TGF-β3 modulates the inflammatory environment and reduces scar formation following vocal fold mucosal injury in rats

Human Keratoconus Cell Contractility is Mediated by Transforming Growth Factor-Beta Isoforms

Keratoconus (KC) is a progressive disease linked to defects in the structural components of the corneal stroma. The extracellular matrix (ECM) is secreted and assembled by corneal keratocytes and regulated by transforming growth factor-β (TGF-β). We have previously identified alterations in the TGF-β pathway in human keratoconus cells (HKCs) compared to normal corneal fibroblasts (HCFs). In our current study, we seeded HKCs and HCFs in 3D-collagen gels to identify variations in contractility, and expression of matrix metalloproteases (MMPs) by HKCs in response the TGF-β isoforms. HKCs showed delayed contractility with decreased Collagen I:Collagen V ratios. TGF-β1 significantly increased ECM contraction, Collagen I, and Collagen V expression by HKCs. We also found that HKCs have significantly decreased Collagen I:Collagen III ratios suggesting a potential link to altered collagen isoform expression in KC. Our findings show that HKCs have significant variations in collagen secretion in a 3D collagen gel and have delayed contraction of the matrix compared to HCFs. For the first time, we utilize a collagen gel model to characterize the contractility and MMP expression by HKCs that may contribute to the pathobiology of KC.

Scarless wound healing: chasing the holy grail

Over 100 million patients acquire scars in the industrialized world each year, primarily as a result of elective operations. Although undefined, the global incidence of scarring is even larger, extending to significant numbers of burn and other trauma-related wounds. Scars have the potential to exert a profound psychological and physical impact on the individual. Beyond aesthetic considerations and potential disfigurement, scarring can result in restriction of movement and reduced quality of life. The formation of a scar following skin injury is a consequence of wound healing occurring through reparative rather than regenerative mechanisms. In this article, the authors review the basic stages of wound healing; differences between adult and fetal wound healing; various mechanical, genetic, and pharmacologic strategies to reduce scarring; and the biology of skin stem/progenitor cells that may hold the key to scarless regeneration.

Keratoconus in vitro and the key players of the TGF-β pathway

PURPOSE

Keratoconus (KC) is a corneal thinning disease of unknown etiology whose pathophysiology is correlated with the presence of a thin corneal stroma and altered extracellular matrix (ECM). Transforming growth factor-β (TGF-β) signaling is a key regulator of ECM secretion and assembly in multiple tissues, including the anterior segment of the eye, and it has been linked to KC. We have previously shown that human keratoconus cells (HKCs) have a myofibroblast phenotype and altered ECM assembly compared to normal human corneal fibroblasts (HCFs). Moreover, TGF-β3 treatment promotes assembly of a more normal stromal ECM and modulates the fibrotic phenotype in HKCs. Herein, we identify alterations in TGF-β signaling that contribute to the observed fibrotic phenotype in HKCs.

METHODS

HCFs and HKCs were stimulated with TGF-β1, TGF-β2, or TGF-β3 isoforms (0.1 ng/mL) in the presence of a stable vitamin C derivative (0.5 mM) for 4 weeks. All samples were examined using RT-PCR and western blotting to quantify changes in the expressions of key TGF-β signaling molecules between HCFs and HKCs.

RESULTS

We found a significant downregulation in the SMAD6 and SMAD7 expressions by HKCs when compared to HCFs (p≤0.05). Moreover, stimulation of HKCs with any of the three TGF-β isoforms did not significantly alter the expressions of SMAD6 or SMAD7. HCFs also showed an upregulation in TGF-βRI, TGF-βRII, and TGF-βRIII following TGF-β3 treatment, whereas HKCs showed a significant two-fold downregulation.

CONCLUSIONS

Overall, our data shows the decreased expressions of the regulatory SMADs SMAD6 and SMAD7 by HKCs contribute to the pathological ECM structure observed in KC, and TGF-β3 may attenuate this mechanism by downregulating the expression of the key profibrotic receptor, TGF-βRII. Our study suggests a significant role of altered regulation of TGF-β signaling in KC progression and that it may enable novel therapeutic developments targeting TGF-β receptor regulation.

Paracrine action of mesenchymal stromal cells delivered by microspheres contributes to cutaneous wound healing and prevents scar formation in mice

BACKGROUND AIMS

Accumulating evidence suggests that mesenchymal stromal cells (MSCs) participate in wound healing to favor tissue regeneration and inhibit fibrotic tissue formation. However, the evidence of MSCs to suppress cutaneous scar is extremely rare, and the mechanism remains unidentified. This study aimed to demonstrate whether MSCs-as the result of their paracrine actions on damaged tissues-would accelerate wound healing and prevent cutaneous fibrosis.

METHODS

For efficient delivery of MSCs to skin wounds, microspheres were used to maintain MSC potency. Whether MSCs can accelerate wound healing and alleviate cutaneous fibrosis through paracrine action was investigated with the use of a Transwell co-culture system in vitro and a murine model in vivo.

RESULTS

MSCs cultured on gelatin microspheres fully retained their cell surface marker expression profile, proliferation, differentiation and paracrine potential. Co-cultures of MSCs and fibroblasts indicated that the benefits of MSCs on suppressing fibroblast proliferation and its fibrotic behavior induced by inflammatory cytokines probably were caused by paracrine actions. Importantly, microspheres successfully delivered MSCs into wound margins and significantly accelerated wound healing and concomitantly reduced the fibrotic activities of cells within the wounds and excessive accumulation of extracellular matrix as well as the transforming growth factor-β1/transforming growth factor-β3 ratio.

CONCLUSIONS

This study provides insight into what we believe to be a previously undescribed, multifaceted role of MSC-released protein in reducing cutaneous fibrotic formation. Paracrine action of MSCs delivered by microspheres may thus qualify as a promising strategy to enhance tissue repair and to prevent excessive fibrosis during cutaneous wound healing.

Identification of inflammatory mediators in patients with rhegmatogenous retinal detachment associated with choroidal detachment

PURPOSE

To investigate the expression profile of intravitreous cytokines, chemokines, and growth factors in patients with rhegmatogenous retinal detachment associated with choroidal detachment (RRDCD) in comparison with patients with only rhegmatogenous retinal detachment (RRD).

METHODS

Twenty RRDCD patients and 30 RRD patients were included in this case-control study. A multiplex bead-based immunoassay was performed to determine the expression of a wide range of 29 inflammatory mediators in undiluted vitreous from the patients. Data were analyzed using the Mann-Whitney U-test for nonparametric values and multivariate logistic regression analysis.

RESULTS

Compared with the patients with RRD, intravitreous inflammatory mediators, including migration inhibitor factor (MIF), interleukin-6 (IL-6), CCL4, CCL11, CCL17, CCL19, CCL22, CXCL9, CXCL8, soluble inter-cellular adhesion molecule 1 (sICAM-1), transforming growth factor β3 (TGF-β3), and platelet-derived growth factor AA (PDGF-AA), were upregulated in patients with RRDCD. After calibrating the factors duration of detachment, preoperative proliferative vitreoretinopathy grade, and presence or absence of macular hole, the PDGF-AA concentrations were not significantly different according to the multivariate logistic regression analysis. MIF and sICAM-1 markers were significantly different between the two groups and represented a forward stepwise logistic regression trend.

CONCLUSIONS

This is the first report to use multiplex bead analysis to investigate inflammatory mediators related to RRDCD. We proposed that the upregulated expression of these mediators may be involved in the inflammation process of RRDCD and that regulation of their expression may be potentially therapeutic by altering local inflammation.

Epidermal growth factor mediated healing in stem cell-derived vocal fold mucosa

BACKGROUND

The goal of vocal fold wound healing is the reconstitution of functional tissue, including a structurally and functionally intact epithelium. Mechanisms underlying reepithelialization in vocal folds are not known, although it is suspected that healing involves the interplay between several growth factors. We used a three-dimensional human embryonic stem cell-derived model of vocal fold mucosa to examine the effects of one growth factor, exogenous epidermal growth factor (EGF), on wound healing.

MATERIALS AND METHODS

A scratch wound was created in the in vitro model. Rate of wound healing, epidermal growth factor receptor (EGFR) activation, and cell proliferation after injury were analyzed with and without application of both exogenous EGF and an EGFR inhibitor, gefitinib.

RESULTS

Wound repair after injury was significantly hastened by application of exogenous EGF (13.3 μm/h, ± 2.63) compared with absence of exogenous EGF (7.1 μm/h ± 2.84), but inhibited with concurrent addition of Gefitinib (5.2 μm/h, ± 2.23), indicating that EGF mediates wound healing in an EGFR-dependent manner. Immunohistochemistry revealed that EGFR activation occurred only in the presence of exogenous EGF. Although not statistically significant, increased density of Ki67 staining in the epithelium adjacent to the scratch wound was observed after treatment with EGF, suggesting a tendency for exogenous EGF to increase epithelial cell proliferation.

CONCLUSIONS

Exogenous EGF increases the rate of wound healing in an EGFR-dependent manner in a three-dimensional stem cell-derived model of vocal fold mucosa. This model of wound healing can be used to gain insight into the mechanisms that regulate vocal fold epithelial repair after injury.

Microarray-based characterization of differential gene expression during vocal fold wound healing in rats

The vocal fold (VF) mucosa confers elegant biomechanical function for voice production but is susceptible to scar formation following injury. Current understanding of VF wound healing is hindered by a paucity of data and is therefore often generalized from research conducted in skin and other mucosal systems. Here, using a previously validated rat injury model, expression microarray technology and an empirical Bayes analysis approach, we generated a VF-specific transcriptome dataset to better capture the system-level complexity of wound healing in this specialized tissue. We measured differential gene expression at 3, 14 and 60 days post-injury compared to experimentally naïve controls, pursued functional enrichment analyses to refine and add greater biological definition to the previously proposed temporal phases of VF wound healing, and validated the expression and localization of a subset of previously unidentified repair- and regeneration-related genes at the protein level. Our microarray dataset is a resource for the wider research community and has the potential to stimulate new hypotheses and avenues of investigation, improve biological and mechanistic insight, and accelerate the identification of novel therapeutic targets.

Epithelial cells are active participants in vocal fold wound healing: an in vivo animal model of injury

Vocal fold epithelial cells likely play an important, yet currently poorly defined, role in healing following injury, irritation and inflammation. In the present study, we sought to identify a possible role for growth factors, epidermal growth factor (EGF) and transforming growth factor-beta 1 (TGFβ1), in epithelial regeneration during wound healing as a necessary first step for uncovering potential signaling mechanisms of vocal fold wound repair and remodeling. Using a rat model, we created unilateral vocal fold injuries and examined the timeline for epithelial healing and regeneration during early and late stages of wound healing using immunohistochemistry (IHC). We observed time-dependent secretion of the proliferation marker, ki67, growth factors EGF and TGFβ1, as well as activation of the EGF receptor (EGFR), in regenerating epithelium during the acute phase of injury. Ki67, growth factor, and EGFR expression peaked at day 3 post-injury. Presence of cytoplasmic and intercellular EGF and TGFβ1 staining occurred up to 5 days post-injury, consistent with a role for epithelial cells in synthesizing and secreting these growth factors. To confirm that epithelial cells contributed to the cytokine secretion, we examined epithelial cell growth factor secretion in vitro using polymerase chain reaction (PCR). Cultured pig vocal fold epithelial cells expressed both EGF and TGFβ1. Our in vivo and in vitro findings indicate that epithelial cells are active participants in the wound healing process. The exact mechanisms underlying their roles in autocrine and paracrine signaling guiding wound healing await study in a controlled, in vitro environment.

Upregulation of transforming growth factor-β signaling in a rat model of rotator cuff tears

BACKGROUND

Muscle atrophy, fatty infiltration, and fibrosis of the muscle have been described as important factors governing outcome after rotator cuff injury and repair. Muscle fibrosis is also thought to have a role in determining muscle compliance at the time of surgery. The transforming growth factor-β (TGF-β) pathways are highly conserved pathways that exert a potent level of control over muscle gene expression and are critical regulators of fibrosis in multiple organ systems. It has been shown that TGF-β can regulate important pathways of muscle atrophy, including the Akt/mammalian target of rapamycin pathway. The purpose of this study was to evaluate the expression of TGF-β and its downstream effectors of fibrosis after a massive rotator cuff tear (RCT) in a previously established rat model.

METHODS

To simulate a massive RCT, infraspinatus and supraspinatus tenotomy and suprascapular nerve transection were performed on Sprague-Dawley rats with use of a validated model. Two and 6 weeks after surgery, supraspinatus muscles were harvested to study alterations in TGF-β signaling by Western blotting, quantitative polymerase chain reaction, and histologic analysis.

RESULTS

There was a significant increase in fibrosis in the rotator cuff muscle after RCT in our animal model. There was a concomitant increase in TGF-β gene and protein expression at both 2 and 6 weeks after RCT. Evaluation of the TGF-β signaling pathway revealed an increase in SMAD2 activation but not in SMAD3. There was an increase in profibrotic markers collagen I, collagen III, and α-smooth muscle actin.

CONCLUSIONS

TGF-β signaling is significantly upregulated in rat supraspinatus muscles after RCTs.

Effects of phonation time and magnitude dose on vocal fold epithelial genes, barrier integrity, and function

OBJECTIVES/HYPOTHESIS

To investigate the effects of increasing time and magnitude doses of vibration exposure on transcription of the vocal fold's junctional proteins, structural alterations, and functional tissue outcomes.

STUDY DESIGN

Animal study.

METHODS

100 New Zealand White breeder rabbits were studied. Dependent variables were measured in response to increasing time doses (30, 60, or 120 minutes) and magnitude doses (control, modal intensity, and raised intensity) of vibration exposure. Messenger RNA expression of occludin, zonula occluden-1 (ZO-1), E-cadherin, β-catenin, interleukin 1β, cyclooxygenase-2, transforming growth factor β-1, and fibronectin were measured. Tissue structural alterations were assessed using transmission electron microscopy (TEM). Transepithelial resistance was used to measure functional tissue outcomes.

RESULTS

Occludin gene expression was downregulated in vocal folds exposed to 120-minute time doses of raised-intensity phonation, relative to control, and modal-intensity phonation. ZO-1 gene expression was upregulated following a 120-minute time dose of modal-intensity phonation, compared to control, and downregulated after a 120-minute time dose of raised-intensity phonation, compared to modal-intensity phonation. E-cadherin gene expression was downregulated after a 120-minute time dose of raised-intensity phonation, compared to control and modal-intensity phonation. TEM revealed extensive desquamation of the stratified squamous epithelial cells with increasing time and magnitude doses of vibration exposure. A general observation of lower transepithelial resistance measures was made in tissues exposed to raised-intensity phonation compared to all other groups.

CONCLUSIONS

This study provides evidence of vocal fold tissue responses to varying time and magnitude doses of vibration exposure.

LEVEL OF EVIDENCE

NA.

Mechanotransduction and fibrosis

Scarring and tissue fibrosis represent a significant source of morbidity in the United States. Despite considerable research focused on elucidating the mechanisms underlying cutaneous scar formation, effective clinical therapies are still in the early stages of development. A thorough understanding of the various signaling pathways involved is essential to formulate strategies to combat fibrosis and scarring. While initial efforts focused primarily on the biochemical mechanisms involved in scar formation, more recent research has revealed a central role for mechanical forces in modulating these pathways. Mechanotransduction, which refers to the mechanisms by which mechanical forces are converted to biochemical stimuli, has been closely linked to inflammation and fibrosis and is believed to play a critical role in scarring. This review provides an overview of our current understanding of the mechanisms underlying scar formation, with an emphasis on the relationship between mechanotransduction pathways and their therapeutic implications.