ZONAL VARIATIONS OF TYPE-II, TYPE-IX AND TYPE-XI COLLAGEN MESSENGER-RNAS IN RAT EPIPHYSEAL CARTILAGE CHONDROCYTES - QUANTITATIVE-EVALUATIONOF IN-SITU HYBRIDIZATION BY IMAGE-ANALYSIS OF AUTORADIOGRAPHY

The spatial-temporal distribution of the mRNAs for type TX and type XI collagens were compared to that of type II collagen mRNA in the tibia l epiphyseal plate cartilage of normal growing rats. The mRNAs were de tected by in situ hybridization with radio-labelled specific probes an d visualized by radioautography. The areas covered by the resulting si lver grains were quantified by computer assisted image analysis. The a reas in chondrocytes of each zone of the epiphyseal plate cartilage, w hich correspond to the stages of chondrocyte development and function were determined. Types II, IX and XI mRNAs were present to some extent in chondrocytes of all zones. The distribution of type II and type IX collagen mRNAs were similar with the highest concentrations in the pr oliferative zone, and the lowest in the resting and calcifying zones c hondrocytes. In contrast, type XI collagen mRNA had a different distri bution, with the lowest concentration in the resting zone chondrocytes and a significant decrease in the calcifying zone chondrocytes. These patterns correlates with the changes in chondrocyte function, and map reflect the roles of the type IX and type XI collagens. The data show that computer assisted image analysis of in situ hybridization radioa utograhic images is a precise, rapid tool for analysing differences in gene expression.