Experimental study of tissue-engineered cartilage allograft with RNAi chondrocytes in vivo.

Purpose: To determine the effects of RNA interference (RNAi) on chondrocyte proliferation, function, and immunological rejection after allogenic tissue-engineered cartilage transplantation within bone matrix gelatin scaffolds. Methods: Seven million rat normal and RNAi chondrocytes were harvested and separately composited with fibrin glue to make the cell suspension, and then transplanted subcutaneously into the back of Sprague Dawley rats after being cultured for 10 days in vitro. Untransplanted animals served as the control group. The allograft and immunological response were examined at 1, 2, 4, 8, and 12 months postoperatively with hematoxylin and eosin histochemical staining, immunohistochemical staining (aggrecan, type II collagen, class I and II major histocompatibility complex), and flow cytometry for peripheral blood cluster of differentiation 4(+) (CD4(+)) and CD8(+) T-cells. Results: There was no infection or death in the rats except one, which died in the first week. Compared to the control group, the RNAi group had fewer eukomonocytes infiltrated, which were only distributed around the graft. The ratio of CD4(+)/CD8(+) T-cells in the RNAi group was significantly lower than the normal one (P<0.05). There were many more positively stained chondrocytes and positively stained areas around the cells in the RNAi group, which were not found in the control group. Conclusion: The aggrecanase-1 and aggrecanase-2 RNAi for chondrocytes decreased the immunological rejection effect.