Skin fibrosis: Models and mechanisms

BMP1 Promotes Keloid by Inducing Fibroblast Inflammation and Fibrogenesis

Keloid is a typical fibrotic and inflammatory skin disease with unclear mechanisms and few therapeutic targets. In this study, we found that BMP1 was significantly increased in a collagen high-expressing subtype of fibroblast by reanalyzing a public single-cell RNA-sequence data set of keloid. The number of BMP1-positive fibroblast cells was increased in keloid fibrotic loci. Increased levels of BMP1 were further validated in the skin tissues and fibroblasts from keloid patients. Additionally, a positive correlation between BMP1 and the Keloid Area and Severity Index was found in keloid patients. In vitro analysis revealed collagen production, the phosphorylation levels of p65, and the IL-1β secretion decreased in BMP1 interfered keloid fibroblasts. Besides, the knockdown of BMP1 inhibited the growth and migration of keloid fibroblast cells. Mechanistically, BMP1 inhibition downregulated the noncanonical TGF-β pathways, including p-p38 and p-ERK1/2 signaling. Furthermore, we found the delivery of BMP1 siRNAs could significantly alleviate keloid in human keloid-bearing nude mice. Collectively, our results indicated that BMP1 exhibited various pathogenic effects on keloids as promoting cell proliferation, migration, inflammation, and ECM deposition of fibroblast cells by regulating the noncanonical TGF-β/p38 MAPK, and TGF-β/ERK pathways. BMP1-lowing strategies may appear as a potential new therapeutic target for keloid.

Blockade of Sialylation with Decrease in Polysialic Acid Levels Counteracts Transforming Growth Factor β1-Induced Skin Fibroblast-to-Myofibroblast Transition

Aberrant sialylation with overexpression of the homopolymeric glycan polysialic acid (polySia) was recently reported in fibroblasts from fibrotic skin lesions. Yet, whether such a rise in polySia levels or sialylation in general may be functionally implicated in profibrotic activation of fibroblasts and their transition to myofibroblasts remains unknown. Therefore, we herein explored whether inhibition of sialylation could interfere with the process of skin fibroblast-to-myofibroblast transition induced by the master profibrotic mediator transforming growth factor β1 (TGFβ1). Adult human skin fibroblasts were pretreated with the competitive pan-sialyltransferase inhibitor 3-Fax-peracetyl-Neu5Ac (3-Fax) before stimulation with recombinant human TGFβ1, and then analyzed for polySia expression, cell viability, proliferation, migratory ability, and acquisition of myofibroblast-like morphofunctional features. Skin fibroblast stimulation with TGFβ1 resulted in overexpression of polySia, which was effectively blunted by 3-Fax pre-administration. Pretreatment with 3-Fax efficiently lessened TGFβ1-induced skin fibroblast proliferation, migration, changes in cell morphology, and phenotypic and functional differentiation into myofibroblasts, as testified by a significant reduction in FAP, ACTA2, COL1A1, COL1A2, and FN1 gene expression, and α-smooth muscle actin, N-cadherin, COL1A1, and FN-EDA protein levels, as well as a reduced contractile capability. Moreover, skin fibroblasts pre-administered with 3-Fax displayed a significant decrease in Smad3-dependent canonical TGFβ1 signaling. Collectively, our in vitro findings demonstrate for the first time that aberrant sialylation with increased polySia levels has a functional role in skin fibroblast-to-myofibroblast transition and suggest that competitive sialyltransferase inhibition might offer new therapeutic opportunities against skin fibrosis.

Mesenchymal stem cells in craniofacial reconstruction: a comprehensive review

Craniofacial reconstruction faces many challenges, including high complexity, strong specificity, severe injury, irregular and complex wounds, and high risk of bleeding. Traditionally, the "gold standard" for treating craniofacial bone defects has been tissue transplantation, which involves the transplantation of bone, cartilage, skin, and other tissues from other parts of the body. However, the shape of craniofacial bone and cartilage structures varies greatly and is distinctly different from ordinary long bones. Craniofacial bones originate from the neural crest, while long bones originate from the mesoderm. These factors contribute to the poor effectiveness of tissue transplantation in repairing craniofacial defects. Autologous mesenchymal stem cell transplantation exhibits excellent pluripotency, low immunogenicity, and minimally invasive properties, and is considered a potential alternative to tissue transplantation for treating craniofacial defects. Researchers have found that both craniofacial-specific mesenchymal stem cells and mesenchymal stem cells from other parts of the body have significant effects on the restoration and reconstruction of craniofacial bones, cartilage, wounds, and adipose tissue. In addition, the continuous development and application of tissue engineering technology provide new ideas for craniofacial repair. With the continuous exploration of mesenchymal stem cells by researchers and the continuous development of tissue engineering technology, the use of autologous mesenchymal stem cell transplantation for craniofacial reconstruction has gradually been accepted and promoted. This article will review the applications of various types of mesenchymal stem cells and related tissue engineering in craniofacial repair and reconstruction.

Characterization of Different Inflammatory Skin Conditions in a Mouse Model of DNCB-Induced Atopic Dermatitis

The mouse model of 2,4-dinitrochlorbenzene (DNCB)-induced human-like atopic dermatitis (hlAD) has been widely used to test novel treatment strategies and compounds. However, the study designs and methods are highly diverse, presenting different hlAD disease patterns that occur after sensitization and repeated challenge with DNCB on dorsal skin. In addition, there is a lack of information about the progression of the disease during the experiment and the achieved pheno- and endotypes, especially at the timepoint when therapeutic treatment is initiated. We here examine hlAD in a DNCB-induced BALB/cJRj model at different timepoints: (i) before starting treatment with dexamethasone, representing a standard drug control (day 12) and (ii) at the end of the experiment (day 22). Both timepoints display typical AD-associated characteristics: skin thickening, spongiosis, hyper- and parakeratosis, altered cytokine and gene expression, increased lipid mediator formation, barrier protein and antimicrobial peptide abnormalities, as well as lymphoid organ hypertrophy. Increased mast cell infiltration into the skin and elevated immunoglobulin E plasma concentrations indicate a type I allergy response. The DNCB-treated skin showed an extrinsic moderate sub-acute hlAD lesion at day 12 and an extrinsic mild sub-acute to chronic pheno- and endotype at day 22 with a dominating Th2 response. A dependency of the filaggrin formation and expression in correlation to the disease severity in the DNCB-treated skin was found. In conclusion, our study reveals a detailed classification of a hlAD at two timepoints with different inflammatory skin conditions and pheno- and endotypes, thereby providing a better understanding of the DNCB-induced hlAD model in BALB/cJRj mice.

Discovering and Validating Cuproptosis-Associated Marker Genes for Accurate Keloid Diagnosis Through Multiple Machine Learning Models

Background

Keloid is a common condition characterized by abnormal scarring of the skin, affecting a significant number of individuals worldwide.

Objective

The occurrence of keloids may be related to the reduction of cell death. Recently, a new cell death mode that relies on copper ions has been discovered. This study aimed to identify novel cuproptosis-related genes that are associated with keloid diagnosis.

Methods

We utilized several gene expression datasets, including GSE44270 and GSE145725 as the training group, and GSE7890, GSE92566, and GSE121618 as the testing group. We integrated machine learning models (SVM, RF, GLM, and XGB) to identify 10 cuproptosis-related genes (CRGs) for keloid diagnosis in the training group. The diagnostic capability of the identified CRGs was validated using independent datasets, RT-qPCR, Western blotting, and IHC analysis.

Results

Our study successfully categorized keloid samples into two clusters based on the expression of cuproptosis-related genes. Utilizing WGCNA analysis, we identified 110 candidate genes associated with cuproptosis. Subsequent functional enrichment analysis results revealed that these genes may play a regulatory role in cell growth within keloid tissue through the MAPK pathway. By integrating machine learning models, we identified CRGs that can be used for diagnosing keloid. The diagnostic efficacy of CRGs was confirmed using independent datasets, RT-qPCR, Western blotting, and IHC analysis. GSVA analysis indicated that high expression of CRGs influenced the gene set related to ECM receptor interaction.

Conclusion

This study identified 10 cuproptosis-related genes that provide insights into the molecular mechanisms underlying keloid development and may have implications for the development of targeted therapies.

Metformin: A Potential Treatment for Acne, Hidradenitis Suppurativa and Rosacea

Metformin is a widely used drug for treatment of diabetes mellitus, due to its safety and efficacy. In addition to its role as an antidiabetic drug, numerous beneficial effects of metformin have enabled its use in various diseases. Considering the anti-androgenic, anti-angiogenic, anti-fibrotic and antioxidant properties of metformin, it may have the potential to improve chronic inflammatory skin diseases. However, further evidence is needed to confirm the efficacy of metformin in dermatological conditions, This review focuses on exploring the therapeutic targets of metformin in acne vulgaris, hidradenitis suppurativa and rosacea, by studying their pathogeneses.

Topical Administration of an Apoptosis Inducer Mitigates Bleomycin-Induced Skin Fibrosis

Pathological fibrosis is distinguished from physiological wound healing by persistent myofibroblast activation, suggesting that therapies that induce myofibroblast apoptosis selectively could prevent progression and potentially reverse the established fibrosis, such as for scleroderma (a heterogeneous autoimmune disease characterized by multiorgan fibrosis). Navitoclax (NAVI) is a BCL-2/BCL-xL inhibitor with antifibrotic properties and has been investigated as a potential therapeutic for fibrosis. NAVI makes myofibroblasts particularly vulnerable to apoptosis. However, despite NAVI's significant potency, clinical translation of BCL-2 inhibitors, NAVI in this case, is hindered due to the risk of thrombocytopenia. Therefore, in this work, we utilized a newly developed ionic liquid formulation of NAVI for direct topical application to the skin, thereby avoiding systemic circulation and off-target-mediated side effects. The ionic liquid composed of choline and octanoic acid (COA) at a 1:2 molar ionic ratio increases skin diffusion and transportation of NAVI and maintains their retention within the dermis for a prolonged duration. Topical administration of NAVI-mediated BCL-xL and BCL-2 inhibition results in the transition of myofibroblast to fibroblast and ameliorates pre-existing fibrosis, as demonstrated in a scleroderma mouse model. We have observed a significant reduction of α-SMA and collagen, which are known as fibrosis marker proteins, as a result of the inhibition of anti-apoptotic proteins BCL-2/BCL-xL. Overall, our findings show that COA-assisted topical delivery of NAVI upregulates apoptosis specific to myofibroblasts, with minimal presence of the drug in the systemic circulation, resulting in an accelerated therapeutic effect with no discernible drug-associated toxicity.

Laser Therapy Changes the Expression of Matrix Metalloproteinases in Bleomycin-Induced Skin Fibrosis

Matrix metalloproteinases (MMPs) are often considered biomarkers of skin fibrosis. At the early stages of the pathological process, an elevation of their enzymatic activity causes significant changes in the composition of the extracellular matrix. MMPs secreted by immune cells facilitate their migration to the site of damage. Then, the immune cells eliminate the affected cells and biomolecules. Moreover, bidirectional changes in the activity of proteolytic enzymes, including MMPs, accompany wound healing. This study aimed to assess changes in the expression of Mmp2, Mmp3, and Mmp9 after treating mice with laser therapy using the experimental model of bleomycin-induced skin fibrosis. Using immunohistochemistry, we characterized the histological features of scarred skin. We also analyzed changes in the expression of MMPs using real-time polymerase chain reaction before and after laser irradiation. We showed that treatment of the mice with a CO2 laser partially normalized the histological features of scarred skin. We also noticed a decrease in the expression of Mmp2, Mmp3 (both p < 0.05), and Mmp9 (p = 0.065) during scar healing. The obtained results suggest that normalization of skin homeostasis requires control of MMP activity via induction of genes.

Chitosan/Phenolic Compounds Scaffolds for Connective Tissue Regeneration

Chitosan-based scaffolds modified by gallic acid, ferulic acid, and tannic acid were fabricated. The aim of the experiment was to compare the compatibility of scaffolds based on chitosan with gallic acid, ferulic acid, or tannic acid using the in vivo method. For this purpose, materials were implanted into rabbits in the middle of the latissimus dorsi muscle length. A scaffold based on unmodified chitosan was implanted by the same method as a control. Moreover, the Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) spectra and scanning electron microscope (SEM) observations were made to study the interactions between chitosan and phenolic acids. Additionally, antioxidant properties and blood compatibility were investigated. The results showed that all studied materials were safe and non-toxic. However, chitosan scaffolds modified by gallic acid and tannic acid were resorbed faster and, as a result, tissues were organized faster than those modified by ferulic acid or unmodified.

Extracellular matrix stiffness-The central cue for skin fibrosis

Skin fibrosis is a physiopathological process featuring the excessive deposition of extracellular matrix (ECM), which is the main architecture that provides structural support and constitutes the microenvironment for various cellular behaviors. Recently, increasing interest has been drawn to the relationship between the mechanical properties of the ECM and the initiation and modulation of skin fibrosis, with the engagement of a complex network of signaling pathways, the activation of mechanosensitive proteins, and changes in immunoregulation and metabolism. Simultaneous with the progression of skin fibrosis, the stiffness of ECM increases, which in turn perturbs mechanical and humoral homeostasis to drive cell fate toward an outcome that maintains and enhances the fibrosis process, thus forming a pro-fibrotic "positive feedback loop". In this review, we highlighted the central role of the ECM and its dynamic changes at both the molecular and cellular levels in skin fibrosis. We paid special attention to signaling pathways regulated by mechanical cues in ECM remodeling. We also systematically summarized antifibrotic interventions targeting the ECM, hopefully enlightening new strategies for fibrotic diseases.

Poly(l-lactic acid) Scaffold Releasing an α4β1 Integrin Agonist Promotes Nonfibrotic Skin Wound Healing in Diabetic Mice

Skin wound healing is a highly complex process that continues to represent a major medical problem, due to chronic nonhealing wounds in several classes of patients and to possible fibrotic complications, which compromise the function of the dermis. Integrins are transmembrane receptors that play key roles in this process and that offer a recognized druggable target. Our group recently synthesized GM18, a specific agonist for α4β1, an integrin that plays a role in skin immunity and in the migration of neutrophils, also regulating the differentiated state of fibroblasts. GM18 can be combined with poly(l-lactic acid) (PLLA) nanofibers to provide a controlled release of this agonist, resulting in a medication particularly suitable for skin wounds. In this study, we first optimized a GM18-PLLA nanofiber combination with a 7-day sustained release for use as skin wound medication. When tested in an experimental pressure ulcer in diabetic mice, a model for chronic nonhealing wounds, both soluble and GM18-PLLA formulations accelerated wound healing, as well as regulated extracellular matrix synthesis toward a nonfibrotic molecular signature. In vitro experiments using the adhesion test showed fibroblasts to be a principal GM18 cellular target, which we then used as an in vitro model to explore possible mechanisms of GM18 action. Our results suggest that the observed antifibrotic behavior of GM18 may exert a dual action on fibroblasts at the α4β1 binding site and that GM18 may prevent profibrotic EDA-fibronectin-α4β1 binding and activate outside-in signaling of the ERK1/2 pathways, a critical component of the wound healing process.

Increased Expression of Galectin-3 in Skin Fibrosis: Evidence from In Vitro and In Vivo Studies

Skin fibrosis is a hallmark of a wide array of dermatological diseases which can greatly impact the patients' quality of life. Galectin-3 (GAL-3) has emerged as a central regulator of tissue fibrosis, playing an important pro-fibrotic role in numerous organs. Various studies are highlighting its importance as a skin fibrotic diseases biomarker; however, there is a need for further studies that clarify its role. This paper aims to ascertain whether the expression of GAL-3 is increased in relevant in vitro and in vivo models of skin fibrosis. We studied the role of GAL-3 in vitro using normal human dermal fibroblasts (NHDF) and fibrocytes. In addition, we used a skin fibrosis murine model (BALB/c mice) and human biopsies of healthy or keloid tissue. GAL-3 expression was analyzed using real time PCR, Western blot and immunostaining techniques. We report a significantly increased expression of GAL-3 in NHDF and fibrocytes cell cultures following stimulation with transforming growth factor β1 (TGFβ1). In vivo, GAL-3 expression was increased in a murine model of systemic sclerosis and in human keloid biopsies. In sum, this study underlines the involvement of GAL-3 in skin fibrosis using several models of the disease and highlights its role as a relevant target.

Identification and validation of key immune-related genes with promising diagnostic and predictive value in systemic sclerosis

AIMS

To screen and confirm key immune-related genes (IRGs) with diagnostic and predictive value in systemic sclerosis (SSc) and provide potential therapeutic targets for patients with SSc.

MATERIALS AND METHODS

In Gene Expression Omnibus database (GEO), four datasets of gene expression profiling related to SSc were downloaded and used for the analysis in this study. After differential analysis of SSc cases and controls in GSE130955, the differentially expressed genes (DEGs) were overlapped with IRGs to obtain the immune-related differentially expressed genes (IR-DEGs) in SSc. In addition, functional annotation and pathway enrichment of IR-DEGs were conducted. The protein-protein interaction network (PPI) was constructed to identify key IR-DEGs. Using GSE58095, GSE181549 and GSE130953, the diagnostic and predictive abilities for the key IR-DEGs in SSc were validated. Finally, the screened key genes were confirmed in skin derived bleomycin (BLM)-induced SSc mice by Real-time PCR.

KEY FINDINGS

NGFR, TNFSF13B, FCER1G, GIMAP5, TYROBP and CSF1R may have important or very high diagnostic value for SSc. TYROBP and TNFSF13B had moderate and mild predictive value respectively in SSc patients after treatment. Real-time PCR assay further confirmed that the expressions of Ngfr, Tyrobp, Csf1r, Fcer1g and Gimap5 were significantly higher in skin of BLM-induced SSc mice than that in controls.

SIGNIFICANCE

The key IR-DEGs, including NGFR, TNFSF13B, TYROBP, CSF1R, FCER1G and GIMAP5, may become auxiliary diagnostic indicators and potential biomarkers for SSc. Moreover, TNFSF13B and TYROBP could have good prospects as predictive indicators in SSc patients that accepted cyclophosphamide or transplantation therapy.

Synergistic effect of Aloe vera flower and Aloe gel on cutaneous wound healing targeting MFAP4 and its associated signaling pathway: In-vitro study

ETHNOPHARMACOLOGICAL RELEVANCE

Aloe vera (L.) Burm. f. (Liliaceae family) is a well-known traditional medicinal plant, that has been used to treat a variety of illnesses, for decades ranging from cancer to skin disorders including wounds. It has been included in the traditional and herbal healthcare systems of many cultures around the world, as well as the pharmacopeia of different countries. Several in vitro and in vivo studies have also confirmed its potential antioxidant, anti-inflammatory, and wound-healing activities, etc. in the consistency of its historical and traditional uses. However, most studies to date are based on the A. vera gel and latex including its wound-healing effects. Very few studies have been focused on its flower, and rarely with its effects on cutaneous wound healing and its molecular mechanism.

AIM OF THE STUDY

To the best of our knowledge, this is the first study to report on the synergistic effect of the A. vera flower (AVF) and Aloe gel (PAG) on cutaneous wound-healing, as well as revealing its molecular mechanism targeting microfibril-associated glycoprotein 4 (MFAP4) and its associated signaling pathway.

METHODS

To investigate the synergistic effect of A. vera flower and Aloe gel in cutaneous wound healing, cell viability, and cell migration, as well proliferation assay was performed. This was followed by quantitative real-time polymerase chain reaction and Western blot analyses in wounded conditions to check the effects of this mixture on protein and mRNA levels in normal human dermal fibroblast (NHDF) cells. Moreover, small interfering RNA (siRNA) -mediated knockdown of MFAP4 in NHDF cells was performed followed by migration assay and cell cycle analysis, to confirm its role in cutaneous wound healing. Additionally, HaCaT cells were included in this study to evaluate its migratory and anti-inflammatory effects.

RESULTS

Based on our obtained results, the PAG and AVF mixture synergistically induced the proliferation, migration, and especially ECM formation of NHDF cells by enhancing the expression of MFAP4. Other extracellular components associated with MFAP4 signaling pathway, such as fibrillin, collagen, elastin, TGF β, and α-SMA, also increased at both the protein and mRNA levels. Subsequently, this mixture initiated the phosphorylation of the extracellular signal-regulated kinase (ERK) and AKT signaling pathways, and the S-phase of the cell cycle was also slightly modified. Also, the mixture induced the migration of HaCaT cells along with the suppression of inflammatory cytokines. Moreover, the siRNA-mediated knockdown highlighted the crucial role of MFAP4 in cutaneous wound healing in NHDF cells.

CONCLUSION

This study showed that the mixture of PAG and AVF has significant wound healing effects targeting MFAP4 and its associated signaling pathway. Additionally, MFAP4 was recognized as a new potential biomarker of wound healing, which can be confirmed by further in vivo studies.

Tetrahedral Framework Nucleic Acids Inhibit Skin Fibrosis via the Pyroptosis Pathway

The skin is the first line of defense for the human body and is vulnerable to injury. Various topical or systemic diseases facilitate skin inflammation, and when the intensity or duration of skin injury exceeds the ability of tissue repair, fibrosis, an outcome of a dysregulated tissue-repair response, begins to dominate the repair process. However, existing methods for reducing skin fibrosis are insufficient and cause side effects, highlighting the need for drugs that effectively inhibit skin fibrosis and reduce immunogenicity, inflammation, apoptosis, and pyroptosis. Tetrahedral framework nucleic acids (tFNAs) are DNA nanomaterials that have a unique spatial structure, demonstrate excellent biosecurity, and promote anti-inflammatory, antioxidative, antifibrotic, angiogenic, and skin-wound-healing activities with almost no toxicity. Here, we explored the potential of tFNAs in skin fibrosis therapy in vitro and in vivo. After incubating cells or injecting mice with profibrogenic molecules and tFNAs, we found that the tFNAs inhibited the epithelial-mesenchymal transition, reduced inflammatory factor levels, decreased skin collagen content, and inhibited the pyroptosis pathway. These findings suggest the potential of tFNAs in treating pyroptosis-related diseases.

Self-Assembled Human Skin Equivalents Model Macrophage Activation of Cutaneous Fibrogenesis in Systemic Sclerosis

OBJECTIVE

The development of precision therapeutics for systemic sclerosis (SSc) has been hindered by the lack of models that accurately mimic the disease in vitro. This study was undertaken to design and test a self-assembled skin equivalent (saSE) system that recapitulates the cross-talk between macrophages and fibroblasts in cutaneous fibrosis.

METHODS

SSc-derived dermal fibroblasts (SScDFs) and normal dermal fibroblasts (NDFs) were cultured with CD14+ monocytes from SSc patients or healthy controls to allow de novo stroma formation. Monocyte donor-matched plasma was introduced at week 3 prior to seeding keratinocytes to produce saSE with a stratified epithelium. Tissue was characterized by immunohistochemical staining, atomic force microscopy, enzyme-linked immunosorbent assay, and quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Stroma synthesized de novo from NDFs and SScDFs supported a fully stratified epithelium to form saSE. A thicker and stiffer dermis was generated by saSE with SScDFs, and more interleukin-6 and transforming growth factor β (TGFβ) was secreted by saSE with SScDFs compared to saSE with NDFs, regardless of the inclusion of monocytes. Tissue with SSc monocytes and plasma had amplified dermal thickness and stiffness relative to control tissue. Viable CD163+ macrophages were found within the stroma of saSE 5 weeks after seeding. Additionally, SSc saSE contained greater numbers of CD163+ and CD206+ macrophages compared to control saSE. TGFβ blockade inhibited stromal stiffness to a greater extent in SSc saSE compared to control saSE.

CONCLUSION

These data suggest reciprocal activation between macrophages and fibroblasts that increases tissue thickness and stiffness, which is dependent in part on TGFβ activation. The saSE system may serve as a platform for preclinical therapeutic testing and for molecular characterization of SSc skin pathology through recapitulation of the interactions between macrophages and fibroblasts.

Inhibition of PDE4 by apremilast attenuates skin fibrosis through directly suppressing activation of M1 and T cells

Systemic sclerosis (SSc) is a life-threatening chronic connective tissue disease with the characteristics of skin fibrosis, vascular injury, and inflammatory infiltrations. Though inhibition of phosphodiesterase 4 (PDE4) has been turned out to be an effective strategy in suppressing inflammation through promoting the accumulation of intracellular cyclic adenosine monophosphate (cAMP), little is known about the functional modes of inhibiting PDE4 by apremilast on the process of SSc. The present research aimed to investigate the therapeutic effects and underlying mechanism of apremilast on SSc. Herein, we found that apremilast could markedly ameliorate the pathological manifestations of SSc, including skin dermal thickness, deposition of collagens, and increased expression of α-SMA. Further study demonstrated that apremilast suppressed the recruitment and activation of macrophages and T cells, along with the secretion of inflammatory cytokines, which accounted for the effects of apremilast on modulating the pro-fibrotic processes. Interestingly, apremilast could dose-dependently inhibit the activation of M1 and T cells in vitro through promoting the phosphorylation of CREB. In summary, our research suggested that inhibiting PDE4 by apremilast might provide a novel therapeutic option for clinical treatment of SSc patients.

SB203580-A Potent p38 MAPK Inhibitor Reduces the Profibrotic Bronchial Fibroblasts Transition Associated with Asthma

Subepithelial fibrosis is a component of the remodeling observed in the bronchial wall of patients diagnosed with asthma. In this process, human bronchial fibroblasts (HBFs) drive the fibroblast-to-myofibroblast transition (FMT) in response to transforming growth factor-β₁ (TGF-β₁), which activates the canonical Smad-dependent signaling. However, the pleiotropic properties of TGF-β₁ also promote the activation of non-canonical signaling pathways which can affect the FMT. In this study we investigated the effect of p38 mitogen-activated protein kinase (MAPK) inhibition by SB203580 on the FMT potential of HBFs derived from asthmatic patients using immunocytofluorescence, real-time PCR and Western blotting methods. Our results demonstrate for the first time the strong effect of p38 MAPK inhibition on the TGF-β₁-induced FMT potential throughout the strong attenuation of myofibroblast-related markers: α-smooth muscle actin (α-SMA), collagen I, fibronectin and connexin 43 in HBFs. We suggest the pleiotropic mechanism of SB203580 on FMT impairment in HBF populations by the diminishing of TGF-β/Smad signaling activation and disturbances in the actin cytoskeleton architecture along with the maturation of focal adhesion sites. These observations justify future research on the role of p38 kinase in FMT efficiency and bronchial wall remodeling in asthma.

Systemic mesalazine treatment prevents spontaneous skin fibrosis in PLK2-deficient mice

Skin fibrosis is a complex biological remodeling process occurring in disease like systemic sclerosis, morphea, or eosinophilic fasciitis. Since the knowledge about the underlying pathomechanisms is still incomplete, there is currently no therapy, which prevents or reverses skin fibrosis sufficiently. The present study investigates the role of polo-like kinase 2 (PLK2) and the pro-fibrotic cytokine osteopontin (OPN) in the pathogenesis of cutaneous fibrosis and demonstrates the antifibrotic effects of systemic mesalazine treatment in vivo. Isolated primary dermal fibroblasts of PLK2 wild-type (WT) and knockout (KO) mice were characterized invitro. Skin thickness and histoarchitecture were studied in paraffin-embedded skin sections. The effects of mesalazine treatment were examined in isolated fibroblasts and PLK2 KO mice, which were fed 100 µg/g mesalazine for 6 months via the drinking water. Compared to WT, PLK2 KO fibroblasts displayed higher spontaneous myofibroblast differentiation, reduced proliferation rates, and overexpression of the fibrotic cytokine OPN. Invitro, 72 h of treatment with 10 mmol/L mesalazine induced phenotype conversion in PLK2 KO fibroblasts and attenuated OPN expression by inhibiting ERK1/2. In vivo, dermal myofibroblast differentiation, collagen accumulation, and skin thickening were prevented by mesalazine in PLK2 KO. Plasma creatinine levels indicated good tolerability of systemic long-term mesalazine treatment. The current study reveals a spontaneous fibrotic skin phenotype and ERK1/2-dependent OPN overexpression in PLK2 KO mice. We provide experimental evidence for the antifibrotic effectiveness of systemic mesalazine treatment to prevent fibrosis of the skin, suggesting further investigation in experimental and clinical settings.

Animal and Human Models of Tissue Repair and Fibrosis: An Introduction

Reductionist cell culture systems are not only convenient but essential to understand molecular mechanisms of myofibroblast activation and action in carefully controlled conditions. However, tissue myofibroblasts do not act in isolation and the complexity of tissue repair and fibrosis in humans cannot be captured even by the most elaborate culture models. Over the past five decades, numerous animal models have been developed to study different aspects of myofibroblast biology and interactions with other cells and extracellular matrix. The underlying principles can be broadly classified into: (1) organ injury by trauma such as prototypical full thickness skin wounds or burns; (2) mechanical challenges, such as pressure overload of the heart by ligature of the aorta or the pulmonary vein; (3) toxic injury, such as administration of bleomycin to lungs and carbon tetrachloride to the liver; (4) organ infection with viruses, bacteria, and parasites, such as nematode infections of liver; (5) cytokine and inflammatory models, including local delivery or viral overexpression of active transforming growth factor beta; (6) "lifestyle" and metabolic models such as high-fat diet; and (7) various genetic models. We will briefly summarize the most widely used mouse models used to study myofibroblasts in tissue repair and fibrosis as well as genetic tools for manipulating myofibroblast repair functions in vivo.

Validation strategies for identifying drug targets in dermal fibrotic disorders

Fibrotic skin disorders, such as keloid disease (KD), are common clinically challenging disorders with unknown etiopathogenesis and ill-defined treatment strategies that affect millions of people worldwide. Thus, there is an urgent need to discover novel therapeutics. The validation of potential drug targets is an obligatory step in discovering and developing new therapeutic agents for the successful treatment of dermal fibrotic conditions, such as KD. The integration of multi-omics data with traditional and modern technological approaches, such as RNA interference (RNAi) and genome-editing tools, would provide unique opportunities to identify and validate novel targets in KD during early drug development. Thus, in this review, we summarize the current and emerging drug discovery process with a focus on validation strategies of potential drug targets identified in dermal fibrosis.

Single-cell RNA-seq reveals fibroblast heterogeneity and increased mesenchymal fibroblasts in human fibrotic skin diseases

Fibrotic skin disease represents a major global healthcare burden, characterized by fibroblast hyperproliferation and excessive accumulation of extracellular matrix. Fibroblasts are found to be heterogeneous in multiple fibrotic diseases, but fibroblast heterogeneity in fibrotic skin diseases is not well characterized. In this study, we explore fibroblast heterogeneity in keloid, a paradigm of fibrotic skin diseases, by using single-cell RNA-seq. Our results indicate that keloid fibroblasts can be divided into 4 subpopulations: secretory-papillary, secretory-reticular, mesenchymal and pro-inflammatory. Interestingly, the percentage of mesenchymal fibroblast subpopulation is significantly increased in keloid compared to normal scar. Functional studies indicate that mesenchymal fibroblasts are crucial for collagen overexpression in keloid. Increased mesenchymal fibroblast subpopulation is also found in another fibrotic skin disease, scleroderma, suggesting this is a broad mechanism for skin fibrosis. These findings will help us better understand skin fibrotic pathogenesis, and provide potential targets for fibrotic disease therapies.

Notch-ing up knowledge on molecular mechanisms of skin fibrosis: focus on the multifaceted Notch signalling pathway

Fibrosis can be defined as an excessive and deregulated deposition of extracellular matrix proteins, causing loss of physiological architecture and dysfunction of different tissues and organs. In the skin, fibrosis represents the hallmark of several acquired (e.g. systemic sclerosis and hypertrophic scars) and inherited (i.e. dystrophic epidermolysis bullosa) diseases. A complex series of interactions among a variety of cellular types and a wide range of molecular players drive the fibrogenic process, often in a context-dependent manner. However, the pathogenetic mechanisms leading to skin fibrosis are not completely elucidated. In this scenario, an increasing body of evidence has recently disclosed the involvement of Notch signalling cascade in fibrosis of the skin and other organs. Despite its apparent simplicity, Notch represents one of the most multifaceted, strictly regulated and intricate pathways with still unknown features both in health and disease conditions. Starting from the most recent advances in Notch activation and regulation, this review focuses on the pro-fibrotic function of Notch pathway in fibroproliferative skin disorders describing molecular networks, interplay with other pro-fibrotic molecules and pathways, including the transforming growth factor-β1, and therapeutic strategies under development.

Transcriptome analysis of human dermal fibroblasts following red light phototherapy

Fibrosis occurs when collagen deposition and fibroblast proliferation replace healthy tissue. Red light (RL) may improve skin fibrosis via photobiomodulation, the process by which photosensitive chromophores in cells absorb visible or near-infrared light and undergo photophysical reactions. Our previous research demonstrated that high fluence RL reduces fibroblast proliferation, collagen deposition, and migration. Despite the identification of several cellular mechanisms underpinning RL phototherapy, little is known about the transcriptional changes that lead to anti-fibrotic cellular responses. Herein, RNA sequencing was performed on human dermal fibroblasts treated with RL phototherapy. Pathway enrichment and transcription factor analysis revealed regulation of extracellular matrices, proliferation, and cellular responses to oxygen-containing compounds following RL phototherapy. Specifically, RL phototherapy increased the expression of MMP1, which codes for matrix metalloproteinase-1 (MMP-1) and is responsible for remodeling extracellular collagen. Differential regulation of MMP1 was confirmed with RT-qPCR and ELISA. Additionally, RL upregulated PRSS35, which has not been previously associated with skin activity, but has known anti-fibrotic functions. Our results suggest that RL may benefit patients by altering fibrotic gene expression.

Transgenerational supplementation with eicosapentaenoic acid reduced the metabolic consequences on the whole body and skeletal muscle in mice receiving an obesogenic diet

PURPOSE

The effect of manipulating the fatty acid profile of the diet over generations could affect the susceptibility to develop obesity and metabolic disorders. Although some acute effects were described, the impact of transgenerational continuous supplementation with omega 3 fatty acids on metabolic homeostasis and skeletal muscle metabolic flexibility during a nutritional stress is unknown.

METHODS

We analyzed the effect of an obesogenic diet in mice after transgenerational supplementation with an omega-3 rich oil (mainly EPA) or a control oil. Young F3 animals received a high fat and high sucrose diet for 4 months. Whole-body biometric data were recorded and lipidomic/transcriptomic adaptations were explored in the skeletal muscle.

RESULTS

F3 mice from the lineage supplemented with EPA gained less weight, fat mass, and exhibited better metabolic parameters after the obesogenic diet compared to mice from the control lineage. Transcriptomic exploration of skeletal muscle showed differential regulation of biological processes such as fibrosis, fatty acid catabolism, and inflammation between lineages. These adaptations were associated to subtle lipid remodeling of cellular membranes with an enrichment in phospholipids with omega 3 fatty acid in mice from the EPA lineage.

CONCLUSION

Transgenerational and continuous intake of EPA could help to reduce cardiovascular and metabolic risks related to an unbalanced diet by the modulation of insulin sensitivity, fatty acid metabolism, and fibrosis in skeletal muscle.

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.

3D bioprinting dermal-like structures using species-specific ulvan

3D cellularized structures revealing dermal-like properties have been successfully printed using bioinks based on the sulfated polysaccharide ulvan from Australian green seaweed.

Targeting the α7 nicotinic acetylcholine receptor-A novel road towards the future treatment of skin diseases

Nicotinic acetylcholine receptors (nAChRs) are members of the superfamily of neurotransmitter-gated ion channels. The natural ligand for nAChRs is the endogenous neurotransmitter acetylcholine. Among the nAChRs is the α7nAChR. It is not only expressed by neural tissues but also in the skin. A number of different resident cutaneous cell types including epidermal keratinocytes, sebocytes and dermal fibroblasts express functional α7nAChR. Moreover, cells of the immune system such as lymphocytes, macrophages and monocytes, playing an important role in skin homeostasis, also express α7nAChR. Translational research focusing on the exploitation of the α7nAChR in dermatology has revealed that this neuroendocrine receptor could be promising target for the treatment of inflammatory skin diseases. For example, α7nAChR agonists can counteract transforming growth factor-β1-mediated responses in dermal fibroblasts, key effector cells in scleroderma. In accordance with this α7nAChR, agonists are effective in both inflammation and non-inflammation-driven models of experimentally induced skin fibrosis. Moreover, α7nAChR agonists can modulate expression of proinflammatory cytokines in epidermal keratinocytes that are crucially involved in the pathogenesis of psoriasis and other inflammatory skin diseases. Finally, the capability of α7nAChR agonists to suppress ultraviolet light A/B-induced responses, for example production of proinflammatory cytokines and oxidative stress, the latter crucially involved in dermal photoageing, points to a potential of such agents in the prevention of extrinsic skin ageing. Therefore, emphasis on translational research targeting the α7nAChR in skin may lead to the development of new treatment and prevention modalities against fibrosclerotic skin diseases, psoriasis vulgaris, atopic dermatitis, acne, photodermatoses and extrinsic skin ageing.

A Comparative Study of Engineered Dermal Templates for Skin Wound Repair in a Mouse Model

Engineered dermal templates have revolutionised the repair and reconstruction of skin defects. Their interaction with the wound microenvironment and linked molecular mediators of wound repair is still not clear. This study investigated the wound bed and acellular "off the shelf" dermal template interaction in a mouse model. Full-thickness wounds in nude mice were grafted with allogenic skin, and either collagen-based or fully synthetic dermal templates. Changes in the wound bed showed significantly higher vascularisation and fibroblast infiltration in synthetic grafts when compared to collagen-based grafts (P ≤ 0.05). Greater tissue growth was associated with higher prostaglandin-endoperoxide synthase 2 (Ptgs2) RNA and cyclooxygenase-2 (COX-2) protein levels in fully synthetic grafts. Collagen-based grafts had higher levels of collagen III and matrix metallopeptidase 2. To compare the capacity to form a double layer skin substitute, both templates were seeded with human fibroblasts and keratinocytes (so-called human skin equivalent or HSE). Mice were grafted with HSEs to test permanent wound closure with no further treatment required. We found the synthetic dermal template to have a significantly greater capacity to support human epidermal cells. In conclusion, the synthetic template showed advantages over the collagen-based template in a short-term mouse model of wound repair.

Activin A-Mediated Regulation of XT-I in Human Skin Fibroblasts

Fibrosis is a fundamental feature of systemic sclerosis (SSc) and is characterized by excessive accumulation of extracellular matrix components like proteoglycans (PG) or collagens in skin and internal organs. Serum analysis from SSc patients showed an increase in the enzyme activity of xylosyltransferase (XT), the initial enzyme in PG biosynthesis. There are two distinct XT isoforms-XT-I and XT-II-in humans, but until now only XT-I is associated with fibrotic remodelling for an unknown reason. The aim of this study was to identify new XT mediators and clarify the underlying mechanisms, in view of developing putative therapeutic anti-fibrotic interventions in the future. Therefore, we used different cytokines and growth factors, small molecule inhibitors as well as small interfering RNAs, and assessed the cellular XT activity and XYLT1 expression in primary human dermal fibroblasts by radiochemical activity assays and qRT-PCR. We identified a new function of activin A as a regulator of XYLT1 mRNA expression and XT activity. While the activin A-induced XT-I increase was found to be mediated by activin A receptor type 1B, MAPK and Smad pathways, the activin A treatment did not alter the XYLT2 expression. Furthermore, we observed a reciprocal regulation of XYLT1 and XYLT2 transcription after inhibition of the activin A pathway components. These results improve the understanding of the differential expression regulation of XYLT isoforms under pathological fibroproliferative conditions.

Bioengineered 3D Models to Recapitulate Tissue Fibrosis

Fibrosis, characterized by progressive tissue stiffening resulting in organ failure, is a growing health problem affecting millions of people worldwide. Currently, therapeutic options for tissue fibrosis are severely limited and organ transplantation is the only effective treatment for the end-stage fibrotic diseases with inherent limitations. Recent advancements in engineered 3D in vitro human disease mimic models, recapitulating the tissue pathophysiology, have provided unique state-of-the-art platforms for: (i) understanding the biological mechanisms involved in the disease pathogenesis; and (ii) high-throughput and reproducible drug screening. This review focuses on the recent multidisciplinary developments made towards advanced 3D biomimetic fibrotic tissue (liver, kidney, and lung) models that combine highly precision manufacturing techniques with high cellular functionality and biophysical (mechanical) properties.

Patch repair of deep wounds by mobilized fascia

Mammals form scars to quickly seal wounds and ensure survival by an incompletely understood mechanism^1-5. Here we show that skin scars originate from prefabricated matrix in the subcutaneous fascia. Fate mapping and live imaging revealed that fascia fibroblasts rise to the skin surface after wounding, dragging their surrounding extracellular jelly-like matrix, including embedded blood vessels, macrophages and peripheral nerves, to form the provisional matrix. Genetic ablation of fascia fibroblasts prevented matrix from homing into wounds and resulted in defective scars, whereas placing an impermeable film beneath the skin-preventing fascia fibroblasts from migrating upwards-led to chronic open wounds. Thus, fascia contains a specialized prefabricated kit of sentry fibroblasts, embedded within a movable sealant, that preassemble together diverse cell types and matrix components needed to heal wounds. Our findings suggest that chronic and excessive skin wounds may be attributed to the mobility of the fascia matrix.

Ointment of Ximenes americana promotes acceleration of wound healing in rats1

Purpose

To evaluate the healing potential of the Ximenia americana hydroalcoholic extract in 10% cream in excisional wound models in rats.

Methods

Sixty male adults Wistar rats were submitted to skin and subcutaneous tissue surgery in the right and left thoracic regions, divided into three experimental groups: Standard submitted to treatment with only the base vehicle, Treated wounds treated with hydroalcoholic extract of X. americana applied on 10%, Lanette base and Control, untreated wounds. The treatment was performed daily and the wounds evaluated microscopically by the quantification of fibroblasts, collagen fibers and blood vessels.

Results

The histomorphometric analysis showed a significant increase in the number of fibroblasts, collagen fibers and blood vessels in the treated group.

Conclusion

The topical action of the cream based on Ximenia americana shows angiogenic effects and improves the replacement of collagen, suggesting its use for the development of herbal remedy in the treatment of cutaneous wound healing.

Nimbolide ameliorates fibrosis and inflammation in experimental murine model of bleomycin-induced scleroderma

BACKGROUND

Clinical manifestations of skin fibrosis are very variable and ambiguous, making its management quite critical and challenging. The lack of appropriate established pharmacological interventions make its treatment even more complicated. Intricate details of the underlying pathogenesis are thus imperative to further explore different treatment possibilities. Of note, the TGF-β/Smad signaling axis and epithelial to mesenchymal transition (EMT) are the principal offenders in this fibrotic disorder.

OBJECTIVE

Our current study is aimed at demonstrating the antifibrotic and anti-inflammatory potential of nimbolide, a triterpene derived from Indian traditional plant neem, in a murine model of Bleomycin-induced scleroderma.

METHODS

Male C57BL/6 mice were administered with Bleomycin injections subcutaneously, daily for 28 days, at a constant site on the dorsum of the mice. Treatment with nimbolide lasted from day 1 to day 28. At the time of study termination, the injected sites were collected and stored suitably to conduct further molecular experiments and protein expression studies.

RESULTS AND CONCLUSION

The results of our study show that nimbolide can significantly intervene in the TGF-β/Smad signaling axis and the consequent EMT process, thus attenuating deposition of extracellular matrix. Nimbolide also profoundly caused the regression of established inflammation-driven fibrosis, thus demonstrating both antifibrotic and anti-inflammatory activities. Another commendable finding of this study is that nimbolide was able to decrease the levels of LOXL2, a collagen cross-linker, which is aberrantly expressed in scleroderma. Although further mechanistic studies are required, our study displays nimbolide for the first time as a potent antifibrotic agent which can be used as a pharmacological intervention for the treatment of scleroderma.