Upregulation of secretory connective tissue growth factor (CTGF) in keratinocyte-fibroblast coculture contributes to keloid pathogenesis

Parecoxib decreases cellular growth and Bcl-2 protein levels in primary cultures of keloid fibroblasts

Keloids seem to overexpress cyclo-oxygenase-2 (COX-2), suggesting a role in its deregulated pathway in inducing an altered epithelial-mesenchymal interaction, which may be responsible for the overgrowth of dermal components resulting in scars or keloid lesions. This study aimed to evaluate the effect of Parecoxib, a COX-2 inhibitor, on cell growth in fibroblast primary cultures obtained from human keloid tissues. Tissue explants were obtained from patients who underwent intralesional excision of untreated keloids; central fractions were isolated from keloid tissues and used for establishing distinct primary cultures. Appropriate aliquots of Parecoxib, a COX-2 inhibitor were diluted to obtain the concentration used in the experimental protocols in vitro (1, 10 or 100 μM). Treatment with Parecoxib (at all concentrations) caused a significant decrease in cellular growth from 24 hours onwards, and with a maximum at 72 hours (P < .02). Moreover, at 72 hours Parecoxib significantly reduced cellular vitality. Parecoxib treatment also induced an increase in fragmented nuclei with a maximum effect at 100 μM and a significant decrease in Bcl-2 and an increase in activated caspase-3 protein levels at 72 hours compared with control untreated cultures. Our findings suggest a potential use of the COX-2 inhibitor, Parecoxib, as the therapy for keloids.

Systemic Fibrocyte Levels and Keloid Expression of the Chemoattractant CXCL12 Are Upregulated Compared With Patients With Normal Scar

BACKGROUND

Fibrocytes are bone marrow mesenchymal precursors with a surface phenotype compatible with leukocytes, fibroblasts, and hematopoietic progenitors that have been shown to traffic to wound healing sites in response to described chemokine pathways. Keloids are focal fibrotic responses to cutaneous trauma characterized by disordered collagen, which may be associated with elevated systemic fibrocyte levels and/or wound bed chemokine expression.

METHODS

Blood specimens from patients with longstanding keloids and those who form grossly normal scars were assayed by fluorescence activated cell sorting analysis for fibrocytes (CD45+, Col I+). The expression of the fibrocyte chemotactic cell surface marker CXCR4, intracellular markers of fibroblast differentiation (pSMAD2/3), and plasma levels of the CXCR4 cognate CXCL12 were compared. Keloid specimens and grossly normal scars were excised, and local expression of CXCL12 was assayed.

RESULTS

Keloid-forming patients demonstrated a significantly greater number of circulating fibrocytes (17.4 × 105 cells/mL) than control patients (1.01 × 105 cells/mL, P = 0.004). The absolute number of fibrocytes expressing CXCR4 was significantly greater (P = 0.012) in keloid-forming patients. Systemic CXCL12 levels were insignificantly greater in keloid-forming patients than controls. Keloid specimens had significantly greater CXCL12 expression (529.3 pg/mL) than normal scar (undetectable).

CONCLUSIONS

Systemic fibrocyte levels and the CXCR4/CXCL12 biologic axis responsible for fibrocyte trafficking to areas of regional fibrosis were both upregulated in patients who form keloids compared with controls. Keloids persistently expressed CXLC12, which serves both as the main chemoattractant for fibrocytes and a downstream mediator for local inflammation, suggesting a role for this biologic axis in keloid formation and possibly recurrence.

hTERT-Driven Immortalization of RDEB Fibroblast and Keratinocyte Cell Lines Followed by Cre-Mediated Transgene Elimination

The recessive form of dystrophic epidermolysis bullosa (RDEB) is a crippling disease caused by impairments in the junctions of the dermis and the basement membrane of the epidermis. Using ectopic expression of hTERT/hTERT + BMI-1 in primary cells, we developed expansible cultures of RDEB fibroblasts and keratinocytes. We showed that they display the properties of their founders, including morphology, contraction ability and expression of the respective specific markers including reduced secretion of type VII collagen (C7). The immortalized keratinocytes retained normal stratification in 3D skin equivalents. The comparison of secreted protein patterns from immortalized RDEB and healthy keratinocytes revealed the differences in the contents of the extracellular matrix that were earlier observed specifically for RDEB. We demonstrated the possibility to reverse the genotype of immortalized cells to the state closer to the progenitors by the Cre-dependent hTERT switch off. Increased β-galactosidase activity and reduced proliferation of fibroblasts were shown after splitting out of transgenes. We anticipate our cell lines to be tractable models for studying RDEB from the level of single-cell changes to the evaluation of 3D skin equivalents. Our approach permits the creation of standardized and expandable models of RDEB that can be compared with the models based on primary cell cultures.

MiR-133a-3p inhibits scar formation in scalded mice and suppresses the proliferation and migration of scar derived-fibroblasts by targeting connective tissue growth factor

Excessive scar formation post burn injury can cause great pain to the patients. MiR-133a-3p has been demonstrated to be anti-fibrotic in some fibrosis-related diseases. However, its possible role in scar formation has not been elucidated yet. In present study, the effect of miR-133a-3p on scar formation was investigated in a scalded model of mice. Moreover, the function of miR-133a-3p on proliferation and migration of scar-derived fibroblasts (SFs) was studied in vitro. It was found that miR-133a-3p was dramatically downregulated in scar tissue of scalded mice. Upregulation of miR-133a-3p by miR-133a-3p agomir obviously inhibited the scar formation in scalded mice. Histological staining showed that upregulation of miR-133a-3p attenuated the excessive deposition of collagen in scar tissue of scalded mice. In vitro study showed that upregulation of miR-133a-3p effectively suppressed the proliferation and migration of SFs. Besides, upregulation of miR-133a-3p attenuated the protein levels of α-smooth muscle actin (α-SMA) and collagen I, indicating that miR-133a-3p could suppress the activation of SFs. The expression of connective tissue growth factor (CTGF), a critical mediator in cell proliferation, migration and extracellular matrix (ECM) synthesis, was also downregulated by the upregulation of miR-133a-3p. Luciferase reporter assay validated that CTGF was directly targeted by miR-133a-3p. In addition, overexpression of CTGF abolished the effect of miR-133a-3p on inhibiting the proliferation, migration and activation of SFs, indicating that miR-133a-3p functioned by targeting CTGF. Therefore, miR-133a-3p might be a promising target for treating pathological scars.

The Keloid Disorder: Heterogeneity, Histopathology, Mechanisms and Models

Keloids constitute an abnormal fibroproliferative wound healing response in which raised scar tissue grows excessively and invasively beyond the original wound borders. This review provides a comprehensive overview of several important themes in keloid research: namely keloid histopathology, heterogeneity, pathogenesis, and model systems. Although keloidal collagen versus nodules and α-SMA-immunoreactivity have been considered pathognomonic for keloids versus hypertrophic scars, conflicting results have been reported which will be discussed together with other histopathological keloid characteristics. Importantly, histopathological keloid abnormalities are also present in the keloid epidermis. Heterogeneity between and within keloids exists which is often not considered when interpreting results and may explain discrepancies between studies. At least two distinct keloid phenotypes exist, the superficial-spreading/flat keloids and the bulging/raised keloids. Within keloids, the periphery is often seen as the actively growing margin compared to the more quiescent center, although the opposite has also been reported. Interestingly, the normal skin directly surrounding keloids also shows partial keloid characteristics. Keloids are most likely to occur after an inciting stimulus such as (minor and disproportionate) dermal injury or an inflammatory process (environmental factors) at a keloid-prone anatomical site (topological factors) in a genetically predisposed individual (patient-related factors). The specific cellular abnormalities these various patient, topological and environmental factors generate to ultimately result in keloid scar formation are discussed. Existing keloid models can largely be divided into in vivo and in vitro systems including a number of subdivisions: human/animal, explant/culture, homotypic/heterotypic culture, direct/indirect co-culture, and 3D/monolayer culture. As skin physiology, immunology and wound healing is markedly different in animals and since keloids are exclusive to humans, there is a need for relevant human in vitro models. Of these, the direct co-culture systems that generate full thickness keloid equivalents appear the most promising and will be key to further advance keloid research on its pathogenesis and thereby ultimately advance keloid treatment. Finally, the recent change in keloid nomenclature will be discussed, which has moved away from identifying keloids solely as abnormal scars with a purely cosmetic association toward understanding keloids for the fibroproliferative disorder that they are.

RNAi nanotherapy for fibrosis: highly durable knockdown of CTGF/CCN-2 using siRNA-DegradaBALL (LEM-S401) to treat skin fibrotic diseases

Skin fibrosis occurs in a variety of human diseases but the current anti-fibrosis treatments are not sufficient. One major cause of fibrotic diseases shared across diverse organ fibrosis is uncontrolled overexpression of the connective tissue growth factor (CTGF, also known as CCN2). Here, we examine the anti-fibrotic activity of RNAi therapy utilizing siRNA against CTGF with a new drug delivery system (DDS), 'DegradaBALL', which is based on porous nanoparticles, for durable CTGF gene silencing. DegradaBALL is a modular DDS having many favorable properties for RNA delivery such as effective intracellular uptake, convenient drug loading, biocompatibility, sustained release profile and biodegradability. DegradaBALL loaded with siCTGF, named 'LEM-S401', showed highly durable and effective CTGF gene-silencing in TGF-β induced lung fibrosis and skin fibrosis model cells, A549 and HaCaT, respectively. In addition, LEM-S401 induced knockdown of collagen types I and III, which are excess extracellular matrix components in fibrotic skin in addition to CTGF in the mouse wound healing model. Most importantly, we showed that LEM-S401 effectively inhibited the formation of hypertrophic scars in wound-associated dermal fibrosis mouse models, during both the epidermis recovery and tissue remodeling process. Our findings suggest that LEM-S401 could be a highly potent therapeutic option for skin fibrotic diseases.

Smad interacting protein 1 influences transforming growth factor-β1/Smad signaling in extracellular matrix protein production and hypertrophic scar formation

The transforming growth factor (TGF)-β/Smad signal transduction pathway is closely associated with hypertrophic scar (HS) formation. Smad interacting protein 1 (SIP1) is a cytoplasmic protein that efficiently regulates Smad2-/3-dependent signaling within the TGF-β₁ pathway. SIP1 influences collagen synthesis in the HS through a heretofore unknown mechanism. This study investigated the role of the SIP1-mediated TGF-β₁/Smad signaling pathway in extracellular matrix (ECM) protein production and hypertrophic scarring. SIP1 expression was markedly lower in HS vs. normal skin (NS) tissue, and α-smooth muscle actin (α-SMA) content and collagen I/III (Col I/III) synthesis were inversely correlated with SIP1 expression. Furthermore, SIP1 inhibited Smad2/3 phosphorylation in vitro, and improved the collagen-based architecture of the scar while reducing collagen expression and overall scar formation in a rabbit ear model of HS. Based on these findings, we propose that SIP1 acts as a molecular modulator capable of altering Smad2-/3-facilitated signaling through the control of Smad phosphorylation, thus inhibiting α-SMA and collagen upregulation in fibroblasts and, ultimately, HS formation. The low SIP1 content in scar tissue also suggests that SIP1 (and positive regulation thereof) is a prospective target for selective HS drug therapy.

Targeting mTORC1/2 with OSI-027 inhibits proliferation and migration of keloid keratinocytes

Keloid is a dermal proliferative disorder characterized by the excessive proliferation and migration of keratinocytes and fibroblasts. Over-activation of the serine/threonine protein kinase, mammalian target of rapamycin (mTOR), plays a pivotal role in the process. Here, we show that both mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2) were hyper-activated in keloid-derived primary keratinocytes. Further, OSI-027, an mTOR kinase inhibitor, potently inhibited proliferation and migration of keloid keratinocytes. At the molecular level, OSI-027 disrupted the assembly of mTORC1 (mTOR-Raptor) and mTORC2 (mTOR-Rictor-mLST8). Further, OSI-027 almost completely blocked the phosphorylation of the mTORC1 substrates, S6K1, S6 and 4EBP1, and the mTORC2 substrate, AKT, at Ser-473. The OSI-027 treatment of keloid keratinocytes showed more effectively inhibited cell proliferation and migration compared to the mTORC1 inhibitor, rapamycin. Moreover, restoring mTORC1 activation by the introduction of the constitutively active S6K1 only partly alleviated OSI-027-induced inhibition of keloid keratinocytes. Notably, mTOR2 inhibition by Rictor siRNAs also inhibited keloid keratinocyte proliferation and migration, but less efficiently than OSI-027. Together, our results imply that concurrent targeting of mTORC1/2 by OSI-027 potently inhibits the proliferation and the migration of keloid keratinocytes. Thus, OSI-027 may have translational value for the treatment of keloid.

Construction of histidine-containing hydrocarbon stapled cell penetrating peptides for in vitro and in vivo delivery of siRNAs

A hydrocarbon stapled peptide based strategy was used to develop an optimized cell penetrating peptide for siRNA delivery. Various stapled peptides, having amphipathic Leu- and Lys-rich regions, were prepared and their cell penetrating potentials were evaluated. One peptide, stEK, was found to have high cell penetration and siRNA delivery abilities at low nanomolar concentrations. In order to improve its ability to promote gene silencing, stEK was modified by replacing several Lys residues with His moieties. The modified peptide, LKH-stEK, was found to facilitate endosomal escape and to display >90% knock-down with 50 nM of a siRNA targeting cyclophilin B in HeLa cells. The results of an in vivo animal wound healing model study demonstrate that LKH-stEK promotes delivery of an siRNA, which targets the connective tissue growth factor, and that this process leads to efficient gene silencing by the siRNA at a nanomolar level in mouse skin.

Ginsenoside Rg3 inhibits keloid fibroblast proliferation, angiogenesis and collagen synthesis in vitro via the TGF‑β/Smad and ERK signaling pathways

A wide range of therapeutic options exists for the treatment of keloids, all of which have their own strengths; however, a high risk of side-effects and frequent recurrence remains. Therefore, the present study aimed to identify improved therapeutic approaches or drugs for the treatment of keloids. Ginsenoside Rg3 (Rg3) has been reported to exert numerous antitumor effects, thus indicating that Rg3 may be a potential therapeutic agent that targets keloids. The present study determined the effects of Rg3 on human keloid fibroblasts (KFs) in vitro, and further explored the associated molecular and cellular mechanisms. Keloid scar specimens were obtained from patients, aged between 22 and 35 years, without systemic diseases and primary cells were isolated from keloid tissues. In each assay, KFs were divided into three groups and were cultured in medium with or without various concentrations of Rg3 (50 or 100 μg/ml). Cell viability assay, flow cytometry, quantitative polymerase chain reaction, cell migration assay, immunofluorescence staining, western blot analysis, Transwell cell invasion assay and immunohistochemical analysis were used to analyze the KFs and keloid explant cultures. The results of the present study demonstrated that Rg3 was able to exert an inhibitory effect on the transforming growth factor-β/Smad and extracellular signal-regulated kinase signaling pathways in KFs. The proliferation, migration, invasion, angiogenesis and collagen synthesis of KFs were markedly suppressed following treatment with Rg3. Furthermore, the results of an ex vivo assay indicated that Rg3 inhibited angiogenesis and reduced collagen accumulation in keloids. Significant statistical differences existed between the control and Rg3-treated groups (P<0.05). All of these experimental results suggested that Rg3 may serve as a reliable drug for the treatment of patients with keloids.

Immunohistochemical Evaluation of Leptin Expression in Wound Healing: A Clue to Exuberant Scar Formation

Leptin has been recognized as an important factor for promoting normal cutaneous wound healing. The aim of this work was to explore leptin expression in keloid and hypertrophic scars (HS) compared with surgical scars and normal skin. The relationship of this expression with clinicopathologic parameters of studied cases was also evaluated. Using immunohistochemical techniques, leptin was analyzed in skin biopsies of 60 nonobese subjects without metabolic syndrome who presented with keloids (20), HS (20), and surgical scars (20). Twenty normal skin samples, from age-matched, sex-matched, and body mass index-matched subjects, were enrolled as a control group. Leptin showed positive immunoreactivity in epidermis in all cases of surgical scars and keloids and in 75% of HS cases. Dermal expression in fibroblasts, inflammatory cells, and endothelial cells was positive in all cases of surgical scars and keloids and in 70% of HS cases. Leptin was overexpressed in keloids and HS compared with normal skin in epidermis (P<0.001 for both) and dermis (P<0.001 for both) and to surgical scars both in epidermis (P=0.0006, P=0.01, respectively) and dermis (P=0.0001, P=0.001, respectively). Higher leptin H score was significantly associated with older age (P=0.02) and positive family history (P=0.002) in keloid cases and with axial site in keloid and HS cases (P=0.001, P=0.02, respectively). Significant positive correlation was noted between epidermal and dermal leptin H scores in keloids (r=+0.37, P=0.04) and HS (r=+0.39, P=0.02). This may be due to epithelial-mesenchymal interactions in scar pathogenesis. In conclusion, in situ leptin overexpression may increase the possibility of keloid and HS occurrence through altered cytokine production and prolonged healing phases with excessive deposition and delayed collagen degradation. This may open an avenue for research for new therapeutic modalities based on its inhibition.

Development of Cell-Penetrating Asymmetric Interfering RNA Targeting Connective Tissue Growth Factor

Connective tissue growth factor (CTGF) is a multifunctional matricellular protein, playing a role as a central mediator in tissue remodeling and fibrosis. A number of reports have shown the pivotal roles of CTGF in the progression of fibrosis, suggesting CTGF as a promising therapeutic target for the treatment of fibrotic disorders including hypertrophic scars and keloids. In this study, we present the development of an interfering RNA molecule that efficiently inhibits the expression of CTGF via RNA interference mechanism both in vitro and in vivo. Chemical modifications were introduced to the asymmetric interfering RNA (asiRNA) backbone structure. The resulting RNA molecule, termed cell-penetrating asiRNA (cp-asiRNA), entered into cells and triggered RNA interference-mediated gene silencing without delivery vehicles. The gene-silencing activity of cp-asiRNA targeting CTGF (cp-asiCTGF) was examined both in vitro and in vivo. Furthermore, the administration of cp-asiCTGF in the rat skin excision wound model efficiently reduced the induction of CTGF and collagens during the wound-healing process. These results suggest that the cp-asiCTGF molecule could be developed into antifibrotic therapeutics such as antiscar drugs.

Keloids and Hypertrophic Scars: A Spectrum of Clinical Challenges

Since their earliest description, keloids and hypertrophic scars have beleaguered patients and clinicians alike. These scars can be aesthetically disfiguring, functionally debilitating, emotionally distressing, and psychologically damaging, culminating in a significant burden for patients. Our current understanding of keloid pathophysiology has grown and continues to advance while molecular biology, genetics, and technology provide ever-deepening insight into the nature of wound healing and the pathologic perturbations thereof. Greater understanding will lead to the development and application of refined therapeutic modalities. This article provides an overview of our current understanding of keloids, highlighting clinical characteristics and diagnostic criteria while providing a comprehensive summary of the many therapeutic modalities available. The proposed mechanism, application, adverse events, and reported efficacy of each modality is evaluated, and current recommendations are summarized.

Visible Red Light Emitting Diode Photobiomodulation for Skin Fibrosis: Key Molecular Pathways

Skin fibrosis, also known as skin scarring, is an important global health problem that affects an estimated 100 million persons per year worldwide. Current therapies are associated with significant side effects and even with combination therapy, progression, and recurrence is common. Our goal is to review the available published data available on light-emitting diode-generated (LED) red light phototherapy for treatment of skin fibrosis. A search of the published literature from 1 January 2000 to present on the effects of visible red light on skin fibrosis, and related pathways was performed in January 2016. A search of PubMed and EMBASE was completed using specific keywords and MeSH terms. "Fibrosis" OR "skin fibrosis" OR "collagen" was combined with ("light emitting diode," "LED," "laser," or "red light"). The articles that were original research studies investigating the use of visible red light to treat skin fibrosis or related pathways were selected for inclusion. Our systematic search returned a total of 1376 articles. Duplicate articles were removed resulting in 1189 unique articles, and 133 non-English articles were excluded. From these articles, we identified six articles related to LED effects on skin fibrosis and dermal fibroblasts. We augmented our discussion with additional in vitro data on related pathways. LED phototherapy is an emerging therapeutic modality for treatment of skin fibrosis. There is a growing body of evidence demonstrating that visible LED light, especially in the red spectrum, is capable of modulating key cellular characteristic associated with skin fibrosis. We anticipate that as the understanding of LED-RL's biochemical mechanisms and clinical effects continue to advance, additional therapeutic targets in related pathways may emerge. We believe that the use of LED-RL, in combination with existing and new therapies, has the potential to alter the current treatment paradigm of skin fibrosis. There is a current lack of clinical trials investigating the efficacy of LED-RL to treat skin fibrosis. Randomized clinical trials are needed to demonstrate visible red light's clinical efficacy on different types of skin fibrosis.

Nanolayered siRNA delivery platforms for local silencing of CTGF reduce cutaneous scar contraction in third-degree burns

Wound healing is an incredibly complex biological process that often results in thickened collagen-enriched healed tissue called scar. Cutaneous scars lack many functional structures of the skin such as hair follicles, sweat glands, and papillae. The absence of these structures contributes to a number of the long-term morbidities of wound healing, including loss of function for tissues, increased risk of re-injury, and aesthetic complications. Scar formation is a pervasive factor in our daily lives; however, in the case of serious traumatic injury, scars can create long-lasting complications due to contraction and poor tissue remodeling. Within this report we target the expression of connective tissue growth factor (CTGF), a key mediator of TGFβ pro-fibrotic response in cutaneous wound healing, with controlled local delivery of RNA interference. Through this work we describe both a thorough in vitro analysis of nanolayer coated sutures for the controlled delivery of siRNA and its application to improve scar outcomes in a third-degree burn induced scar model in rats. We demonstrate that the knockdown of CTGF significantly altered the local expression of αSMA, TIMP1, and Col1a1, which are known to play roles in scar formation. The knockdown of CTGF within the healing burn wounds resulted in improved tissue remodeling, reduced scar contraction, and the regeneration of papillary structures within the healing tissue. This work adds support to a number of previous reports that indicate CTGF as a potential therapeutic target for fibrosis. Additionally, we believe that the controlled local delivery of siRNA from ultrathin polymer coatings described within this work is a promising approach in RNA interference that could be applied in developing improved cancer therapies, regenerative medicine, and fundamental scientific research.

MicroRNA-143-3p inhibits hyperplastic scar formation by targeting connective tissue growth factor CTGF/CCN2 via the Akt/mTOR pathway

Post-traumatic hypertrophic scar (HS) is a fibrotic disease with excessive extracellular matrix (ECM) production, which is a response to tissue injury by fibroblasts. Although emerging evidence has indicated that miRNA contributes to hypertrophic scarring, the role of miRNA in HS formation remains unclear. In this study, we found that miR-143-3p was markedly downregulated in HS tissues and fibroblasts (HSFs) using qRT-PCR. The expression of connective tissue growth factor (CTGF/CCN2) was upregulated both in HS tissues and HSFs, which is proposed to play a key role in ECM deposition in HS. The protein expression of collagen I (Col I), collagen III (Col III), and α-smooth muscle actin (α-SMA) was obviously inhibited after treatment with miR-143-3p in HSFs. The CCK-8 assay showed that miR-143-3p transfection reduced the proliferation ability of HSFs, and flow cytometry showed that either early or late apoptosis of HSFs was upregulated by miR-143-3p. In addition, the activity of caspase 3 and caspase 9 was increased after miR-143-3p transfection. On the contrary, the miR-143-3p inhibitor was demonstrated to increase cell proliferation and inhibit apoptosis of HSFs. Moreover, miR-143-3p targeted the 3'-UTR of CTGF and caused a significant decrease of CTGF. Western blot demonstrated that Akt/mTOR phosphorylation and the expression of CTGF, Col I, Col III, and α-SMA were inhibited by miR-143-3p, but increased by CTGF overexpression. In conclusion, we found that miR-143-3p inhibits hypertrophic scarring by regulating the proliferation and apoptosis of human HSFs, inhibiting ECM production-associated protein expression by targeting CTGF, and restraining the Akt/mTOR pathway.

The Aldo-Keto Reductase AKR1B10 Is Up-Regulated in Keloid Epidermis, Implicating Retinoic Acid Pathway Dysregulation in the Pathogenesis of Keloid Disease

Keloid disease is a recurrent fibroproliferative cutaneous tumor of unknown pathogenesis for which clinical management remains unsatisfactory. To obtain new insights into hitherto underappreciated aspects of keloid pathobiology, we took a laser capture microdissection-based, whole-genome microarray analysis approach to identify distinct keloid disease-associated gene expression patterns within defined keloid regions. Identification of the aldo-keto reductase enzyme AKR1B10 as highly up-regulated in keloid epidermis suggested that an imbalance of retinoic acid metabolism is likely associated with keloid disease. Here, we show that AKR1B10 transfection into normal human keratinocytes reproduced the abnormal retinoic acid pathway expression pattern we had identified in keloid epidermis. Cotransfection of AKR1B10 with a luciferase reporter plasmid showed reduced retinoic acid response element activity, supporting the hypothesis of retinoic acid synthesis deficiency in keloid epidermis. Paracrine signals released by AKR1B10-overexpressing keratinocytes into conditioned medium resulted in up-regulation of transforming growth factor-β1, transforming growth factor-β2, and collagens I and III in both keloid and normal skin fibroblasts, mimicking the typical profibrotic keloid profile. Our study results suggest that insufficient retinoic acid synthesis by keloid epidermal keratinocytes may contribute to the pathogenesis of keloid disease. We refocus attention on the role of injured epithelium in keloid disease and identify AKR1B10 as a potential new target in future management of keloid disease.

The effect of 595 nm pulsed dye laser on connective tissue growth factor (CTGF) expression in cultured keloid fibroblasts

OBJECTIVE

To investigate the effect of pulsed dye laser (PDL 595 nm) on the proliferation and expression of connective tissue growth factor (CTGF) in cultured keloid fibroblasts.

MATERIALS AND METHODS

Cultured keloid fibroblasts were exposed to pulsed dye laser irradiation at fluences of 6, 8, and 10 J/cm(2) , with pulse durations of 1.5, 3, and 10 ms. The viability of keloid fibroblasts was measured with CCK-8 at 72, 24, and 12 hours prior to irradiation. Subsequently, viability was measured at 12, 24, and 72 hours post-irradiation. Additionally, the fibroblast cell cycle and apoptosis rate were measured by flow cytometry. Finally, keloid fibroblasts underwent real-time polymerase chain reaction (PCR) and Western blot to investigate the CTGF mRNA and protein expression after PDL irradiation. The untreated cultured keloid fibroblasts served as controls.

RESULTS

The proliferation of keloid fibroblasts was significantly inhibited after PDL irradiation. Both CTGF mRNA and protein expression were significantly down-regulated in 1.5, 3, and 10 ms pulse duration groups, in a dose dependent manner (P < 0.05). However, there was no statistically significant difference between groups of different pulse duration in 6, 8, and 10 J/cm(2) fluence ranges (P > 0.05).

CONCLUSIONS

Within certain fluence ranges, pulsed dye laser can effectively suppress the growth of keloids and significantly down-regulate CTGF mRNA and CTGF expression.

Aspidin PB, a novel natural anti-fibrotic compound, inhibited fibrogenesis in TGF-β1-stimulated keloid fibroblasts via PI-3K/Akt and Smad signaling pathways

Keloid is an overgrowth of scar tissue that develops around a wound. The mechanisms of keloid formation and development still remain unknown, and no effective treatment is available. Searching for active natural resources may develop better prevention and treatment approaches for keloids. Aspidin PB is a natural resource with lower toxicity. We explored its effect on the regulation of TGF-β1-induced expression of type I collagen, CTGF, and α-SMA in keloid fibroblasts (KFs). Western blotting was used to detect the expression levels of type I collagen, CTGF, α-SMA, PI-3K/Akt and Smad-dependent and Smad-independent signaling pathway. The effect of aspidin PB on cell viability in human keloid fibroblasts was measured by MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide). The percentage of the apoptotic cells was studied by flow cytometry. Based on our results, we revealed that aspidin PB inhibited the production of type I collagen, CTGF, and α-SMA in TGF-β1-induced KFs by blocking PI-3K/Akt signaling pathway. The TGF-β1-mediated phosphorylated levels of Smad2/3 were inhibited by aspidin PB pretreatment. Conclusively, our study suggests that aspidin PB has an inhibitory effect on fibrogenesis in TGF-β1-induced KFs. Our findings imply that aspidin PB has a therapeutic potential to intervene and prevent keloids and other fibrotic diseases.

Human hypertrophic and keloid scar models: principles, limitations and future challenges from a tissue engineering perspective

Most cutaneous wounds heal with scar formation. Ideally, an inconspicuous normotrophic scar is formed, but an abnormal scar (hypertrophic scar or keloid) can also develop. A major challenge to scientists and physicians is to prevent adverse scar formation after severe trauma (e.g. burn injury) and understand why some individuals will form adverse scars even after relatively minor injury. Currently, many different models exist to study scar formation, ranging from simple monolayer cell culture to 3D tissue-engineered models even to humanized mouse models. Currently, these high-/medium-throughput test models avoid the main questions referring to why an adverse scar forms instead of a normotrophic scar and what causes a hypertrophic scar to form rather than a keloid scar and also, how is the genetic predisposition of the individual and the immune system involved. This information is essential if we are to identify new drug targets and develop optimal strategies in the future to prevent adverse scar formation. This viewpoint review summarizes the progress on in vitro and animal scar models, stresses the limitations in the current models and identifies the future challenges if scar-free healing is to be achieved in the future.

Expression of insulin-like growth factor-1 receptor in keloid and hypertrophic scar

BACKGROUND

Keloid and hypertrophic scar (HS) are two pathological forms of excessive dermal fibrosis, which are due to aberrant wound-healing responses. Accumulating evidence suggests that aberrant activity of growth factors and increased numbers of growth factor receptors play an important role in the formation of pathological scar.

AIM

We examined the expression level of insulin-like growth factor-1 receptor (IGF-IR) in keloid, HS and normal skin.

METHODS

IGF-IR expression was analyzed by immunohistochemistry, real-time PCR and western blotting on tissues and fibroblasts from 30 patients, comprising 10 patients with keloid and 20 with HS (10 with immature and 10 with mature HS), and from 10 age-matched and sex-matched healthy controls.

RESULTS

Immunoreactivity to IGF-IR was found in dermal fibroblasts of keloid (90%), immature HS, (80%) and mature HS (30%), but not in normal skin. There was no statistically significant difference in immunoreactivity scores between keloid and immature HS, but there was a significant difference (P < 0.01) between mature and immature HS. Real-time PCR and western blot analysis confirmed that there was high expression of IGF-IR in keloid and immature HS fibroblasts, but not in mature HS or normal skin fibroblasts. IGF-IR was expressed in the overlying epidermis, and there was no significant difference between the groups.

CONCLUSIONS

IGF-IR may be involved in the pathogenesis of keloid and HS. Given that IGF-IR are predominantly expressed on dermal fibroblasts, targeting of IGF-IR in fibroblasts may be of benefit to prevent scarring.

Simvastatin inhibits transforming growth factor-β1-induced expression of type I collagen, CTGF, and α-SMA in keloid fibroblasts

Simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme-A reductase inhibitor, is used to reduce cholesterol levels. Accumulating evidence has revealed the immunomodulatory and anti-inflammatory effects of simvastatin that prevent cardiovascular diseases. In addition, the beneficial effects of statins on fibrosis of various organs have been reported. However, the functional effect of statins on dermal fibrosis of keloids has not yet been explored. The objective of this study was to determine whether simvastatin could affect dermal fibrosis associated with keloids. We examined the effect of simvastatin on transforming growth factor (TGF)-β1-induced production of type I collagen, connective tissue growth factor (CTGF or CCN2), and α-smooth muscle actin (α-SMA). Keloid fibroblasts were cultured and exposed to different concentrations of simvastatin in the presence of TGF-β1, and the effects of simvastatin on TGF-β1-induced collagen and CTGF production in keloid fibroblasts were determined. The type I collagen, CTGF, and α-SMA expression levels and the Smad2 and Smad3 phosphorylation levels were assessed by Western blotting. The effect of simvastatin on cell viability was evaluated by assessing the colorimetric conversion of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide. Simvastatin suppressed TGF-β1-induced type I collagen, CTGF, and α-SMA production in a concentration-dependent manner. The TGF-β1-induced Smad2 and Smad3 phosphorylation levels were abrogated by simvastatin pretreatment. The inhibition of type I collagen, CTGF, and α-SMA expression by simvastatin was reversed by geranylgeranyl pyrophosphate, suggesting that the simvastatin-induced cellular responses were due to inhibition of small GTPase Rho involvement. A RhoA activation assay showed that preincubation with simvastatin significantly blocked TGF-β1-induced RhoA activation. The Rho-associated coiled kinase inhibitor Y27632 abrogated TGF-β1-induced production of type I collagen, CTGF, and α-SMA. However, Y27632 had no significant effect on TGF-β1-induced phosphorylation of Smad2 and Smad3. In conclusion, the present study suggests that simvastatin is an effective inhibitor of TGF-β1-induced type I collagen, CTGF, and α-SMA production in keloid fibroblasts.

Site-specific keloid fibroblasts alter the behaviour of normal skin and normal scar fibroblasts through paracrine signalling

Keloid disease (KD) is an abnormal cutaneous fibroproliferative disorder of unknown aetiopathogenesis. Keloid fibroblasts (KF) are implicated as mediators of elevated extracellular matrix deposition. Aberrant secretory behaviour by KF relative to normal skin fibroblasts (NF) may influence the disease state. To date, no previous reports exist on the ability of site-specific KF to induce fibrotic-like phenotypic changes in NF or normal scar fibroblasts (NS) by paracrine mechanisms. Therefore, the aim of this study was to investigate the influence of conditioned media from site-specific KF on the cellular and molecular behaviour of both NF and NS enabled by paracrine mechanisms. Conditioned media was collected from cultured primary fibroblasts during a proliferative log phase of growth including: NF, NS, peri-lesional keloid fibroblasts (PKF) and intra-lesional keloid fibroblasts (IKF). Conditioned media was used to grow NF, NS, PKF and IKF cells over 240 hrs. Cellular behavior was monitored through real time cell analysis (RTCA), proliferation rates and migration in a scratch wound assay. Fibrosis-associated marker expression was determined at both protein and gene level. PKF conditioned media treatment of both NF and NS elicited enhanced cell proliferation, spreading and viability as measured in real time over 240 hrs versus control conditioned media. Following PKF and IKF media treatments up to 240 hrs, both NF and NS showed significantly elevated proliferation rates (p<0.03) and migration in a scratch wound assay (p<0.04). Concomitant up-regulation of collagen I, fibronectin, α-SMA, PAI-1, TGF-β and CTGF (p<0.03) protein expression were also observed. Corresponding qRT-PCR analysis supported these findings (P<0.03). In all cases, conditioned media from growing marginal PKF elicited the strongest effects. In conclusion, primary NF and NS cells treated with PKF or IKF conditioned media exhibit enhanced expression of fibrosis-associated molecular markers and increased cellular activity as a result of keloid fibroblast-derived paracrine factors.

Adventitial nab-rapamycin injection reduces porcine femoral artery luminal stenosis induced by balloon angioplasty via inhibition of medial proliferation and adventitial inflammation

BACKGROUND

Endovascular interventions on peripheral arteries are limited by high rates of restenosis. Our hypothesis was that adventitial injection of rapamycin nanoparticles would be safe and reduce luminal stenosis in a porcine femoral artery balloon angioplasty model.

METHODS AND RESULTS

Eighteen juvenile male crossbred swine were included. Single-injury (40%-60% femoral artery balloon overstretch injury; n=2) and double-injury models (endothelial denudation injury 2 weeks before a 20%-30% overstretch injury; n=2) were compared. The double-injury model produced significantly more luminal stenosis at 28 days, P=0.002, and no difference in medial fibrosis or inflammation. Four pigs were randomized to the double-injury model and adventitial injection of saline (n=2) or 500 μg of nanoparticle albumin-bound rapamycin (nab-rapamycin; n=2) with an endovascular microinfusion catheter. There was 100% procedural success and no difference in endothelial regeneration. At 28 days, nab-rapamycin led to significant reductions in luminal stenosis, 17% (interquartile range, 12%-35%) versus 10% (interquartile range, 8.3%-14%), P=0.001, medial cell proliferation, P<0.001, and fibrosis, P<0.001. There were significantly fewer adventitial leukocytes at 3 days, P<0.001, but no difference at 28 days. Pharmacokinetic analysis (single-injury model) found rapamycin concentrations 1500× higher in perivascular tissues than in blood at 1 hour. Perivascular rapamycin persisted ≥8 days and was not detectable at 28 days.

CONCLUSIONS

Adventitial nab-rapamycin injection was safe and significantly reduced luminal stenosis in a porcine femoral artery balloon angioplasty model. Observed reductions in early adventitial leukocyte infiltration and late medial cell proliferation and fibrosis suggest an immunosuppressive and antiproliferative mechanism. An intraluminal microinfusion catheter for adventitial injection represents an alternative to stent- or balloon-based local drug delivery.

Keloids and hypertrophic scars: update and future directions

Summary:

The development of cutaneous pathological scars, namely, hypertrophic scars (HSs) and keloids, involves complex pathways, and the exact mechanisms by which they are initiated, evolved, and regulated remain to be fully elucidated. The generally held concepts that keloids and HSs represent “aberrant wound healing” or that they are “characterized by hyalinized collagen bundles” have done little to promote their accurate clinicopathological classification or to stimulate research into the specific causes of these scars and effective preventative therapies. To overcome this barrier, we review here the most recent findings regarding the pathology and pathogenesis of keloids and HSs. The aberrations of HSs and keloids in terms of the inflammation, proliferation, and remodeling phases of the wound healing process are described. In particular, the significant roles that the extracellular matrix and the epidermal and dermal layers of skin play in scar pathogenesis are examined. Finally, the current hypotheses of pathological scar etiology that should be tested by basic and clinical investigators are detailed. Therapies that have been found to be effective are described, including several that evolved directly from the aforementioned etiology hypotheses. A better understanding of pathological scar etiology and manifestations will improve the clinical and histopathological classification and treatment of these important lesions.

CCN2 is transiently expressed by keratinocytes during re-epithelialization and regulates keratinocyte migration in vitro by the ras-MEK-ERK signaling pathway

BACKGROUND

CCN2 (previously known as connective tissue growth factor) is a multifunctional matricellular protein that has numerous effects on cell life and cell interactions with the connective tissue. Although the importance of CCN2 for the fibrotic process in wound healing has been well studied, the involvement of CCN2 in keratinocyte function has not yet been explored. Therefore, the aim of the present study was to investigate the role of CCN2 in the epidermis during wound healing.

MATERIALS AND METHODS

Immunohistochemistry was done on sections from full-thickness porcine wounds. The effect of CCN2 on the migration of cultured human keratinocytes exposed to scratch wounds, the effect on phosphorylation of extracellular signal-related kinases (ERK), and the effect of adding inhibitors to the ERK/mitogen-activated protein kinase pathway to human keratinocytes were studied.

RESULTS

The CCN2 protein was transiently expressed in vivo at the leading keratinocyte edge during re-epithelialization of full-thickness porcine wounds. In vitro, exogenous addition of CCN2 to human keratinocyte cultures regulated keratinocyte migration and resulted in phosphorylation of ERK. The addition of inhibitors of ERK/mitogen-activated protein kinase counteracted the effect of CCN2 on migration.

CONCLUSIONS

CCN2 was transiently expressed at the leading keratinocyte edge in vivo. The biologic importance of this was supported in vitro, because CCN2 regulated human keratinocyte migration through activation of the Ras-mitogen-activated protein kinase kinase-ERK signal transduction pathway.

Keloid disease can be inhibited by antagonizing excessive mTOR signaling with a novel dual TORC1/2 inhibitor

Keloid disease (KD) is a fibroproliferative lesion of unknown etiopathogenesis that possibly targets the PI3K/Akt/mTOR pathway. We investigated whether PI3K/Akt/mTOR inhibitor, Palomid 529 (P529), which targets both mammalian target of rapamycin complex 1 (mTORC-1) and mTORC-2 signaling, could exert anti-KD effects in a novel KD organ culture assay and in keloid fibroblasts (KF). Treatment of KF with P529 significantly (P < 0.05) inhibited cell spreading, attachment, proliferation, migration, and invasive properties at a low concentration (5 ng/mL) and induced substantial KF apoptosis when compared with normal dermal fibroblasts. P529 also inhibited hypoxia-inducible factor-1α expression and completely suppressed Akt, GSK3β, mTOR, eukaryotic initiation factor 4E-binding protein 1, and S6 phosphorylation. P529 significantly (P < 0.05) inhibited proliferating cell nuclear antigen and cyclin D and caused considerable apoptosis. Compared with rapamycin and wortmannin, P529 also significantly (P < 0.05) reduced keloid-associated phenotypic markers in KF. P529 caused tissue shrinkage, growth arrest, and apoptosis in keloid organ cultures and substantially inhibited angiogenesis. pS6, pAkt-Ser473, and mTOR phosphorylation were also suppressed in situ. P529 reduced cellularity and expression of collagen, fibronectin, and α-smooth muscle actin (substantially more than rapamycin). These pre-clinical in vitro and ex vivo observations are evidence that the mTOR pathway is a promising target for future KD therapy and that the dual PI3K/Akt/mTOR inhibitor P529 deserves systematic exploration as a candidate agent for the future treatment of KD.

Transcriptional inhibition of hypertrophic scars by a gene silencer, pyrrole-imidazole polyamide, targeting the TGF-β1 promoter

Synthetic pyrrole-imidazole (PI) polyamides bind to the minor groove of double-helical DNA with high affinity and specificity, and inhibit the transcription of corresponding genes. We examined the effects of a transforming growth factor (TGF)-β1-targeted PI polyamide (Polyamide) on hypertrophic skin scars in rats. Hypertrophic scars were created dorsally in rats by incisions. FITC-labeled Polyamide was injected to investigate its distribution in the skin. Expression of TGF-β1, connective tissue growth factor (CTGF), collagen type1, and fibronectin mRNAs was evaluated by reverse transcription PCR analysis. The extent of fibrosis and the expression of TGF-β1 were evaluated histologically and immunohistochemically. Polyamide was distributed in almost all nuclei of skin cells. Expression of TGF-β1 mRNA reached a peak at 3 days after skin incision. Expression of CTGF and extracellular matrix mRNAs was increased continuously even after the peak induction of TGF-β1 mRNA. Injection of Polyamide completely inhibited both the development of scars and the induction of growth factors and extracellular matrix mRNAs. The treatment also markedly inhibited fibrotic changes and reduced the numbers of vimentin-positive spindle-shaped fibroblasts. Injection of Polyamide also reduced established hypertrophic scars in rats. Thus, TGF-β1-targeted PI polyamide should be a feasible gene silencer for hypertrophic scars and keloids.

Expression and functional analysis of endoglin in isolated liver cells and its involvement in fibrogenic Smad signalling

Endoglin is an accessory component of the TGF-β-binding receptor complex that differentially modulates TGF-β and BMP responses. The existence of two splice variants L- and S-endoglin which differ in their cytoplasmic domain has already been shown in human and mice. Endoglin is located on the cell surfaces of cultured hepatic stellate cells and transdifferentiated myofibroblasts suggesting that this receptor might be associated with the profibrogenic attributes of these liver cell subpopulations. We now show that endoglin expression is increased in transdifferentiating hepatic stellate cells and in two models of liver fibrosis (i.e. bile duct ligation and carbon tetrachloride model) and further detectable in cultured portal fibroblasts representing another important fibrogenic cell type but not in hepatocytes. In respect to TGF-β1-signalling, we demonstrate that endoglin interacts with and is phosphorylated by TβRII. In hepatic stellate cells, TGF-β1 upregulates endoglin expression most likely via the ALK5 pathway and requires the SP1 transcription factor. We further identified a novel rat splice variant that is structurally and functionally different from that identified in human and mouse. Transient overexpression of endoglin resulted in a strong increase of TGF-β1-driven Smad1/5 phosphorylation and α-smooth muscle actin expression in a hepatic stellate cell line. In supernatants of respective cultures, we could detect the ectodomain of endoglin suggesting that shedding is a further key process involved in the regulation of this surface receptor.

Pathophysiology and management of the burn scar

Fibroproliferative disorders (FPDs) are common and serious disorders. Hypertrophic scar (HSc) and keloids represent the dermal equivalents of FPD and impose lower mortality but great morbidity. This article reviews current knowledge in the pathophysiology and molecular and cellular characteristics of postburn HSc. Additionally, current treatment modalities and future treatment options based on advancements in the understanding of the pathophysiology of HSc are discussed.

Molecular dissection of abnormal wound healing processes resulting in keloid disease

Keloids are locally aggressive scars that typically invade into healthy surrounding skin and cause both physical and psychosocial distress to the patient. These pathological scars occur following minimal skin trauma after a variety of causes including burns and trauma. Although the pathogenesis of keloid disease is not well understood, it is considered to be the end product of an abnormal healing process. The aim of this review was to investigate the molecular and cellular pathobiology of keloid disease in relation to the normal wound healing process. The molecular aberrances in keloids that correlate with the molecular mechanisms in normal wound healing can be categorized into three groups: (1) extracellular matrix proteins and their degradation, (2) cytokines and growth factors, and (3) apoptotic pathways. With respect to cellular involvements, fibroblasts are the most well-studied cell population. However, it is unclear whether the fibroblast is the causative cell; they are modulated by other cell populations in wound repair, such as keratinocytes and macrophages. This review presents a detailed account of individual phases of the healing process and how they may potentially be implicated in aberrant raised scar formation, which may help in clarifying the mechanisms involved in keloid disease pathogenesis.

Transforming growth factor-beta and angiotensin in fibrosis and burn injuries

This review considers the roles of transforming growth factor-beta (TGF-beta), the signaling Smad proteins, and angiotensin II (AT II) in conditions leading to human fibrosis. The goal is to update the burn practitioner and researcher about this important pathway and to introduce AT II as a possible synergistic signal to TGF-beta in burn scarring. Literature searches of the MEDLINE database were performed for English manuscripts combinations of TGF-beta, Smad, angiotensin, fibrosis, burn, and scar. AT II and TGF-beta both activate the Smad protein system, which leads to the expression of genes related to fibrosis. In fibrotic conditions, such as tubulointerstitial nephritis, systemic sclerosis, and myocardial infarctions, AT II acts both independently and synergistically with TGF-beta. Both AT II and TGF-beta act through a messenger system, the Smad proteins that lead to excessive extracellular matrix formation. Treatment and research implications are reviewed. The interaction between AT II and TGF-beta leading to fibrosis is well described in some human diseases. This pathway may be of importance in human burn scarring as well.