Extracellular matrix promotes the growth and differentiation of murine hematopoietic cells in vitro.

We have developed a long-term culture system in which murine marrow cells are cultured on a complex extracellular matrix (ECM) that is derived from marrow and extracted with guanidine hydrochloride and dithiothreitol. Marrow cultures were established with fresh murine marrow cells and recharged at 2 wk (week 0). Phase microscopy showed a dramatically increased adherent cell layer development on ECM compared with controls within a week after recharge. By electron microscopy, this adherent layer was composed of numerous reticular cells apparently attached to the ECM which extended cytoplasmic projections to the surrounding hematopoietic cells. Adherent cellularity on ECM-coated dishes increased to 30 times the control values by week 2. Cumulative suspension cells on ECM dishes were eight times controls. ECM influenced both hematopoietic progenitor cell proliferation and differentiation. Adherent colony-forming unit-granulocyte/macrophage and colony-forming unit-megakaryocyte were greater than 30 and 15 times the control values, respectively, by week 2 (P less than or equal to 0.05). There were more mature granulocytic and megakaryocytic cells in ECM-coated dishes than in controls at all time points. This new culture system directly demonstrates that ECM is an important component of the hematopoietic microenvironment.