CHONDROADHERIN EXPRESSION CHANGES IN SKELETAL DEVELOPMENT

Chondroadherin is a cartilage protein with cell binding properties. Th e expression of chondroadherin was studied in rat tissues and during p ostnatal femoral head development. For design of oligonucleotide probe s and primers a 1664 bp, full length, rat chondroadherin cDNA was isol ated from a rat chondrosarcoma library and sequenced. Northern blot an alysis showed chondroadherin mRNA to be present in femoral head and ri b cartilage, as well as in tendon. More sensitive reverse-transcriptas e PCR additionally identified the mRNA. in calvaria, long bone and bon e marrow. Localization of chondroadherin by immunocytochemistry in the developing femoral head from postnatal day 14 to day 60 showed presen ce of the protein in cartilaginous regions. With increasing age a very distinct localization of chondroadherin was seen in the territorial m atrix around late proliferative cells in the growth plate as well as i n the developing articular cartilage in the maturing femoral head. Loc alization of chondroadherin mRNA by in situ hybridization was in agree ment with immunocytochemistry with strong hybridization signals in lat e proliferative cells in the growth plate. In the articular cartilage the expression was restricted to cells in the lower regions. A three-f old increase of cartilage chondroadherin content in the growing femora l head was demonstrated by Western blot analysis. The high expression of this cell binding protein in a dynamic region of cartilage suggests an important role for chondroadherin in the regulation of chondrocyte growth and proliferation.