Epigenetics as a versatile regulator of fibrosis.

Fibrosis, a process caused by excessive deposition of extracellular matrix (ECM), is a common cause and outcome of organ failure and even death. Researchers have made many efforts to understand the mechanism of fibrogenesis and to develop therapeutic strategies; yet, the outcome remains unsatisfactory. In recent years, advances in epigenetics, including chromatin remodeling, histone modification, DNA methylation, and noncoding RNA (ncRNA), have provided more insights into the fibrotic process and have suggested the possibility of novel therapy for organ fibrosis. In this review, we summarize the current research on the epigenetic mechanisms involved in organ fibrosis and their possible clinical applications.

Salvianolic Acid B Reduces the Inflammation of Fat Grafts by Inhibiting the NF-Kb Signalling Pathway in Macrophages.

BACKGROUND: Autologous fat grafting is a common method for soft tissue defect repair. However, the high absorption rate of transplanted fat is currently a bottleneck in the process. Excessive inflammation is one of the main reasons for poor fat transplantation. Salvianolic acid B (Sal-B) is a herbal medicine that shows promise for improving the effectiveness of fat transplantation. OBJECTIVE: The aim of this study was to improve fat graft survival by injecting Sal-B into fat grafts locally. METHODS: In vivo, 0.2 mL of Coleman fat was transplanted into nude mice along with Sal-B. The grafts were evaluated by histologic analysis at 2, 4, and 12 weeks posttransplantation and by microcomputed tomography at 4 weeks posttransplantation. In vitro ribonucleic acid sequencing, cell proliferation assays, anti-inflammatory activity assays, molecular docking studies, and kinase activity assays were performed in RAW264.7 cells to detect the potential mechanism. RESULTS: Sal-B significantly improved fat graft survival and attenuated adipose tissue fibrosis and inflammation. Sal-B also inhibited the polarization of M1 macrophages in fat grafts. In vitro, Sal-B inhibited the proliferation and activation of inflammatory pathways in RAW264.7 cells. In addition, Sal-B had an inhibitory effect on NF-κB (nuclear factor κ light polypeptide gene enhancer in B cells) signaling. This bioactivity of Sal-B may result from its selective binding to the kinase domain of the inhibitor of NF-κB kinase subunit ß. CONCLUSIONS: Sal-B could serve as a promising agent for improving the effect of fat transplantation by inhibiting the polarization of M1 macrophages through NF-κB signaling.

Exosome-delivered CD44v6/C1QBP complex drives pancreatic cancer liver metastasis by promoting fibrotic liver microenvironment.

OBJECTIVE: Pancreatic ductal adenocarcinoma (PDAC) shows a remarkable predilection for liver metastasis. Pro-oncogenic secretome delivery and trafficking via exosomes are crucial for pre-metastatic microenvironment formation and metastasis. This study aimed to explore the underlying mechanisms of how PDAC-derived exosomes (Pex) modulate the liver microenvironment and promote metastasis. DESIGN: C57BL/6 mice were 'educated' by tail vein Pex injection. The intrasplenic injection liver metastasis and PDAC orthotopic transplantation models were used to evaluate liver metastasis. Stable cell lines CD44v6 (CD44 variant isoform 6) or C1QBP (complement C1q binding protein) knockdown or overexpression was established using lentivirus transfection or gateway systems. A total of 142 patients with PDAC in Huashan Hospital were retrospectively enrolled. Prognosis and liver metastasis were predicted using Kaplan-Meier survival curves and logistic regression models. RESULTS: Pex tail vein injection induced the deposition of liver fibrotic extracellular matrix, which promoted PDAC liver metastasis. Specifically, the exosomal CD44v6/C1QBP complex was delivered to the plasma membrane of hepatic satellite cells (HSCs), leading to phosphorylation of insulin-like growth factor 1 signalling molecules, which resulted in HSC activation and liver fibrosis. Expression of Pex CD44v6 and C1QBP in PDAC patients with liver metastasis was significantly higher than in PDAC patients without liver metastasis, and simultaneous high expression of exosomal CD44v6 and C1QBP correlated with a worse prognosis and a higher risk of postoperative PDAC liver metastasis. CONCLUSION: The Pex-derived CD44v6/C1QBP complex is essential for the formation of a fibrotic liver microenvironment and PDAC liver metastasis. Highly expressed exosomal CD44v6 and C1QBP are promising biomarkers for predicting prognosis and liver metastasis in patients with PDAC.

LRG-1 promotes fat graft survival through the RAB31-mediated inhibition of hypoxia-induced apoptosis.

Autologous adipose tissue is an ideal soft tissue filling material, and its biocompatibility is better than that of artificial tissue substitutes, foreign bodies and heterogeneous materials. Although autologous fat transplantation has many advantages, the low retention rate of adipose tissue limits its clinical application. Here, we identified a secretory glycoprotein, leucine-rich-alpha-2-glycoprotein 1 (LRG-1), that could promote fat graft survival through RAB31-mediated inhibition of hypoxia-induced apoptosis. We showed that LRG-1 injection significantly increased the maintenance of fat volume and weight compared with the control. In addition, higher fat integrity, more viable adipocytes and fewer apoptotic cells were observed in the LRG-1-treated groups. Furthermore, we discovered that LRG-1 could reduce the ADSC apoptosis induced by hypoxic conditions. The mechanism underlying the LRG-1-mediated suppression of the ADSC apoptosis induced by hypoxia was mediated by the upregulation of RAB31 expression. Using LRG-1 for fat grafts may prove to be clinically successful for increasing the retention rate of transplanted fat.

Ubiquitin-Specific Protease 15 Maintains Transforming Growth Factor-ß Pathway Activity by Deubiquitinating Transforming Growth Factor-ß Receptor I during Wound Healing.

Wound healing is a process of cutaneous barrier reconstruction that occurs after skin injury and involves diverse cytokines and cell types. Similar to several deubiquitinating enzymes, ubiquitin-specific protease 15 (USP15) can remove ubiquitin chains from specific proteins to rescue them from degradation. However, the regulatory role of USP15 in wound healing remains unclear. We investigated the dynamic function of USP15 in wound healing. First, in USP15 knockout mice, we observed a significant delay in wound closure. In addition, inhibition of cell proliferation and migration was observed in USP15-silenced human dermal fibroblasts. Through RNA sequencing, it was revealed that the transforming growth factor-ß (TGF-ß) pathway was suppressed after USP15 knockdown. Furthermore, coimmunoprecipitation demonstrated that USP15 could interact with TGF-ß receptor I and promote its deubiquitination, thereby maintaining TGF-ß signaling pathway activity by enhancing TGF-ß receptor I stability. These observations shed light on the function and mechanisms of USP15-mediated modulation of the TGF-ß signaling pathway during wound healing, thus providing a novel potential target for the treatment of refractory wounds.

Alisol A attenuates high-fat-diet-induced obesity and metabolic disorders via the AMPK/ACC/SREBP-1c pathway.

Obesity and its associated metabolic disorders such as diabetes, hepatic steatosis and chronic heart diseases are affecting billions of individuals. However there is no satisfactory drug to treat such diseases. In this study, we found that alisol A, a major active triterpene isolated from the Chinese traditional medicine Rhizoma Alismatis, could significantly attenuate high-fat-diet-induced obesity. Our biochemical detection demonstrated that alisol A remarkably decreased lipid levels, alleviated glucose metabolism disorders and insulin resistance in high-fat-diet-induced obese mice. We also found that alisol A reduced hepatic steatosis and improved liver function in the obese mice model.In addition, protein expression investigation revealed that alisol A had an active effect on AMPK/ACC/SREBP-1c pathway. As suggested by the molecular docking study, such bioactivity of alisol A may result from its selective binding to the catalytic region of AMPK.Therefore, we believe that Alisol A could serve as a promising agent for treatment of obesity and its related metabolic diseases.

Calcimycin Suppresses S100A4 Expression and Inhibits the Stimulatory Effect of Transforming Growth Factor ß1 on Keloid Fibroblasts.

Recent researches have indicated that S100A4 participates in tissue fibrosis, whereas calcimycin inhibits this process as a novel S100A4 transcription inhibitor. However, the relationship and mechanisms between calcimycin and S100A4 in keloid fibroblasts (KFs) remain unknown. The present research was aimed to evaluate the effect of calcimycin on S100A4 expression and pathogenesis in KFs. Keloid fibroblasts were cultured and exposed to different concentrations of calcimycin in the absence or presence of transforming growth factor ß1 (TGF-ß1). The results showed that the expression of S100A4 was significantly increased in keloid derived fibroblasts compared with normal skin fibroblasts. Calcimycin depressed S100A4 in a concentration- and time-dependent manner. Moreover, calcimycin suppressed TGF-ß1-induced collagen type I, fibronectin, and α-smooth muscle actin expression and cell viability in cultured KFs. Furthermore, calcimycin modulated expression of TGF-ß/Smad target genes Smad7 and phosphorylation of TGF-ß1-induced Smad2/3. This research for the first time confirmed the presence of S100A4 in KFs. Calcimycin inhibits the expression of S100A4, as well as KF proliferation and migration and extracellular matrix (ECM) synthesis. Taken together, these results indicate that calcimycin might be a therapeutic candidate to keloid or other related fibrotic disorders.

Topical Application of TT-10 Ameliorates Impaired Wound Healing.

BACKGROUND: In recent decades, chronic wounds have become an increasingly significant clinical concern due to their increasing morbidity and socioeconomic toll. However, there is currently no product available on the market that specifically targets this intricate process. One clear indicator of delayed wound repair is the inhibition of re-epithelialization. Yes-associated protein (YAP), which is a potential focal point for tissue repair and regeneration, has been shown to be prominent in several studies. In this context, we have identified the pharmacological product TT-10, which is a YAP activator, as a potential candidate for the treatment of various forms of chronic wounds. METHODS: The role of TT-10 in regulating YAP activity and subcellular localization was determined by western blotting and immunofluorescence staining. The effect of TT-10 on the biological functions of keratinocytes was assessed by proliferation, wound healing, and apoptosis assays. The impairment of YAP activity in chronic wounds was measured in human and mouse tissues. The in vivo efficacy of TT-10 was examined by gross examination, H&E staining, and measuring wound areas and gaps in normal, diabetic, and ischemic wounds. RESULTS: Our findings suggest that TT-10 facilitates the nuclear transport of YAP, consequently increasing YAP activity, which in turn increases the proliferation and migration of keratinocytes. Moreover, we showed that intracutaneous injection of TT-10 along the wound periphery promoted re-epithelization via YAP activation in the epidermis, culminating in accelerated wound closure in several chronic wound healing models. CONCLUSIONS: Our research highlights the potential of TT-10 to treat chronic wounds, which is a persistent challenge in tissue repair.

Mechanisms and translational applications of regeneration in limbs: From renewable animals to humans.

BACKGROUND: The regenerative capacity of organisms declines throughout evolution, and mammals lack the ability to regenerate limbs after injury. Past approaches to achieving successful restoration through pharmacological intervention, tissue engineering, and cell therapies have faced significant challenges. OBJECTIVES: This review aims to provide an overview of the current understanding of the mechanisms behind animal limb regeneration and the successful translation of these mechanisms for human tissue regeneration. RESULTS: Particular attention was paid to the Mexican axolotl (Ambystoma mexicanum), the only adult tetrapod capable of limb regeneration. We will explore fundamental questions surrounding limb regeneration, such as how amputation initiates regeneration, how the limb knows when to stop and which parts to regenerate, and how these findings can apply to mammalian systems. CONCLUSIONS: Given the urgent need for regenerative therapies to treat conditions like diabetic foot ulcers and trauma survivors, this review provides valuable insights and ideas for researchers, clinicians, and biomedical engineers seeking to facilitate the regeneration process or elicit full regeneration from partial regeneration events.

Salvianolic acid B protects against UVB-induced skin aging via activation of NRF2.

BACKGROUND: Prolonged exposure to sun radiation may result in harmful skin photoaging. Therefore, discovering novel anti-photoaging treatment modalities is critical. An active component isolated from Salvia miltiorrhiza (SM), Salvianolic acid B (Sal-B), is a robust antioxidant and anti-inflammatory agent. This investigation aimed to discover the therapeutic impact and pathways of salvianolic acid B for UVB-induced skin photoaging, an area that remains unexplored. METHODS: We conducted in vitro experiments on human dermal fibroblasts (HDFs) exposed to UVB radiation, assessing cellular senescence, superoxide dismutase (SOD) activity, cell viability, proliferation, migration, levels of reactive oxygen species (ROS), and mitochondrial health. The potential mechanism of Sal-B was analyzed using RNA sequencing, with further validation through Western blotting, PCR, and nuclear factor erythroid 2-related factor 2 (NRF2) silencing methods. In vivo, a model of skin photoaging induced by UVB in nude mice was employed. The collagen fiber levels were assessed utilizing hematoxylin and eosin (H&E), Masson, and Sirus red staining. Additionally, NRF2 and related gene and protein expression levels were identified utilizing PCR and Western blotting. RESULTS: Sal-B was found to significantly counteract photoaging in UVB-exposed skin fibroblasts, reducing aging-related decline in fibroblast proliferation and an increase in apoptosis. It was observed that Sal-B aids in protecting mitochondria from excessive ROS production by promoting NRF2 nuclear translocation. NRF2 knockdown experiments established its necessity for Sal-B's anti-photoaging effects. The in vivo studies also verified Sal-B's anti-photoaging efficacy, surpassing that of tretinoin (Retino-A). These outcomes offer novel insights into the contribution of Sal-B in developing clinical treatment modalities for UVB-induced photodamage in skin fibroblasts. CONCLUSION: In this investigation, we identified the Sal-B protective impact on the senescence of dermal fibroblasts and skin photoaging induced by radiation of UVB. The outcomes suggest Sal-B as a potential modulator of the NRF2 signaling pathway.

Matrix stiffness-induced α-tubulin acetylation is required for skin fibrosis formation through activation of Yes-associated protein.

Skin fibrosis, a pathological process featured by fibroblast activation and extracellular matrix (ECM) deposition, makes a significant contribution to morbidity. Studies have identified biomechanics as the central element in the complex network of fibrogenesis that drives the profibrotic feedback loop. In this study, we found that the acetylation of α-tubulin at lysine 40 (K40) was augmented in fibrotic skin tissues. Further analysis showed that α-tubulin acetylation is required for fibroblast activation, including contraction, migration, and ECM deposition. More importantly, we revealed that biomechanics-induced upregulation of K40 acetylation promotes fibrosis by mediating mechanosensitive Yes-associated protein S127 dephosphorylation and its cytoplasm nucleus shuttle. Furthermore, we demonstrated that the knockdown of α-tubulin acetyltransferase 1 could rescue the K40 acetylation upregulation caused by increased matrix rigidity and ameliorate skin fibrosis both in vivo and in vitro. Herein, we highlight the critical role of α-tubulin acetylation in matrix stiffness-induced skin fibrosis and clarify a possible molecular mechanism. Our research suggests α-tubulin acetylation as a potential target for drug design and therapeutic intervention.

Advancements in adipose-derived stem cell therapy for skin fibrosis.

Pathological scarring and scleroderma, which are the most common conditions of skin fibrosis, pathologically manifest as fibroblast proliferation and extracellular matrix (ECM) hyperplasia. Fibroblast proliferation and ECM hyperplasia lead to fibrotic tissue remodeling, causing an exaggerated and prolonged wound-healing response. The pathogenesis of these diseases has not been fully clarified and is unfortunately accompanied by exceptionally high medical needs and poor treatment effects. Currently, a promising and relatively low-cost treatment has emerged-adipose-derived stem cell (ASC) therapy as a branch of stem cell therapy, including ASCs and their derivatives-purified ASC, stromal vascular fraction, ASC-conditioned medium, ASC exosomes, etc., which are rich in sources and easy to obtain. ASCs have been widely used in therapeutic settings for patients, primarily for the defection of soft tissues, such as breast enhancement and facial contouring. In the field of skin regeneration, ASC therapy has become a hot research topic because it is beneficial for reversing skin fibrosis. The ability of ASCs to control profibrotic factors as well as anti-inflammatory and immunomodulatory actions will be discussed in this review, as well as their new applications in the treatment of skin fibrosis. Although the long-term effect of ASC therapy is still unclear, ASCs have emerged as one of the most promising systemic antifibrotic therapies under development.

Targeting the stem cell niche: role of collagen XVII in skin aging and wound repair.

The skin epidermis and appendages undergo ongoing renewal throughout life. Stem cells residing in the epidermis and hair follicles are pivotal for sustaining skin homeostasis. The self-renewal ability of stem cells significantly decreases during skin aging but actively increases during wound repair. Residential stem cells reside in niches that provide spatially distinct microenvironments for stem cell maintenance and function. Cell-extracellular matrix (ECM) adhesion is essential for the establishment of niche architecture. Collagen XVII (COL17), as a transmembrane protein constituting hemidesmosomes (HDs), mediates the interactions of stem cells with surrounding cells and the matrix to regulate skin homeostasis, aging and wound repair. This review focuses on the pivotal role of the niche component COL17 in stem cell maintenance and its function in regulation of skin aging and wound repair.

Corrigendum: Focusing on Mechanoregulation Axis in Fibrosis: Sensing, Transduction and Effecting.

[This corrects the article DOI: 10.3389/fmolb.2022.804680.].

HDAC5-mediated Smad7 silencing through MEF2A is critical for fibroblast activation and hypertrophic scar formation.

Transforming growth factor-ß (TGF-ß) signaling plays a key role in excessive fibrosis. As a class IIa family histone deacetylase (HDAC), HDAC5 shows a close relationship with TGF-ß signaling and fibrosis. However, the effect and regulatory mechanism of HDAC5 in hypertrophic scar (HS) formation remain elusive. We show that HDAC5 was overexpressed in HS tissues and depletion of HDAC5 attenuated HS formation in vivo and inhibited fibroblast activation in vitro. HDAC5 knockdown (KD) significantly downregulated TGF-ß1 induced Smad2/3 phosphorylation and increased Smad7 expression. Meanwhile, Smad7 KD rescued the Smad2/3 phosphorylation downregulation and scar hyperplasia inhibition mediated by HDAC5 deficiency. Luciferase reporter assays and ChIP-qPCR assays revealed that HDAC5 interacts with myocyte enhancer factor 2A (MEF2A) suppressing MEF2A binding to the Smad7 promoter region, which results in Smad7 promoter activity repression. HDAC4/5 inhibitor, LMK235, significantly alleviated hypertrophic scar formation. Our study provides clues for the development of HDAC5 targeting strategies for the therapy or prophylaxis of fibrotic diseases.

Focusing on Mechanoregulation Axis in Fibrosis: Sensing, Transduction and Effecting.

Fibrosis, a pathologic process featured by the excessive deposition of connective tissue components, can affect virtually every organ and has no satisfactory therapy yet. Fibrotic diseases are often associated with organ dysfunction which leads to high morbidity and mortality. Biomechanical stmuli and the corresponding cellular response havebeen identified in fibrogenesis, as the fibrotic remodeling could be seen as the incapacity to reestablish mechanical homeostasis: along with extracellular matrix accumulating, the physical property became more "stiff" and could in turn induce fibrosis. In this review, we provide a comprehensive overview of mechanoregulation in fibrosis, from initialing cellular mechanosensing to intracellular mechanotransduction and processing, and ends up in mechanoeffecting. Our contents are not limited to the cellular mechanism, but further expand to the disorders involved and current clinical trials, providing an insight into the disease and hopefully inspiring new approaches for the treatment of tissue fibrosis.

Salvianolic acid-B improves fat graft survival by promoting proliferation and adipogenesis.

BACKGROUND: Our previous study proved that Salvia miltiorrhiza could enhance fat graft survival by promoting adipogenesis. However, the effect of salvianolic acid B (Sal-B), the most abundant and bioactive water-soluble compound in Salvia miltiorrhiza, on fat graft survival has not yet been investigated. OBJECTIVE: This study aims to investigate whether salvianolic acid B could improve fat graft survival and promote preadipocyte differentiation. The underlying mechanism has also been studied. METHODS: In vivo, 0.2 ml of Coleman fat was transplanted into nude mice with salvianolic acid B. The grafts were evaluated by HE and IF at 2 and 4 weeks posttransplantation and by micro-CT at 4 weeks posttransplantation. In vitro, the adipogenesis and proliferative activities of salvianolic acid B were analyzed in cultured human adipose-derived stem cells (h-ADSCs) and 3T3-L1 cells to detect the mechanism by which salvianolic acid B affects graft survival. RESULTS: In vivo, the weights and volumes of the fat grafts in the Sal-B-treated groups were significantly higher than those of the fat grafts in the control group. In addition, higher fat integrity and more viable adipocytes were observed in the Sal-B-treated groups. In vitro, salvianolic acid B showed the ability to promote 3T3-L1 and h-ADSC proliferation and adipogenesis. CONCLUSIONS: Our in vitro experiments demonstrated that salvianolic acid B can promote the proliferation of adipose stem cells and enhance the differentiation of adipose stem cells. Simultaneously, in vivo experiments showed that salvianolic acid B can improve the survival rate of fat transplantation. Therefore, our research shed light on the potential therapeutic usage of salvianolic acid B in improving the survival rate of fat transplantation.

LRG1 Promotes Keratinocyte Migration and Wound Repair through Regulation of HIF-1α Stability.

Re-epithelialization is a complex process during skin wound healing, and cell migration is an integral part of this phenomenon. Here we identified a role for LRG1 as a key regulator of epidermal keratinocyte migration where LRG1 acts via enhancement of HIF-1α stability. We showed that LRG1 is upregulated at murine skin wound edges and that addition of recombinant human LRG1 accelerates keratinocyte migration and skin wound healing. Furthermore, we identified transcription factor ELK3 as a downstream effector of LRG1. We confirmed that elevated ELK3 levels manipulated by LRG1 can promote cell migration through upregulation of HIF-1α stability. Because hyperglycemia complicatedly affects HIF-1α stability and activation, our findings provide insights into the molecular controls of wound-associated cell migration and identify potential therapeutic targets for the treatment of chronic diabetic wounds. In conclusion, we demonstrated that LRG1 promotes wound repair through keratinocyte migration and is important for normalization of an abnormal process of diabetic wound healing where HIF-1α stability is insufficient.

Early Postoperative Application of Botulinum Toxin Type A Prevents Hypertrophic Scarring after Epicanthoplasty: A Split-Face, Double-Blind, Randomized Trial.

BACKGROUND: Postoperative hypertrophic scarring of the medial canthal area is a common phenomenon and deterrent for patients considering epicanthoplasty. Botulinum toxin type A has been reported for hypertrophic scar and keloid treatment. However, there is a lack of high-level evidence regarding the effects of botulinum toxin type A in the medial canthal area. METHODS: In this split-face, double-blind, randomized trial, 43 consecutive consenting patients undergoing Park Z-epicanthoplasty were randomized to receive 5 U of botulinum toxin type A or the same volume of saline injections at days 6 to 7 postoperatively. Scars were assessed independently using the Vancouver Scar Scale, the visual analogue scale, and patient satisfaction rating at the 1-, 3-, and 6-month follow-ups. RESULTS: Overall, 30 patients completed this trial. The botulinum toxin type A-treated side achieved significantly improved Vancouver Scar Scale scores. The most obvious improvements were observed at the 3-month follow-up visit. Among the four subscores of the Vancouver Scar Scale, the most significantly improved subscores were the height and pliability. The visual analogue scale scores also decreased significantly on the botulinum toxin type A-treated side at all three follow-up visits. Approximately 86.7 percent of the patients were satisfied with the scar and epicanthoplasty outcomes. No severe complications were reported. CONCLUSIONS: Early postoperative botulinum toxin type A injection in the medial canthal region efficiently reduces hypertrophic scarring and improves the outcome of epicanthoplasty. Therefore, botulinum toxin type A injection can be used as a routine method to prevent hypertrophic scarring and improve the outcome of epicanthoplasty. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, II.