c-Abl silencing reduced the inhibitory effects of TGF-β1 on apoptosis in systemic sclerosis dermal fibroblasts

The c-Abl-RACK1-FAK signaling axis promotes renal fibrosis in mice through regulating fibroblast-myofibroblast transition

BACKGROUND

Renal fibrosis is a prevalent manifestation of chronic kidney disease (CKD), and effective treatments for this disease are currently lacking. Myofibroblasts, which originate from interstitial fibroblasts, aggregate in the renal interstitium, leading to significant accumulation of extracellular matrix and impairment of renal function. The nonreceptor tyrosine kinase c-Abl (encoded by the Abl1 gene) has been implicated in the development of renal fibrosis. However, the precise role of c-Abl in this process and its involvement in fibroblast-myofibroblast transition (FMT) remain poorly understood.

METHODS

To investigate the effect of c-Abl in FMT during renal fibrosis, we investigated the expression of c-Abl in fibrotic renal tissues of patients with CKD and mouse models. We studied the phenotypic changes in fibroblast or myofibroblast-specific c-Abl conditional knockout mice. We explored the potential targets of c-Abl in NRK-49F fibroblasts.

RESULTS

In this study, fibrotic mouse and cell models demonstrated that c-Abl deficiency in fibroblasts mitigated fibrosis by suppressing fibroblast activation, fibroblast-myofibroblast transition, and extracellular matrix deposition. Mechanistically, c-Abl maintains the stability of the RACK1 protein, which serves as a scaffold for proteins such as c-Abl and focal adhesion kinase at focal adhesions, driving fibroblast activation and differentiation during renal fibrosis. Moreover, specifically targeting c-Abl deletion in renal myofibroblasts could prove beneficial in established kidney fibrosis by reducing RACK1 expression and diminishing the extent of fibrosis.

CONCLUSIONS

Our findings suggest that c-Abl plays a pathogenic role in interstitial fibrosis through the regulation of RACK1 protein stabilization and myofibroblast differentiation, suggesting a promising strategy for the treatment of CKD.

Drug development and novel therapeutics to ensure a personalized approach in the treatment of systemic sclerosis

INTRODUCTION

Systemic sclerosis (SSc) is a systemic disease encompassing autoimmunity, vasculopathy, and fibrosis. SSc is still burdened by high mortality and morbidity rates. Recent advances in understanding the pathogenesis of SSc have identified novel potential therapeutic targets. Several clinical trials have been subsequently designed to evaluate the efficacy of a number of new drugs. The aim of this review is to provide clinicians with useful information about these novel molecules.

AREA COVERED

In this narrative review, we summarize the available evidence regarding the most promising targeted therapies currently under investigation for the treatment of SSc. These medications include kinase inhibitors, B-cell depleting agents, and interleukin inhibitors.

EXPERT OPINION

Over the next five years, several new, targeted drugs will be introduced in clinical practice for the treatment of SSc. Such pharmacological agents will expand the existing pharmacopoeia and enable a more personalized and effective approach to patients with SSc. Thus, it will not only possible to target a specific disease domain, but also different stages of the disease.

Myofibroblast fate plasticity in tissue repair and fibrosis: Deactivation, apoptosis, senescence and reprogramming

In response to tissue injury, fibroblasts differentiate into professional repair cells called myofibroblasts, which orchestrate many aspects of the normal tissue repair programme including synthesis, deposition and contraction of extracellular matrix proteins, leading to wound closure. Successful tissue repair responses involve termination of myofibroblast activities in order to prevent pathologic fibrotic scarring. Here, we discuss the cellular and molecular mechanisms limiting myofibroblast activities during physiological tissue repair, including myofibroblast deactivation, apoptosis, reprogramming and immune clearance of senescent myofibroblasts. In addition, we summarize pathological mechanisms leading to myofibroblast persistence and survival, a hallmark of fibrotic diseases. Finally, we discuss emerging anti-fibrotic therapies aimed at targeting myofibroblast fate such as senolytics, gene therapy, cellular immunotherapy and CAR-T cells.

The Role of Pro-fibrotic Myofibroblasts in Systemic Sclerosis: from Origin to Therapeutic Targeting

Systemic sclerosis (SSc, scleroderma) is a complex connective tissue disorder characterized by multisystem clinical manifestations resulting from immune dysregulation/autoimmunity, vasculopathy and, most notably, progressive fibrosis of the skin and internal organs. In recent years, it has emerged that the main drivers of SSc-related tissue fibrosis are myofibroblasts, a type of mesenchymal cells with both the extracellular matrix-synthesizing features of fibroblasts and the cytoskeletal characteristics of contractile smooth muscle cells. The accumulation and persistent activation of pro-fibrotic myofibroblasts during SSc development and progression result into elevated mechanical stress and reduced matrix plasticity within the affected tissues and may be ascribed to a reduced susceptibility of these cells to pro-apoptotic stimuli, as well as their increased formation from tissue-resident fibroblasts or transition from different cell types. Given the crucial role of myofibroblasts in SSc pathogenesis, finding the way to inhibit myofibroblast differentiation and accumulation by targeting their formation, function and survival may represent an effective approach to hamper the fibrotic process or even halt or reverse established fibrosis. In this review, we discuss the role of myofibroblasts in SSc-related fibrosis, with a special focus on their cellular origin and the signaling pathways implicated in their formation and persistent activation. Furthermore, we provide an overview of potential therapeutic strategies targeting myofibroblasts that may be able to counteract fibrosis in this pathological condition.

Myofibroblasts and Fibrosis: Mitochondrial and Metabolic Control of Cellular Differentiation

Cardiac fibrosis is mediated by the activation of resident cardiac fibroblasts, which differentiate into myofibroblasts in response to injury or stress. Although myofibroblast formation is a physiological response to acute injury, such as myocardial infarction, myofibroblast persistence, as occurs in heart failure, contributes to maladaptive remodeling and progressive functional decline. Although traditional pathways of activation, such as TGFβ (transforming growth factor β) and AngII (angiotensin II), have been well characterized, less understood are the alterations in mitochondrial function and cellular metabolism that are necessary to initiate and sustain myofibroblast formation and function. In this review, we highlight recent reports detailing the mitochondrial and metabolic mechanisms that contribute to myofibroblast differentiation, persistence, and function with the hope of identifying novel therapeutic targets to treat, and potentially reverse, tissue organ fibrosis.

Evasion of apoptosis by myofibroblasts: a hallmark of fibrotic diseases

Organ fibrosis is a lethal outcome of autoimmune rheumatic diseases such as systemic sclerosis. Myofibroblasts are scar-forming cells that are ultimately responsible for the excessive synthesis, deposition and remodelling of extracellular matrix proteins in fibrosis. Advances have been made in our understanding of the mechanisms that keep myofibroblasts in an activated state and control myofibroblast functions. However, the mechanisms that help myofibroblasts to persist in fibrotic tissues remain poorly understood. Myofibroblasts evade apoptosis by activating molecular mechanisms in response to pro-survival biomechanical and growth factor signals from the fibrotic microenvironment, which can ultimately lead to the acquisition of a senescent phenotype. Growing evidence suggests that myofibroblasts and senescent myofibroblasts, rather than being resistant to apoptosis, are actually primed for apoptosis owing to concomitant activation of cell death signalling pathways; these cells are poised to apoptose when survival pathways are inhibited. This knowledge of apoptotic priming has paved the way for new therapies that trigger apoptosis in myofibroblasts by blocking pro-survival mechanisms, target senescent myofibroblast for apoptosis or promote the reprogramming of myofibroblasts into scar-resolving cells. These novel strategies are not only poised to prevent progressive tissue scarring, but also have the potential to reverse established fibrosis and to regenerate chronically injured tissues.

Non-canonical (non-SMAD2/3) TGF-β signaling in fibrosis: Mechanisms and targets

Transforming growth factor (TGF)-β uses several intracellular signaling pathways besides canonical ALK5-Smad2/3 signaling to regulate a diverse array of cellular functions. Several of these so-called non-canonical (non-Smad2/3) pathways have been implicated in the pathogenesis of fibrosis and may therefore represent targets for therapeutic intervention. This review summarizes our current knowledge on the mechanisms of non-canonical TGF-β signaling in fibrosis, the potential molecular targets and the use of agonists/antagonists for therapeutic intervention.

Overexpression of apoptosis-related protein, survivin, in fibroblasts from patients with systemic sclerosis

BACKGROUND/OBJECTIVES

Recent studies suggest that, in addition to activation and hypersecretion of matrix components, fibroblasts from patients with systemic sclerosis (SSc) are resistant to apoptosis. Previous studies have shown that survivin, a member of inhibition of apoptosis (IAP) family, plays an important role in apoptosis resistance. Accordingly, we decided to study the expression of the most important members of IAP family in SSc fibroblasts, which can block apoptosis either by binding and inhibiting caspases or through caspase-independent mechanisms.

METHOD

Skin biopsy samples were obtained from 19 patients with diffuse cutaneous SSc (DcSSc) and 16 healthy controls. Dermal fibroblasts were cultured and the total RNA was isolated from cells followed by cDNA synthesis. Real-time PCR was performed using SYBR Green PCR master mix and specific primers for cIAP1, cIAP2, XIAP, and Survivin mRNA quantification.

RESULTS

A significantly increased expression level of Survivin was observed in fibroblasts from SSc patients compared to controls (2.26-fold, P = 0.04). However, mRNA expression of cIAP1, cIAP2, and XIAP did not change significantly between cases and controls.

CONCLUSIONS

Our results showed that survivin is upregulated in SSc skin fibroblast which may lead to resistance to apoptosis. Further studies should be performed to reveal the role of survivin in apoptosis pathway of SSc fibroblasts.

Attenuation of aquaporin-3 and epidermal growth factor receptor expression and activation in systemic sclerosis dermal fibroblasts

OBJECTIVES

Impaired wound healing and skin dehydration are the mainstay of systemic sclerosis (SSc) cutaneous manifestations. Aquaporin-3 (AQP3) has a pivotal role in skin hydration and wound healing. Epidermal growth factor receptor (EGFR) activation is impaired in SSc fibroblasts. It is unclear whether AQP3 downregulation or epidermal growth factor (EGF) signaling are the primary points of dysregulation in SSc patients.

METHODS

Skin punch biopsies were obtained from 10 SSc patients and 10 healthy subjects. The mRNA and/or protein expression levels of AQP3, EGFR/p-EGFR, matrix metalloproteinase-1/2/9 (MMP-1/2/9), and tissue inhibitors of metalloproteinase-1 (TIMP1) at baseline and after EGF and transforming growth factor-β1 (TGF-β1) treatment was evaluated in extracted fibroblasts using real-time polymerase chain reaction and western blot analysis.

RESULTS

SSc fibroblasts expressed lower AQP3 and EGFR, compared with normal fibroblasts. Normal fibroblasts increased AQP3 expression in response to EGF whereas AQP3 expression had no change in EGF-treated-SSc fibroblasts. Likewise, EGFR was activated in response to EGF in the normal group but not SSc group. Baseline expression of MMP-1/2/9 and TIMP1 was not different between SSc and controls. EGF treatment did not result in alteration of any MMPs expression in either of the groups. Combination treatment resulted in a significant upregulation of MMP-1 in normal fibroblasts compared with SSc fibroblasts, while in SSc fibroblasts MMP-9 expression was upregulated in response to treatment with TGF-β1 only.

CONCLUSION

Downregulation of AQP3 expression in SSc fibroblasts may be related to reduced EGFR expression and activation. TGF-β1 (alone or in combination with EGF) only can upregulate AQP3 expression in SSc fibroblasts so, TGF-β1 affect MMP-1 and MMP-9 just in SSc fibroblasts.

Unraveling SSc Pathophysiology; The Myofibroblast

Systemic sclerosis (SSc) is a severe auto-immune disease, characterized by vasculopathy and fibrosis of connective tissues. SSc has a high morbidity and mortality and unfortunately no disease modifying therapy is currently available. A key cell in the pathophysiology of SSc is the myofibroblast. Myofibroblasts are fibroblasts with contractile properties that produce a large amount of pro-fibrotic extracellular matrix molecules such as collagen type I. In this narrative review we will discuss the presence, formation, and role of myofibroblasts in SSc, and how these processes are stimulated and mediated by cells of the (innate) immune system such as mast cells and T helper 2 lymphocytes. Furthermore, current novel therapeutic approaches to target myofibroblasts will be highlighted for future perspective.

Evaluation of ITGB2 (CD18) and SELL (CD62L) genes expression and methylation of ITGB2 promoter region in patients with systemic sclerosis

Systemic sclerosis (SSc), an autoimmune disease of connective tissue, is characterized by inflammation, fibrosis, and vessel endothelial damage. Products of Integrin subunit beta 2 (ITGB2) and selectin L (SELL) genes participate in several functional pathways of immune system. The aim of this investigation was to survey the transcript level of ITGB2 and SELL genes as well as methylation status of CpG sites in promoter region of differently expressed gene in PBMCs of SSc patients. PBMCs were isolated from whole blood of 50 SSc patients and 30 healthy controls. Total RNA and DNA contents of PBMCs were extracted. Gene expression was analyzed by real-time PCR using the SYBR Green PCR Master Mix. To investigate the methylation status of CpG sites, DNA samples were treated by bisulfite, amplified through nested PCR, and sequenced through Sanger difficult sequencing method. ITGB2 gene in PBMCs of SSc patients was overexpressed significantly in comparison to healthy controls. However, no altered SELL expression was observed. Three CpG sites of 12, 13 and 14 were significantly hypomethylated in patients group, despite overall methylation status of ITGB2 gene promoter revealed no significant difference between study groups. There was no statistically significant correlation between methylation status of ITGB2 promoter and the gene expression in patients. Regarding to lack of correlation of increased expression of ITGB2 with its promoter hypomethylation in SSc patients, our study suggests that upregulation of ITGB2 in PBMCs from SSc patients is probably due to another mechanism other than methylation alteration.

Epigenetics and pathogenesis of systemic sclerosis; the ins and outs

The pathogenesis of many diseases is influenced by environmental factors which can affect human genome and be inherited from generation to generation. Adverse environmental stimuli are recognized through the epigenetic regulatory complex, leading to gene expression alteration, which in turn culminates in disease outcomes. Three epigenetic regulatory mechanisms modulate the manifestation of a gene, namely DNA methylation, histone changes, and microRNAs. Both epigenetics and genetics have been implicated in the pathogenesis of systemic sclerosis (SSc) disease. Genetic inheritance rate of SSc is low and the concordance rate in both monozygotic (MZ) and dizygotic (DZ) twins is little, implying other possible pathways in SSc pathogenesis scenario. Here, we provide an extensive overview of the studies regarding different epigenetic events which may offer insights into the pathology of SSc. Furthermore, epigenetic-based interventions to treat SSc patients were discussed.

Expressions of p53 and PUMA in fibroblasts of systemic sclerosis patients are normal at transcription level

BACKGROUND

Systemic sclerosis (SSc) fibroblasts show resistance apoptosis mechanisms, which enhances the fibrosis stage of the disease. Impaired function of p53 upregulated modulator of apoptosis (PUMA) has been related to deficits in p53-dependant apoptosis pathway. This study aimed to evaluate the transcriptional levels of p53 and PUMA mRNAs in fibroblasts from SSc patients and compare it with healthy individuals.

METHODS

In this case-control study, skin biopsy samples were obtained from 19 patients with diffuse cutaneous SSc (DcSSc) and 16 healthy controls. Afterward, dermal fibroblasts were isolated and cultured. After extraction of total RNA from cultured fibroblasts, complementary DNA (cDNA) was synthesized. mRNA quantification was carried out using real-time PCR, SYBR Green PCR master mix, and specific primers for p53 and PUMA.

RESULTS

No significant alteration was observed in mRNA expression levels of p53 and PUMA (P = .99 and .23, respectively) in fibroblasts from SSc patients compared with controls.

CONCLUSIONS

Apoptosis pathways are impaired in fibroblasts from patients with SSc, leading to chronic fibrosis. Nonetheless, PUMA/p53 pathway may not be involved in dysfunction of apoptosis mechanisms in fibroblasts of patients with SSc.

Inhibition of MicroRNA-21 induces apoptosis in dermal fibroblasts of patients with systemic sclerosis

BACKGROUND

Prolonged activation of dermal fibroblasts is the main cause of progressive fibrosis in systemic sclerosis (SSc). It seems that inhibition of apoptosis in SSc fibroblasts deregulates fibrosis. MicroRNA-21 (miR-21) is a pro-fibrotic factor with high expression in lesional areas of SSc skin and fibroblasts.

METHODS

The effects of miR-21 on expression of Bcl-2 and Bax, two apoptotic genes, in dermal fibroblasts of SSc patients were evaluated using real-time polymerase chain reaction and Western blot analysis. Apoptotic cells were detected using flow cytometry and Hoechst 33258 staining assays.

RESULTS

Overexpression of miR-21 using synthetic miR-21 RNA increased expression of Bcl-2, an inhibitor of apoptosis, and decreased the Bax : Bcl-2 expression ratio, a cell fate determinant, in SSc fibroblasts. Antisense inhibition of miR-21 induced a high rate of apoptosis in SSc fibroblasts. We propose that this may be associated with a decrease in Bcl-2 expression and a shift in the Bax : Bcl-2 ratio.

CONCLUSIONS

Although further studies are necessary to determine the underlying apoptotic pathway, we propose that inhibition of miR-21 in dermal fibroblasts from lesional skin may be useful in harnessing progressive fibrosis in SSc.

Investigating the potential of Shikonin as a novel hypertrophic scar treatment

Background

Hypertrophic scarring is a highly prevalent condition clinically and results from a decreased number of apoptotic fibroblasts and over-abundant production of collagen during scar formation following wound healing. Our previous studies indicated that Shikonin, an active component extracted from Radix Arnebiae, induces apoptosis and reduces collagen production in hypertrophic scar-derived fibroblasts. In the study reported here, we further evaluate the potential use of Shikonin as a novel scar remediation therapy by examining the effects of Shikonin on both keratinocytes and fibroblasts using Transwell® co-culture techniques. The underlying mechanisms were also revealed. In addition, effects of Shikonin on the expression of cytokines in Transwell co-culture “conditioned” medium were investigated.

Results

Our results indicate that Shikonin preferentially inhibits cell proliferation and induces apoptosis in fibroblasts without affecting keratinocyte function. In addition, we found that the proliferation-inhibiting and apoptosis-inducing abilities of SHI might be triggered via MAPK and Bcl-2/Caspase 3 signalling pathways. Furthermore, SHI has been found to attenuate the expression of TGF-β1 in Transwell co-cultured “conditioned” medium.

Conclusions

The data generated from this study provides further evidence that supports the potential use of Shikonin as a novel scar remediation therapy.