BMP Receptors in Human Periodontal Cells

Introduction and Objectives: Bone morphogenetic proteins (BMP) are potent growth factors which play a major part in the re-building of many tissues, including the periodontium. The BMP exert their biological functions by signal transduction via 3 BMP receptors (BMPR), designated BMPR-IA, BMPR-IB and BMPR-II. Since these 3 polypeptides thus determine the response of target cells to endogenously produced BMP and BMP applied for therapeutic purposes, the aims of this study were to measure and compare the relative expression of BMPR-IA, BMPR-IB and BMPR-II in periodontal cells. Methods: The reverse transcriptase-polymerase chain reaction (RT-PCR) and a cell-enzyme-linked immunoabsorbent assay (C-ELISA) were used to measure the relative levels of BMPR-IA, -IB and -II mRNA and protein, respectively, in human alveolar bone, periodontal ligament and gingival fibroblast cells. Results: Transcripts for the 3 BMPR genes were found to be expressed by all the periodontal cells, although the relative levels differed markedly. Thus, while the bone cells produced low levels of BMPR-IA mRNA, they had significantly greater amounts of BMPR-IB and BMPR-II transcripts compared with the periodontal ligament cells and gingival fibroblasts. Moreover, the amounts of BMPR-IB transcripts in the latter 2 soft tissue-derived cells were substantially different, but they nevertheless expressed very similar levels of BMPR-II mRNA. In addition, a C-ELISA technique was developed which demonstrated, for the first time, that the corresponding proteins were also expressed, but at different relative levels by each particular cell type. Conclusion: These results show that the different BMPR mRNA transcripts and, most importantly for BMP function, the corresponding BMPR antigens, are expressed at different levels by the different periodontal cells in vitro, suggesting that these cells are likely to have unique and selective responses in BMP-induced periodontal regeneration. This study was supported by The Royal Thai Government Scholarship and the UCL Graduate School Student Conference Fund.