title: Rapid fusion between mesenchymal stem cells and cardiomyocytes yields electrically active, non-contractile hybrid cells.
abstract: Cardiac cell therapies involving bone marrow-derived human mesenchymal stem cells (hMSCs) have shown promising results, although their mechanisms of action are still poorly understood. Here, we investigated direct interactions between hMSCs and cardiomyocytes in vitro. Using a genetic Ca(2+) indicator gCaMP3 to efficiently label hMSCs in co-cultures with neonatal rat ventricular myocytes (NRVMs), we determined that 25-40% of hMSCs (from 4 independent donors) acquired periodic Ca(2+) transients and cardiac markers through spontaneous fusion with NRVMs. Sharp electrode and voltage-clamp recordings in fused cells showed action potential properties and Ca(2+) current amplitudes in between those of non-fused hMSCs and NRVMs. Time-lapse video-microscopy revealed the first direct evidence of active fusion between hMSCs and NRVMs within several hours of co-culture. Application of blebbistatin, nifedipine or verapamil caused complete and reversible inhibition of fusion, suggesting potential roles for actomyosin bridging and Ca(2+) channels in the fusion process. Immunostaining for Cx43, Ki67, and sarcomeric α-actinin showed that fused cells remain strongly coupled to surrounding NRVMs, but downregulate sarcomeric structures over time, acquiring a non-proliferative and non-contractile phenotype. Overall, these results describe the phenotype and mechanisms of hybrid cell formation via fusion of hMSCs and cardiomyocytes with potential implications for cardiac cell therapy.
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, NC.
authors.forename: Ilya Y
authors.initials: IY
authors.lastname: Shadrin
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, NC.
authors.forename: Woohyun
authors.initials: W
authors.lastname: Yoon
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, NC.
authors.forename: Liqing
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, NC.
authors.forename: Neal
authors.initials: N
authors.lastname: Shepherd
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, NC.
authors.forename: Nenad
authors.initials: N
authors.lastname: Bursac
mesh_terms: D000185:Actinin / Q000235:genetics / Q000378:metabolism; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002459:Cell Fusion; D002465:Cell Movement; D002478:Cells, Cultured; D018920:Coculture Techniques; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007477:Ions / Q000737:chemistry / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D018715:Microscopy, Video; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000378:metabolism; D024462:Myosin Type II / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D059008:Time-Lapse Imaging; D020107:Troponin T / Q000235:genetics / Q000378:metabolism
chemical_list: D020746:Calcium Channels, L-Type; D018031:Connexin 43; D007477:Ions; D020107:Troponin T; D000185:Actinin; D002110:Caffeine; D024462:Myosin Type II; D002118:Calcium