Development of Neuro-Coupled Human Embryonic Stem Cell-Derived Cardiac Pacemaker Cells.

Cardiovascular diseases remain the major cause of death in the US. Human Stem and progenitor cell-derived cardiomyocytes (SPC-CMs) hold great promise for myocardial repairs. Recent progress in cellular reprogramming of various somatic cell types into induced pluripotent stem cells opened the door for developing patient-specific, cell-based therapies. However, most SPC-CMs displayed heterogeneous and immature electrophysiological (EP) phenotypes with uncontrollable automaticity. Implanting these electrically immature and inhomogeneous CMs to the hearts would likely be arrhythmogenic and deleterious. Furthermore, as CMs mature, they undergo changes in automaticity and electrical properties. We used human embryonic stem cell-derived CMs (hESC-CMs) as the model system to study the development and maturation of CMs in the embryoid body (EB) environment. Elucidating molecular pathways governing EP maturation of early hESC-CMs in EBs would enable engineered microenvironment to create functional pacemaker cells or electrophysiologically compatible hESC-CMs for cell replacement therapies. We have established antibiotic (Abx)-resistant hESC lines conferred by lentiviral vectors under the control of a cardiac-specific promoter. With simple Abx treatment, we easily isolated >95% pure hESC-CMs at various stages of differentiation from EBs. In the first year of this grant support and using the Abx selection system, we found that hESC-CMs isolated at early stages of differentiation without further contacts with non-cardiomyocytes (non-CMs) depicted arrested electrical maturation. The intracellular Ca2+-mediated automaticity developed very early and contributed to dominant automaticity throughout hESC-CM differentiation regardless of the presence or absence of non-CMs. In contrast, sarcolemmal ion channels evolved later upon further differentiation within EBs and their maturation required the interaction with non-CMs. In the second year, we further developed an add-back co-culture system to enable adding non-CMs back to early isolated hESC-CMs, which rescued the arrest of EP maturation. We also developed techniques to isolate pure subsets of non-CMs, such as neural crest and endothelial cells, from hESC-derived EBs, which exerted influences on maturation of specific subsets of ion channel populations respectively. Therefore, our study showed for the first time that non-CMs exert significant influences on the EP maturation of hESC-CMs during differentiation. Knowledge of this study will allow us to improve functional maturation of primitive hESC-CMs or to create neuro-coupled pacemaker cells before cell transplantation.

Reporting Period:

NCE

Cardiovascular diseases remain the major cause of death in the US. Human Stem and progenitor cell-derived cardiomyocytes (SPC-CMs) hold great promise for myocardial repairs. Recent progress in cellular reprogramming of various somatic cell types into induced pluripotent stem cells opened the door for developing patient-specific, cell-based therapies. However, most SPC-CMs displayed heterogeneous and immature electrophysiological (EP) phenotypes with uncontrollable automaticity. Implanting these electrically immature and inhomogeneous CMs to the hearts would likely be arrhythmogenic and deleterious. Furthermore, as CMs mature, they undergo changes in automaticity and electrical properties. We used human embryonic stem cell-derived CMs (hESC-CMs) as the model system to study the development and EP maturation of CMs in the embryoid body (EB) environment. Elucidating molecular pathways governing EP maturation of early hESC-CMs in EBs would enable engineered microenvironment to create functional pacemaker cells or electrophysiologically compatible hESC-CMs for cell replacement therapies. We have established antibiotic (Abx)-resistant hESC lines conferred by lentiviral vectors under the control of a cardiac-specific promoter. With simple Abx treatment, we easily isolated >95% pure hESC-CMs at various stages of differentiation from EBs. In the first year of this grant support and using the Abx selection system, we found that hESC-CMs isolated at early stages of differentiation without further contacts with non-cardiomyocytes (non-CMs) depicted arrested electrical maturation. The intracellular Ca2+-mediated automaticity developed very early and contributed to dominant automaticity throughout hESC-CM differentiation regardless of the presence or absence of non-CMs. In contrast, sarcolemmal ion channels evolved later upon further differentiation within EBs and their maturation required the interaction with non-CMs. In the second year, we further developed an add-back co-culture system to enable adding non-CMs back to early isolated hESC-CMs, which rescued the arrest of EP maturation. In the third no-cost extension year, we further successfully established the cocultures of human neural crest cell (NCC)-derivatives and early-purified hESC-CMs. We found that peripheral neurons derived from human NCCs exerted strong influences on the development of a specific subset of ion channel populations during early hESC-CM differentiation. Therefore, our study showed for the first time that non-CMs, especially neurons derived from NCCs, exert significant influences on the EP maturation of hESC-CMs during differentiation. Knowledge of this study will allow us to improve functional maturation of primitive hESC-CMs or to create neuro-coupled pacemaker cells before cell transplantation.

Grant Application Details

Application Title:

Development of Neuro-Coupled Human Embryonic Stem Cell-Derived Cardiac Pacemaker Cells.

Public Abstract:

Optimal cardiac function depends on the properly coordinated cardiac conduction system (CCS). The CCS is a group of specialized cells responsible for generating cardiac rhythm and conducting these signals efficiently to working myocardium. This specialized CCS includes the sinoatrial node, atrioventricular node and His-Purkinje system. These specialized pacemaking /conducting cells have different properties from the surrounding myocytes responsible for the contractile force. Genetic defects or postnatal damage by diseases or aging processes of these cells would result in impaired pulse generation (sinus node dysfunction, SND) or propagation (heart block). Implantation of an electronic cardiac pacemaker is necessary for intolerant bradycardia to restore cardiac rhythm. However, the electronic implantable pacemaker has multiple associated risks (e.g. infections) and requires frequent generator changes due to limited battery life. Sinus node dysfunction is a generalized abnormality of cardiac impulse formation and accounts for >30 percent of permanent pacemaker placements in the US. A perfect therapy to SND will be to repair or replace the defective sinus node by cellular or genetic approaches. Many recent studies have demonstrated, in a proof-of-concept style, of generating a biological pacemaker by implanting various types of progenitor or stem cells into ventricular myocardium to form a pulse-generating focus. However, a perfect biological pacemaker will require good connections with the intrinsic neuronal network for proper physiological responses. Elucidation of the factors controlling the evolution of pacemaker cells and their interaction with the peripheral neuronal precursor cells (neural crest cells, NCCs) will be paramount for creating an adaptive biological pacemaker. The NCCs have been shown to be contiguous with the developing conduction system in embryonic hearts of humans. However, the influence and interaction of the NCCs with the developing cardiac pacemaker cells remains unclear. In addition, there is no simple marker for identifying the pacemaker cells and the electrophysiological (EP) recording is the only physiological method to trace the evolution of cardiac pacemaker cells from human embryonic stem cells (hESCs). We have successfully obtained the EP properties of early hESC-derived cardiomyocytes. We propose here an in vitro co-culture system to study fate of the pacemaker cells evolved from hESCs and to investigate the influence of NCCs on the early, cardiac committed myocytes derived from hESCs. Such a study will provide insight in the development of pacemaker cells and in the mechanisms of early neuro-cardiac interaction. Results from the proposed study may suggest strategies for developing efficient and neuro-coupled cardiac pacemakers from ESCs. These neuro-coupled biological pacemaker cells may one day used clinically to replace the need for implanting an electronic pacemaker for the treatment of intolerant bradycardia.

Statement of Benefit to California:

Optimal cardiac function depends on the properly coordinated cardiac conduction system. Genetic defects or postnatal damage by diseases or aging processes of these pacemaker cells would result in impaired pulse generation (sinus node dysfunction) or propagation (heart block). The implantation of an electronic cardiac pacemaker is necessary for intolerant bradycardia to restore physiologic cardiac rhythm. However, the electronic implantable pacemaker has multiple associated risks (e.g. infections and thrombosis) and requires frequent generator changes due to limited battery life. Sinus node dysfunction (SND) is a generalized abnormality of cardiac impulse formation and accounts for 30-50 percent of permanent pacemaker placements in the US. A perfect therapy to SND will be to repair or replace the defective sinus node by cellular or genetic approaches. Most of the research work on developing biological pacemakers are performed in Columbia University at New York City, Johns Hopkins University at Baltimore, and Technion-Israel Institute of Technology at Haifa, Israel. All of their approaches produced short-lived and non-responsive biological pacemakers to physiological demands. None of human stem cell-related research in California is devoted to this highly promising field of developing biological pacemakers. The proposed research here will elucidate the factors controlling the evolution of pacemaker cells and their interaction with the peripheral neuronal precursor cells (neural crest cells). Such a study will provide insight in the development of pacemaker cells and in the mechanisms of early neuro-cardiac interaction. These factors then can be used to generate better neuro-coupled biological pacemaker cells in California. These neuro-coupled biological pacemaker cells may one day be used clinically to replace the need for implanting an electronic pacemaker for the treatment of intolerant bradycardia. Creating the neuro-coupled, adaptive biological pacemakers will make California the epicenter of the next generation of pacemaker therapy, and will benefit its citizens who have intolerant cardiac bradycardia.

Publications

Circulation (2009): Electrophysiological challenges of cell-based myocardial repair. (PubMed: 20008740)
J Cardiovasc Electrophysiol (2011): Electrophysiological Mapping of Embryonic Mouse Hearts: Mechanisms for Developmental Pacemaker Switch and Internodal Conduction Pathway. (PubMed: 21985309)
PLoS One (2009): Lentiviral vectors and protocols for creation of stable hESC lines for fluorescent tracking and drug resistance selection of cardiomyocytes. (PubMed: 19352491)
Circulation (2013): Missense Mutations in Plakophilin-2 Cause Sodium Current Deficit and Associate with a Brugada Syndrome Phenotype. (PubMed: 24352520)
Stem Cells Dev (2010): Non-cardiomyocytes influence the electrophysiological maturation of human embryonic stem cell-derived cardiomyocytes during differentiation. (PubMed: 20001453)
Nature (2013): Studying arrhythmogenic right ventricular dysplasia with patient-specific iPSCs. (PubMed: 23354045)