Dextran sulfate promotes the rapid aggregation of porcine bone-marrow stromal cells

Despite the fact that cells of the mammalian stromal compartment of bone marrow have been shown to contain multipotential stem cells when studied in diffusion chambers it is notable that the same range of possible phenotypes (e.g., chondrocytic) has not been induced in freshly isolated marrow stromal cells in vitro. To investigate the possible role of glycoconjugates on phenotype expression, the effects of chondroitin sulfate, dermatan sulfate, dextran 500, and dextran sulfate on the cell morphology and differentiation of confluent porcine bone-marrow stromal-cell monolayers were studied. Of these glycosaminoglycan molecules only dextran sulfate induced confluent porcine bone-marrow stromal-cell monolayers to retract into tight, circular cell aggregates. Retraction began within 6 h, was complete after 3-5 days, and was dose dependent. Subsequent removal of dextran sulfate from the culture medium resulted in a return to a monolayer culture. Aggregated cells were essentially nonmitotic but dye exclusion indicated high cell viability. Dexamethasone, ascorbate, and beta-glycerophosphate produced no morphological change within 6 days when administered alone, but increased proliferation and aggregation in dextran sulfate-treated cultures. Immunocytochemistry of monolayer cultures revealed positive staining for type I but not type II collagen and addition of dexamethasone, ascorbate, and beta-glycerophosphate increased type I collagen deposition. In contrast, the centers of dextran sulfate-induced aggregates were positive for type II collagen, whereas type I collagen was only present at the periphery of the aggregates. Further addition of dexamethasone, ascorbate, and beta-glycerophosphate had little effect.(ABSTRACT TRUNCATED AT 250 WORDS)