Effects of FGF2 Priming and Nrf2 Activation on the Antioxidant Activity of Several Human Dental Pulp Cell Clones Derived From Distinct Donors, and Therapeutic Effects of Transplantation on Rodents With Spinal Cord Injury.

In recent years, the interest in cell transplantation therapy using human dental pulp cells (DPCs) has been increasing. However, significant differences exist in the individual cellular characteristics of human DPC clones and in their therapeutic efficacy in rodent models of spinal cord injury (SCI); moreover, the cellular properties associated with their therapeutic efficacy for SCI remain unclear. Here, using DPC clones from seven different donors, we found that most of the clones were highly resistant to H2O2 cytotoxicity if, after transplantation, they significantly improved the locomotor function of rats with complete SCI. Therefore, we examined the effects of the basic fibroblast growth factor 2 (FGF2) and bardoxolone methyl (RTA402), which is a nuclear factor erythroid 2-related factor 2 (Nrf2) chemical activator, on the total antioxidant capacity (TAC) and the resistance to H2O2 cytotoxicity. FGF2 treatment enhanced the resistance of a subset of clones to H2O2 cytotoxicity. Regardless of FGF2 priming, RTA402 markedly enhanced the resistance of many DPC clones to H2O2 cytotoxicity, concomitant with the upregulation of heme oxygenase-1 (HO-1) and NAD(P)H-quinone dehydrogenase 1 (NQO1). With the exception of a subset of clones, the TAC was not increased by either FGF2 priming or RTA402 treatment alone, whereas it was significantly upregulated by both treatments in each clone, or among all seven DPC clones together. Thus, the TAC and resistance to H2O2 cytotoxicity were, to some extent, independently regulated and were strongly enhanced by both FGF2 priming and RTA402 treatment. Moreover, even a DPC clone that originally exhibited no therapeutic effect on SCI improved the locomotor function of mice with SCI after transplantation under both treatment regimens. Thus, combined with FGF2, RTA402 may increase the number of transplanted DPCs that migrate into and secrete neurotrophic factors at the lesion epicenter, where reactive oxygen species are produced at a high level.

Exosomes from dental pulp cells attenuate bone loss in mouse experimental periodontitis.

BACKGROUND AND OBJECTIVE: Exosomes are small vesicles secreted from many cell types. Their biological effects largely depend on their cellular origin and the physiological state of the originating cells. Exosomes secreted by mesenchymal stem cells exert therapeutic effects against multiple diseases and may serve as potential alternatives to stem cell therapies. We previously established and characterized human leukocyte antigen (HLA) haplotype homo (HHH) dental pulp cell (DPC) lines from human wisdom teeth. In this study, we aimed to investigate the effect of local administration of HHH-DPC exosomes in a mouse model of periodontitis. METHODS: Exosomes purified from HHH-DPCs were subjected to particle size analysis, and expression of exosome markers was confirmed by western blotting. We also confirmed the effect of exosomes on the migration of both HHH-DPCs and mouse osteoblastic MC3T3-E1 cells. A mouse experimental periodontitis model was used to evaluate the effect of exosomes in vivo. The morphology of alveolar bone was assessed by micro-computed tomography (µCT) and histological analysis. The effect of exosomes on osteoclastogenesis was evaluated using a co-culture system. RESULTS: The exosomes purified from HHH-DPCs were homogeneous and had a spherical membrane structure. HHH-DPC exosomes promoted the migration of both human DPCs and mouse osteoblastic cells. The MTT assay showed a positive effect on the proliferation of human DPCs, but not on mouse osteoblastic cells. Treatment with HHH-DPC exosomes did not alter the differentiation of osteoblastic cells. Imaging with µCT revealed that the exosomes suppressed alveolar bone resorption in the mouse model of periodontitis. Although no change was apparent in the dominance of TRAP-positive osteoclast-like cells in decalcified tissue sections upon exosome treatment, HHH-DPC exosomes significantly suppressed osteoclast formation in vitro. CONCLUSIONS: HHH-DPC exosomes stimulated the migration of human DPCs and mouse osteoblastic cells and effectively attenuated bone loss due to periodontitis.

Priming with FGF2 stimulates human dental pulp cells to promote axonal regeneration and locomotor function recovery after spinal cord injury.

Human dental pulp cells (DPCs), adherent cells derived from dental pulp tissues, are potential tools for cell transplantation therapy. However, little work has been done to optimize such transplantation. In this study, DPCs were treated with fibroblast growth factor-2 (FGF2) for 5-6 consecutive serial passages and were transplanted into the injury site immediately after complete transection of the rat spinal cord. FGF2 priming facilitated the DPCs to promote axonal regeneration and to improve locomotor function in the rat with spinal cord injury (SCI). Additional analyses revealed that FGF2 priming protected cultured DPCs from hydrogen-peroxide-induced cell death and increased the number of DPCs in the SCI rat spinal cord even 7 weeks after transplantation. The production of major neurotrophic factors was equivalent in FGF2-treated and untreated DPCs. These observations suggest that FGF2 priming might protect DPCs from the post-trauma microenvironment in which DPCs infiltrate and resident immune cells generate cytotoxic reactive oxygen species. Surviving DPCs could increase the availability of neurotrophic factors in the lesion site, thereby promoting axonal regeneration and locomotor function recovery.

Derivation of iPSCs after culture of human dental pulp cells under defined conditions.

Human dental pulp cells (hDPCs) are a promising resource for regenerative medicine and tissue engineering and can be used for derivation of induced pluripotent stem cells (iPSCs). However, current protocols use reagents of animal origin (mainly fetal bovine serum, FBS) that carry the potential risk of infectious diseases and unwanted immunogenicity. Here, we report a chemically defined protocol to isolate and maintain the growth and differentiation potential of hDPCs. hDPCs cultured under these conditions showed significantly less primary colony formation than those with FBS. Cell culture under stringently defined conditions revealed a donor-dependent growth capacity; however, once established, the differentiation capabilities of the hDPCs were comparable to those observed with FBS. DNA array analyses indicated that the culture conditions robustly altered hDPC gene expression patterns but, more importantly, had little effect on neither pluripotent gene expression nor the efficiency of iPSC induction. The chemically defined culture conditions described herein are not perfect serum replacements, but can be used for the safe establishment of iPSCs and will find utility in applications for cell-based regenerative medicine.

Hypoxia enhances colony formation and proliferation but inhibits differentiation of human dental pulp cells.

The hypoxia condition was expected to be suitable for the establishment and maintenance of human dental pulp cells (hDPCs), because they reside in a low-oxygen environment in vivo. Therefore, we presently examined the effects of hypoxia on the proliferation and differentiation of hDPCs in vitro. hDPCs grown under 3% O(2) showed a significantly higher proliferation rate than those under 21% O(2). Then, we prepared hypoxic cultures of hDPCs from older patients' teeth having inflammation and succeeded in recovering and expanding a small number of hDPCs. These cells were confirmed to have capability for osteo/odontogenic differentiation. Hypoxia suppressed the osteo/odontogenic differentiation of hDPCs in vitro and increased the number of cells expressing STRO-1, an early mesenchymal stem cell marker. This simple method will increase the possibility to obtain living hDPCs from damaged and/or aged tissues, from which it is ordinarily difficult to isolate living stem cells with differentiation capability.

Oral complaints and stimulated salivary flow rate in 1188 adults.

BACKGROUND: Recently, oral sensory complaints (OSC) were proposed as a disease entity to represent idiopathic sensory disturbances of dry mouth, burning mouth, and taste disturbance, even though neither the status of OSC in the general population nor its underlying mechanism has yet been elucidated. Moreover, these three OSC-related complaints have not been assessed in combination by means of a visual analog scale (VAS) in a large-scale, community-dwelling population of a broad age range. METHODS: In a 1188-member community-dwelling adult population, comprised of 373 males and 815 females, aged 20-90 years, the three OSC-related complaints and stimulated salivary flow rate (SSFR) were assessed by means of a VAS and modified Saxon test, respectively. Association of each complaint with age, gender, SSFR, and other complaints was analyzed. RESULTS: Increases in both prevalence and intensity of subjective dry mouth and burning mouth were associated closely with decreasing SSFR. Even for taste disturbance, which may be affected less significantly by salivation status than the other two complaints, a significant association was suggested between decreasing SSFR and especially severe taste disturbance. However, these oral complaints were found in considerable prevalence even in the individuals with high SSFR. Often overlapping presentation of these complaints and a close association in intensity between the complaints to each other were also found. CONCLUSIONS: Hyposalivation may be a significant and common etiology for the three oral complaints, although the considerable prevalence of complaints without hyposalivation suggests other etiologies, including those related to the OSC.