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Heart, Lung and Circulation

Don’t Turn Off the Tap! The Importance of Discovery Science to the Australian Cardiovascular Sector and Improving Clinical Outcomes Into the Future

Published:August 10, 2022DOI:https://doi.org/10.1016/j.hlc.2022.06.669
      Despite significant advances in interventional and therapeutic approaches, cardiovascular disease (CVD) remains the leading cause of death and mortality. To lower this health burden, cardiovascular discovery scientists need to play an integral part in the solution. Successful clinical translation is achieved when built upon a strong foundational understanding of the disease mechanisms involved. Changes in the Australian funding landscape, to place greater emphasis on translation, however, have increased job insecurity for discovery science researchers and especially early-mid career researchers. To highlight the importance of discovery science in cardiovascular research, this review compiles six science stories in which fundamental discoveries, often involving Australian researchers, has led to or is advancing to clinical translation. These stories demonstrate the importance of the role of discovery scientists and the need for their work to be prioritised now and in the future. Australia needs to keep discovery scientists supported and fully engaged within the broader cardiovascular research ecosystem so they can help realise the next game-changing therapy or diagnostic approach that diminishes the burden of CVD on society.

      Keywords

      Introduction

      When John F Kennedy (JFK) first conceived the idea to send humans to the moon (and back), questions were asked about its value and usefulness to humankind. Even the previous administration led by Eisenhower, who first established the National Aeronautics and Space Administration (NASA), regarded JFK as ‘nuts’ for considering an all-out effort to reach the moon. The Apollo program was the single largest project for its time—over a decade of work costing US$25.6 billion (US$156 billion when adjusted for inflation). Questions dogged the program through disasters like the 1967 fire that killed the Apollo 1 crew, right up to the ultimately successful moon landing in 1969: “Wouldn’t this money have been better spent on the millions of people facing poverty and starvation?” Although potentially difficult to see at the time, the benefits of this visionary project are impossible to overstate—and we are still seeing them today.
      Apollo spurred significant advances across a host of different scientific fields including avionics, telecommunications and computing. Even the live broadcast of the moon landing was a technological marvel of the time. The rise of Silicon Valley is a direct result of the Apollo program, followed by Apple, Microsoft and others. Furthermore, that human endeavour in science inspired millions worldwide to study science, technology, engineering and mathematics (STEM) fields, indirectly led to more advances. And it was driven by fundamental scientists and engineers working on a project that many at the time thought superfluous and indulgent.
      Few people now look back at Apollo and question its value to the society that paid for it. It is through this lens that we must judge the value of investing in discovery science, appreciating the time and investment required to make translatable, transformative impact. There is no more salient illustration of this today than the COVID-19 pandemic. Had we not invested in the scientists who first made fundamental discoveries underlying mRNA vaccine technology and fast-paced DNA-based vaccine production years before the pandemic, the stunning speed at which multiple, highly effective COVID-19 vaccines were generated would not have been possible today. If ever there was a time to appreciate the importance of fundamental discovery research, it is now.
      And yet, the future of discovery science is at risk with limited funding options and decreasing job security. As a result, our most inquisitive minds, from university graduates to scientists with 20-year careers, are moving to careers outside of science [
      Professional Scientists Australia
      Professional Scientists Employment and Renumeration Report 2021-22.
      ]. The cardiovascular research sector in Australia is no exception to this. Despite cardiovascular disease (CVD) being the biggest killer in Australia and costing the economy AUD$15 billion per annum [
      Australian Institute of Health and Welfare. Disease Expenditure in Australia. 2019b; Cat no. HWE 76. Canberra: AIHW.
      ], the culmination of repeated short-term contracts, job uncertainty and low funding success rates has led to over 90% of cardiovascular researchers saying they are considering leaving the field in the next few years [
      • Climie R.E.
      • Wu J.H.Y.
      • Calkin A.C.
      • Chapman N.
      • Inglis S.C.
      • Mirabito Colafella K.M.
      • et al.
      Lack of strategic funding and long-term job security threaten to have profound effects on cardiovascular researcher retention in Australia.
      ].
      Spectacular developments in our understanding of CVD over the last 60 years have seen dramatic declines in mortality. However, a plateau has been reached and ‘solving’ the next frontier of CVD (e.g. coronary artery disease in patients without conventional risk factors, treatment-resistant hypertension, and haemorrhagic stroke, among others) will require a whole-of-pipeline approach that places importance on basic and discovery science.
      Simply put, clinical translation is limited by the fundamental understanding on which it is built. Here, we highlight six examples of this pipeline in action, where fundamental discoveries have developed into therapies that substantially impact CVD treatment and management, some involving Australian scientists. These are only a handful of the stories we could have told and we acknowledge the many researchers whose discoveries are not able to be covered here. We offer these as potent examples of why basic scientific research should be supported at the earliest stages of the research pipeline, and as a call-for-action for the government of Australia to renew support for this now endangered research sector.

      From a Filamentous Fungus to Our Leading Therapy for CVD

      “To avoid cardiovascular disease, lower your cholesterol levels”. Most people are familiar with this statement; for years we have known about the contribution of elevated total cholesterol and low-density lipoprotein cholesterol (LDL-c) levels to CVD. Indeed, therapies that lower blood lipid levels are now the mainline treatment option for doctors. However, the story of how we got to today’s therapies starts over 300 years ago (Figure 1), when scientist Francois Poulletier de le Salle found solid cholesterol in gallstones [
      • Endo A.
      A historical perspective on the discovery of statins.
      ]. It took another hundred years, in 1833, before Felix-Henri Boudet discovered cholesterol in human blood [
      • Endo A.
      A historical perspective on the discovery of statins.
      ], and then 23 years until Rudolf Virchow described ‘atherosclerotic deposits’ [
      • Virchow R.
      Cellular pathology. As based upon physiological and pathological histology. Lecture XVI--Atheromatous affection of arteries. 1858.
      ]. It was then another century until the Framingham Heart Study in 1957, the first large population-based heart health study, linked higher cholesterol levels with human coronary artery disease (CAD) [
      • Dawber T.R.
      • Moore F.E.
      • Mann G.V.
      Coronary heart disease in the Framingham study.
      ]. It was glacial progress, and little could be done with this knowledge. It would be basic molecular research that allowed the next step forward.
      Figure thumbnail gr1
      Figure 1Timeline of discovery for determining the role of cholesterol in atherosclerosis, the cholesterol biosynthesis pathway and the cholesterol lowering, athero-protective properties of statins. Filled panels indicate discovery science. Open panels indicate clinical discoveries. A split panel indicates work that included both discovery and translation science. The ‘set of scales’ represent clinical trials, magnifying glass indicates a breakthrough discovery, tick indicates FDA approval and a medal/ribbon indicates a Nobel Prize was awarded for the discovery. Created with BioRender.com.
      Abbreviation: FDA, US Food & Drug Administration.
      In the 1970s, scientists began characterising the cholesterol biosynthetic pathway, which was the first step towards making a tangible impact against cholesterol-induced CVD. Pioneering enzymologic studies by Konrad Bloch revealed that 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMGCoA) reductase was the rate-limiting step in cholesterol biosynthesis, and earned him a Nobel Prize [
      • Goldfine H.
      • Vance D.E.
      Obituary: Konrad E. Bloch (1912-2000).
      ]. US scientists Goldstein and Brown had a keen knowledge of this pathway and through elegant, well-controlled studies, identified that a novel receptor—the LDL receptor—caused feedback inhibition of HMGCoA reductase. This discovery would also earn Goldstein and Brown a Nobel Prize [
      • Motulsky A.G.
      The 1985 Nobel Prize in physiology or medicine.
      ]. Around the same time, Akira Endo isolated a molecule called ‘compactin’ from the filamentous fungus penicillium citrinum and found it could inhibit cholesterol biosynthesis [
      • Endo A.
      • Kuroda M.
      • Tanzawa K.
      Competitive inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase by ML-236A and ML-236B fungal metabolites, having hypocholesterolemic activity.
      ]. Goldstein and Brown reached out to Endo, asking if they could test compactin in fibroblasts from patients with familial hypercholesterolaemia (FH), and found that compactin inhibited HMGCoA reductase [
      • Brown M.S.
      • Faust J.R.
      • Goldstein J.L.
      • Kaneko I.
      • Endo A.
      Induction of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in human fibroblasts incubated with compactin (ML-236B), a competitive inhibitor of the reductase.
      ]. Suddenly, by combining basic research of a biological mechanism with the biochemistry of fungi, a potential treatment was identified.
      However, the pathway from these laboratory findings to today’s statin lipid-lowering therapies was complex, and almost completely derailed. During preclinical trials, dogs treated with very large doses of compactin developed gastrointestinal lesions. The scientists running the trials interpreted these as malignant lymphomas [
      • Endo A.
      A historical perspective on the discovery of statins.
      ]. This diagnosis sent drug companies into retreat—the Akira-founded Sankyo stopped statin development, as did pharmaceutical giant Merck who were working on their own ‘lovastatin’. Fears were amplified as cholesterol had been established as a key component of cell membranes—could these drugs affect the structure of cells themselves? It was not until several years later, following a change in leadership at Merck, that statins were re-evaluated [
      • Endo A.
      A historical perspective on the discovery of statins.
      ]. Extensive toxicity testing proved the ‘lymphomas’ in dogs were not lymphomas at all, but a result of histological changes caused by cellular processing of the massive amounts of compactin that was given. Other safety testing showed that cellular cholesterol was not of concern. This triggered US Food & Drug Administration (FDA) approval for clinical trials, which showed lovastatin was safe in humans. The Scandinavian Simvastatin Survival Study trial followed, showing statins were highly effective at lowering LDL-c and cardiovascular event recurrence [
      Randomised trial of cholesterol lowering in 4444 patients with coronary heart disease: the Scandinavian Simvastatin Survival Study (4S).
      ]. Global efforts testing the many statins now in the marketplace in placebo-controlled clinical trials, have resoundingly testified to the general safety and efficacy of statins in reducing CVD risk. A notable Australian contribution was from Stephen Nicholls, who, during his time at the Cleveland Clinic with Steven Nissen, led large clinical trials that have shown high-dose statins are well tolerated, regress atherosclerosis and reduce CVD events [
      • Nicholls S.J.
      • Ballantyne C.M.
      • Barter P.J.
      • Chapman M.J.
      • Erbel R.M.
      • Libby P.
      • et al.
      Effect of two intensive statin regimens on progression of coronary disease.
      ].
      Ultimately, statins have revolutionised CVD treatment, saving millions of people from the debilitating effects of atherosclerosis. But this long and complicated story was only made possible by the repeated efforts of discovery scientists, whose work fed and informed clinical research at every step.

      Interfering With Lipid Shuttling to Increase the Good Cholesterol

      The development of statins is not the whole cholesterol story. Cholesterol is not a stagnant form—esterified cholesterol molecules shift between different lipoprotein fractions, such as low-density lipoprotein (LDL) to the high-density lipoprotein (HDL) form and vice versa. In the 1970s, Australian Philip Barter, working as an independent researcher at the time at Flinders University in Adelaide, argued that there must be a ‘factor’ that causes this shift (Figure 2). It ended up taking a decade, but he eventually overturned contemporary opinion and showed there was a “lipid transfer protein” (LTP) in human serum that promoted the exchange of cholesterol esters between lipoproteins. When he added mixtures of lipoproteins to otherwise-lipoprotein-free human serum, there was a shift of esterified cholesterol from HDL to very-low density lipoprotein (VLDL). This exchange did not occur with lipoprotein-free serum from rats [
      • Barter P.J.
      • Lally J.I.
      The activity of an esterified cholesterol transferring factor in human and rat serum.
      ]—clearly there was something unique about human serum. Barter later used semi-purified fractions of LTP (soon known as cholesterol ester transfer protein, CETP) from human plasma for systematic testing of lipid transfer activity to show it was the enzyme responsible [
      • Barter P.J.
      • Hopkins G.J.
      • Calvert G.D.
      Transfers and exchanges of esterified cholesterol between plasma lipoproteins.
      ].
      Figure thumbnail gr2
      Figure 2Timeline for the discovery of CETP and its translation to cardiovascular clinical trials. Filled panels indicate discovery science. Open panels indicate clinical discoveries. The ‘set of scales’ represent clinical trials, magnifying glass indicates a breakthrough discovery and the kangaroo symbols indicate an Australian discovery. Created with BioRender.com.
      Abbreviations: CETP, cholesteryl ester transfer protein; HDLc, high density lipoprotein cholesterol; LDLc, low density lipoprotein cholesterol; LoF, loss of function; LTP, lipid transfer protein.
      Geneticists in the 1980s then discovered mutations in the CETP gene. Some patients in Japan had CETP mutations that caused a loss of function, resulting in significantly elevated HDL-c and reduced LDL-c levels [
      • Koizumi J.
      • Mabuchi H.
      • Yoshimura A.
      • Michishita I.
      • Takeda M.
      • Itoh H.
      • et al.
      Deficiency of serum cholesteryl-ester transfer activity in patients with familial hyperalphalipoproteinaemia.
      ,
      • Yamashita S.
      • Matsuzawa Y.
      • Okazaki M.
      • Kako H.
      • Yasugi T.
      • Akioka H.
      • et al.
      Small polydisperse low density lipoproteins in familial hyperalphalipoproteinemia with complete deficiency of cholesteryl ester transfer activity.
      ]. This came amidst emerging epidemiological evidence, including from the Framingham Heart Study, that as HDL-c levels decreased, the risk of myocardial infarction (MI) increased [
      • Dawber T.R.
      • Moore F.E.
      • Mann G.V.
      Coronary heart disease in the Framingham study.
      ]. These results prompted scientists to suggest that if low HDL-c increased the risk of cardiac problems, then increasing HDL-c could be protective. Inhibition of CETP was an obvious strategy, especially in conjunction with lipid-lowering statin therapy.
      Adelaide-based Mavis Abbey led the charge, showing that inhibition of CETP in rabbits decreased VLDL and LDL cholesterol and reduced atherosclerosis [
      • Abbey M.
      • Calvert G.D.
      Effects of blocking plasma lipid transfer protein activity in the rabbit.
      ]. The subsequent search for potential CETP inhibitors soon identified ‘torcetrapib’, which had the most favourable effects on elevating HDL-c and inhibiting CETP, especially in people with low HDL-c levels [
      • Brousseau M.E.
      • Schaefer E.J.
      • Wolfe M.L.
      • Bloedon L.T.
      • Digenio A.G.
      • Clark R.W.
      • et al.
      Effects of an inhibitor of cholesteryl ester transfer protein on HDL cholesterol.
      ]. Large-scale clinical trials of CETP inhibition understandably followed. But this unexpectedly led to a more challenging time for CETP inhibition and the HDL hypothesis.
      The first Phase 3 CETP inhibitor trial was led by Barter, the scientist who originally discovered CETP [
      • Barter P.J.
      • Caulfield M.
      • Eriksson M.
      • Grundy S.M.
      • Kastelein J.J.
      • Komajda M.
      • et al.
      Effects of torcetrapib in patients at high risk for coronary events.
      ]. Torcetrapib initially appeared to perform beautifully—increasing HDL-c levels by 70%. However, it also increased the participants’ mortality (likely from off-target effects, including increased blood pressure). The study was halted early. The second CETP inhibitor trial tested a different drug, dalcetrapib [
      • Schwartz G.G.
      • Olsson A.G.
      • Abt M.
      • Ballantyne C.M.
      • Barter P.J.
      • Brumm J.
      • et al.
      Effects of dalcetrapib in patients with a recent acute coronary syndrome.
      ]. Dalcetrapib caused a more modest elevation in HDL-c and exhibited no off-target effects. However, it didn’t provide any cardiovascular benefit. The study was also halted early. The third CETP trial, led by Nicholls (who had been a PhD student of Barter's), used evacetrapib [
      • Nicholls S.J.
      • Brewer H.B.
      • Kastelein J.J.
      • Krueger K.A.
      • Wang M.D.
      • Shao M.
      • et al.
      Effects of the CETP inhibitor evacetrapib administered as monotherapy or in combination with statins on HDL and LDL cholesterol: a randomized controlled trial.
      ]. It ended the same way and increased the growing concern about the benefit of CETP inhibition.
      A fourth and final trial used the inhibitor anacetrapib [
      • Group H.T.R.C.
      • Bowman L.
      • Hopewell J.C.
      • Chen F.
      • Wallendszus K.
      • Stevens W.
      • et al.
      Effects of anacetrapib in patients with atherosclerotic vascular disease.
      ]. Given to over 30,000 participants with atherosclerotic CVD and on statin therapy, anacetrapib reduced major coronary events. Admittedly it wasn’t the largest reduction—only 9%, but still a highly significant result. Whether this trial was successful due to its size or duration, or whether it was driven by HDL-c raising (104%) or LDL-c and non-HDL-c lowering (-17% and -18%, respectively), is still a subject of debate. Regardless, the aptly-named REVEAL
      Randomized EValuation of the Effects of Anacetrapib Through Lipid-modification.
      trial demonstrated that CETP inhibition reduces cardiovascular events, making it one of few non-statin strategies that holds claim to reducing CVD. The tumultuous track that CETP inhibition has taken has ultimately meant that CETP inhibitors are unlikely to be integrated into routine clinical use and regulatory approval is not being sought.
      Nonetheless, the decade-long testing of CETP inhibition in large clinical trials sparked a new appreciation for the role of HDL functionality, with it now being regarded as a better marker of cardiovascular benefit than HDL-c concentration. This put the biology of HDL firmly on the map for CVD, revealing its complexity in ways that have never been previously considered or thought to be important. And while it was clinical studies that brought a treatment to market, it was laboratory-based discovery science, starting with Barter in the 1970s in the labs of Adelaide, that made it possible, at multiple stages.

      Understanding Protein Origami for the Prevention of Cardiomyopathy

      Biomedical science sees its greatest advances when new technology allows us to ask fundamental questions at a deeper level. This is perhaps best exemplified by the development of X-ray crystallography by Australian-born Sir William Lawrence Bragg and his father William Henry Bragg [
      • Thomas J.M.
      Centenary: The birth of X-ray crystallography.
      ]. It enabled some of the most iconic breakthroughs in modern biomedical research, including elucidation of the structure of DNA [
      • Watson J.D.
      • Crick F.H.
      Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid.
      ] and then the first structures of proteins [
      • Perutz M.F.
      • Rossmann M.G.
      • Cullis A.F.
      • Muirhead H.
      • Will G.
      • North A.C.
      Structure of haemoglobin: a three-dimensional Fourier synthesis at 5.5-A. resolution, obtained by X-ray analysis.
      ,
      • Kendrew J.C.
      • Dickerson R.E.
      • Strandberg B.E.
      • Hart R.G.
      • Davies D.R.
      • Phillips D.C.
      • et al.
      Structure of myoglobin: a three-dimensional Fourier synthesis at 2 A. resolution.
      ].
      Understanding how the “beads-on-a-string” structure of a newly synthesised protein chain becomes folded in a complicated three-dimensional structure has been fundamental to our understanding of the molecular basis of disease. In the 1970s the prevailing view of protein structure and function was that the sequence of a protein determines its native conformation which, in turn, determines its biological activity [
      • Anfinsen C.B.
      The formation and stabilization of protein structure.
      ]. However, it is now widely recognised that many proteins can adopt either a “native active conformation” or can misfold into an inactive amyloid fibrillar structure. Using the analogy of the art of origami, one piece of paper can be folded into multiple structures.
      The term amyloid was coined by Virchow in 1854 to refer to macroscopic tissue deposits that stained positively with iodine (Figure 3) [
      Virchow's Archiv. 1854-1859.
      ]. For the next 125 years, amyloid remained of interest to a few curious biochemists and a few haematologists who looked after patients with rare systemic amyloidosis and suffered from amyloid deposits. We now recognise that these amyloid deposits are formed by misfolded immunoglobulin light chains or transthyretin.
      Figure thumbnail gr3
      Figure 3Timeline of the discovery of amyloid and its role in degenerative disease, including identification of the role of TTR protein mis-folding in amyloidosis through to the clinical translation of a TTR stabiliser that prevents heart failure. Filled panels indicate discovery science. Open panels indicate clinical discoveries. A split panel indicates work that included both discovery and translation science. The ‘set of scales’ represent clinical trials, magnifying glass indicates a breakthrough discovery, tick indicates FDA approval and a medal/ribbon indicates a Nobel Prize was awarded for the discovery. The kangaroo symbols indicate an Australian discovery. Created with BioRender.com.
      Abbreviations: FDA, US Food & Drug Administration; TTR, transthyretin; ATTR, amyloid transthyretin; ATTR-ACT, Tafamidis in Transthyretin Cardiomyopathy Clinical Trial.
      The discovery that the insoluble extracellular deposits in Alzheimer’s disease were made of amyloid fibrils led to an explosion of interest in understanding how and why certain proteins end up in these insoluble amyloid forms, including, in 1985, the purification and characterisation of the amyloid protein in Alzheimer disease, undertaken by Colin Masters in his laboratory in Western Australian [
      • Masters C.L.
      • Simms G.
      • Weinman N.A.
      • Multhaup G.
      • McDonald B.L.
      • Beyreuther K.
      Amyloid plaque core protein in Alzheimer disease and Down syndrome.
      ]. With Alzheimer’s and its related dementias one of the major causes of death and disability in our community, there is now great interest in understanding the molecular basis of protein misfolding and the development of drugs that can interfere with the initiation and/or growth of amyloid deposits.
      However, under the shadow of Alzheimer’s disease, it is often overlooked that amyloid deposits can also result in a range of other degenerative diseases, including in the cardiovascular system. One protein in particular that misfolds and accumulates in the myocardium is transthyretin, or transthyretin (TTR). This accumulation affects the myocardium and conduction system, causing cardiomyopathy, heart failure and pacing issues such as atrial fibrillation [
      • Connors L.H.
      • Sam F.
      • Skinner M.
      • Salinaro F.
      • Sun F.
      • Ruberg F.L.
      • et al.
      Heart failure resulting from age-related cardiac amyloid disease associated with wild-type transthyretin: a prospective, observational cohort study.
      ].
      In its native form, TTR circulates in the blood transporting holoretinol binding protein [
      • Johnson S.M.
      • Connelly S.
      • Fearns C.
      • Powers E.T.
      • Kelly J.W.
      The transthyretin amyloidoses: from delineating the molecular mechanism of aggregation linked to pathology to a regulatory-agency-approved drug.
      ]. The importance of TTR in amyloid formation was first uncovered in biochemical studies led by Jeffery Kelly, working at the Texas A&M University in the US in the early 1990s. His team discovered that TTR, upon even partial denaturation, readily misassembles and forms amyloid fibrils [
      • Colon W.
      • Kelly J.W.
      Partial denaturation of transthyretin is sufficient for amyloid fibril formation in vitro.
      ]. A follow-up study soon identified mutations that further destabilised TTR and increased amyloidogenicity [
      • McCutchen S.L.
      • Colon W.
      • Kelly J.W.
      Transthyretin mutation Leu-55-Pro significantly alters tetramer stability and increases amyloidogenicity.
      ].
      Over the ensuing decade, Kelly’s team focussed on developing strategies to prevent TTR from unfolding. Initial success came when they showed in vitro that thyroxin and a non-native ligand could prevent unfolding of TTR, reducing conformation changes and amyloid fibril formation [
      • Miroy G.J.
      • Lai Z.
      • Lashuel H.A.
      • Peterson S.A.
      • Strang C.
      • Kelly J.W.
      Inhibiting transthyretin amyloid fibril formation via protein stabilization.
      ]. However, it was soon realised that the most effective way to prevent initial TTR unfolding was to use stabilisers that increased the kinetic barrier (energy required) to unfold, thereby keeping TTR in its native tetrameric state [
      • Hammarstrom P.
      • Wiseman R.L.
      • Powers E.T.
      • Kelly J.W.
      Prevention of transthyretin amyloid disease by changing protein misfolding energetics.
      ].
      Over 1,000 aromatic small molecules were tested to find the best stabiliser in preventing TTR amyloid fibrillogenesis [
      • Johnson S.M.
      • Connelly S.
      • Fearns C.
      • Powers E.T.
      • Kelly J.W.
      The transthyretin amyloidoses: from delineating the molecular mechanism of aggregation linked to pathology to a regulatory-agency-approved drug.
      ]. A drug licensed in 2010, tafamidis, became the lead candidate after it was found to bind highly selectively to TTR in human plasma, stabilising TTR and preventing TTR fibril formation even in denaturing conditions [
      • Razavi H.
      • Palaninathan S.K.
      • Powers E.T.
      • Wiseman R.L.
      • Purkey H.E.
      • Mohamedmohaideen N.N.
      • et al.
      Benzoxazoles as transthyretin amyloid fibril inhibitors: synthesis, evaluation, and mechanism of action.
      ].
      Initial pilot and dosage studies of tafamidis were for the prevention of polyneuropathy by TTR amyloid. These found outstanding benefits, in which tafamidis reduced neurological deterioration with no adverse events [
      • Coelho T.
      • Maia L.F.
      • Martins da Silva A.
      • Waddington Cruz M.
      • Plante-Bordeneuve V.
      • Lozeron P.
      • et al.
      Tafamidis for transthyretin familial amyloid polyneuropathy: a randomized, controlled trial.
      ]. Post hoc analyses of these neuropathy trials also identified benefits for preventing amyloid cardiomyopathy [
      • Maurer M.S.
      • Grogan D.R.
      • Judge D.P.
      • Mundayat R.
      • Packman J.
      • Lombardo I.
      • et al.
      Tafamidis in transthyretin amyloid cardiomyopathy: effects on transthyretin stabilization and clinical outcomes.
      ]. A proportion of the patients in the trials had heart failure (shown by high levels of NT-proBNP, a marker for heart failure) and conduction abnormalities, but after 12 months on tafamidis, these patients had no further deterioration in cardiac condition and were, in fact, stabilised [
      • Maurer M.S.
      • Grogan D.R.
      • Judge D.P.
      • Mundayat R.
      • Packman J.
      • Lombardo I.
      • et al.
      Tafamidis in transthyretin amyloid cardiomyopathy: effects on transthyretin stabilization and clinical outcomes.
      ].
      With this promising result, a cardiomyopathy-specific trial of tafamidis was conducted. In this 30-month trial, tafamidis treatment caused a significant reduction in all-cause mortality and cardiovascular-related hospitalisations, and slowed the decline in quality of life. Overall, survival was 17.5 months longer for those on tafamidis [
      • Maurer M.S.
      • Schwartz J.H.
      • Gundapaneni B.
      • Elliott P.M.
      • Merlini G.
      • Waddington-Cruz M.
      • et al.
      Tafamidis treatment for patients with transthyretin amyloid cardiomyopathy.
      ]. These outstanding outcomes gained tafamidis regulatory approval for use in patients with TTR cardiomyopathy in 2019 [
      • Maurer M.S.
      • Bokhari S.
      • Damy T.
      • Dorbala S.
      • Drachman B.M.
      • Fontana M.
      • et al.
      Expert consensus recommendations for the suspicion and diagnosis of transthyretin cardiac amyloidosis.
      ].
      From decades of work by pioneers in understanding protein structure and function, the pathogenicity of protein origami led directly to the development of a lifesaving medical cure for a once fatal disease.

      When ‘NO’ Was the Correct Answer All Along

      The endothelium—the innermost lining of arteries and veins and composed of endothelial cells—was once considered nothing more than just a simple barrier between the blood and the vessel wall. Then, in 1980, scientists Furchgott and Zawakzki accidentally [
      • Furchgott R.F.
      Endothelium-derived relaxing factor: discovery, early studies, and identifcation as nitric oxide (Nobel Lecture).
      ] found the vasodilating effects of acetylcholine (ACh) on excised arteries would only occur when the endothelium was left intact [
      • Furchgott R.F.
      • Zawadzki J.V.
      The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine.
      ]. They postulated that ACh stimulated the release of a ‘substance’ from endothelial cells, which caused vascular smooth muscle relaxation. This ‘substance’ was subsequently named endothelium-derived relaxing factor (EDRF) [
      • Cherry P.D.
      • Furchgott R.F.
      • Zawadzki J.V.
      • Jothianandan D.
      Role of endothelial cells in relaxation of isolated arteries by bradykinin.
      ].
      It would take 7 years before researchers worked out what EDRF was. The discovery that nitric oxide (NO) was the mysterious vasodilation mediator is one of the most far-reaching discoveries in the past four decades. First discovered, isolated and coined ‘nitrous air—a different type of air for respiration’ by Joseph Priestly in 1786 [
      • Smith W.D.
      A history of nitrous oxide and oxygen anaesthesia. I. Joseph Priestley to Humphry Davy.
      ] (Figure 4), this colourless, volatile, potentially toxic gas rapidly became the golden child for cardiovascular function and beyond.
      Figure thumbnail gr4
      Figure 4Timeline for the discovery of nitric oxide, its vasodilatory effects on the vasculature through to the clinical translation of sildenafil. Filled panels indicate discovery science. Open panels indicate clinical discoveries. The ‘set of scales’ represent clinical trials, magnifying glass indicates a breakthrough discovery, tick indicates FDA approval and a medal/ribbon indicates a Nobel Prize was awarded for the discovery. Created with BioRender.com.
      Abbreviations: FDA, US Food & Drug Administration; EDRF, endothelium-derived relaxing factor; PDE5, phosphodiesterase type 5; cGMP, cyclic-guanosine monophosphate.
      Of course, reaching this discovery was not a straight line, or the work of a few.
      ACh-induced EDRF release was found to accompany an increase of cyclic-guanosine monophosphate (cGMP) [
      • Furchgott R.F.
      Endothelium-derived relaxing factor: discovery, early studies, and identifcation as nitric oxide (Nobel Lecture).
      ], similar to the increase in cGMP observed by Murad [
      • Katsuki S.
      • Arnold W.
      • Mittal C.
      • Murad F.
      Stimulation of guanylate cyclase by sodium nitroprusside, nitroglycerin and nitric oxide in various tissue preparations and comparison to the effects of sodium azide and hydroxylamine.
      ] and Ignarro [
      • Gruetter C.A.
      • Barry B.K.
      • McNamara D.B.
      • Gruetter D.Y.
      • Kadowitz P.J.
      • Ignarro L.
      Relaxation of bovine coronary artery and activation of coronary arterial guanylate cyclase by nitric oxide, nitroprusside and a carcinogenic nitrosoamine.
      ] with NO-mediated vasodilation [
      • Gruetter C.A.
      • Barry B.K.
      • McNamara D.B.
      • Gruetter D.Y.
      • Kadowitz P.J.
      • Ignarro L.
      Relaxation of bovine coronary artery and activation of coronary arterial guanylate cyclase by nitric oxide, nitroprusside and a carcinogenic nitrosoamine.
      ]. This was an important observation as cGMP is a major mechanism through which the effects of NO are mediated. Then, haemoglobin and methylene blue were found to be potent inhibitors of EDRF-mediated vasodilation and inhibitors of NO-mediated vasodilation [
      • Furchgott R.F.
      Endothelium-derived relaxing factor: discovery, early studies, and identifcation as nitric oxide (Nobel Lecture).
      ]. As technology progressed, the NO story advanced towards its inevitable conclusion, with new perfusion-bioassays finding more similarities between NO and EDRF. Then, in 1986, both Furchgott and Ignarro proposed at a symposium that EDRF was in fact NO all along. This was finally confirmed in publications by Ignarro et al. [
      • Ignarro L.J.
      • Buga G.M.
      • Wood K.S.
      • Byrns R.E.
      • Chaudhuri G.
      Endothelium-derived relaxing factor produced and released from artery and vein is nitric oxide.
      ], Palmer et al. [
      • Palmer R.M.
      • Ferrige A.G.
      • Moncada S.
      Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor.
      ], and Khan and Furchgott [
      • Nava E.
      • Llorens S.
      The paracrine control of vascular motion. A historical perspective.
      ] the following year.
      Fast forward 35 years and we now know that NO’s physiological functions extend far beyond mediating vascular relaxation. NO inhibits platelet aggregation and pathogen replication as part of the body’s immune response. It is implicated in a range of cardiovascular and non-cardiovascular related disease states, such as hypertension, septic shock, and dementia. Reduced bioavailability of NO (or endothelial dysfunction, as it is commonly called) is associated with many, if not all, cardiovascular risk factors, including atherosclerosis, coronary artery disease (CAD), hypertension, hypercholesterolaemia, and diabetes [
      • Yetik-Anacak G.
      • Catravas J.D.
      Nitric oxide and the endothelium: history and impact on cardiovascular disease.
      ]. And, we use NO levels to predict disease using widely-available invasive and non-invasive assessments of vascular endothelial function [
      • Flammer A.J.
      • Anderson T.
      • Celermajer D.S.
      • Creager M.A.
      • Deanfield J.
      • Ganz P.
      • et al.
      The assessment of endothelial function: from research into clinical practice.
      ].
      But possibly the most famous outcome from identifying NO as EDRF is the development of sildenafil, better known as Viagra, which inhibits phosphodiesterase type 5 (PDE5), an enzyme that limits the relaxation effect of NO on smooth muscle cells. From a simple discovery of the factor responsible for endothelial relaxation came arguably the best-known drug on the market. Indeed, its initial development focussed on cardiovascular effects, before the direction rapidly changed when new results emerged. Sildenafil citrate (Revatio, Pfizer, New York, NY, USA) also demonstrated excellent efficacy for the treatment of pulmonary hypertension through its anti-proliferative effects on vascular smooth muscle cells in which it now has FDA approval for this indication [
      • Galie N.
      • Ghofrani H.A.
      • Torbicki A.
      • Barst R.J.
      • Rubin L.J.
      • Badesch D.
      • et al.
      Sildenafil citrate therapy for pulmonary arterial hypertension.
      ].
      From the first discovery of NO in 1772 to the identification of NO as EDRF in 1987, being named the “Molecule of the Year” by Science in 1992 and having a scientific journal as its namesake (Nitric Oxide: Biology and Chemistry) in 1997, the far-reaching impact of the discovery of NO as EDRF is no doubt impressive. For this revolutionary change in knowledge and understanding, Furchgott, Ignarro, and Murad received the Nobel Prize for Medicine or Physiology in 1998.
      Up until the experiments that proved EDRF was in fact NO, the answer to the question “Do you think you know what EDRF is yet?” had always been “No”. Whoever would have thought that it was accidentally the correct answer all along?

      Repairing Hearts With Deadly Spider Venom

      While a filamentous fungus was the unexpected genesis of statins, spider venom has also proved an unlikely source of inspiration for discovery scientists studying heart cell death following myocardial infarction (MI). The venom of a number of species (e.g. snakes, spiders, scorpions and shellfish) has been studied by scientists for well over a century (Figure 5). As far back as 1904, for example, it was identified that snake venom caused neurotoxic effects [
      • Lamb G.
      • Hunter W.
      On the action of venoms of different species of poisonous snakes on the nervous system.
      ]. In the 1970s components from the venom of the snake Bothros jararaca were found to inhibit angiotensin converting enzyme (ACE) [
      • Ondetti M.A.
      • Williams N.J.
      • Sabo E.F.
      • Pluscec J.
      • Weaver E.R.
      • Kocy O.
      Angiotensin-converting enzyme inhibitors from the venom of Bothrops jararaca. Isolation, elucidation of structure, and synthesis.
      ]. This formed the first steps to the development of captopril, a now widely used anti-hypertensive drug that improves the survival of patients post-MI [
      • Pfeffer M.A.
      • Braunwald E.
      • Moye L.A.
      • Basta L.
      • Brown Jr., E.J.
      • Cuddy T.E.
      • et al.
      Effect of captopril on mortality and morbidity in patients with left ventricular dysfunction after myocardial infarction. Results of the survival and ventricular enlargement trial. The SAVE Investigators.
      ].
      Figure thumbnail gr5
      Figure 5Timeline for the discovery of the biological effects of venom, the identification of ASICs and an inhibitor from spider venom that preserves hearts post-MI. Filled panels indicate discovery science. Open panels indicate clinical discoveries. A split panel indicates work that included both discovery and translation science. The magnifying glass indicates a breakthrough discovery and the kangaroo symbols indicate an Australian discovery. Created with BioRender.com.
      Abbreviations: ASICS, acid-sensing ion channels; MI, myocardial infarction; ACE, angiotensin converting enzyme; BP, blood pressure; PcTX1, psalmotoxin.
      During an MI, the ensuing myocardial ischaemia causes a change in cardiomyocyte metabolism, switching to anaerobic glycolysis that lowers intracellular pH, making it more acidic. This myocardial acidosis is well-known to be associated with significant patient mortality. However, while injury response mechanisms are extensively studied, no drugs that prevent cells from dying during an MI have translated into clinical practice. This is despite ischaemic injuries to the heart being the most significant underlying cause of heart failure, costing health systems around the world about USD$108 billion annually [
      • Cook C.
      • Cole G.
      • Asaria P.
      • Jabbour R.
      • Francis D.P.
      The annual global economic burden of heart failure.
      ].
      Acidosis causes changes in the function of diverse ion channels in cardiomyocytes. For example, the sodium hydrogen exchanger (NHE) is well-known to underpin pathological changes in ion balance in cardiomyocytes during cardiac ischaemia. Inhibitors of the NHE channel using cariporide reached Phase 3 clinical trials before being discontinued due to cerebrovascular complications [
      • Kimura K.
      • Nakao K.
      • Shibata Y.
      • Sone T.
      • Takayama T.
      • Fukuzawa S.
      • et al.
      Randomized controlled trial of TY-51924, a novel hydrophilic NHE inhibitor, in acute myocardial infarction.
      ]. More recently, a new type of ion channel has been discovered that mediates cell death in response to ischaemia, the acid-sensing ion channels (ASICs). These channels appear to be key players in mediating acid-induced cell death signals in cells [
      • Waldmann R.
      • Champigny G.
      • Voilley N.
      • Lauritzen I.
      • Lazdunski M.
      The mammalian degenerin MDEG, an amiloride-sensitive cation channel activated by mutations causing neurodegeneration in Caenorhabditis elegans.
      ].
      The opportunity to modulate ASIC activity came from a source few expected. In 2000, a French team led by Michel Lazdunski identified a component of tarantula spider venom that selectively bound the ASIC1a channel isoform with high potency [
      • Escoubas P.
      • De Weille J.R.
      • Lecoq A.
      • Diochot S.
      • Waldmann R.
      • Champigny G.
      • et al.
      Isolation of a tarantula toxin specific for a class of proton-gated Na+ channels.
      ]. Not recognising the potential as a therapeutic for brain and cardiac injuries, this toxin, psalmotoxin 1 (PcTx1), was thought of solely as a tool to understand ion channel functions.
      It was not until 4 years later that inhibition of ASICs was suggested as a mechanism to prevent cell death. A paper published in Cell in 2004 by Roger Simon and colleagues in the US [
      • Xiong Z.G.
      • Zhu X.M.
      • Chu X.P.
      • Minami M.
      • Hey J.
      • Wei W.L.
      • et al.
      Neuroprotection in ischemia: blocking calcium-permeable acid-sensing ion channels.
      ] showed that ischaemia-induced cellular acidosis activated ASICs and caused neuronal injury. But, when PcTx1 was administered to pharmacologically block ASIC1a, the brain was protected from ischaemic injury. These mice displayed significantly smaller infarct volumes than control mice in a model of transient focal ischaemia in which an occlusion was made around the cerebral artery for 24 hours, mimicking a stroke-like injury. The findings of this study provided the critical rationale for using ASIC inhibitors for neuroprotection following stroke.
      More than 10 years later, a Queensland laboratory led by Glenn King [
      • Chassagnon I.R.
      • McCarthy C.A.
      • Chin Y.K.
      • Pineda S.S.
      • Keramidas A.
      • Mobli M.
      • et al.
      Potent neuroprotection after stroke afforded by a double-knot spider-venom peptide that inhibits acid-sensing ion channel 1a.
      ] made a serendipitous discovery that proved a turning point for ASIC1a inhibitors. A student in his team was sequencing the proteome of the venom of one of the world’s most deadly spiders, the Fraser Island (K’gari) funnel-web spider. This spider venom contained a sequence that matched PcTx1, except that this molecule had two homologous PcTx1-like domains separated by a short linker. This new molecule, Hi1a, showed critical differences in function to PcTx1, particularly that, unlike the original PcTx1, Hi1a incompletely blocked ASIC1a in a slowly reversible manner. Based on promising studies in stroke, King and colleagues tested Hi1a in a focal transient ischaemia stroke model, finding remarkable efficacy at reducing infarct size at very low doses, even when administered up to 8 hours after stroke induction [
      • Chassagnon I.R.
      • McCarthy C.A.
      • Chin Y.K.
      • Pineda S.S.
      • Keramidas A.
      • Mobli M.
      • et al.
      Potent neuroprotection after stroke afforded by a double-knot spider-venom peptide that inhibits acid-sensing ion channel 1a.
      ].
      As King showed the benefits of Hi1a in stroke, Nathan Palpant, having established his lab at University of Queensland, postulated that a similar acidosis stress event might happen post-ischaemia in cardiomyocytes following MI. Therefore, Hi1a may also protect against cardiac damage post-MI and prevent heart failure. His work, using human induced pluripotent stem cell (iPSC)-derived cardiomyocytes, found that inhibition of ASIC1a using either Hi1a or PcTx1 prevented cell death in an in vitro model of cardiac ischaemic reperfusion injury (IRI) [
      • Redd M.A.
      • Scheuer S.E.
      • Saez N.J.
      • Yoshikawa Y.
      • Chiu H.S.
      • Gao L.
      • et al.
      Therapeutic inhibition of acid-sensing ion channel 1a recovers heart function after ischemia-reperfusion injury.
      ]. Follow-up studies using a mouse model of cardiac IRI showed that mice receiving Hi1a had markedly improved cardiac recovery compared to control mice. Furthermore, they were protected against the cardiac dysfunction and fibrosis that can lead to heart failure. A chance conversation between Glenn King and Jamie Vandenberg then led to the establishment of a collaboration with heart transplant trailblazer Peter Macdonald working at the St. Vincent’s Hosptial and Victor Chang Cardiac Research Institute in Sydney, where the Hi1a work was extended into heart transplant experiments, a model system that has a proven pathway to clinical translation [
      • Dhital K.K.
      • Iyer A.
      • Connellan M.
      • Chew H.C.
      • Gao L.
      • Doyle A.
      • et al.
      Adult heart transplantation with distant procurement and ex-vivo preservation of donor hearts after circulatory death: a case series.
      ].
      After just 20 years, from when PcTx1 was first identified in tarantula venom as an agent that blocks ASICs, we are now on the cusp of a new, highly effective therapy that saves hearts and brains from cell death following strokes and heart attacks. These ground-breaking discoveries, led by Australian-based scientists using a protein from the venom of an Australian spider on K’gari/Fraser Island, have generated therapies that are now being developed for clinical testing.

      Stem Cells That Repair the Heart

      Approximately one billion cardiomyocytes are lost during a MI. Unfortunately, the human heart has a poor ability to regenerate these ‘lost’ cells on its own, leading to scarring of the heart tissue, reduced cardiac function, and subsequent heart failure. The potential of stem cell therapy to regenerate tissues and treat disease is therefore enormous. It is not hard, however, to understand the immense challenges that come with the goal of accurately delivering stem cells to the damaged heart, having them differentiate only into relevant cell types which then integrate anatomically and electrically into the damaged tissue in a way that promotes normal function. Australian discovery scientists have led the way and helped navigate the numerous hurdles, both biological and ethical.
      Stem cell biology was first pioneered over 70 years ago and one of the key researchers was Don Metcalf at the Walter and Eliza Hall Institute in Melbourne (Figure 6). Metcalf is renowned for being an especially dedicated scientist and deep thinker, and from the first day he set eyes on agar plates containing small colonies of cells from mouse bone marrow, he became fascinated with what made them grow [
      • Metcalf D.
      Summon up the Blood.
      ]. Most significantly, he and his team resolved waves of confusion over what colony stimulation factor (CSF) was and how it acted [
      • Bradley T.R.
      • Metcalf D.
      • Robinson W.
      Stimulation by leukaemic sera of colony formation in solid agar cultures by proliferation of mouse bone marrow cells.
      ,
      • Robinson W.A.
      • Stanley E.R.
      • Metcalf D.
      Stimulation of bone marrow colony growth in vitro by human urine.
      ,
      • Metcalf D.
      • Moore M.A.
      Factors modifying stem cell proliferation of myelomonocytic leukemic cells in vitro and in vivo.
      ,
      • Metcalf D.
      The colony stimulating factor (CSF).
      ]. Then, after multiple CSFs were identified (eventually known as M-CSF, GM-CSF and G-CSF), they provided many of the seminal studies that ironed out their associated confusions and contradictions [
      • Metcalf D.
      The Wellcome Foundation lecture, 1986. The molecular control of normal and leukaemic granulocytes and macrophages.
      ], providing the knowledge and understanding that allowed stem cell therapies to progress to the clinic around the world.
      Figure thumbnail gr6
      Figure 6Timeline representing the seminal studies characterising colony stimulating factors, the mixed findings from initial stem cell clinical trials to the promise of recent advances. Filled panels indicate discovery science. Open panels indicate clinical discoveries. A split panel indicates work that included both discovery and translation science. The ‘set of scales’ represent clinical trials, magnifying glass indicates a breakthrough discovery and a medal/ribbon indicates a Nobel Prize was awarded for the discovery. The kangaroo symbols indicate an Australian discovery. Created with BioRender.com.
      Abbreviations: ACCRUE, Meta-Analysis of Cell-based CaRdiac stUdiEs; hESCs, human embryonic stem cells; hiPSCs, human induced pluripotent stem cell.
      Indeed, the last 30 years saw the largest steps towards developing stem cell-based cell therapies for heart regeneration. Pioneering work in the ‘90s demonstrated for the first time that cardiomyocytes could graft into hearts and survive [
      • Koh G.Y.
      • Soonpaa M.H.
      • Klug M.G.
      • Field L.J.
      Long-term survival of AT-1 cardiomyocyte grafts in syngeneic myocardium.
      ]. Following this, an apparent breakthrough study in 2001 [
      • Orlic D.
      • Kajstura J.
      • Chimenti S.
      • Jakoniuk I.
      • Anderson S.M.
      • Li B.
      • et al.
      Bone marrow cells regenerate infarcted myocardium.
      ] claimed that bone marrow cells injected to the infarct site post-MI in mice were able to differentiate into endothelial cells, myocytes and smooth muscle cells, and replace a substantial portion of the infarcted heart tissue, leading to heart regeneration. Whilst these findings sparked great enthusiasm in the field, significant flaws and falsifications were subsequently identified in this paper and in other studies by this group. In a high profile hit on discovery science, the retraction of >30 papers followed and understandably had a disheartening impact on the cardiac cell therapeutics field [
      • Chien K.R.
      • Frisen J.
      • Fritsche-Danielson R.
      • Melton D.A.
      • Murry C.E.
      • Weissman I.L.
      Regenerating the field of cardiovascular cell therapy.
      ].
      But a host of clinical trials were already underway that were testing bone marrow and other stem-cell-based therapies in patients after MI. The findings of these trials were highly variable. For example, some studies found significant improvements in left ventricular ejection fraction following infusion of autologous bone marrow cells or bone marrow-derived progenitor cells post-MI [
      • Meyer G.P.
      • Wollert K.C.
      • Lotz J.
      • Steffens J.
      • Lippolt P.
      • Fichtner S.
      • et al.
      Intracoronary bone marrow cell transfer after myocardial infarction: eighteen months' follow-up data from the randomized, controlled BOOST (BOne marrOw transfer to enhance ST-elevation infarct regeneration) trial.
      ,
      • Lunde K.
      • Solheim S.
      • Aakhus S.
      • Arnesen H.
      • Abdelnoor M.
      • Egeland T.
      • et al.
      Intracoronary injection of mononuclear bone marrow cells in acute myocardial infarction.
      ]. Others saw no benefit [
      • Janssens S.
      • Dubois C.
      • Bogaert J.
      • Theunissen K.
      • Deroose C.
      • Desmet W.
      • et al.
      Autologous bone marrow-derived stem-cell transfer in patients with ST-segment elevation myocardial infarction: double-blind, randomised controlled trial.
      ]. In 2015, a meta-analysis of 12 randomised studies found stem cell therapy, overall, showed no benefit on major adverse cardiac events or secondary endpoints, including death or ventricular volume [
      • Gyongyosi M.
      • Wojakowski W.
      • Lemarchand P.
      • Lunde K.
      • Tendera M.
      • Bartunek J.
      • et al.
      Meta-Analysis of Cell-based CaRdiac stUdiEs (ACCRUE) in patients with acute myocardial infarction based on individual patient data.
      ].
      What did become evident following this unfortunate detour in cardiac stem cell science, was that the ability of stem cells to engraft and survive is actually extremely limited. Therefore, it was back to the bench with discovery scientists tasked with deciphering the underlying reason. It is now realised that a deep understanding of the biological mechanisms that control cardiac repair is necessary before moving again into large-scale clinical trials. And although many translational challenges still exist today, significant progress is being made.
      Meanwhile, the idea of cardiomyocyte therapy was gaining traction in laboratories around the world with the realisation that human cardiomyocytes could be produced at scale by directed differentiation of human embryonic stem cells (hESC) based on developmental principals [
      • Kouskoff V.
      • Lacaud G.
      • Schwantz S.
      • Fehling H.J.
      • Keller G.
      Sequential development of hematopoietic and cardiac mesoderm during embryonic stem cell differentiation.
      ]. One study that gained significant attention and provided a major step forward towards clinical translation of cardiomyocyte therapy was performed by Australian James Chong during his time as a Fellow at the University of Washington in Seattle USA under the mentorship of Charles Murry [
      • Chong J.J.
      • Yang X.
      • Don C.W.
      • Minami E.
      • Liu Y.W.
      • Weyers J.J.
      • et al.
      Human embryonic-stem-cell-derived cardiomyocytes regenerate non-human primate hearts.
      ]. They demonstrated the potential of human embryonic stem cell-derived cardiomyocytes (hESC-CMs) to repair infarcted hearts of non-human primates. One billion hESC-CMs were generated in vitro, then injected into the myocardium following ischaemia/reperfusion, resulting in remuscularisation of the infarct region, revascularisation by host cells and electrical integration.
      Of the stem cell candidates, induced pluripotent stem cells (iPSCs) are increasingly recognised for their potential. Chong, now back in Australia running his own lab at the Westmead Millennium Institute for Medical Research, is now embarking on pushing forward the translation of iPSC-CM therapies in patients with no-option end-stage heart failure. Other Australians, including John Rasko from the Centenary Institute at the University of Sydney, have also advanced testing of iPSC-derived mesenchymal stem cells to early-stage clinical pilot studies, demonstrating safety in graft-versus-host disease [
      • Bloor A.J.C.
      • Patel A.
      • Griffin J.E.
      • Gilleece M.H.
      • Radia R.
      • Yeung D.T.
      • et al.
      Production, safety and efficacy of iPSC-derived mesenchymal stromal cells in acute steroid-resistant graft versus host disease: a phase I, multicenter, open-label, dose-escalation study.
      ]. Furthermore, Queensland-based James Hudson has pioneered a novel technique that utilises human iPSCs to produce multi-cellular cardiac microtissues that mimic tissue composition in the human heart [
      • Mills R.J.
      • Humphrey S.J.
      • Fortuna P.R.J.
      • Lor M.
      • Foster S.R.
      • Quaife-Ryan G.A.
      • et al.
      BET inhibition blocks inflammation-induced cardiac dysfunction and SARS-CoV-2 infection.
      ]. These enable the rapid screening of treatments or different stimulations, such as cytokine combinations seen in COVID-19, and present a powerful system for overcoming translation gaps in the process of drug discovery.

      Conclusions

      The role of a discovery scientist is absolutely central to developing new treatments and interventions, which makes it infinitely exciting. It is also often impossible to predict where a particular mechanistic discovery might have a translational impact, such as the observation of protein fibrils, or the investigation of spider venoms. While some may view aspects of discovery science as esoteric, the examples provided in this review directly demonstrate that such knowledge often makes a tangible impact on the society in which we live, improving quality of life and providing economic benefit. This review emphasises the need to support Australia’s current and future discovery scientists in the cardiovascular field to uncover game-changing discoveries. We need them to unlock the full potential of stem cells, of spider venom, or cholesterol control, that will protect or repair our hearts in the future. However, our discovery science workforce is largely an under-supported, stressed, and perilously-employed group of individuals that feel the need to prepare for ‘jumping ship’ to alternate professions. This is not a strong foundation for science-led discovery.
      Advocates for basic science need to step up and remind all funders: governments (National Health and Medical Research Council, Medical Research Future Fund, Australian Research Council and State-based research funds), philanthropy, industry and the wider community of the fundamental and significant role that the basic sciences play in providing deep solutions to our most significant areas of disease burden. We also need to ensure that we have a funding framework that encourages budding young scientists to tackle the hardest problems. This means funding longer-term contracts that provide stability and enable researchers to develop a broader vision and to effectively manage risk, an inherent component of the discovery process. Another important mechanism that supports Australian researchers is the funding of overseas fellowships that enable Australians to acquire training in top international laboratories. This investment should be continued and expanded. Time and time again Australians have punched well above their weight during overseas postdoctoral placements, which then facilitates their transition to successful independent researchers back in Australia, supporting the Australian research ecosystem. It must be acknowledged that many of our very best Australian researchers also remain overseas in well-resourced laboratories, establishing their own labs and having an immense influence in the US, Europe and other countries. To encourage the return of the majority of these highly-skilled people, Australia needs to provide funding opportunites well-past the PhD and early-career fellowship stage and out to >15 years postdoctoral. These opportunities are currently exceedingly scarce and prohibitively competitive. This type of funding support also has the benefit of enabling young scientists to see that there is a possibility of a long-term career in research in Australia, preventing their loss to other professions.
      There are, however, exciting opportunites ahead for the basic scientists in the medical research sector. The Federal Government’s recent announcement of the AUD$2.2 billion Research Commercialisation Fund is a welcome initiative that fosters whole-of-pipeline thinking and collaboration by the entire research ecosystem. Basic scientists who choose to engage with these efforts will have the opportunity to tackle the largest unmet needs in health by driving discovery and innovation aimed at boosting health outcomes as well as commercialisation. In turn, this will help drive funding sustainability for the whole sector and ensure that cardiovascular research can capitalise on the opportunity before us. With the very recent change in the federal government of Australia, the Australian research community is hoping that a Minister for Science and Technology will be appointed. It is critical we have a champion at the federal level who can drive long-term strategies regarding education, research, translation, innovation and research infrastructure.
      Overall, the immense value of discovery science needs to be realised. It takes time but it is worth it.

      Conflicts of Interest

      The authors declare no competing interests.

      Acknowledgements

      We thank the Australian Cardiovascular Alliance (ACvA) Board for their support and endorsement of this initiative. We would like to thank and acknowledge the supporting roles of ACvA Project Officers, Meng-Ping Hsu and Catherine Shang, in the facilitation of this initiative. We acknowledge that some authors are members of the ACvA Board.

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