Search

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. [ABSTRACT FROM AUTHOR]

Background: As an important oncogenic miRNA, microRNA-21 (miR-21) is associated with various malignant diseases. However, the precise biological function of miR-21 and its molecular mechanism in hypertrophic scar fibroblast cells has not been fully elucidated. Methodology/Principal Findings: Quantitative Real-Time PCR (qRT-PCR) analysis revealed significant upregulation of miR-21 in hypertrophic scar fibroblast cells compared with that in normal skin fibroblast cells. The effects of miR-21 were then assessed in MTT and apoptosis assays through in vitro transfection with a miR-21 mimic or inhibitor. Next, PTEN (phosphatase and tensin homologue deleted on chromosome ten) was identified as a target gene of miR-21 in hypertrophic scar fibroblast cells. Furthermore, Western-blot and qRT-PCR analyses revealed that miR-21 increased the expression of human telomerase reverse transcriptase (hTERT) via the PTEN/PI3K/AKT pathway. Introduction of PTEN cDNA led to a remarkable depletion of hTERT and PI3K/AKT at the protein level as well as inhibition of miR-21-induced proliferation. In addition, Western-blot and qRT-PCR analyses confirmed that hTERT was the downstream target of PTEN. Finally, miR-21 and PTEN RNA expression levels in hypertrophic scar tissue samples were examined. Immunohistochemistry assays revealed an inverse correlation between PTEN and hTERT levels in high miR-21 RNA expressing-hypertrophic scar tissues. Conclusions/Significance: These data indicate that miR-21 regulates hTERT expression via the PTEN/PI3K/AKT signaling pathway by directly targeting PTEN, therefore controlling hypertrophic scar fibroblast cell growth. MiR-21 may be a potential novel molecular target for the treatment of hypertrophic scarring. [ABSTRACT FROM AUTHOR]

Autophagy is a tightly regulated physiological process essential for cellular maintenance, differentiation, development, and homeostasis. Aberration of this process associates with the pathogeneses of several diseases in mammals. Hypertrophic scar (HS) is characterized by an abundance of collagenous tissue with hypercellularity. However, the molecular mechanism in HS formation is poorly understood. We compared the autophagic capacity in HS and its normal skin (NS) counterparts and explored the molecular mechanism of autophagy during the formation of HS. Microtubule-associated protein 1 light chain 3 (LC3) proteins in HS and NS were detected by immunohistochemistry, Western blot and quantitative real-time PCR (qPCR). The data showed that LC3 positive staining in HS was less intensive relative to NS group ( p < 0.05). Three forms of LC3, with molecular weights of about 19 kDa (proLC3), 18 kDa (LC3-I) and 16 kDa (LC3-II), respectively, expressed in NS by Western blot. In contrast, only proLC3 expressed while both LC3-I and LC3-II were significantly downregulated in HS. The protein level of beclin 1 in HS was significantly lower compared with NS ( p < 0.05). LC3 and beclin 1 mRNA levels in HS were significantly lower than that in NS ( p < 0.05). These results suggest that the generation of LC3-I and LC3-II are interrupted in HS, and that the resultant decrease of autophagic capacity may associate with the pathogenesis of HS. [ABSTRACT FROM AUTHOR]

Keloids and hypertrophic scars are significant symptomatic clinical problems characterized by the excessive and abnormal deposition of collagen-based extracellular matrix (ECM) components. However, the molecular basis of keloid and hypertrophic scar formation has not been fully elucidated. Here, we demonstrated that down-regulation of the transcription factor Smad interacting protein 1 (SIP1) could be relevant to keloid and hypertrophic scar formation. The results of the present study show that the level of SIP1 mRNA is significantly decreased in pathological scar tissues and in normal skin and pathological scar fibroblasts treated with transforming growth factor β1 (TGF-β1). In contrast, the expression of SIP1 mRNA is not decreased in normotrophic scar samples. The SIP1 mRNA level inversely correlates with the mRNA level of type I collagen (COL1A2) and directly correlates with the mRNA level of matrix metalloproteinase-1 (MMP1). Overexpression of SIP1 in keloid and hypertrophic scar fibroblasts represses TGF-β1-stimulated COL1A2 expression and induces MMP1 expression. Alternatively, knockdown of SIP1 in normal skin fibroblasts enhance TGF-β1-induced COL1A2 levels. These findings suggest that SIP1 could be a regulator of skin fibrosis, and depletion of SIP1 in pathological scar tissues could result in an up-regulation of collagen and down-regulation of matrix metalloproteinase, leading to an abnormal accumulation of ECM along with fibrosis and pathological scar formation. [Copyright &y& Elsevier]