Cartilaginous differentiation in the joint capsule.

The proliferation and differentiation of cells are greatly influenced by their environment. Many growth factors and cytokines are reported to be environmental factors that affect the proliferation and differentiation of cells. Mechanical stress is also considered to influence these physiological reactions. The joint capsule, which is a part of the joint tissue, plays a very important role in the stability of the joint and in maintaining the intracapsular phenomenon. In patients with dislocated hip arthropathy, this capsule is involved in the weightbearing function by forming a sliding surface between the capsule and the femoral head articular cartilage. The surface of the tissue macroscopically shows cartilaginous change, which indicates cartilaginous differentiation caused by mechanical stress. We examined the cartilage-specific proteoglycan component, which is composed of cartilaginou matrix at the differentiation site. We investigated proteoglycan production, molecular size, and the gene expression of cartilaginous substrate. At the inner layer of the weightbearing area of the joint capsule, proteoglycan production was significantly higher than that of other noncartilaginous tissue. We also identified the gene expression of cartilaginous proteoglycan using the reverse transcription polymerase chain reaction (RT-PCR) method.