Inhibitory effect of 405-nm blue LED light on the growth of Candida albicans and Streptococcus mutans dual-species biofilms on denture base resin.

We investigated whether irradiation with 405-nm blue LED light could inhibit the growth of not only single- but dual-species biofilms formed by Candida albicans and Streptococcus mutans on denture base resin and cause the alteration in gene expression related to adhesion and biofilm formation. C. albicans and S. mutans single-/dual-species biofilms were formed on the denture base specimens. The biofilms were irradiated with 405-nm blue LED light (power density output: 280 mW/cm2) for 0 (control) and 40 min. Dual-species biofilms were analyzed using CFU assay and fluorescence microscopy, and single-/dual-species biofilms were analyzed using alamarBlue assays and gene expression analysis. To assess the inhibitory effect of irradiation on dual-species biofilms, specimens after irradiation were aerobically incubated for 12 h. After incubation, the inhibition of growth was assessed using CFU assays and fluorescence microscopy. Data were analyzed using the Mann-Whitney U or Student's t test (p < 0.05). Irradiation produced a significant inhibitory effect on biofilms. Fluorescence microscopy revealed that almost all C. albicans and S. mutans cells were killed by irradiation, and there was no notable difference in biofilm thickness immediately after irradiation and after irradiation and incubation for 12 h. alamarBlue assays indicated the growth of the biofilms was inhibited for 12-13 h. The expression of genes associated with adhesion and biofilm formation-als1 in C. albicans and ftf, gtfC, and gtfB in S. mutans-significantly reduced by irradiation. Irradiation with 405-nm blue LED light effectively inhibited the growth of C. albicans and S. mutans dual-species biofilms for 12 h.

Microbicidal effect of 405-nm blue LED light on Candida albicans and Streptococcus mutans dual-species biofilms on denture base resin.

This study investigated: (1) the microbicidal effect of 405-nm blue LED light irradiation on biofilm formed by Candida albicans hyphae and Streptococcus mutans under dual-species condition on denture base resin, (2) the generation of intracellular reactive oxygen species (ROS) induced by irradiation, and (3) the existence of intracellular porphyrins, which act as a photosensitizer. Denture base resin specimens were prepared and C. albicans and S. mutans dual-species biofilms were allowed to form on the specimens. The biofilms were irradiated with 405-nm blue LED light and analyzed using the colony-forming unit assay, fluorescence microscopy, and scanning electron microscopy (SEM). Single-species biofilms of C. albicans and S. mutans formed on the specimens were irradiated with 405-nm blue LED light. After the irradiation, the intracellular ROS levels in C. albicans and S. mutans cells were measured. In addition, the level of intracellular porphyrins in C. albicans and S. mutans were measured. Irradiation for more than 30 min significantly inhibited the colony formation ability of C. albicans and S. mutans. Fluorescence microscopy revealed that almost all C. albicans and S. mutans cells were killed by irradiation. SEM images showed various cell damage patterns. Irradiation led to the generation of intracellular ROS and porphyrins were present in both C. albicans and S. mutans cells. In conclusion, irradiation with 405-nm blue light-emitting diode light for 40 min effectively disinfect C. albicans hyphae and S. mutans dual-species biofilms and possibly react with intracellular porphyrins resulting in generation of ROS in each microorganism.

Effectiveness of 405-nm blue LED light for degradation of Candida biofilms formed on PMMA denture base resin.

This study investigated (i) the degradation effect of 405-nm blue light-emitting diode (LED) light irradiation on Candida albicans and C. glabrata biofilms formed on denture base resin and (ii) the effects of 405-nm blue LED light irradiation on the mechanical and surface characteristics of the resin. Polymethyl methacrylate denture base resin discs were prepared, and C. albicans or C. glabrata biofilms formed on the denture base resin discs. Each biofilm was irradiated with 405-nm blue LED light under a constant output power (280 mW/cm2) for different times in a moisture chamber with 100% relative humidity. Postirradiation, each biofilm was analyzed using a colony-forming unit assay, fluorescence microscopy, and scanning electron microscopy (SEM). Parallelepiped specimens of acrylic resin were prepared, and changes in their flexural strength (FS), flexural modulus (FM), and surface roughness (Ra) preirradiation and postirradiation with 405-nm blue LED light were evaluated. Irradiation for 30 min completely inhibited colony formation in both Candida species. Fluorescence microscopy showed that almost all Candida cells were killed because of irradiation. SEM images showed various cell damage patterns, such as wrinkles, shrinkage, and cell surface damage. An increase in FS was noted postirradiation, but no significant changes were observed in FM and Ra preirradiation and postirradiation. In conclusion, irradiation with 405-nm blue LED light induces degradation of C. albicans and C. glabrata biofilms on denture base resin, even in the absence of photosensitizers, without resin surface deterioration.

Effect of melatonin on human dental papilla cells.

Melatonin regulates a variety of biological processes, which are the control of circadian rhythms, regulation of seasonal reproductive function and body temperature, free radical scavenging and so on. Our previous studies have shown that various cells exist in human and mouse tooth germs that express the melatonin 1a receptor (Mel1aR). However, little is known about the effects of melatonin on tooth development and growth. The present study was performed to examine the possibility that melatonin might exert its influence on tooth development. DP-805 cells, a human dental papilla cell line, were shown to express Mel1aR. Expression levels of mRNA for Mel1aR in DP-805 cells increased until 3 days after reaching confluence and decreased thereafter. Real-time reverse transcription-polymerase chain reaction showed that melatonin increased the expression of mRNAs for osteopontin (OPN), osteocalcin (OCN), bone sialoprotein (BSP), dentin matrix protein-1 (DMP-1) and dentin sialophosphoprotin (DSPP). Melatonin also enhanced the mineralized matrix formation in DP-805 cell cultures in a dose-dependent manner. These results strongly suggest that melatonin may play a physiological role in tooth development/growth by regulating the cellular function of odontogenic cells in tooth germs.

Nerve growth factor increases electrical activity of neural cells derived from murine bone marrow stromal cells.

OBJECTIVE: Nerve growth factor (NGF) triggers long-term neuronal excitability. We examined its effect on murine bone marrow stromal cells (BMSC)-derived neurons. METHODS: With an optimal differentiation protocol, BMSCs were differentiated into neurons in culture. To confirm the probability of differentiation of BMSC into neuron, the expression of neuronal marker protein, neurofilament, was examined by immunocytochemistry. To examine the electrophysiological properties of BMSC-derived neurons, the field potentials were recorded either from nontreated (control) BMSC-derived neurons or from BMSC-derived neurons after the treatment with NGF by using extracellular recording techniques. RESULTS: Most BMSC-derived neurons showed spontaneous discharges whose amplitudes were up to 2 mV. When NGF at a concentration of 100 ng/ml was applied to BMSC-derived neurons, the amplitudes of discrete field potentials were gradually enlarged within 1 min after NGF application and peaked 3 min later (20-fold the size of control). However, the enlargement of the amplitudes of field potentials almost disappeared 5 min after NGF application. CONCLUSION: This finding indicates that neuronal cells derived from murine BMSCs generate discrete field potential activities spontaneously and that NGF has the effect of enlarging transient, but not sustained, electrical activity of BMSC-derived neurons.

Automatic Diagnosis of Early-Stage Oral Cancer and Precancerous Lesions from ALA-PDD Images Using GAN and CNN.

A screening system for early-stage oral cancer and precancerous lesions should be established because it is difficult to detect them even for specialists and they are often detected too late. In this paper, we propose a method for automatically classifying fluorescence images acquired by ALA-PDD (Photodynamic Diagnosis using 5-Aminolevulinic Acid) into three classes: Normal, Low-Risk, High-Risk. We augment a small image dataset by training GAN (Generative adversarial networks) with Differentiable Augmentation, and then train CNN (Convolutional Neural Network) for the classification by the augmented dataset. Experimental results show good classification results, which suggest that the combination of ALA-PDD and CNN classification is a promising method for oral cancer screening. Clinical Relevance- The method proposed in this paper has a potential to be used as a screening method for early-stage oral cancer and precancerous lesions, that is non-invasive, accurate, easy to use, and does not require specialization.

Photodynamic Diagnosis Using 5-Aminolevulinic Acid with a Novel Compact System and Chromaticity Analysis for the Detection of Oral Cancer and High-Risk Potentially Malignant Oral Disorders.

Detecting early-stage oral cancer and precancerous lesions are critical to improving patient prognosis and quality of life after treatment. Photodynamic diagnosis using 5-aminolevulinic acid enables the detection of malignant lesions. This study aimed to improve the diagnostic accuracy of photodynamic diagnosis using an objective chromaticity analysis of fluorescence emitted from oral lesions. Sixty-seven patients with clinically suspicious oral cavity lesions underwent photodynamic diagnosis after topical application of 5-aminolevulinic acid solution, followed by imaging and histological evaluation of the lesions. Chromaticity red and green values were measured from the fluorescence images on the lesion, and the red-to-green ratio was calculated. The photodynamic diagnosis allowed for the visualization of oral cancer and high-risk dysplasia as red fluorescence. Compared to low-risk dysplasia and benign lesions, oral cancer and high-risk dysplasia areas had a significantly higher red value and red-to-green ratio. After setting the cutoff value, sensitivity and specificity were 83.3-88.7% and 83.3-83.9%, respectively, when discriminating between oral cancer or high-risk dysplasia and low-risk dysplasia or benign lesions. Photodynamic diagnosis combined with chromaticity analysis may be a valuable diagnostic tool for detecting oral lesions, with a high likelihood of malignant transformation.

Leptin and vascular endothelial growth factor regulate angiogenesis in tooth germs.

Leptin, a 16 kDa non-glycolated polypeptide of 146 amino acids produced by the ob gene, has a variety of physiological roles not only in lipid metabolism, hematopoiesis, thermogenesis and ovarian function, but also in angiogenesis. This study focuses to investigate the possibility that leptin, as an angiogenic factor, may regulate the angiogenesis during tooth development. We firstly studied the expression of leptin and vascular endothelial growth factor (VEGF) during tooth development immunohistochemically. This investigation revealed that leptin is expressed in ameloblasts, odontoblasts, dental papilla cells and stratum intermedium cells. This expression pattern was similar to that of VEGF, one of the most potent angiogenic factors. Interestingly, more leptin-positive cells were observed in the upper third portion of dental papilla, which is closest to odontoblastic layer, compared to middle and lower thirds. Moreover, in the dental papilla, more CD31 and/or CD34-positive vascular endothelial cells were observed in the vicinity of ameloblasts and odontoblasts expressing leptin and VEGF. These findings strongly suggest that ameloblasts, odontoblasts and dental papilla cells induce the angiogenesis in tooth germs by secretion of leptin as well as VEGF.

Expression and cellular localizaion of melatonin-synthesizing enzymes in rat and human salivary glands.

Melatonin, discovered in 1958, is secreted by the pineal gland primarily during the night. Its secretion is controlled by the light/dark cycle of the environment. Melatonin is also produced in and secreted by various extrapineal organs, tissues and cells and its synthesizing enzyme arylalkylamine N-acetyltransferase (AANAT) is expressed in various extrapineal organs, tissues and cells. Recently, it was reported that melatonin is present in saliva, but it is not certain where melatonin was synthesized and whether it was secreted into saliva and what function it may have in saliva. The present study was performed to investigate where melatonin was synthesized and whether it was secreted by salivary glands into saliva. We performed immunohistochemical analysis of the expression of AANAT in rat parotid, submandibular and sublingual glands and the expression of both AANAT and hydroxyindole-O-methyltransferase (HIOMT) in human submandibular glands. We evaluated the expression of AANAT and HIOMT mRNA in rat submandibular glands by quantitative reverse transcription-polymerase chain reaction. As a result, we observed expression of AANAT in epithelial cells of striated ducts in rat salivary glands and expression of AANAT, HIOMT and melatonin in epithelial cells of striated ducts in human submandibular glands. In addition, we also confirmed the expression of the most potent melatonin receptor, melatonin 1a receptor, in rat buccal mucosa. Our findings suggest that melatonin might be produced and secreted by salivary glands directly into saliva and that it might play some physiological role in the oral cavity.

A New Induction Method for the Controlled Differentiation of Human-Induced Pluripotent Stem Cells Using Frozen Sections.

Considering that every tissue/organ has the most suitable microenvironment for its functional cells, controlling induced pluripotent stem cell (iPSC) differentiation by culture on frozen sections having a suitable microenvironment is possible. Induced PSCs were cultured on frozen sections of the liver, the brain, the spinal cord, and cover glasses (control) for 9 days. The iPSCs cultured on the sections of the liver resembled hepatocytes, whereas those on sections of the brain and the spinal cord resembled neuronal cells. The percentage of hepatocytic marker-positive cells in the iPSCs cultured on the sections of the liver was statistically higher than that of those in the iPSCs cultured on the sections of the brain and the spinal cord or on cover glasses. In contrast, the iPSCs cultured on the sections of the brain and the spinal cord revealed a high percentage of neural marker-positive cells. Thus, iPSCs can be differentiated into a specific cell lineage in response to specific factors within frozen sections of tissues/organs. Differentiation efficacy of the frozen sections markedly differed between the iPSC clones. Therefore, our induction method could be simple and effective for evaluating the iPSC quality.

Non-Invasive Diagnostic System Based on Light for Detecting Early-Stage Oral Cancer and High-Risk Precancerous Lesions-Potential for Dentistry.

Oral health promotion and examinations have contributed to the early detection of oral cancer and oral potentially malignant disorders, leading to the adaptation of minimally invasive therapies and subsequent improvements in the prognosis/maintenance of the quality of life after treatments. However, the accurate detection of early-stage oral cancer and oral epithelial dysplasia is particularly difficult for conventional oral examinations because these lesions sometimes resemble benign lesions or healthy oral mucosa tissues. Although oral biopsy has been considered the gold standard for accurate diagnosis, it is deemed invasive for patients. For this reason, most clinicians are looking forward to the development of non-invasive diagnostic technologies to detect and distinguish between cancerous and benign lesions. To date, several non-invasive adjunctive fluorescence-based detection systems have improved the accuracy of the detection and diagnosis of oral mucosal lesions. Autofluorescence-based systems can detect lesions as a loss of autofluorescence through irradiation with blue-violet lights. Photodynamic diagnosis using 5-aminolevulinic acid (ALA-PDD) shows the presence of very early oral cancers and oral epithelial dysplasia as a red fluorescent area. In this article, currently used fluorescence-based diagnostic methods are introduced and discussed from a clinical point of view.

Grapefruit seed extract effectively inhibits the Candida albicans biofilms development on polymethyl methacrylate denture-base resin.

This study aimed to investigate the cleansing effects of grapefruit seed extract (GSE) on biofilms of Candida albicans (C. albicans) formed on denture-base resin and the influence of GSE on the mechanical and surface characteristics of the resin. GSE solution diluted with distilled water to 0.1% (0.1% GSE) and 1% (1% GSE) and solutions with Polident® denture cleansing tablet dissolved in distilled water (Polident) or in 0.1% GSE solution (0.1% G+P) were prepared as cleansing solutions. Discs of acrylic resin were prepared, and the biofilm of C. albicans was formed on the discs. The discs with the biofilm were treated with each solution for 5 min at 25°C. After the treatment, the biofilm on the discs was analyzed using a colony forming unit (CFU) assay, fluorescence microscopy, and scanning electron microscopy (SEM). In order to assess the persistent cleansing effect, the discs treated with each solution for 5 min were aerobically incubated in Yeast Nitrogen Base medium for another 24 h. After incubation, the persistent effect was assessed by CFU assay. Some specimens of acrylic resin were immersed in each solution for 7 days, and changes in surface roughness (Ra), Vickers hardness (VH), flexural strength (FS), and flexural modulus (FM) were evaluated. As a result, the treatment with 1% GSE for 5 min almost completely eliminated the biofilm formed on the resin; whereas, the treatment with 0.1% GSE, Polident, and 0.1% G+P for 5 min showed a statistically significant inhibitory effect on biofilms. In addition, 0.1% GSE and 0.1% G+P exerted a persistent inhibitory effect on biofilms. Fluorescence microscopy indicated that Polident mainly induced the death of yeast, while the cleansing solutions containing at least 0.1% GSE induced the death of hyphae as well as yeast. SEM also revealed that Polident caused wrinkles, shrinkage, and some deep craters predominantly on the cell surfaces of yeast, while the solutions containing at least 0.1% GSE induced wrinkles, shrinkage, and some damage on cell surfaces of not only yeasts but also hyphae. No significant changes in Ra, VH, FS, or FM were observed after immersion in any of the solutions. Taken together, GSE solution is capable of cleansing C. albicans biofilms on denture-base resin and has a persistent inhibitory effect on biofilm development, without any deteriorations of resin surface.

Histological evaluation of apatite cement containing atelocollagen.

Tissue response to apatite cement (AC) containing atelocollagen (AC (ate)) was evaluated using conventional AC (c-AC) as a control material. At one week, the only difference between AC (ate) and c-AC was found in the soft tissue response. With c-AC, a moderate inflammatory response was exhibited: small particles of c-AC were scattered in the cutaneous tissue and many foreign body giant cells were aggregated around the scattered c-AC, whereas AC (ate) showed only a slight inflammatory response with few foreign body giant cells. In terms of bone tissue response, difference between AC (ate) and c-AC was observed at four weeks. New bone formation was observed along the cement at the edge of the pre-existing cortical bone in both c-AC and AC (ate). However, in the case of AC (ate), more abundant and thicker new bone was formed along the cement in the bone marrow when compared with c-AC.

Cryopreservation Method for the Effective Collection of Dental Pulp Stem Cells.

Dental pulp stem cells (DPSCs) are an attractive cell source for use in cell-based therapy, regenerative medicine, and tissue engineering because DPSCs have a high cell proliferation ability and multidifferentiation capacity. However, several problems are associated with the collection and preservation of DPSCs for use in future cell-based therapy. In particular, the isolation of DPSCs for cryopreservation is time consuming and expensive. In this study, we developed a novel cryopreservation method (NCM) for dental pulp tissues to isolate suitable DPSCs after thawing cryopreserved tissue. Using the NCM, dental pulp tissues were cultured on adhesion culture dishes for 5 days and then cryopreserved. After thawing, the cryopreserved dental pulp tissue fragments exhibited cell migration. We evaluated each property of DPSCs isolated using the NCM (DPSCs-NCM) and the explant method alone without cryopreservation (DPSCs-C). DPSCs-NCM had the same proliferation capacity as DPSCs-C. Flow cytometry (FACS) analysis indicated that both DPSCs-NCM and DPSCs-C were positive for mesenchymal stem cell markers at the same level but negative for hematopoietic cell markers. Moreover, both DPSCs-NCM and DPSCs-C could differentiate into osteogenic, chondrogenic, and adipogenic cells during culture in each induction medium. These results suggest that DPSCs-NCM may be mesenchymal stem cells. Therefore, our novel method might facilitate the less expensive cryopreservation of DPSCs, thereby providing suitable DPSCs for use in patients in future cell-based therapies.

Proliferation and differentiation of cultured MC3T3-E1 osteoblasts on surface-layer modified hydroxyapatite ceramic with acid and heat treatments.

Effects of functionally gradient calcium phosphate consisting of hydroxyapatite (HAP) and alpha-tricalcium phosphate (alpha-TCP) on proliferation and differentiation of osteoblasts were evaluated using MC3T3-E1 cells. There were no significant differences in the proliferation of MC3T3-E1 cells among HAP-alpha-TCP functionally gradient calcium phosphate, pure HAP, and cell culture plastic wells. mRNA expressions of type I collagen, alkaline phosphate, and osteocalcine were evaluated as indexes of initial; mid-stage, and late-stage osteoblastic differentiation. Basically, HAP-alpha-TCP functionally gradient calcium phosphate and pure HAP enhanced the expressions of the three markers when compared with that of cell culture plastic wells. For type I collagen and alkaline phosphate expressions, HAP-alpha-TCP functionally gradient calcium phosphate showed the same expression level as pure HAP. For osteocalcine expression, HAP-alpha-TCP functionally gradient calcium phosphate showed a higher level than pure HAP. We concluded, therefore, HAP-alpha-TCP functionally gradient calcium phosphate has good potential to be a bone filler material with high osteoconductivity.

Leptin promotes wound healing in the skin.

INTRODUCTION: Leptin, a 16 kDa anti-obesity hormone, exhibits various physiological properties. Interestingly, skin wound healing was proven to delay in leptin-deficient ob/ob mice. However, little is known on the mechanisms of this phenomenon. In this study, we attempted to elucidate a role of leptin in wound healing of skin. METHODS: Immunohistochemical analysis was performed to confirm the expression of the leptin receptor (Ob-R) in human and mouse skin. Leptin was topically administered to chemical wounds created in mouse back skin along with sustained-release absorbable hydrogel. The process of wound repair was histologically observed and the area of ulceration was measured over time. The effect of leptin on the proliferation, differentiation and migration of human epidermal keratinocytes was investigated. RESULTS: Ob-R was expressed in epidermal cells of human and mouse skin. Topical administration of leptin significantly promoted wound healing. Histological analysis showed more blood vessels in the dermal connective tissues in the leptin-treated group. The proliferation, differentiation/function and migration of human epidermal keratinocytes were enhanced by exogenous leptin. CONCLUSION: Topically administered leptin was proven to promote wound healing in the skin by accelerating proliferation, differentiation/function and migration of epidermal keratinocytes and enhancing angiogenesis around the wounded area. These results strongly suggest that topical administration of leptin may be useful as a treatment to promote wound healing in the skin.

Effects of apatite cements on proliferation and differentiation of human osteoblasts in vitro.

Although apatite cement (AC) and sintered hydroxyapatite (s-HAP) are known to show good osteoconductivity, it is not clear whether or not the degree of their osteoconductivity is the same. In addition, it has not been clarified whether or not it is dependent on the type of AC; conventional AC (c-AC), fast-setting AC (fs-AC) or anti-washout AC (aw-AC). The aim of this study was to investigate the effects of ACs on cultured human osteoblasts, as they may provide a useful index of osteoconductivity. Human osteoblasts were cultured on the surfaces of ACs and s-HAP, and were evaluated with respect to cell attachment, proliferation, and differentiation. We found that ACs and s-HAP showed similar cell attachment. No significant difference between ACs and s-HAP was found with respect to the proliferation of osteoblasts. In contrast, we found that the differentiation of osteoblasts was enhanced on the surface of ACs compared with that of s-HAP. However, there was no difference among the types of AC. We therefore concluded that AC may show better osteoconductivity than s-HAP, and that osteoconductivity of AC may be similar, regardless of the type of AC.

Effects of various sterilization methods on the setting and mechanical properties of apatite cement.

Sterilization capability is a necessary requirement for any material that is to be used in a medical application. Therefore, it is necessary for apatite cement (AC) to be sterilized. Because there is little information on the sterilization methods of AC, the aims of this investigation were to evaluate the effects of various sterilization methods, including steam, dry heat, ethylene oxide (EtO) gas, and gamma irradiation sterilizations, on the setting and mechanical properties of AC. In the case of steam sterilization, because AC powder aggregated before setting-time measurements, the setting time could not be measured. When the powder was sterilized by dry heat or EtO gas, the setting time was prolonged significantly and the wet diametral tensile strength (DTS) value decreased significantly. Therefore, sterilizations with steam, dry heat, or EtO gas were suggested to be inappropriate methods for AC. Accordingly, the following experiments focused on gamma sterilization. The setting time of AC was retarded with an increase in gamma irradiation dose. The wet DTS value decreased with the increase in gamma irradiation dose. There was no compositional change due to the gamma irradiation. The following tests were carried out in order to examine the effect of the gamma irradiation on the setting reaction of AC in detail. Tetracalcium phosphate [TTCP: Ca(4)(PO(4))(2)O] and dicalcium phosphate anhydrous (DCPA: CaHPO(4)) were separately irradiated, and the cements were produced with the use of irradiated powder and nonirradiated powder. Although the wet DTS value of AC produced from irradiated TTCP and nonirradiated DCPA decreased with increasing gamma irradiation dose, there was no significant difference. In contrast, the wet DTS value of AC produced from irradiated DCPA and nonirradiated TTCP significantly decreased with the increase in gamma irradiation dose. In conclusion, although the detailed mechanism of the delayed setting time and decreased DTS value was not clarified by the present study, it was found that gamma irradiation affected DCPA more than TTCP.

Effects of neutral sodium hydrogen phosphate on the setting property and hemostatic ability of hydroxyapatite putty as a local hemostatic agent for bone.

Hydroxyapatite (HAP) putty has been reported to have good hemostatic ability and excellent biocompatibility. Although the setting reaction of HAP putty and resulting transformation to HAP is the reason for this excellent biocompatibility, it also limits the handling period. In this study, the relationship between the setting reaction of HAP putty and its hemostatic ability was investigated, where neutral sodium hydrogen phosphate concentration and post-preparation time were used as indexes. A higher concentration of neutral sodium hydrogen phosphate was found to result in decreased hemostatic ability. The hemostatic ability of HAP putty decreased with time after its preparation; thus it was important to use HAP putty within 10 min after its preparation. The adhesive strength of HAP putty to bone increased with time. Therefore reliable hemostasis can be expected with HAP putty. Although the limited handling time is a drawback, HAP putty is thought to have a good potential as a hemostatic agent-it is highly reliable, and has a high hemostatic ability with excellent biocompatibility.

Leptin promotes wound healing in the oral mucosa.

INTRODUCTION: Leptin, a 16 kDa circulating anti-obesity hormone, exhibits many physiological properties. Recently, leptin was isolated from saliva; however, its function in the oral cavity is still unclear. In this study, we investigated the physiological role of leptin in the oral cavity by focusing on its effect on wound healing in the oral mucosa. METHODS: Immunohistochemical analysis was used to examine the expression of the leptin receptor (Ob-R) in human/rabbit oral mucosa. To investigate the effect of leptin on wound healing in the oral mucosa, chemical wounds were created in rabbit oral mucosa, and leptin was topically administered to the wound. The process of wound repair was histologically observed and quantitatively analyzed by measuring the area of ulceration and the duration required for complete healing. The effect of leptin on the proliferation, differentiation and migration of human oral mucosal epithelial cells (RT7 cells) was investigated using crystal violet staining, reverse transcription polymerase chain reaction (RT-PCR) and a wound healing assay, respectively. RESULTS: Ob-R was expressed in spinous/granular cells in the epithelial tissue and vascular endothelial cells in the subepithelial connective tissue of the oral mucosa. Topical administration of leptin significantly promoted wound healing and shortened the duration required for complete healing. Histological analysis of gingival tissue beneath the ulceration showed a denser distribution of blood vessels in the leptin-treated group. Although the proliferation and differentiation of RT7 cells were not affected by leptin, the migration of these cells was accelerated in the presence of leptin. CONCLUSION: Topically administered leptin was shown to promote wound healing in the oral mucosa by accelerating epithelial cell migration and enhancing angiogenesis around the wounded area. These results strongly suggest that topical administration of leptin may be useful as a treatment to promote wound healing in the oral mucosa.