Response of murine stromal bone marrow cultures to α-particle irradiation in vivo and in vitro at osteosarcomogenic α-radiation doses

Stromal cells belonging to the bone marrow microenvironment are altered in mice at fisk of bone tumour development after Am-241 injection. This can be observed with selective cell culture techniques long before the tumours become manifest. Colony forming assays in vitro showed increases in the number of stromal stem cells at lower dose levels but a decrease in cell number at higher dose levels. The in vitro osteogenic capacity of marrow, which is attributed to stromal cells of the osteogenic lineage, was significantly reduced. The changes were persistent until at least 1 yr after Am-241 injection. In vitro alpha-irradiation of bone marrow also reduced the osteogenic capacity of the bone marrow at dose levels that were comparable with those producing an effect in vivo. This suggests a direct effect of alpha-particle irradiation on stromal bone marrow cells. These data and previous results on the regulatory role of the stroma in haemopoiesis show that stromal bone marrow cells.should be considered as sensitive targets for chronic low level alpha-particle irradiation.