Differential sensitivity to cryopreservation of clonogenic progenitor cells and stromal precursors from leukemic and normal bone marrow

The survival of human leukemic and normal progenitor cells was determined after cryopreservation. Thirteen marrows from patients with acute myeloid leukemia (AML) were studied as fresh and eight as cryopreserved samples. Marrows from five normal donors were studied as both fresh and cryopreserved samples. Although the number of bone marrow mononuclear cells (BMMC) recovered after cryopreservation was always lower than that originally stored, no significant difference was observed between the clonogenic potential of fresh and cryopreserved BMMC from either the leukemic or the normal samples. When grown in long‐term bone marrow culture (LTBMC), the cultures initiated with cryopreserved BMMC failed to form a confluent stroma, and the duration of nonadherent and progenitor cell production was significantly lower than that from fresh samples. However, when these cryopreserved samples were recharged onto preformed irradiated stroma, the duration of the cultures improved significantly. We conclude that it is the bone marrow stromal cells rather than the clonogenic progenitors which are sensitive to the effects of cryopreservation. Thus cryopreservation does not appear to influence the activity of AML progenitor cells. Our results also indicate that frozen marrow can be used for LTBMC experiments if cultured on a preformed stromal layer.