Human coronary vascular smooth muscle and endothelium-dependent responses after storage at -75 degrees C

In the present study, we investigated whether an established method of cryostorage at -75 degrees C in the presence of dimethyl sulfoxide (Me2SO) and fetal calf serum (FCS) could preserve the vascular and endothelial responses of isolated human coronary arteries. A total of 123 ring segments (4-5 mm in length) of epicardial coronary arteries were isolated within 1 to 2 h from hearts of four patients receiving a cardiac transplant. Thirty-nine coronary ring segments were studied immediately upon cleaning of surrounding tissues, while 84 similarly cleaned segments were stored at -75 degrees C for 7 to 10 days prior to in vitro reactivity studies. In the freshly isolated coronary arteries, addition of prostaglandin F2 alpha, endothelin (ET-1), or acetylcholine consistently produced a dose-dependent contraction, reaching a maximum contractile force of 9.6 +/- 0.7, 4.5 +/- 0.5, and 3.1 +/- 0.5 g (M +/- SEM), respectively, while histamine, thrombin and substance P consistently produced an endothelium-dependent relaxation (EDR) with a maximum of -89 +/- 2.8, -85 +/- 5.0, and -72 +/- 3.5%, respectively. Isoproterenol produced an endothelium-independent relaxation (-82 +/- 4.5%). Cryostorage of human coronary arteries at -75 degrees C without cryoprotectant resulted in a complete loss of the contractile response. In contrast, addition of Me2SO and FCS in the cryostorage medium significantly preserved the contractile responses, although they were decreased (1.9 +/- 0.3, 1.5 +/- 0.3, and 0.6 +/- 0.1 g to PGF2 alpha, ET-1, and acetylcholine, respectively) when compared to the fresh controls. The maximum EDR to histamine, thrombin, and substance P in the cryostored coronaries were also reduced to -40 +/- 5.6, -21 +/- 3.3, and -47 +/- 4.7%, respectively, and the isoproterenol-induced relaxation was reduced to -62 +/- 4.1%. These results suggest that although the cryostorage method described in the present report provided only limited preservation of human coronary arteries, significant vascular smooth muscle and endothelial-dependent functions were retained. Thus, it is possible that further refinement of the present cryostorage methodology may provide better preservation of functionally viable human blood vessels.