Abstract
The knee joint is the largest and most complex joint in the human body. In this study, we investigated TGFβ1 expression in the outer meniscus, inner meniscus and articular cartilage of rabbit and human knee tissue (outer and inner menisci) 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. Immunohistochemical 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 extracellular matrix analysis. Regulatory studies were performed using TGF-β1 inhibitors SB-431542 and PD98059. Gene expression 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 meniscus. 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 enhance the repair and regeneration of meniscal tissue should be tailored to enhance region-specific variation in cell proliferation and extracellular matrix synthesis.
Highlights
The knee joint is one of the largest articulations in the body
TGF-β1 is a potent inhibitor of growth in most cell types, it has been shown to stimulate growth of certain cells in culture, such as mouse bone marrow mesenchymal stem cells [18], rat and avian articular chondrocytes [19,20], human nasal septal chondrocytes [21] and cells with an osteoblastic phenotype from rat parietal bone [22]
We first did immunostaining of the rabbit knee tissue to know the regional difference in expression of Transforming growth factor-β (TGF-β) level
Summary
The knee joint is one of the largest articulations in the body. Menisci within the knee are crucial to its proper function. The two components are the outer and inner menisci, which differ in the predominant collagen and proteoglycan isomers that constitute them. A torn meniscus can result from any activity that causes forcefully twist or rotate knee, such as aggressive pivoting or sudden stops and turns. Treatment of tears is confounded by a limited blood supply, which effectively ends at the transition of the inner and outer regions [3]. To aid healing of torn menisci, investigators are examining the potential of growth factor therapy. Primary candidates among these are basic fibroblast growth factor bFGF [4], TGF-β [5,6] and platelet derived growth factor-AB. Previous studies have indicated a dramatic, order-of-magnitude effect on meniscal cell proliferation with exogenous bFGF in monolayer culture [4]
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