This progress report covers FY3 of the project to identify and characterize novel small molecule probes of cardiomyocyte differentiation from stem cells. During FY3, we characterized 11 novel chemical entities that promote cardiomyocyte differentiation. The small, drug-like molecules affect distinct steps in cardiomyocyte differentiation – 5 compounds promote formation of uncommitted cardiac progenitors, 2 stimulated committed cardiac precursors, while 2 compounds act later to stimulate differentiation into cardiomyocytes. Thus, these compounds are novel probes of stem cell differentiation. Some of the compounds are characterized to act upon particular cellular target proteins while the targets of other compounds are unknown. Of the latter class, candidate targets have been characterized by biochemical studies; one of which has been confirmed by RNA interference, yielding a new pathway in cardiac cell formation from stem cells. Three of the chemical series have been described in a patent application. Additional primary hits are being characterized.
For FY4, we will continue characterization of a novel compounds. Particular focus will be on 4 chemical entities that promote later stages of human stem cell cardiomyocyte differentiation and on characterizing and discovering additional candidates that act on late-stage differentiation. In addition, we will develop a new pathway screen for a cellular target involved in specifying cardiomyocyte progenitors that have recently been shown to form new myocytes in vivo. Our new compounds are valuable probes of the underlying mechanism(s) responsible for making cardiac cells from stem cells. Moreover, recent data has shown that endogenous stem cells that reside in the adult heart resemble progenitors in the hESC cultures, so certain of our compounds can be considered as targeting cellular proteins and signaling pathways that might be beneficial to stimulate endogenous regeneration. Towards this goal, we will optimize the drug-like properties of the compounds in anticipation of in vivo testing for regenerative potential.