Anin vitromodel of human oral explants to study early effects of radiation mucositis

Development of an Ex Vivo Functional Assay for Prediction of Irradiation Related Toxicity in Healthy Oral Mucosa Tissue

Radiotherapy in the head-and-neck area is one of the main curative treatment options. However, this comes at the cost of varying levels of normal tissue toxicity, affecting up to 80% of patients. Mucositis can cause pain, weight loss and treatment delays, leading to worse outcomes and a decreased quality of life. Therefore, there is an urgent need for an approach to predicting normal mucosal responses in patients prior to treatment. We here describe an assay to detect irradiation responses in healthy oral mucosa tissue. Mucosa specimens from the oral cavity were obtained after surgical resection, cut into thin slices, irradiated and cultured for three days. Seven samples were irradiated with X-ray, and three additional samples were irradiated with both X-ray and protons. Healthy oral mucosa tissue slices maintained normal morphology and viability for three days. We measured a dose-dependent response to X-ray irradiation and compared X-ray and proton irradiation in the same mucosa sample using standardized automated image analysis. Furthermore, increased levels of inflammation-inducing factors-major drivers of mucositis development-could be detected after irradiation. This model can be utilized for investigating mechanistic aspects of mucositis development and can be developed into an assay to predict radiation-induced toxicity in normal mucosa.

Biopsy-Derived Oral Keratinocytes – a Model to Potentially Test for Oral Mucosa Radiation Sensitivity

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Human oral keratinocytes – the key players in radiation mucositis in head and neck cancer treatment – are established ex vivo from patient-derived micro-biopsies.

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Individual radiosensitivity of primary oral keratinocytes is measured by a novel assay for cellular proliferation and spreading.

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The keratinocyte model also supports classical functional assays such as clonogenic survival and DNA double strand repair.

Purpose

To establish stable in vitro growth of keratinocytes from very small biopsy specimens and successfully apply new test systems to determine their radiosensitivity.

Materials and Methods

Oral mucosa biopsies (diameter: 1.7 mm) from 15 subjects were immobilized with custom-made cups onto culture plates. Outgrowing cells were tested for cytokeratin 5/14 and Ki67, expanded, radiated at different doses, and seeded onto circumscribed areas before being allowed to spread centrifugally. In this newly developed spreading assay, cell-covered areas were measured by image analysis. For statistical analysis, a linear mixed regression model was used; additionally, results were correlated to the radiation dose applied. Colony forming efficiency (CFE) was used to validate the results. DNA damage repair was analysed by gammaH2AX and 53BP1 foci quantification using immunofluorescence microscopy 24 h and 96 h after irradiation.

Results

Stable keratinocyte growth continued for up to 7 weeks in 14 biopsies. Cells spread reliably from an initial 16.6 mm² up to a median of 119.2 mm² (range: 54.4–290). Radiated cells spread to only 100.7 mm² (2 Gy; range: 55.3–266.7); 73.2 mm² (4 Gy; 15–240.4); 47 mm² (6 Gy; 2–111.9), and 22.7 mm² (8 Gy; 0–80). Similarly, CFE decreased from 0.223 (0 Gy) to 0.0028 (8 Gy). Using an individual donor as a random factor, cell spread correlated with CFE, where radiation dose was the main driver (decrease by 0.50, adjusted for area). Upon irradiation with 6 Gy, radiation-induced DNA damage was increased after 24 h in all samples, and even after 96 h in 5 out of 7 samples, as detected by a higher number of gammaH2AX/53BP1 foci in irradiated cells (mean 3.7 for 24 h; mean 0.6 for 96 h).

Conclusion

In vitro propagation of keratinocytes derived from a small biopsy is feasible. Radiation impairs cellular migration and proliferation, and the newly described spreading assay allows ranking for cellular radioresistance. The keratinocyte model also supports classical functional assays such as clonogenic survival and DNA double strand repair. The clinical relevance awaits upcoming investigations.

Radiation-induced Oral Mucositis in Brazilian Patients: Prevalence and Associated Factors

Aim: To determine the prevalence of radiation-induced oral mucositis (OM) and associated factors.

PATIENTS AND METHODS

A cross-sectional retrospective study was performed at a reference dental care center. The medical records of patients submitted to radiotherapy for the treatment of head and neck cancer were used to collect clinical and demographic variables. The data were submitted to descriptive analysis and multivariate Poisson regression with robust variance [p<0.05; 95% confidence intervaI (CI)].

RESULTS

Four hundred and thirteen patients were analyzed. The mean age was 55±14 years. The prevalence of OM in the overall sample was 41.9% and was higher among males (78.2%). The following variables were significantly associated with the outcome: radiation dose [prevalence ratio (PR)= 1.04; 95% CI=1.02-1.06]; concomitant chemotherapy (PR=1.48, 95% CI=1.05-2.08); oral candidiasis (PR=1.97, 95% CI=1.44-2.68); and osteoradionecrosis (PR=1.51, 95% CI=1.10-2.06).

CONCLUSION

Radiation-induced OM was associated with radiation dose, concomitant chemotherapy, oral candidiasis and osteoradionecrosis. The rate of OM underscores the importance of adequate oral care prior to treatment for head and neck cancer.

Phenotypic markers of oral keratinocytes seeded on two distinct 3D oral mucosa models

This study validates the use of a full-thickness oral mucosa model for in vitro studies with a collagen type I matrix, by comparison of this model with two other 3D oral mucosa models: human-sourced and porcine acellular dermal matrices (AlloDerm®/Strattice®, respectively). For the collagen matrix model, gingival fibroblasts were seeded either onto the dermal side of the AlloDerm® and Strattice® matrices or within the collagen matrices in complete culture medium (DMEM). For all scaffolds, DMEM was replaced every 24 h up to 72 h. For the full-thickness oral mucosa models, 72 h after fibroblast seeding, oral keratinocytes were seeded on the epidermal sides of AlloDerm® and Strattice® matrices or collagen matrices. All matrices and models were subjected to histological analysis, complementing phenotypic characterization by evaluation of glucose consumption, cell proliferation, gene expression and synthesis of growth factors. A higher fibroblast ratio was observed for the collagen matrix, in which the distribution of gingival fibroblasts was also more homogeneous. Metabolism, proliferation, and gene expression and synthesis of VEGF of these cells were also increased for the collagen matrix. All matrices provided a suitable substrate for oral keratinocytes adhesion, proliferation, and phenotypic expression; however, higher proliferation, stratification, and differentiation were noted when oral keratinocytes were seeded on the dermal matrices.

Tumor necrosis factor-alpha and interleukin-17 differently affects Langerhans cell distribution and activation in an innovative three-dimensional model of normal human skin

Among the several cytokines involved in the psoriasis pathogenesis, tumor necrosis factor (TNF)-alpha and interleukin (IL)-17 play a central role. Many biomolecular steps remain unknown due to difficulty to obtain psoriatic models. To investigate the effect of TNF-alpha and IL-17 on the ultrastructure, immunophenotype, and number of epidermal Langerhans cells (LCs), human skin explants (n=7) were cultured air-liquid interface in a Transwell system. Four different conditions were used: medium alone (control), medium added with 100 ng/ml TNF-alpha or 50 ng/ml IL-17 or a combination of both cytokines. Samples were harvested 24 and 48 h after cytokine addition and were frozen. Samples harvested at 24h were also processed for transmission electron microscopy (TEM). By immunofluorescence analysis with anti-human Langerin antibody (three experiments/sample) we calculated the percentage of LCs/mm(2) of living epidermis after 24 and 48 h of incubation (considering control as 100%). At 24h LC number was significantly higher in samples treated with both cytokines (216.71+15.10%; p<0.001) and in TNF-alpha (125.74+26.24%; p<0.05). No differences were observed in IL-17-treated samples (100.14+38.42%). After 48 h, the number of epidermal Langerin-positive cells in IL-17- and TNF-alpha treated samples slightly decreased (94.99+36.79% and 101.37+23% vs. their controls, respectively). With the combination of both cytokines epidermal LCs strongly decreased (120+13.36%). By TEM, upon TNF-alpha stimulus LCs appeared with few organelles, mostly mitochondria, lysosomes, and scattered peripherical BGs. Upon IL-17 stimulus, LCs showed a cytoplasm with many mitochondria and numerous BGs close to the perinuclear space and Golgi apparatus, but also at the periphery, at the beginning of the dendrites. The addition of both cytokines did not affect LC ultrastructure. Our study showed that IL-17 induced significant changes in LC ultrastructure, while the combination of both cytokines seems to have a strong chemo-attractant effect on epidermal LCs, supporting the relevance of investigating the interplay between LCs and pro-inflammatory cytokines in the ongoing of the disease.

A novel synthetic compound 3-amino-3-(4-fluoro-phenyl)-1H-quinoline-2,4-dione (KR22332) exerts a radioprotective effect via the inhibition of mitochondrial dysfunction and generation of reactive oxygen species

PURPOSE

Acute side effects of radiation such as oral mucositis are observed in most patients. Although several potential radioprotective agents have been proposed, no effective agent has yet been identified. In this study, we investigated the effectiveness of synthetic compound 3-amino-3-(4-fluoro-phenyl)-1H-quinoline-2,4-dione (KR22332) as a radioprotective agent.

MATERIALS AND METHODS

Cell viability, apoptosis, the generation of reactive oxygen species (ROS), mitochondrial membrane potential changes, and changes in apoptosis-related signaling were examined in human keratinocyte (HaCaT).

RESULTS

KR22332 inhibited irradiation-induced apoptosis and intracellular ROS generation, and it markedly attenuated the changes in mitochondrial membrane potential in primary human keratinocytes. Moreover, KR22332 significantly reduced the protein expression levels of ataxia telangiectasia mutated protein, p53, and tumor necrosis factor (TNF)-α compared to significant increases observed after radiation treatment.

CONCLUSION

KR22332 significantly inhibited radiation-induced apoptosis in human keratinocytes in vitro, indicating that it might be a safe and effective treatment for the prevention of radiation-induced mucositis.

Tissue-engineered mucosa is a suitable model to quantify the acute biological effects of ionizing radiation

The aim of this study was to evaluate the suitability of tissue-engineered mucosa (TEM) as a model for studying the acute effects of ionizing radiation (IR) on the oral mucosa. TEM and native non-keratinizing oral mucosa (NNOM) were exposed to a single dose of 16.5Gy and harvested at 1, 6, 24, 48, and 72h post-irradiation. DNA damage induced by IR was determined using p53 binding protein 1 (53BP1), and DNA repair was determined using Rad51. Various components of the epithelial layer, basement membrane, and underlying connective tissue were analyzed using immunohistochemistry. The expression of cytokines interleukin-1β (IL-1β) and transforming growth factor beta 1 (TGF-β1) was analyzed using an enzyme-linked immunosorbent assay. The expression of DNA damage protein 53BP1 and repair protein Rad51 were increased post-irradiation. The expression of keratin 19, vimentin, collage type IV, desmoglein 3, and integrins α6 and β4 was altered post-irradiation. Proliferation significantly decreased at 24, 48, and 72h post-irradiation in both NNOM and TEM. IR increased the secretion of IL-1β, whereas TGF-β1 secretion was not altered. All observed IR-induced alterations in TEM were also observed in NNOM. Based on the similar response of TEM and NNOM to IR we consider our TEM construct a suitable model to quantify the acute biological effects of IR.

Acute effects of cigarette smoke on three-dimensional cultures of normal human oral mucosa

CONTEXT

Human oral mucosa is the combustion chamber of cigarette, but scanty evidence is available about the early smoke effects.

OBJECTIVE

The present work aimed at evaluating from a morphological point of view whole smoke early effects on epithelial intercellular adhesion and keratinocyte terminal differentiation in a three-dimensional model of human oral mucosa.

MATERIALS AND METHODS

Biopsies of keratinized oral mucosa of healthy nonsmoking women (n = 5) were collected. After culturing in a Transwell system, one fragment of each biopsy was exposed to the smoke of one single cigarette; the remnant represented the internal control. The distribution of epithelial differentiation markers (keratin-10, K10, and keratin-14, K14, for suprabasal and basal cells respectively), desmosomes (desmoglein-1, desmoglein-3), tight junctions (occludin), adherens junctions (E-cadherin, β-catenin), and apoptotic cells (p53, caspase 3) were evaluated by immunofluorescence.

RESULTS

Quantitative analysis of K14 immunolabeling revealed an overexpression in the suprabasal layers as early as 3 h after smoke exposure, without impairment of the epithelial junctional apparatus and apoptosis induction.

DISCUSSION AND CONCLUSION

These results suggested that the first significant response to cigarette smoke came from the basal and suprabasal layers of the human oral epithelium. The considered model maintained the three-dimensional arrangement of the human mucosa in the oral cavity and mimicked the inhalation/exhalation cycle during the exposure to cigarette smoke, offering a good possibility to extrapolate the reported observations to humans.

Morphological evaluation of tongue mucosa in burning mouth syndrome

OBJECTIVE

The aim of the present study was to perform a morphological evaluation by immunofluorescence of biomarkers of keratinocyte intercellular adhesion, and of differentiation in the tongue mucosa of burning mouth syndrome patients (BMS), compared with a control group.

DESIGN

A prospective blinded evaluation of tongue mucosal specimens processed for light microscopy was performed. Intercellular adhesion was evaluated by investigating the expression of desmoglein 1, desmoglein 3, and of occludin. Keratin 10 and keratin 14 (markers of epithelial differentiation) were also evaluated, as keratin 16 (marker for activated keratinocytes after epithelial injury). Apoptotic cascade was investigated by p53 and activated caspase-3 expression. The basal membrane integrity was analysed through laminin immunoreactivity.

RESULTS

In both groups, a preserved three-dimensional architecture of the tongue was observed. Desmoglein 1 and desmoglein 3 epithelial distributions were similar in the desmosomes of patients and control subjects. Again, keratin 10 immunoreactivity and distribution pattern of keratin 14 in the epithelial compartment was similar in both groups. In control samples, keratin 16 immunoreactivity was scant throughout the epithelium with a punctuate and scattered cytoplasmic labelling. In contrast, in all BMS patients keratinocyte cytoplasm was homogeneously labelled for keratin 16, with a more intense staining than controls. Furthermore, keratin 16 staining progressively decreased proceeding towards the most superficial epithelial layers.

CONCLUSIONS

The results of this study are consistent with and support the clinically normal features of oral mucosa in BMS, and suggest that keratin 16 may be involved in the cell mechanisms underlying the syndrome occurrence.