Glucosamine reduces anabolic as well as catabolic processes in bovine chondrocytes cultured in alginate 1

SummaryObjectiveTo investigate the working mechanism of glucosamine (GlcN) by studying the effect of different GlcN derivatives on bovine chondrocytes in alginate beads under anabolic and catabolic culture conditions.MethodsBovine chondrocytes seeded in alginate beads were treated with different concentrations of glucosamine–sulfate (GlcN-S), glucosamine–hydrochloride (GlcN-HCl) or N-acetyl–glucosamine (GlcN-Ac). Culture conditions were anabolic, 3 day pre-culture followed by 14 days' treatment; catabolic, extracellular matrix (ECM) breakdown induced by 10 ng/ml interleukin-1β (IL-1β); or a situation with balance between ECM breakdown and synthesis, 24 days' pre-culture followed by 14 days' treatment. The outcome measurements were total glycosaminoglycan (GAG) and DNA content per bead.ResultsIn the situation with balance between ECM breakdown and synthesis, GlcN-Ac had a small stimulatory effect on total GAG content. GlcN-S and GlcN-HCl had no effect. Under anabolic condition 5 mM GlcN-S and GlcN-HCl significantly reduced total GAG content. GlcN-Ac did not show this effect. IL-1β induced catabolic effects were prevented by adding 5 mM GlcN-HCl. Interference of GlcN with glucose (Gluc) was demonstrated by adding extra Gluc to the medium in the anabolic culture conditions. Increasing extracellular Gluc concentrations diminished the effect of GlcN.ConclusionGlcN-S and GlcN-HCl, but not GlcN-Ac, reduce anabolic and catabolic processes. For anabolic processes this was demonstrated by decreased ECM synthesis, for catabolic processes by protection against IL-1β mediated ECM breakdown. This might be due to interference of GlcN with Gluc utilization. We suggest that the claimed structure modifying effects of GlcN are more likely based on protection against ECM degradation than new ECM production.