Understanding Cardiac Progenitors to deliver Regenerative Medicine and Disease Modelling

Heart disease, including damage to heart muscle, kills more people worldwide than any other illness. This means strategies for cardiac regeneration, such as cell replacement therapy after myocardial infarction and 'disease in a dish' modelling in vitro, are urgently needed. Access to cardiovascular cells including cardiomyocytes from human pluripotent stem cells (hPSCs) offers therapeutic potential capable of revolutionising cardiology but, as yet, the promise is unmet. Progress is currently hindered by our poor understanding of, and thus ability to control, cardiac cell development - principally the events of cardiac progenitor cell (CPC) specification, self-renewal and differentiation. The lack of comparative molecular benchmarking with human embryogenesis, required to authenticate cells in vitro, is another major barrier. By consequence, at present, mixtures of poorly specified cardiomyocyte identities emerge from uncontrolled, heterogeneous differentiation. The resultant cells are inadequate for accurate disease modelling (disease phenotypes are highly variable) and would be potentially life-threatening (arrhythmogenic) if transplanted.

There are three major components to my study, delivery of which will unlock potential for academic research, clinical and industrial applications: 1) discovering the identity of CPCs and how to control them, 2) authenticating ventricular cardiomyocyte differentiation and 3) testing the system in an in vivo context.

The challenge to unravelling the complexities of cardiac cell development is that differentiation is heterogeneous, CPCs are diverse, and cells progress along the differentiation trajectory at different rates. To overcome this, I have created an in vitro model system of single cell genomics linked to clonal lineage tracing and fate assessment. This integrated and unbiased approach will enable me to identify the gene expression and chromatin signatures pertinent to CPC self-renewal and cardiomyocyte differentiation potential. Perturbation experiments in vitro, combined with comparative measurements of the native cells in human embryogenesis, will help me identify the most functionally influential and authentic candidates. Together, these experiments will deliver the knowledge and tools to isolate, expand and differentiate the most desirable CPC identities - those with potential to be accurately programmed to specific target cell types e.g. ventricular cardiomyocytes (a key target for disease modelling and cell therapy).
To learn how to accurately control downstream differentiation of CPCs to ventricular cardiomyocytes, I will use the gene expression and chromatin structure of human ventricular myocardium through development to benchmark differentiation in vitro. The relationship between signalling pathways and the regulation and expression of key transcription factors will be systematically resolved, to achieve the accurate, lineage-specific differentiation of CPCs. Finally, to validate these advances in CPC maintenance, tracking and differentiation to translational relevance, I will work in partnership with international collaborators to assess cell behaviour following transplantation into an animal model.
In summary, by delivering research innovation of immediate clinical and industrial importance, this project is closely in tune with the UK Government's Industrial Strategy. The predicted advances will benefit applications in regenerative medicine, cardiac disease modelling, biomarker identification and drug screening. Moreover, it will also allow me to establish myself as a global leader in the field and, by partnering with industry, a persistent force towards achieving these translational goals.

The socioeconomic cost of cardiovascular disease (CVD) to the UK is immense, with around 7 million people living with CVD (bhf.org.uk/statistics) and an estimated cost to the UK economy of £19 billion each year. While survival rates from cardiovascular events have been improving, therapeutic options are very limited for many patients e.g. with heart failure or debilitating genetic disease. By advancing stem cell technology, this research will support industry to help patients, thus promoting the health and wealth of the nation.

Who will benefit from this research?

> Drug development industry - any path to decreasing the attrition rate of drugs during the development process will decrease costs and improve the flow of drugs to patients. Stem cell technology is anticipated to have a major impact on this field in the coming years by providing access to accurate patient-specific models of disease (using iPSCs and gene editing), drug-safety pharmacology screens and disease biomarkers. This will help to de-risk drug development but also help to make it more personalised - a concept known as precision medicine. This research, helping to better understand cardiac differentiation, how to control cardiac progenitor cells (CPCs) and direct their differentiation in line with human development, will provide immediate opportunity for making authentic human cell models of the heart. These innovations will provide immediate benefit to the new 'Medicines Discovery Catapult' (MDC), an Innovate UK funded organisation aimed at supporting UK businesses develop drugs by developing patient relevant cell models and validating biomarkers. It will create the tools and the knowledge the MDC needs to deliver these goals. As such, further along, this will benefit the pharmaceutical industry who are poised to reap the rewards of stem cell technology, but have been held back up to now by the inaccuracy of the available models; to ensure that potential gains safely outweigh the risks, they need these to be well-validated and of high-confidence.

> Regenerative medicine industry - the UK cell therapy industry is a rapidly growing commercial sector that in recent years has benefited from increased investment, including through the Innovate UK 'Cell and Gene Therapy Catapult', now also building a large-scale GMP-compliant manufacturing centre in the UK to support production needs. The industry needs to scale up the manufacture of existing therapies for clinical trials; but to continue growth, needs also to have new innovative therapies entering the development pipeline. By developing CPC technology, including novel approaches to isolate and maintain these cells, and validating their behaviour in vivo, this research will provide important groundwork towards a regenerative therapy for heart disease.

> The public - for those affected by heart attack and heart failure, advances in regenerative medicine will bring hope where there was none. By unlocking its potential, this innovative research will help transform the clinical applications of stem cell technology. It also promises to help those suffering from heart disease from genetic causes by facilitating the development of precision medicine and treatments tailored to particular genetic defects. The benefits of both may start to be realised in the next 10 years. Improvements in the drug development pipeline in industry e.g. with new human disease models and improved safety pharmacology, should also improve future drug flow to the market (beyond 10 years).

> Charities - many charities focused on combating CVD will benefit including the British Heart Foundation (BHF), the biggest independent funder of CVD research in the UK. This research will help by delivering innovative technology but also by creating a network of skilled scientists motivated to fight for this cause on into the future.