Selection, maturation induction and enrichment of pacemaker cells from stem cells for generating biological pacemakers in clinical therapy

Funding Type: 
Early Translational I
Grant Number: 
TR1-01231
Investigator: 
ICOC Funds Committed: 
$0
Public Abstract: 
Optimal cardiac function depends on the properly coordinated cardiac conduction system, which includes sinoatrial node (SAN), atrioventricular node and His-Purkinje system. Genetic defects or postnatal damage of SAN cells result in impaired pulse generation (sinus node dysfunction, SND), accounting for >30% of permanent pacemaker placements in the US. However, electronic pacemakers have limited battery life and multiple associated risks. The ideal therapy for SND is to repair or replace the defective SAN by cellular or genetic approaches. Stem and progenitor cell-derived cardiomyocytes (SPC-CMs) hold great promise for generating biological pacemakers. However, three main bottlenecks need to be resolved before we could translate primitive SPC-CMs into a feasible biological pacemaker. First, we need to create methods to isolate SAN progenitor cells from primitive SPC-CMs to facilitate the development of pure pacemaker cells (PMCs) from SPCs. Second, most SPC-CMs display heterogeneous and immature electrophysiological (EP) phenotypes with variable automaticity. The molecular pathways of inducing EP maturation of primitive PMCs are largely unknown. Implanting these electrically immature and inhomogeneous CMs into hearts may carry arrhythmogenic risks. Third, methods to enrich and induce maturation of PMCs are needed for any feasible clinical application. Further development in selection, inducing maturation and enrichment of pacemaker cells from primitive SPC-CMs are needed in order to overcome bottlenecks of translating SPC-CMs into feasible biological pacemaker cells. Studying SAN development is a challenging task due to lack of specific SAN tracking markers or methods. Additionally, most mutant mice with defective SAN function are embryonic-lethal and cannot be studied further. We used human embryonic stem cell-derived cardiomyocytes (hESC-CMs) to investigate factors affecting the development of automaticity in embryoid bodies (EBs). We find that automaticity of primitive hESC-CMs evolves in the EB milieu from a simple intracellular Ca2+ based mechanism to a mature form of automaticity, involving sarcolemmal ion channels. We have developed an EP screen with a specific agent that can sub-select early PMCs from primitive SPC-CMs, as a result, facilitating the generation of pure PMCs. We also successfully generated induced pluripotent stem (iPS) cell-derived cardiomyocytes (iPS-CMs). Furthermore, in order to elucidate the molecular pathways of PMC development, we apply gene chip technologies and collaborate with other scientists to establish the developmental gene profiles of PMCs obtained from human adult hearts, fetal hearts, hESC-CMs and iPS-CMs. We will use automated microscopy with cell tracking technologies to screen small molecules to enrich early PMCs and to induce their maturation. The overall goal of this proposal is to purify, differentiate, and enrich pacemaker cells for cell-based therapy of intolerable slow heart rate from SND.
Statement of Benefit to California: 
Cardiovascular diseases remain the major cause of death in the western world. Stem and progenitor cell (SPC)-based cell therapies in animal and human studies suggest promising therapeutic potentials. However, most SPC-derived cardiomyocytes (SPC-CMs) display heterogeneous and immature electrophysiological (EP) phenotypes with substantial automaticity. Implanting these electrically immature and inhomogeneous CMs to hearts may carry arrhythmogenic and deleterious risks. Furthermore, genetic defects or postnatal damage of sinoatrial node (SAN) cells result in impaired pulse generation (sinus node dysfunction, SND), accounting for >30% of pacemaker placements in the US. However, electronic pacemakers have multiple associated risks. The ideal therapy for SND is to repair or replace the defective SAN by cellular or genetic approaches. SPC-CMs hold great promise for generating biological pacemakers. Several bottlenecks need to be resolved before we can translate SPC-CMs into a feasible biological pacemaker. We have successfully used human embryonic stem cell-derived cardiomyocytes (hESC-CMs) to investigate factors affecting the development of automaticity of early PMCs. We have developed an EP screen with a specific agent that can sub-select early pacemaker cells (PMCs) from primitive SPC-CMs, as a result, facilitating the generation of pure PMCs. With collaborations, we also successfully generated induced pluripotent stem (iPS) cell-derived cardiomyocytes (iPS-CMs). These two breakthroughs lead us a step closer toward generating patient-specific biological pacemaker cells for future clinical therapy. We further used gene chip technology to map the genetic makeup of PMCs in adult & fetal hearts, hESC-CMs and iPS-CMs in order to create a road map for inducing maturation of primitive PMCs. Finally, we will apply automated microscopy with cell tracking technologies to screen small molecules for enriching early PMCs for the gene chip analysis and for inducing the maturation of early PMCs. With aforementioned goals achieved, we will make California the first state to develop a patient-specific biological pacemaker with a mature and homogeneous population of PMCs. No otherstem cell-related research in California is devoted to optimize the selection, scale-up and induction of maturation of PMCs for achieving a safe cell-based therapy. The proposed research will be the first to achieve this goal indicated by CIRM translational I research awards. The success of this proposal will also make California the epicenter of the next generation of cell therapies and will benefit its citizens who have significant SND.

© 2013 California Institute for Regenerative Medicine