치주인대, 이틀뼈 및 시멘트질의 발생과정에서 치주인대-특이 유전자 PDLs22의 발현

Abstract

치주인대(periodontal ligament)는 치아를 지지할 뿐만 아니라 인접 이틀뼈 및 시멘트질의 수복과 재생에 관여하는 것으로 알려져 있으나, 치주인대 세포의 발생과 분화에 선택적으로 관여하는 유전자에 대한 연구는 미미한 실정이다. 치주인대 세포의 분화와 뼈와 시멘트질의 형성과정에서 치주인대-특이 유전자인 PDLs22의 명확한 기능을 알아보기 위하여 배양 치주인대 세포의 분화 과정에서 PDLs22, osteonectin과 osteocalcin mRNA 발현을 RT-PCR법으로 비교하였고, PDLs22에 대한 항체를 제작한 후 흰쥐 치아와 치주조직 발생과정에서 PDLs22 단백질의 분포를 면역조직화학적으로 확인하였다. 치주인대 세포들은 배양 14일째에 석회화 결절을 형성하였고, 세포의 배양과정에서 osteocalcin mRNA는 배양 초기부터 발현되어 배양 기간 동안에 강하게 발현되었으며, osteonectin PDLs22 mRNA는 배양 초기부터 발현되었으나 석회화 결절이 형성되면서 발현이 감소되었다. 면역조직화학적 염색소견에서 PDLs22단백질은 치아관 형성시기의 바깥치아상피와 별그물에서 발현되기 시작하여 HERS(Hertwig's epithelial root sheath)의 바깥치아상피로 이어진 다음 치주인대, 이틀뼈 및 시멘트질을 형성하기 위한 전구세포에서 강하게 발현되었다. 이상의 결과를 종합하면 치주인대-특이 유전자 PDL22는 치주조직 발생에 있어 상피-간엽간의 중요한 매개물질로 작용하며, 뼈와 시멘트질의 초기 형성과정에 중요한 역할을 하는 것으로 생각된다

Identifying specific factors and/or mechanism regulating development of periodontal tissue will provide important information at to which molecules and cells are required for regulation of periodontal tissue lost as a consequence of disease. The origin and location of cementoblast and osteoblast precursor cells in adult periodontal tissues is not definitely known but it has been suggested that tooth related periodontal ligament may be the source of cementoblasts and the bone-related periodontal ligament for osteoblasts. However, little is known of the molecular mechanism controlling PDL function. PDL-specific protein; PDLs22 had been previously identified as a novel protein isolated from cultured human PDL fibroblasts using subtraction hybridization between human gingival fibroblasts and PDL fibroblasts. The aim of this study was to examine the functional characterization of PDLs22 in differentiation of periodontal ligament. alveolar bone and cementum. Human osteocalcin (OC), osteonectin(ON) and PDLs22 mRNA were detected by reverse transcription polymerase chain reaction (RT-PCR) in primary cell cultures of periodontal ligament fibroblast during mineral nodule formation in vitro. And the localization of PDLs22 in rat tissues was detected by polyclonal antibody against PDLs22 by means of immunohistochemical staining. The results were as follows: 1. PDL celIs were capable of producing mineral-like nodules in vitro. 2. PDLs22 mRNA was expressed in the initial stages whereas it was not expressed in the calcification stage, during mineral nodule formation of PDL cells in vitro. 3. PDLs22 protein was expressed in external dental epithelium and stellate reticulum during crown formation stage, and was continued in external dental epithelium of Hertwig's epithelial sheath Also PDLs22 protein was strongly expressed in the bone and cementum-related side of the PDL and weakly expressed in the middle of PDL. In the developing bone, PDLs22 protein is only expressed in preosteoblast not osteocyte and osteoblast. The results suggest PDLs22 is important mediator of epithelial-mesenchymal reaction in development of PDL. alveolar bone and cementum and is related to initial differentiation of cementum and alveolar bone.