Effects of Bisphosphonate on the Ossification of Growth Plate of the Knee Joint in Rats

Lee, Eun Joo; Kim, Hyun Jin; Lee, Gae Hyuk; Kim, Min Seok; Park, Ha Ok; Kim, Won Jae; Kim, Sunhun

Abstract

Bisphosphonates inhibit bone resorption by affecting osteoclastic function and formation of osteoclasts from their precursor cells. Chondroclasts have the same origin and differentiation as osteoclasts. Thus, it is hypothesized that bisphosphonate can affect on cartilage metabolism. This study was aimed to elucidate effects of alendronate, a nitrogen containing bisphosphonate, on cartilage development in the tibial proximal and femoral distal epiphyseal plates in rats. Alendronate (1 mg/kg) was subcutaneously administered in growing rat pups for 10 days. Several parameters such as the number and size of chondroclasts, involved in cartilage resorption, size of secondary ossification center and thickness of cartilage cell layers were measured and analysed by histomorphometry. The size of the secondary ossification centers in the tibial proximal and femoral distal epiphysis was smaller in the alendronate treated group (p< 0.01). The number of osteoclasts in the both the ossification centers and chondroclasts beneath the epiphyseal plates was significantly decreased by alendronate treatment (p< 0.01). The size of chondroclasts was not significantly changed (p> 0.05). The thickness of proliferating cartilage layer was not changed, but by contrast, hypertrophied cartilage layer was increased in thickness by alendronate treatment. These findings suggest that bisphosphonates can affect cartilage cell metabolism in a chondroprotective way.