Effects Of Cyclic Mechanical Stretch On BMP-2 In RA And OA Fibroblast-like Synoviocytes

Synovium of RA and OA are involved in Arthritis. Inflammatory factors and mechanical stimuli play important roles for synovial tissue.Inflammatory factors and mechanical stimuli are two important factors affecting the disease development. B cells and macrophages in synovium secrete inflammatory cytokines such as interleukin-1 (IL-1), tumor necrosis factor-α(TNF-α) etc. into the synovial fluid. In the inflammatory environment , prostaglandin (PGE2 ), endothelial cell adhesion molecule (hUVEC), matrix metalloproteinases (MMPs) and other cytokines are promoted and thus lead to synovial thickening, hyperemia, edema and infiltration of lymphocytes and macrophages. On the other hand, the mechanical stimuli under physiological conditions can make synovial hyperplasia, cell activation, proliferation, and aggravate chronic inflammatory.Bone morphogenetic proteins 2 (BMP-2) are a class of multifunctional glycoprotein belonging to TGF-βfamily. They play roles in embryogenesis, nerve repair, angiogenesis etc. Not only involved in bone formation and osteophyte formation, BMP-2 also contribute to regulation of cell differentiation , proliferation. They have links with the abnormal proliferation of synoviocytes.In this study, biomechanics, cell biology, molecular biology and other methods were used for the respond of human knee synovial fibroblast-like cells(FLS) to cyclic mechanical stretching. We focused on the way of mechanical signals - gene expression. Major work and conclusions are as follows:①The synoviocytes from normal, rheumatoid arthritis and osteoarthritis tissue were cultured. Semi-quantitative PCR and western blotting were used to detect the differential expression of BMP-2 mRNA. The results show that BMP-2mRNA expressed higher in OA FLS than normal and RA (P<0.05). It suggested that the differences in the pathogenesis of OA and RA.②Cyclic mechanical stretching devices were used to influence the normal, RA, OA FLS at normal and inflammatory conditions. The frequency of strain was 0.5 HZ and the amplitude 6%. RNA were collected at the timepoint of 2, 6 h. Biochemical response and gene expression of cyclic mechanical strain on FLS under the conditions of inflammatory factors were explored. The results showed:1) Cyclic mechanical stretch of 6%, 0.5HZ, 2h had no significant effect on BMP-2 mRNA levels on the three kinds of FLS(P>0.05). Cyclic mechanical stretch of 6%, 0.5HZ, 6h significantly increased BMP-2 mRNA level in all FLS(P<0.05).2) The inflammatory cytokines IL-1β(interlukin-1β) induced a large number of BMP-2 mRNA in a time-dependent pattern within 2-6h(P<0.05).3)6%, 0.5HZ, 2h and 6%, 0.5HZ, 6h mechanical stretch up-regulated normal, RA FLS(P<0.05) and down-regulated OA-FLS significantly under the conditions of IL-1β(P<0.05).In summary, this study shows that both mechanical stimulation and inflammatory cytokines increased the expression of BMP-2 gene. The difference of BMP-2 gene expression caused by mechanical stimulation in normal, OA, RA FLS under inflammatory conditions indicated the different roles of mechanical stretch for OA, and RA disease.