The Distribution of Collagen I,II,X and Alkaline Phosphatase in the Development of Condylar Cartilage of Fetal Mouse Mandible

Objective The purpose of this study was to investigate the distribution of collagenⅠ,Ⅱ,Ⅹ,alkaline phosphatase(ALP) and their roles during initiation of condylar cartilage of the fetal mouse. Methods Coronary sections of mandible of mouse embryo aged from 14+{th} to 18+{th} day were studied under light microscope after stained by immunohistochemical method with antibody of typesⅠ,Ⅱ,Ⅹcollagen and ALP.Results On the 14th day of mouse embryo, it was found that mesenchymal cells condensation continuous with the periosteum. TypeⅠcollagen and ALP were positive behind the terminal of the ossifying mandibular periosteum where future condylar will form. On the 15th day, positive staining for typesⅠ,Ⅱ collagen was found in mesenchymal cells around hypertrophic cells and typeⅩcollagen was detected in hypertrophic cells. ALP was positive in both mesenchymal cells and hypertrophic cells. On the 16th day, typeⅠcollagen was observed from periosteal osteogenic cells and mesenchymal cells of the fibrous cell layer to the upper hypertrophic cell layer while TypeⅡcollagen was restricted from the lower polymorphic cell layer to the bottom of the hypertropic cell layer. TypeⅩcollagen was positive in the hypertrophic cell layer. ALP was positive in periosteal osteogenic cells and hypertrophic chondral cells, but not in the polymorphic cell layer.Conclusion Development of condylar cartilage is different from that of limb bone. TypesⅠ,Ⅱ,Ⅹcollagen are expressed in the condylar chondrocyte on the early stage of endochondral ossification. The histology evidence supports the conjecture that condylar cartilage is derived from differentiated mesenchymal cells of the preperiosteum or periosteum of the mandible where ALP is positively expressed.