CCN2 and CCN5 exerts opposing effect on fibroblast proliferation and transdifferentiation induced by TGF-β

The matricellular protein CCN5 prevents anti-VEGF drug-induced epithelial-mesenchymal transition of retinal pigment epithelium

Age-related macular degeneration (AMD) is one of the major causes of blindness in the elderly worldwide. Anti-vascular endothelial growth factor (VEGF) drugs have been widely used to treat the neovascular type of AMD (nAMD). However, VEGF acts not only as a pro-angiogenic factor but also as an anti-apoptotic factor in the eyes. In this study, we found that anti-VEGF drugs, including bevacizumab (Bev), ranibizumab (Ran), and aflibercept (Afl), induced epithelial-mesenchymal transition (EMT) in ARPE-19 cells in vitro, accompanied by the induction of CCN2, a potent pro-fibrotic factor. Similarly, intravitreal injection of Afl into mouse eyes resulted in EMT in the retinal pigmented epithelium (RPE). Co-treatment with CCN5, an anti-fibrotic factor that down-regulates CCN2 expression, significantly attenuated the adverse effects of the anti-VEGF drugs both in vitro and in vivo. Inhibition of the VEGF signaling pathway with antagonists of VEGF receptors, SU5416 and ZM323881, induced EMT and up-regulated CCN2 in ARPE-19 cells. Additionally, knock-down of CCN2 with siRNA abolished the adverse effects of the anti-VEGF drugs in ARPE-19 cells. Collectively, these results suggest that anti-VEGF drugs induce EMT in RPE through the induction of CCN2 and that co-treatment with CCN5 attenuates the adverse effects of anti-VEGF drugs in mouse eyes.

Pharmacotherapies to prevent epidural fibrosis after laminectomy: a systematic review of in vitro and in vivo animal models

BACKGROUND CONTEXT

Excessive production of epidural fibrosis in the nerve root can be a pain source after laminectomy. Pharmacotherapy is a minimally invasive treatment option to attenuate epidural fibrosis by suppressing proliferation and activation of fibroblasts, inflammation, and angiogenesis, and inducing apoptosis.

PURPOSE

We reviewed and tabulated pharmaceuticals with their respective signaling axes implicated in reducing epidural fibrosis. Additionally, we summarized current literature for the feasibility of novel biologics and microRNA to lessen epidural fibrosis.

STUDY DESIGN/SETTING

Systematic Review.

METHODS

According to the PRISMA guidelines, we systematically reviewed the literature in October 2022. The exclusion criteria included duplicates, nonrelevant articles, and insufficient detail of drug mechanism.

RESULTS

We obtained a total of 2,499 articles from PubMed and Embase databases. After screening the articles, 74 articles were finally selected for the systematic review and classified based on the functions of drugs and microRNAs which included inhibition of fibroblast proliferation and activation, pro-apoptosis, anti-inflammation, and antiangiogenesis. In addition, we summarized various pathways to prevent epidural fibrosis.

CONCLUSION

This study allows a comprehensive review of pharmacotherapies to prevent epidural fibrosis during laminectomy.

CLINICAL SIGNIFICANCE

We expect that our review would enable researchers and clinicians to better understand the mechanism of anti-fibrosis drugs for the clinical application of epidural fibrosis therapies.

Significance of CCNs in liver regeneration

The liver has an inherent regenerative capacity via hepatocyte proliferation after mild-to-modest damage. When hepatocytes exhaust their replicative ability during chronic or severe liver damage, liver progenitor cells (LPC), also termed oval cells (OC) in rodents, are activated in the form of ductular reaction (DR) as an alternative pathway. LPC is often intimately associated with hepatic stellate cells (HSC) activation to promote liver fibrosis. The Cyr61/CTGF/Nov (CCN) protein family consists of six extracellular signaling modulators (CCN1-CCN6) with affinity to a repertoire of receptors, growth factors, and extracellular matrix proteins. Through these interactions, CCN proteins organize microenvironments and modulate cell signalings in a diverse variety of physiopathological processes. In particular, their binding to subtypes of integrin (αvβ5, αvβ3, α6β1, αvβ6, etc.) influences the motility and mobility of macrophages, hepatocytes, HSC, and LPC/OC during liver injury. This paper summarizes the current understanding of the significance of CCN genes in liver regeneration in relation to hepatocyte-driven or LPC/OC-mediated pathways. Publicly available datasets were also searched to compare dynamic levels of CCNs in developing and regenerating livers. These insights not only add to our understanding of the regenerative capability of the liver but also provide potential targets for the pharmacological management of liver repair in the clinical setting. Ccns in liver regeneration Restoring damaged or lost tissues requires robust cell growth and dynamic matrix remodeling. Ccns are matricellular proteins highly capable of influencing cell state and matrix production. Current studies have identified Ccns as active players in liver regeneration. Cell types, modes of action, and mechanisms of Ccn induction may vary depending on liver injuries. Hepatocyte proliferation is a default pathway for liver regeneration following mild-to-modest damages, working in parallel with the transient activation of stromal cells, such as macrophages and hepatic stellate cells (HSC). Liver progenitor cells (LPC), also termed oval cells (OC) in rodents, are activated in the form of ductular reaction (DR) and are associated with sustained fibrosis when hepatocytes lose their proliferative ability in severe or chronic liver damage. Ccns may facilitate both hepatocyte regeneration and LPC/OC repair via various mediators (growth factors, matrix proteins, integrins, etc.) for cell-specific and context-dependent functions.

Evaluation of the effectiveness of oxytocin and enalapril in the prevention of epidural fibrosis developed after laminectomy in rats

INTRODUCTION

Except for methylprednisolone, there is no current low-cost and low-side-effect drug/barrier method to prevent epidural fibrosis after spine surgery. However, the use of methylprednisolone has led to substantial controversy because of its serious side effects on wound healing. This study aimed to evaluate the effects of enalapril and oxytocin on preventing the development of epidural fibrosis in a rat laminectomy model.

MATERIALS

Under sedation anesthesia, T9, T10, and T11 laminectomy was performed on 24 Wistar Albino male rats. The animals were then separated into four groups; Sham group (only laminectomy was performed; n = 6), MP group (laminectomy was performed and 10 mg/kg/day methylprednisolone was administered intraperitoneally (ip) for 14 days; n = 6), ELP group (laminectomy was performed and 0.75 mg/kg/day enalapril was administered ip for 14 days; n = 6), OXT group (laminectomy was performed and 160 µg/kg/day oxytocin was administered ip for 14 days; n = 6). Four weeks after the laminectomy, all the rats were euthanised, and the spines were removed for histopathological, immunohistochemical, and biochemical examinations.

RESULTS

Histopathological examinations revealed that the degree of epidural fibrosis (X²=14.316, p = 0.003), collagen density (X²=16.050, p = 0.001), and fibroblast density (X²=17.500, p = 0.001) was higher in the Sham group and lower in the MP, ELP, and OXT groups. Immunohistochemical examinations showed that collagen type 1 immunoreactivity was higher in the Sham group and lower in the MP, ELP, and OXT groups (F = 54.950, p < 0.001). The highest level of α-smooth muscle actin immunoreactivity was seen in the Sham and OXT groups, and the lowest was in the MP and ELP groups (F = 33.357, p < 0.001). Biochemical analysis revealed that tissue levels of TNF-α, TGF-β, IL-6, CTGF, caspase-3, p-AMPK, pmTOR, and mTOR/pmTOR were higher in the Sham group and lower in MP, ELP, and OXT groups (p < 0.05). The GSH/GSSG levels were lower in the Sham group and higher in the other three groups (X²=21.600, p < 0.001).

CONCLUSION

The study results showed that enalapril and oxytocin, which are known to have anti-inflammatory, antioxidant, anti-apoptotic, and autophagy-related regenerative properties, could reduce the development of epidural fibrosis after laminectomy in rats.

The matricellular protein CCN5 induces apoptosis in myofibroblasts through SMAD7-mediated inhibition of NFκB

We previously showed that the matricellular protein CCN5 reverses established cardiac fibrosis (CF) through inducing apoptosis in myofibroblasts (MyoFBs) but not in cardiomyocytes or fibroblasts (FBs). In this study, we set out to elucidate the molecular mechanisms underlying CCN5-mediated selective apoptosis of MyoFBs. We first observed that the apoptotic protein p53 and the anti-apoptotic protein NFκB are simultaneously induced in MyoFBs. When the expression level of p53 was suppressed using a siRNA, CCN5 did not induce apoptosis in MyoFBs. By contrast, when NFκB signaling was inhibited using IKK VII, an IκB inhibitor, MyoFBs underwent apoptosis even in the absence of CCN5. SMAD7 is one of the downstream targets of CCN5 and it was previously shown to potentiate apoptosis in epithelial cells through inhibition of NFκB. In accordance with these reports, when the expression of SMAD7 was suppressed using a siRNA, NFκB signaling was enhanced, and CCN5 did not induce apoptosis. Lastly, we used a luciferase reporter construct to show that CCN5 positively regulated SMAD7 expression at the transcriptional level. Collectively, our data suggest that a delicate balance between the two mutually antagonistic proteins p53 and NFκB is maintained for MyoFBs to survive, and CCN5 tips the balance in favor of the apoptotic protein p53. This study provides insight into the anti-fibrotic activity of CCN5 during the regression of CF.

[Lowered expression of CCN5 in endometriotic tissues promotes proliferation, migration and invasion of endometrial stromal cells]

OBJECTIVE

To explore the expression of CCN5 in endometriotic tissues and its impact on proliferation, migration and invasion of human endometrial stromal cells (HESCs).

METHODS

We collected ovarian endometriosis samples from 20 women receiving laparoscopic surgery and eutopic endometrium samples from 15 women undergoing IVF-ET for comparison of CCN5 expression. Cultured HESCs were transfected with a recombinant adenovirus Ad-CCN5 for CCN5 overexpression or with a CCN5-specific siRNA for knocking down CCN5 expression, and the changes of cell proliferation, migration and invasion were evaluated using CCK-8 assay, wound healing assay and Transwell chamber assay. RT-qPCR and Western blotting were used to examine the expression levels of epithelial-mesenchymal transition (EMT) markers including E-cadherin, N-cadherin, Snail-1 and vimentin in HESCs with CCN5 overexpression or knockdown.

RESULTS

CCN5 expression was significantly decreased in ovarian endometriosis tissues as compared with eutopic endometrium samples (P < 0.01). CCN5 overexpression obviously inhibited the proliferation, migration and invasion of HESCs, significantly increased the expression of E-cadherin and decreased the expressions of N-cadherin, Snail-1 and vimentin (P < 0.01). CCN5 knockdown significantly enhanced the proliferation, migration and invasion of HESCs and produced opposite effects on the expressions of E-cadherin, N-cadherin, Snail-1 and vimentin (P < 0.01).

CONCLUSION

CCN5 can regulate the proliferation, migration and invasion of HESCs and thus plays an important role in EMT of HESCs, suggesting the potential of CCN5 as a therapeutic target for endometriosis.

Tissue distribution and transcriptional regulation of CCN5 in the heart after myocardial infarction

CCN5 is a divergent member of the cellular communication network factor (CCN) family in that it lacks the carboxyl terminal cystine knot domain common to the other CCN family members. CCN5 has been reported to antagonize the profibrotic actions of CCN2 and to inhibit myocardial collagen deposition and fibrosis in chronic pressure overload of the heart. However, what mechanisms that regulate CCN5 activity in the heart remain unknown. Recombinant, replication defective adenovirus encoding firefly luciferase under control of the human CCN5 promoter was prepared and used to investigate what mechanisms regulate CCN5 transcription in relevant cells. Tissue distribution of CCN5 in hearts from healthy mice and from mice subjected to myocardial infarction was investigated. Contrary to the profibrotic immediate early gene CCN2, we find that CCN5 is induced in the late proliferation and maturation phases of scar healing. CCN5 was identified principally in endothelial cells, fibroblasts, smooth muscle cells, and macrophages. Our data show that CCN5 gene transcription and protein levels are induced by catecholamines via β₂-adrenergic receptors. Myocardial induction of CCN5 was further confirmed in isoproterenol-infused mice. We also find that CCN5 transcription is repressed by TNF-α, an inflammatory mediator highly elevated in early phases of wound healing following myocardial infarction. In conclusion, CCN5 predominates in endothelial cells, fibroblasts, and macrophages of the differentiating scar tissue and its transcription is conversely regulated by β₂-adrenergic agonists and TNF-α.

Down-Regulation of a Profibrotic Transforming Growth Factor-β1/Cellular Communication Network Factor 2/Matrix Metalloprotease 9 Axis by Triamcinolone Improves Idiopathic Subglottic Stenosis

Idiopathic subglottic stenosis (iSGS) is a progressive fibrotic disease characterized by life-threatening airway narrowing. Although the molecular underpinnings are unknown, previous reports showing that subglottic serial intralesional steroid injections (SILSIs) improve clinical outcomes suggest a steroid-sensitive pathway in iSGS. Herein, a prospective study was conducted to determine the changes in profibrotic markers during SILSI to identify steroid-sensitive profibrotic drivers. Seven newly diagnosed patients with iSGS were recruited for SILSI. Subglottic biopsies before and after SILSI treatments were evaluated for histologic and molecular markers by confocal microscopy and RT-qPCR. At baseline, iSGS subglottises contained abundant vimentin-positive/α-smooth muscle actin-negative fibroblasts, intermingled with a matrix of fibronectin and types I and VI collagen. Transforming growth factor (TGF)-β1 was up-regulated primarily in glandular epithelium. Cellular communication network factor 2 (CCN2) was mainly up-regulated in stromal fibroblasts surrounding TGF-β1-positive glandular structures. SILSI improved iSGS by reducing fibroblast infiltration and increasing matrix remodeling. Mechanistically, SILSI counteracted the effects of TGF-β1 by inducing matrix metalloprotease 9 (MMP9) expression while repressing CCN2 expression, without affecting TGFβ1 levels. Treatment of primary iSGS-derived fibroblasts with TGF-β1 recapitulated aspects of the disease in vivo, demonstrating that the induction in CCN2 and repression of MMP9 are caused by changes in histone acetylation induced by TGF-β1. Triamcinolone counteracted the coregulation of these genes by impairing SMAD2/3 binding to promoter regions, and not through histone acetylation. In conclusion, this study shows that SILSI counteracts a dysregulated TGF-β1/CCN2/MMP9 axis involved in iSGS development.

Mitochondrial remodelling-a vicious cycle in diabetic complications

Diabetes mellitus (DM) is a chronic, metabolic condition characterized by excessive blood glucose that causes perturbations in physiological functioning of almost all the organs of human body. This devastating metabolic disease has its implications in cognitive decline, heart damage, renal, retinal and neuronal complications that severely affects quality of life and associated with decreased life expectancy. Mitochondria possess adaptive mechanisms to meet the cellular energy demand and combat cellular stress. In recent years mitochondrial homeostasis has been point of focus where several mechanisms regulating mitochondrial health and function are evaluated. Mitochondrial dynamics plays crucial role in maintaining healthy mitochondria in cell under physiological as well as stress condition. Mitochondrial dynamics and corresponding regulating mechanisms have been implicated in progression of metabolic disorders including diabetes and its complications. In current review we have discussed about role of mitochondrial dynamics under physiological and pathological conditions. Also, modulation of mitochondrial fission and fusion in diabetic complications are described. The available literature supports mitochondrial remodelling as reliable target for diabetic complications.

Emerging role of CCN family proteins in fibrosis

Fibrosis is a common pathological change characterized by the excessive accumulation of fibrous connective tissue. Once uncontrolled, this pathological progress can lead to irreversible damage to the structure and function of organs, which is a serious threat to human health and life. Actually, the disability and death of patients caused by many chronic diseases have a closed relationship with fibrosis. The CCN protein family, including six members, is a small group of matrix proteins exhibiting structurally similar features. In the past 20 years, different biological functions of CCN proteins have been identified in various diseases. Of note, it has been recently shown that they are implicated in the key pathological process of fibrosis. In this review, we summarize the current status of knowledge regarding the role of CCN proteins involved in the pathogenesis of fibrosis diseases in detail. Furthermore, we highlight some of the underlying interaction mechanisms of CCN protein acting in fibrosis that helps to develop new drugs and determine appropriate clinical strategies for fibrotic diseases.

Endogenous CCN5 Participates in Angiotensin II/TGF-β1 Networking of Cardiac Fibrosis in High Angiotensin II-Induced Hypertensive Heart Failure

Aberrant activation of angiotensin II (Ang II) accelerates hypertensive heart failure (HF); this has drawn worldwide attention. The complex Ang II/transforming growth factor (TGF)-β₁ networking consists of central mechanisms underlying pro-fibrotic effects; however, this networking still remains unclear. Cellular communication network 5 (CCN5), known as secreted matricellular protein, mediates anti-fibrotic activity by inhibiting fibroblast-to-myofibroblast transition and the TGF-β₁ signaling pathway. We hypothesized that endogenous CCN5 plays an essential role in TGF-β₁/Ang II networking-induced cardiac fibrosis (CF), which accelerates the development of hypertensive HF. This study aimed to investigate the potential role of CCN5 in TGF-β₁/Ang II networking-induced CF. Our clinical retrospective study demonstrated that serum CCN5 decreased in hypertensive patients, but significantly increased in hypertensive patients taking oral angiotensin-converting enzyme inhibitor (ACEI). A negative association was observed between CCN5 and Ang II in grade 2and 3 hypertensive patients receiving ACEI treatment. We further created an experimental model of high Ang II-induced hypertensive HF. CCN5 was downregulated in the spontaneously hypertensive rats (SHRs) and increased via the inhibition of Ang II production by ACEI. This CCN5 downregulation may activate the TGF-β₁ signaling pathway, which promotes direct deposition of the extracellular matrix (ECM) and fibroblast-to-myofibroblast transition via activated Smad-3. Double immunofluorescence staining of CCN5 and cell markers of cardiac tissue cell types suggested that CCN5 was mainly expressed in the cardiac fibroblasts. Isolated cardiac fibroblasts were exposed to Ang II and transfected with small interfering RNA targeting CCN5. The expression of TGF-β₁ together with Col Ia and Col IIIa was further promoted, and alpha-smooth muscle actin (α-SMA) was strongly expressed in the cardiac fibroblasts stimulated with Ang II and siRNA. In our study, we confirmed the anti-fibrotic ability of endogenous CCN5 in high Ang II-induced hypertensive HF. Elevated Ang II levels may decrease CCN5 expression, which subsequently activates TGF-β₁ and finally promotes the direct deposition of the ECM and fibroblast-to-myofibroblast transition via Smad-3 activation. CCN5 may serve as a potential biomarker for estimating CF in hypertensive patients. A novel therapeutic target should be developed for stimulating endogenous CCN5 production.

Alterations in extracellular matrix composition during aging and photoaging of the skin

Human skin is composed of the cell-rich epidermis, the extracellular matrix (ECM) rich dermis, and the hypodermis. Within the dermis, a dense network of ECM proteins provides structural support to the skin and regulates a wide variety of signaling pathways which govern cell proliferation and other critical processes. Both intrinsic aging, which occurs steadily over time, and extrinsic aging (photoaging), which occurs as a result of external insults such as solar radiation, cause alterations to the dermal ECM. In this study, we utilized both quantitative and global proteomics, alongside single harmonic generation (SHG) and two-photon autofluorescence (TPAF) imaging, to assess changes in dermal composition during intrinsic and extrinsic aging. We find that both intrinsic and extrinsic aging result in significant decreases in ECM-supporting proteoglycans and structural ECM integrity, evidenced by decreasing collagen abundance and increasing fibril fragmentation. Intrinsic aging also produces changes distinct from those produced by photoaging, including reductions in elastic fiber and crosslinking enzyme abundance. In contrast, photoaging is primarily defined by increases in elastic fiber-associated protein and pro-inflammatory proteases. Changes associated with photoaging are evident even in young (mid 20s) sun-exposed forearm skin, indicating that proteomic evidence of photoaging is present decades prior to clinical signs of photoaging. GO term enrichment revealed that both intrinsic aging and photoaging share common features of chronic inflammation. The proteomic data has been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the data set identifier PXD015982.

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Intrinsic aging and photoaging both decrease ECM-supporting proteoglycans and structural ECM.

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Intrinsic aging produces reductions in elastic fiber and crosslinking enzyme abundance.

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Photoaging results in increases in pro-inflammatory proteases and elastic fiber abundance.

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Intrinsic aging and photoaging share common features associated with chronic inflammation.

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Proteomic changes associated with photoaging are evident decades prior to clinical aging signs.

CCN5 Reduces Ligamentum Flavum Hypertrophy by Modulating the TGF-β Pathway

Ligamentum flavum hypertrophy (LFH) is the most important component of lumbar spinal canal stenosis. Although the pathophysiology of LFH has been extensively studied, no method has been proposed to prevent or treat it. Since the transforming growth factor-β (TGF-β) pathway is known to be critical in LFH pathology, we investigated whether LFH could be prevented by blocking or modulating the TGF-β mechanism. Human LF cells were used for the experiments. First, we created TGF-β receptor 1 (TGFBR1) knock out (KO) cells with CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 biotechnology and treated them with TGF-β1 to determine the effects of blocking the TGF-β pathway. Subsequently, we studied the effect of CCN5, which has recently been proposed to modulate the TGF-β pathway. To assess the predisposition toward fibrosis, α-smooth muscle actin (αSMA), fibronectin, collagen-1, collagen-3, and CCN2 were evaluated with quantitative real-time polymerase chain reaction, western blotting, and immunocytochemistry. The TGFBR1 KO LF cells were successfully constructed with high KO efficiency. In wild-type (WT) cells, treatment with TGF-β1 resulted in the overexpression of the messenger RNA (mRNA) of fibrosis-related factors. However, in KO cells, the responses to TGF-β1 stimulation were significantly lower. In addition, CCN5 and TGF-β1 co-treatment caused a notable reduction in mRNA expression levels compared with TGF-β1 stimulation only. The αSMA protein expression increased with TGF-β1 but decreased with CCN5 treatment. TGF-β1 induced LF cell transdifferentiation from fibroblasts to myofibroblasts. However, this cell transition dramatically decreased in the presence of CCN5. In conclusion, CCN5 could prevent LFH by modulating the TGF-β pathway. © 2019 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 37:2634-2644, 2019.

Lanatoside C protects mice against bleomycin-induced pulmonary fibrosis through suppression of fibroblast proliferation and differentiation

It has been established that lanatoside C, a FDA-approved cardiac glycoside, reduces proliferation of cancer cell lines. The proliferation of fibroblasts is critical to the pathogenesis of pulmonary fibrosis (PF), a progressive and fatal fibrotic lung disease lacking effective treatment. In this study we have investigated the impact of lanatoside C on a bleomycin (BLM)-induced mouse model of PF and through the evaluation of fibroblast proliferation and activation in vitro. We evaluated explanted lung tissue by histological staining, western blot analysis, qRT-PCR and survival analysis, demonstrating that lanatoside C was able to protect mice against BLM-induced pulmonary fibrosis. The proliferation of cultured pulmonary fibroblasts isolated from BLM-induced PF mice was suppressed by lanatoside C, as hypothesized, through the induction of cell apoptosis and cell cycle arrest at the G2/M phase. The Akt signalling pathway was involved in this process. Interestingly, the production of α-SMA, fibronectin, and collagen I and III in response to TGF-β1 in healthy mouse fibroblasts was suppressed following lanatoside C administration by inhibition of TGF-β1/Smad signalling. In addition, TGF-β1-induced migration in lung fibroblasts was also impeded after lanatoside C treatment. Together, our data revealed that lanatoside C alleviated BLM-induced pulmonary fibrosis in mice via attenuation of growth and differentiation of fibroblasts, suggesting that it has potential as a candidate therapy for PF patients.

Emerging roles of transforming growth factor β signaling in wet age-related macular degeneration

Age-related macular degeneration (AMD) is one of the major causes of irreversible blindness among aging populations in developed countries and can be classified as dry or wet according to its progression. Wet AMD, which is characterized by angiogenesis on the choroidal membrane, is uncommonly seen but more severe. Controlling or completely inhibiting the factors that contribute to the progression of events that lead to angiogenesis may be an effective strategy for treating wet AMD. Emerging evidence has shown that transforming growth factor-β (TGF-β) signaling plays a significant role in the progression of wet AMD. In this review, we described the roles of and changes in TGF-β signaling in the development of AMD and discussed the mechanisms of the TGF-β superfamily in choroidal neovascularization (CNV) and wet AMD, including the modulation of angiogenesis-related factors, inflammation, vascular fibrosis, and immune responses, as well as cross-talk with other signaling pathways. These remarkable findings indicate that TGF-β signaling is a potential target for wet AMD treatment.

CCN proteins as potential actionable targets in scleroderma

Systemic sclerosis (SSc) is a complex autoimmune connective tissue disease combining inflammatory, vasculopathic and fibrotic manifestations. Skin features, which give their name to the disease and are considered as diagnostic as well as prognostic markers, have not been thoroughly investigated in terms of therapeutic targets. CCN proteins (CYR61/CCN1, CTGF/CCN2, NOV/CCN3 and WISP1-2-3 as CCN4-5-6) are a family of secreted matricellular proteins implicated in major cellular processes such as cell growth, migration, differentiation. They have already been implicated in key pathophysiological processes of SSc, namely fibrosis, vasculopathy and inflammation. In this review, we discuss the possible implication of CCN proteins in SSc pathogenesis, with a special focus on skin features, and identify the potential actionable CCN targets.

Artesunate inhibits fibroblasts proliferation and reduces surgery-induced epidural fibrosis via the autophagy-mediated p53/p21waf1/cip1 pathway

Fibroblast proliferation is considered to be a major cause in the process of epidural fibrosis formation. Autophagy is a tightly-regulated catabolic process in charge of degrading intracellular components. Although autophagy has been associated with fibrosis of different tissues, the effect of autophagy on epidural fibrosis is still unknown. The aim of this study was to investigate the function and mechanism of autophagy induced by Artesunate (ART), a classical antimalarial agent extracted from the Chinese medicinal herb. In vitro, the effect of ART on inducing fibroblast autophagy was evaluated via LC3 immunofluorescent staining, Transmission Electron Microscopy (TEM) and western blotting analysis. Moreover, the effect of ART on inhibiting fibroblast proliferation was investigated by CCK-8 assay, EdU incorporation assay, flow cytometry and western blotting analysis. Results indicated that ART could induce autophagy and inhibit proliferation in fibroblasts. The inhibitory effect of ART on fibroblast proliferation was associated with the upregulation of p53 and p21^waf1/cip1 proteins. Intriguingly, 3-MA, a classical autophagy inhibitor, attenuated ART-induced p53/p21^waf1/cip1 pathway activation and fibroblast proliferation inhibition. In vivo, the effect of ART on reducing epidural fibrosis was detected by histological macroscopic assessment, hydroxyproline content analysis, histological and immunohistochemical staining. The results revealed that ART had significant suppressive effects on epidural fibrosis following laminectomy in rats. In conclusion, this research demonstrated that ART could inhibit fibroblast proliferation and reduce epidural fibrosis formation after laminectomy, and the potential mechanism might through autophagy cascade-mediated p53/p21^waf1/cip1 pathway. It might provide a novel reagent for reducing epidural fibrosis after spinal laminectomy surgery.

Roles of the TGF-β⁻VEGF-C Pathway in Fibrosis-Related Lymphangiogenesis

Lymphatic vessels drain excess tissue fluids to maintain the interstitial environment. Lymphatic capillaries develop during the progression of tissue fibrosis in various clinical and pathological situations, such as chronic kidney disease, peritoneal injury during peritoneal dialysis, tissue inflammation, and tumor progression. The role of fibrosis-related lymphangiogenesis appears to vary based on organ specificity and etiology. Signaling via vascular endothelial growth factor (VEGF)-C, VEGF-D, and VEGF receptor (VEGFR)-3 is a central molecular mechanism for lymphangiogenesis. Transforming growth factor-β (TGF-β) is a key player in tissue fibrosis. TGF-β induces peritoneal fibrosis in association with peritoneal dialysis, and also induces peritoneal neoangiogenesis through interaction with VEGF-A. On the other hand, TGF-β has a direct inhibitory effect on lymphatic endothelial cell growth. We proposed a possible mechanism of the TGF-β–VEGF-C pathway in which TGF-β promotes VEGF-C production in tubular epithelial cells, macrophages, and mesothelial cells, leading to lymphangiogenesis in renal and peritoneal fibrosis. Connective tissue growth factor (CTGF) is also involved in fibrosis-associated renal lymphangiogenesis through interaction with VEGF-C, in part by mediating TGF-β signaling. Further clarification of the mechanism might lead to the development of new therapeutic strategies to treat fibrotic diseases.

CCN5/WISP2 and metabolic diseases

Obesity and type 2 diabetes increase worldwide at an epidemic rate. It is expected that by the year 2030 around 500 million people will have diabetes; predominantly type 2 diabetes. The CCN family of proteins has become of interest in both metabolic and other common human diseases because of their effects on mesenchymal stem cell (MSCs) proliferation and differentiation as well as being important regulators of fibrosis. We here review current knowledge of the WNT1 inducible signaling pathway protein 2 (CCN5/WISP2). It has been shown to be an important regulator of both these processes through effects on both the canonical WNT and the TGFβ pathways. It is also under normal regulation by the adipogenic commitment factor BMP4, in contrast to conventional canonical WNT ligands, and allows MSCs to undergo normal adipose cell differentiation. CCN5/WISP2 is highly expressed in, and secreted by, MSCs and is an important regulator of MSCs growth. In a transgenic mouse model overexpressing CCN5/WISP2 in the adipose tissue, we have shown that it is secreted and circulating in the blood, the mice develop hypercellular white and brown adipose tissue, have increased lean body mass and enlarged hypercellular hearts. Obese transgenic mice had improved insulin sensitivity. Interestingly, the anti-fibrotic effect of CCN5/WISP2 is protective against heart failure by inhibition of the TGFβ pathway. Understanding how CCN5/WISP2 is regulated and signals is important and may be useful for developing new treatment strategies in obesity and metabolic diseases and it can also be a target in regenerative medicine.

Blockade of PDGF Receptors by Crenolanib Has Therapeutic Effect in Patient Fibroblasts and in Preclinical Models of Systemic Sclerosis

Systemic sclerosis (SSc) is a multi-organ fibrotic disease with few treatment options. Activated fibroblasts are the key effector cells in SSc responsible for the excessive production of collagen and the development of fibrosis. Platelet-derived growth factor (PDGF), a potent mitogen for cells of mesenchymal origin, has been implicated in the activation of SSc fibroblasts. Our aim was to examine the therapeutic potential of crenolanib, an inhibitor of PDGF receptor signaling, in cultured fibroblasts and in angiotensin II-induced skin and heart fibrosis. Crenolanib effectively inhibited proliferation and migration of SSc and healthy control fibroblasts and attenuated basal and transforming growth factor-β-induced expression of CCN2/CTGF and periostin. In contrast to healthy control fibroblasts, SSc fibroblasts proliferated in response to PDGFAA, whereas a combination of PDGFAA and CCN2 was required to elicit a similar response in healthy control fibroblasts. PDGF receptor α mRNA correlated with CCN2 and other fibrotic markers in the skin of SSc patients. In mice challenged with angiotensin II, PDGF receptor α-positive cells were increased in the skin and heart. These PDGF receptor α-positive cells co-localized with PDGF receptor β, procollagen, and periostin. Treatment with crenolanib attenuated the skin and heart fibrosis. Our data indicate that inhibition of PDGF signaling presents an attractive therapeutic approach for SSc.

Upregulation of microRNA-574-3p in a human gastric cancer cell line AGS by TGF-β1

The mechanisms that regulate miR-574-3p expression in cells remain elusive. In the present study, we used real-time PCR assay to demonstrate TGF-β1-induced miR-574-3p upregulation in AGS cells, which was inhibited by TGF-β receptor I inhibitor SB431542. We used a computer search to identify Smad binding sites upstream of the miR-574-3p precursor sequence. We demonstrated that silencing Smad4, but not Smad2 or Smad3, significantly inhibited the TGF-β1-induced miR-574-3p upregulation in AGS cells. Furthermore, TGF-β1 significantly increased the activity of a dual-luciferase reporter that contains the Smad binding sites upstream of the miR-574 precursor sequence. Silencing Smad4 significantly inhibited the TGF-β1-induced increase in the activity of the reporter in AGS cells. ChIP assay showed that Smad4 directly bound to the promoter of miR-574-3p. MiR-574-3p inhibition was effective in eliminating the inhibition of AGS cell proliferation induced by TGF-β1, suggesting that TGF-β1 inducing upregulation of miR-574-3p is functionally significant.

CCN family of proteins: critical modulators of the tumor cell microenvironment

The CCN family of proteins consisting of CCN1 (Cyr61), CCN2 (CTGF), CCN3 (NOV), CCN4 (WISP-1), CCN5 (WISP-2) and CCN6 (WISP-3) are considered matricellular proteins operating essentially in the extracellular microenvironment between cells. Evidence has also been gradually building since their first discovery of additional intracellular roles although the major activity is triggered at the cell membrane. The proteins consist of 4 motifs, a signal peptide (for secretion} followed consecutively by the IGFBP, VWC, TSP1 and CT (C-terminal cysteine knot domain) motifs, which signify their potential binding partners and functional connections to a variety of key regulators of physiological processes. With respect to cancer it is now clear that, whereas certain members can facilitate tumor behavior and progression, others can competitively counter the process. It is therefore clear that the net outcome of biological interactions in the matrix and what gets signaled or inhibited can be a function of the interplay of these CCN 1-6 proteins. Because the CCN proteins further interact with other key proteins, like growth factors in the matrix, the balance is not only important but can vary dynamically with the physiological states of tumor cells and the surrounding normal cells. The tumor niche with its many cell players has surfaced as a critical determinant of tumor behavior, invasiveness, and metastasis. It is in this context that CCN proteins should be investigated with the potential of being recognized and validated for future therapeutic approaches.

Cell surface receptors for CCN proteins

The CCN family (CYR61; CTGF; NOV; CCN1-6; WISP1-3) of matricellular proteins in mammals is comprised of six homologous members that play important roles in development, inflammation, tissue repair, and a broad range of pathological processes including fibrosis and cancer. Despite considerable effort to search for a high affinity CCN-specific receptor akin to growth factor receptors, no such receptor has been found. Rather, CCNs bind several groups of multi-ligand receptors as characteristic of other matricellular proteins. The most extensively documented among CCN-binding receptors are integrins, including αvβ3, αvβ5, α5β1, α6β1, αIIbβ3, αMβ2, and αDβ2, which mediate diverse CCN functions in various cell types. CCNs also bind cell surface heparan sulfate proteoglycans (HSPGs), low density liproprotein receptor-related proteins (LRPs), and the cation-independent mannose-6-phosphate (M6P) receptor, which are endocytic receptors that may also serve as co-receptors in cooperation with other cell surface receptors. CCNs have also been reported to bind FGFR-2, Notch, RANK, and TrkA, potentially altering the affinities of these receptors for their ligands. The ability of CCNs to bind a multitude of receptors in various cell types may account for the remarkable versatility of their functions, and underscore the diverse signaling pathways that mediate their activities.

Fibroblast-Extracellular Matrix Interactions in Tissue Fibrosis

Activated myofibroblasts are key effector cells in tissue fibrosis. Emerging evidence suggests that myofibroblasts infiltrating fibrotic tissues originate predominantly from local mesenchyme-derived populations. Alterations in the extracellular matrix network play an important role in modulating fibroblast phenotype and function. In a pro-inflammatory environment, generation of matrix fragments may induce a matrix-degrading fibroblast phenotype. Deposition of ED-A fibronectin plays an important role in myofibroblast transdifferentiation. In fibrotic tissues, the matrix is enriched with matricellular macromolecules that regulate growth factor-mediated responses and modulate protease activation. This manuscript discusses emerging concepts on the role of the extracellular matrix in regulation of fibroblast behavior.