Objective: To detect the expression of mitofusion-1(Mfn1) in periodontal ligament stem cells (PDLSCs) isolated from healthy and periodontitis tissue and to study the effect of Mfn1 on the osteogenic differentiation of PDLSCs. Methods: PDLSCs were isolated from the healthy and periodontitis human samples(H-PDLSCs and P-PDLSCs). IL-1β was applied to mimic the inflammation microenvironment(H-PDLSCs + IL-1β). RT-PCR was used to detect the expression of Mfn1 in HPDLSCs, P-PDLSCs and H-PDLSCs + IL-1β. The expression of Mfn1 in P-PDLSCs was down-regulated by siRNA of Mfn1 (siMfn1). The osteogenic differentiation of the cells was examined by RT-PCR, alizarin red staining and cetyl pyridine chloride quantitative analysis. Results: The expression level of Mfn1 in P-PDLSCs and H-PDLSCs + IL-1β (5 μg/ml) groups was higher than that in H-PDLSCs(P＜ 0. 05). When the expression of Mfn1 in P-PDLSCs was down-regulated by siMfn1 the osteogenic differentiation ability of P-PDSLCs was restored(P＜ 0. 05). Conclusion: Inflammation may promote Mfn1 expression in PDLSCs and inhibite the osteogenic differentiation of P-PDLSCs.

The teeth are highly differentiated chewing organs formed by the development of tooth germ tissue located in the jaw and consist of the enamel, dentin, cementum, pulp, and periodontal tissue. Moreover, the teeth have a complicated regulatory mechanism, special histologic origin, diverse structure, and important function in mastication, articulation, and aesthetics. These characteristics, to a certain extent, greatly complicate the research in tooth regeneration. Recently, new ideas for tooth and tissue regeneration have begun to appear with rapid developments in the theories and technologies in tissue engineering. Numerous types of stem cells have been isolated from dental tissue, such as dental pulp stem cells (DPSCs), stem cells isolated from human pulp of exfoliated deciduous teeth (SHED), periodontal ligament stem cells (PDLSCs), stem cells from apical papilla (SCAPs), and dental follicle cells (DFCs). All these cells can regenerate the tissue of tooth. This review outlines the cell types and strategies of stem cell therapy applied in tooth regeneration, in order to provide theoretical basis for clinical treatments.
Adult Stem Cells ; physiology ; Animals ; Cell Differentiation ; Humans ; Stem Cell Transplantation ; Tissue Engineering ; Tooth ; cytology ; growth & development ; physiology ; Wound Healing

Objective: To investigate the effect of endoplasmic reticulum (ER)-mitochondria coupling and the expression of mitofusion 2 (Mfn2) in periodontal ligament stem cells (PDLSC), so as to provide a theoretical basis and therapeutic target for promoting periodontal regeneration in treatment of periodontitis. Methods: The periodontal ligament tissue was scraped from extracted intact human teeth and teeth with periodontitis collected in the Department of Oral and Maxillofacial Surgery, the Fourth Military Medical University. The health PDLSC (H-PDLSC) and inflammatory PDLSC (P-PDLSC) were obtained respectively from the primary culture of the human teeth and cloned using 1imited diluted method. The level of ER-mitochondrial coupling was observed by transmission electron microscopy and organelle-specific fluorescence staining. Quantitative real-time PCR (qPCR) was used to detect the expression of Mfn2 in H-PDLSC and P-PDLSC. Tumor necrosis factor alpha (TNF-α) was used to simulate the inflammatory microenvironment. H-PDLSC was cultured in normal medium and media containing 5 and 10 mg/L TNF-α, named as H-PDLSC group, H-PDLSC+TNF-α (5 mg/L) group and H-PDLSC+TNF-α (10 mg/L) group, respectively. At the 7th day, qPCR was applied to detect the mRNA level of Mfn2. The expression of Mfn2 in P-PDLSC was down-regulated by small interfering RNA siMfn2. The osteogenic differentiation of P-PDLSC and P-PDLSC+siMfn2 were examined by qPCR at the 7th day, and alizarin red staining and cetyl pyridine chloride quantitative analysis at the 28th day after osteogenic induction. Results: The level of ER-mitochondrial coupling in the P-PDLSC group (the length of the coupling structure/mitochondrial perimeter was 0.55±0.10, the length of the coupling structure/endoplasmic reticulum perimeter was 0.44±0.08) was significantly higher than that in the H-PDLSC group (P<0.01). The co-localization of endoplasmic reticulum and mitochondria of P-PDLSC group was 0.71±0.09, which was significantly higher than that of H-PDLSC group (P<0.01). The expression level of Mfn2 in P-PDLSC (1.46±0.10) was higher than that in H-PDLSC (0.99±0.08). The expression levels of Mfn2 in H-PDLSC+TNF-α (5 mg/L) and H-PDLSC+TNF-α (10 mg/L) groups were 1.28±0.19, 1.54±0.43, respectively, which were both significantly higher than that in H-PDLSC (0.82±0.14) (P<0.01). P-PDLSC transfected with siMfn2 down-regulated the expression of Mfn2, and the osteogenic differentiation ability of P-PDLSC was restored. The results showed that the expression of alkaline phosphatase, Runt-related transcription factor-2 (RUNX2) and osteocalcin mRNA in P-PDLSC+siMfn2 group were significantly higher than that of the control group (P<0.01). The alizarin red staining and quantitative results of cetyl pyridinium chloride were consistent with the qPCR results. Conclusions In the microenvironment of inflammation, ER-mitochondrial coupling and the expression of Mfn2 of PDLSC increased, which might lead to a decrease in osteogenic differentiation of PDLSC. The specific mechanism needs to be further studied.