Molecular biological study on the physiologic function of periodntal ligament of human deciduous tooth

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The expression of mRNA of osteoprotegerin(OPG), receptor activator nuclear kappa B ligand(RANKL) and macrophage colony stimulating factor(M-CSF) was investigated by RT-PCR on the cultured cells derived from periodontal ligament of human deciduous teeth(HPLF-D) and permanent teeth(HPLF-P), alveolar bone process(hOB) and gingival fibroblast(hGF). All of the cultured cells express mRNA of OPG at almost same level. The expression of M-CSF mRNA was also observed on all types of the cells. The mRNA level of secreted form of M-CSF was dominant compared to membrane-bound form. On the other hand, the expression of RANKL message was observed on HPLF-D, HPLF-P and hOB, excepted on hGF. However, the level of RANKL mRNA on HPLF-D was almost same level of hOB and it was higher than that on HPLF-P. The level of RANKL message was increased by the addition of 1 α,25 dihydroxyvitamin D_3(D_3) in dose dependent manner.These data suggested as follows1)The cells in periodontal tissues express a considerable level of mRNA of M-CSF and OPG, those are able to regulate osteoclast differentiation.2)RANKL, which is produced by osteoblasts or HPLF, is the most important factor on osteoclast differentiation in periodontal tissues.3)The level of RANKL mRNA increased by the factors playing important roll on bone metabolism (for example, D_3) is able to induce the differentiation of osteoclasts (or odontoclasts).4)Bone resorbing factors affect the cells in periodontal ligament of deciduous tooth on inducing the differentiation of osteoclst (or odontoclast), and the effect is greater than that on periodontal ligament of permanent tooth.