Role In Hypertrophic Scar Formation Research Articles

CILP2 promotes hypertrophic scar through Snail acetylation by interaction with ACLY

Background & aimsHypertrophic scar (HS) is a skin fibroproliferative disorder occurring after burns, surgeries or traumatic injuries, and it has caused a tremendous economic and medical burden. Its molecular mechanism is associated with the abnormal proliferation and transition of fibroblasts and excessive deposition of extracellular matrix. Cartilage intermediate layer protein 2 (CILP2), highly homologous to cartilage intermediate layer protein 1 (CILP1), is mainly secreted predominantly from chondrocytes in the middle/deeper layers of articular cartilage. Recent reports indicate that CILP2 is involved in the development of fibrotic diseases. We investigated the role of CILP2 in the progression of HS. Methods and resultsIt was found in this study that CILP2 expression was significantly higher in HS than in normal skin, especially in myofibroblasts. In a clinical cohort, we discovered that CILP2 was more abundant in the serum of patients with HS, especially in the early stage of HS. In vitro studies indicated that knockdown of CILP2 suppressed proliferation, migration, myofibroblast activation and collagen synthesis of hypertrophic scar fibroblasts (HSFs). Further, we revealed that CILP2 interacts with ATP citrate lyase (ACLY), in which CILP2 stabilizes the expression of ACLY by reducing the ubiquitination of ACLY, therefore prompting Snail acetylation and avoiding reduced expression of Snail. In vivo studies indicated that knockdown of CILP2 or ACLY inhibitor, SB-204990, significantly alleviated HS formation. ConclusionCILP2 exerts a vital role in hypertrophic scar formation and might be a detectable biomarker reflecting the progression of hypertrophic scar and a therapeutic target for hypertrophic scar.

Angiogenesis modulation-mediated inhibitory effects of tacrolimus on hypertrophic scar formation.

Hypertrophic scar (HS) is a fibroproliferative disorder that causes cosmetic as well as functional problems; however, to our knowledge, there is no satisfactory treatment for HS to date. Previous studies have indicated that angiogenesis plays a crucial role in HS formation; therefore, anti-angiogenetic therapies are considered effective in improving HS. Although tacrolimus (TAC) has been proven effective in preventing HS formation in vivo and in vitro, its underlying mechanism remains controversial and ambiguous. Because of its anti-angiogenic effects in other diseases, we aimed to determine whether TAC reduces HS by suppressing angiogenesis. Using a rabbit ear HS model that we developed, HS was treated once a week with normal saline, dimethyl sulfoxide, or TAC for 3weeks. Histological evaluation indicated that TAC significantly reduced collagen deposition and microvessel density in scar tissues. Moreover, immunofluorescence staining for CD31 and vascular endothelial growth factor (VEGF)-A revealed that TAC significantly inhibited HS angiogenesis. In vitro analysis showed that TAC inhibited endothelial cell migration and tubulogenesis as well as the viability and proliferation of human umbilical vascular endothelial cells (HUVECs) and HS fibroblasts (HSFBs). Furthermore, TAC significantly downregulated the expression of the human angiogenetic factors VEGF-A, FGF-2, PDGF-β, and TGF-β1 in HUVECs and HSFBs. Additionally, TAC-mediated inhibition of angiogenesis decreased the gene expression of crucial fibrotic markers, including α- smooth muscle actin and collagens 1 and 3, in HSFBs. This is the first study to demonstrate the inhibitory effects of TAC on HS formation mediated by a mechanism involving the suppression of scar angiogenesis.

Ivermectin inhibits cell proliferation and the expression levels of typeI collagen, α‑SMA and CCN2 in hypertrophic scar fibroblasts.

A hypertrophic scar(HPS) is characterized by abnormal cell proliferation and the overproduction of extracellular matrix. Currently, the treatment options available for this remain unsatisfactory. Innovative treatments are required to attenuate or prevent hypertrophic scarring and the present study searched for a drug capable of becoming a new preventative and therapeutic strategy. Although the underlying mechanisms have not been fully clarified; it is widely accepted that the TGF‑β1/SMAD3 signaling pathway serves an essential role in HPS formation. In the present study, a compound library consisting of clinically used drugs was screened for their inhibitory activity against the SMAD3 protein. The results indicated that ivermectin was able to suppress the phosphorylation of SMAD3. Therefore, the present study further investigated whether ivermectin exhibited antifibrotic effects on HPS fibroblasts. The results demonstrated that ivermectin inhibited the proliferation of HPS fibroblasts and significantly decreased the production of typeI collagen, α‑smooth muscle actin and cellular communication network factor 2, as determined by analyzing the mRNA and protein expression levels. In conclusion, the results of the present study suggested that ivermectin may be a promising therapeutic agent for HPS.

Investigating the potential of LSKL peptide as a novel hypertrophic scar treatment

Hypertrophic scar (HTS) is a common pathologic dermal fibroproliferative disease after skin injury. Transforming growth factor β (TGF-β) plays a central role in HTS formation and development. Thrombospondin-1 (TSP-1) activates latent TGF-β by binding to latency-associated peptide-β on TGF-β structure. So far, LSKL peptide was shown to selectively antagonize TSP-1. In this study, TSP-1 was first confirmed to be highly expressed in HTS. LSKL peptide was proven to inhibit the overexpression of extracellular matrix and contractile ability of HTS fibroblasts. In vivo, LSKL could attenuate the thickness of HTS, distortion of collagen alignment and fibrogenesis. Results also demonstrated that LSKL peptide not only remarkably attenuated cell proliferation and migration, but also induced cell apoptosis of HTS fibroblasts. Western blot analysis further revealed that LSKL peptide significantly suppressed the phosphorylation of PI3K, AKT, and mTOR, while not affecting the phosphorylation of Smad2/3 and MEK/ERK. These findings suggested that LSKL might be a promising anti-fibrosis agent to HTS through PI3K/AKT/mTOR signaling pathway.

Epidermal HMGB1 Activates Dermal Fibroblasts and Causes Hypertrophic Scar Formation in Reduced Hydration.

HMGB1 protein is a multifunctional cytokine involved in inflammatory reactions and is known to play a key role in tissue repair and fibrosis. However, the function of HMGB1 in fibrotic skin diseases, such as hypertrophic scar formation, remains unclear. In this study, HMGB1 was detected in the nuclei of epidermal cells in normal skin and had accumulated in the cytoplasm in hypertrophic scars. By establishing a keratinocyte-fibroblast co-culture and conditional medium treatment models, we found that a reduced hydration condition increased the expression and secretion of HMGB1 in keratinocytes, subsequently activating dermal fibroblasts. HMGB1 secreted from keratinocytes activated fibroblasts by promoting the nuclear import of MRTF-A, increased the nuclear accumulation of MRTF-A/SRF complexes and consequently enhanced α-smooth muscle actin promoter activation. Moreover, blockade of advanced glycation end products or Toll-like receptor 2/4 inhibited the fibroblast activation induced by HMGB1. Finally, local delivery of HMGB1 resulted in marked hypertrophic scar formation in rabbit hypertrophic scar models, while HMGB1 blockade exerted a clear anti-scarring effect. Our results indicate that high HMGB1 levels induced by a reduced hydration status play an important role in hypertrophic scar formation, strongly suggesting that HMGB1 is a novel target for preventing scarring.

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.

Study on the role of Hsa-miR-31-5p in hypertrophic scar formation and the mechanism

Hypertrophic scar (HS) formation is associated with the fibrosis of fibrocytes caused by excessive extracellular matrix (ECM) synthesis and deposition, the initial event of HS formation. Our high throughput screen of miRNA expression profiles identified hsa-miR31-5p, whose transcription level was most differentially in normal skin fibroblasts (NS) and HS among other miRNAs. The level of hsa-miR31-5p in HS was significantly higher than in NS. In-vitro functional experiments showed hsa-miR31-5p knockdown remarkably suppressed the proliferation of hypertrophic scar fibroblasts (HSFBs) under hypoxia, promoted cell invasion, and inhibited the expression of Collagen I and III and Fibronectin (FN), suggesting that hsa-miR31-5p knockdown effectively reduces HS formation caused by excessive ECM synthesis and deposition in HSFBs under hypoxia. Mechanism study showed that the regulation of HS formation by hsa-miR31-5p was mediated by its target gene, factor-inhibiting HIF-1 (FIH): under hypoxia, hsa-miR31-5p down-regulated FIH and thus increased the level of hypoxia inducible factor-1α (HIF-1α), which subsequently activated the HIF-1α fibrosis regulation pathway in HSFBs, and stimulated the proliferation and ECM synthesis in HSFBs, eventually resulting in fibrosis and scar formation. The data also show that knockdown of hsa-miR31-5p in HSFBs impaired the trend of increased proliferation, reduced invasion and excessive ECM synthesis and deposition caused by HIF-1a activation under hypoxia through upregulating FIH, indicating that knockdown of hsa-miR31-5p effectively inhibits the formation of HS. In conclusion, hsa-miR31 -5p plays an important role in HS formation by inhibiting FIH and regulating the HIF-1α pathway. Therefore, hsa-miR31 -5p may be a novel therapeutic target for HS.

Inhibition of FKBP10 Attenuates Hypertrophic Scarring through Suppressing Fibroblast Activity and Extracellular Matrix Deposition

Hypertrophic scar is a pathogenic form of scar formation with no recognized treatment to date. Its molecular mechanism is related to the abnormal proliferation and transition of fibroblasts and overproduction of extracellular matrix. FKBP10 is a molecular chaperone able to regulate α-smooth muscle actin expression and pro-collagen maturation in fibroblasts. However, to our knowledge, no research has investigated the biological function of FKBP10 in scar formation to date. In this study, we aim to assess the expression and function of FKBP10 in hypertrophic scarring. Through microarray analysis, real-time reverse transcriptase-PCR and immunohistochemistry, we discovered that FKBP10 is up-regulated in human and mouse hypertrophic scars. Then we evaluated hypertrophic scar formation in mouse models treated with FKBP10 small interfering RNA and found that knockdown of FKBP10 could attenuate hypertrophic scar formation invivo. To further explore the underlying mechanism, FKBP10 was knocked down in human hypertrophic scar fibroblasts. The invitro results showed that FKBP10 siRNA could inhibit fibroblast activity, reduce the expression of α-smooth muscle actin and extracellular matrix components, and attenuate transforming growth factor-β1 expression and the activation of the Smad signaling pathway. In conclusion, FKBP10 plays a crucial role in hypertrophic scar formation and might be a therapeutic target for hypertrophic scars.

Inflammation and cutaneous nervous system involvement in hypertrophic scarring.

This study aimed to use a mouse model of hypertrophic scarring by mechanical loading on the dorsum of mice to determine whether the nervous system of the skin and inflammation participates in hypertrophic scarring. Results of hematoxylin-eosin and immunohistochemical staining demonstrated that inflammation contributed to the formation of a hypertrophic scar and increased the nerve density in scar tissue.Western blot assay verified that interleukin-13 expression was increased in scar tissue. These findings suggest that inflammation and the cutaneous nervous system play a role in hypertrophic scar formation.

Dracorhodin perchlorate induces apoptosis in primary fibroblasts from human skin hypertrophic scars via participation of caspase-3

Hypertrophic scar (HS) is an abnormally proliferative disorder characterized by excessive proliferation of fibroblasts and redundant deposition of extracellular matrix. An unbalance between fibroblast proliferation and apoptosis has been assumed to play an important role in HS formation. To explore the regulative effects of dracorhodin perchlorate (Dp), one of the derivants of dracorhodin that is a major constituent in the traditional Chinese medicine, on primary fibroblasts from human skin hypertrophic scars, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometric analysis were respectively used to evaluate the inhibitory effect of Dp on the cells and to determine cell cycle distribution. Additionally, cellular apoptosis was separately detected with Hoechst 33258 staining and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay. The expression levels of caspase-3 mRNA and protein were respectively measured with reverse transcription-polymerase chain reaction and western blot analysis, and caspase-3 activity were determined using a colorimetric assay kit. The results showed that Dp significantly inhibited cell growth, and induced apoptosis in fibroblasts in a dose-and time-dependent manner, arresting cell cycle at G1 phase. Additionally, Dp slightly up-regulated caspase-3 mRNA expression in fibroblasts, but significantly down-regulated caspase-3 protein expression in a dose- and time-dependent manner, and concurrently elevated caspase-3 activity. Taken together, these data indicated that Dp could effectively inhibit cell proliferation, and induced cell cycle arrest and apoptosis in fibroblasts, at least partially via modulation of caspase-3 expression and its activity, which suggests that Dp is an effective and potential candidate to develop for HS treatment.

Mechanical tension promotes skin nerve regeneration by upregulating nerve growth factor expression.

This study aimed to explore the role of mechanical tension in hypertrophic scars and the change in nerve density using hematoxylin-eosin staining and S100 immunohistochemistry, and to observe the expression of nerve growth factor by western blot analysis. The results demonstrated that mechanical tension contributed to the formation of a hyperplastic scar in the back skin of rats, in conjunction with increases in both nerve density and nerve growth factor expression in the scar tissue. These experimental findings indicate that the cutaneous nervous system plays a role in hypertrophic scar formation caused by mechanical tension.

Influence of lipopolysaccharide on collagen metabolism of normal skin fibroblasts of human

Objective To observe the influence of lipopolysaccharide (LPS) on collagen metabolism of normal human skin fibroblasts and its biological role in the formation of hypertrophic scar.Methods Fibroblasts were isolated and cultured in vitro,and then exposed to different doses of LPS (0.005,0.01,0.05,0.1,0.5,1.0 μg/ml) from E.coli.055:B5 respectively.The expression of proccllagen type Ⅰ,Ⅲand collagenase mRNAs was tested by RT -PCR.Fibroblasts from hypertrophic scar tissue obtained from the same patients in the same culture passage were used as control.Results Compared with control group,the expression of procollagen type Ⅰ,Ⅲ mRNAs in normal skin fibroblasts increased (0.323 ± 0.041,0.303 ± 0.063,0.391 ± 0.071,0.344 ± 0.086,0.488 ± 0.059,0.401 ± 0.087,0.616 ± 0.107,0.434 ±0.084,0.823 ±0.092,0.542 ± 0.082),while the expression of collagenase mRNAs of normal skin fibroblasts depressed(0.598 ± 0.068,0.556 ± 0.049,0.441 ± 0.043,0.372 ± 0.083,0.260 ± 0.027 ).When LPS was set to the concentration of 0.005 μg/ml,it showed a concentration dependent manner.However,when the concentration of LPS was set to 0.5 μg/ml,the expression of procollagen type Ⅰ,Ⅲ and collagenase mRNAs of normal skin fibroblasts began to decrease (0.451 ± 0.063,0.374 ± 0.072,0.360 ± 0.062).When the concentration of LPS was set to 1.0 μg/ml,the expression of procollagen type Ⅰ,Ⅲ mRNAs (0.162 ± 0.025,0.171 ± 0.061 )were inhibited and the expression of collagenase mRNAs began to increase (0.444 ±0.114).When the concentration of LPS was set to 0.1 μg/ml,the expression of procollagen type Ⅰ,Ⅲ and collagenase mRNAs of normal skin fibroblasts(0.823 ±0.092,0.542 ±0.082,0.260 ±0.027)was similar to that of hypertrophic scar tissue fibroblasts(0.829 ±0.049,0.569 ±0.038,0.277 ±0.059).Conclusions This result supported that LPS may be an important factor in collagen metabolism of normal skin fibroblasts and it plays an important role in hypertrophic scar formation. Key words: Lipopolysaccharides/PD ; Collagen/ME ; Skin/CY/DE; Fibroblasts/ME/DE

Smad ubiquitination regulatory factor 2 expression is enhanced in hypertrophic scar fibroblasts from burned children

Transforming growth factor-β1 (TGF-β1) plays a key role in hypertrophic scar formation. A lot of studies have shown that TGF-β1 stimulates fibroblast proliferation, collagen production, and α-smooth muscle actin (α-SMA) expression, inhibits matrix degradation and eventually leads to scar formation. Smad proteins are important intracellular mediators of TGF-β1 signaling, and Smad ubiquitination regulatory factor 2 (Smurf2), an ubiquitin ligase for Smads, plays critical roles in the regulation of TGF-β1/Smad signaling. It was reported that Smurf2 was abnormally expressed during the process of liver fibrosis and lung fibrosis. Hypertrophic scarring is a fibroproliferative disorder of the dermis that occurs following wounding. However, little is known about the expression of Smurf2 in hypertrophic scarring. We hypothesized that TGF-β1 signaling cannot be disrupted after wound epithelialization probably due to abnormal expression of Smurf2 in hypertrophic scar fibroblasts. In the present study, we found that hypertrophic scar fibroblasts exhibited increased Smurf2 protein and mRNA levels compared with normal fibroblasts, and the expression of Smurf2 gradually increased in hypertrophic scar fibroblasts after TGF-β1 stimulation. Furthermore, we transfected Smurf2 siRNA into hypertrophic scar fibroblasts, and we found that silencing the expression of Smurf2 in hypertrophic scar fibroblasts dramatically reduced TGF-β1 production, inhibited TGF-β1-induced α-SMA expression and inhibited TGF-β1-induced collagen I synthesis. Our results suggest that the enhanced expression of Smurf2 is involved in the progression of hypertrophic scarring.

Imbalance between activin A and follistatin drives postburn hypertrophic scar formation in human skin

Hypertrophic scarring is a skin disorder characterized by persistent inflammation and fibrosis that may occur after wounding or thermal injury. Altered production of cytokines and growth factors, such as TGF-beta, play an important role in this process. Activin A, a member of the TGF-beta family, shares the same intra-cellular Smad signalling pathway with TGF-beta, but binds to its own specific transmembrane receptors and to follistatin, a secreted protein that inhibits activin by sequestration. Recent studies provide evidences of a novel role of activin A in inflammatory and repair processes. The aim of this study was to evaluate the importance of activin A and follistatin expression in the different phases of scar evolution. Immunostaining of sections obtained from active phase hypertrophic scars (AHS) revealed the presence of a high number of alpha-SMA(+) myofibroblasts and DC-SIGN(+) dendritic cells coexpressing activin A. Ex-vivo AHS fibroblasts produced more activin and less follistatin than normal skin or remission phase hypertrophic scar (HS) fibroblasts, both in basal conditions and upon TGF-betas stimulation. We demonstrate that fibroblasts do express activin receptors, and that this expression is not affected by TGF-betas. Treatment of HS fibroblasts with activin A induced Akt phosphorylation, promoted cell proliferation, and enhanced alpha-SMA and type I collagen expression. Follistatin reduced proliferation and suppressed activin-induced collagen expression. These results indicate that the activin/follistatin interplay has a role in HS formation and evolution. The impact of these observations on the understanding of wound healing and on the identification of new therapeutic targets is discussed.

The Temporal Effects of Anti-TGF-β1, 2, and 3 Monoclonal Antibody on Wound Healing and Hypertrophic Scar Formation

A number of studies have implicated transforming growth factor (TGF)-beta1, 2, and 3 (TGF-beta) in wound healing and hypertrophic scarring. We propose that TGF-beta has a temporal effect on these processes. To test this hypothesis, we applied anti-TGF beta1, 2, and 3 monoclonal antibody topically to our dermal ulcer model in the rabbit ear. Rabbit ear wounds were treated intradermally with anti-TGF-beta1, 2, and 3 antibody at early, middle, and late time points. Treated and untreated control wounds were harvested at various time points and examined histologically to quantify wound healing and scar hypertrophy. Real-time polymerase chain reaction was performed to determine TGF-beta mRNA expression in the treated and control wounds. The early treatment group demonstrated decreased new epithelium and granulation tissue (p < 0.05 versus controls). Scars harvested on days 28 and 40 displayed no difference in scar hypertrophy. Both the middle and late treatment groups demonstrated a significant decrease in scar hypertrophy (p < 0.05). Treated wounds from the early treatment group displayed delayed wound healing, with no reduction in scar hypertrophy. Later treatment of wounds with the same antibody, beginning 7 days after wounding, resulted in a reduction in scar hypertrophy. These results support our hypothesis and clearly demonstrate that TGF-beta1, 2, and 3 have differential temporal effects during the wound-healing process, and are important for optimal wound healing in the first week after wounding; beyond 1 week, TGF-beta1, 2, and 3 play a critical role in hypertrophic scar formation.

Myofibroblasts in Hypertrophic Scars, Where do they come from?

Wound healing is accompanied by the appearance of myofibroblasts (myoFB) in the wound. In skin wound healing these cells can be derived from dermal fibroblasts (dFB) by the action of TGF‐β, released from platelets and inflammatory cells entering the wound in the first phase of wound healing. MyoFB show an increased expression of components of the extracellular matrix such as collagen type I and III. In partial thickness wounds the myoFB disappear after the wound is closed probably by apoptosis. In full thickness wounds however the myoFB remain present and the healing of these wounds is accompanied by the formation of hypertrophic scars. Processes such as excessive collagen depositions, altered collagen remodeling and contraction play a key role in hypertrophic scar formation. We hypothesise that the presence of a specific myoFB subtype, which is less susceptible for apoptotic triggers, is responsible for sustained duration of these processes. In full‐thickness wounds the fibroblasts (FB) that populate the wound area are not only recruited from the surrounding dermis but also from other tissues such as the subcutaneous fat. To test the possible involvement of subcutaneous fat fibroblasts (fFB) in scar formation we studied the expression levels of proteins which are thought to play a role in hypertrophic scar formation in these cells. The expression levels of these proteins were compared with the expression levels in dFB and scar derived fibroblasts (sFB). Cultured fFB do show increased expression of α‐SMA, collagen types I and III, and TIMPs and decreased expression of MMPs in comparison with cultured dFB. Furthermore the cells show a collagen cross‐linking profile comparable with bone collagen resulting in collagen fibers which are less accessible for proteases. This kind of cross‐linking is also seen in hypertrophic scars. Taken together the differences in expression profile will lead to excessive collagen deposition. The expression pattern of fFB resembles that of sFB. This suggests that indeed the myoFB from the subcutaneous fat may play a role in hypertrophic scar formation.