Background Musculoskeletal injures are the most common cause for severe, chronic pain and physical disability affecting hundreds of millions of people around the world and represent a major concern also in sports medicine. A preclinical study evaluated the impact of chondroitin sulfate (CS) and glucosamine (GLU) combination (both compounds used in the treatment of osteoarthritis) on muscle healing and force recovery. Although the mechanisms of action of the combination CS +GLU have been largely studied in articular tissue, its potential therapeutic effects for muscle healing remain still unknown.

Objectives The aim of the present study is to elucidate the mechanisms of action responsible for this interesting benefit.

Methods Human skeletal muscle biopsies were digested with Protease type XIV and the resulting tissue suspension were collected by centrifugation. The digested muscle pellet was then triturated to liberate the human satellite cells. Differential centrifugations were used to enrich the cell fraction. Cell suspension was then transferred onto cell-culture dishes in Growth media (DMEM/M-199 medium (3:1) with 10% FBS, 10 µg/ml insulin, 2 mM glutamine, 25 ng/ml fibroblast growth factor, and 10 ng/ml epidermal growth factor) and cells were expanded in a growing monolayer. The effect of CS+GLU treatment in primary human skeletal muscle cells was evaluated in a cell proliferation assay. NF-kB intracellular levels were determined by Western Blot. TNF-a production was measured in culture medium supernatants by ELISA.

Results An enhancement in cell proliferation was found in CS+GLU treatments at a concentrations of 100 and 200 µg/ml, increasing 1,60-fold (p<0,01) and 2,04-fold (p<0,001), respectively, compared to untreated cells. In addition, myoblasts were then incubated with IL-6 (50 ng/ml) for 72 hour in order to induce an inflammatory environment. The results showed an IL-6 induced-reduction on cell proliferation in all groups, although the data did not reach statistical significance. Therefore, an IL-6 inhibitory effect on cell proliferation in human muscle cannot be ensured. We also measured the effect of the combined treatment CS+GLU on NF-kB activation and TNF-a production in human skeletal muscle cells in primary culture. Despite of TNF-a levels were undetectable in cell supernatants, preliminary data showed a slight reduction on NF-kB signalling pathway. Global gene expression profiles, measured by microarrays and GeneChip Human Gene 1.0 ST Arrays (Affymetrix), will also be analysed.

Conclusions The mechanisms of action involved in the potential therapeutic effect described in an in vivo injured muscle model seem to be related with an increase in muscle cell proliferation, together with blocking NF-kB nuclear translocation and TNFa production. Although further investigation is required, these preclinical data suggests potentially positive effects of CS and GLU administration for the treatment of skeletal muscle injuries in sports medicine.

Disclosure of Interest None declared