Objective: To investigate the effect of allogeneic chondrocytes-calcium alginate gel composite under the intervention of low intensive pulsed ultrasound (LIPUS) for repairing rabbit articular cartilage defects.
Methods: Bilateral knee articular cartilage were harvested from 8 2-week-old New Zealand white rabbits to separate the chondrocytes by mechanical-collagen type II enzyme digestion. The 3rd passage chondrocytes were diluted by 1.2% sodium alginate to 5 x 10(6) cells/mL, then mixed with CaCl2 solution to prepare chondrocytes-calcium alginate gel composite, which was treated with LIPUS for 3 days (F0: 1 MHz; PRF: 1 kHz; Amp: 60 mW/cm2; Cycle: 50; Time: 20 minutes). An articular cartilage defect of 3 mm in diameter and 3 mm in thickness was established in both knees of 18 New Zealand white rabbits (aged 28-35 weeks; weighing, 2.1-2.8 kg), and divided into 3 groups randomly, 6 rabbits in each group: LIPUS group, common group, and model group. Defect was repaired with LIPUS-intervention gel composite, non LIPUS-intervention gel composite in LIPUS group and common group, respectively; defect was not treated in the model group. The general condition of rabbits was observed after operation. The repair effect was evaluated by gross and histological observations, immunohistochemical staining, and Wakitani score at 8 and 12 weeks after operation.
Results: Defect was filled with hyaline chondroid tissue and white chondroid tissue in LIPUS and common groups, respectively. LIPUS group was better than common group in the surface smooth degree and the degree of integration with surrounding tissue. Defect was repaired slowly, and the new tissue had poor elasticity in model group. Histological observation and Wakitani score showed that LIPUS group had better repair than common group at 8 and 12 weeks after operation; the repair effect of the 2 groups was significantly better than that of model group (P < 0.05); and significant differences in repair effect were found between at 8 and 12 weeks in LIPUS and common groups (P < 0.05). The collagen type II positive expression area and absorbance (A) value of LIPUS and common groups were significantly higher than those of model group (P < 0.05) at 8 and 12 weeks after operation, and the expression of LIPUS group was superior to that of common group at 12 weeks (P < 0.05); and significant differences were found between at 8 and 12 weeks in LIPUS group (P < 0.05), but no significant difference between 2 time points in common and model groups (P > 0.05).
Conclusion: Allogeneic chondrocytes-calcium alginate gel composite can effectively repair articular cartilage defect. The effect of LIPUS optimized allogeneic chondrocytes-calcium alginate gel composite is better.