Cell renewal in the oral mucosa and skin of the rat. I. Turnover time

Alveolar mucosal cell spheroids promote extraction socket healing and osseous defect regeneration

BACKGROUND

Alveolar mucosa could be a promising source of mesenchymal stem cells (MSCs) for regeneration therapeutics because it exhibits faster healing potential and can be easily collected with minimal periodontal disturbance. This study aimed to evaluate the potential of alveolar mucosal cell (AMC) spheroids for promoting extraction socket healing and calvarial osseous defect regeneration.

METHODS

AMCs were isolated from Sprague-Dawley rats. Antigenic and MSC surface marker expressions and trilineage differentiation capability were assessed. AMCs were then osteogenically stimulated (OAs) or unstimulated (UAs), self-aggregated to form spheroids, and encapsulated in gelatin hydrogel to fill rat extraction sockets or combined with freeze-dried bone graft (FDBG) to fill rat calvarial osseous defects. The outcome was assessed by gross observation, micro-CT imaging, and immunohistochemistry.

RESULTS

AMCs highly expressed MSC surface markers, showed weak antigenicity, and were capable of trilineage differentiation at Passage 3. In the extraction sockets, wound closure, socket fill, keratinization, and proliferative activities were accelerated in those with AMC spheroids treatment. Socket fill and maturation were further promoted by OA spheroids. In the calvarial osseous defects, the mineralized tissue ratio was promoted with AMC spheroids/FDBG treatment, and bone sialoprotein expression and cell proliferation were more evident with OA spheroids/FDBG treatment.

CONCLUSION

AMCs exhibited MSC properties with weak antigenicity. AMC spheroids promoted extraction socket healing, AMC spheroids/FDBG promoted calvarial osseous defect regeneration, and the outcomes were further enhanced by osteogenically stimulation of AMCs.

Angiogenesis Inhibitor Drug-induced Benign Migratory Glossitis in a Patient of Juvenile-onset Recurrent Respiratory Papillomatosis under Maintenance Therapy

Background

Benign migratory glossitis or geographic tongue is a chronic recurring inflammatory condition of the oral cavity. With its ephemeral characteristics, there has been reported literature showing its association with the administration of certain drugs including angiogenesis inhibitors. The antiangiogenic drugs act by selectively inhibiting the vascular endothelial growth factor (VEGF) signaling. It has been widely used as an adjunct and a maintenance agent for the treatment of various cancers.

Aims

This study aims to report probable characteristic oral mucosal changes in a patient with juvenile-onset recurrent respiratory papillomatosis (JORRP) under maintenance therapy with an antiangiogenesis drug.

Case description

The patient was presented with a burning sensation on having spicy food. This occurred after the completion of three cycles of bevacizumab infusion. It was associated with the appearance of migratory lesions over the tongue and evolved periods of remission and exacerbation. Clinical examination revealed lesions characteristic of the geographic tongue on the anterior two-thirds of the dorsal surface as well as the lateral surface of the tongue classified as type 2, according to Hume criteria. Oral examination revealed dental caries in relation to 52, 54, 62, 63, 74, and 85 teeth and grossly decayed 64. Topical lignocaine gel was instituted for symptomatic relief of the lesion. Full mouth rehabilitation with preventive and restorative therapeutic interventions was carried out.

Clinical significance and conclusion

The documented literature along with this report put forth a probable association of geographic tongue with the use of bevacizumab drugs which requires further detailed studies. These lesions generally require symptomatic treatment with assurance only. The etiology is poorly understood.

How to cite this article

Kalra N, Tyagi R, Khatri A, et al. Angiogenesis Inhibitor Drug-induced Benign Migratory Glossitis in a Patient of Juvenile-onset Recurrent Respiratory Papillomatosis under Maintenance Therapy. Int J Clin Pediatr Dent 2024;17(1):92-96.

Zonula occludens-1 distribution and barrier functions are affected by epithelial proliferation and turnover rates

Zonula occludens-1 (ZO-1) is a scaffolding protein of tight junctions, which seal adjacent epithelial cells, that is also expressed in adherens junctions. The distribution pattern of ZO-1 differs among stratified squamous epithelia, including that between skin and oral buccal mucosa. However, the causes for this difference, and the mechanisms underlying ZO-1 spatial regulation, have yet to be elucidated. In this study, we showed that epithelial turnover and proliferation are associated with ZO-1 distribution in squamous epithelia. We tried to verify the regulation of ZO-1 by comparing normal skin and psoriasis, known as inflammatory skin disease with rapid turnover. We as well compared buccal mucosa and oral lichen planus, known as an inflammatory oral disease with a longer turnover interval. The imiquimod (IMQ) mouse model, often used as a psoriasis model, can promote cell proliferation. On the contrary, we peritoneally injected mice mitomycin C, which reduces cell proliferation. We examined whether IMQ and mitomycin C cause changes in the distribution and appearance of ZO-1. Human samples and mouse pharmacological models revealed that slower epithelial turnover/proliferation led to the confinement of ZO-1 to the uppermost part of squamous epithelia. In contrast, ZO-1 was widely distributed under conditions of faster cell turnover/proliferation. Cell culture experiments and mathematical modelling corroborated these ZO-1 distribution patterns. These findings demonstrate that ZO-1 distribution is affected by epithelial cell dynamics.

Establishment of a chemical tongue injury-recovery mouse model

Tongue epithelium is one of the most proliferative and regenerative epithelia in our body. However, tongue stem cell research is hampered partly by the lack of optimal animal models to study tongue injury, repair, and regeneration. Here, we establish a novel chemically induced tongue injury-recovery mouse model. Focal application of sodium hydroxide for a limited time led to the denudation of suprabasal layers, leaving the basal layer. Time course study revealed that tongue epithelial cells robustly proliferate over one week after the tongue injury. Importantly, we demonstrated that our novel mouse model could be employed in the lineage tracing of the tongue stem cells under the injury and repair process and further showed that tongue stem cells proliferate faster and generate larger clones in the injury condition than in the steady state condition. Our data indicate the development of a novel chemically induced tongue injury-recovery mouse model for tongue stem cell research, which will significantly facilitate the preclinical study for the pathogenesis and treatment of caustic ingestion.

Maturation of the neonatal oral mucosa involves unique epithelium-microbiota interactions

Postnatal host-microbiota interplay governs mucosal homeostasis and is considered to have life-long health consequences. The intestine monolayer epithelium is critically involved in such early-life processes; nevertheless, the role of the oral multilayer epithelium remains ill defined. We demonstrate that unlike the intestine, the neonate oral cavity is immensely colonized by the microbiota that decline to adult levels during weaning. Neutrophils are present in the oral epithelium prenatally, and exposure to the microbiota postnatally further recruits them to the preamble neonatal epithelium by γδT17 cells. These neutrophils virtually disappear during weaning as the epithelium seals. The neonate and adult epithelium display distinct turnover kinetics and transcriptomic signatures, with neonate epithelium reminiscent of the signature found in germ-free mice. Microbial reduction during weaning is mediated by the upregulation of saliva production and induction of salivary antimicrobial components by the microbiota. Collectively, unique postnatal interactions between the multilayer epithelium and microbiota shape oral homeostasis.

Site-Specific Expression Pattern of PIWI-Interacting RNA in Skin and Oral Mucosal Wound Healing

The oral mucosa exhibits exceptional healing capability when compared to skin. Recent studies suggest that intrinsic differences in coding genes and regulatory small non-coding RNA (sncRNA) genes (e.g., microRNAs) may underlie the exceptional healing that occurs in the oral mucosa. Here, we investigate the role of a novel class of sncRNA-Piwi-interacting RNA (piRNA)-in the tissue-specific differential response to injury. An abundance of piRNAs was detected in both skin and oral mucosal epithelium during wound healing. The expression of PIWI genes (the obligate binding partners of piRNAs) was also detected in skin and oral wound healing. This data suggested that PIWI-piRNA machinery may serve an unknown function in the highly orchestrated wound healing process. Furthermore, unique tissue-specific piRNA profiles were obtained in the skin and oral mucosal epithelium, and substantially more changes in piRNA expression were observed during skin wound healing than oral mucosal wound healing. Thus, we present the first clue suggesting a role of piRNA in wound healing, and provide the first site-specific piRNA profile of skin and oral mucosal wound healing. These results serve as a foundation for the future investigation of the functional contribution(s) of piRNA in wound repair and tissue regeneration.

Differential microRNA profile underlies the divergent healing responses in skin and oral mucosal wounds

Oral mucosal wounds heal faster than skin wounds, yet the role of microRNAs in this differential healing has never been examined. To delineate the role of microRNAs in this site-specific injury response, we first compared the microRNAome of uninjured skin and oral mucosa in mice. A total of 53 tissue-specific microRNAs for skin and oral mucosa epithelium were identified. The most striking difference was the high abundance of miR-10a/b in skin (accounting for 21.10% of the skin microRNAome) as compared to their low expression in oral mucosa (2.87%). We further examined the dynamic changes of microRNAome throughout the time course of skin and oral mucosal wound healing. More differentially expressed microRNAs were identified in skin wounds than oral wounds (200 and 33, respectively). More specifically, miR-10a/b was significantly down-regulated in skin but not oral wounds. In contrast, up-regulation of miR-21 was observed in both skin and oral wounds. The therapeutic potential of miR-10b and miR-21 in accelerating wound closure was demonstrated in in vitro assays and in a murine skin wound model. Thus, we provided the first site-specific microRNA profile of skin and oral mucosal wound healing, and demonstrate the feasibility of a microRNA-based therapy for promoting wound closure.

Oral Complications in Patients with Advanced Cancer

Disturbances caused by lesions of the oral cavity play an important part in the alteration of the qualtity of life of cancer patients. The main complications affecting the oral cavity are infections (fungal, viral, bacterial), neutropenic ulcers, drug-induced stomatitis, dry mouth, and taste alteration. Most of the information available about these entities has been acquired in the cancer patient without advanced disease. The little known about the epidemiology and physiopathology of such lesions in the advanced phase of cancer is presented and approaches to management are suggested.

Effect of Transplantation of Bone Marrow Derived Mesenchymal Stem Cells and Platelets Rich Plasma on Experimental Model of Radiation Induced Oral Mucosal Injury in Albino Rats

Normal tissue damage following radiotherapy is still a major problem in cancer treatment. Therefore, the current work aimed at exploring the possible role of systemically injected bone marrow derived mesenchymal stem cells (BM-MSCs) and/or locally injected platelet rich plasma (PRP) in ameliorating the side effects of ionizing radiation on the rat's tongue. Twelve rats served as control group (N) and 48 rats received a single radiation dose of 13 Gy to the head and neck region; then, they were equally divided into 4 experimental groups: irradiated only (C), irradiated + MSCs (S), irradiated + (PRP) (P), and combined group (PS). Animal scarification occurred in 3 and 7 days after radiation. Then, tongues were dissected and examined histologically and for expression of bcl-2 by RT-PCR. Histological examination of the treated groups (S), (P), and (PS) revealed an obvious improvement in the histological structure of the tongue, compared to group (C), in addition to upregulated expression of bcl-2, indicating decreased apoptotic activity. Conclusion. BM-MSCs and PRP have shown positive effect in minimizing the epithelial atrophy of normal oral mucosa after regional radiotherapy, which was emphasized by decreasing apoptotic activity in these tissues. Nevertheless, combined use of BM-MSCs and PRP did not reveal the assumed synergetic effect in oral tissue protection.

Dormancy activation mechanism of oral cavity cancer stem cells

Radiotherapy and chemotherapy are targeted primarily at rapidly proliferating cancer cells and are unable to eliminate cancer stem cells in the G0 phase. Thus, these treatments cannot prevent the recurrence and metastasis of cancer. Understanding the mechanisms by which cancer stem cells are maintained in the dormant G0 phase, and how they become active is key to developing new cancer therapies. The current study found that the anti-cancer drug 5-fluorouracil, acting on the oral squamous cell carcinoma KB cell line, selectively killed proliferating cells while sparing cells in the G0 phase. Bisulfite sequencing PCR showed that demethylation of the Sox2 promoter led to the expression of Sox2. This then resulted in the transformation of cancer stem cells from the G0 phase to the division stage and suggested that the transformation of cancer stem cells from the G0 phase to the division stage is closely related to an epigenetic modification of the cell.

Oral epithelial stem cells in tissue maintenance and disease: the first steps in a long journey

The identification and characterization of stem cells is a major focus of developmental biology and regenerative medicine. The advent of genetic inducible fate mapping techniques has made it possible to precisely label specific cell populations and to follow their progeny over time. When combined with advanced mathematical and statistical methods, stem cell division dynamics can be studied in new and exciting ways. Despite advances in a number of tissues, relatively little attention has been paid to stem cells in the oral epithelium. This review will focus on current knowledge about adult oral epithelial stem cells, paradigms in other epithelial stem cell systems that could facilitate new discoveries in this area and the potential roles of epithelial stem cells in oral disease.

Adeno-associated virus expresses transgenes in hair follicles and epidermis

Adeno-associated virus (AAV) vectors are nonpathogenic, integrating DNA vectors capable of transducing dividing and nondividing cells with the potential of long-term expression. Evaluating this interesting vector system in the skin for the first time, we found that an AAV vector containing the lacZ gene (AAVlacZ) led to the expression of beta-galactosidase for more than 6 weeks following in vivo injection. Interestingly, expression was present not only in dividing and postmitotic epidermal keratinocytes but also in hair follicle epithelial cells and eccrine sweat glands. However, expression upon readministration was limited. Functional studies in swine using human erythropoietin were hampered by immunogenicity. Thus, AAV seems to be the only vector to date that efficiently targets hair follicle epithelial cells. It may also be useful when longer term expression in keratinocytes than that achievable by direct injection of plasmid DNA is desired.

Immunolocalization and adenoviral vector-mediated manganese superoxide dismutase gene transfer to experimental oral tumors

The anti-oxidant enzyme system protects cellular macromolecules against damage from reactive oxygen species. One component of this system, manganese superoxide dismutase (MnSOD), has also been shown to display tumor suppressor gene-like activity. The purpose of this study was to examine changes in MnSOD expression during hamster cheek pouch carcinogenesis, and the effects of MnSOD overexpression using an adenoviral vector. Tumor induction was carried out using 7,12-dimethylbenz[alpha]anthracene. Animals were killed at periodic intervals, and cheek pouch tissues were excised and examined for MnSOD expression by immunohistochemistry and digital image analysis. We observed a reduction in MnSOD expression as early as 2 weeks after the start of carcinogen application. Low MnSOD expression persisted until the end of the 23-week experimental period. Solid hamster cheek pouch carcinoma xenografts were then established in nude mice. An adenoviral vector encoding the human MnSOD gene was delivered to the xenografts by direct injection. We observed high, immediate expression of MnSOD in the xenografts that persisted for 10 days following cessation of viral construct delivery. Delivery of the MnSOD construct resulted in a maximal 50% reduction in tumor growth compared with untreated controls. Our results suggest that MnSOD may be a tumor suppressor gene in the hamster cheek pouch model system.

Efficient expression of naked plasmid DNA in mucosal epithelium: prospective for the treatment of skin lesions

Mucocutaneous gene therapy offers exciting new treatment modalities for skin lesions. Transient expression of naked plasmid DNA could be used as a local treatment of various skin lesions where the corresponding gene product (protein) has therapeutic or immunization potential. We analyzed the time course, magnitude, and histologic expression of the indicator plasmid DNA (pCMV:beta-Gal) in mucosal epithelium and papilloma lesions. Upon direct injection of naked plasmid DNA (20 microg) into oral mucosa, expression occurred at high local concentrations, up to 35-fold higher than in comparable injections into the epidermis. Due to the accelerated turnover of mucosal epithelium beta-galactosidase positive epithelial cells were detected in the basal and suprabasal layers as early as 3 h after injection, whereas only the most superficial mucosal layers demonstrated beta-galactosidase staining at 24 h post-injection. These biologic characteristics need to be taken into consideration when clinical applications of expressing naked plasmid DNA in epithelial tissues are considered.

A quantitative histometric murine in vivo model of radiation-induced oral mucositis

Gastrointestinal toxicity is a limiting factor in the effectiveness of cancer therapy. This toxicity is most visible in the mouth. There is considerable interest in developing strategies involving growth-factor manipulation of the epithelial stem cells to afford protection to these cells during treatment and/or to speed up the regenerative process following treatment. In order for this to be achieved, studies have to be undertaken in animal systems to demonstrate the proof of principle and determine optimal protocols. Here, a murine model for oral mucositis based on measurements of tissue cellularity at various times after exposure to radiation was used to investigate cytotoxicity. Several sites in the mouth were analysed and the pronounced circadian rhythm in these various epithelial sites determined. The circadian rhythm is important in that it would determine the timing of administration of growth factors. A microscope with an interactive computer was used to define areas of epithelium and lengths of basal layer, within which, and along which, the total number of cell nuclei was determined over a range of times following exposure to 10, 20 and 30 Gy of X-rays. For various practical reasons, the ventral surface of the tongue was identified as the most appropriate tissue to analyse. Here, measurements of cellularity reached minimum values between 6 and 8 days following 20 Gy. Labelling of S-phase cells demonstrated foci of regeneration and a burst of proliferative regeneration that commenced at about 5 days and reached peak values at 8 days after irradiation. This burst of regenerative proliferation was coincident with the minimum in tissue cellularity on about day 8. The lower dose of radiation (10 Gy) had minimal effects on cellularity: after the higher dose (30 Gy), there was clearly a more severe level of cellular depletion. This quantitative model of oral mucositis could be used to study the effects of other cytotoxics, including combinations of agents, and the potential role of growth factors to reduce the severity of the cellular depletion and to speed up the kinetics of regeneration.

Proliferation kinetics of mouse tongue epithelium under normal conditions and following single dose irradiation

Epithelial proliferation in the ventral surface of mouse tongue follows a pronounced circadian rhythm with a peak in mitotic activity at 10.00 a.m., preceded by a wave of DNA synthesis 8 h earlier. Nearly all cells (85%) pass through G2 and mitosis immediately after the S-phase; they subsequently divide again, usually after 2 or 3 days, indicating cohorts of cells with different G1-duration. The fraction of all nucleated cells comprised in one daily proliferation wave is about 20%, indicating a turnover time of the nucleated cell compartment of about 5 days. Cytotoxic injury by a single radiation dose of 20 Gy causes a steep decrease in cell counts, leading to complete denudation after 9-13 days. The difference between the latent period before ulceration and the tissue turnover time is explained by a marked proliferative activity of the doomed cells. The mitotic index increases steeply after day 1 to three times the control level, but most mitotic figures display gross abnormalities such as multipolar spindles or chromosome clumping. As a consequence cells with abnormal or multiple nuclei appear in the basal layers 3 days post irradiation and subsequently migrate to the upper layers. After denudation the epithelium rapidly becomes restored, with a phase of transient hyperplasia on days 13-14. Normal architecture is regained by day 15. Over the whole healing period the mitotic index remains at a high level, with most of the mitoses appearing histologically normal.

Issues in symptom control. Part 4. Oral complications in patients with advanced cancer

Disturbances caused by lesions of the oral cavity play an important part in the alteration of the quality of life of cancer patients. The main complications affecting the oral cavity are infections (fungal, viral, bacterial), neutropenic ulcers, drug-induced stomatitis, dry mouth, and taste alteration. Most of the information available about these entities has been acquired in the cancer patient without advanced disease. The little knowledge about the epidemiology and physiopathology of such lesions in the advanced phase of cancer is presented, and approaches to management are suggested.

Clinical characteristics and mechanisms involved in chemotherapy-induced oral ulceration

The clinical characteristics of chemotherapy-induced oral mucosal ulceration in a group of patients with acute leukemia were examined in detail in a long-term prospective clinical study. Differences in regional susceptibility within the mouth to the effects of chemotherapy were apparent. A reconstruction of the probable mechanisms involved is presented.

Rates of epithelial cell proliferation in the oral mucosa and skin of the tamarin monkey (Saguinus fuscicollis)

Epithelial cell proliferation was determined in skin and various regions of the oral cavity of the tamarin monkey and was expressed by means of two mitotic indices: the number of metaphases per mm of epithelial surface, and the number of metaphases per mm basement membrane. A significant correlation was obtained between the rank ordering of the different regions according to each index. Generally, the non-keratinized tissues of the oral cavity had mitotic rates higher than those of the keratinized oral regions, with the epidermis having the lowest value. The mitotic index also correlated significantly with epithelial thickness, with the thicker regions showing a higher rate of proliferation. These results represent the first comprehensive set of values for a primate and are in general agreement with data obtained from non-primate species; the values support the concept that the oral lining tissue turns over more rapidly than does the masticatory mucosa (Bhaskar, 1980).

Site-specific distribution of epithelial cell-surface carbohydrates in rat oral mucosa

The binding of two fluorescein-labelled lectins to epithelial cell surfaces was examined microspectrofluorimetrically in rat oral mucosa. Griffonia simplicifolia (GS-I-B4), which is specific for alpha-D-galactosyl end groups, labelled only basal cells, while Ulex europaeus (UEA-I), which is specific for alpha-L-fucosyl groups, labelled only spinous cells. The degree of binding of the lectins was dependent on the lectin concentration and the lectin pH. Different sites were examined. The labelling of basal cells by GS-I-B4 was maximal on the lateral borders of the tongue, and the fluorescence diminished medially; in contrast, the UEA-I labelling of the corresponding spinous cells was of undiminished intensity in the mediolateral direction across the entire lingual epithelium. There was a gradual increase in the binding of GS-I-B4 and UEA-I towards the posterior aspect of the tongue. In the mid-palate, there was stronger staining both of basal cells by GS-I-B4 and of spinous cells by UEA-I in the gingivae as compared to the centre of the palate. In anteroposterior sections of the fore- and mid-palate, the fluorescence intensity of basal cells was inversely related to that of spinous cells, with maximal labelling of basal cells by GS-I-B4 and corresponding minimal binding of spinous cells by UEA-I being evident at the crests of the transverse rugae, and the opposite pattern of staining by both lectins being noted at the bases of the rugae.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of liquid protein diet on collagen metabolism of the gingiva of young rats

The effects of liquid protein diet (LPD) on gingival collagen metabolism were evaluated in young rats. Experimental animals received a LPD, while pair-fed and ad libitum groups received a 20% casein diet. Prior to sacrifice at days 23, 35 and 48 post-partum, animals from each group were injected with C14-proline. Gingival tissues from the palate were excised and analyzed for collagen content and collagen synthesis. Results of body-weight changes at day 48 showed a 20% decrease in the LPD group, while pair-fed and ad libitum groups increased 47% and 267%, respectively. Collagen content per gram of gingiva was not significantly different among the three groups. Gingival collagen synthesis, however, did show significant differences among the three groups. It was concluded that while LPD effects on the overall body condition were profound, LPD exerts minimal effect on gingival collagen metabolism in young rats.

Significance of protein-energy malnutrition in dentistry: some suggestions for the profession

A sound nutritional state is extremely important for the maintenance of healthy oral tissues as well as the body in general. Dentistry is, by nature, related to nutrition and dental practitioners should inform their patients and the public of its importance. For this reason, dentists should have a much broader background in nutrition and food sciences.

Barrier properties of inflamed denture-loaded palatal mucosa to water

The barrier property of inflamed palatal mucosa to water has been studied in eight adult edentulous persons with a generalized denture stomatitis, by measuring the transmucosal water flow under varying osmotic gradients. Flow rates were registered gravimetrically in solute saturated filter paper discs after 10-min periods of mucosal contact, using solutions with an osmolarity of 0, 0.25, 0.30, 0.38, 0.50 and 0.75 osmol sucrose/l. The histology of the mucosal areas was evaluated from cytologic scrapings, and biopsy material from two persons. The inflow with use of pure water was 2.98 mg/cm2/10 min, being about three and a half times greater than through the intact mucosal surface. The point of isotony of the inflamed mucosa ranged between 0.30 and 0.36 with a mean value of 0.33 osmol/l, thus being of the same magnitude as in plasma and tissue fluid. The observations from the biopsy material were in accordance with earlier histological evidence from generalized denture stomatitis, indicating that the permeability properties of the inflamed mucosa belonged to epithelial cell layers located in the lower part of the spinous layer.