Effect of colchicine on the endochondral ossification of the epiphyseal cartilage of rat tibia.

Abstract

A histological study and an autoradiographic study using tritiated thymidine were carried out to investigate the effect of colchicine on the epiphyseal growth cartilage of rat tibia, especially in relation to the function of microtubules.Intravenous injection of colchicine (1.0 mg/l;kg) thickened the growth plate during the period from 3 to 5 days after administration. This was mainly due to an increase in number of hypertrophied chondrocytes. During the same period, the osteoblasts and the osteoclasts were detached from the trabecular bone at the junction of growth plate and metaphysis. The invasion of capillaries to the open end lacunae of the growth plate decreased remarkably (P>0.01). Appearance of thin trabecular bones in the metaphysis was noted.Autoradiographic study showed that following a decrease in number of labeled proliferative chondrocytes during the period from 2 to 8 hours after the colchicine administration, the number of labeled chondrocytes increased remarkably (P>0.01). Labeled osteoprogenitor cells at the junction of growth plate and metaphysis decreased (P>0.01) at 3-5 days after colchicine administration.At 6-10 days after administration, the thickness of the growth plate began to decrease with continuous erosion of the calcified cartilage septa. The invasion of capillaries to the growth plate was restored gradually and then osteoblasts and osteoclasts reappeared on the surface of spongiosa. The number of labeled osteoprogenitor cells and proliferative chondrocytes returned to a normal level.These results suggest that colchicine treatment induced the synchronization of mitosis of proliferative chondrocytes in the growth plate. At the same time, colchicine treatment retarded the erosion of calcified cartilage matrix at the junction of growth plate and metaphysis and reduced the bone remodeling process of pongiosa which may have caused the increase in thickness of the growth plate.These actions of colchicine may be closely related to the inhibition of microtubular function of cells engaged in the process of endochondral ossification. Introduction Endochondral ossification