【Abstract】 Objective To compare the effect of PLGA and collagen sponge combined with rhBMP-2 on repairing ofarticular cartilage defect in rabbits respectively. Methods PLGA and collagen sponge were made into cyl inders which were 4 mm in diameter and 3 mm in thickness, and compounded with rhBMP-2 (0.5 mg). Defect 4 mm in diameter were made in both of femoral condyles of 24 two-month-old New Zealand white rabbits. The defects in right 18 knees were treated with PLGA/rhBMP-2 composites (experimental group 1), and the left 18 knees were treated with collagen sponge/rhBMP-2 composites (experimental group 2), the other 12 knees were left untreated as control group. At 4, 12 and 24 weeks after operation, the animals were sacrificed and the newly formed tissues were observed macroscopically and microscopically, graded histologically and analyzed statistically. Results From the results of macroscopical and microscopical observation, in the experimental group 1, the defects were filled with smooth and translucent cartilage; while in the experimental group 2, the white translucent tissues did notfill the defects completely; and in the two experimental groups, the new cartilage tissues demarcated from the surrounding cartilage,chondrocytes distributed uniformly but without direction; a l ittle fibrous tissue formed in the control group 4 weeks postoperatively. In the experimental group 1, the defects were filled completely with white, smooth and translucent cartilage tissue without clear l imit with normal cartilage; while in the experimental group 2, white translucent tissues formed, the boundary still could be recognized; in the two experimental groups, the thickness was similar to that of the normal cartilage; the cells paralleled to articular surface in the surface layer, but in the deep layer, the cells distributed confusedly, the staining of matrix was positive but a l ittle weak; subchondral bone and tide mark recovered and the new tissue finely incorporated with normal cartilage;however, in the control group, there was a l ittle of discontinuous fibrous tissue, chondrocytes maldistributed in the border andthe bottom of the defects 12 weeks postoperatively. In the experimental group 1, white translucent cartilage tissues formed, the boundary disappeared; in the experimental group 2, the color and the qual ity of new cartilage were similar to those of 12 weeks; in the two experimental groups, the thickness of the new cartilage, which appeared smooth, was similar to that of the normal cartilage, the chondrocytes arranged uniformly but confusedly; the staining of matrix was positive and subchondral bone and tide mark recovered, the new tissue finely incorporated with normal cartilage; in the control group, a layer of discontinuous fibrous tissue formed in the bottom of the defects 24 weeks postoperatively. Results of histological grade showed that there were significantdifference between experimental group (1 and 2) and control group at any time point (P lt; 0.01); the scores of 12 weeks and 24 weeks in experimental group 1 and 2 had a significant difference compared with that of 4 weeks (P lt; 0.01), there was no significant difference between 12 weeks and 24 weeks (P gt; 0.05), and there were no significant difference between the two experimental groups at the same time point (P gt; 0.05). Conclusion Both PLGA and collagen sponge as a carrier compounded with rhBMP-2 can repair articular cartilage defects.
ObjectiveTo study the effect and feasibility of poly-lactide-co-glycolide (PLGA) loaded with recombinant human bone morphogenetic protein 2 (rhBMP-2) on repairing articular cartilage defect in rabbits. Methods PLGA was made into cylinders which were 4 mm in diameter and 3 mm in thickness. rhBMP-2 was fully homogenated before used. PLGA combined with 0.5 mg rhBMP-2 under the condition of vacuum(700 mmHg),and then lyophilized, packed ,sterilized with ethylene oxide and reserved. Defects of 4 mm in diameter and reaching medullary cavity were made in femoral condyles of 72 two-month-old New Zealand white rabbits. The 36 right defects were repaired with PLGA-rhBMP-2 composites as the experimental group, the 36 left defects with PLGA only as PLGA group, the other 36 left defects were left untreated as control group, and the other 36 right defects with PLGA-MSCs composites as cell group. At 4, 8, 12, 24, 36 and 48 weeks after operation, macroscopical and microscopical observations were made, and the histological grade wasdone.Results After 4 weeks of operation: In the experimental group and cell group, defects were filled with white translucent tissue which appeared smooth and soft; the matrix around chondrocytes was weakly metachromatic, the newly formed cartilage tissue was thicker than normal cartilage tissue; there was no formed tissue in the PLGA group and the blank control group. After 8 weeks of operation: In the experimental group and cell group, the new tissue was white, translucent, tenacious and smooth. The boundary with normal cartilage became vague. New cartilage cells distributed evenly. The cells of the surface layerparalleled, but the deeper layer lost directivity. The matrix dyed weakly. The new cartilage gradually became thinner, but it still thicker than the normal cartilage ones. The PLGA degraded besides some drops.In the blank control group and PLGA group, a little white membrane formed at the bottom of the defect. After 1224 weeks of operation: In the experimental group and cell group, defects were filled with new tissues which were white, translucent, tenacious and smooth. The boundary disappeared.The thickness of the new cartilage was similar to that of the normal ones. The cells of the surface layer paralleled to each other,but the cells of the deeper layer tended to arrange vertically. The matrix around chondrocytes was metachromatic,but the color was lighter than that of the normal cartilage. Bone under the cartilage and the tide mark recovered. The new cartilage linked with nomal cartilage finely.In the blank control group and PLGA group, there was a little fibrous tissue at the bottom of the defect withe obvious boundary. After 36 weeks and 48 weeks of operation：in the experimental group and the cell group, the new cartilage was slightly white，continuous and less smooth. The boundary disappeared. There was no proliferated synovial membrane.The thickenss of the new cartilage was thinner than that of the normal ones. The matrix around chondrocytes was weakly metachromatic. In the blank control group and PLGA group, the defect still existed, but became smaller.At the bottom of the defect, fibrous tissues formed. Some cartilage denudated and became less smooth.Some bone under cartilage exposed,and the synovial membrane became thick. The histologic grade of the repair tissue at 12 weeks and 24 weeks of operation in experimental group and cell group was significantly different from that at 4, 8 and 48 weeks of operation(Plt;0.01). There was also significant difference in the experimental group and cell group compared with the blank control group and PLGA group at each time after operation(Plt;0.01). But there was no significant difference between the experimental group and the cell group. Conclusion In the course of degradation。。。。。。.