To investigate both prophylactic and therapeutic roles of salmon calcitonin on the articular cartilage of rabbit's knees.
Right knee instability was produced in 30 New Zealand white rabbits by sectioning the cranial cruciate ligament (CCL). Animals were separated into four groups: placebo prophylactic-stage group (n=6), killed 8 weeks post surgery, calcitonin prophylactic-stage group (n=6), treated immediately after surgery with salmon calcitonin and killed at 8 weeks, placebo therapeutic-stage group (n=9) killed at 16 weeks post surgery and calcitonin therapeutic-stage group (n=9), treated with salmon calcitonin from 8th to 16th week and killed at 16 weeks post surgery. A histomorphometric study was based on the morphological changes of the articular cartilage and subchondral bone (degeneration indexes), as well as the articular cartilage thickness, chondrocytes' arrangement and their metabolic activity (regeneration indexes).
Calcitonin groups showed smoother articular surface, no or minimal signs of ulceration, smaller osteophytes, and less subchondral cystic formation than placebo groups. Normal distribution of chondrocytes or hypercellularity was noticed in areas of mild osteoarthritic (OA) changes in the calcitonin groups indicating regeneration activity. Periodic Acid Schiff's and Alcian blue staining were negative in the placebo groups while increased absorption in the calcitonin groups revealed high anabolic activity.
In prophylactic stages salmon calcitonin seemed to inhibit the progression of osteoarthritis by increasing the layers of hyaline cartilage, restoring the cellular metabolism, and decreasing the volume of osteophytes. In therapeutic stages, the hormone had a healing effect by decreasing the subchondral cysts, regenerating the hyaline cartilage and restoring cellular metabolism. Both macroscopic and histological findings of this study supported the biochemical results of previous studies showing the therapeutic effect of calcitonin on osteoarthritis.