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FUN14 domain‑containing 1 (FUNDC1) is a receptor that has been previously reported to activate hypoxia‑induced mitophagy. However, the potential role of FUNDC1 in the pathophysiology of dental pulp diseases remains unknown. Therefore, present study first collected tissue specimens from patients with pulpitis and from healthy individuals. The results of reverse transcription‑quantitative PCR and immunohistochemical staining revealed markedly increased FUNDC1 and hypoxia‑inducible factor‑1α expression in pulpitis tissue specimens compared with those from healthy individuals. To provide a theoretical basis for the study of the occurrence, development and reparative mechanisms in the dental pulp after tissue injury, the present study then investigated the role of hypoxia‑induced mitophagy in the regulation of proliferation, migration and odontoblastic differentiation in human dental pulp cells (HDPCs), in addition, to the possible involvement of FUNDC1. The surface markers and multipotent differentiation capabilities of HDPCs were performed by flow cytometry (surface markers), alizarin red (osteogenic capabilities), alcian blue (chondrogenic capabilities) and oil red O (adipogenic capabilities). Following culture under hypoxia conditions (1% O

The exact phenotype of human periodontal ligament cells (hPDLCs) remains a controversial area. Basic fibroblast growth factor (FGF-2) exhibits various functions and its effect on hPDLCs is also controversial. Therefore, the present study examined the effect of FGF-2 on the growth and osteoblastic phenotype of hPDLCs with or without osteogenic inducers (dexamethasone and β-glycerophosphate). FGF-2 was added to defined growth culture medium and osteogenic inductive culture medium. Cell proliferation, osteogenic differentiation and mineralization were measured. The selected differentiation markers, Runx2, collagen type I, α1 (Col1a1), osteocalcin (OCN) and epidermal growth factor receptor (EGFR), were investigated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Runx2 and OCN protein expression was measured by western blotting. FGF-2 significantly increased the proliferation of hPDLCs, but did not affect alkaline phosphatase activity. RT-qPCR analysis revealed enhanced mRNA expression of Runx2, OCN and EGFR, but suppressed Col1a1 gene expression in the absence of osteogenic inducers, whereas all these gene levels had no clear trend in their presence. The Runx2 protein expression was clearly increased, but the OCN protein level showed no evident trend. The mineralization assay demonstrated that FGF-2 inhibited mineralized matrix deposition with osteogenic inducers. These results suggested that FGF-2 induces the growth of immature hPDLCs, which is a competitive inhibitor of epithelial downgrowth, and suppresses their differentiation into mineralized tissue by affecting Runx2 expression. Therefore, this may lead to the acceleration of periodontal regeneration.

Calcium ions (Ca2+) are a major constituent of most pulp-capping materials and have an important role in the mineralization of human dental pulp cells (hDPCs). A previous study by our group has shown that increased levels of Ca2+ can promote hDPC-mediated mineralization in long-term cultures (21 days). However, the initiation of mineralization occurs in the early stage of osteogenic inductive culture, and the effects of Ca2+ on the mineralization of hDPCs in short-term cultures (five days) have not been studied in detail. Furthermore, the underlying mechanism by which Ca2+ stimulates the mineralization of hDPCs has remained controversial. A strong correlation between mineralization and cell apoptosis and/or death has been identified. Thus, the present study hypothesized that Ca2+ may promote the onset of hDPC-mediated mineralization through inducing their apoptosis and/or death. To verify this hypothesis, Ca2+ was added to the growth culture medium and osteogenic culture medium at various concentrations. Alizarin Red S staining and reverse transcription-polymerase chain reaction analysis were used to evaluate the onset of mineralization. Furthermore, the cell counting kit-8 and fluorescein isothiocyanate-Annexin V/propidium iodide double-staining method were adopted to detect the proliferation and apoptosis of hDPCs in the growth culture medium. An animal experiment and scanning electron microscopic observation of ceramic graft implants were applied to measure the mineralization in vivo. The results showed that 5.4 and 9.0 mM Ca2+ accelerated the onset of mineralized matrix nodule formation, promoted osteopontin mRNA expression and induced marked cell apoptosis and necrosis, but had no obvious effect on cell proliferation. These findings indicated a positive association between cell apoptosis and/or death and the timing of formation as well as the quantity of extracellular mineralization induced by Ca2+ in short-term cultured hDPCs.