Aplastic anaemia with marrow defective in formation of fibroblastoid cell colonies in vitro

The formation of fibroblastoid colonies by marrow cells in vitro has been used as a putative assay for a stem cell of haemopoietic stroma. Bone marrow from one patient with aplastic anaemic did not form any of these colonies, while its growth in diffusion chambers as an indirect measure of a haemopoietic stem cell was even better than normal. On the other hand, marrow from the other aplastic patient showed only quantitative decrease in the formation of fibroblastoid colonies and simultaneously grew very poorly in diffusion chambers. These patients were indistinguishable by the cytological examination of their marrow, however, the peripheral blood abnormalities were expressed less severely in the first patient. These results suggest the contribution of the defect in marrow cells, which form fibroblastoid colonies in vitro to the development of aplastic anaemia in these patients.