Integrins and Extracellular Matrix Proteins in the Human Childhood and Adolescent Growth Plate

Abstract

Interaction of chondrocytes with the surrounding matrix significantly influences differentiation and growth. These processes involve cell surface proteins, particularly integrins. The aim of this study was to compare the expression of integrins (a1, a2, a3, a5, a6, av, b1, b3, and b5 subunits) together with matching binding proteins in human childhood and adolescent growth plate cartilage using immunohistochemistry. Integrin b1 was detected in all chondrocytes of the growth plate cartilage, b3 only in osteoclasts of the opening zone, and b5 in hypertrophic chondrocytes and osteoblasts. Integrin a1, a2, and a5 subunits were expressed by chondrocytes in the proliferative and hypertrophic zone as well as in osteoblasts and osteoclasts. Integrin av and a6 subunits were present in chondrocytes of all zones, a3 only in osteoclasts. Collagen type II and fibronectin were seen throughout the growth plate, collagen type X in the hypertrophic zone, collagen type I in the ossifying trabecules. Laminin was expressed by chondrocytes in the resting zone and more weakly in the proliferative zone, collagen VI was present in the pericellular and interterritorial matrix in all zones of the growth plate. These results differ from previous reports on the distribution of integrins in the fetal growth plate. However, there was no difference in integrin expression in children before and during puberty. Our results indicate that integrin expression is not influenced by endocrine factors during sexual maturation and suggest that the process of skeletal maturation is not regulated via altered integrin expression.