| Objective: To investigate the protective effect of calcitonin on articular cartilage and subchondral bone in rat model of experimental osteoarthritis made by anterior cruciate ligament transaction (ACLT).Methods: Forty rats were divided randomly into three groups: Sham(n=10), ACLT+CT(n=15) and ACLT+NS(n=15). Rats in ACLT+CT and ACLT+NS groups were given anterior cruciate ligament transection(ACLT)on the right knee. Rats in Sham group were given the same arthrotomy as pseudo operation control. ACLT+CT group began to receive a daily subcutaneous injection of salmon calcitonin at the dose of 10 IU/kg for 12 weeks; ACLT+NS group received NS at the same dose. All rats were sacrificed at the 12th week after the surgery. Double labeling was performed with subcutaneous injections of tetracylcin at the 11th day and of calcein at the 4th day before sacrificed. The decalcified right femora condyles were cut and stained with Masson, VG, immunohistochemistry of IL-1βand MMP-13.The general observation of the degeneration of the articular cartilage of femoral condyle,HE staining, safranin-O/fast green ,Masson and VG were observed under the dissecting microscope,and were graded by Mankin's scale; The bone mineral density of 1/4 of the distal portion of right femurs and the subchondral bone of internal and external side of femoral condyle was mearsured with the dual-energy X-ray absorptiometry scanner. Sclerous tissues of cancellated bone of right proximal tibia of rats were embedded, sliced, stained for observation of morphometry Parameters and were analyzed in image.Results: (1) The Sham group, ACLT+CT group and ACLT group exhibited OA development in the femoral condyles cartilage. Surfaces of knee joints of the Sham group were all smooth and glossy, and displayed light blue, synovial fluid was clear; Knee joints of ACLT+NS group swelled, and its surface were uneven or anabrotic, displayed dim and bloomy, synovial was light yellow and cloudy, their tibial plateaus appeared hypertrophic, osteophyte emerged on the margin, which was typical appearance of OA. In ACLT+CT group, articular surfaces were uneven and dim, but tibial plateau hypertrophy had not been seen, cartilage degradation were smaller than ACLT group. The Mankin score of the Sham and ACLT+CT group were apparently higher than the ACLT group (p<0.05). (2) The bone mineral density (BMD) of the distal right femora had no significant change between three groups. However, the BMD of the subchondral bone of ACLT+CT group were lower than ACLT+NS group (p<0.05). In the index of the Bone histomorphometry of the ACLT+CT group were obviously better than ACLT+NS group (p<0.05). The static index of Bone Histomorphometry: trabecular bone volume (BV/TV), trabecular separation (Tb. N) showed in Sham and ACLT+CT groups were significantly higher than that in ACLT+NS group. However, trabecular bone thickness (Tb.Th) and trabecular separation (Tb.Sp) in Sham and ACLT+CT groups were significantly higher than ACLT+NS group. In the dynamic index, the percent labeled perimeter (%L.Pm), osteoclast number (Oc.N), mineral apposition rate (MAR), Osteoid Perimeter(O.Pm) and Osteoclast Number(Oc.N) of Sham and ACLT+CT groups showed significant lower than ACLT+NS group (p<0.05)(.3) In ACLT+CT group, gene expression levels of IL-1βand MMP-13 were significantly lower than ACLT+NS group (p<0.05).Conclusion: A daily subcutaneous injection of salmon calcitonin at a dose of 10IU/kg for 12 weeks probably protect articular cartilage and subchondral bone. The calcitonin may be prospectively used for the treatment of OA. |
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