The effect of ice formation on the function of smooth muscle tissue stored at -21 or -60 °C

Abstract

The mechanisms by which single cells are injured during freezing are relatively well understood, but it is likely that additional factors apply to tissues and organs, factors that may be responsible for the poor suecess of attempts to cryopreserve complex multicellular systems. One such factor may be the formation of extracellular ice. {A figure is presented}. This study was designed to discover whether ice formation as such is detrimental to the contractile recovery of pieces of mammalian smooth muscle after storage at subzero temperatures. Strips of taenia coli muscle were equilibrated with 2.56 M Me2SO in a buffered solution, cooled at either 0.3 or 2 °C/min to -21 °C and then held at this temperature in the frozen state. Other muscle strips were bathed in a solution the composition of which mimicked that of the unfrozen phase of the previous solution at -21 °C; it contained 4.49 M Me2SO and 1.75 times the normal concentration of salts, and muscles equilibrated with this solution were also cooled at either 0.3 or 2 °C/min to -21 °C, and then held unfrozen for the same length of time. It was shown that exposure to -21 °C and the increased concentration of solutes had little effect on the contractile recovery of the muscles, whereas ice formation was damaging. Furthermore, the rate of cooling had a marked effect upon functional recovery in the frozen muscles, and this could be correlated with the known effect of these cooling rates on the pattern of ice formation in the tissue. The effect was also seen in muscles frozen at -60 °C. Improved buffering increased the functional recovery of all groups, but the effect of ice, and of cooling rate in the presence of ice, was confirmed. These findings may have significant implications for attempts to cryopreserve complex tissues and organs. © 1983.