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J Thorac Cardiovasc Surg 2001;121:0098-0107
© 2001 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease |
From the Division of Cardiovascular Surgery, Department of Laboratory Medicine and Pathobiology, Toronto General Hospital, University of Toronto, Toronto, Ontario, Canada.
R.K.L. is a Research Scholar of the Heart and Stroke Foundation of Canada. S.V. is a Fellow of the Medical Research Council of Canada. This research was supported by a grant from the Medical Research Council of Canada (grant No. MT-13665) to R.K.L.
Received for publication May 4, 2000. Revisions requested June 12, 2000; revisions received July 26, 2000. Accepted for publication Sept 3, 2000. Address for reprints: Ren-Ke Li, MD, PhD, Toronto General Hospital, CCRW 1-815, 200 Elizabeth St, Toronto, Ontario, Canada, M5G 2C4 (E-mail: RenKe.Li{at}uhn.on.ca).
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 transplantation of cryopreserved fetal cardiomyocytes were evaluated.
Methods: Segments of fetal rat myocardial tissue (0.2, 2.0, and 6.0 mm3 mince size) and cultured cardiomyocytes were cryopreserved in liquid nitrogen for 1, 2, and 4 weeks. After cryopreservation, the tissue samples and cultured cardiomyocytes were thawed at 37°C and cultured, and cell proliferation and rate of contraction were determined. Cultured cryopreserved (n = 5) and noncryopreserved (control, n = 5) fetal cardiomyocytes were transplanted into the subcutaneous tissue and into a transmural left ventricular free wall scar of Sprague-Dawley rats (n = 3). The survival and rate of contraction of these transplanted cells were also examined.
Results: Cryopreservation of cultured fetal cardiomyocytes resulted in viable and functional cardiomyocytes although the cell number and percentage of beating cells were diminished. Survival of cardiomyocytes isolated from cryopreserved fetal myocardium was a function of tissue size before cryopreservation; the lowest survival was recorded in tissues with the largest mince size (6.0 mm3). The subcutaneous transplants contracted spontaneously and regularly with an idioventricular rhythm. In addition, the transplanted cardiomyocytes were elongated and formed a myocardium-like pattern with blood vessels present within the contractile tissue. In the transmural left ventricular scar, both control and experimental fetal cardiomyocyte transplants 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 subcutaneous and myocardial scar tissue, and (3) improvements in cryopreservation techniques are required to augment the rates of cardiomyocyte survival observed in the study.
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