Force Measurements of Human Embryonic Stem Cell‐Derived Cardiomyocytes in an In Vitro Transplantation Model

Human embryonic stem cell (hESC)‐derived cardiomyocytes have been suggested for cardiac cell replacement therapy. However, there are no data on loaded contractions developed by these cells and the regulation thereof. We developed a novel in vitro transplantation model in which beating cardiomyocytes derived from hESCs (line H1) were isolated and transplanted onto noncontractile, ischemically damaged ventricular slices of murine hearts. After 2–3 days, transplanted cells started to integrate mechanically into the existing matrix, resulting in spontaneous movements of the whole preparation. Preparations showed a length‐dependent increase of active tension. In transplanted early beating hESC‐derived cardiomyocytes, frequency modulation by field stimulation was limited to a small range around their spontaneous beating rate. Our data demonstrate that this novel in vitro transplantation model is well suited to assess the mechanical properties and functional integration of cells suggested for cardiac replacement strategies.