Stromal colonies can be grown from the non-adherent cells in human long-term bone marrow cultures.

The absence of a pluripotent stem cell assay for human cells means that we must rely on assays of committed progenitors as a means for examining the ability of long-term bone marrow culture (LTBMC) to support haemopoiesis. The CFU-GM assay has been employed by many authors to demonstrate that the proliferative capacity and differentiation potential has been retained in LTBMC. In this study the non-adherent cells from human LTBMC were set up using a liquid culture technique for the clonal proliferation of stromal colonies (CFU-F). Weekly plating of the non-adherent cells produced CFU-F for up to 7 wk. Morphological, cytochemical and antigenic characterisation of these colonies revealed that they were identical to those grown from bone marrow de novo. LTBMC can now be used to identify the interactions between the haemopoietic inductive microenvironment and stromal progenitors and allow us to investigate the precise role of cell-cell interactions or cytokine influences on the proliferative capacity of stromal cell progenitors.