Effects of glycosaminoglycans on U-937 leukemia cell proliferation and differentiation: structure-function relationship.

Glycosaminoglycans (heparins, dermatan sulfate, chondroitin sulfate) with different structures and physicochemical properties were evaluated for their capacity to influence proliferation and differentiation of U-937 cell line. The contrasting and specific effects of glycosaminoglycans (depending on their structures and properties) on a leukemia cell line could help explain the regulation of proliferative and/or differentiative processes of hematopoietic cells in order to clarify the control of development and differentiation of hematopoietic progenitor cells by bone marrow extracellular matrix. Heparin from beef intestinal mucosa, heparan sulfate from beef spleen, dermatan sulfate from beef intestinal mucosa, and chondroitin sulfate from bovine trachea were extracted and purified, and their purity, structures, and physicochemical properties were evaluated. Fast-moving heparin was obtained by its selective precipitation as barium salt, and partially desulfated and re-N-sulfated heparin was produced by chemical modifications. Different glycosaminoglycans were tested to evaluate their effects on proliferation and differentiation processes of a monoblastic leukemia cell line (U-937). Heparin and derivatives (from 0.1 to 100 micrograms/ml) inhibit cell proliferation; heparan sulfate does not produce modifications, while chondroitin sulfate and dermatan sulfate (from 0.01 to 100 micrograms/ml) significantly stimulate cell growth. Cell differentiation was evaluated by cytoenzymatic determination of alpha-naphthyl butyrate esterase and by fluorescein-labeled anti-HLA-DR, anti-CD11b, and anti-CD14 antibodies. Nitro blue tetrazolium reduction and phagocytosis were also evaluated. Heparin and derivatives significantly increase U-937 differentiation. Heparin sulfate has no effect, while chondroitin sulfate and, to a lesser extent, dermatan sulfate, induce a strong decrease of differentiative markers. The regulation of U-937 cell properties appears to be related to charge density and to the amount of N-sulfate and N-acetyl groups. In particular, glycosaminoglycans with lower sulfate-to-carboxyl ratios and N-sulfate group percentages (chondroitin sulfate and dermatan sulfate) stimulate proliferation and produce a decrease of differentiative markers; on the contrary, polysaccharides with high charge density and N-sulfate group amounts (heparin and derivatives) inhibit U-937 proliferation and induce terminal differentiation. A previous paper (N. Volpi, L. Bolognani, A. Conte, and M. Petrini, (1993) Leukemia Res. 17, 789-798) demonstrates dissimilar effects on U-937 cells by chondroitin sulfates with different structures and physicochemical properties. In this study we confirm the importance of glycosaminoglycan structures and physicochemical properties in regulating cell functions. Possible mechanisms of action are discussed.