Long term bone marrow cultures: an ultrastructural review

Abstract

Long-term liquid cultures of bone marrow support the growth and proliferation of self renewing haemopoietic stem cells and the majority of myeloid lineages. The maturation of granulocyte elements occurs in normal cultures, but this may be shifted to erythropoiesis by the addition of a stimulus such as serum from anaemic mice. The continued production of stem cells and differentiating populations of either granulocytes or erythroid cells is dependent upon the establishment and maintenance of an adherent layer in the cultures which arise from the stromal cells in the original marrow inoculum. To date, the presence of adipocytes, fibroblasts, reticulum cells, and endothelial cells has been established amongst the stromal cells; and neutrophil and basophil granulocytes, megakaryocytes, full erythroid differentiation, and monocytes and macrophages have been identified in the haemopoietic lineages. Interactions at the cellular level appear to occur between the lipid synthesising adipocytes and developing granulocytes, and a central macrophage and erythroblasts, forming an 'in vitro' erythroblastic islet. These associations may form aspects of an 'in vitro' haemopoietically inductive microenvironment.