Influence of different temperature of cryopreservation on the proliferative potential of human bone marrow progenitor cells. Transplantological implications.

The influence of two different temperatures of cryopreservation of human bone marrow on the proliferative potential of granulocyto-monocytic (GM-CFU), erythroid (BFU-E) and megakaryocytic (CFU-Meg) progenitors was investigated. For this purpose, the human bone marrow cells were cryopreserved in the standard freezing medium supplemented with 10% DMSO and stored at -80 degrees C in a freezer or at -196 degrees C in a liquid nitrogen tank. Subsequently, cells were thawed, plated and stimulated in vitro to grow myeloid colonies. Unexpectedly, bone marrow cells stored at -80 degrees C formed about 60%, and those stored at -196 degrees C formed barely 8% of CFU-GM and BFU-E colonies respectively, in comparison to control non-frozen cells. CFU-Meg progenitors appeared to be the most sensitive to cryopreservation among all clonogeneic cells tested. The number of CFU-Meg derived colonies decreased to 20% in marrow cryopreserved at -80 degrees C and to about 2% in cells stored in liquid nitrogen at -196 degrees C. These data demonstrate the advantages of bone marrow storage at -80 degrees C over freezing in liquid nitrogen at -196 degrees C. Moreover, the increased sensitivity of CFU-Meg to cryopreservation could explain, at least partially, the clinical phenomenon of protracted thrombocytopenia observed in patients transplanted with the cryopreserved bone marrow cells.