Transcriptional events in a clinical model of oral mucosal tissue injury and repair

Differential Temperature-Induced Responses in Immortalized Oral and Skin Keratinocytes

The epidermis of the skin and oral mucosa is constantly exposed to various environmental stimuli, including temperature changes. In particularly extreme conditions, such as excess heat or cold, significant injury may occur. Oral and skin keratinocytes exhibit tissue-specific differences in wound healing outcomes and the transcriptomic response to injury. This study investigated if skin and oral keratinocytes also have differential responses to heat- and cold-induced injury. Oral keratinocytes (TIGKs) were found to exhibit an enhanced viability following heat-induced injury compared to skin keratinocytes (HaCaTs). However, there were no discernible differences between skin and oral keratinocyte viability following cold-induced injury. To examine the transcriptomic differences between skin and oral keratinocytes in response to temperature-induced injury, we generated an mRNA-sequencing gene expression dataset. Differentially expressed genes (DEGs) including heat shock proteins (HSPs) were identified between HaCaTs and TIGKs at baseline (37 °C) and after heat- (60 °C) or cold-induced (-25 °C) injury. Our comparative analyses suggest that skin and oral keratinocytes exhibit transcriptomic differences at baseline and in their responses to heat or cold exposure. The enhanced heat tolerance of TIGKs relative to HaCaTs may be due to an advantageous expression of a subset of HSPs at baseline in TIGKs. Our work also provides a source of skin and oral keratinocyte gene expression data following heat- and cold-induced injury that can be used for future analyses.

Dynamics of Human Palatal Wound Healing and the Associated Microbiome

Wound healing in the oral mucosa is superior to that in the skin, with faster wound closure accompanied by reduced inflammation, less angiogenesis, and minimal scar formation. A well-characterized oral wound model is critical to investigating the mechanisms of oral wound closure and the efficacy of various clinical interventions. Currently, there are a few human oral wound models, although none of them are well characterized. In the present study, we describe and characterize a human hard palate wound healing model. A 3.5-mm circular and two 1 × 5-mm rectangular full-thickness wounds were made in the first and second molar region, 5 mm from the gingival margin, on the hard palate of human subjects. The circular wound was used to monitor wound closure and collect swabs for a microbiome analysis via 16s rRNA sequencing. The rectangular wounds were biopsied and the tissue was used to evaluate the gene expression of wound healing-related mediators by real-time polymerase chain reaction. Saliva was also collected to examine the protein levels of similar molecules by enzyme-linked immunosorbent assays. Circular wounds were nearly closed on day 7 after wounding. Significant changes in the gene expression of inflammatory cytokines, growth factors, antimicrobial peptides, and extracellular matrix-related molecules were identified in day 1 and day 3 wound tissue and compared with unwounded tissue on day 0. Changes in the protein levels of various mediators were limited in the saliva. In addition, alpha diversity, beta diversity, and differential microbiome analysis demonstrated significant changes in bacterial colonization of the wound surface over time compared with unwounded mucosa. In summary, we comprehensively characterize a human hard palate wound-healing model that details the dynamic changes of wound closure, levels of wound healing-related mediators in the wound and saliva, and the oral wound microbiome.

Transcriptional changes in human palate and skin healing

Most human tissue injuries lead to the formation of a fibrous scar and result in the loss of functional tissue. One adult tissue that exhibits a more regenerative response to injury with minimal scarring is the oral mucosa. We generated a microarray gene expression dataset to examine the response to injury in human palate and skin excisional biopsies spanning the first 7 days after wounding. Differential expression analyses were performed in each tissue to identify genes overexpressed or underexpressed over time when compared to baseline unwounded tissue gene expression levels. To attribute biological processes of interest to these gene expression changes, gene set enrichment analysis was used to identify core gene sets that are enriched over the time-course of the wound healing process with respect to unwounded tissue. This analysis identified gene sets uniquely enriched in either palate or skin wounds and gene sets that are enriched in both tissues in at least one time point after injury. Finally, a cell type enrichment analysis was performed to better understand the cell type distribution in these tissues and how it changes over the time course of wound healing. This work provides a source of human wound gene expression data that includes two tissue types with distinct regenerative and scarring phenotypes.

Gene expression profiles of oral soft tissue-derived fibroblast from healing wounds: correlation with clinical outcome, autophagy activation and fibrotic markers expression

AIM

Our aim was to evaluate gene expression profiling of fibroblasts from human alveolar mucosa (M), buccal attached gingiva (G) and palatal (P) tissues during early wound healing, correlating it with clinical response.

MATERIALS AND METHODS

M, G and P biopsies were harvested from six patients at baseline and 24 hr after surgery. Clinical response was evaluated through Early wound Healing Score (EHS). Fibrotic markers expression and autophagy were assessed on fibroblasts isolated from those tissues by Western blot and qRT-PCR. Fibroblasts from two patients were subjected to RT² profiler array, followed by network analysis of the differentially expressed genes. The expression of key genes was validated with qRT-PCR on all patients.

RESULTS

At 24 hr after surgery, EHS was higher in P and G than in M. In line with our clinical results, no autophagy and myofibroblast differentiation were observed in G and P. We observed significant variations in mRNA expression of key genes: RAC1, SERPINE1 and TIMP1, involved in scar formation; CDH1, ITGA4 and ITGB5, contributing to myofibroblast differentiation; and IL6 and CXCL1, involved in inflammation.

CONCLUSIONS

We identified some genes involved in periodontal soft tissue clinical outcome, providing novel insights into the molecular mechanisms of oral repair (ClinicalTrial.gov-NCT04202822).

Myofibroblast Gene Expression Profile after Tooth Extraction in the Rabbit

After tooth extraction, the alveolar bone tends to shrink in volume, especially on the vestibular side. The role of myofibroblasts in bone remodeling has not been sufficiently investigated. The aim of the present study was to explore the gene expression related to myofibroblasts presence and activity during a 90-day healing period after tooth extraction. The study included 36 rabbits, and a single tooth extraction was performed on each rabbit. The extractive sockets were randomly distributed to natural healing or to scarification of the wound. The sacrifices were staggered in such a manner that animals contributed with sockets representing 2, 7, 15, 30, 60, and 90 days of healing. Nanostring technology was used to evaluate the expression of a wide panel consisting in 148 genes related to the activation, induction, and suppression of myofibroblasts, socket microenvironment, and autophagy. We found that the expression profile of this custom panel was time-related. The post-extractive socket was subjected to significant gene expression changes after 15 days: the genes involved in the induction of myofibroblasts were up-regulated in the first 15-day period and down-regulated during the rest of the follow-up. The study suggested that myofibroblasts play a major role in the immediate 15-day period following tooth extraction.

Early Wound Healing Score (EHS): An Intra- and Inter-Examiner Reliability Study

The early wound healing score (EHS) was introduced to assess early wound healing of periodontal soft tissues after surgical incision. The purpose of this study is to evaluate the intra- and inter-examiner reliability of the EHS. Six examiners with different levels of training and clinical focus were enrolled. Each examiner was trained on the use of the EHS before starting the study. Thereafter, 63 photographs of three different types of surgical incisions taken at day 1, 3 or 7 post-operatively were independently evaluated according to the proposed assessment method. A two-way random intra-class correlation coefficient (ICC) and 95% confidence interval (CI) were used to analyze the intra- and inter-examiner reliability for the EHS. The inter-examiner reliability for the EHS was 0.828 (95% CI: 0.767–0.881). The intra-examiner reliability ranged between 0.826 (95% CI: 0.728–0.891) and 0.915 (95% CI: 0.856–0.950). The results therefore show an “almost perfect agreement” for intra- and inter-examiner reliability. The EHS provides a system for reproducible repeated ratings for the early healing assessment of incisions of periodontal soft tissues. Even when used by examiners with different clinical experience and specialty, it shows a high correlation coefficient.

The Spectrum of Scarring in Craniofacial Wound Repair

Fibrosis is intimately linked to wound healing and is one of the largest causes of wound-related morbidity. While scar formation is the normal and inevitable outcome of adult mammalian cutaneous wound healing, scarring varies widely between different anatomical sites. The spectrum of craniofacial wound healing spans a particularly diverse range of outcomes. While most craniofacial wounds heal by scarring, which can be functionally and aesthetically devastating, healing of the oral mucosa represents a rare example of nearly scarless postnatal healing in humans. In this review, we describe the typical wound healing process in both skin and the oral cavity. We present clinical correlates and current therapies and discuss the current state of research into mechanisms of scarless healing, toward the ultimate goal of achieving scarless adult skin healing.

Autophagy activation is required for myofibroblast differentiation during healing of oral mucosa

AIM

It is known that periodontal tissues heal faster that skin, and gingiva in particular heal without scar formation. The mechanisms regulating this behaviour are still unclear. The aim of our work was to compare wound healing in oral mucosa and gingiva, investigating the role of α-smooth muscle actin (αSMA)-expressing myofibroblasts and autophagy.

MATERIALS AND METHODS

Biopsies were obtained from seven patients immediately before and 24 hr after vertical releasing incision in oral mucosa and attached gingiva. Both whole biopsies and primary cultures of fibroblasts derived from the same tissues were subjected to immunofluorescence, Western blot and quantitative real-time PCR analyses.

RESULTS

We demonstrated that in oral mucosa, characterized by partially fibrotic outcome during repair, the activation of autophagy determined an increase in αSMA and collagen 1a1 production. Conversely, wound healing did not stimulate autophagy in attached gingiva, and subsequently, no increase in myofibroblast differentiation and collagen deposition could be seen, thus justifying its scarless outcome.

CONCLUSIONS

The elucidation of the differential regulation of autophagy in periodontal tissues and its correlation with myofibroblast differentiation and fibrotic outcome could allow the identification of new molecules involved in periodontal healing and the development of new surgical approaches for periodontal treatment that could improve the outcome of postoperative wounds.

Human gingiva transcriptome during wound healing

OBJECTIVES

To investigate the gene expression profile of human gingiva following surgical wounding.

METHODS

Ten volunteers had one side of the palate wounded. Five days later, biopsies were harvested from both wounded (healing gingiva) and contra-lateral site (normal gingiva). Tissue samples were processed for gene expression (RNA-Seq, real-time PCR) and immunohistochemistry. Gene set enrichment/pathway analysis was also performed.

RESULTS

Seven hundred genes were significantly differentially expressed in healing gingiva. Among genes with >twofold change (FC) in expression, 399 genes were up-regulated and 88 down-regulated, several not previously reported expressed in gingiva. Most increased in expression (≥30-FC) were MMP1, CCL18, SPP1, MUC21, CTHRC1, MMP10, and SERPINE1; most decreased (≥7-FC) were COCH, SIAH3, MT4, IGFL3, KY, and SYT16. Real-time PCR confirmed significantly changed mRNA levels for selective genes tested. Gene set enrichment analysis revealed several significantly enriched biological pathways. Immunohistochemistry confirmed protein expression of MUC21, CTHRC1, CTGF, and SYT16 in normal and healing gingiva.

CONCLUSIONS

This first comprehensive analysis of the human gingival transcriptome during surgical wound healing offers novel insights into the participating molecular and biological mechanisms. The present results could serve as basis for future investigations into gingival wound healing following surgical, traumatic, or other type of injury.

Differential Apoptosis in Mucosal and Dermal Wound Healing

Objectives: Dermal and mucosal healing are mechanistically similar. However, scarring and closure rates are dramatically improved in mucosal healing, possibly due to differences in apoptosis. Apoptosis, nature's preprogrammed form of cell death, occurs via two major pathways, extrinsic and intrinsic, which intersect at caspase3 (Casp3) cleavage and activation. The purpose of this experiment was to identify the predominant pathways of apoptosis in mucosal and dermal wound healing. Approach: Wounds (1 mm biopsy punch) were made in the dorsal skin (n=3) or tongue (n=3) of female Balb/C mice aged 6 weeks. Wounds were harvested at 6 h, 24 h, day 3 (D3), D5, D7, and D10. RNA was isolated and analyzed using real time reverse transcriptase-polymerase chain reaction. Expression levels for genes in the intrinsic and extrinsic apoptotic pathways were compared in dermal and mucosal wounds. Results: Compared to mucosal healing, dermal wounds exhibited significantly higher expression of Casp3 (at D5; p<0.05), Casp7 (at D5; p<0.05), Trp53 (at 24 h and D5; p<0.05), Tnfrsf1b (at 24 h; p<0.05), FasR (at 24 h, D5, and D7; p<0.05), and Casp8 (at 24 h; p<0.05) and significantly lower gene expression of Tradd (at 24 h; p<0.05). Innovation: Our observations indicate differential execution of apoptosis in oral wound healing compared to skin. Conclusion: Expression patterns of key regulators of apoptosis in wound healing indicate that apoptosis occurs predominantly through the intrinsic pathway in the healing mucosa, but predominantly through the extrinsic pathway in the healing skin. The identification of differences in the apoptotic pathways in skin and mucosal wounds may allow the development of therapeutics to improve skin healing.

Nasal epithelial repair and remodeling in physical injury, infection, and inflammatory diseases

PURPOSE OF REVIEW

To summarize the current knowledge of cellular and molecular mechanisms of nasal epithelial repair and remodeling during physical and pathophysiological conditions.

RECENT FINDINGS

Nasal epithelial repair and remodeling is a highly organized and well coordinated process, involving inflammation, proliferation, differentiation, matrix deposition, and remodeling, and is regulated by a wide variety of growth factors and cytokines. From the in-vivo and in-vitro studies conducted in both human and animal models, undifferentiated basal cells (progenitors) are able to migrate from adjacent epithelium, spread over the denuded basement membrane, and proliferate in injured regions (self-renewal) in necessary (homeostasis) or excessive (hyperplasia) degree. Progenitor cells reorient to an apical-basal polarity, and progressively differentiate into ciliated and nonciliated columnar cells and goblet cells, reconstituting a functional respiratory epithelium after several weeks. This recovery process can be observed during various types and severity of injury, and also in common nasal diseases, including acute viral, allergic, and nonallergic rhinitis, as well as chronic rhinosinusitis with and without nasal polyps.

SUMMARY

Although nearly 10 000 articles about nasal epithelium have been published in the last decade, the mechanisms underlying the nasal epithelial repair are still understood at only a superficial descriptive level. In order to advance rhinology to the next level of a comprehensive knowledge of the orchestrated genetic and molecular processes acting during epithelial repair, combined clinical and experimental studies using sophisticated investigational plans to elucidate the functions of both the protein-coding and regulatory portions of the human genome are required.

Gene expression signatures: a new approach to understanding the pathophysiology of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a complex inflammatory disease with variable disease manifestation. Though external risk factors are associated with development and/or persistence of CRS, the host mucosal response is also important, as nasal epithelium acts as a physical and immune barrier. Under inflammatory stress, the nasal epithelium can undergo injury, followed by a rapid remodeling response ranging from epithelial hyperplasia, to goblet-cell metaplasia, to denudation, loss of cilia, fibrosis, and basement membrane thickening. Identification of gene expression signatures and molecular pathways in CRS pathogenesis have now begun to contribute significantly to a better understanding of the genetic and molecular alterations underlying CRS development and progression. Genetic studies are especially illuminating when multiple gene variants synergize within a permissive environmental context, and are expected to guide development of more effective therapeutic targets for CRS treatment.

Microarray analyses of peripheral whole blood cells from ulcerative colitis patients: effects of leukocytapheresis

Complementary DNA microarray technology allows the simultaneous analysis of the expression of hundreds to thousands of genes. We applied this technique to clarify the molecular mechanisms underlying the therapeutic effects of leukocytapheresis (LCAP) therapy in patients with ulcerative colitis (UC). A 776-gene microarray analysis was performed using whole blood cells from six normal subjects and six patients with active UC who had undergone filtration LCAP. Widespread gene upregulation was observed in patients with UC, compared with normal subjects. After LCAP, genes with proinflammatory actions, such as CD97, CD74, human leukocyte antigen-DRβ1 and -DP light chain, were downregulated, while genes responsible for antimicrobial actions, such as neutrophil gelatinase-associated lipocalin, and acute phase reactions, such as haptoglobin α1S and α1-acid glycoprotein, were upregulated. In conclusion, we identified several genes expressed in the whole blood cells of UC patients as well as the transcriptional events following LCAP. Following LCAP, the gene profile shifted toward a pattern indicating disease improvement. These results suggest a basis for the molecular mechanisms leading to the therapeutic effects of LCAP and also indicate new therapeutic targets, providing important prognostic information.

Osteoblastic and cytokine gene expression of implant-adherent cells in humans

OBJECTIVES

Implant surface topography is a key determinant affecting osteoblastic differentiation and cell-cell signaling of implant-adherent cells.

MATERIALS AND METHODS

To assess the early osteoinductive and cell-cell signaling events in adherent cells, commercially pure titanium implants (2.2 × 5 mm) with nanotopography (HF-treated TiO2 grit-blasted) were compared with micron-scale topography TiO2 grit-blasted (micron-scale, control) implants in vivo. Six implants (n = 3/surface) were placed in 10 systemically healthy subjects and removed by reverse threading at 1, 3, and 7 days. Gene expression profiles of adherent cells were interrogated using low-density RT-PCR arrays.

RESULTS

Osteoinduction was not observed at day 1 on either surface. At 3 days, elevated levels of BMP6, osteopontin, and osterix (OSX) were observed in RNA of cells adherent to both micron-scale and nanotopography surfaces. Both surfaces supported osteoinductive gene expression at 7 days; however, modest elevations of most mRNAs and significantly higher OSX mRNA levels were measured for cells adhered to nanotopography implants. Further, chemokine and cytokine profiles including CXCL10, CXCL14, IL-9, IL-22, and TOLLIP were upregulated on nanotopographic surfaces as compared with microtopographic surfaces.

CONCLUSIONS

Implants with superimposed nanoscale topography generate a greater induction of genes linked to osteogenesis and cell-cell signaling during the early phases of osseointegration.

Effect of growth factors on the migration of equine oral and limb fibroblasts using an in vitro scratch assay

The objective of this study was to determine the effect of platelet derived growth factor BB (PDGF), epidermal growth factor (EGF), transforming growth factor β1 (TGFβ1), insulin like growth factor-1 (IGF-1) and fibroblast growth factor-2 (FGF-2) on the proliferation and migration of equine oral mucosa and leg skin fibroblast cell lines, using an in vitro scratch assay. Fibroblasts from the two sites were firstly grown to confluence and then an area of cells removed (cell void area). Cell migration alone (with the addition of the mitosis inhibitor mitomycin-C to the culture media) and proliferation and migration combined (without mitomycin-C) into the cell void area were observed at 0, 5, 10, 24 and 36 h. The presence of mitomycin-C in the culture media significantly slowed the closure of the cell void area, as mitosis was inhibited. For the oral cells only, TGFβ1 significantly slowed both migration (with mitomycin-C) and proliferation and migration combined (without mitomycin-C). For the limb cells only, both PDGF and FGF-2 significantly increased fibroblast proliferation and migration combined (without mitomycin-C). For both cell types, EGF significantly reduced migration (with mitomycin-C). IGF-1 had no effect on any of the parameters measured. It was concluded that TGFβ1, PDGF and FGF-2 have differential effects on the proliferation and migration of equine oral and limb fibroblasts. These differences in fibroblast responses to growth factors may in part form the basis of the different clinical outcomes for oral and limb wounds.

Bisphosphonates inhibit expression of p63 by oral keratinocytes

Osteonecrosis of the jaw (ONJ), a side-effect of bisphosphonate therapy, is characterized by exposed bone that fails to heal within eight weeks. Healing time of oral epithelial wounds is decreased in the presence of amino-bisphosphonates; however, the mechanism remains unknown. We examined human tissue from individuals with ONJ and non-bisphosphonate-treated control individuals to identify changes in oral epithelium and connective tissue. Oral and intravenous bisphosphonate-treated ONJ sites had reduced numbers of basal epithelial progenitor cells, as demonstrated by a 13.8±1.1% and 31.9±5.8% reduction of p63 expression, respectively. No significant differences in proliferation rates, vessel density, or macrophage number were noted. In vitro treatment of clonal and primary oral keratinocytes with zoledronic acid (ZA) inhibited p63, and expression was rescued by the addition of mevalonate pathway intermediates. In addition, both ZA treatment and p63 shRNA knock-down impaired formation of 3D Ex Vivo Produced Oral Mucosa Equivalents (EVPOME) and closure of an in vitro scratch assay. Analysis of our data suggests that bisphosphonate treatment may delay oral epithelial healing by interfering with p63-positive progenitor cells in the basal layer of the oral epithelium in a mevalonate-pathway-dependent manner. This delay in healing may increase the likelihood of osteonecrosis developing in already-compromised bone.

Positional differences in the wound transcriptome of skin and oral mucosa

Background

When compared to skin, oral mucosal wounds heal rapidly and with reduced scar formation. Recent studies suggest that intrinsic differences in inflammation, growth factor production, levels of stem cells, and cellular proliferation capacity may underlie the exceptional healing that occurs in oral mucosa. The current study was designed to compare the transcriptomes of oral mucosal and skin wounds in order to identify critical differences in the healing response at these two sites using an unbiased approach.

Results

Using microarray analysis, we explored the differences in gene expression in skin and oral mucosal wound healing in a murine model of paired equivalent sized wounds. Samples were examined from days 0 to 10 and spanned all stages of the wound healing process. Using unwounded matched tissue as a control, filtering identified 1,479 probe sets in skin wounds yet only 502 probe sets in mucosal wounds that were significantly differentially expressed over time. Clusters of genes that showed similar patterns of expression were also identified in each wound type. Analysis of functionally related gene expression demonstrated dramatically different reactions to injury between skin and mucosal wounds. To explore whether site-specific differences might be derived from intrinsic differences in cellular responses at each site, we compared the response of isolated epithelial cells from skin and oral mucosa to a defined in vitro stimulus. When cytokine levels were measured, epithelial cells from skin produced significantly higher amounts of proinflammatory cytokines than cells from oral mucosa.

Conclusions

The results provide the first detailed molecular profile of the site-specific differences in the genetic response to injury in mucosa and skin, and suggest the divergent reactions to injury may derive from intrinsic differences in the cellular responses at each site.

Chronic tympanic membrane perforation: a better animal model is needed

Developments in the treatment of chronic tympanic membrane perforation have been hindered by the lack of an ideal animal model. It is not appropriate to test such treatments on acute perforations as the majority of these heal spontaneously. An ideal animal model would be one that most closely resembles the human clinical situation. It should be inexpensive, readily available, and easy to create. There have been a number of attempts to create a chronic tympanic membrane perforation model with limited success. All published attempts at chronic tympanic membrane perforations have been reviewed and the limitations of each model are discussed. A number of areas for research exist for further developing a chronic tympanic membrane perforation model. These areas include a perforation model in the presence of bacteria and eustachian tube dysfunction. Understanding the molecular and genetic mechanisms of chronic otitis media and potential treatments will also be useful.

Histopathological and lymphangiogenic parameters in relation to lymph node metastasis in early stage oral squamous cell carcinoma

PURPOSE

Lymph node metastasis from oral squamous cell carcinoma (SCC) correlates with a poor prognosis. Therefore, accurate assessment of lymph node status is crucial in treatment planning. Furthermore, prediction of delayed neck metastasis (DNM), especially in early stage tumors with a clinically negative (N0) neck, will determine the need for neck dissection or irradiation. In this study, we assess various clinical, histopathological and lymphangiogenic parameters in early stage oral SCC and their association with DNM.

MATERIALS AND METHODS

Clinical, histological, and immunohistochemical analyses were undertaken for 29 patients with T1N0M0 or T2N0M0 oral SCC affecting the tongue or floor of mouth and correlated with the development of DNM.

RESULTS

Tumor thickness, nuclear pleomorphism, pattern of invasion, and immunohistochemical expression of the lymphangiogenesis-associated molecules VEGFR-3 and VEGF-C were associated with DNM.

CONCLUSIONS

Analysis of these parameters may help to identify patients who would benefit from a neck dissection or irradiation by predicting the likelihood of lymph node metastasis.

Evening exposure to blue light stimulates the expression of the clock genePER2in humans

We developed a non-invasive method to measure and quantify human circadian PER2 gene expression in oral mucosa samples and show that this gene oscillates in a circadian (= about a day) fashion. We also have the first evidence that induction of human PER2 expression is stimulated by exposing subjects to 2 h of light in the evening. This increase in PER2 expression was statistically significant in comparison to a non-light control condition only after light at 460 nm (blue) but not after light exposure at 550 nm (green). Our results indicate that the non-image-forming visual system is involved in human circadian gene expression. The demonstration of a functional circadian machinery in human buccal samples and its response to light opens the door for investigation of human circadian rhythms at the gene level and their associated disorders.