The Effects of the Transforming Growth Factor-β1 (TGF-β1) Signaling Pathway on Cell Proliferation and Cell Migration are Mediated by Ubiquitin Specific Protease 4 (USP4) in Hypertrophic Scar Tissue and Primary Fibroblast Cultures

Binding of Vialinin A and p-Terphenyl Derivatives to Ubiquitin-Specific Protease 4 (USP4): A Molecular Docking Study

The para-terphenyl derivative vialinin A (Vi-A), isolated from Thelephora fungi, has been characterized as a potent inhibitor of the ubiquitin-specific protease 4 (USP4). Blockade of USP4 contributes to the anti-inflammatory and anticancer properties of the natural product. We have investigated the interaction of Vi-A with USP4 by molecular modeling, to locate the binding site (around residue V98 within the domain in USP segment) and to identify the binding process and interaction contacts. From this model, a series of 32 p-terphenyl compounds were tested as potential USP4 binders, mainly in the vialinin, terrestrin and telephantin series. We identified 11 compounds presenting a satisfactory USP4 binding capacity, including two fungal products, vialinin B and aurantiotinin A, with a more favorable empirical energy of USP4 interaction (ΔE) than the reference product Vi-A. The rare p-terphenyl aurantiotinin A, isolated from the basidiomycete T. aurantiotincta, emerged as a remarkable USP4 binder. Structure-binding relationships have been identified and discussed, to guide the future design of USP4 inhibitors based on the p-terphenyl skeleton. The docking study should help the identification of other protease inhibitors from fungus.

Effect of Mortalin on Scar Formation in Human Dermal Fibroblasts and a Rat Incisional Scar Model

Wound healing is a complicated cascading process; disequilibrium among reparative processes leads to the formation of pathologic scars. Herein, we explored the role of mortalin in scar formation and its association with the interleukin-1α receptor using in vitro and in vivo models. To investigate the effects of mortalin, we performed an MTT cell viability assay, qRT-PCR, and Western blot analyses, in addition to immunofluorescence and immunoprecipitation studies using cultured fibroblasts. A rat incisional wound model was used to evaluate the effect of a mortalin-specific shRNA (dE1-RGD/GFP/shMot) Ad vector in scar tissue. In vitro, the mortalin-treated human dermal fibroblast displayed a significant increase in proliferation of type I collagen, α-smooth muscle actin, transforming growth factor-β, phospho-Smad2/3-complex, and NF-κB levels. Immunofluorescence staining revealed markedly increased mortalin and interleukin-1α receptor protein in keloid tissue compared to those in normal tissue, suggesting that the association between mortalin and IL-1α receptor was responsible for the fibrogenic effect. In vivo, mortalin-specific shRNA-expressing Ad vectors significantly decreased the scar size and type-I-collagen, α-SMA, and phospho-Smad2/3-complex expression in rat incisional scar tissue. Thus, dE1-RGD/GEP/shMot can inhibit the TGF-β/α-SMA axis and NF-κB signal pathways in scar formation, and blocking endogenous mortalin could be a potential therapeutic target for keloids.

Anlotinib Inhibits PFKFB3-Driven Glycolysis in Myofibroblasts to Reverse Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal disease in which the normal alveolar network is gradually replaced by fibrotic scars. Current evidence suggests that metabolic alterations correlate with myofibroblast activation in IPF. Anlotinib has been proposed to have antifibrotic effects, but the efficacy and mechanisms of anlotinib against lung fibrosis have not been systematically evaluated. The antifibrotic effects of anlotinib were evaluated in bleomycin-induced mouse models and transforming growth factor-beta 1 (TGF-β1)-stimulated lung fibroblasts. We measured lactate levels, 2-NBDG glucose uptake and the extracellular acidification rate (ECAR) to assess glycolysis in fibroblasts. RNA-protein coimmunoprecipitation (RIP) and polysome analyses were performed to investigate novel mechanisms of glycolytic reprogramming in pulmonary fibrosis. We found that anlotinib diminished myofibroblast activation and inhibited the augmentation of glycolysis. Moreover, we show that PCBP3 posttranscriptionally increases PFKFB3 expression by promoting its translation during myofibroblast activation, thus promoting glycolysis in myofibroblasts. Regarding mechanism, anlotinib exerts potent antifibrotic effects by downregulating PCBP3, reducing PFKFB3 translation and inhibiting glycolysis in myofibroblasts. Furthermore, we observed that anlotinib had preventative and therapeutic antifibrotic effects on bleomycin-induced pulmonary fibrosis. Therefore, we identify PCBP3 as a protein involved in the regulation of glycolysis reprogramming and lung fibrogenesis and propose it as a therapeutic target for pulmonary fibrosis. Our data suggest that anlotinib has antifibrotic effects on the lungs, and we provide a novel mechanism for this effect. Anlotinib may constitute a novel and potent candidate for the treatment of pulmonary fibrosis.

Network Meta-Analysis of Different Clinical Commonly Used Drugs for the Treatment of Hypertrophic Scar and Keloid

Background: There is no uniform treatment for pathological scars, including keloids and hypertrophic scars, in clinic currently. Previously, multiple randomized controlled trials have examined the clinical efficacy of different treatments. Nonetheless, the results are inconsistent, and many treatments have not been directly compared. This makes it difficult to conclude which approach is more favorable, in terms of efficacy and safety, for the treatment of pathological scarring. This study aimed at evaluating the efficacy of different injection and topical treatment strategies for hypertrophic scar and keloid.

Methods: Relevant literature from PubMed, Medline, Embase, Scopus, the Cochrane Central Register of Controlled Trials (CCRCT), and WHO International Clinical Trials Registry Platform (WHO-ICTRP) were searched, from database inception through November 2020. Randomized clinical trials evaluating different treatment strategies of pathological scars, including triamcinolone acetonide (TAC), verapamil (VER), 5-fluorouracil (5-FU), botulinum toxin A (BTA), bleomycin (BLM), and silicone gels were included in the study.

Results: The network meta-analysis included a total of 2,009 patients from 29 studies. A network meta-analysis of injection and topical treatment strategies showed that the efficacy of TAC combined with BTA was best in the treatment of pathological scars. Combination therapies of TAC with 5-FU and TAC with BTA significantly improved the clinical efficiency. However, there was no statistically significant difference between other treatment strategies. The order of efficacy predicted by the surface under the cumulative ranking (SUCRA) curve was as follows: TAC+BTA (82.2%) > TAC+5-FU (69.8%) > BTA (67.3%) > 5-FU+silicone (59.4%) > TAC+silicone (58.3%) > 5-FU (49.8%) > BLM (42.0%) > TAC (26.7%) > VER (26.2%) > silicone (18.3%). There was no publication bias revealed based on the funnel diagram.

Conclusion: This study recommends intralesional injection of TAC-BTA and TAC-5-FU combined therapies. But for patients who cannot tolerate the side effects, the use of silicone gels in combination with TAC is recommended. However, these conclusions need to be further confirmed by more randomized controlled trials.

LncRNA PICSAR binds to miR-485-5p and activates TGF-β1/Smad to promote abnormal proliferation of hypertrophic scar fibroblasts (HSFs) and excessive deposition of extracellular matrix (ECM)

The purpose of this study is to explore whether LncRNA PICSAR binds to miR-485-5p and thereby activates TGF-β1/Smad signaling pathway, influencing the abnormal proliferation of fibroblasts and excessive deposition of ECM in hypertrophic scar formation. PICSAR and miR-485-5p expressions were detected by qPCR. Cell proliferation was examined by CCK-8. Protein expressions were determined by western blot. Immunofluorescence detected the Ki-67 expression. Dual-luciferase followed by immunoprecipitation was performed to verify the interaction between PICSAR and miR-485-5p. Interference with PICSAR inhibited the abnormal proliferation of hypertrophic scar fibroblasts (HSFs) and the excessive deposition of ECM. It was also confirmed in our study that MiR-485-5p is a direct target of PICSAR in HSFs. Additionally, inhibition of miR-485-5p reversed the effect of PICSAR knockdown in HSFs. LncRNA PICSAR binds to miR-485-5p and thereby activates TGF-β1/Smad signaling pathway, promoting the abnormal proliferation of fibroblasts and excessive deposition of ECM in hypertrophic scar formation.

Spotlight on USP4: Structure, Function, and Regulation

The deubiquitinating enzyme (DUB)–mediated cleavage of ubiquitin plays a critical role in balancing protein synthesis and degradation. Ubiquitin-specific protease 4 (USP4), a member of the largest subfamily of cysteine protease DUBs, removes monoubiquitinated and polyubiquitinated chains from its target proteins. USP4 contains a DUSP (domain in USP)–UBL (ubiquitin-like) domain and a UBL-insert catalytic domain, sharing a common domain organization with its paralogs USP11 and USP15. USP4 plays a critical role in multiple cellular and biological processes and is tightly regulated under normal physiological conditions. When its expression or activity is aberrant, USP4 is implicated in the progression of a wide range of pathologies, especially cancers. In this review, we comprehensively summarize the current knowledge of USP4 structure, biological functions, pathological roles, and cellular regulation, highlighting the importance of exploring effective therapeutic interventions to target USP4.

The Ubiquitin Proteasome System and Skin Fibrosis

The ubiquitin proteasome system (UPS) is a highly conserved way to regulate protein turnover in cells. The UPS hydrolyzes and destroys variant or misfolded proteins and finely regulates proteins involved in differentiation, apoptosis, and other biological processes. This system is a key regulatory factor in the proliferation, differentiation, and collagen secretion of skin fibroblasts. E3 ubiquitin protein ligases Parkin and NEDD4 regulate multiple signaling pathways in keloid. Tumor necrosis factor (TNF) receptor-associated factor 4 (TRAF4) binding with deubiquitinase USP10 can induce p53 destabilization and promote keloid-derived fibroblast proliferation. The UPS participates in the occurrence and development of hypertrophic scars by regulating the transforming growth factor (TGF)-β/Smad signaling pathway. An initial study suggests that TNFα-induced protein 3 (TNFAIP3) polymorphisms may be significantly associated with scleroderma susceptibility in individuals of Caucasian descent. Sumoylation and multiple ubiquitin ligases, including Smurfs, UFD2, and KLHL42, play vital roles in scleroderma by targeting the TGF-β/Smad signaling pathway. In the future, drugs targeting E3 ligases and deubiquitinating enzymes have great potential for the treatment of skin fibrosis.

Effect of THBS1 on the Biological Function of Hypertrophic Scar Fibroblasts

Hypertrophic scarring is a skin collagen disease that can occur following skin damage and is unlikely to heal or subside naturally. Since surgical treatment often worsens scarring, it is important to investigate the pathogenesis and prevention of hypertrophic scarring. Thrombospondin-1 (THBS1) is a matrix glycoprotein that can affect fibrosis by activating TGF-β1, which plays a key role in wound repair and tissue regeneration; therefore, we investigated the effects of THBS1 on the biological function of hypertrophic scar fibroblasts. THBS1 expression was measured in hypertrophic scars and adjacent tissues as well as normal fibroblasts, normal scar fibroblasts, and hypertrophic scar fibroblasts. In addition, THBS1 was overexpressed or silenced in hypertrophic scar fibroblasts to determine the effects of THBS1 on cell proliferation, apoptosis, and migration, as well as TGF-β1 expression. Finally, the role of THBS1 in hypertrophic scarring was confirmed in vivo using a mouse model. We found that THBS1 expression was increased in hypertrophic scar tissues and fibroblasts and promoted the growth and migration of hypertrophic scar fibroblasts as well as TGF-β1 expression. Interestingly, we found that si-THBS1 inhibited the occurrence and development of bleomycin-induced hypertrophic scars in vivo and downregulated TGF-β1 expression. Together, our findings suggest that THBS1 is abnormally expressed in hypertrophic scars and can induce the growth of hypertrophic scar fibroblasts by regulating TGF-β1. Consequently, THBS1 could be an ideal target for treating hypertrophic scarring.