Shirong Li

Investigating the role of P311 in the hypertrophic scar.

The mechanisms of hypertrophic scar formation are not fully understood. We previously screened the differentially expressed genes of human hypertrophic scar tissue and identified P311 gene as upregulated. As the activities of P311 in human fibroblast function are unknown, we examined the distribution of it and the effects of forced expression or silencing of expression of P311. P311 expression was detected in fibroblast-like cells from the hypertrophic scar of burn injury patients but not in peripheral blood mononuclear cells, bone marrow mesenchymal stem cells, epidermal cells or normal skin dermal cells. Transfection of fibroblasts with P311 gene stimulated the expression of alpha-smooth muscle actin (α-SMA), TGF-β1 and α1(I) collagen (COL1A1), and enhanced the contraction of fibroblast populated collagen lattices (FPCL). In contrast, interference of fibroblast P311 gene expression decreased the TGF-β1 mRNA expression and reduced the contraction of fibroblasts in FPCL. These results suggest that P311 may be involved in the pathogenesis of hypertrophic scar via induction of a myofibroblastic phenotype and of functions such as TGF-β1 expression. P311 could be a novel target for the control of hypertrophic scar development.

Genistein inhibits proliferation and functions of hypertrophic scar fibroblasts.

Hypertrophic scarring is abnormal proliferation of dermal fibroblasts and excessive deposition of extracellular matrix. To date, despite many studies, treatments have not been satisfactory. Genistein, a potent, specific inhibitor of tyrosine protein kinases (TPKs), has been proved to inhibit many kinds of tumour and some fibrotic diseases. The purpose of this study was to investigate the effects of genistein on the proliferation and functions of hypertrophic scar fibroblasts (HSFBs) and the mechanism by which genistein inhibits TPK signal transduction. The first effect was observed by methyl-thiazol-diphenyl-tetrazolium assay and the second by [gamma-(32)p] adenosine triphosphate incorporation assay. The results demonstrated that genistein inhibits the proliferation and function of HSFBs and changes the TPK signal transduction pathway, which can provide an experimental basis for treating HS with genistein.

Stromal cell-derived factor 1 (SDF-1) accelerated skin wound healing by promoting the migration and proliferation of epidermal stem cells

Epidermal stem cells could contribute to skin repair through the migration of cells from the neighboring uninjured epidermis, infundibulum, hair follicle, or sebaceous gland. However, little is known about the factors responsible for the complex biological processes in wound healing. Herein, we will show that the attracting chemokine, SDF-1/CXCR4, is a major regulator involved in the migration of epidermal stem cells during wound repair. We found that the SDF-1 levels were markedly increased at the wound margins following injury and CXCR4 expressed in epidermal stem cells and proliferating epithelial cells. Blocking the SDF-1/CXCR4 axis resulted in a significant reduction in epidermal stem cell migration toward SDF-1 in vitro and delayed wound healing in vivo, while an SDF-1 treatment enhanced epidermal stem cell migration and proliferation and accelerated wound healing. These results provide direct evidence that SDF-1 promotes epidermal stem cell migration, accelerates skin regeneration, and makes the development of new regenerative therapeutic strategies for wound healing possible.

shRNA targeting SFRP2 promotes the apoptosis of hypertrophic scar fibroblast

Hypertrophic scars result from a dysregulated process in wound healing. Although the basic mechanism is unclear, increased proliferation and decreased cell apoptosis are noticed in the development of hypertrophic scar. In previous study, we found that secreted frizzled-related protein 2 (SFRP2), which was associated with cell proliferation, apoptosis, and differentiation, was dramatically upregulated in hypertrophic scar (HS) tissue. In this study short hairpin RNA (shRNA) targeting SFRP2 was employed to characterize SFRP2 function in hypertrophic scar-derived fibroblasts (HSFb). Cell proliferation was assessed by MTT, dynamic growth curves, and BRDU assays. Meanwhile, Cell apoptosis was detected using fluorescence-activated cell sorting (FACS). Caspase-3 activity was assayed by spectrophotometry. Fibroblast populated collagen lattice (FPCL) model was employed to evaluate the contractility of HSFb. Further, real-time PCR and western blot were used to measure the mRNA and protein expressions of α-SMA in HSFb. In addition, mRNA levels of type I and III procollagen were assayed by quantitative real-time PCR. The results revealed that shRNA targeting SFRP2 significantly promoted the apoptosis of HSFb, while it had no effect on the cell proliferation. Decreased synthesis of a-smooth muscle actin (α-SMA) in HSFb and reduced contraction of fibroblasts in the FPCL model were observed. Quantitative RT-PCR suggested that the mRNAs of type I and III procollagen were significantly downregulated. In conclusion, as a novel anti-apoptosis gene, SPRP2 was present in hypertrophic scars. Importantly, shRNA targeting SFRP2 may provide a new approach to preventing the formation of HS.

SFRP2 and Slug Contribute to Cellular Resistance to Apoptosis in Hypertrophic Scars

Hypertrophic scars (HS) are skin disorders which occur after wounding and thermal injury. Our previous studies have suggested that secreted frizzled-related protein 2 (SFRP2) is involved in HS formation and that the suppression of SFRP2 promotes apoptosis of hypertrophic scar fibroblasts (HSFBs). However, the mechanisms have not been clarified. Previous studies revealed that Slug expression inhibits cell apoptosis, in vitro and in vivo, and SFRP2 regulates the expression of Slug in cervical cancer cells. In the present study, we quantified differential expression levels of expression of SFRP2 and Slug in HS and normal skin tissues by immunohistochemistry, both of which have important anti-apoptosis roles. Furthermore, a short hairpin RNA approach was adopted to investigate the potential function of SFRP2 and Slug in HSFB apoptosis. Cell apoptosis was detected using fluorescence-activated cell sorting and Caspase-3 activity was assayed by spectrophotometry. This study demonstrates that SFRP2 expression, as well as Slug, is dramatically up-regulated in HS relative to normal skin tissues, and the Slug expression is positively correlated with SFRP2. Slug expression was down-regulated in SFRP2-deficient cells, and the down-regulation of Slug expression increased sensitivity to apoptosis which was induced through a caspase-3-dependent pathway. The infected cells with reduced levels of Slug were tested for the expression of apoptosis-related genes (Bcl-2, Bax and PUMA) which were previously identified as Slug targets. Bcl-2 expression was down-regulated in Slug-deficient cells. In conclusion, SFRP2 appears to interact with Slug to affect the apoptosis of hypertrophic scar fibroblasts.

MicroRNA-98 inhibits the cell proliferation of human hypertrophic scar fibroblasts via targeting Col1A1

BackgroundHypertrophic scarring (HS) is a severe disease, and results from unusual wound healing. Col1A1 could promote the hypertrophic scar formation, and the expression of Col1A1 in HS tissue was markedly higher than that in the normal. In present study, we aimed to identify miRNAs as post-transcriptional regulators of Col1A1 in HS.MethodsMicroRNA-98 was selected as the key miRNA comprised in HS. The mRNA levels of miR-98 in HS tissues and the matched normal skin tissues were determined by qRT-PCR. MTT and flow cytometry were used to determine the influence of miR-98 on cell proliferation and apoptosis of HSFBs, respectively. Col1A1 was found to be the target gene of miR-98 using luciferase reporter assay. Luciferase assay was performed to determine the relative luciferase activity in mimic NC, miR-98 mimic, inhibitor NC and miR-98 inhibitor with Col1A13′-UTR wt or Col1A13′-UTR mt reporter plasmids. The protein expression of Col1A1 in HSFBs after transfection with mimic NC, miR-98 mimic, inhibitor NC and miR-98 inhibitor were determined by western blotting.ResultsThe mRNA level of miR-98 in HS tissues was much lower than that in the control. Transfection of HSFBs with a miR-98 mimic reduced the cell viability of HSFBs and increased the apoptosis portion of HSFBs, while inhibition of miR-98 increased cell viability and decreased apoptosis portion of HSFBs. miR-98 inhibitor increased the relative luciferase activity significantly when cotransfected with the Col1A1-UTR reporter plasmid, while the mutant reporter plasmid abolished the miR-98 inhibitor-mediated increase in luciferase activity. Western blotting revealed that overexpression of miR-98 decreased the expression of Col1A1.ConclusionsOverexpression of miR-98 repressed the proliferation of HSFBs by targeting Col1A1.

High glucose inhibits ClC-2 chloride channels and attenuates cell migration of rat keratinocytes

Background Accumulating evidence has demonstrated that migration of keratinocytes is critical to wound epithelialization, and defects of this function result in chronic delayed-healing wounds in diabetes mellitus patients, and the migration has been proved to be associated with volume-activated chloride channels. The aim of the study is to investigate the effects of high glucose (HG, 25 mM) on ClC-2 chloride channels and cell migration of keratinocytes. Methods Newborn Sprague Dawley rats were used to isolate and culture the keratinocyte in this study. Immunofluorescence assay, real-time polymerase chain reaction, and Western blot assay were used to examine the expression of ClC-2 protein or mRNA. Scratch wound assay was used to measure the migratory ability of keratinocytes. Transwell cell migration assay was used to measure the invasion and migration of keratinocytes. Recombinant lentivirus vectors were established and transducted to keratinocytes. Whole-cell patch clamp was used to perform the electrophysiological studies. Results We found that the expression of ClC-2 was significantly inhibited when keratinocytes were exposed to a HG (25 mM) medium, accompanied by the decline of volume-activated Cl− current (ICl,vol), migration potential, and phosphorylated PI3K as compared to control group. When knockdown of ClC-2 by RNAi or pretreatment with wortmannin, similar results were observed, including ICl,vol and migration keratinocytes were inhibited. Conclusion Our study proved that HG inhibited ClC-2 chloride channels and attenuated cell migration of rat keratinocytes via inhibiting PI3K signaling.

RhoA promotes epidermal stem cell proliferation via PKN1-cyclin D1 signaling.

Objective Epidermal stem cells (ESCs) play a critical role in wound healing, but the mechanism underlying ESC proliferation is not well defined. Here, we explore the effects of RhoA on ESC proliferation and the possible underlying mechanism. Methods Human ESCs were enriched by rapid adhesion to collagen IV. RhoA(+/+)(G14V), RhoA(-/-)(T19N) and pGFP control plasmids were transfected into human ESCs. The effect of RhoA on cell proliferation was detected by cell proliferation and DNA synthesis assays. Induction of PKN1 activity by RhoA was determined by immunoblot analysis, and the effects of PKN1 on RhoA in terms of inducing cell proliferation and cyclin D1 expression were detected using specific siRNA targeting PKN1. The effects of U-46619 (a RhoA agonist) and C3 transferase (a RhoA antagonist) on ESC proliferation were observed in vivo. Results RhoA had a positive effect on ESC proliferation, and PKN1 activity was up-regulated by the active RhoA mutant (G14V) and suppressed by RhoA T19N. Moreover, the ability of RhoA to promote ESC proliferation and DNA synthesis was interrupted by PKN1 siRNA. Additionally, cyclin D1 protein and mRNA expression levels were up-regulated by RhoA G14V, and these effects were inhibited by siRNA-mediated knock-down of PKN1. RhoA also promoted ESC proliferation via PKN in vivo. Conclusion This study shows that the effect of RhoA on ESC proliferation is mediated by activation of the PKN1-cyclin D1 pathway in vitro, suggesting that RhoA may serve as a new therapeutic target for wound healing.

Osteopontin activates mesenchymal stem cells to repair skin wound

Mesenchymal stem cells (MSCs) are promising candidates for skin wound repair due to their capabilities of accumulating at wounds and differentiating into multiple types of skin cells. However, the underlying mechanisms responsible for these processes remain unclear. In this study, we found that osteopontin (OPN) stimulated the migration of MSCs in vitro, and observed the recruitment of endogenous MSCs to a skin wound and their differentiation into keratinocytes and endothelial cells. In OPN knock-out mice, the recruitment of MSCs to the skin wound was significantly inhibited, and wound closure was hampered after an intradermal injection of exogenous MSCs compared to wild-type mice. Consistent with these observations, the expressions of adhesion molecule CD44 and its receptor E-selectin were significantly decreased in the lesions of OPN knock-out mice compared with wild-type mice suggesting that OPN may regulate the migration of MSCs through its interactions with CD44 during skin wound recovery. In summary, our data demonstrated that OPN played a critical role in activating the migration of MSCs to injured sites and their differentiation into specific skin cell types during skin wound healing.

Smac/DIABLO regulates the apoptosis of hypertrophic scar fibroblasts

In abnormal skin wound healing, hypertrophic scars (HS) are characterized by excessive fibroblast hypercellularity and an overproduction of collagen, leading to atypical extracellular matrix (ECM) remodeling. Although the exact mechanisms of HS remain unclear, decreased HS fibroblast (HSFB) apoptosis and increased proliferation are evident in the development of HS. In this study, the contribution of the second mitochondria-derived activator of caspases/direct inhibitor of apoptosis protein (IAP)-binding protein with a low isoelectric point (pI) (Smac/DIABLO), an apoptosis-promoting protein released from the mitochondria, was investigated in human normal skin and HSFB cultures. The expression of Smac/DIABLO is usually decreased in many malignant tumors compared with normal tissues. Immunohistochemical analysis of skin tissues and the western blot analyses of fibroblasts revealed that the expression of Smac/DIABLO was lower in HS tissues compared with normal skin tissues. Of note, adenovirus-mediated Smac/DIABLO overexpression in the cultured HSFBs significantly reduced cell proliferation, as detected by the cell counting kit-8, and increased caspase-3 and -9 activity, as detected by spectrofluorimetry. In addition, it increased apoptosis, as detected by fluorescence-activated cell sorting (FACS). Furthermore, we found that the silencing of Smac with siRNA in the HSFBs induced a noticeable decrease in caspase-3 and -9 activity, leading to a significant reduction in apoptosis. In addition, the mRNA expression of type I and III pro-collagen detected in the HSFBs was significantly increased following the silencing of Smac with siRNA and was inhibited following Smac/DIABLO overexpression, as shown by real-time RT-PCR. In conclusion, Smac/DIABLO decreases the proliferation and increases the apoptosis of HSFBs. To our knowledge, the data from our study suggest for the first time that Smac/DIABLO is a novel therapeutic target for HS.