Effects of a preformed extracellular matrix on long-term serum-free bone marrow culture.

The extracellular matrix (ECM) produced by the stromal layer plays a key role in the regulation of commitment and differentiation of hematopoietic cells. Long-term bone marrow culture (LTBMC) allows analysis of the stromal microenvironment. Recently, serum-free LTBMC has been described, but the formation of a classical adherent layer was never observed under these conditions. We have evaluated the effect(s) of a chemically well defined ECM on serum-free and serum-dependent LTBMC. In serum-dependent cultures ECM did not induce a significant increase of hematopoiesis. In serum-free conditions, a marked improvement of hematopoiesis was observed, both in terms of CFU-GM and BFU-E yield and in duration of cultures. A confluent stromal layer was observed only in the presence of ECM. The present results indicate that the addition of ECM to serum-free cultures provides a standardized culture condition, while improving progenitor cell recovery and allowing formation of a confluent stromal layer. Moreover, ECM+LTBMC may provide a model to study the effect(s) of adhesive proteins and hematopoietic growth factors normally present in serum.