Yin/Yang expression of CCN family members: Transforming growth factor beta 1, via ALK5/FAK/MEK, induces CCN1 and CCN2, yet suppresses CCN3, expression in human dermal fibroblasts

Matricellular protein CCN1 promotes collagen alignment and scar integrity after myocardial infarction

BACKGROUND

Members of the cellular communication network family (CCN) of matricellular proteins, like CCN1, have long been implicated in the regulation of cellular processes underlying wound healing, tissue fibrogenesis, and collagen dynamics. While many studies suggest antifibrotic actions for CCN1 in the adult heart through the promotion of myofibroblast senescence, they largely relied on exogenous supplementation strategies in in vivo models of cardiac injury where its expression is already induced-which may confound interpretation of its function in this process. The objective of this study was to interrogate the role of the endogenous protein on fibroblast function, collagen structural dynamics, and its associated impact on cardiac fibrosis after myocardial infarction (MI).

METHODS/RESULTS

Here, we employed CCN1 loss-of-function methodologies, including both in vitro siRNA-mediated depletion and in vivo fibroblast-specific knockout mice to assess the role of the endogenous protein on cardiac fibroblast fibrotic signaling, and its involvement in acute scar formation after MI. In vitro depletion of CCN1 reduced cardiac fibroblast senescence and proliferation. Although depletion of CCN1 decreased the expression of collagen processing and stabilization enzymes (i.e., P4HA1, PLOD1, and PLOD2), it did not inhibit myofibroblast induction or type I collagen synthesis. Alone, fibroblast-specific removal of CCN1 did not negatively impact ventricular performance or myocardial collagen content but did contribute to disorganization of collagen fibrils and increased matrix compliance. Similarly, Ccn1 ablated animals subjected to MI showed no discernible alterations in cardiac structure or function one week after permanent coronary artery ligation, but exhibited marked increases in incidence of mortality and cardiac rupture. Consistent with our findings that CCN1 depletion does not assuage myofibroblast conversion or type I collagen synthesis in vitro, Ccn1 knockout animals revealed no measurable differences in collagen scar width or mass compared to controls; however, detailed structural analyses via SHG and TEM of scar regions revealed marked alterations in their scar collagen topography-exhibiting changes in numerous macro- and micro-level collagen architectural attributes. Specifically, Ccn1 knockout mice displayed heightened ECM structural complexity in post-MI scar regions, including diminished local alignment and heightened tortuosity of collagen fibers, as well as reduced organizational coherency, packing, and size of collagen fibrils. Associated with these changes in ECM topography with the loss of CCN1 were reductions in fibroblast-matrix interactions, as evidenced by reduced fibroblast nuclear and cellular deformation in vivo and reduced focal-adhesion formation in vitro; findings that ultimately suggest CCN1's ability to influence fibroblast-led collagen alignment may in part be credited to its capacity to augment fibroblast-matrix interactions.

CONCLUSIONS

These findings underscore the pivotal role of endogenous CCN1 in the scar formation process occurring after MI, directing the appropriate arrangement of the extracellular matrix's collagenous components in the maturing scar-shaping the mechanical properties that support its structural stability. While this suggests an adaptive role for CCN1 in regulating collagen structural attributes crucial for supporting scar integrity post MI, the long-term protracted expression of CCN1 holds maladaptive implications, potentially diminishing collagen structural complexity and compliance in non-infarct regions.

Evaluation of the Use of Cell Lines in Studies of Selenium-Dependent Glutathione Peroxidase 2 (GPX2) Involvement in Colorectal Cancer

Hydroperoxides (ROOHs) are known as damaging agents capable of mediating mutation, while a role as signaling agents through oxidation of protein sulfhydryls that can alter cancer-related pathways has gained traction. Glutathione peroxidase 2 (GPX2) is an antioxidant enzyme that reduces ROOHs at the expense of glutathione (GSH). GPX2 is noted for a tendency of large increases or decreases in expression levels during tumorigenesis that leads to investigators focusing on its role in cancer. However, GPX2 is only one component of multiple enzyme families that metabolize ROOH, and GPX2 levels are often very low in the context of these other ROOH-reducing activities. Colorectal cancer (CRC) was selected as a case study for examining GPX2 function, as colorectal tissues and cancers are sites where GPX2 is highly expressed. A case can be made for a significant impact of changes in expression levels. There is also a link between GPX2 and NADPH oxidase 1 (NOX1) from earlier studies that is seldom addressed and is discussed, presenting data on a unique association in colon and CRC. Tumor-derived cell lines are quite commonly used for pre-clinical studies involving the role of GPX2 in CRC. Generally, selection for this type of work is limited to identifying cell lines based on high and low GPX2 expression with the standard research scheme of overexpression in low-expressing lines and suppression in high-expressing lines to identify impacted pathways. This overlooks CRC subtypes among cell lines involving a wide range of gene expression profiles and a variety of driver mutation differences, along with a large difference in GPX2 expression levels. A trend for low and high GPX2 expressing cell lines to segregate into different CRC subclasses, indicated in this report, suggests that choices based solely on GPX2 levels may provide misleading and conflicting results by disregarding other properties of cell lines and failing to factor in differences in potential protein targets of ROOHs. CRC and cell line classification schemes are presented here that were intended to assist workers in performing pre-clinical studies but are largely unnoted in studies on GPX2 and CRC. Studies are often initiated on the premise that the transition from normal to CRC is associated with upregulation of GPX2. This is probably correct. However, the source normal cells for CRC could be almost any colon cell type, some with very high GPX2 levels. These factors are addressed in this study.

The role of yes activated protein (YAP) in melanoma metastasis

Hippo was first identified in a genetic screen as a protein that suppressed proliferation and cell growth. Subsequently, it was shown that hippo acted in a so-called canonical cascade to suppress Yorkie, the Drosophila equivalent of Yes-activated protein (YAP), a mechanosensitive transcriptional cofactor that enhances the activity of the TEAD family of transcription factors. YAP promotes fibrosis, activation of cancer-associated fibroblasts, angiogenesis and cancer cell invasion. YAP activates the expression of the matricellular proteins CCN1 (cyr61) and CCN2 (ctgf), themselves mediators of fibrogenesis and oncogenesis, and coordination of matrix deposition and angiogenesis. This review discusses how therapeutically targeting YAP through YAP inhibitors verteporfin and celastrol and its downstream mediators CCN1 and CCN2 might be useful in treating melanoma.

The yes-associated protein-1 (YAP1) inhibitor celastrol suppresses the ability of transforming growth factor β to activate human gingival fibroblasts

OBJECTIVE

To determine whether celastrol, an inhibitor of the mechanosensitive transcriptional cofactor yes-associated protein-1 (YAP1), impairs the ability of TGFβ1 to stimulate fibrogenic activity in human gingival fibroblast cell line.

DESIGN

Human gingival fibroblasts were pre-treated with celastrol or DMSO followed by stimulation with or without TGFβ1 (4 ng/ml). We then utilized bulk RNA sequencing (RNAseq), real-time polymerase chain reaction (RT-PCR), Western blot, immunofluorescence, cell proliferation assays to determine if celastrol impaired TGFβ1-induced responses in a human gingival fibroblast cell line.

RESULTS

Celastrol impaired the ability of TGFβ1 to induce expression of the profibrotic marker and mediator CCN2. Bulk RNAseq analysis of gingival fibroblasts treated with TGFβ1, in the presence or absence of celastrol, revealed that celastrol impaired the ability of TGFβ1 to induce mRNA expression of genes within extracellular matrix, wound healing, focal adhesion and cytokine/Wnt signaling clusters. RT-PCR analysis of extracted RNAs confirmed that celastrol antagonized the ability of TGFβ1 to induce expression of genes anticipated to contribute to fibrotic responses. Celastrol also reduced gingival fibroblast proliferation, and YAP1 nuclear localization in response to TGFβ1.

CONCLUSION

YAP1 inhibitors such as celastrol could be used to impair pro-fibrotic responses to TGFβ1 in human gingival fibroblasts.

A modest proposal: targeting αv integrin-mediated activation of latent TGFbeta as a novel therapeutic approach to treat scleroderma fibrosis

INTRODUCTION

The potent profibrotic cytokine transforming growth factor-β (TGF-β) has been associated with the onset and progression of the fibrosis seen in the autoimmune connective tissue disease scleroderma (systemic sclerosis, SSc).

AREA COVERED

This review explores the data supporting the notion that TGF-β contributes to SSc fibrosis and examines why initiating clinical trials in SSc aimed at targeting integrin-mediated latent TGF-β activation is timely.

EXPERT OPINION

Targeting TGF-β directly has not been proven to be clinically effective in this disease. Conversely, targeting matrix stiffness, which perpetuates fibrosis, may have more promise. Intriguingly, targeting integrin-mediated activation of latent TGF-β, which bridges these concepts, may have therapeutic value.

Back to the future: targeting the extracellular matrix to treat systemic sclerosis

Fibrosis is the excessive deposition of a stable extracellular matrix (ECM); fibrotic tissue is composed principally of highly crosslinked type I collagen and highly contractile myofibroblasts. Systemic sclerosis (SSc) is a multisystem autoimmune connective tissue disease characterized by skin and organ fibrosis. The fibrotic process has been recognized in SSc for >40 years, but drugs with demonstrable efficacy against SSc fibrosis in ameliorating the lung involvement have only recently been identified. Unfortunately, these treatments are ineffective at improving the skin score in patients with SSc. Previous clinical trials in SSc have largely focused on the cross-purposing of anti-inflammatory drugs and the use of immunosuppressive drugs from the transplantation field, which address inflammatory and/or autoimmune processes. Limited examination has taken place of specific anti-fibrotic agents developed through their ability to directly target the ECM in SSc by, for example, alleviating the persistent matrix stiffness and mechanotransduction that might be required for both the initiation and maintenance of fibrosis, including in SSc. However, because of the importance of the ECM in the SSc phenotype, attempts have now been made to identify drugs that specifically target the ECM, including some drugs that are currently under consideration for the treatment of cancer.

The advance of CCN3 in fibrosis

The extracellular matrix (ECM) is comprised of various extracellular macromolecules, including collagen, enzymes, and glycoproteins, which offer structural and biochemical support to neighboring cells. After tissue injury, extracellular matrix proteins deposit in the damaged tissue to promote tissue healing. However, an imbalance between ECM production and degradation can result in excessive deposition, leading to fibrosis and subsequent organ dysfunction. Acting as a regulatory protein within the extracellular matrix, CCN3 plays a crucial role in numerous biological processes, such as cell proliferation, angiogenesis, tumorigenesis, and wound healing. Many studies have demonstrated that CCN3 can reduce the production of ECM in tissues through diverse mechanisms thereby exerting an inhibitory effect on fibrosis. Consequently, CCN3 emerges as a promising therapeutic target for ameliorating fibrosis.

Myofibroblast Ccn3 is regulated by Yap and Wwtr1 and contributes to adverse cardiac outcomes

Introduction

While Yap and Wwtr1 regulate resident cardiac fibroblast to myofibroblast differentiation following cardiac injury, their role specifically in activated myofibroblasts remains unexplored.

Methods

We assessed the pathophysiological and cellular consequence of genetic depletion of Yap alone (Yap fl/fl ;Postn MCM ) or Yap and Wwtr1 (Yap fl/fl ;Wwtr1 fl/+ ;Postn MCM ) in adult mouse myofibroblasts following myocardial infarction and identify and validate novel downstream factors specifically in cardiac myofibroblasts that mediate pathological remodeling.

Results

Following myocardial infarction, depletion of Yap in myofibroblasts had minimal effect on heart function while depletion of Yap/Wwtr1 resulted in smaller scars, reduced interstitial fibrosis, and improved ejection fraction and fractional shortening. Single cell RNA sequencing of interstitial cardiac cells 7 days post infarction showed suppression of pro-fibrotic genes in fibroblasts derived from Yap fl/fl ,Wwtr1 fl/+ ;Postn MCM hearts. In vivo myofibroblast depletion of Yap/Wwtr1 as well in vitro knockdown of Yap/Wwtr1 dramatically decreased RNA and protein expression of the matricellular factor Ccn3. Administration of recombinant CCN3 to adult mice following myocardial infarction remarkably aggravated cardiac function and scarring. CCN3 administration drove myocardial gene expression of pro-fibrotic genes in infarcted left ventricles implicating CCN3 as a novel driver of cardiac fibrotic processes following myocardial infarction.

Discussion

Yap/Wwtr1 depletion in myofibroblasts attenuates fibrosis and significantly improves cardiac outcomes after myocardial infarction and we identify Ccn3 as a factor downstream of Yap/Wwtr1 that contributes to adverse cardiac remodeling post MI. Myofibroblast expression of Yap, Wwtr1, and Ccn3 could be further explored as potential therapeutic targets for modulating adverse cardiac remodeling post injury.

The matricellular protein CCN3 supports lung endothelial homeostasis and function

Aberrant vascular remodeling contributes to the progression of many aging-associated diseases, including idiopathic pulmonary fibrosis (IPF), where heterogeneous capillary density, endothelial transcriptional alterations, and increased vascular permeability correlate with poor disease outcomes. Thus, identifying disease-driving mechanisms in the pulmonary vasculature may be a promising strategy to limit IPF progression. Here, we identified Ccn3 as an endothelial-derived factor that is upregulated in resolving but not in persistent lung fibrosis in mice, and whose function is critical for vascular homeostasis and repair. Loss and gain of function experiments were carried out to test the role of CCN3 in lung microvascular endothelial function in vitro through RNAi and the addition of recombinant human CCN3 protein, respectively. Endothelial migration, permeability, proliferation, and in vitro angiogenesis were tested in cultured human lung microvascular endothelial cells (ECs). Loss of CCN3 in lung ECs resulted in transcriptional alterations along with impaired wound-healing responses, in vitro angiogenesis, barrier integrity as well as an increased profibrotic activity through paracrine signals, whereas the addition of recombinant CCN3 augmented endothelial function. Altogether, our results demonstrate that the matricellular protein CCN3 plays an important role in lung endothelial function and could serve as a promising therapeutic target to facilitate vascular repair and promote lung fibrosis resolution.

Molecular and Genetic Interactions between CCN2 and CCN3 behind Their Yin-Yang Collaboration

Cellular communication network factor (CCN) 2 and 3 are the members of the CCN family that conduct the harmonized development of a variety of tissues and organs under interaction with multiple biomolecules in the microenvironment. Despite their striking structural similarities, these two members show contrastive molecular functions as well as temporospatial emergence in living tissues. Typically, CCN2 promotes cell growth, whereas CCN3 restrains it. Where CCN2 is produced, CCN3 disappears. Nevertheless, these two proteins collaborate together to execute their mission in a yin–yang fashion. The apparent functional counteractions of CCN2 and CCN3 can be ascribed to their direct molecular interaction and interference over the cofactors that are shared by the two. Recent studies have revealed the mutual negative regulation systems between CCN2 and CCN3. Moreover, the simultaneous and bidirectional regulatory system of CCN2 and CCN3 is also being clarified. It is of particular note that these regulations were found to be closely associated with glycolysis, a fundamental procedure of energy metabolism. Here, the molecular interplay and metabolic gene regulation that enable the yin–yang collaboration of CCN2 and CCN3 typically found in cartilage development/regeneration and fibrosis are described.

The Emerging Roles of CCN3 Protein in Immune-Related Diseases

The CCN proteins are a family of extracellular matrix- (ECM-) associated proteins which currently consist of six secreted proteins (CCN1-6). CCN3 protein, also known as nephroblastoma overexpressed protein (NOV), is a member of the CCN family with multiple biological functions, implicated in major cellular processes such as cell growth, migration, and differentiation. Recently, CCN3 has emerged as a critical regulator in a variety of diseases, including immune-related diseases, including rheumatology arthritis, osteoarthritis, and systemic sclerosis. In this review, we will briefly introduce the structure and function of the CCN3 protein and summarize the roles of CCN3 in immune-related diseases, which is essential to understand the functions of the CCN3 in immune-related diseases.

Selective deletion of connective tissue growth factor attenuates experimentally-induced pulmonary fibrosis and pulmonary arterial hypertension

Connective tissue growth factor (CTGF, CCN2) is a matricellular protein which plays key roles in normal mammalian development and in tissue homeostasis and repair. In pathological conditions, dysregulated CCN2 has been associated with cancer, cardiovascular disease, and tissue fibrosis. In this study, genetic manipulation of the CCN2 gene was employed to investigate the role of CCN2 expression in vitro and in experimentally-induced models of pulmonary fibrosis and pulmonary arterial hypertension (PAH). Knocking down CCN2 using siRNA reduced expression of pro-fibrotic markers (fibronectin p < 0.01, collagen type I p < 0.05, α-SMA p < 0.0001, TIMP-1 p < 0.05 and IL-6 p < 0.05) in TGF-β-treated lung fibroblasts derived from systemic sclerosis patients. In vivo studies were performed in mice using a conditional gene deletion strategy targeting CCN2 in a fibroblast-specific and time-dependent manner in two models of lung disease. CCN2 deletion significantly reduced pulmonary interstitial scarring and fibrosis following bleomycin-instillation, as assessed by fibrotic scores (wildtype bleomycin 3.733 ± 0.2667 vs CCN2 knockout (KO) bleomycin 4.917 ± 0.3436, p < 0.05) and micro-CT. In the well-established chronic hypoxia/Sugen model of pulmonary hypertension, CCN2 gene deletion resulted in a significant decrease in pulmonary vessel remodelling, less right ventricular hypertrophy and a reduction in the haemodynamic measurements characteristic of PAH (RVSP and RV/LV + S were significantly reduced (p < 0.05) in CCN2 KO compared to WT mice in hypoxic/SU5416 conditions). These results support a prominent role for CCN2 in pulmonary fibrosis and in vessel remodelling associated with PAH. Therefore, therapeutics aimed at blocking CCN2 function are likely to benefit several forms of severe lung disease.

In vitro assessment of anti-fibrotic drug activity does not predict in vivo efficacy in murine models of Duchenne muscular dystrophy

AIM

Fibrosis is the most common complication from chronic diseases, and yet no therapy capable of mitigating its effects is available. Our goal is to unveil specific signaling regulating the fibrogenic process and to identify potential small molecule candidates that block fibrogenic differentiation of fibro/adipogenic progenitors.

METHOD

We performed a large-scale drug screen using muscle-resident fibro/adipogenic progenitors from a mouse model expressing EGFP under the Collagen1a1 promotor. We first confirmed that the EGFP was expressed in response to TGFβ1 stimulation in vitro. Then we treated cells with TGFβ1 alone or with drugs from two libraries of known compounds. The drugs ability to block the fibrogenic differentiation was quantified by imaging and flow cytometry. From a two-rounds screening, positive hits were tested in vivo in the mice model for the Duchenne Muscular Dystrophy (mdx mice). The histopathology of the muscles was assessed with picrosirius red (fibrosis) and laminin staining (myofiber size).

KEY FINDINGS

From the in vitro drug screening, we identified 21 drugs and tested 3 in vivo on the mdx mice. None of the three drugs significantly improved muscle histopathology.

SIGNIFICANCE

The in vitro drug screen identified various efficient compounds, none of them strongly inhibited fibrosis in skeletal muscle of mdx mice. To explain these observations, we hypothesize that in Duchenne Muscular Dystrophy, in which fibrosis is a secondary event due to chronic degeneration and inflammation, the drugs tested could have adverse effect on regeneration or inflammation, balancing off any positive effects and leading to the absence of significant results.

CCN Family Proteins in Cancer: Insight Into Their Structures and Coordination Role in Tumor Microenvironment

The crosstalk between tumor cells and the tumor microenvironment (TME), triggers a variety of critical signaling pathways and promotes the malignant progression of cancer. The success rate of cancer therapy through targeting single molecule of this crosstalk may be extremely low, whereas co-targeting multiple components could be complicated design and likely to have more side effects. The six members of cellular communication network (CCN) family proteins are scaffolding proteins that may govern the TME, and several studies have shown targeted therapy of CCN family proteins may be effective for the treatment of cancer. CCN protein family shares similar structures, and they mutually reinforce and neutralize each other to serve various roles that are tightly regulated in a spatiotemporal manner by the TME. Here, we review the current knowledge on the structures and roles of CCN proteins in different types of cancer. We also analyze CCN mRNA expression, and reasons for its diverse relationship to prognosis in different cancers. In this review, we conclude that the discrepant functions of CCN proteins in different types of cancer are attributed to diverse TME and CCN truncated isoforms, and speculate that targeting CCN proteins to rebalance the TME could be a potent anti-cancer strategy.

Transient ACE (Angiotensin-Converting Enzyme) Inhibition Suppresses Future Fibrogenic Capacity and Heterogeneity of Cardiac Fibroblast Subpopulations

Transient ACE (angiotensin-converting enzyme) inhibition in spontaneously hypertensive rats is known to protect against future injury-induced cardiac inflammation, fibrosis, and dysfunction; however, the mechanisms of protection have not been delineated. Here, we used single-cell RNA sequencing to test the hypothesis that transient ACE inhibitor treatment would induce a persistent shift in cardiac fibroblast subpopulations. Adult male spontaneously hypertensive rats (11 weeks old, hypertensive with cardiac hypertrophy) were treated for 2 weeks with an ACE inhibitor, enalapril (30 mg/kg per day, PO), or water (untreated spontaneously hypertensive rats) followed by a 2-week washout period (n=7/group). Cardiac fibroblasts were isolated from the left ventricle and subjected to single-cell RNA sequencing. Nine clusters of fibroblasts were identified, with 98% of cells in clusters 0 to 6. The transient treatment produced significant changes both within and across clusters. Cluster 1 depicted a highly fibrogenic gene profile, with cluster 6 serving as a gateway to cluster 1. Transient ACE inhibition depleted the gateway and expanded cluster 0, which was the least fibrogenic profile. Moreover, within cluster 1 fibroblasts, ACE inhibition reduced expression of individual fibrosis genes (eg, COL1A1, COL3A1, and FN1; all P<1×10-35). Clusters 2 to 5 reflected proliferative, moderately fibrogenic, translationally active, and less inflammatory subsets of fibroblasts, all of which exhibited attenuated fibrogenic gene expression after transient ACE inhibition. In conclusion, transient ACE inhibition shifts cardiac fibroblast subpopulations and degree of activation resulting in an overall reduced fibrogenic phenotype.

CCN2 (Cellular Communication Network factor 2) in the bone marrow microenvironment, normal and malignant hematopoiesis

CCN2, formerly termed Connective Tissue Growth Factor, is a protein belonging to the Cellular Communication Network (CCN)-family of secreted extracellular matrix-associated proteins. As a matricellular protein it is mainly considered to be active as a modifier of signaling activity of several different signaling pathways and as an orchestrator of their cross-talk. Furthermore, CCN2 and its fragments have been implicated in the regulation of a multitude of biological processes, including cell proliferation, differentiation, adhesion, migration, cell survival, apoptosis and the production of extracellular matrix products, as well as in more complex processes such as embryonic development, angiogenesis, chondrogenesis, osteogenesis, fibrosis, mechanotransduction and inflammation. Its function is complex and context dependent, depending on cell type, state of differentiation and microenvironmental context. CCN2 plays a role in many diseases, especially those associated with fibrosis, but has also been implicated in many different forms of cancer. In the bone marrow (BM), CCN2 is highly expressed in mesenchymal stem/stromal cells (MSCs). CCN2 is important for MSC function, supporting its proliferation, migration and differentiation. In addition, stromal CCN2 supports the maintenance and longtime survival of hematopoietic stem cells, and in the presence of interleukin 7, stimulates the differentiation of pro-B lymphocytes into pre-B lymphocytes. Overexpression of CCN2 is seen in the majority of B-acute lymphoblastic leukemias, especially in certain cytogenetic subgroups associated with poor outcome. In acute myeloid leukemia, CCN2 expression is increased in MSCs, which has been associated with leukemic engraftment in vivo. In this review, the complex function of CCN2 in the BM microenvironment and in normal as well as malignant hematopoiesis is discussed. In addition, an overview is given of data on the remaining CCN family members regarding normal and malignant hematopoiesis, having many similarities and some differences in their function.

Verteporfin inhibits the persistent fibrotic phenotype of lesional scleroderma dermal fibroblasts

Fibrosis is perpetuated by an autocrine, pro-adhesive signaling loop maintained by the synthetic and contractile abilities of myofibroblasts and the stiff, highly-crosslinked extracellular matrix. Transcriptional complexes that are exquisitely responsive to mechanotransduction include the co-activator YAP1, which regulates the expression of members of the CCN family of matricellular proteins such as CCN2 and CCN1. Although selective YAP1 inhibitors exist, the effect of these inhibitors on profibrotic gene expression in fibroblasts is largely unknown, and is the subject of our current study. Herein, we use genome-wide expression profiling, real-time polymerase chain reaction and Western blot analyses, cell migration and collagen gel contraction assays to assess the ability of a selective YAP inhibitor verteporfin (VP) to block fibrogenic activities in dermal fibroblasts from healthy individual human controls and those from isolated from fibrotic lesions of patients with diffuse cutaneous systemic sclerosis (dcSSc). In control fibroblasts, VP selectively reduced expression of fibrogenic genes and also blocked the ability of TGFbeta to induce actin stress fibers in dermal fibroblasts. VP also reduced the persistent profibrotic phenotype of dermal fibroblasts cultured from fibrotic lesions of patients with dcSSc. Our results are consistent with the notion that, in the future, YAP1 inhibitors may represent a novel, valuable method of treating fibrosis as seen in dcSSc.

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.

Connective Tissue Growth Factor: From Molecular Understandings to Drug Discovery

Connective tissue growth factor (CTGF) is a key signaling and regulatory molecule involved in different biological processes, such as cell proliferation, angiogenesis, and wound healing, as well as multiple pathologies, such as tumor development and tissue fibrosis. Although the underlying mechanisms of CTGF remain incompletely understood, a commonly accepted theory is that the interactions between different protein domains in CTGF and other various regulatory proteins and ligands contribute to its variety of functions. Here, we highlight the structure of each domain of CTGF and its biology functions in physiological conditions. We further summarized main diseases that are deeply influenced by CTGF domains and the potential targets of these diseases. Finally, we address the advantages and disadvantages of current drugs targeting CTGF and provide the perspective for the drug discovery of the next generation of CTGF inhibitors based on aptamers.

Calreticulin exploits TGF-β for extracellular matrix induction engineering a tissue regenerative process

Topical application of extracellular calreticulin (eCRT), an ER chaperone protein, in animal models enhances wound healing and induces tissue regeneration evidenced by epidermal appendage neogenesis and lack of scarring. In addition to chemoattraction of cells critical to the wound healing process, eCRT induces abundant neo-dermal extracellular matrix (ECM) formation by 3 days post-wounding. The purpose of this study was to determine the mechanisms involved in eCRT induction of ECM. In vitro, eCRT strongly induces collagen I, fibronectin, elastin, α-smooth muscle actin in human adult dermal (HDFs) and neonatal fibroblasts (HFFs) mainly via TGF-β canonical signaling and Smad2/3 activation; RAP, an inhibitor of LRP1 blocked eCRT ECM induction. Conversely, eCRT induction of α5 and β1 integrins was not mediated by TGF-β signaling nor inhibited by RAP. Whereas eCRT strongly induces ECM and integrin α5 proteins in K41 wild-type mouse embryo fibroblasts (MEFs), CRT null MEFs were unresponsive. The data show that eCRT induces the synthesis and release of TGF-β3 first via LRP1 or other receptor signaling and later induces ECM proteins via LRP1 signaling subsequently initiating TGF-β receptor signaling for intracellular CRT (iCRT)-dependent induction of TGF-β1 and ECM proteins. In addition, TGF-β1 induces 2-3-fold higher level of ECM proteins than eCRT. Whereas eCRT and iCRT converge for ECM induction, we propose that eCRT attenuates TGF-β-mediated fibrosis/scarring to achieve tissue regeneration.

Et tu, CCN1…

The CCN family of matricellular proteins are recognized bona fide targets for therapeutically targeting so-called chronic inflammatory diseases, including fibrosis and cancers. The majority of the work supporting this contention has been derived from examining CCN2, formerly, and unhelpfully, termed "connective tissue growth factor." Both CCN2, and its related protein, CCN1, formerly termed "cysteine-rich protein 61", are positively regulated by not only TGFbeta, but also by the hippo/YAP/TAZ mechanotransduction pathway that appears to drive these pathologies. Indeed, increasing evidence indicates that CCN1 also contributes to these fibrosis and cancers and, consequently, targeting both CCN2 and CCN1 simultaneously could be of therapeutic value. This commentary focuses on a recent, exciting paper (Ju et al., 2020, Scientific Reports, 10, 3201) suggesting that CCN1 is a target for non-alcoholic steatohepatitis (NASH).

Endogenous CCN family member WISP1 inhibits trauma-induced heterotopic ossification

Heterotopic ossification (HO) is defined as abnormal differentiation of local stromal cells of mesenchymal origin, resulting in pathologic cartilage and bone matrix deposition. Cyr61, CTGF, Nov (CCN) family members are matricellular proteins that have diverse regulatory functions on cell proliferation and differentiation, including the regulation of chondrogenesis. However, little is known regarding CCN family member expression or function in HO. Here, a combination of bulk and single-cell RNA sequencing defined the dynamic temporospatial pattern of CCN family member induction within a mouse model of trauma-induced HO. Among CCN family proteins, Wisp1 (also known as Ccn4) was most upregulated during the evolution of HO, and Wisp1 expression corresponded with chondrogenic gene profile. Immunohistochemistry confirmed WISP1 expression across traumatic and genetic HO mouse models as well as in human HO samples. Transgenic Wisp1LacZ/LacZ knockin animals showed an increase in endochondral ossification in HO after trauma. Finally, the transcriptome of Wisp1-null tenocytes revealed enrichment in signaling pathways, such as the STAT3 and PCP signaling pathways, that may explain increased HO in the context of Wisp1 deficiency. In sum, CCN family members, and in particular Wisp1, are spatiotemporally associated with and negatively regulate trauma-induced HO formation.

Conjunction junction, what's the function? CCN proteins as targets in fibrosis and cancers

Cellular communication network (CCN) proteins are matricellular proteins that coordinate signaling among extracellular matrix, secreted proteins, and cell surface receptors. Their specific in vivo function is context-dependent, but they play profound roles in pathological conditions, such as fibrosis and cancers. Anti-CCN therapies are in clinical consideration. Only recently, however, has the function of these complex molecules begun to emerge. This review summarizes and interprets our current knowledge regarding these fascinating molecules and provides experimental evidence for their utility as therapeutic targets.