Changes in leucine-rich repeat proteoglycans during maturation of the bovine growth plate

The primary growth plate of the fetal bovine tibia was studied in order to determine whether changes in the structure, abundance and expression of the leucine-rich repeat proteoglycans were occurring during tissue maturation from reserve cartilage to hypertrophic cartilage. The proteoglycans under s tudy were decorin, biglycan, fibromodulin and lumican. Decorin was readily detectable in both the reserve and proliferating zones of the growth plate, but its abundance decreased markedly in the zones of maturation and hypert rophy where it could not be detected under the same conditions of analysis. In contrast to decorin, fibromodulin and biglycan could be detected throug hout the growth plate, though their abundance was decreased in the prolifer ative and hypertrophic zones. Unlike the other proteoglycans, lumican could not be detected throughout the growth plate. At the message level, the exp ression of decorin shows a similar trend to that of protein abundance in th e extracellular matrix, with its expression dropping markedly in the prolif erative and hypertrophic zones. In the case of both biglycan and fibromodul in, message expression continued at a similar level throughout the growth p late. Thus, the leucine-rich repeat proteoglycans are different in the way they behave during growth plate maturation. (C) 2001 Elsevier Science B.V./ International Society of Matrix Biology. All rights reserved.