Search

Matrix metalloproteinases (MMPs) 8 and 13 comprise the collagenase subfamily in rats and mice, and only MMP13 has been implicated in degradation of the collagenous matrices during development of bone and cartilage. On the hypothesis that MMP8 is also involved in bone and cartilage development, the present study was designed to investigate gene expression of MMP8 in rat embryonic mandibles and hind limbs. Expression of MMP8 was examined with in situ hybridization and RT-PCR and was compared with that of MMP13. Osteoblastic and chondrocytic cells expressing collagenous matrix molecules were identified using in situ hybridization for collagen Types I and II. The results demonstrated that MMP8 is expressed by osteoblastic progenitors, differentiated osteoblasts, osteocytes, and chondrocytes in the growth plate for the first time. Furthermore, the expression of MMP8 is much broader than that of MMP13, for which expression is confined to differentiated phenotypes of osteoblastic and chondrocytic lineage.

The present study was designed to investigate how rat hyaline cartilagesat various sites in vivo express the gene and protein of type I collagen using in situ hybridization and immunohistochemistry. The gene of pro alpha1(I) collagen was expressed by chondrocytes in articular cartilage, and theprotein of type I collagen was identified in the cartilage matrix. In contrast,growth plate cartilage expressed the gene of pro alpha 1(I) collagen, butno protein of type I collagen. Neither gene nor protein of type I collagenwas expressed in cartilages of trachea and nasal septum. The present studysuggested that expression of type I collagen in hyaline cartilages may beregulated tissue-specifically at gene and/or protein levels. [ABSTRACT FROM AUTHOR]