Lubricin expression in human osteoarthritic knee meniscus and synovial fluid: a morphological, immunohistochemical and biochemical study

The purpose of this study was to investigate the expression of lubricin, the product of the human PRG4 (proteoglycan 4) gene, in menisci and synovial fluid from normal donors and patients with osteoarthritis (OA), using a combination of histology, immunohistochemistry, ELISA and Western blotting analysis, to provide further insight on the role of this protein in the progression of OA and pathological processes in the meniscus. Lubricin expression was studied in samples from 40 patients and in 9 normal donors after arthroscopic partial meniscectomy. Histological analysis confirmed normal microanatomy and the absence of structural changes in control samples. Menisci derived from OA patients showed evidence of structural alterations, fibrillations and clefts. Immunohistochemical analysis revealed very strong lubricin immunostaining in normal menisci in contrast to weak/moderate staining seen in osteoarthritic menisci. Quantitative ELISA and Western blot analysis confirmed the above results. The findings of this study support the notion that changes in lubricin expression and boundary-lubricating ability of cartilage is followed by the development of OA. This study could provide the biological foundation for the development of novel therapeutic treatments, to be applied before the surgery, for the prevention of post-traumatic cartilage damage.