Expression of cytokines after meniscal rasping to promote meniscal healing

Purpose: We have developed a new surgical procedure of rasping a meniscal s urface to repair a tear in the avascular zone. This procedure stimulates va scular induction to the tear, resulting in meniscal healing. The purpose of this study was to elucidate the mechanism of vascular induction and menisc al healing. Type of Study: Randomized trial. Methods: A full-thickness long itudinal tear of 5 min in length was created in the avascular zone of the a nterior segment of both medial menisci of rabbits. Meniscal rasping of abou t 0.5 mm in depth was then done on the femoral surface of the left meniscus from the parameniscal synovium to the inner portion including the longitud inal tear, and the right meniscus was left untreated as a control. After su rgery, at 1, 7, 14, 28, 56, and 112 days, 4 rabbits were killed, both media l menisci were resected, and immunohistochemical staining with monoclonal a ntibodies was used to quantify expression of interleukin-1 alpha (IL-1 alph a), transforming growth factor-beta1 (TGF-beta1), platelet-derived growth f actor (PDGF), and proliferating-cell nuclear antigen (PCNA) on the femoral surface of the menisci. A positive ratio of immunostaining was encountered. Results: The positive ratio of IL-1 alpha, TGF-beta1, PDGF, and PCNA on th e rasped surface area reached its peak at 1, 7, 14, and 7 days, respectivel y, after surgery, and thereafter gradually declined. Although the time cour se of the positive ratio was different among these cytokines, the positive ratio on the rasped surface was significantly higher than that on the contr ol surface at the early stage of the observation period. Conclusions: The c ytokine network on the rasped meniscal surface appears to be the key to exp laining the mechanism of vascular induction and ineniscal healing by menisc al rasping.