|M.Sc Student||Sviri Gill|
|Subject||The Influence of Intra-Articular Injections of TGF-B1 and|
IGF-1 on Healing and Regeneration in the
|Department||Department of Medicine||Supervisor||MRS Erella Livne (Deceased)|
Objective: Osteoarhritis (OA) the most common joint disease predominating in old age and is a major case of disability in aging. The disease is characterized by the slowly progressive destruction of articular cartilage of joints. These distraction have been attributed to a loss of tissue integrity due to metabolic and structural changes, and may reflect reduced ability of the chondrocytes to respond to various stimuli and stresses in the aging organism. The propose of the study was to test the effects of intraarticular injections of growth factors to knee and temporomandibular joints of aged mice on proteoglycan synthesis and on metalloproteases activity.
Materials: 20-month-old female ICR mice were treated by either three intraarticular injections of IGF-1 (25ng), TGF-b (10ng), TGF-b (10ng) + IGF-1(25ng), or saline, on days 1, 4, 7 (short interval), or on days 1, 8, 15 (long interval). Joints were dissected and cultured in the presence of 35S-sulfate and 3H-thymidine and their ex-vivo incorporations into DNA and proteoglycans were determined. Tissue samples were processed for morphology, autoradiography, immunohistochemistry and for metalloproteinases zymographic activity.
Results: After short interval treatment with TGF-b, TGF-b+IGF-1, the ex-vivo incorporations of 3H-thymidine and 35S-sulfate were elevated in tibia and femur, but were reduced in temporomandibular joint, while long interval treatment resulted in attenuated incorporation in femur. No significant response was observed after treatment with IGF-1in femur and mandibular condyle, while in the tibia an elevation was observed. Morphology revealed that in osteoarthritic cartilages (mandibular and femoral condyles) an enhanced proteoglycan synthesis and 35S-sulfate incorporation were observed after TGF-b, TGF-b+ IGF-1. These effects were more pronounced in the temporomandibular as compare to the femoral condyle and were more pronounced after the short-term interval. On the other hand, the tibial cartilage failed to respond to TGF-b and exhibited an increase in PG synthesis only after IGF-1 treatment. TGF-b+IGF-1 treatment resulted in reduced immunostaining for TGF-b and IGF-1. Increased zymographic activity of MMP-2,9 and increased positive immunostaining for MMP-2, -3 were observed after treatment with TGF-b +IGF-1.
Conclusions: Local administration of TGF-b or TGF-b+IGF-1induced proteoglycan synthesis and chondrocyte proliferation in OA cartilage in aged mice. This enhancement was limited to the time of treatment itself and was less pronounced when the administration interval was extended. However, OA cartilage was not sensitive to local administration of IGF-1. The failure of the treatment to induce prolonged increase in PG synthesis or chondrocyte proliferation could be related to the reduced endogenous production of IGF-1 and TGF-b in the tissue and to the observed increase in MMP-9 activity induced by the treatment.