Fetal Skin Wound Healing: Key Extracellular Matrix Components and Regulators in Scarless Healing

Fetal skin at early gestational stage is able to regenerate and heal rapidly after wounding. The exact mechanisms and molecular pathways involved in this process are however still largely unknown. The numerous differences in the skin of the early fetus versus skin in later developmental stages might provide clues for the mechanisms of scarless healing. This review summarizes the differences between mammalian fetal skin and the skin at later developmental phases in healthy and wounded conditions, focusing on extracellular matrix components, which are crucial factors in the microenvironment that direct cells and tissue functions and hence the wound healing process.

Genome-wide in vivo CRISPR screen identifies TGFβ3 as actionable biomarker of palbociclib resistance in triple negative breast cancer

Triple negative breast cancer (TNBC) remains exceptionally challenging to treat. While CDK4/6 inhibitors have revolutionized HR + breast cancer therapy, there is limited understanding of their efficacy in TNBC and meaningful predictors of response and resistance to these drugs remain scarce. We conducted an in vivo genome-wide CRISPR screen using palbociclib as a selection pressure in TNBC. Hits were prioritized using microarray data from a large panel of breast cancer cell lines to identify top palbociclib sensitizers. Our study defines TGFβ3 as an actionable determinant of palbociclib sensitivity that potentiates its anti-tumor effects. Mechanistically, we show that chronic palbociclib exposure depletes p21 levels, contributing to acquired resistance, and that TGFβ3 treatment can overcome this. This study defines TGFβ3 as an actionable biomarker that can be used to improve patient stratification for palbociclib treatment and exploits the synergistic interaction between CDK4/6 and TGFβ3 to propose a new combinatorial treatment for TNBC.

Transforming Growth Factor-β/Smad Signaling Inhibits Melanoma Cancer Stem Cell Self-Renewal, Tumor Formation and Metastasis

The secreted protein transforming growth factor-beta (TGFβ) plays essential roles, ranging from cell growth regulation and cell differentiation in both normal and cancer cells. In melanoma, TGFβ acts as a potent tumor suppressor in melanoma by blocking cell cycle progression and inducing apoptosis. In the present study, we found TGFβ to regulate cancer stemness in melanoma through the Smad signaling pathway. We discovered that TGFβ/Smad signaling inhibits melanosphere formation in multiple melanoma cell lines and reduces expression of the CD133+ cancer stem cell subpopulation in a Smad3-dependent manner. Using preclinical models of melanoma, we further showed that preventing Smad3/4 signaling, by means of CRISPR knockouts, promoted both tumorigenesis and lung metastasis in vivo. Collectively, our results define new functions for the TGFβ/Smad signaling axis in melanoma stem-cell maintenance and open avenues for new therapeutic approaches to this disease.

Concise Review on Scientific Approaches to Burns and Scars

Burns are large open surgical lesions bathed in virulent pus that result in rupturing of the cutaneous membrane, which has serious consequences such as an extensive loss of proteins, and body fluids, increased chances of infections, and sometimes death. These can be classified based on their penetration levels, i.e., first-degree burns penetrating the epidermis, second-degree burns including both epidermis and dermis, third-degree burns to both layers including the hair follicular cells, sweat glands and various core tissues, fourth-degree burns to adipose tissue, fifth stage burns to muscles, and sixth stage burns to bones. Wound healing/wound repair is a very perplexing process in which the tissues of the affected/burnt area repairs themselves to attain their original form and functionality but develop a scar at the wound site. This article mainly focuses on the algorithms to differentiate various degrees of burns, general first aid approaches to burns and scars, the rationale of treatment of burns, basic mechanisms highlighting the healing processes in humans in terms of free from scar formation as well as with scar formation at their elementary levels including cellular as well as biochemical levels, utility, and progression of pre-clinical data to humans and finally approaches for the improvement of scar formation in man.

The Role of TGF-β3 in Radiation Response

Transforming growth factor-beta 3 (TGF-β3) is a ubiquitously expressed multifunctional cytokine involved in a range of physiological and pathological conditions, including embryogenesis, cell cycle regulation, immunoregulation, and fibrogenesis. The cytotoxic effects of ionizing radiation are employed in cancer radiotherapy, but its actions also influence cellular signaling pathways, including that of TGF-β3. Furthermore, the cell cycle regulating and anti-fibrotic effects of TGF-β3 have identified it as a potential mitigator of radiation- and chemotherapy-induced toxicity in healthy tissue. This review discusses the radiobiology of TGF-β3, its induction in tissue by ionizing radiation, and its potential radioprotective and anti-fibrotic effects.

Myofibroblasts: Function, Formation, and Scope of Molecular Therapies for Skin Fibrosis

Myofibroblasts are contractile, α-smooth muscle actin-positive cells with multiple roles in pathophysiological processes. Myofibroblasts mediate wound contractions, but their persistent presence in tissues is central to driving fibrosis, making them attractive cell targets for the development of therapeutic treatments. However, due to shared cellular markers with several other phenotypes, the specific targeting of myofibroblasts has long presented a scientific and clinical challenge. In recent years, myofibroblasts have drawn much attention among scientific research communities from multiple disciplines and specialisations. As further research uncovers the characterisations of myofibroblast formation, function, and regulation, the realisation of novel interventional routes for myofibroblasts within pathologies has emerged. The research community is approaching the means to finally target these cells, to prevent fibrosis, accelerate scarless wound healing, and attenuate associated disease-processes in clinical settings. This comprehensive review article describes the myofibroblast cell phenotype, their origins, and their diverse physiological and pathological functionality. Special attention has been given to mechanisms and molecular pathways governing myofibroblast differentiation, and updates in molecular interventions.

Current and upcoming therapies to modulate skin scarring and fibrosis

Skin is the largest organ of the human body. Being the interface between the body and the outer environment, makes it susceptible to physical injury. To maintain life, nature has endowed skin with a fast healing response that invariably ends in the formation of scar at the wounded dermal area. In many cases, skin remodelling may be impaired, leading to local hypertrophic scars or keloids. One should also consider that the scarring process is part of the wound healing response, which always starts with inflammation. Thus, scarring can also be induced in the dermis, in the absence of an actual wound, during chronic inflammatory processes. Considering the significant portion of the population that is subject to abnormal scarring, this review critically discusses the state-of-the-art and upcoming therapies in skin scarring and fibrosis.

Elevated CD26 Expression by Skin Fibroblasts Distinguishes a Profibrotic Phenotype Involved in Scar Formation Compared to Gingival Fibroblasts

Compared to skin, wound healing in oral mucosa is faster and produces less scarring, but the mechanisms involved are incompletely understood. Studies in mice have linked high expression of CD26 to a profibrotic fibroblast phenotype, but this has not been tested in models more relevant for humans. We hypothesized that CD26 is highly expressed by human skin fibroblasts (SFBLs), and this associates with a profibrotic phenotype distinct from gingival fibroblasts (GFBLs). We compared CD26 expression in human gingiva and skin and in gingival and hypertrophic-like scar-forming skin wound healing in a pig model, and used three-dimensional cultures of human GFBLs and SFBLs. In both humans and pigs, nonwounded skin contained abundantly CD26-positive fibroblasts, whereas in gingiva they were rare. During skin wound healing, CD26-positive cells accumulated over time and persisted in forming hypertrophic-like scars, whereas few CD26-positive cells were present in the regenerated gingival wounds. Cultured human SFBLs displayed significantly higher levels of CD26 than GFBLs. This was associated with an increased expression of profibrotic genes and transforming growth factor-β signaling in SFBLs. The profibrotic phenotype of SFBLs partially depended on expression of CD26, but was independent of its catalytic activity. Thus, a CD26-positive fibroblast population that is abundant in human skin but not in gingiva may drive the profibrotic response leading to excessive scarring.

Current Therapeutic Approach to Hypertrophic Scars

Abnormal scarring and its accompanying esthetic, functional, and psychological sequelae still pose significant challe nges. To date, there is no satisfactory prevention or treatment option for hypertrophic scars (HSs), which is mostly due to not completely comprehending the mechanisms underlying their formation. That is why the apprehension of regular and controlled physiological processes of scar formation is of utmost importance when facing hypertrophic scarring, its pathophysiology, prevention, and therapeutic approach. When treating HSs and choosing the best treatment and prevention modality, physicians can choose from a plethora of therapeutic options and many commercially available products, among which currently there is no efficient option that can successfully overcome impaired skin healing. This article reviews current therapeutic approach and emerging therapeutic strategies for the management of HSs, which should be individualized, based on an evaluation of the scar itself, patients’ expectations, and practical, evidence-based guidelines. Clinicians are encouraged to combine various prevention and treatment modalities where combination therapy that includes steroid injections, 5-fluorouracil, and pulsed-dye laser seems to be the most effective. On the other hand, the current therapeutic options are usually empirical and their results are unreliable and unpredictable. Therefore, there is an unmet need for an effective, targeted therapy and prevention, which would be based on an action or a modulation of a particular factor with clarified mechanism of action that has a beneficial effect on wound healing. As the extracellular matrix has a crucial role in cellular and extracellular events that lead to pathological scarring, targeting its components mostly by regulating bone morphogenetic proteins may throw up new therapeutic approach for reduction or prevention of HSs with functionally and cosmetically acceptable outcome.

Liver fibrosis in bile duct-ligated rats correlates with increased hepatic IL-17 and TGF-β2 expression

BACKGROUND AND RATIONALE FOR THE STUDY: IL-17, TGF-β1/2 are cytokines involved in the development of kidney, pulmonary and liver fibrosis. However, their expression kinetics in the pathogenesis of cholestatic liver fibrosis have not yet been fully explored. The aim of the study was to analyze the expression of IL-17, RORγt, NKp46, TGF-β1, and TGF-β2 in the liver of rats with bile duct ligation (BDL).

RESULTS

Hepatic IL-17A gene expression analyzed by qRT-PCR showed a dramatic increase of 350 and 10 fold, at 8 and 30 days post BDL, respectively. TGFβ1 and TGFβ2 gene expression significantly increased throughout the whole fibrotic process. At the protein level in liver homogenates, IL-17, TGF-β1, and RORγt significantly increased at 8 and 30 days after BDL. Interestingly, a significant increase in the protein levels of TGF-β2 and decrease of NKp46 was observed only 30 days after BDL. Unexpectedly, TGF-β2 exhibited stronger signals than TGF-β1 at the gene expression and protein levels. Histological analysis showed bile duct proliferation and collagen deposition.

CONCLUSIONS

Our results suggest that pro-fibrogenic cytokines IL-17, TGF-β1 and, strikingly, TGF-β2 might be important players of liver damage in the pathogenesis of early and advanced experimental cholestatic fibrosis. Th17 cells might represent an important source of IL-17, while NK cell depletion may account for the perpetuation of liver damage in the BDL model.

Growth factor pathways in hypertrophic scars: Molecular pathogenesis and therapeutic implications

Hypertrophic scars represent the most common complication of skin injury and are caused by excessive cutaneous wound healing characterized by hypervascularity and pathological deposition of extracellular matrix (ECM) components. To date, the optimal and specific treatment methods for hypertrophic scars have not been available in the clinic. Current paradigm has established fibroblasts and myofibroblasts as pivotal effector cells in the pathophysiology of wound healing. Their biological properties including origin, proliferation, migration, contraction and ECM regulation have profound impacts on the progression and regression of hypertrophic scars. These complex processes are executed and modulated by a signaling network involving a number of growth factors and cytokines. Of particular importance is transforming growth factor-β, platelet-derived growth factor, connective tissue growth factor, epidermal growth factor, and vascular endothelial growth factor. This review article briefly describes the biological functions of fibroblasts and myofibroblasts during hypertrophic scars, and thereafter examines the up-to-date molecular knowledge on the roles of key growth factor pathways in the pathophysiology of hypertrophic scars. Importantly, the therapeutic implications and future challenges of these molecular discoveries are critically discussed in the hope of advancing therapeutic approaches to limit pathological scar formation.

Human gingival fibroblasts display a non-fibrotic phenotype distinct from skin fibroblasts in three-dimensional cultures

Scar formation following skin injury can be a major psychosocial and physiological problem. However, the mechanisms of scar formation are still not completely understood. Previous studies have shown that wound healing in oral mucosa is faster, associates with a reduced inflammatory response and results to significantly reduced scar formation compared with skin wounds. In the present study, we hypothesized that oral mucosal fibroblasts from human gingiva are inherently distinct from fibroblasts from breast and abdominal skin, two areas prone to excessive scar formation, which may contribute to the preferential wound healing outcome in gingiva. To this end, we compared the phenotype of human gingival and skin fibroblasts cultured in in vivo-like three-dimensional (3D) cultures that mimic the cells' natural extracellular matrix (ECM) niche. To establish 3D cultures, five parallel fibroblast lines from human gingiva (GFBLs) and breast skin (SFBLs) were seeded in high density, and cultured for up to 21 days in serum and ascorbic acid containing medium to induce expression of wound-healing transcriptome and ECM deposition. Cell proliferation, morphology, phenotype and expression of wound healing and scar related genes were analyzed by real-time RT-PCR, Western blotting and immunocytochemical methods. The expression of a set of genes was also studied in three parallel lines of human abdominal SFBLs. Findings showed that GFBLs displayed morphologically distinct organization of the 3D cultures and proliferated faster than SFBLs. GFBLs expressed elevated levels of molecules involved in regulation of inflammation and ECM remodeling (MMPs) while SFBLs showed significantly higher expression of TGF-β signaling, ECM and myofibroblast and cell contractility-related genes. Thus, GFBLs display an inherent phenotype conducive for fast resolution of inflammation and ECM remodeling, characteristic for scar-free wound healing, while SFBLs have a profibrotic, scar-prone phenotype.

New molecular medicine-based scar management strategies

Keloids and hypertrophic scars are prevalent disabling conditions with still suboptimal treatments. Basic science and molecular-based medicine research have contributed to unravel new bench-to-bedside scar therapies and to dissect the complex signalling pathways involved. Peptides such as the transforming growth factor beta (TGF-β) superfamily, with Smads, Ski, SnoN, Fussels, endoglin, DS-Sily, Cav-1p, AZX100, thymosin-β4 and other related molecules may emerge as targets to prevent and treat keloids and hypertrophic scars. The aim of this review is to describe the basic complexity of these new molecular scar management strategies and point out new fibrosis research lines.

Intracellular signaling mechanisms associated with CD47 modified surfaces

We have previously established that recombinant CD47 can ameliorate the inflammatory response to synthetic polymeric surfaces. Here, we begin to profile, at the transcriptional, translational and cell signaling level, the inflammatory cell response when blood interacts with CD47 modified polyvinyl chloride (PVC) (CD47-PVC). We used qPCR arrays to compare transcriptional changes between human whole blood exposed to CD47-PVC or PVC. Transcription of IL1F5, IL1F10, IL17F, CCL3, CCL8, CCL28, CXCL12, and CXCL13 was upregulated in blood exposed to PVC, compared to CD47-PVC. The increase in CCL3 and CCL8 transcription correlated with an increase in the chemokines' presence in the plasma. Exposure of blood to CD47-PVC resulted in an increase, compared to PVC, in transcription of CCL2, CCL4, CCL20, CXCL1, TGFβ3, GDF3, GDF10, CD40LG, and TNFSF10. CD47-PVC exposure resulted in an increase of the following matrix metalloproteinase related genes: MMP1, MMP7, MMP13, and MMP16. Phosflow cytometry, and assays examining transcription factor binding, cell attachment, and genome-wide chromatin association indicated that members of the JAK-STAT signaling pathway, particularly JAK2 and STAT5, mediate inflammatory cell interactions with CD47-PVC. Our data demonstrate that differential molecular responses to CD47 involve downregulation of cytokines, upregulation of MMPs, and JAK/STAT signaling mechanisms.

Dynamics of Transforming Growth Factor Beta Signaling in Wound Healing and Scarring

SIGNIFICANCE

Wound healing is an intricate biological process in which the skin, or any other tissue, repairs itself after injury. Normal wound healing relies on the appropriate levels of cytokines and growth factors to ensure that cellular responses are mediated in a coordinated manner. Among the many growth factors studied in the context of wound healing, transforming growth factor beta (TGF-β) is thought to have the broadest spectrum of effects.

RECENT ADVANCES

Many of the molecular mechanisms underlying the TGF-β/Smad signaling pathway have been elucidated, and the role of TGF-β in wound healing has been well characterized. Targeting the TGF-β signaling pathway using therapeutic agents to improve wound healing and/or reduce scarring has been successful in pre-clinical studies.

CRITICAL ISSUES

Although TGF-β isoforms (β1, β2, β3) signal through the same cell surface receptors, they display distinct functions during wound healing in vivo through mechanisms that have not been fully elucidated. The challenge of translating preclinical studies targeting the TGF-β signaling pathway to a clinical setting may require more extensive preclinical research using animal models that more closely mimic wound healing and scarring in humans, and taking into account the spatial, temporal, and cell-type-specific aspects of TGF-β isoform expression and function.

FUTURE DIRECTIONS

Understanding the differences in TGF-β isoform signaling at the molecular level and identification of novel components of the TGF-β signaling pathway that critically regulate wound healing may lead to the discovery of potential therapeutic targets for treatment of impaired wound healing and pathological scarring.

A Paradigm of Fibroblast Activation and Dermal Wound Contraction to Guide the Development of Therapies for Chronic Wounds and Pathologic Scars

SIGNIFICANCE

Delayed wound healing and pathologic scarring are abnormal processes that can be thought of as occurring on a wound healing continuum, where insufficient wound contraction leads to nonhealing wounds, and overexuberant wound contraction leads to scarring. Chronic nonhealing wounds, including diabetic foot wounds, decubitus ulcers, and venous stasis ulcers, affect millions of people annually in the United States and costs billions of dollars. Similarly, pathologic scaring affects more than 40 million Americans annually and also costs billions of dollars.

CRITICAL ISSUES

While there are multiple factors that contribute to chronic nonhealing wounds and pathologic scars, a derangement in wound contraction is common to both. In this article, we will present a paradigm of dermal wound contraction, derived from clinical observations and basic science evidence, which pertains to chronic nonhealing wounds and pathologic scars.

RECENT ADVANCES

We will review how select therapies currently under investigation and in development fit the paradigm.

FUTURE DIRECTIONS

The paradigm will facilitate translational research and enable the development of future innovative therapies.

Phase 2 cross-over multicenter trial on the efficacy and safety of topical cyanoacrylates compared with topical silicone gel in the prevention of pathologic scars

BACKGROUND

Many clinical studies on scar therapy are reported in the literature, but only silicone gel sheeting and corticosteroid injections are supported by accurate prospective controlled studies. This prospective multicenter cross-over phase 2 study tested the effectiveness of a topical cyanoacrylate compared with silicone gel in improving postsurgical scars

METHODS

Patients presenting with symmetric breast scars after augmentation or reduction mammaplasty were enrolled in the study. From the same day as stitch removal, the cyanoacrylate was applied on one side every 3 to 5 days and the silicone gel on the other side twice a day for 3 months. Assessments of patients and external observers using a visual analog scale were recorded at scheduled visits during 1 year, and scars were photographed. Objective evaluations included measurements of scar width, length, and elevation. The statistical significance of objective parameter modifications was analyzed using the Wilcoxon test

RESULTS

Positive effects of both tested products were observed during the scar maturation process, and final scars of good quality were achieved without any major adverse effect. The topical cyanoacrylate proved to be more efficacious in preventing scar widening, and this result was statistically significant

CONCLUSIONS

The tested topical cyanoacrylate had a positive effect on the scar maturation process at least comparable with that of topical silicone gel.

Applying amphibian limb regeneration to human wound healing: a review

In contrast to the limited regenerative ability found in human wound healing, which often results in unsatisfying and deficient scar formation, urodele amphibians, with the Mexican axolotl as a prime example, expose an extraordinary regenerative capacity. This regeneration leads to a perfect restoration of tissue architecture, function, and aesthetics with the axolotl being actually able to reclaim complete limbs. Evolutionary considerations suggest that regeneration might be a biologic principle which also underlies human wound healing. Experimental findings, such as comparative studies on transforming growth factor-β and fibroblast growth factor accentuate this assumption. Regeneration, as recent data indicate, might be a question of adaptive immunity. The loss of regenerative potency correlates with the decrease of regeneration in most species, whereas the Mexican axolotl lacks adaptive immunity throughout its life. The characterization of molecular pathways as a prerequisite for any control of regenerative processes sets an increasing indication toward the transfer into human beings. Some regenerative techniques, eg, recombinant transforming growth factor-β have already emerged. Molecular findings suggest that there is an intrinsic regenerative capacity in humans which might be initiated under appropriate circumstances. The Mexican axolotl is liable to diverse surgical and molecular approaches. Though well-known among developmental biologists, its exploitation for experimental Plastic Surgery still has to be established. We therefore intend to give an introduction to amphibian regeneration and the common evolutionary roots of regeneration and human wound healing, as we believe that Plastic Surgery takes a unique advantage of performing basic research on amphibian regeneration.

TGF-ß in wound healing: a review

TGF-ß, a growth factor involved in various stages of the wound healing process, exists in three different isoforms. Experimental models have shown these isoforms to be functionally different and one of them, TGF-ß3, has the potential to reduce scarring in clinical practice. This literature review explores the role of TGF- in wound healing, examining the research to date.

Therapies with emerging evidence of efficacy: avotermin for the improvement of scarring

Many patients are dissatisfied with scars on both visible and non-visible body sites and would value any opportunity to improve or minimise scarring following surgery. Approximately 44 million procedures in the US and 42 million procedures in the EU per annum could benefit from scar reduction therapy. A wide range of non-invasive and invasive techniques have been used in an attempt to improve scarring although robust, prospective clinical trials to support the efficacy of these therapies are lacking. Differences in wound healing and scar outcome between early fetal and adult wounds led to interest in the role of the TGFbeta family of cytokines in scar formation and the identification of TGFbeta3 (avotermin) as a potential therapeutic agent for the improvement of scar appearance. Extensive pre-clinical and human Phase I and II clinical trial programmes have confirmed the scar improving efficacy of avotermin which produces macroscopic and histological improvements in scar architecture, with improved restitution of the epidermis and an organisation of dermal extracellular matrix that more closely resembles normal skin. Avotermin is safe and well tolerated and is currently in Phase III of clinical development, with the first study, in patients undergoing scar revision surgery, fully recruited.

Biological agents for controlling excessive scarring

The potential of various biological agents to reduce or prevent excessive scar formation has now been evaluated in numerous in-vitro studies, experimental animal models and preliminary clinical trials, in some cases with particularly promising results. Perhaps prominent among this group of biological agents, and, to some degree, possibly representing marketed compounds already being used 'off label' to manage excessive scarring, are the tumor necrosis factor alpha antagonist etanercept, and immune-response modifiers such as IFNalpha2b and imiquimod. Additional assessment of these novel agents is now justified with a view to reducing or preventing hypertrophic scars, keloid scars and the recurrence of post-excision keloid lesions.

Extracellular matrix molecules: potential targets in pharmacotherapy

The extracellular matrix (ECM) consists of numerous macromolecules classified traditionally into collagens, elastin, and microfibrillar proteins, proteoglycans including hyaluronan, and noncollagenous glycoproteins. In addition to being necessary structural components, ECM molecules exhibit important functional roles in the control of key cellular events such as adhesion, migration, proliferation, differentiation, and survival. Any structural inherited or acquired defect and/or metabolic disturbance in the ECM may cause cellular and tissue alterations that can lead to the development or progression of disease. Consequently, ECM molecules are important targets for pharmacotherapy. Specific agents that prevent the excess accumulation of ECM molecules in the vascular system, liver, kidney, skin, and lung; alternatively, agents that inhibit the degradation of the ECM in degenerative diseases such as osteoarthritis would be clinically beneficial. Unfortunately, until recently, the ECM in drug discovery has been largely ignored. However, several of today's drugs that act on various primary targets affect the ECM as a byproduct of the drugs' actions, and this activity may in part be beneficial to the drugs' disease-modifying properties. In the future, agents and compounds targeting directly the ECM will significantly advance the treatment of various human diseases, even those for which efficient therapies are not yet available.

Scar and contracture: biological principles

Dysregulated wound healing and pathologic fibrosis cause abnormal scarring, leading to poor functional and aesthetic results in hand burns. Understanding the underlying biologic mechanisms involved allows the hand surgeon to better address these issues, and suggests new avenues of research to improve patient outcomes. In this article, the authors review the biology of scar and contracture by focusing on potential causes of abnormal wound healing, including depth of injury, cytokines, cells, the immune system, and extracellular matrix, and explore therapeutic measures designed to target the various biologic causes of poor scar.

Scarless healing of oral mucosa is characterized by faster resolution of inflammation and control of myofibroblast action compared to skin wounds in the red Duroc pig model

BACKGROUND

Scar formation following skin trauma can have devastating consequences causing physiological and psychosocial concerns. Currently, there are no accepted predictable treatments to prevent scarring which emphasizes a need for a better understanding of the wound healing and scar formation process.

OBJECTIVES

Previously it was shown that healing of small experimental wounds in the oral mucosa of red Duroc pigs results in significantly reduced scar formation as compared with equivalent full-thickness skin wounds. In the present study, scar formation was assessed in 17 times larger experimental wounds in both oral mucosa and skin of the red Duroc pigs.

METHODS

Equivalent experimental wounds were created in the oral mucosa and dorsal skin of red Duroc pigs, and scar formation, localization and abundance of key wound healing cells, transforming growth factor-beta (TGF-beta) and phosphorylated Smad3 (pSmad3) were assessed.

RESULTS

Oral mucosal wounds displayed significantly less clinical and histological scar formation than did the corresponding skin wounds. The number of macrophages, mast cells, TGF-beta and pSmad3 immunopositive cells was significantly reduced in the oral mucosal wounds as compared with skin wounds during the maturation stage of the healing process. Although the number of myofibroblasts was significantly elevated, the oral mucosal wounds showed significantly less contraction than did the skin wounds over time.

CONCLUSIONS

Earlier resolution of the inflammatory reaction and reduced wound contraction may promote scarless oral mucosal wound healing. In addition, scar formation likely depends not only on the number of myofibroblasts but also on the extracellular environment which regulates their function.