[Experimental study of repairing full-thickness articular cartilage defect with chondrocyte-sodium alginate...

To explore the effect of tissue engineered cartilage reconstructed by using sodium alginate hydrogel and SIS complex as scaffold material and chondrocyte as seed cell on the repair of full-thickness articular cartilage defects.

SIS was prepared by custom-made machine and detergent-enzyme treatment. Full-thickness articular cartilage of loading surface of the humeral head and the femoral condyle obtained from 8 New Zealand white rabbits (2-3 weeks old) was used to culture chondrocytes in vitro. Rabbit chondrocytes at passage 4 cultured by conventional multiplication method were diluted by sodium alginate to (5-7) x 10(7) cells/mL, and then were coated on SIS to prepare chondrocyte-sodium alginate hydrogel-SIS complex. Forty 6-month-old clean grade New Zealand white rabbits weighing 3.0-3.5 kg were randomized into two groups according to different operative methods (n = 20 rabbits per group), and full-thickness cartilage defect model of the unilateral knee joint (right or left) was established in every rabbit. In experimental group, the complex was implanted into the defect layer by layer to construct tissue engineered cartilage, and SIS membrane was coated on the surface to fill the defect completely. While in control group, the cartilage defect was filled by sodium alginate hydrogel and was sutured after being coated with SIS membrane without seeding of chondrocyte. General condition of the rabbits after operation was observed. The rabbits in two groups were killed 1, 3, 5, 7, and 9 months after operation, and underwent gross and histology observation.

Eight rabbits were excluded due to anesthesia death, wound infection and diarrhea death. Sixteen rabbits per group were included in the experiment, and 3, 3, 3, 3, and 4 rabbits from each group were randomly selected and killed 1, 3, 5, 7, and 9 months after operation, respectively. Gross observation and histology Masson trichrome staining: in the experimental group, SIS on the surface of the implant was fused with the host tissue, and the interface between them disappeared 1 month after operation; part of the implant was chondrified and the interface between the implant and the host tissue was fused 3 months after operation; the implant turned into fibrocartilage 5 months after operation; fiber arrangement of the cartilage in the implant was close to that of the host tissue 7 months after operation; cartilage fiber in the implant arranged disorderly and active cell metabolism and proliferation were evident 9 months after operation. While in the control group, no repair of the defect was observed 9 months after operation. No obvious repair was evident in the defects of the control group within 9 months after operation. Histomorphometric evaluation demonstrated that the staining intensity per unit area of the reparative tissue in the defect of the experimental group was significant higher than that of the control group at each time point (P < 0.05), the chondrification in the experimental group was increased gradually within 3, 5, and 7 months after operation (P < 0.05), and it was decreased 9 months after operation comparing with the value at 7 months after operation (P < 0.05).

Constructed by chondrocyte-sodium alginate hydrogel-SIS in complex with surficial suturing of SIS membrane, the tissue engineered cartilage can in-situ repair cartilage defect, promote the regeneration of cartilage tissue, and is in line with physiological repair process of articular cartilage.