Glucosamine promotes chondrogenic phenotype in both chondrocytes and mesenchymal stem cells and inhibits MMP-13 expression and matrix degradation

Objectives: Glucosamine (GIcN), a natural amino monosaccharide, is a constituent of glycosaminoglycans (GAGs) found in hyaline cartilage. GIcN salts constitute a new class of nutraceutical components with putative chondroprotective activity, which may target chondrocytes as well as chondroprogenitors cells, such as mesenchymal stem cells (MSCs), during cartilage turnover and repair. In the present study, we examined the effects of GIcN on chondrogenesis of human MSCs (hMSCs) and the phenotype of normal and osteoarthritic human articular chondrocytes, using an in vitro pellet culture model maintained in a defined medium. Methods: hMSCs and normal and osteoarthritic human chondrocytes grown as pellet cultures, stimulated or not with interieukin-1 beta (IL-1 beta), were treated with varying doses of GIcN. Expression of cartilage matrix genes and cartilage degrading enzymes was determined by semiquantitative and quantitative real-time reverse transcription polymerase chain reaction (RT-PCR), and by histological staining of cartilage markers, as well as sulfated GAG (sGAG) analysis and Western blotting. Results: Chondrocytes grown in the presence of serum for 11 days showed decreased expression of the cartilage matrix genes, collagen type 11 (collagen II) and aggrecan, as early as day 3, which was reversed with GIcN treatment by day 11. Both hMSCs and choncrocytes grown as pellet cultures in defined medium and treated with 100 mu M GIcN exhibited enhanced expression of collagen II and aggrecan as well as increased content of sGAG, when compared to control untreated pellets. However, high doses of GIcN (10-20 mM) were inhibitory. GIcN treatment partially blocked IL-1 beta mediated downregulation of collagen II and aggrecan expression and inhibited expression of the matrix degrading enzyme, matrix metalloproteinase 13 (MMP-13), in both chondrocytes and hMSCs undergoing chondrogenesis. Conclusions: These observations suggest that GIcN treatment enhances hMSC chondrogenesis and maintains cartilage matrix gene expression in chondrocytes, which may account for some of the reported chondroprotective properties of GIcN on cartilage. (c) 2007 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.