Involvement of cell-cell and cell-matrx adhesion molecules in chondroblastic and osteoblasticdifferentiation

本研究旨在探讨细胞外基质对软骨细胞和成骨细胞分化的调节机制。观察了大鼠气管和胫骨生长板软骨细胞肥大和基质钙化的过程，重点观察了X型胶原的表达。研究了大鼠胚胎下颌骨成骨过程中细胞外基质蛋白的表达。取新生至10周龄大鼠的气管和新生大鼠的胫骨固定，石蜡包埋，切片进行X型胶原免疫组织化学染色。12~19d大鼠胚胎头部固定，石蜡包埋，连续切片进行细胞外基质蛋白免疫组织化学染色。X型胶原在胫骨生长板肥大软骨细胞周围基质中表达，而在气管中不表达。14日龄大鼠胚胎下颌骨间充质细胞集合体中可见Tenascin和FN。15日龄大鼠胚胎下颌骨未钙化的骨基质中可识别出I型胶原和骨连接蛋白。16天胚胎下颌骨钙化骨基质中有骨桥蛋白、骨涎蛋白和骨钙素的表达。本研究提示：(1)X型胶原不参与大鼠气管软骨细胞肥大或基质钙化；(2)在大鼠胚胎下颌骨成骨过程中，细胞外基质蛋白以时间特异性的方式表达和积累。

The present study was designed to study the regulatory mechanism of the extracellular matrix on differentiation of chondrocytes and osteoblasts. The process of hypertrophization of chondrocytes and matrix calcification in rat tracheal and tibial growth plate cartilages was examined focusing on expression of type X collagen. The osteogenic process in rat embryonic mandibles was investigated focusing on expression of extracellular matrix proteins. Tracheas in new-born to 10-week old rats and tibiae in new-born rats were fixed, embedded in paraffin and the sections were processed for immunohistochemistry for type X collagen. Heads of rat embryos from 12 to 19 days in gestation were fixed, embedded in paraffin and the serial sections were processed for immunohistochemistry for extracellular matrix proteins. Type X collagen was expressed in the matrix around hypertrohic chondrocytes of the tibial growth plate, but not in the trachea. Tenascin and fibronectin were identified in the mesenchymal cell aggregation of mandibles in 14 day-rat embryos. Type I collagen and osteonectin were recognized in the uncalcified bone matrix in 15 day-rat embryonicmandibles. Osteopontin, bone sialoprotein and osteocalcin were expressed in the calcified bone matrix in 16 day-embryonic mandibles. The present studies suggested that (1) type X collagen is not involved in hypertrophization of chondrocytes or matrix calcification in the rat trachea and (2) extracellular matrix proteins are expressed and accumulated in a time specific manner during osteogenesis of the rat embryonic mandible.