The Knee Joint Tissues Differ Significantly in TGFβ1 Expression and Its Sensitivity

Abstract

The knee joint is the largest and most complex joint in the human body. In this study, we investigated TGFβ1 expres-sion in the outer meniscus, inner meniscus and articular cartilage of rabbit and human knee tissue (outer and inner me-nisci) in order to determine the potential role of this factor in normal meniscal function. We also examined the potential of TGF-β1 stimulation to promote tissue regeneration in the two different regions of rabbit knee meniscus tissue. Im-munohistochemical investigations of TGF-β1 were performed on rabbit and human knee tissue. The rabbit outer, inner and articular cartilage cells were culture and stimulated with TGF-β1 followed by cell proliferation assay and extracel-lular matrix analysis. Regulatory studies were performed using TGF-β1 inhibitors SB-431542 and PD98059. Gene ex-pression was analyzed by quantitative polymerase chain reaction. We found marked regional variation in the expression of TGF-β1 in rabbit and human knee. TGF-β1 expressions are relatively greater in the outer meniscus than inner me-niscus. Furthermore, we found that exogenous TGF-β1 stimulation increased cell proliferation and aggrecan synthesis more so in the outer than in the inner meniscus. Articular cartilage tissue shows moderate levels of cell proliferation and ECM synthesis when compared with outer and inner meniscus. These findings suggest that growth factors used to en-hance the repair and regeneration of meniscal tissue should be tailored to enhance region-specific variation in cell pro-liferation and extracellular matrix synthesis.