Introduction and Aims: There has been a lack of studies investigating the effect of cytokines on human meniscal cartilage. We investigated the regenerative potential of meniscal cartilage at different zones of human and sheep menisci under the effect of platelet-derived growth factor AB (PDGF-AB), insulin-like growth factor I (IGF-I), and basic fibroblast growth factor (bFGF) in a dose-dependent manner.

Method: Monolayer cell cultures were prepared from the inner (avascular), middle, and outer (vascular) zones of human and sheep lateral menisci. Fibrochondrocytes were exposed to various concentrations of each of the three growth factors. To assess cell proliferation, 3H-Thymidine uptake assay was used. For assessment of matrix formation, radioactive 35S uptake assay and Blyscan assay were used to assess newly formed glycosaminoglycans (GAGs), 14C-Proline uptake assay and ELISA were used to assess newly formed collagen.

Results: The growth factors under investigation stimulated the fibrochondrocytes isolated from all meniscal zones in a similar dose-dependent fashion. In human meniscal cells, PDGF-AB at a concentration of 200 ng/ml stimulated proliferation by up to four-fold and GAGs synthesis by up to 12-fold (p < 0.001). IGF-I and to a lesser extent bFGF, at concentrations of 100 and 200 ng/ml, also stimulated both cell proliferation and matrix formation in all three meniscal zones (p < 0.001). PDGF and to a lesser degree IGF at concentrations of 100 and 200 ng/ml have stimulated collagen type I synthesis by up to two-fold.

Conclusion: The results of this study indicate that fibro-chondrocytes originating from the avascular zone of the meniscus have the ability to proliferate and to regenerate their surrounding extracellular matrix when exposed to growth factors. This is an encouraging observation that will form the basis for in vivo research, aimed at enhancing meniscal repair, even within the avascular zone, following surgical repair.

Aims: This study investigated the regenerative potential of different parts of human and sheep menisci when exposed to PDGF-AB, IGF-I, and bFGF in a dose dependent manner. Methods: Monolayer cell cultures were prepared from inner, middle, and outer zones of the lateral menisci of sheep and from humans obtained following total knee replacement and partial meniscectomy. Various concentrations of each of the three growth factors were used in addition to control samples. Wemeasured the incorporation of Radio-labelled thymidine to assess cell proliferation and radioactive sulphate and radio-labelled proline to assess matrix formation. Results: Both PDGF-AB and IGF-I have a signiþcant effect in promoting both þbrochondrocyte proliferation and matrix formation in the all meniscal zone zones at 100 and 200 ng/ml (p< 0.001). However, cells isolated from the inner avascu-lar zone of the meniscus showed a higher response than those isolated from the outer vascular zone. bFGF has also stimulated both cell proliferation and matrix formation, but to a lower degree in comparison to PDGF-AB and bFGF, in all meniscal zones of sheep meniscus (p< 0.05). Whereas, in humans, bFGF stimulated only cell isolated form the inner zone of the meniscus (p< 0.05). Conclusions: These results indicate that the meniscal tissue in the avascular zone has the ability to regenerate when exposed to growth factors such as PDGF, IGF-I, and bFGF. This could improve the therapeutic methods to treat meniscal injuries and, ultimately, reduce the incidence of osteoarthritis of the knee.