IMMUNOHISTOCHEMICAL LOCALIZATION OF PARATHYROID HORMONE-RELATED PROTEIN IN DEVELOPING MOUSE MECKELS CARTILAGE AND MANDIBLE

In order to clarify the role of parathyroid hormone-related protein (P THrP) during Meckel's cartilage and mandibular development, an immunoh istochemical study of PTHrP and its receptor, PTH/PTHrP receptor, was designed to examine their localization in the anterior region of Mecke l's cartilage including the rostrum, which is known to contribute to t he development of the mandible. Meckel's cartilage was first observed on day 13 of gestation and PTHrP was faintly localized in the chondroc ytes. bn day 16 of gestation, at the stage of elongation and initiatio n of endochondral ossification in Meckel's cartilage, PTHrP was locali zed in the chondrocytes located in the area showing interstitial growt h and in and around the nuclei of hypertrophic chondrocytes undergoing endochondral ossification. At day 18 of gestation, endochondral ossif ication was spread over the entire area proximal to the molar region i n Meckel's cartilage, except in the mesial fusion site formed by immat ure chondrocytes. PTHrP was localized in the osteoblasts adjacent to t he calcified matrix, but had disappeared from the chondrocytes forming Meckel's cartilage. The localization of PTH/PTHrP receptor was simila r to that of PTHrP. These results show that localization of PTHrP is s patially and temporally related to the growth of Meckel's cartilage. ( C) 1997 Elsevier Science Ltd. All rights reserved.