XBP1s gene of endoplasmic reticulum stress enhances proliferation and osteogenesis of human periodontal ligament cells.

BACKGROUND: The endoplasmic reticulum stress (ERS) pathway, inositol-requiring enzyme-1 alpha-X-box binding protein-1 (IRE1α-XBP1), has been considered as a critical factor of human periodontal ligament cells (hPDLCs) in proliferation and osteogenesis. This study aimed to explore the effect and mechanism of XBP1s, which was cleaved by IRE1α on the proliferation and osteogenesis of hPDLCs. METHODS: ERS model was induced by tunicamycin (TM); cell proliferation was assessed by CCK-8 assay; pLVX-XBP1s-hPDLCs cell line was established by lentivirus infaction; expression of ERS-related protein including eIF2α, GRP78, ATF4 and XBP1s, autophagy-related P62 and LC3, and apoptosis-related Bcl-2 and Caspase-3 were detected by Western Blot; expression of osteogenic genes was detected by RT-qPCR, and senescence of hPDLCs was explored by ß-galactosidase staining. Furthermore, the interaction between XBP1s and human bone morphogenetic protein 2 (BMP2) was examined by immunofluorescence antibody test (IFAT). RESULTS: The results showed an increase in proliferation of hPDLCs from 0 to 24 h when ERS was induced by TM treatment (P < 0.05). XBP1s overexpression induced hPDLCs proliferation, upgraded autophagy and degraded apoptosis significantly (P < 0.05). In pLVX-XBP1s-hPDLCs, the ratio of senescent cells was markedly decreased after several passages (P < 0.05); After infection with pLVX-BMP2 lentiviral supernatant, IFAT result showed that XBP1s and BMP2 well co-located in the cytoplasm of pLVX-XBP1s-hPDLCs and PERK-ATF4 ERS branch was activated, meanwhile, there were obviously more mineralized nodules and mRNA expression of osteogenesis-related genes was continually up-regulated (P < 0.05). CONCLUSIONS: XBP1s promotes the proliferation via regulating the autophagy and apoptosis, and enhances expression of osteogenic genes in hPDLCs. The mechanisms in this regard need exploring further for periodontal tissue regeneration, functionalization and clinical applications.

Regulation of proliferation and apoptosis of aging periodontal ligament cells by autophagy-related gene 7.

BACKGROUND: Human periodontal ligament cells (hPDLCs) can be applied in periodontal regeneration engineering to repair the tissue defects related to periodontitis. Theoretically, it can affect the vitality of hPDLCs that cell aging increases apoptosis and decreases autophagy. Autophagy is a highly conserved degradation mechanism, which degrades the aging and damaged intracellular organelles through autophagy lysosomes to maintain normal intracellular homeostasis. Meanwhile, autophagy-related gene 7 (ATG7) is a key gene that regulates the level of cellular autophagy. OBJECTIVE: This study was to explore the effects of autophagic regulation of aging hPDLCs on cell proliferation and cell apoptosis. METHODS: A cell model of aging hPDLCs overexpressing and silencing ATG7 were respectively constructed by lentiviral vectors in vitro. A series of experiments was performed to confirm relevant senescence phenotype on aging hPDLCs, and to detect the effects of changes in autophagy on their proliferation and apoptosis-related factors in aging hPDLCs. RESULTS: The results showed that overexpression of ATG7 could motivate autophagy, promoting proliferation of aging hPDLCs and inhibiting apoptosis synchronously (P < 0.05). On the contrary, suppressing autophagy levels by silencing ATG7 would inhibit cell proliferation and accelerate cell senescence (P < 0.05). CONCLUSION: ATG7 regulates the proliferation and apoptosis of aging hPDLCs. Hence, autophagy may act as a target to delay senescence of hPDLCs, which can be helpful in the future in-depth study on regeneration and functionalization of periodontal supporting tissues.