CCN2 and musculoskeletal system disorder: Although further studies on humans are needed, these findings suggest that serum levels of TGFB1, CTGF and MMP2, and perhaps even hydroxyproline, may serve as serum biomarkers of underlying tissue fibrogenic changes in this rat model of work-related musculoskeletal disorders, and that serum IL-6 may be a biomarker of either musculotendinous inflammatory or fibrotic responses.