High-intensity laser therapy (HILT) and photobiomodulation therapy (PBMT) are two types of laser treatment. According to recent clinical reports, PBMT promotes wound healing after trauma or surgery. In addition, basic research has revealed that cell differentiation, proliferation, and activity and subsequent tissue activation and wound healing can be promoted. However, many points remain unclear regarding the mechanisms for wound healing induced by PBMT. Therefore, in this review, we present an example from our study of HILT and PBMT irradiation of tooth extraction wounds using two types of lasers with different characteristics (diode laser and carbon dioxide laser). Then, the effects of PBMT on the wound healing of bone tissues are reviewed from histological, biochemical, and cytological perspectives on the basis of our own study of the extraction socket as well as studies by other researchers. Furthermore, we consider the feasibility of treatment in which PBMT irradiation is applied to stem cells including dental pulp stem cells, the theme of this Special Issue, and we discuss research that has been reported on its effect.

Introduction: The purpose of the present study was to clarify the relationships between the risk of malnutrition as a preliminary stage of malnutrition and overall and oral measurements for sarcopenia in older Japanese adults. Methods: Forty-five participants (79.7 ± 6.1 years) were included in the analysis. The nutrition status of the participants was assessed using the Mini Nutritional Assessment-Short Form (MNA-SF) and classified into two groups: normal and at risk of malnutrition. Overall measurements for sarcopenia in the present study were the skeletal muscle mass index, grip strength, and walking speed, while oral measurements were the cross-sectional area of the geniohyoid muscle, tongue pressure (TP), and oral diadochokinesis. Results: MNA-SF correlated with TP (r = 0.347, p = 0.019). We observed decreases of 5.7 kPa in TP and 3.9 kg/cm² in BMI in the at risk of malnutrition group. A multiple regression analysis of parameters contributing to the risk of malnutrition identified TP as an independent variable (β = 0.913, p = 0.042). Conclusions: The present results demonstrate that the risk of malnutrition is associated with TP as an oral measurement for sarcopenia, but not overall measurements for sarcopenia. Therefore, low TP may be related with the risk of malnutrition.

Although in vivo studies have explored the relationship between oral environment and microbial communities, a precise analysis of the effects of environmental pH on oral microbiota remains challenging owing to their complexity and external influences. This study aimed to investigate the effect of environmental pH on the structure and diversity of oral microbiota in vitro. Tongue coating samples from ten participants were cultured anaerobically at six pH levels (5.5–8.0) using adjusted media. After DNA extraction, high-throughput sequencing of the 16s rRNA V3–V4 region was performed. Microbial diversity was analyzed using alpha and beta diversity indices, and differential taxa were identified using linear discriminant analysis effect size (LEfSe). Alpha diversity analysis revealed reduced diversity at pH 5.5 and 8.0. Beta diversity revealed that microbial communities at pH 5.5, 7.5, and 8.0 were separated from those at pH 7.0. LEfSe identified bacterial species that were significantly altered at pH 5.5 and 8.0. Environmental pH significantly influences the diversity and composition of microbial communities, with substantial changes occurring under acidic or alkaline conditions. These findings provide deeper insight into how oral biofilms respond to pH variations, underscoring the critical role of pH in oral microbiota dynamics.

A number of studies have recently demonstrated the effectiveness of CO₂ laser irradiation for the repair and regeneration of scar tissue from injuries or surgical wounds. However, such studies of the oral mucosa are highly limited. Previous studies using CO₂ laser irradiation have indicated that two factors contribute to esthetic healing, namely, artificial scabs, which are a coagulated and carbonized blood layer formed on the wound surface, and photobiomodulation therapy (PBMT) for suppressing wound scarring and promoting wound healing. This review outlines basic research and clinical studies of esthetic healing with the use of a CO₂ laser for both artificial scab formation by high-intensity laser therapy and PBMT in the treatment of injuries and surgical wounds with small parenchymal defects in oral soft tissues. The results showed that the wound surface was covered by an artificial scab, enabling the accumulation of blood and the perfusion necessary for tissue regeneration and repair. Subsequent PBMT also downregulated the expression of transformation growth factor-b1, which is involved in tissue scarring, and decreased the appearance of myofibroblasts. Taken together, artificial scabs and PBMT using CO₂ lasers contribute to the suppression of scarring in the tissue repair process, leading to favorable esthetic and functional outcomes of wound healing.

Salivary biomarkers are promising molecules for diagnosing systemic diseases. Cytidine/uridine monophosphate kinase 2 (CMPK2) is associated with various systemic diseases. However, little is known about the role of the CMPK2 gene in saliva and dyslipidemia. This study investigated the relationship between serum lipid levels and Cmpk2 mRNA expression in the saliva of dyslipidemic mice. Additionally, immunofluorescence staining was employed to assess the localization of the CMPK2 protein in the submandibular gland. Two types of dyslipidemic mice were utilized: mice fed a high-fat and high-cholesterol (HFHC) diet and genetically dyslipidemic ApoE-deficient mice. The mice at 9 to 46 weeks were analyzed for serum lipid levels, Cmpk2 mRNA expression in saliva, and CMPK2 protein localization in the submandibular glands. Both dyslipidemic mice displayed elevated low-density lipoprotein cholesterol and total cholesterol in serum. ApoE-deficient mice apparently exhibited increased Cmpk2 expression in saliva. Immunofluorescence staining indicated that CMPK2 proteins were primarily localized in the serous acini, potentially associated with the secretion of Cmpk2 mRNA in saliva. These findings suggest that Cmpk2 mRNA increases and is detectable in the saliva of dyslipidemic mice, providing a viable experimental model to assess the potential use of CMPK2 as a biomarker for dyslipidemia.

Several protocols have been reported for inducing parathyroid differentiation from human pluripotent stem cells in vitro. However, the efficiency of terminal differentiation into mature parathyroid cells remains limited. In this study, we performed comparative transcriptomic analyses of parathyroid lineage-induced human induced pluripotent stem (iPS) cells to clarify their developmental stage identity. Comparative analyses with adult parathyroid adenoma, used as a surrogate reference for mature parathyroid cells, and thymuses revealed that the differentiated cells exhibited gene expression patterns consistent with early-stage parathyroid and thymus development, including TBX1, which is required for fate determination of the parathyroid–thymic primordium. On the other hand, the expression of mature parathyroid marker genes, such as PTH, GCM2, and the calcium-sensing receptor (CaSR), remained markedly lower than that in parathyroid adenoma. Under the differentiation conditions and durations examined, application of modified differentiation protocols did not significantly enhance the expression of mature parathyroid markers, although pharyngeal pouch developmental gene expression was maintained. Our findings indicate that current in vitro differentiation systems effectively induce the parathyroid–thymic primordium stage, while a developmental bottleneck at the transition from the primordium toward parathyroid lineage commitment remains.