Smad2 decelerates re-epithelialization during gingival wound healing

PRF Lysates Enhance the Proliferation and Migration of Oral Squamous Carcinoma Cell Lines

Platelet-rich fibrin (PRF) is an autologous fibrin-rich matrix where activated platelets and leucocytes accumulate. PRF has a wide spectrum of clinical indications with the overall aim of supporting tissue regeneration which in dentistry includes the healing of healthy oral mucosa with epithelial cells. In oral squamous cell carcinoma lesions, however, epithelial cells undergo malignant transformation, indicated by their unrestricted proliferation and migration potential, which should not be further enhanced by a wound-healing formula. Yet, little is known about how oral squamous cell carcinomas respond to PRF lysates. The aim of the present study was, therefore, to test the capacity of PRF lysates to change the transcriptome of HSC2 oral squamous carcinoma cells and perform bioassays to support the findings. Based on the RNAseq analysis, PRF lysates caused an increase in the genes functionally linked to cell replication and migration. In support of this screening approach, PRF lysates enhanced the proliferation of HSC2 oral squamous carcinoma cells, as indicated by 3[H]-thymidine incorporation, cell counting, and the expression of proliferation-related genes. Moreover, PRF lysates sped up cell migration in a scratch assay requiring actin polymerization. Taken together, our data showing that PRF lysates are mitogenic and stimulate motility of oral squamous carcinoma cell lines could be an indication that treatment with PRF in cases of oral carcinoma should be carefully considered.

Role of Inhibitor SMADs in Stage 3 Grade B periodontitis before and after periodontal treatment

OBJECTIVE

This study aimed to examine the levels of transforming growth factor-beta (TGF-β) and inhibitory-Smads (I-Smads) in saliva and gingival crevicular fluid (GCF) in patients with Stage 3 Grade B periodontitis before and after non-surgical periodontal treatment.

BACKGROUND

Recently, it has been stated that Smads play an active role in all conditions where TGF-β is involved, including periodontal inflammation.

METHODS

Twenty healthy participants (control) and 20 patients with Stage 3, Grade B periodontitis were recruited. GCF and saliva samples and clinical periodontal recordings were investigated at the baseline and 1 month after treatment. TGF-β and I-Smads (Smads 6 and 7) were determined by ELISA.

RESULTS

Salivary Smad6 and Smad7 levels were significantly lower in the periodontitis group than healthy controls (p < .05), while there was no difference in salivary TGF-β levels between groups at baseline (p > .05). The total amounts and concentrations of GCF TGF-β, Smad6, and Smad7 were significantly lower in the periodontitis group than healthy controls at baseline (p < .05), and then decreased in concentration levels with treatment (p < .001). Positive correlations were found between total amounts and concentrations of GCF TGF-β, Smad6, and Smad7 (p < .05).

CONCLUSION

Our findings revealed that Smad6 and Smad7 in GCF and saliva decreased in periodontitis and then increased after periodontal treatment. Our study suggests that I-Smads act in parallel with TGF-β in periodontal inflammation and may have a role in the development of periodontitis.

Emerging Insights into Keratin 16 Expression during Metastatic Progression of Breast Cancer

Simple Summary

The mechanisms leading to tumor metastasis remain poorly understood, and therefore, phenotyping of circulating tumor cells from cancer patients may contribute to translating these mechanisms. In in silico analysis, high expression of keratin 16 was associated with higher tumor aggressiveness. According to our results, keratin 16 is a metastasis-associated protein that promotes EMT and acts as a positive regulator of cellular motility by reorganizing the actin cytoskeleton, which is the driving force behind disrupting intercellular adhesion and directional migration. In metastatic breast cancer patients, circulating tumor cells expressing keratin 16 were associated with shorter relapse-free survival. This is an important issue for future research to determine the exact function of keratin 16 in tumor dissemination and metastasis development by analyzing keratin 16 status in disseminating tumor cells. Furthermore, gaining a better knowledge of keratin 16’s biology would give crucial mechanistic insights that might lead to a unique treatment option.

Abstract

Keratins are the main identification markers of circulating tumor cells (CTCs); however, whether their deregulation is associated with the metastatic process is largely unknown. Previously we have shown by in silico analysis that keratin 16 (KRT16) mRNA upregulation might be associated with more aggressive cancer. Therefore, in this study, we investigated the biological role and the clinical relevance of K16 in metastatic breast cancer. By performing RT-qPCR, western blot, and immunocytochemistry, we investigated the expression patterns of K16 in metastatic breast cancer cell lines and evaluated the clinical relevance of K16 expression in CTCs of 20 metastatic breast cancer patients. High K16 protein expression was associated with an intermediate mesenchymal phenotype. Functional studies showed that K16 has a regulatory effect on EMT and overexpression of K16 significantly enhanced cell motility (p < 0.001). In metastatic breast cancer patients, 64.7% of the detected CTCs expressed K16, which was associated with shorter relapse-free survival (p = 0.0042). Our findings imply that K16 is a metastasis-associated protein that promotes EMT and acts as a positive regulator of cellular motility. Furthermore, determining K16 status in CTCs provides prognostic information that helps to identify patients whose tumors are more prone to metastasize.

The Emerging Role of microRNA in Periodontitis: Pathophysiology, Clinical Potential and Future Molecular Perspectives

During the last few decades, it has been established that messenger ribonucleic acid (mRNA) transcription does not inevitably lead to protein translation, but there are numerous processes involved in post-transcriptional regulation, which is a continuously developing field of research. MicroRNAs (miRNAs) are a group of small non-coding RNAs, which negatively regulate protein expression and are implicated in several physiological and pathological mechanisms. Aberrant expression of miRNAs triggers dysregulation of multiple cellular processes involved in innate and adaptive immune responses. For many years, it was thought that miRNAs acted only within the cell in which they were synthesised, but, recently, they have been found outside cells bound to lipids and proteins, or enclosed in extracellular vesicles, namely exosomes. They can circulate throughout the body, transferring information between cells and altering gene expression in the recipient cells, as they can fuse with and be internalised by the recipient cells. Numerous studies on miRNAs have been conducted in order to identify possible biomarkers that can be used in the diagnosis of periodontal disease. However, as therapeutic agents, single miRNAs can target several genes and influence multiple regulatory networks. The aim of this review was to examine the molecular role of miRNAs and exosomes in the pathophysiology of periodontal disease and to evaluate possible clinical and future implications for a personalised therapeutical approach.

Electrical stimulation enhances early palatal wound healing in mice

BACKGROUND/OBJECTIVE

Electrical stimulation (ES) has been used to treat chronic wound and other clinical applications, showing favorable results in wound closure. It was hypothesized that ES can present a positive effect on oral mucosa healing. The aim of this study was to investigate the effects of ES during the palatal mucosa early healing process in Swiss mice.

METHODS

Ninety animals were divided into two groups: Control (C; n = 45), which received Sham ES applications, and Test (ES; n = 45), which received ES (100 μA; 9 kHz; 660 mVpp) once a day for 3 days. A full thickness wound was performed with a 1.5 mm diameter biopsy punch in the hard palate. Histologically, the following parameters were evaluated: palatal wound closure and epithelial and connective wound edge distance (EED and CED). Furthermore, IL-1β, IL-6, IL-10 TNF-α, and VEGF cytokine levels were evaluated by multiplex assay. The percentage of collagen fibers was assessed using the polarization method and the Smad proteins using the immunofluorescence method.

RESULTS

Palatal wound closure presented a significant reduction on day 5 in the ES group (p = 0.01). Additionally, both EED and CED were shorter for all time points in the ES group (p < 0.05), and the inflammatory markers IL-6, IL-10, TNF-α, and VEGF were reduced (p < 0.05). There were no differences in collagen fibers and phospho-Smad2 between the groups.

CONCLUSION

ES had a positive effect on early palatal wound closure outcomes, as well as on inflammatory markers.

The effect of non-thermal atmospheric pressure plasma application on wound healing after gingivectomy

Recent studies have indicated the potential benefits of Non-thermal atmospheric pressure plasma (NTAPP) as a novel therapeutic approach. The purpose of the current study was thus to assess the effect of NTAPP on gingival wound healing. Fifteen patients with bilaterally symmetrical gingival hyperplasia were included in the study. After gingivectomy and gingivoplasty, the left-hand side of the symmetrical surgical area was irradiated with NTAPP (plasma jet kINPen 11). Digital photographs of the gingival wounds were taken at baseline and days 3, 7, and 14. Wound epithelialisation was evaluated. Landry Wound Healing Index (WHI) scores and visual analogue scale (VAS) scores were also recorded. There were significant differences between the epithelialisation of the NTAPP-treated sites and the control sites after the surgical procedures. The NTAPP-treated sites had significantly smaller stained surface areas compared with the control sites on the 3rd, 7^th , and 14th days (P < .05). The NTAPP-treated sites had better WHI scores than the control sites throughout the follow-up period (P < .05). It can be concluded that NTAPP enhances epithelialisation and stimulates wound healing after gingivectomy and gingivoplasty. However, further clinical studies with larger sample sizes are needed to determine the exact benefits of NTAPP for gingival wound healing.

Elucidation of molecular pathways responsible for the accelerated wound healing induced by a novel fibrous chitin dressing

Fibrous chitin dressing (FCD) prepared from a NaOH-urea aqueous solution of chitin via a physical process was used to study its effect on wound healing using a full-thickness cutaneous wound model in rats and mice. It was demonstrated that wounds in rats covered with the FCD showed faster collagen (especially type I collagen) growth and speedier healing than those with Gauze (12 days versus 16 days). The ability of FCD to promote wound healing was also observed on wild-type (WT) mice. For MyD88-knockout mice, however, FCD displayed no beneficial but an adverse effect on wound healing: the healing time for wounds treated with FCD was even longer than those treated with gauze. Importantly, in vivo studies indicated that FCD-treated mice, compared to gauze-treated ones, exhibited markedly higher expressions of MyD88, IKBα, TGF-β, P-TβR II, TβR II and P-Smad2/3 in wild-type mice. For MyD88 knockout mice, however, the expressions of those molecules were inhibited and lowered in FCD-treated ones than those treated with gauze. In vitro studies confirmed that chitin increased the expression of TGF-β, P-TβRII and P-Smad2/3 while the expressions of those molecules were significantly inhibited with CD14 antibody (p < 0.05). These results indicated that FCD accelerated wound healing through a MyD88-dependent pathway, followed by a TGF-β/Smad pathway. This work not only demonstrated the superior wound healing effect of chitin-derived dressing, but also provided for the first time the underlying molecular mechanism, further establishing chitin as an important biomedical material for potential clinical applications.

Single-walled carbon nanohorns modulate tenocyte cellular response and tendon biomechanics

Subfailure ligament and tendon injury remain a significant burden to global healthcare. Here, we present the use of biocompatible single-walled carbon nanohorns (CNH) as a potential treatment for the repair of sub-failure injury in tendons. First, in vitro exposure of CNH to human tenocytes revealed no change in collagen deposition but a significant decrease in cell metabolic activity after 14 days. Additionally, gene expression studies revealed significant downregulation of collagen Types I and III mRNA at 7 days with some recovery after 14 days of exposure. Biomechanical tests with explanted porcine digitorum tendons showed the ability of CNH suspensions to modulate tendon biomechanics, most notably elastic moduli immediately after treatment. in vivo experiments demonstrated the ability of CNH to persist in the damaged matrix of stretch-injured Sprague Dawley rat Achilles tendon but not significantly modify tendon biomechanics after 7 days of treatment. Although these results demonstrate the early feasibility of utility of CNH as a potential modality for tendon subfailure injury, additional work is needed to further validate and ensure clinical efficacy.

Negative feedback by SNAI2 regulates TGFβ1-induced amelotin gene transcription in epithelial-mesenchymal transition

Junctional epithelium (JE) demonstrates biological responses with the rapid turnover of gingival epithelial cells. The state occurs in inflammation of gingiva and wound healing after periodontal therapy. To understand the underlying mechanisms and to maintain homeostasis of JE, it is important to investigate roles of JE-specific genes. Amelotin (AMTN) is localized at JE and regulated by inflammatory cytokines and apoptotic factors that represent a critical role of AMTN in stabilizing the dentogingival attachment, which is an entrance of oral bacteria. In this study, we demonstrated that the AMTN gene expression was regulated by SNAI2 and transforming growth factor β1 (TGFβ1)-induced epithelial-mesenchymal transition (EMT) that occurs in wound healing and fibrosis during chronic inflammation. SNAI2 downregulated AMTN gene expression via SNAI2 bindings to E-boxes (E2 and E4) in the mouse AMTN gene promoter in EMT of gingival epithelial cells. Meanwhile, TGFβ1-induced AMTN gene expression was attenuated by SNAI2 and TGFβ1-induced SNAI2, without inhibition of the TGFβ1-Smad3 signaling pathway. Moreover, SNAI2 small interfering RNA (siRNA) rescued SNAI2-induced downregulation of AMTN gene expression, and TGFβ1-induced AMTN gene expression was potentiated by SNAI2 siRNA. Taken together, these data demonstrated that AMTN gene expression in the promotion of EMT was downregulated by SNAI2. The inhibitory effect of AMTN gene expression was an independent feedback on the TGFβ1-Smad3 signaling pathway, suggesting that the mechanism can be engaged in maintaining homeostasis of gingival epithelial cells at JE and the wound healing phase.

Lupeol, a Pentacyclic Triterpene, Promotes Migration, Wound Closure, and Contractile Effect In Vitro: Possible Involvement of PI3K/Akt and p38/ERK/MAPK Pathways

Skin wound healing is a dynamic and complex process involving several mediators at the cellular and molecular levels. Lupeol, a phytoconstituent belonging to the triterpenes class, is found in several fruit plants and medicinal plants that have been the object of study in the treatment of various diseases, including skin wounds. Various medicinal properties of lupeol have been reported in the literature, including anti-inflammatory, antioxidant, anti-diabetic, and anti-mutagenic effects. We investigated the effects of lupeol (0.1, 1, 10, and 20 μg/mL) on in vitro wound healing assays and signaling mechanisms in human neonatal foreskin keratinocytes and fibroblasts. Results showed that, at high concentrations, Lupeol reduced cell proliferation of both keratinocytes and fibroblasts, but increased in vitro wound healing in keratinocytes and promoted the contraction of dermal fibroblasts in the collagen gel matrix. This triterpene positively regulated matrix metalloproteinase (MMP)-2 and inhibited the NF-κB expression in keratinocytes, suggesting an anti-inflammatory effect. Lupeol also modulated the expression of keratin 16 according to the concentration tested. Additionally, in keratinocytes, lupeol treatment resulted in the activation of Akt, p38, and Tie-2, which are signaling proteins involved in cell proliferation and migration, angiogenesis, and tissue repair. These findings suggest that lupeol has therapeutic potential for accelerating wound healing.

Modulation of microenvironment for controlling the fate of periodontal ligament cells: the role of Rho/ROCK signaling and cytoskeletal dynamics

Cells behave in a variety of ways when they perceive changes in their microenvironment; the behavior of cells is guided by their coordinated interactions with growth factors, niche cells, and extracellular matrix (ECM). Modulation of the microenvironment affects the cell morphology and multiple gene expressions. Rho/Rho-associated coiled-coil-containing protein kinase (ROCK) signaling is one of the key regulators of cytoskeletal dynamics and actively and/or passively determines the cell fate, such as proliferation, migration, differentiation, and apoptosis, by reciprocal communication with the microenvironment. During periodontal wound healing, it is important to recruit the residential stem cells into the defect site for regeneration and homeostasis of the periodontal tissue. Periodontal ligament (PDL) cells contain a heterogeneous fibroblast population, including mesenchymal stem cells, and contribute to the reconstruction of tooth-supporting tissues. Therefore, bio-regeneration of PDL cells has been the ultimate goal of periodontal therapy for decades. Recent stem cell researches have shed light on intrinsic ECM properties, providing paradigm shifts in cell fate determination. This review focuses on the role of ROCK activity and the effects of Y-27632, a specific inhibitor of ROCK, in the modulation of ECM-microenvironment. Further, it presents the current understanding of how Rho/ROCK signaling affects the fate determination of stem cells, especially PDL cells. In addition, we have also discussed in detail the underlying mechanisms behind the reciprocal response to the microenvironment.

Amelotin gene expression is temporarily being upregulated at the initiation of apoptosis induced by TGFβ1 in mouse gingival epithelial cells

Amelotin (AMTN) is expressed and secreted by ameloblasts in the maturation stage of amelogenesis and persist with low levels in the junctional epithelium (JE) of erupted teeth. The purpose of this study is to investigate the transcriptional regulation of the AMTN gene by transforming growth factor beta1 (TGFβ1) in gingival epithelial (GE1) cells in the apoptosis phase. Apoptosis was evaluated by the fragmentation of chromosomal DNA and TUNEL staining. A real-time PCR was carried out to examine the AMTN mRNA levels induced by TGFβ1 and Smad3 overexpression. Transient transfection analyses were completed using the various lengths of mouse AMTN gene promoter constructs with or without TGFβ1. Chromatin immunoprecipitation (ChIP) assays were performed to investigate the Smad3 bindings to the AMTN gene promoter by TGFβ1. TGFβ1-induced apoptosis in GE1 cells were detected at 24 and 48 h by DNA fragmentation and TUNEL staining. AMTN mRNA levels increased at 6 h and reached maximum at 24 h in GE1 cells. Luciferase activities of the mouse AMTN gene promoter constructs were induced by TGFβ1. The results of the ChIP assays showed that there was an increase in Smad3 binding to Smad-binding element (SBE)#1 and SBE#2 after stimulation by TGFβ1. Immunohistochemical localization of AMTN was detected in the JE, and the AMTN protein levels in Smad3-deficient mice were decreased compared with wild-type mice. AMTN mRNA levels were induced at the initiation of apoptosis by TGFβ1, which mediated through the Smad3 bindings to SBEs in the mouse AMTN gene promoter.

Smad2 overexpression enhances adhesion of gingival epithelial cells

OBJECTIVE

Gingival epithelial cells play an important role in preventing the initiation of periodontitis, by their hemidesmosomal adhesion to the tooth root surface. Adhesion requires integrin-extracellular matrix (ECM) interactions that are intricately regulated by transforming growth factor-β (TGF-β) signaling. However, the mechanisms underlying the interplay between adhesion molecules and TGF-β, especially the respective roles of Smad2 and Smad3, remain elusive. In this study, we examined the effects of Smad overexpression on gingival epithelial cell adhesion and expression profiles of integrin and ECM-related genes.

METHODS

Human gingival epithelial cells immortalized by the SV40 T-antigen were transfected with Smad2- and Smad3-overexpression vectors. A cell adhesion assay involving fluorescence detection of attached cells was performed using the ArrayScan imaging system. Real-time PCR was performed to examine the kinetics of integrin and ECM gene expression. In vitro and in vivo localization of adhesion molecules was examined by immunofluorescence analysis.

RESULTS

By using SB431542, a specific inhibitor of the TGF-β type I receptor, Smad2/3 signaling was confirmed to be dominant in TGF-β1-induced cell adhesion. The Smad2-transfectant demonstrated higher potency for cell adhesion and integrin expression (α2, α5, β4, and β6) than the Smad3-transfectant, whereas little or no change in ECM expression was observed in either transfectant. Moreover, the gingival epithelium of transgenic mice that overexpressed Smad2 driven by the keratin 14 promoter showed increased integrin α2 expression.

CONCLUSION

These findings indicate the crucial role of Smad2 in increased adhesion of gingival epithelial cells via upregulation of integrin α2.

Smad2 overexpression induces alveolar bone loss and up regulates TNF-α, and RANKL

OBJECTIVE

The aim of the current study was to investigate whether Smad2 overexpression in JE cells induced alveolar bone loss, and to understand the mechanisms regulating the bone loss.

METHODS

A mouse line was created that used a cytokeratin 14 (K14) promoter to overexpress Smad2 in the epithelium of the transgenic mice (K14-Smad2). Micro CT radiographs (μCT) were used to assess bone loss, bone volume, and bone density. The expression of Tnfα, Il1-β, Ifγ, Rankl, and Opg were assessed by RT-PCR. Western blots were used to detect the protein levels of TNF-α and IL1-β. Tartrate-resistant acid phosphatase (TRAP) was used as a marker for osteoclasts. Wild type (WT) mice were used as controls in all steps of the current study.

RESULTS

K14-Smad2 mice had 52.5% (±4.2) root exposed compared to 32.4%(±3.2) in the WT mice. There was a significant difference in alveolar bone volume in the K14-Smad2 mice when compared to WT mice 2.65mm³ (±0.3) and 4.3mm³ (±0.35) respectively. K14-Smad2 mice also had reduced bone density 696.8mg/cc (±70) at 12 months when compared to WT mice 845.9mg/cc(±10). The mRNA levels of Tnfα and Rankl increased by 3.26- and 2.5-fold respectively in the K14-Smad2 mice when compared to controls. The protein level of TNF-α was also significantly increased to 2.8-fold in K14-Smad2 mice when compared to WT mice. Smad2 overexpression increased the total numbers of osteoclasts in K14-Smad2 mice (3.4±0.2)-fold when compared to WT mice.

CONCLUSION

Smad2 overexpression induces alveolar bone loss and increases the numbers of osteoclasts. Also, Smad2 overexpression up-regulates TNF-α and RANKL.

Non-thermal atmospheric pressure plasma increased mRNA expression of growth factors in human gingival fibroblasts

OBJECTIVES

The aim of this in vitro study was to investigate the effects of a non-thermal atmospheric pressure plasma jet (NTAPPJ) on the cellular activity of human gingival fibroblasts (HGF) for possible non-surgical application of it during gingival wound healing.

MATERIALS AND METHODS

HGF cells were exposed with NTAPPJ for 1, 2, and 4 min and were investigated for cellular attachment, cell viability, morphology of attached cells, proliferation rate, and messenger ribonucleic acid (mRNA) expression of various growth factors. Also, scavengers for chemicals produced by NTAPPJ were used to identify the chemical species responsible for the effects.

RESULTS

There was no significant change in the number of HGF cells attached or their proliferation following NTAPPJ exposure. Also, high cell viability resulted from exposure of all of HGF cells to NTAPPJ for 1, 2, and 4 min. However, cells were more stretched while the mRNA expressions of transforming growth factor and vascular endothelial growth factor were significantly increased following NTAPPJ exposure. Additionally, the scavenger test showed that nitric oxide is likely to be the chemical responsible for an increase of cellular activity.

CONCLUSION

The results demonstrated that the NTAPPJ increased mRNA expressions of growth factors in human gingival fibroblasts.

CLINICAL RELEVANCE

Application of NTAPPJ would be useful in gingival wound healing in clinics though additional studies confirming the effects would be needed.

Up-regulation of Hsp72 and keratin16 mediates wound healing in streptozotocin diabetic rats

Background

Impaired wound healing is a complication of diabetes and a serious problem in clinical practice. We previously found that whey protein (WP) was able to regulate wound healing normally in streptozotocin (STZ)-diabetic models. This subsequent study was designed to assess the effect of WP on heat shock protein-72 (Hsp72) and keratin16 (Krt16) expression during wound healing in diabetic rats.

Methods

WP at a dosage of 100 mg/kg of body weight was orally administered daily to wounded normal and STZ-diabetic rats for 8 days.

Results

At day 4, the WP-treated diabetic wound was significantly reduced compared to that in the corresponding control. Diabetic wounded rats developed severe inflammatory infiltration and moderate capillary dilatation and regeneration. Treated rats had mild necrotic formation, moderate infiltration, moderate to severe capillary dilatation and regeneration, in addition to moderate epidermal formation. Hsp72 and Krt16 densities showed low and dense activity in diabetic wounded and diabetic wounded treated groups, respectively. At day 8, WP-treatment of diabetic wounded animals revealed great amelioration with complete recovery and closure of the wound. Reactivity of Hsp72 and Krt16 was reversed, showing dense and low, or medium and low, activity in the diabetic wounded and diabetic wounded treated groups, respectively. Hsp72 expression in the pancreas was found to show dense reactivity with WP-treated diabetic wound rats.

Conclusion

This data provides evidence for the potential impact of WP in the up-regulation of Hsp72 and Krt16 in T1D, resulting in an improved wound healing process in diabetic models.

Cross-Talk Between Human Tenocytes and Bone Marrow Stromal Cells Potentiates Extracellular Matrix Remodeling In Vitro

Tendon and ligament (T/L) pathologies account for a significant portion of musculoskeletal injuries and disorders. Tissue engineering has emerged as a promising solution in the regeneration of both tissues. Specifically, the use of multipotent human mesenchymal stromal cells (hMSC) has shown great promise to serve as both a suitable cell source for tenogenic regeneration and a source of trophic factors to induce tenogenesis. Using four donor sets, we investigated the bidirectional paracrine tenogenic response between human hamstring tenocytes (hHT) and bone marrow-derived hMSC. Cell metabolic assays showed that only one hHT donor experienced sustained notable increases in cell metabolic activity during co-culture. Histological staining confirmed that co-culture induced elevated collagen protein levels in both cell types at varying time-points in two of four donor sets assessed. Gene expression analysis using qPCR showed the varied up-regulation of anabolic and catabolic markers involved in extracellular matrix maintenance for hMSC and hHT. Furthermore, analysis of hMSC/hHT co-culture secretome using a reporter cell line for TGF-β, a potent inducer of tenogenesis, revealed a trend of higher TGF-β bioactivity in hMSC secretome compared to hHT. Finally, hHT cytoskeletal immunostaining confirmed that both cell types released soluble factors capable of inducing favorable tenogenic morphology, comparable to control levels of soluble TGF-β1. These results suggest a potential for TGF-β-mediated signaling mechanism that is involved during the paracrine interplay between the two cell types that is reminiscent of T/L matrix remodeling/turnover. These findings have significant implications in the clinical use of hMSC for common T/L pathologies.

Upregulation of gingival tissue miR-200b in obese periodontitis subjects

Increased local immune and inflammatory responses in obese individuals with periodontitis may explain the aggressive clinical presentation and altered treatment response when compared to that of normal weight subjects. Our goal was to identify any differences in microRNA (miRNA) expression profiles of gingival tissue in periodontitis when obesity is present, which may suggest novel molecular pathways that this miRNA network may affect. Total RNA was extracted from gingival tissue biopsies collected from normal weight and obese individuals with periodontitis; miRNA expression profiling was performed with Affymetrix GeneChip miRNA 3.0 arrays; and results were validated with quantitative reverse transcription polymerase chain reaction (qRT-PCR). In silico identification of previously confirmed miRNA gene targets was conducted through miRTarBase and miRWalk databases, and pathway enrichment analysis identified enriched miRNA gene sets. Expression of selected genes in the same biopsy samples was tested with qRT-PCR. The gingival tissue miRNA profile of obese patients, compared to that of normal weight patients, showed 13 upregulated and 22 downregulated miRNAs, among which miR-200b was validated by qRT-PCR to be significantly increased in obesity. Functional analysis of 51 experimentally validated miR-200b gene targets identified enrichment of genes involved in cell motility, differentiation, DNA binding, response to stimulus, and vasculature development pathways not previously identified in the obesity-specific disease profile. Furthermore, the expression of the miR-200b gene targets ZEB1/2, GATA2, and KDR was confirmed by qRT-PCR as being lower in obese patients with periodontitis versus normal weight patients, suggesting a role of miR-200b in regulation of a set of gene targets and biological pathways relevant to wound healing and angiogenesis. Functional studies to explore the role of miR-200b in the above processes may offer new insights on putative therapeutic targets for this group of patients.

Bone morphogenetic protein signaling suppresses wound-induced skin repair by inhibiting keratinocyte proliferation and migration

Bone morphogenetic protein (BMP) signalling plays a key role in the control of skin development and postnatal remodelling by regulating keratinocyte proliferation, differentiation and apoptosis. To study the role of BMPs in wound-induced epidermal repair, we used transgenic mice overexpressing the BMP downstream component Smad1 under the control of a K14 promoter as an in vivo model, as well as ex vivo and in vitro assays. K14-caSmad1 mice exhibited retarded wound healing associated with significant inhibition of proliferation and increased apoptosis in healing wound epithelium. Furthermore, microarray and qRT-PCR analyses revealed decreased expression of a number of cytoskeletal/cell motility-associated genes including wound-associated keratins (Krt16, Krt17) and Myo5a, in the epidermis of K14-caSmad1 mice versus wild-type controls during wound healing. BMP treatment significantly inhibited keratinocyte migration ex vivo, and primary keratinocytes of K14-caSmad1 mice showed retarded migration compared to wild-type controls. Finally, siRNA-mediated silencing of Bmpr-1B in primary mouse keratinocytes accelerated cell migration and was associated with increased expression of Krt16, Krt17 and Myo5a compared to controls. Thus, this study demonstrates that BMPs inhibit keratinocyte proliferation, cytoskeletal organization and migration in regenerating skin epithelium during wound healing, and raises a possibility for using BMP antagonists for the management of chronic wounds.

Transforming Growth Factor Beta Signaling in Cutaneous Wound Healing: Lessons Learned from Animal Studies

SIGNIFICANCE

Wound healing is a complex physiological process involving a multitude of growth factors, among which transforming growth factor beta (TGF-β) has the broadest spectrum of effects. Animal studies have provided key information on the mechanisms of TGF-β action in wound healing and have guided the development of therapeutic strategies targeting the TGF-β pathway to improve wound healing and scarring outcome.

RECENT ADVANCES

Development of tissue-specific expression systems for overexpression or knockout of TGF-β signaling pathway components has led to novel insight into the role of TGF-β signaling in wound healing. This work has also identified molecules that might serve as molecular targets for the treatment of pathological skin conditions such as chronic wounds and excessive scarring (fibrosis).

CRITICAL ISSUES

Many of the mouse models with genetic alterations in the TGF-β signaling pathway develop an underlying skin abnormality, which may pose some limitations on the interpretation of wound-healing results obtained in these animals. Also, TGF-β's pleiotropic effects on many cell types throughout all phases of wound healing present a challenge in designing specific strategies for targeting the TGF-β signaling pathway to promote wound healing or reduce scarring.

FUTURE DIRECTIONS

Further characterization of TGF-β signaling pathway components using inducible tissue-specific overexpression or knockout technology will be needed to corroborate results obtained in mouse models that display a skin phenotype, and to better understand the role of TGF-β signaling during distinct phases of the wound-healing process. Such studies will also provide a better understanding of how TGF-β mediates its autocrine, paracrine, and double paracrine effects on cellular responses in vivo during wound healing.