Expression of matrix metalloproteinases during vascularization and ossification of normal and impaired avian growth plate

¹ Department of Biochemistry and Nutrition, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University, Israel
² Department of Cell Biology and Physiology, Washington University, St. Louis, USA
³ Institute of Animal Science, the Volcani Center, Bet Dagan, Israel

^* To whom correspondence should be addressed. E-mail: ornanme{at}agri.huji.ac.il.

	Abstract

Enzymes of the matrix metalloproteinase (MMP) family regulate angiogenesis and are involved in the endochondral ossification process. Tibial dyschondroplasia (TD) and rickets are 2 disorders associated with impairments in this process, mainly in the vascularization of the avian growth plate. In this paper, we induced TD and rickets and studied the expression patterns of four members of the MMP family known to be important for endochondral ossification, MMP-2, 3, 9, and 13, in normal and impaired avian growth plates. The expression of MMP-3, 9 and 13 was reduced in the lesions and lined up parallel to the expulsion of blood vessels, which was extended up to the border of the lesion, but did not penetrate into it. Matrix metalloproteinase-2 was not expressed in the TD lesion but was overexpressed in the rachitic lesion. We also studied the differentiation stage of the chondrocytes populating the lesions and found that the rachitic lesion were populated with proliferative chondrocytes whereas the TD lesions were filled with chondrocytes that present both proliferative and hypertrophic markers. These results suggest that MMP-3, 9, and 13 play a role in vascularization and ossification processes, while MMP-2 is related to chondrocyte differentiation and may be involved in cartilage remodeling in the avian growth plate.

Key Words: chondrocyte, rickets, tibial dyschondroplasia