Transplantation of cryopreserved cardiomyocytes

Background: The present study examined the survival and rate of contraction of (1) cardiomyocytes cultured from cryopreserved fetal rat myocardium and (2) cryopreserved cultured cardiomyocytes. In addition, the effects of tra nsplantation of cryopreserved fetal cardiomyocytes were evaluated. Methods: Segments of fetal rat myocardial tissue (0.2, 2.0, and 6.0 mm(3) m ince size) and cultured cardiomyocytes were cryopreserved in liquid nitroge n for 1, 2, and 3 weeks. After cryopreservation, the tissue samples and cul tured cardiomyocytes were thawed at 37 degreesC and cultured, and cell prol iferation and rate of contraction were determined. Cultured cryopreserved ( n = 5) and noncryopreserved (control, n = 5) fetal cardiomyocytes were tran splanted into the subcutaneous tissue and into a transmural left ventricula r free wall scar of Sprague-Dawley rats (n = 3). The survival and rate of c ontraction of these transplanted cells were also examined. Results: Cryopreservation of cultured fetal cardiomyocytes resulted in viab le and functional cardiomyocytes although the cell number and percentage of beating cells were diminished. Survival of cardiomyocytes isolated from cr yopreserved fetal myocardium was a function of tissue size before cryoprese rvation; the lowest survival was recorded in tissues with the largest mince size (6.0 mm(3)). The subcutaneous transplants contracted spontaneously an d regularly with an idioventricular rhythm. In addition, the transplanted c ardiomyocytes were elongated and formed a myocardium-like pattern with bloo d vessels present within the contractile tissue. In the transmural left ven tricular scar, both control and experimental fetal cardiomyocyte transplant s formed myocardium-like tissue. Conclusions: The present study uncovers the following key observations: (1) cryopreservation of fetal cardiomyocytes and cardiomyocytes isolated from cryopreserved myocardial tissue results in viable and functional cells, (2) cryopreserved fetal cardiomyocytes can be successfully transplanted into s ubcutaneous and myocardial scar tissue, and (3) improvements in cryopreserv ation techniques are required to augment the rates of cardiomyocyte surviva l observed in the study.