Targeted direct reprogramming of adult cardiac fibroblasts to functional cardiomyocytes (2016–2018)
Heart disease is the leading cause of death in all industrialised countries, accounting for 12.7% of total global mortality. Regenerating a damaged heart remains a major challenge. Direct cell reprogramming is a new exciting cell-free therapeutic strategy for in vivo heart tissue repair. In vitro and in vivo conversion of mouse cardiac fibroblasts to cardiomyocytes has been demonstrated, and direct in vitro reprogramming of human cardiac fibroblasts has been reported. However, the reprogramming efficiency was very low, employed clinically untranslatable, untargeted delivery methods that resulted in off-target in vivo reprogramming of cell types outside the heart, and fostered the generation of predominantly immature, partially reprogrammed, non-beating cardiomyocytes. Clinical and commercial translation of this technology requires the development of non-viral, off-the-shelf, scalable, inexpensive technology that ensures specific reprogramming of only cardiac fibroblasts (CFs), and proof of principle that these targeted delivery approaches can control the stoichiometric uptake and expression of factors in vivo to enable efficient reprogramming. We have developed a novel nanoparticle gene delivery system that enables cell-specific delivery to CFs only and validated that these can be incorporated into injectable hydrogels that integrate into the matrix of tissues, permitting localised sustained delivery. We have further identified a new set of factors that reprogram human CFs more efficiently than current methods. In this project, we will identify the optimal delivery method for the reprogramming nanoparticles (systemic or via hydrogel delivery painted on or injected into the heart) and the best promoters for ensuring cell specificity. We will then optimise promoters and factor stoichiometry for murine and human CF reprogramming in a multifactorial microbioreactor array before testing this novel reprogramming system in a mouse heart attack model.