Hematopoiesis on cellulose ester membranes. XIII. A combination of cloned stromal cells is needed to establish a hematopoietic microenvironment supportive of trilineal hematopoiesis.

A mixture of stromal cells from murine bone marrow placed upon cellulose ester membranes (CEM) and then implanted intraperitoneally (i.p.) in mice results in a regenerated hematopoietic microenvironment which supports trilineal hematopoiesis. We used this model to study the capacity of 5 cloned murine stromal cell lines of marrow origin to support hematopoiesis in vivo: MBA-1 (fibroblast); MBA-2 (endothelial); MBA-13 (fibroendothelial); 14F1.1 (endothelial-adipose); and 14M1.4 (macrophage).10(7) stromal cells of a single cell line were applied to 1.5 cm2 CEM, which were folded into tubes and implanted i.p. into mice. Similarly, combinations of 4, 3 and 2 stromal cell lines were applied to CEM and implanted i.p. Single lines were implanted into syngeneic hosts of the same murine strain from which the clone was derived and into nude mice. Combinations of stromal cells were implanted only in nude mice to avoid allogeneic incompatibility. CEM implants were removed after intervals of 5 to 36 weeks and examined histologically. 1) Stromal cells of a single phenotype did not develop hematopoiesis. 2) A combination of 4 stromal phenotypes (MBA-1, MBA-2, MBA-13 and 14F1.1) formed a hematopoietic microenvironment supportive of trilineal hematopoiesis and bone. 3) The combination of 14F1.1 (endothelial adipose) + a second stromal phenotype--MBA-1 (fibroblast) or MBA-2 (endothelial) or MBA-13 (fibroendothelial) also supported trilineal hematopoiesis and bone. 4) CEM coated with MBA-13 or MBA-1 developed bone but no hematopoiesis. The endothelial-adipose phenotype appears to be essential to support hematopoiesis but requires other types of stromal cells--fibroblast, fibroendothelial or endothelial phenotype.