Effect Of PELP1on Proliferation And Osteogenic Differentiation Of Periodontal Ligament Fibroblast Cells

The periodontal ligament (PDL) is the connective tissue located between alveolarbone and root surface of tooth. PDL is prone to osteoprosis, mainly for alveolar bone hightand bone density decrease, leading to loose teeth and shedding a direct impact onperiodontal organization health and oral treatment. Cells of PDL exhibit osteoblast-likefeatures and are capable of differentiating into osteoblasts or cementoblasts. They play animportant role in maintaining the integrity of the periodontal tissue.Estrogen plays an important role in PDL tissue which expresses estrogen receptor αand β. It has been shown that estrogen stimulates osteogenic differentiation in PDLFCsand co-treatment with growth factors enhances bone formation of PDLFCs. Lowerestrogen level increased the number of osteoclasts, causing the reduction of alveolar bonedensity. Higher estrogen level decreased the number of osteoclasts, increased bone density.The experiment showed that, estrogen receptor expression was significantly decreased inperiodontal disease model in rats. Estrogen receptor inhibition significantly reducedperiodontal ligament cells osteogenic differentiation capacity.The complex of estrogen-ER works through cell signal pathways which are highlydependent on and regulated by coregulatory proteins. These proteins are also called coregulators. The newly studied ER coregulator is praline-, glutamic acid-, andleucine-rich protein1(PELP1). PELP1is expressed in a wide variety of estrogen targettissues, with the highest levels of expression in the brain, mammary gland, ovaries anduterus. In many tissues, PELP1has been shown to reside in both nucleus and cytoplasm.PELP1acts as an important protein that integrates nuclear receptors (NRs) action inregulation of cell signaling pathway including genomic and non-genomic pathways.We hypothesized that, as regulator of estrogen, PELP1may participate in theosteogenic differentiation of PDLFCs through regulating their function. The aim of thisstudy is to investigate the role of PELP1during PDLFCs growth and osteogenicdifferentiation.1PELP1expression in rat PDLtissue and its influencing factorsUsing immunohistochemistry and RT-PCR methods to detect PELP1expression inrat periodontal tissue expression and the role of gender, age and estrogen levels on itsexpression, as a result we found that①the expression level of PELP1seemed to beunrelated with sex;②the expression level of PELP1could be affected by age;③theexpression level of PELP1changed with different estrogen levels.2PELP1expression in rPDLFCs and related to cell proliferation and osteogenicdifferentiationRT-PCR, immunohistochemistry and Western blot methods were used to detectPELP1expression in rat periodontal ligament fibroblast cells (rPDLFCs) and the effect ofPELP1on proliferation and osteogenic differentiation of rPDLFCs. RT-PCR and Westernblot were used to detect the PELP1expression in rPDLFCs-siPELP1.We observed that①PELP1expressed in rPDLFCs;②PELP1expression increased with rPDLFCs growth andproliferation;③PELP1expression increased after rPDLFCs osteo-induction;④ALP andOCN expression decreased in rPDLFCs-siPELP1after osteo-induction.3PELP1expression in I-hPDLFCs and related to cell proliferation and osteogenicdifferentiationhPDLFCs were cultured and identified by immunocytochemistry. RT-PCR andWestern blot were performed to detect PELP1expression on proliferation and osteogenicdifferentiation.The results showed that①PELP1was expressed in both H-hPDLFCs andI-hPDLFCs;②Compared with PELP1expression in H-hPDLFCs, the PELP1level ofI-hPDLFCs decreased with culture time;③During osteogenic induction, the PELP1 expression in I-hPDLFCs was decreased with culture time, and similar with the expressionof the osteogenic marker osteocalcin.In summary, this study aimed to investigate the effect of PELP1on proliferation andosteogenic differentiation of PDLFCs. For the first time, we showed that PELP1expressedin both rat and human PDLFCs and played a role in PDLFCs’proliferation and osteogenicdifferentiation.