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The mammalian target of rapamycin (mTOR)-composed of multiple complexes, including mTOR complex 1/2 (mTORC1/2)-is a serine-threonine kinase that regulates embryonic development. The transcription factor, hypoxia-inducible factor-1α (HIF-1α), is also involved in embryonic development. As the relationship between mTOR and HIF-1α during embryonic development remains unclear, we investigated the relationship between the two using ex vivo submandibular salivary gland organ cultures. When the expression of HIF-1α increased under hypoxic conditions (1% O

To prevent aspiration, oral care with gel is a common method for high-risk patients. An oral care gel is used to clean and moisturize the oral cavity. However, the effects of gel care on oral bacteria remain unclear. In this pilot study, we describe a matching transformation system (MA-T) for elderly high-risk patients. MA-T is an on-demand aqueous chlorine dioxide solution that provides excellent safety with various antimicrobial activities even in the presence of abundant organic compounds. This study investigated the effects of MA-T gel on patients requiring nursing care. Membranous substances were present in the oral cavities of all patients. Oral bacteria and intraoral humidity were examined by daily care using an MA-T gel. Moreover, oral membranous substances were analyzed and bacteria were cultured in selective mediums for opportunistic infection. Consequently, the number of bacteria decreased and oral moisture was improved by treatment with MA-T gel. It is important to care for MA-T gels not only for the single use of professional care but also for daily care. Furthermore, culture experiments showed that MA-T controlled the propagation of opportunistic bacterial infections. The MA-T gel proved to be effective for the oral care of elderly people. Membranous substances may be observed in the oral cavity of persons requiring nursing care for tubal feeding. The results of this pilot study suggest that MA-T, a new disinfectant, can be applied in oral care to reduce aspiration.

Objectives To determine the general condition of elderly xerostomia patients, we collected their background and medication data in order to potentially treat their xerostomia. It is critical to identify the drugs causing xerostomia in elderly patients. A total of 521 patients who were examined at the Xerostomia Clinic of Osaka University Dental Hospital were included in the study. We obtained patients’ data on age, sex, number of primary illnesses, Saxon test scores, oral moisture test, subjective symptoms, and drug types from their clinical records. Results The mean age of the patients was 65.2 ± 13.3 years. Although all patients exhibited xerostomia symptoms, there were a lot of patients without hyposalivation. With respect to medication, each elderly xerostomia patient took an average of 6.8 ± 4.4 medicines. A total of 26.1% of patients in their 70 s took more than ten number of drugs. In addition, the number of frequently used medication medicine was different between elderly and young patients. Most of the medicines had xerostomia as a side effect in medical package inserts. Moreover, the quantity of salivation significantly decreased in patients who took more than seven drugs in comparison with the patients who did not take medicine. Conclusions As patients age, the number of medications they take tends to increase, subsequently increasing their risk of xerostomia. For the health of the patients, it is critical that an accurate diagnosis is made. Clinical relevance To establish therapeutic strategies for treatment of xerostomia, this study provides new and important information that will help in the development of xerostomia medical treatment.

This study investigated olfactory/taste functions in older persons requiring nursing care to clarify whether these functions are associated with appetite or nutritional status. Seventy-two older persons requiring nursing care and 37 unassisted persons were surveyed for olfactory function, taste function, appetite, and nutritional status. Age-adjusted covariance analysis was conducted between the two groups. Both groups showed reduced olfactory and taste functions; these functions were more markedly reduced in participants requiring nursing care compared to those who did not. Both groups had similar appetite and nutritional status findings, suggesting that these factors are not associated with olfactory and taste functions.

The salivary glands produce saliva and are important in maintaining oral health. Saliva keeps the mouth moist, cleanses the oral cavity, aids digestion, and has antibacterial properties. Saliva also helps in swallowing and speech. Investigating the development of the salivary glands is thus relevant in the context of both health and disease. Various cell culture methods have been used to study salivary gland development, including culturing cells in two dimensions (2D). Under physiological conditions, cells constantly interact with other cells and the extracellular matrix, which controls complex biological functions such as cell migration and apoptosis, and can modulate gene expression. Since many of these functions are not accurately represented or reproduced in 2D culture, the results of in vitro experiments using such culture methods are often not reflected in vivo. The use of 3D cultures, such as organ cultures, has helped address this issue and has emerged as a model that better reflects the in vivo physiological environment. Here, we describe a protocol for establishing submandibular salivary gland organ culture that is more concise and simpler than previous methods and includes the separation and dissection of the salivary glands. We also describe the use of environmental stress (hypoxic stimulation) and inhibitors (U0126, LY294002, and rapamycin) to elucidate signaling pathways involved in salivary gland development. This protocol can provide researchers with a simpler and more robust method of salivary gland organ culture, enabling analysis of organ-based signaling pathways to advance developmental biology research. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Submandibular salivary gland organ culture Basic Protocol 2: Analysis of salivary gland development in the presence of hypoxia and signaling pathway inhibitors Basic Protocol 3: Western blotting using submandibular salivary gland organ culture.

MA-T (Matching Transformation System®) is a proprietary chemical mixture for on-demand production of aqueous chlorine dioxide that is used for the treatment of oral malodor. MA-T is also an effective disinfectant against at least 39 pathological microorganisms, including severe acute respiratory syndrome coronavirus 2, and therefore may be useful as a disinfectant mouthwash to prevent the spread of infection. Accidental ingestion is the putative worst hazard scenario associated with mouthwash use; therefore, here we investigated the safety of MA-T ingestion in mice. Mice were provided drinking water containing 0-3000 μg/ml MA-T for 7 days followed by non-spiked drinking water for an additional 14 days. At day 7, mice ingesting 1000 or 3000 μg/ml MA-T showed significantly decreased body weight and significantly increased liver, kidney, and heart tissue injury biomarkers compared with control. However, at 14 days after stopping MA-T ingestion, body weight and tissue injury biomarkers had returned to normal. Histological analysis revealed that MA-T-induced injuries in liver, kidney, spleen, stomach, duodenum, colon, and rectum had also recovered at 14 days after stopping MA-T ingestion; however, mild vascular endothelial injuries remained in heart, jejunum, and ileum in the worst-case scenario. Taken together, MA-T may be potentially safety for further development as a disinfectant mouthwash by risk management, such as placing a caution of the label and adding a distinctive flavor.

Matching transformation system (MA-T), an on-demand aqueous chlorine dioxide solution, is an excellent safety disinfectant, because chlorine dioxide is not detected during storage or before use. The production of chlorine dioxide in MA-T is induced by a catalytic reaction in the presence of target microorganisms. In this study, we investigated MA-T disinfection of masks as a reuse method to eliminate mask shortages. After spraying Escherichia coli on sterilized surgical mask, samples (factitiously contaminated masks) were treated with MA-T spraying or immersion, and the bactericidal efficacy was assessed by culturing. Used surgical masks were also sprayed with MA-T or were immersed in MA-T, and then were cultured to verify the bactericidal effect. The performance of N95 masks was assessed before and after application of MA-T. After spraying with MA-T, the numbers of bacteria of factitiously contaminated masks and used masks were drastically reduced compared with control samples (not applicable and p = 0.002, respectively). After MA-T immersion, the bacterial counts of both masks (factitiously contaminated masks and used masks) were significantly reduced (both p = 0.002). Taken together, the disinfection test on factitiously contaminated with E. coli and used surgical masks showed that masks can be disinfected by MA-T spray and sterilized by immersion, respectively. The N95 mask performance test after 30 min of immersion in MA-T showed that MA-T disinfected the mask without degrading the performance of the mask. In conclusion, MA-T is useful for the reuse of masks because of its decontamination effect and safety while maintaining the function of the mask.

Background: Patients with cerebral palsy are known to have reduced swallowing function because of various causes. Aspiration pneumonia resulting from decreased swallowing function is a major complication in patients with severe cerebral palsy and is directly associated with their survival prognosis. This necessitates an appropriate assessment and response to the aforementioned risk. Previous reports on cerebral palsy patients have mentioned large differences in the prevalence of aspiration, when assessed with standard swallowing function tests. Moreover, there is a weak association between aspiration detected by swallowing function tests, such as video endoscopy and video fluoroscopy, and the incidence of pneumonia. Considering the difficulty in evaluating the risk of pneumonia, we focused on swallowing frequency as an index of daily swallowing function. Swallowing motion protects the airway by safely directing the food, saliva, and secretions accumulated in the pharynx into the esophagus to prevent aspiration and entry into the trachea. Thus, swallowing frequency during daily life can be considered an index for evaluating the risk of regular aspiration and pneumonia. In this retrospective study, we investigated the relationship between swallowing frequency and pneumonia in patients with severe cerebral palsy. Methods: Fifty seven cerebral palsy patients were included in this study. The swallowing frequency was measured three times for each patient on separate days, and the reproducibility was examined by calculating the intraclass correlation coefficient. Further, the relationship between swallowing frequency and history of pneumonia was investigated by multivariate logistic regression analysis.Results: While the swallowing frequency differed between participants, it was constant within individuals (intraclass correlation coefficient: 0.941). Furthermore, the swallowing frequencies per hour were 12.2 ± 12.2 and 27.0 ± 20.4 in the patient groups with and without a history of pneumonia, respectively (PConclusions: Swallowing frequency could be used as an index for assessing the risk of dysphagia and pneumonia in patients with severe cerebral palsy.

The novel, severe acute respiratory syndrome coronavirus (SARS‐CoV‐2) was firstly reported in late December of 2019 and subsequently caused a global outbreak. It has been shown that SARS‐CoV‐2 uses ACE2 (Angiotensin Converting Enzyme 2) as a cellular receptor for host cell entry through the surface unit of SARS‐CoV spike glycoprotein. In this brief report, we analyze ACE2 protein expression and localization in human salivary gland, and propose a possible role of saliva in the pathogenesis of Coronavirus disease 2019 (COVID‐19).

Background/Aim: Although mucociliary clearance is important for preventing pneumonia, its association with the onset of pneumonia is unclear. The aim of this study is to examine the association between saccharin test results as a potential measure of mucociliary clearance and history of pneumonia in nursing home residents. Patients and Methods: Ninety elderly nursing home residents (elderly group) were selected, 35 of whom had a history of pneumonia. Twenty-five healthy adults (adult group) were also investigated to provide baseline values for this study. We conducted the saccharin test to evaluate mucociliary clearance and compared the saccharin time (ST) between those with and without history of pneumonia. Results: Mean ST in the adult group was 12±6 min. The ST in the pneumonia group was significantly longer than that in the non-pneumonia group (32±23 min vs. 17±13 min) (p

PURPOSE: This study examined whether certain medical complications influence the feasibility of tube removal. METHODS: 42 subjects with dysphagia who were under the age of 2.5 years were nourished entirely through feeding tubes. Additionally, they were judged to have no aspiration. The following data about the infants were collected through a retroactive survey: age at which oral feeding training commenced, gender, and whether certain medical complications (cardiovascular, respiratory, digestive, neurological, or oral) had been present at birth. The data were analyzed to determine which type of medical complication affected the likelihood of removing the feeding tube from the infant at 3 years of age. RESULTS: Of the five medical complications examined, cardiovascular complications significantly affected the feasibility of tube removal (p = 0.049). CONCLUSION: Pediatric dysphagia patients with cardiac complications, compared to those with other complications, may take longer to transition off tube feeding.

Salivary glands act as virus reservoirs in various infectious diseases and have been reported to be targeted by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the mechanisms underlying infection and replication in salivary glands are still enigmatic due to the lack of proper in vitro models. Here, we show that human induced salivary glands (hiSGs) generated from human induced pluripotent stem cells can be infected with SARS-CoV-2. The hiSGs exhibit properties similar to those of embryonic salivary glands and are a valuable tool for the functional analysis of genes during development. Orthotopically transplanted hiSGs can be engrafted at a recipient site in mice and show a mature phenotype. In addition, we confirm SARS-CoV-2 infection and replication in hiSGs. SARS-CoV-2 derived from saliva in asymptomatic individuals may participate in the spread of the virus. hiSGs may be a promising model for investigating the role of salivary glands as a virus reservoir.

Polypharmacy in elderly persons living at home or in a nursing home is an issue. In the field of dentistry, strategies to reduce polypharmacy must be promoted; however, there is insufficient basic data on medications received by elderly persons with dysphagia living at home or in a nursing home. The subjects were 106 elderly persons with dysphagia living at home or in a nursing home. Based on their medical records, the presence of disease and number/type of drugs being administered were investigated. Stroke, dementia, and hypertension were common. The mean number of drugs per person was 6.3 (minimum: 0, maximum: 15). Drugs for digestive ulcers were the most frequently prescribed medication, followed by hypotensive drugs, anti-parkinsonism drugs, and other central nervous drugs. Fifty-nine patients (52.8%) had taken drugs that may cause dysphagia, and 19 (17.9%) had taken drugs that may cause aspiration. Of the subjects, 68.9% had taken ≥5 drugs, demonstrating polypharmacy in elderly persons with dysphagia living at home or in a nursing home. Many drugs that may cause dysphagia or aspiration had been prescribed, suggesting the importance of dentists' reducing polypharmacy from the viewpoint of swallowing.

Background Detecting and addressing aspiration early in children with dysphagia, such as those with cerebral palsy, is important for preventing aspiration pneumonia. The current gold standards for assessing aspiration are swallowing function tests, such as fiberoptic endoscopic evaluation of swallowing (FEES) and videofluorographic swallowing study; however, the relationship between aspiration of secretion vs aspiration of foodstuff and pulmonary injury is unclear. To clarify this relationship, we examined the correlations between pneumonia findings from chest computed tomography (CT) and the presence or absence of aspiration detected by FEES. Methods Eighty-five children (11 years 2 months ±7 years 2 months) underwent FEES and chest CT. Based on the FEES findings, the participants were divided into groups: with and without food aspiration, and with and without saliva aspiration. Correlations between chest CT findings of pneumonia and the presence or absence of each type of aspiration were then examined. Results No significant correlations were observed between food aspiration and chest CT findings of pneumonia, whereas saliva aspiration and chest CT findings of pneumonia were significantly correlated. In addition, saliva aspiration was significantly associated with bronchial wall thickening (p < 0.01) and atelectasis (p < 0.05). Conclusions Our findings in children suggest that: (1) the presence or absence of food aspiration detected by FEES evaluation has little correlation with pneumonia, and (2) the presence or absence of saliva aspiration may be an indicator of aspiration pneumonia risk.

To determine the general condition of elderly xerostomia patients, we collected their background and medication data in order to potentially treat their xerostomia. It is critical to identify the drugs causing xerostomia in elderly patients. A total of 521 patients who were examined at the Xerostomia Clinic of Osaka University Dental Hospital were included in the study. We obtained patients' data on age, sex, number of primary illnesses, Saxon test scores, oral moisture test, subjective symptoms, and drug types from their clinical records.The mean age of the patients was 65.2 ± 13.3 years. Although all patients exhibited xerostomia symptoms, there were a lot of patients without hyposalivation. With respect to medication, each elderly xerostomia patient took an average of 6.8 ± 4.4 medicines. A total of 26.1% of patients in their 70 s took more than ten number of drugs. In addition, the number of frequently used medication medicine was different between elderly and young patients. Most of the medicines had xerostomia as a side effect in medical package inserts. Moreover, the quantity of salivation significantly decreased in patients who took more than seven drugs in comparison with the patients who did not take medicine.As patients age, the number of medications they take tends to increase, subsequently increasing their risk of xerostomia. For the health of the patients, it is critical that an accurate diagnosis is made.To establish therapeutic strategies for treatment of xerostomia, this study provides new and important information that will help in the development of xerostomia medical treatment.

The transcription factor p63, a component of the p53 family, has important functions in development, homeostasis, and regeneration of epithelial tissues. However, the role of p63 in the regeneration of exocrine glands, including the salivary glands (SGs), has not been fully investigated. We investigated p63 expression in SG regeneration induced by duct ligation and irradiation. The expression of ΔNp63, a p63 isoform, increased and was colocalized with keratin 5 positive cells were myoepithelial cells. Furthermore, ΔNp63 expression was regulated by FGF7 stimulation via p38 MAPK phosphorylation and affected SG morphogenesis. These results suggest that ΔNp63 is essential for SG regeneration and may be a new target for regenerative treatment.

To investigate olfactory function in elderly subjects requiring nursing care to clarify its association with appetite and nutritional status. Facility for the elderly requiring nursing care. Participants: The subjects were 158 elderly people requiring nursing care and 37 elderly people not requiring nursing care. Experiment I: Olfactory function and factors (cognitive function, appetite, and nutritional status) that may be associated with it were compared between the elderly subjects requiring nursing care and those not requiring nursing care using covariance analysis in consideration of age. For evaluation, the OSIT-J was used for olfactory function, the HDS-R for cognitive function, the CNAQ for appetite, and BMI for nutritional status. Experiment II: The subjects were the same elderly subjects requiring nursing care in Experiment I, and food intake was surveyed in addition to the OSIT-J, HDS-R, CNAQ, and BMI. A univariate linear regression analysis was performed with OSIT-J as the response variable, and age, HDS-R, CNAQ, BMI, and food intake as the explanatory variables. Experiment I: On covariance analysis, the OSIT-J score was significantly lower for the elderly subjects requiring nursing care than for those not requiring nursing care (p

Objectives Salivary gland hypofunction, known as xerostomia, caused by radiation therapy for head & neck cancer and Sjӧgren's syndrome, causes various problems in oral health, and profoundly reduces quality of life. This review describes our database in the area of oral biology to establish new therapies for patients suffering from xerostomia. Highlight Here we review the recent approaches that have enabled us to better understand the mechanisms of salivary gland development. Furthermore, we highlight proposed approaches intended to recover salivary gland function using both gene and cell-based therapy. Conclusions A thorough understanding of the mechanisms involved in salivary gland is necessary in order to design effective therapies for regeneration of damaged salivary glands.

Organoids generated from pluripotent stem cells are used in the development of organ replacement regenerative therapy by recapitulating the process of organogenesis. These processes are strictly regulated by morphogen signalling and transcriptional networks. However, the precise transcription factors involved in the organogenesis of exocrine glands, including salivary glands, remain unknown. Here, we identify a specific combination of two transcription factors (Sox9 and Foxc1) responsible for the differentiation of mouse embryonic stem cell-derived oral ectoderm into the salivary gland rudiment in an organoid culture system. Following orthotopic transplantation into mice whose salivary glands had been removed, the induced salivary gland rudiment not only showed a similar morphology and gene expression profile to those of the embryonic salivary gland rudiment of normal mice but also exhibited characteristics of mature salivary glands, including saliva secretion. This study suggests that exocrine glands can be induced from pluripotent stem cells for organ replacement regenerative therapy., Functional salivary glands have not been generated from embryonic stem cells (mESCs) to date. Here the authors demonstrate directed in vitro differentiation of mESCs to oral ectoderm and salivary gland rudiments that form mature, functional salivary glands after orthotopic transplantation.

Runx1 deficiency results in an anteriorly specific cleft palate at the boundary between the primary and secondary palates and in the first rugae area of the secondary palate in mice. However, the cellular and molecular pathogenesis underlying such regional specificity remain unknown. In this study, Runx1 epithelial-specific deletion led to the failed disintegration of the contacting palatal epithelium and markedly downregulated Tgfb3 expression in the primary palate and nasal septum. In culture, TGFB3 protein rescued the clefting of the mutant. Furthermore, Stat3 phosphorylation was disturbed in the corresponding cleft regions in Runx1 mutants. The Stat3 function was manifested by palatal fusion defects in culture following Stat3 inhibitor treatment with significant downregulation of Tgfb3. Tgfb3 is therefore a critical target of Runx1 signaling, and this signaling axis could be mediated by Stat3 activation. Interestingly, the expression of Socs3, an inhibitor of Stat3, was specific in the primary palate and upregulated by Runx1 deficiency. Thus, the involvement of Socs3 in Runx1-Tgfb3 signaling might explain, at least in part, the anteriorly specific downregulation of Tgfb3 expression and Stat3 activity in Runx1 mutants. This is the first study to show that the novel Runx1-Stat3-Tgfb3 axis is essential in anterior palatogenesis.

The aim of this study was to investigate the predictors of dental changes associated with long-term treatment with oral appliances (OAs) in patients with obstructive sleep apnea (OSA).This was a retrospective study to investigate Japanese patients with OSA receiving long-term treatment with OAs. Comparisons of cephalometric analysis were carried out between the initial and follow-up assessments of dental and skeletal changes. Based on dental changes, predictors that may cause side effects were investigated.A total of 64 patients (average age at start of treatment: 57.7 ± 14.2 years, 44 males) were included in this study. The average duration of treatment was 4.3 ± 2.1 years. Over the total treatment period, there was a significant reduction in overjet (OJ) (1.5 ± 1.3 mm) and overbite (0.90 ± 1.5 mm), and an increase in the lower incisor line to the mandibular plane (3.1 ± 5.4°). A larger reduction in OJ of ≥ 1 mm was associated with treatment duration, use frequency, and mandibular advancement of the OAs. In addition to these predictive factors, the number of teeth was correlated with the amount of OJ reduction.For long-term treatment with OAs, the risk of dental side effects should be considered, such as a reduction in OJ. A small number of maxillary teeth, as well as the factors associated with OAs, including treatment duration, use frequency, and mandibular advancement of the OAs, was correlated with an increased rate of OJ reduction.A commentary on this article appears in this issue on page 7.

Purpose In 2013, we reported the results of a third-generation oral moisture-checking device in a multicentre clinical study involving patients with dry mouth and healthy volunteers. Subsequently, several improvements have been made to the third-generation device, and a fourth-generation device is now commercially available. This study aimed to confirm the usefulness of this improved fourth-generation device in the diagnosis of dry mouth and to assess the physiological wetness of lingual mucosa by using this device. Materials and Method This multicentre study comprised subjects with dry mouth (dry mouth group) and those without dry mouth (healthy group). Results In this study, the degree of moisture was considerably different between the two groups. Receiver operating characteristic analysis revealed an area under the curve value of 0.831. Sensitivity and specificity values were close to 80% in cases where the degree of moisture ≥29.6 was defined as normal, ≤27.9 was defined as dry mouth, and 28.0–29.5 was defined as borderline dry mouth. Conclusions These results suggest that the improved fourth-generation moisture-checking device can be used for the diagnosis of oral dryness.

Salivary secretion displays day-night variations that are controlled by the circadian clock. The central clock in the suprachiasmatic nucleus (SCN) regulates daily physiological rhythms by prompting peripheral oscillators to adjust to changing environments. Aquaporin 5 (Aqp5) is known to play a key role in salivary secretion, but the association between Aqp5 and the circadian rhythm is poorly understood. The aim of our study was to evaluate whether Aqp5 expression in submandibular glands (SMGs) is driven by the central clock in the SCN or by autonomous oscillations. We observed circadian oscillations in the activity of period circadian protein homolog 2 and luciferase fusion protein (PER2::LUC) in cultured SMGs with periodicity depending on core clock genes. A daily rhythm was detected in the expression profiles of Aqp5 in SMGs in vivo. In cultured SMGs ex vivo, clock genes showed distinct circadian rhythms, whereas Aqp5 expression did not. These data indicate that daily Aqp5 expression in the mouse SMG is driven by the central clock in the SCN.

The objective of this study was to determine the utility of nasoendoscopy of the upper airway as a predictor of the efficacy of oral appliance treatment in obstructive sleep apnoea (OSA).A total of 61 consecutive patients with moderate-to-severe polysomnographically diagnosed OSA were recruited for this study. Using nasoendoscopy, we prospectively assessed the velopharynx and oro/hypopharynx in each patient while awake and in the supine position. We measured cross-sectional area (CSA), and anteroposterior and lateral diameters of the airway before and after mandibular advancement, and expressed the changes in dimensions as expansion ratios (after/before). We then compared the measurements of responders and nonresponders with oral appliance treatment.The expansion ratio (median (interquartile range)) for the CSA was greater in responders compared with nonresponders in the velopharynx (2.9 (2.3–5.0)versus1.7 (1.5–1.9), pversus2.4 (1.8–3.7), pThese results indicate that nasoendoscopy may have significant clinical utility in predicting the success of oral appliance treatment.

Salivary gland hypofunction, also termed as xerostomia, is caused by radiation therapy for head and neck cancer or Sjogren's syndrome, leading to a detrimental impact on oral health and quality of life. This review describes current studies on salivary gland development and the translational approaches of basic science to treating patients with dysfunction and hypofunction of the salivary gland. Here, we review the most recent studies that have offered better insight into the mechanisms of salivary gland development and regeneration. Furthermore, we highlight proposed approaches with the aim of recovering salivary gland function using both gene- and cell-based therapy. A thorough understanding of the mechanisms involved in salivary gland development is necessary in order to design effective therapies for regeneration and repair of damaged salivary glands.

Background Most animals and organs have regenerative capabilities. Whether regeneration is a developmental process or a distinct phenomenon that is independent of development is debatable. Method We examined the differences between developing and regenerating salivary glands using duct-ligation models. We performed morphological analyses comparing submandibular gland regeneration and development. To reveal the proliferation processes that occur during salivary gland regeneration and development, we counted the number of Ki67-positive cells over time. In addition, we examined the expression of the following markers: aquaporin 5, smooth muscle actin, cytokeratin 7, and tubulin beta 3. Result The proliferation patterns seen during regeneration differed from those observed during development. Different salivary gland marker expression patterns were seen during development and regeneration. Conclusion This study showed that regenerating salivary glands do not follow the same growth process as developing salivary glands.

Development of the salivary gland is characterized by extensive branching morphogenesis. Although various molecules have been implicated in salivary gland development, the role of the mammalian target of rapamycin (mTOR) signalling pathway, including both mTOR complexes 1 and 2 (mTORC1 and 2), in salivary gland development is unknown. Here, we examined protein expression levels related to the mTOR signalling pathway using an ex vivo submandibular salivary gland (SMG) organ culture. We showed that branching buds in the salivary glands were substantially decreased and phosphorylation of mTORC1 signalling pathway related proteins (mTOR, p70 ribosomal protein S6 kinase 1 and eukaryotic initiation factor 4E-binding protein 1) was inhibited by rapamycin (an mTOR inhibitor). In addition, AKT, which is an upstream protein kinase of mTORC1 and is downstream of mTORC2, is inhibited by LY294002 (a phosphatidylinositol 3-kinase inhibitor), but not by rapamycin. Moreover, rapamycin-treated ICR neonatal mice exhibited a reduction in both body weight and salivary glands compared with vehicle-treated neonatal mice. The present data indicate that the mTOR signalling pathway, including both mTORC1 and mTORC2, plays a critical role in salivary gland development both in ex vivo SMG organ culture and ICR neonatal mice in vivo.