Novel methods for the investigation of human hypertrophic scarring and other dermal fibrosis

Characterization and Physiological Differences of Two Primary Cultures of Human Normal and Hypertrophic Scar Dermal Fibroblasts: A Pilot Study

Background/Objectives: Dermal fibroblasts (DFs) are key participants in skin hypertrophic scarring, and their properties are being studied to identify the molecular and cellular mechanisms underlying the pathogenesis of skin scarring. Methods: In the present work, we performed a comparative analysis of DFs isolated from normal skin (normal dermal fibroblasts, NDFs), and hypertrophic scar skin (hypertrophic scar fibroblasts, HTSFs). The fibroblasts were karyotyped and phenotyped, and experiments on growth rate, wound healing, and single-cell motility were conducted. Results: Comparative analysis revealed a minor karyotype difference between cells. However, HTSFs are characterized by higher proliferation level and motility compared to NDFs. These significant differences may be associated with quantitative and qualitative differences in the cell secretome. A proteomic comparison of NDF and HTSF found that differences were associated with metabolic proteins reflecting physiological differences between the two cells lines. Numerous unique proteins were found only in the vesicular phase of vHTSFs. Some proteins involved in cell proliferation (protein-glutamine gamma-glutamyltransferase K) and cell motility (catenin delta-1), which regulate gene transcription and the activity of Rho family GTPases and downstream cytoskeletal dynamics, were identified. A number of proteins which potentially play a role in fibrosis and inflammation (mucin-5B, CD97, adhesion G protein-coupled receptor E2, antileukoproteinase, protein S100-A8 and S100-A9, protein caspase recruitment domain-containing protein 14) were detected in vHTSFs. Conclusions: A comparative analysis of primary cell cultures revealed their various properties, especially in the cell secretome. These proteins may be considered promising target molecules for developing treatment or prevention strategies for pathological skin scarring.

Human In Vitro Skin Models for Wound Healing and Wound Healing Disorders

Skin wound healing is essential to health and survival. Consequently, high amounts of research effort have been put into investigating the cellular and molecular components involved in the wound healing process. The use of animal experiments has contributed greatly to the knowledge of wound healing, skin diseases, and the exploration of treatment options. However, in addition to ethical concerns, anatomical and physiological inter-species differences often influence the translatability of animal-based studies. Human in vitro skin models, which include essential cellular and structural components for wound healing analyses, would improve the translatability of results and reduce animal experiments during the preclinical evaluation of novel therapy approaches. In this review, we summarize in vitro approaches, which are used to study wound healing as well as wound healing-pathologies such as chronic wounds, keloids, and hypertrophic scars in a human setting.

A systematic review of the comparison between needling (RF-needling, meso-needling, and micro-needling) and ablative fractional lasers (CO2, erbium YAG) in the treatment of atrophic and hypertrophic scars

The aim of this study is to compare needling (RF-needling, meso-needling, micro-needling) and ablative fractional lasers (CO2, erbium-YAG) in the treatment of atrophic and hypertrophic scars in a systematic review. The database was searched, and 10 articles were selected that were relevant in terms of content, topic, and purpose and met the inclusion criteria. Of all the articles reviewed in this study, there were 2 randomized split-face trials (20%), 1 controlled nonrandomized trial (10%), 1 controlled randomized phase III clinical trial (10%), 1 prospective trial (10%), 1 prospective nonrandomized open-label trial (10%), and 1 randomized comparative trial (10%), with the type of study not reported in 3 articles. We used Endnote X8 to review the articles and extract data. After review, the studies were analyzed and categorized. No statistically significant difference was found between the two methods, laser and micro-needling, in the treatment of atrophic and hypertrophic scars in 60% of the articles studied, and both showed significant improvement (70% or more improvement to complete response). Significant improvement was noted in 20% of the studies reviewed for the laser and micro-needling treatment methods. The results of this study show that needling and ablative fractional lasers are tolerable and safe procedures with no significant difference in the treatment of skin scars in sixty percent of the studies.

Advantages and Disadvantages of Using Small and Large Animals in Burn Research: Proceedings of the 2021 Research Special Interest Group

Multiple animal species and approaches have been used for modeling different aspects of burn care, with some strategies considered more appropriate or translatable than others. On April 15, 2021, the Research Special Interest Group of the American Burn Association held a virtual session as part of the agenda for the annual meeting. The session was set up as a pro/con debate on the use of small versus large animals for application to four important aspects of burn pathophysiology: burn healing/conversion; scarring; inhalation injury; and sepsis. For each of these topics, 2 experienced investigators (one each for small and large animal models) described the advantages and disadvantages of using these preclinical models. The use of swine as a large animal model was a common theme due to anatomic similarities with human skin. The exception to this was a well-defined ovine model of inhalation injury; both of these species have larger airways which allow for incorporation of clinical tools such as bronchoscopes. However, these models are expensive and demanding from labor and resource standpoints. Various strategies have been implemented to make the more inexpensive rodent models appropriate for answering specific questions of interest in burns. Moreover, modelling burn-sepsis in large animals has proven difficult. It was agreed that the use of both small and large animal models have merit for answering basic questions about the responses to burn injury. Expert opinion and the ensuing lively conversations are summarized herein, which we hope will help inform experimental design of future research.

Circular RNA HECTD1 knockdown inhibits transforming growth factor-beta/ small mothers against decapentaplegic (TGF-β/Smad) signaling to reduce hypertrophic scar fibrosis

Scars are nearly impossible to avoid after a skin injury, but despite advancements in the treatment modalities, they remain a clinical problem, especially hypertrophic scars (HS). Many studies include the mechanism of formation and inhibition of HS, but it is not fully understood yet. Circular RNA HECTD1 (circHECTD1), for the first time, has been found to have roles in HS physiology. We determined the relative circHECTD1 levels in HS fibrous cells and tissues by RT-qPCR. Afterward, the effect of circHECTD1 knockdown on the proliferation, migration, invasion, fibrosis, and Transforming Growth Factor-beta/small mothers against decapentaplegic (TGF-β/Smad) signaling was studied using CCK-8, wound healing, Transwell, and western blot assays. After the role of circHECTD1 was clarified, its targeted micro RNA (miR) was predicted using the Starbase database, and we constructed a miR-142-3p mimic to study the details of its regulation mechanism. We used the TargetScan database to predict the downstream target high mobility group box 1 (HMGB1) of miR-142-3p, and the luciferase report assay verified the binding, and then its effect was determined by RT-qPCR. circHECTD1 is highly expressed in HS tissues and human skin hypertrophic scar fibroblasts (HSF); its loss of function inhibits cell proliferation, migration, invasion, fibrosis, and TGF-β/Smad signaling. However, miR-142-3p inhibitor reverses the effect of circHECTD1 on all the above-mentioned aspects, including HMGB1 expression. In conclusion, circHECTD1 knockdown interrupts TGF-β/Smad signaling through miR-142-3p/HMGB1 and suppresses scar fibrosis.

Treatment of hypertrophic scar with injection of triamcinolone leads to increased microRNA-26a in a rabbit ear model

Objectives:

Differential expression of microRNAs (miRNAs) has been confirmed to promote hypertrophic scar (HS) formation. However, this mechanism remains to be further elucidated. This paper investigated the effects of microRNA26a on HS of rabbit ears or its mechanism.

Methods:

The rabbit HS models were established and randomly assigned to either the experimental group (20 rabbits with treatment through triamcinolone acetonide) or the scar group (20 rabbits without treatment). In addition, 10 unmodeled rabbits were served as control group. The expression of microRNA-26a in HS tissues was detected via a stem-loop real-time polymerase chain reaction (RT-PCR).

Results:

According to RT-PCR, we showed the decreased expression of microRNA-26a in the scar group compared with that in the experimental group, and in the experimental group compared with that in the control group ( p < .01). In addition, the expression of microRNA-26a was negatively correlated with scar thickness (STs), number of fibroblasts (NFs), Collagen I (Col I) level, Collagen III (Col III) level, Interleukin-6 (IL-6) level, and Tumor necrosis factor-alpha (TNF-α) level (all p < .01).

Conclusions:

Our findings revealed that the increase of microRNA-26a expression might alleviate excessive inflammation during the HS formation, inhibit fibroblast proliferation and collagen deposition in HS, and promote the treatment of HS.

Hypertrophic Scarring: Current Knowledge of Predisposing Factors, Cellular and Molecular Mechanisms

Hypertrophic scarring (HSc) is an age-old problem that still affects millions of people physically, psychologically, and economically. Despite advances in surgical techniques and wound care, prevention and treatment of HSc remains a challenge. Elucidation of factors involved in the development of this common fibroproliferative disorder is crucial for further progress in preventive and/or therapeutic measures. Our knowledge about pathophysiology of HSc at the cellular and molecular level has grown considerably in recent decades. In this article, current knowledge of predisposing factors and the cellular and molecular mechanisms of HSc has been reviewed.

RETRACTED: Healing potential of Spirulina platensis for skin wounds by modulating bFGF, VEGF, TGF-ß1 and α-SMA genes expression targeting angiogenesis and scar tissue formation in the rat model

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. The journal was alerted to an associated PubPeer post in which suspected duplicated features were identified within Figure 4 B1, and the histological image in Figure 3 A1 appears to have been previously published in another article, as detailed here: https://pubpeer.com/publications/E5658B7B735FF993AA795A5F14C086. The journal performed independent analysis and identified additional suspected image duplications between the images of mice in Figure 1 A+B and images of mice in Figure 6 A+B from Elbialy et al., BMC Veterinary Research (2020). The journal requested the authors provide an explanation to these concerns and associated raw data, but this request was not satisfactorily fulfilled. The Editor-in-Chief assessed the case and decided to retract the article.

IL-10 alleviates lipopolysaccharide-induced skin scarring via IL-10R/STAT3 axis regulating TLR4/NF-κB pathway in dermal fibroblasts

Hypertrophic scar (HS) is a severe fibrotic skin disease. It has always been a major problem in clinical treatment, mainly because its pathogenesis has not been well understood. The roles of bacterial contamination and prolonged wound inflammation were considered significant. IL‐10 is a potent anti‐inflammatory cytokine and plays a pivotal role in wound healing and scar formation. Here, we investigate whether IL‐10 alleviates lipopolysaccharide (LPS)‐induced inflammatory response and skin scarring and explore the possible mechanism of scar formation. Our results showed that the expression of TLR4 and pp65 was higher in HS and HS‐derived fibroblasts (HSFs) than their counterpart normal skin (NS) and NS‐derived fibroblasts (NSFs). LPS could up‐regulate the expression of TLR4, pp65, Col I, Col III and α‐SMA in NSFs, but IL‐10 could down‐regulate their expression in both HSFs and LPS‐induced NSFs. Blocking IL‐10 receptor (IL‐10R) or the phosphorylation of STAT3, their expression was up‐regulated. In addition, in vitro and in vivo models results showed that IL‐10 could alleviate LPS‐induced fibroblast‐populated collagen lattice (FPCL) contraction and scar formation. Therefore, IL‐10 alleviates LPS‐induced skin scarring via IL‐10R/STAT3 axis regulating TLR4/NF‐κB pathway in dermal fibroblasts by reducing ECM proteins deposition and the conversion of fibroblasts to myofibroblasts. Our results indicate that IL‐10 can alleviate the LPS‐induced harmful effect on wound healing, reduce scar contracture, scar formation and skin fibrosis. Therefore, the down‐regulation of inflammation may lead to a suitable scar outcome and be a better option for improving scar quality.

Tanshinone IIA down-regulated p-Smad3 signaling to inhibit TGF-β1-mediated fibroblast proliferation via lncRNA-HSRL/SNX9

INTRODUCTION

Tanshinone IIA (TSIIA), an active component of Salvia miltiorrhiza (Danshen), is reported to inhibit cell proliferation in hypertrophic scars (HS). In our previous study, we observed that lncRNA human-specific regulatory loci (HSRL) was up-regulated in HS tissues. However, whether TSIIA serves as an effective treatment for HS through affecting HSRL is still unexplored.

METHODS

TGF-β1-stimulated fibroblast were used as the in vitro HS model. The effects of TSIIA on cell proliferation were evaluated using CCK-8, Edu staining and colony formation assays. By performing loss-of-function and rescue experiments, we explored the role of HSRL and Sorting nexin 9 (SNX9) in TGF-β1-stimulated fibroblast. Employing RNA-protein pull-down assay and Co-immunoprecipitation, we further investigated the mechanisms through which TSIIA attenuated TGF-β1-stimulated fibroblast.

RESULTS

Our data demonstrated that TSIIA could effectively attenuate TGF-β1-mediated fibroblast proliferation in a dose-dependent manner. Meanwhile, TSIIA could down-regulate the expression of α-SMA, VEGFA, Collagen 1, HSRL, SNX9 and p-Smad2/3 in TGF-β1-stimulated HSF. In addition, we found that SNX9 overexpression reversed the effects of HSRL knockdown on TGF-β1-stimulated HSF. Furthermore, we confirmed that TSIIA treatment weakens the interaction between p-Smad3 and SNX9 in HS models.

CONCLUSIONS

Tanshinone IIA down-regulated p-Smad3 signaling to inhibit TGF-β1-mediated fibroblast proliferation via lncRNA-HSRL/SNX9.

Tetramethylpyrazine Induces Apoptosis and Inhibits Proliferation of Hypertrophic Scar-Derived Fibroblasts via Inhibiting the Phosphorylation of AKT

Hypertrophic scar (HS) is a serious fibrotic skin disease and often considered as a kind of benign skin tumor. Tetramethylpyrazine (TMP), the main chemical composition of the traditional Chinese medicine Chuanxiong Rhizoma, has shown significant clinical benefits in the treatment of fibrosis disease and tumor, while the role in HS and the concrete mechanisms remain elusive. Herein, the protective effects of TMP in the treatment of HS was investigated and the results showed that the protein expression levels of type I collagen (Col I), type III collagen (Col III), and α-smooth muscle actin (α-SMA) were all inhibited remarkably after addition of TMP in HS-derived fibroblasts (HFs). Moreover, TMP also suppressed fibroblast proliferative and induced cell apoptosis. The protein expression levels of Caspase-3 and Bcl-2 were all decreased comparing with the control group while proapoptotic proteins Bax and Cleaved Caspase-3 were increased. In addition, TMP treatment markedly reduced the phosphorylation levels of AKT. Taken together, our investigations demonstrated that TMP could down-regulate the expression of fibrosis-related molecules, inhibit scar fibroblast proliferation and activate cell apoptosis, during which AKT pathway was involved. Thus, this study shed more light on the pharmacological mechanisms of TMP, and provided a novel therapeutic alternative for prevention and treatment of HS.

Inhibition of growth of Asian keloid cells with human umbilical cord Wharton's jelly stem cell-conditioned medium

Background

Keloid formation occurs in Caucasian, African, and Asian populations and is a severe psychosocial burden on patients. There is no permanent treatment for this problem as its pathogenesis is not properly understood. Furthermore, differences in keloid behavior between ethnic groups are not known. It has been hypothesized that keloids behave like benign tumors because of their uncontrolled growth. The present study evaluated the tumoricidal properties of human Wharton’s jelly stem cell-conditioned medium (hWJSC-CM) on fresh Asian keloid cells (AKCs).

Methods

Human Wharton’s jelly stem cells (hWJSCs) and AKCs were isolated based on our previous methods. hWJSCs and human skin fibroblasts (HSF) (controls) were used to collect hWJSC-CM and HSF-conditioned medium (HSF-CM). AKCs were treated with hWJSC-CM and HSF-CM in vitro and in vivo in a human keloid xenograft SCID mouse model. The inhibitory effect of hWJSC-CM on AKCs was tested in vitro using various assays and in vivo for attenuation/abrogation of AKC tumors created in a xenograft mouse model.

Results

qRT-PCR analysis showed that the genes FN1, MMP1, and VCAN were significantly upregulated in AKCs and ANXA1, ASPN, IGFBP7, LGALS1, and PTN downregulated. AKCs exposed to hWJSC-CM in vitro showed significant decreases in cell viability and proliferation, increases in Annexin V-FITC+ cell numbers, interruptions of the cell cycle at Sub-G1 and G2/M phases, altered CD marker expression, downregulated anti-apoptotic-related genes, and upregulated pro-apoptotic and autophagy-related genes compared to controls. When AKCs were administered together with hWJSC-CM into immunodeficient mice there were no keloid tumors formed in 7 mice (n = 10) compared to the untreated control mice. When hWJSC-CM was injected directly into keloid tumors created in mice there were significant reductions in keloid tumor volumes and weights in 30 days.

Conclusions

hWJSC-CM inhibited the growth of AKCs in vitro and in xenograft mice, and it may be a potential novel treatment for keloids in the human. The specific molecule(s) in hWJSC-CM that induce the anti-keloid effect need to be identified, characterized, and tested separately in larger preclinical and clinical studies.

MicroRNA-130a has pro-fibroproliferative potential in hypertrophic scar by targeting CYLD

Hypertrophic scars are dermal fibrosis diseases that protrude from the surface of the skin and irregularly extend to the periphery, seriously affecting the appearance and limb function of the patient. In this study, we found that microRNA-130a (miR-130a) was increased in hypertrophic scar tissues and derived primary fibroblasts, accompanied by up-regulation of collagen1/3 and α-SMA. Inhibition of miR-130a in hypertrophic scars fibroblasts suppressed the expression of collagen1/3 and α-SMA as well as the cell proliferation. Bioinformatics analysis combined with luciferase reporter gene assay results indicated that CYLD was a target gene of miR-130a, and the miR-130a mimic could reduce the level of CYLD. In contrast to miR-130a, the expression of CYLD was downregulated in hypertrophic scars and their derived fibroblasts. Overexpressing CYLD inhibited the expression of collagen 1/3 and α-SMA, slowed cell proliferation, and inhibited Akt activity. As expected, further study showed that the overexpression of CYLD could prevent the pro-fibroproliferative effects of miR-130a. Consistent with the in vitro results, the inhibitor of miR-130a effectively ameliorated excessive collagen deposition in bleomycin-induced skin fibrosis mouse model. Taken together, our results indicate that miR-130a promotes collagen secretion, myofibroblast transformation and cell proliferation by targeting CYLD and enhancing Akt activity. Therefore, the miR-130a/CYLD/Akt pathway may serve as a novel entry point for future skin fibrosis research.

Dihydromyricetin attenuates hypertrophic scar formation by targeting activin receptor-like kinase 5

Hypertrophic scar (HPS) is a manifestation of abnormal tissue repair, representing excessive extracellular matrix production and abnormal function of fibroblasts, for which no satisfactory treatment is available at present. Here we identified a natural product of flavonoid, dihydromyricetin, could effectively attenuate HPS formation. We showed that local intradermal injection of dihydromyricetin (50 μM) reduced the gross scar area, cross-sectional size of the scar and the scar elevation index in a mechanical load-induced mouse model. In addition, dihydromyricetin treatment also markedly decreased collagen density of the scar tissue. Furthermore, both in vitro and in vivo study both demonstrated that dihydromyricetin inhibited the proliferation, activation, contractile and migration abilities of hypertrophic scar-derived fibroblasts (HSFs) but did not affect HSFs apoptosis. Western blot analysis revealed that dihydromyricetin could down-regulate the phosphorylation of Smad2 and Smad3 of TGF-β signaling. Such bioactivity of dihydromyricetin may result from its selective binding to the catalytic region of activin receptor-like kinase 5 (ALK5), as suggested by the molecular docking study and kinase binding assay (12.26 μM). Above all, dihydromyricetin may prove to be a promising agent for the treatment of HPS and other fibroproliferative disorders.

Inactivation of Beclin-1-dependent autophagy promotes ursolic acid-induced apoptosis in hypertrophic scar fibroblasts

A hypertrophic scar (HS) is caused by abnormal proliferation of dermal fibroblasts. Thus, promoting hypertrophic scar fibroblast (HSFB) apoptosis is an effective strategy for HS therapy. Ursolic acid (UA) has been widely used as an inducer of apoptosis in diverse cancers. However, whether UA plays an inhibitory role in HS formation is still unknown. In our study, UA was used to treat HSFBs and the cell viability, apoptosis, and collagen synthesis were determined by a Cell Counting Kit 8 assay, flow cytometry, and an H3 -proline incorporation assay, respectively. Autophagy activity was detected by LC3 immunoblotting and electron microscopy, and siRNAs targeting Beclin-1 were used to inhibit autophagy. Western blotting was performed to investigate the molecular changes in HSFBs after various treatments. We found that UA inhibited collagen synthesis and induced cell apoptosis in HSFBs, evidenced by the deregulated expression of Bim, Bcl-2 and Cyto C. Furthermore, we demonstrated that UA induced autophagy and inactivation of autophagy promoted UA-induced apoptosis and collagen synthesis inhibition in HSFBs. Molecular investigation indicated that UA-induced autophagy through upregulation of Beclin-1 and knockdown of Beclin-1 prevent UA-induced autophagy. Overexpression of Bcl-2 prevents UA-induced autophagy, Beclin-1 upregulation, apoptosis and collagen synthesis inhibition in HSFBs. Collectively, our study demonstrated that UA is a novel agent for inhibiting HS formation by promoting apoptosis, especially in combination with an autophagy inhibitor. Our results provide strong evidence of the application of UA in clinical HS treatment.

Autophagy protein LC3 regulates the fibrosis of hypertrophic scar by controlling Bcl-xL in dermal fibroblasts

Hypertrophic scar (HS) is a serious skin fibrotic disease characterized by excessive hypercellularity and extracellular matrix (ECM) component deposition. Autophagy is a tightly regulated physiological process essential for cellular maintenance, differentiation, development and homeostasis. However, during the formation of HS, whether and how autophagy is regulated in dermal fibroblasts are still far from elucidated. Here we detected the autophagic capacity in HS and normal skin (NS) counterparts, explored and verified the key regulatory molecules of autophagy in HS-derived fibroblasts (HSFs), and validated the data using rabbit ear scar model. Transmission electron microscopy (TEM) and immunostaining data showed that LC3-positive cells and autophagosomes in HS/HSFs were more intensive relative to those in NS/NSFs groups. Knockdown of LC3 (shLC3) could significantly block the expressionof type I collagen (Col 1, p < 0.01) and type III collagen (Col 3, p < 0.01) and thus inhibit the fibrosis of HSFs. shLC3 resistant to autophagy was shown to be Bcl-xL-, not Bcl-2-dependent, and silencing of Bcl-xL (sibcl-xL) significantly increased apoptosis of HSFs (p < 0.01). Immunofluorescence results showed that instead of inhibiting α-SMA protein expression, shLC3 could change its architecture arrangement in HSFs. sibcl-xL showed that Bcl-xL was a key signaling molecule involved in HSFs autophagy. More importantly, both shLC3 and sibcl-xL obviously improved the appearance and architecture of the rabbit ear scar, and reduced scar formation on the rabbit ear. Therefore, the aberration of LC3 protein processing compromised autophagy in HS might associate with its pathogenesis in wound repair. LC3 regulated HS fibrosis by controlling the expression of Bcl-xL in HSFs. Thus, Bcl-xL might serve as a potential molecular target, providing a novel strategy for HS therapy.

Compression therapy affects collagen type balance in hypertrophic scar

BACKGROUND

The effects of pressure on hypertrophic scar are poorly understood. Decreased extracellular matrix deposition is hypothesized to contribute to changes observed after pressure therapy. To examine this further, collagen composition was analyzed in a model of pressure therapy in hypertrophic scar.

MATERIALS AND METHODS

Hypertrophic scars created on red Duroc swine (n = 8) received pressure treatment (pressure device mounting and delivery at 30 mm Hg), sham treatment (device mounting and no delivery), or no treatment for 2 wk. Scars were assessed weekly and biopsied for histology, hydroxyproline quantification, and gene expression analysis. Transcription levels of collagen precursors COL1A2 and COL3A1 were quantified using reverse transcription-polymerase chain reaction. Masson trichrome was used for general collagen quantification, whereas immunofluorescence was used for collagen types I and III specific quantification.

RESULTS

Total collagen quantification using hydroxyproline assay showed a 51.9% decrease after pressure initiation. Masson trichrome staining showed less collagen after 1 (P < 0.03) and 2 wk (P < 0.002) of pressure application compared with sham and untreated scars. Collagen 1A2 and 3A1 transcript decreased by 41.9- and 42.3-fold, respectively, compared with uninjured skin after pressure treatment, whereas a 2.3- and 1.3-fold increase was seen in untreated scars. This decrease was seen in immunofluorescence staining for collagen types I (P < 0.001) and III (P < 0.04) compared with pretreated levels. Pressure-treated scars also had lower levels of collagen I and III after pressure treatment (P < 0.05) compared with sham and untreated scars.

CONCLUSIONS

These results demonstrate the modulation of collagen after pressure therapy and further characterize its role in scar formation and therapy.

Identification of sirtuin 1 as a promising therapeutic target for hypertrophic scars

BACKGROUND AND PURPOSE

Sirtuin1 (SIRT1), the founding member of mammalian class III histone deacetylases, is reported to be a drug target involved in fibrotic diseases. However, whether it is an effective drug target in hypertrophic scar treatment is still not known.

EXPERIMENTAL APPROACH

In the present study, we observed that SIRT1 localized to both the epidermis and the dermis of skin tissues by immunohistochemistry. After knock-down of SIRT1 by shRNA or up-regulating SIRT1 by resveratrol, the expression of α-SMA, Col1 and Col3 in fibroblasts were detected by western blots. A mouse excision wound healing model was used to observe the changes in collagen fibre associated with the different expression levels of SIRT1.

KEY RESULTS

SIRT1 expression was inhibited in hypertrophic scar tissue. The down-regulation of SIRT1 resulted in an increased expression of α-SMA, Col1 and Col3 in hypertrophic scar-derived fibroblasts. In contrast, the up-regulation of SIRT1 not only inhibited the expression of α-SMA, Col1 and Col3 in hypertrophic scar-derived fibroblasts but also blocked the activation of TGFβ1-induced normal skin-derived fibroblasts. In the mouse model of wound healing, the deletion of SIRT1 resulted in denser collagen fibres and a more disordered structure, whereas resveratrol treatment led to a more organized and thinner collagen fibre, which was similar to that observed during normal wound healing.

CONCLUSIONS AND IMPLICATIONS

The results revealed that SIRT1 negatively regulates TGFβ1-induced fibroblast activation and inhibits excessive scar formation and is, therefore, a promising drug target for hypertrophic scar formation.

Where we stand with human hypertrophic and keloid scar models

We have yet to create a human scar model that demonstrates the complex nature of hypertrophic scar and keloid formation as well as ways to prevent them despite emerging advances in our understanding of the immune system, the inflammatory response, and proteomic and genomic changes after injury. Despite more complex in vitro models, we fail to explain the fundamental principles to scar formation, and the timeline of their development. The solution to developing the ideal in vitro scar model is one that mimics the heterogeneous cellular and molecular interactions, as well as the evolving structure and function of human skin.

Loureirin B inhibits fibroblast proliferation and extracellular matrix deposition in hypertrophic scar via TGF-β/Smad pathway

The ethanolic extract of Resina Draconis (RDEE) has been reported beneficial to normal wound healing yielding more regularly arranged collagen fibres. Loureirin B, a major component in RDEE, has been supposed to be effective on the prevention and treatment of pathological scars. To investigate the therapeutic effects of loureirin B on hypertrophic scar (HS), fibroblasts from human HS and normal skin (NS) were isolated. Results showed that loureirin B dose-dependently downregulated both mRNA and protein levels of type I collagen (ColI), type III collagen (ColIII) and α-smooth muscle actin (α-SMA) in HS fibroblasts. Loureirin B also suppressed fibroblast proliferative activity and redistributed cell cycle, but did not affect cell apoptosis. In vivo rabbit ear scar model, loureirin B significantly improved the arrangement and deposition of collagen fibres, decreased protein levels of ColI, ColIII and α-SMA and suppressed myofibroblast differentiation and scar proliferative activity. In NS fibroblasts, loureirin B effectively inhibited TGF-β1-induced upregulation of ColI, ColIII and α-SMA levels, myofibroblast differentiation and the activation of Smad2 and Smad3. Loureirin B also affected mRNA levels of major MMPs and TIMPs in TGF-β1-stimulated fibroblasts. Taken together, this study demonstrates that loureirin B could downregulate the expression of fibrosis-related molecules by regulating MMPs and TIMPs levels, inhibit scar fibroblast proliferation and suppress TGF-β1-induced fibrosis, during which TGF-β1/Smad2/3 pathway is likely involved. These findings suggest that loureirin B is a potential therapeutic compound for HS treatment.