Regulation of TGF-β Family Signaling by Inhibitory Smads

Inhibitory Smads suppress pancreatic stellate cell activation through negative feedback in chronic pancreatitis

Background

Activation of pancreatic stellate cells (PSCs) is a key cause of chronic pancreatitis (CP), while inhibition of transforming growth factor-β (TGF-β) signaling renders PSCs inactive. Inhibitory Smads (I-Smads) impede TGF-β intracellular signaling and may provide a way to alleviate CP. Thus, we aimed to investigate the molecular mechanism of I-Smads in CP animals and freshly-isolated PSCs.

Methods

Sixteen male C57BL/6 mice were randomly divided into two groups; a control group (treated with saline) and a CP group (treated with caerulein) for 6 weeks. Masson’s staining was performed to identify fibrosis, and immunohistochemistry (IHC) was performed to measure the levels of Smad6 between the two groups. An improved method derived from internal digestion was used to isolate PSCs from male Sprague Dawley rats. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunofluorescence staining were used to measure the messenger ribonucleic acid (mRNA) and protein levels of alpha-smooth muscle actin (α-SMA). Plasmids of I-Smads or SB431542 were transfected into freshly-isolated PSCs, and relative mRNA levels of marker genes were quantified by qRT-PCR. The two-tailed Student’s t-test was performed to assess significance.

Results

The Smad6 protein level was significantly higher in the pancreas tissue of CP mice compared to the control group. A large number of PSCs were isolated from rat pancreas using an improved isolating method and were confirmed by quiescent and active PSC markers including cluster differentiation antigen 133 (CD133), perilipin 2 (Plin2), α-SMA, Desmin, and collagen 1 (Col1). The mRNA levels of both Smad6 and Smad7 were down-regulated during freshly-isolated PSC activation. Over-expression of both Smad6 and Smad7 in freshly-isolated PSC reduced the mRNA level of α-SMA, glial fibrillary acidic protein (GFAP), Desmin, Col1, Col3, and fibronectin 1 (Fn1) significantly. SB431542 reduced the mRNA level of α-SMA, Col1, Col3, and Fn1 significantly in freshly-isolated PSCs.

Conclusions

This study demonstrated that CP promoted the expression of I-Smads, which suppressed the activation of freshly-isolated PSCs via a negative feedback loop.

Organ Fibrosis and Autoimmunity: The Role of Inflammation in TGFβ-Dependent EMT

Recent advances in our understanding of the molecular pathways that control the link of inflammation with organ fibrosis and autoimmune diseases point to the epithelial to mesenchymal transition (EMT) as the common association in the progression of these diseases characterized by an intense inflammatory response. EMT, a process in which epithelial cells are gradually transformed to mesenchymal cells, is a major contributor to the pathogenesis of fibrosis. Importantly, the chronic inflammatory microenvironment has emerged as a decisive factor in the induction of pathological EMT. Transforming growth factor-β (TGF-β), a multifunctional cytokine, plays a crucial role in the induction of fibrosis, often associated with chronic phases of inflammatory diseases, contributing to marked fibrotic changes that severely impair normal tissue architecture and function. The understanding of molecular mechanisms underlying EMT-dependent fibrosis has both a basic and a translational relevance, since it may be useful to design therapies aimed at counteracting organ deterioration and failure. To this end, we reviewed the recent literature to better elucidate the molecular response to inflammatory/fibrogenic signals in autoimmune diseases in order to further the specific regulation of EMT-dependent fibrosis in more targeted therapies.

Silencing Smad7 potentiates BMP2-induced chondrogenic differentiation and inhibits endochondral ossification in human synovial-derived mesenchymal stromal cells

BACKGROUND

Bone morphogenetic protein 2 (BMP2) is a promising chondrogenic growth factor for cartilage tissue-engineering, but it also induces robust endochondral ossification. Human synovial-derived mesenchymal stromal cells (hSMSCs) have attracted great interest due to their poor potential for differentiation into osteogenic lineages. Smad7 plays a significant in the endochondral ossification. In this study, we explored a new method to amplify the BMP2-induced chondrogenic differentiation of hSMSCs by downregulating Smad7 and applying a cellular scaffold.

METHODS

hSMSCs were isolated from human knee joint synovium from 3 donors through adhesion growth. In vitro and in vivo models of the chondrogenic differentiation of hSMSCs were established. Transgenic expression of BMP2 and silencing of Smad7 and Smad7 was achieved by adenoviral vectors. The osteogenic differentiation was detected by alkaline phosphatase staining, alizarin red staining, and RT-PCR analysis of the osteogenic genes RUNX2, Osterix, and Osteocalcin. The chondrogenic differentiation was detected by Alcian blue staining and RT-PCR analysis of the chondrogenic genes SOX9, COL2, and aggrecan. Hypertrophic differentiation was detected by the markers COL10 and MMP13. A subcutaneous stem cell implantation model was established with polyethylene glycol citrate-co-N-isopropylacrylamide (PPCN) scaffolds and athymic nude mice (3/group, 4-6 week-old female) and evaluated by micro-CT, H&E staining, and Alcian blue staining. An immunohistochemistry assay was used to detected COL1 and COL2, and an immunofluorescence assay was used to detect COL10 and MMP13.

RESULTS

These hSMSCs identified by flow cytometry. These hSMSCs exhibited lower osteo-differentiation potential than iMads and C3H10T1/2-cells. When Smad7 was silenced in BMP2-induced hSMSCs, the chondrogenic differentiation genes SOX9, COL2, and aggrecan were enhanced in vitro. Additionally, it silencing Smad7 led to a decrease in the hypertrophic differentiation genes COL10 and MMP13. In subcutaneous stem cell implantation assays, immunofluorescence and immunohistochemical staining demonstrated that silencing Smad7 increased the number of COL2-positive cells and decreased the expression of COL1, COL10, and MMP13.

CONCLUSION

This study suggests that the application of hSMSCs, cell scaffolds, and silencing Smad7 can potentiate BMP2-induced chondrogenic differentiation and inhibit endochondral ossification. Thus, inhibiting the expression of Smad7 in BMP2-induced hSMSC differentiation may be a new strategy for cartilage tissue-engineering.

Pivotal Role of TGF-β/Smad Signaling in Cardiac Fibrosis: Non-coding RNAs as Effectual Players

Unintended cardiac fibroblast proliferation in many pathophysiological heart conditions, known as cardiac fibrosis, results in pooling of extracellular matrix (ECM) proteins in the heart muscle. Transforming growth factor β (TGF-β) as a pivotal cytokine/growth factor stimulates fibroblasts and hastens ECM production in injured tissues. The TGF-β receptor is a heterodimeric receptor complex on the plasma membrane, made up from TGF-β type I, as well as type II receptors, giving rise to Smad2 and Smad3 transcription factors phosphorylation upon canonical signaling. Phosphorylated Smad2, Smad3, and cytoplasmic Smad4 intercommunicate to transfer the signal to the nucleus, culminating in provoked gene transcription. Additionally, TGF-β receptor complex activation starts up non-canonical signaling that lead to the mitogen-stimulated protein kinase cascade activation, inducing p38, JNK1/2 (c-Jun NH2-terminal kinase 1/2), and ERK1/2 (extracellular signal–regulated kinase 1/2) signaling. TGF-β not only activates fibroblasts and stimulates them to differentiate into myofibroblasts, which produce ECM proteins, but also promotes fibroblast proliferation. Non-coding RNAs (ncRNAs) are important regulators of numerous pathways along with cellular procedures. MicroRNAs and circular long ncRNAs, combined with long ncRNAs, are capable of affecting TGF-β/Smad signaling, leading to cardiac fibrosis. More comprehensive knowledge based on these processes may bring about new diagnostic and therapeutic approaches for different cardiac disorders.

Clinical and Molecular Insights in Erythropoiesis Regulation of Signal Transduction Pathways in Myelodysplastic Syndromes and β-Thalassemia

Erythropoiesis regulation is essential in normal physiology and pathology, particularly in myelodysplastic syndromes (MDS) and β-thalassemia. Several signaling transduction processes, including those regulated by inositides, are implicated in erythropoiesis, and the latest MDS or β-thalassemia preclinical and clinical studies are now based on their regulation. Among others, the main pathways involved are those regulated by transforming growth factor (TGF)-β, which negatively regulates erythrocyte differentiation and maturation, and erythropoietin (EPO), which acts on the early-stage erythropoiesis. Also small mother against decapentaplegic (SMAD) signaling molecules play a role in pathology, and activin receptor ligand traps are being investigated for future clinical applications. Even inositide-dependent signaling, which is important in the regulation of cell proliferation and differentiation, is specifically associated with erythropoiesis, with phospholipase C (PLC) and phosphatidylinositol 3-kinase (PI3K) as key players that are becoming increasingly important as new promising therapeutic targets. Additionally, Roxadustat, a new erythropoiesis stimulating agent targeting hypoxia inducible factor (HIF), is under clinical development. Here, we review the role and function of the above-mentioned signaling pathways, and we describe the state of the art and new perspectives of erythropoiesis regulation in MDS and β-thalassemia.

E3 Ubiquitin Ligases: Key Regulators of TGFβ Signaling in Cancer Progression

Transforming growth factor β (TGFβ) is a secreted growth and differentiation factor that influences vital cellular processes like proliferation, adhesion, motility, and apoptosis. Regulation of the TGFβ signaling pathway is of key importance to maintain tissue homeostasis. Perturbation of this signaling pathway has been implicated in a plethora of diseases, including cancer. The effect of TGFβ is dependent on cellular context, and TGFβ can perform both anti- and pro-oncogenic roles. TGFβ acts by binding to specific cell surface TGFβ type I and type II transmembrane receptors that are endowed with serine/threonine kinase activity. Upon ligand-induced receptor phosphorylation, SMAD proteins and other intracellular effectors become activated and mediate biological responses. The levels, localization, and function of TGFβ signaling mediators, regulators, and effectors are highly dynamic and regulated by a myriad of post-translational modifications. One such crucial modification is ubiquitination. The ubiquitin modification is also a mechanism by which crosstalk with other signaling pathways is achieved. Crucial effector components of the ubiquitination cascade include the very diverse family of E3 ubiquitin ligases. This review summarizes the diverse roles of E3 ligases that act on TGFβ receptor and intracellular signaling components. E3 ligases regulate TGFβ signaling both positively and negatively by regulating degradation of receptors and various signaling intermediates. We also highlight the function of E3 ligases in connection with TGFβ's dual role during tumorigenesis. We conclude with a perspective on the emerging possibility of defining E3 ligases as drug targets and how they may be used to selectively target TGFβ-induced pro-oncogenic responses.

SMAD4 mutations and cross-talk between TGF-β/IFNγ signaling accelerate rates of DNA damage and cellular senescence, resulting in a segmental progeroid syndrome-the Myhre syndrome

SMAD4 encodes a member of the SMAD family of proteins involved in the TGF-β signaling pathway. Potentially heritable, autosomal dominant, gain-of-function heterozygous variants of SMAD4 cause a rare developmental disorder, the Myhre syndrome, which is associated with a wide range of developmental and post-developmental phenotypes that we now characterize as a novel segmental progeroid syndrome. Whole-exome sequencing of a patient referred to our International Registry of Werner Syndrome revealed a heterozygous p.Arg496Cys variant of the SMAD4 gene. To investigate the role of SMAD4 mutations in accelerated senescence, we generated cellular models overexpressing either wild-type SMAD4 or mutant SMAD4-R496C in normal skin fibroblasts. We found that cells expressing the SMAD4-R496C mutant exhibited decreased proliferation and elevated expression of cellular senescence and inflammatory markers, including IL-6, IFNγ, and a TGF-β target gene, PAI-1. Here we show that transient exposure to TGF-β, an inflammatory cytokine, followed by chronic IFNγ stimulation, accelerated rates of senescence that were associated with increased DNA damage foci and SMAD4 expression. TGF-β, IFNγ, or combinations of both were not sufficient to reduce proliferation rates of fibroblasts. In contrast, TGF-β alone was able to induce preadipocyte senescence via induction of the mTOR protein. The mTOR inhibitor rapamycin mitigated TGF-β-induced expression of p21, p16, and DNA damage foci and improved replicative potential of preadipocytes, supporting the cell-specific response to this cytokine. These findings collectively suggest that persistent DNA damage and cross-talk between TGF-β/IFNγ pathways contribute to a series of molecular events leading to cellular senescence and a segmental progeroid syndrome.

Regulation and Signaling of TGF-β Autoinduction

Cell signaling is a vital part of biological life. It helps coordinating various cellular processes including cell survival, cell growth, cell death, and cell interaction with the microenvironment and other cells. In general, cell signaling involves the attachment of signaling molecules known as ligands to specific receptors on cell surface, which then activate downstream events that dictate the cell's response. One of the most studied ligands is transforming growth factor-beta (TGF-β). TGF-β signaling is mainly mediated by suppressor of mothers against decapentaplegic (Smad) proteins, but it also interacts with other pathways such as the Ras and mitogen-activated protein kinase (MAPK) signaling pathways. Furthermore, TGF-β can have a dual role depending on the cellular and microenvironmental context, in which it can act as either a growth promoter or a growth inhibitor. It has been known that TGF-β can self-induce its ligand production, thereby prolonging and amplifying its effect on cells and their microenvironment. The aim of this review is to discuss the regulation and signaling of TGF-β autoinduction, which still remain to be elucidated. Several factors have been found to facilitate TGF-β autoinduction, which include the activator protein-1 (AP1) complex, Smad3-dependent signaling, and non-Smad signaling pathways. On the other hand, the LIM (Lin11, Isl-1 and Mec-3) domain only 7 (LMO7) protein can suppress TGF-β autoinduction by interfering with the activities of AP-1 and Smad3. Since TGF-β autoinduction is implicated in various pathological conditions, better understanding of its regulation and signaling can provide new directions for therapy.

SMAD4 mutations identified in Iranian patients with colorectal cancer and polyp

AIM

Search for SMAD4 mutations in Colorectal cancer (CRC) or polyp in Iran.

BACKGROUND

Colorectal cancer is one of the five prevalent cancers among the Iranian population; however, its molecular mechanisms are not fully understood. The vast majority of CRCs arise from neoplastic polyp.

METHODS

Colorectal cancer and polyp lesions with matched normal tissues from patients who had undergone colonoscopy in Taleghani Hospital (January 2009 - November 2010) were included in the study. DNA extraction and PCR-sequencing for exons 5-11 of the SMAD-4 gene were carried out on 39 and 30 specimens of polyp and adenocarcinoma, respectively.

RESULTS

Of cancer and polyp specimens, 33.3% and 28.2%, respectively, were mutated in the Smad-4 gene. The majority of SMAD4 mutations, especially in the MH₂ domain were missense mutations (63.6% and 68.75, respectively). In cancer, codon 435 and in polyp, codons 435 and 399 were the most common alterations. Unlike cancer specimens, transversion was found frequently in the polyp (56.25% vs. 35.7%). CG>TA transition was about 18.75% and 14.3% in cancer and polyp samples, respectively. Mutations of codon 264 and C.483-4 were seen both in cancer and neoplastic polyps.

CONCLUSION

As frequent alterations, missense mutations are presumably selected during tumorigenesis and polyposis due to their structural impacts on SMAD4 functions and TGF-ß signaling pathway. The lower frequency of CG>TA can be attributed to global genome hypomethylation. Presumably, SMAD4 mutations had occurred in the primary polyps, and some of these mutated cells then developed into carcinoma. On the other hand, polyp-specific mutations may lower the risk of CRC.

BMP4 augments the survival of hepatocellular carcinoma (HCC) cells under hypoxia and hypoglycemia conditions by promoting the glycolysis pathway

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide although its pathogenic mechanism remains to be fully understood. Unlike normal cells, most cancer cells rely on aerobic glycolysis and are more adaptable to the microenvironment of hypoxia and hypoglycemia. Bone Morphogenetic Protein 4 (BMP4) plays important roles in regulating proliferation, differentiation, invasion and migration of HCC cells. We have recently shown that BMP4 plays an important role in regulating glucose metabolism although the effect of BMP4 on glucose metabolic reprogramming of HCC is poorly understood. In this study, we found that BMP4 was highly expressed in HCC tumor tissues, as well as HCC cell lines that were tolerant to hypoxia and hypoglycemia. Mechanistically, we demonstrated that BMP4 protected HCC cells from hypoxia and hypoglycemia by promoting glycolysis since BMP4 up-regulated glucose uptake, the lactic acid production, the ATP level, and the activities of rate limiting enzymes of glycolysis (including HK2, PFK and PK). Furthermore, we demonstrated that BMP4 up-regulated HK2, PFKFB3 and PKM2 through the canonical Smad signal pathway as SMAD5 directly bound to the promoter of PKM. Collectively, our findings shown that BMP4 may play an important role in regulating glycolysis of HCC cells under hypoxia and hypoglycemia condition, indicating that novel therapeutics may be developed to target BMP4-regulated glucose metabolic reprogramming in HCC.

Inhibition of FGF and TGF-β Pathways in hESCs Identify STOX2 as a Novel SMAD2/4 Cofactor

Simple Summary

Signaling pathways are the means by which cells and tissue communicate, orchestrating key events during mammalian development, homeostasis, and disease. During development, signaling determines the identity of cells, and thereby controls morphogenesis and organ specification. Depending on the cellular context, these pathways can exert a broad range of even opposing functions. This is achieved, among other mechanisms, by crosstalk between pathways. Here, we examined how two pathways (the transforming growth factor-β (TGF-β) and the fibroblast growth factor (FGF)) cooperate in the maintenance and cell fate specification of human embryonic stem cells. We used inhibitory molecules for individual pathways on a short time series and analyzed the resulting variation in gene expression. In contrast to our expectations, we did not observe an extended crosstalk between the pathway at the gene regulatory level. However, we discovered STOX2 as a new primary target of the TGF-β signaling pathway. Our results show that STOX2 might act as a novel TGF-β signaling co-factor. Our work will contribute to understand how signaling by the TGF-β is mediated. In the future, these results might help to deepen our understanding of how signaling is propagated.

Abstract

The fibroblast growth factor (FGF) and the transforming growth factor-β (TGF-β) pathways are both involved in the maintenance of human embryonic stem cells (hESCs) and regulate the onset of their differentiation. Their converging functions have suggested that these pathways might share a wide range of overlapping targets. Published studies have focused on the long-term effects (24–48 h) of FGF and TGF-β inhibition in hESCs, identifying direct and indirect target genes. In this study, we focused on the earliest transcriptome changes occurring between 3 and 9 h after FGF and TGF-β inhibition to identify direct target genes only. Our analysis clearly shows that only a handful of target transcripts are common to both pathways. This is surprising in light of the previous literature, and has implications for models of cell signaling in human pluripotent cells. In addition, we identified STOX2 as a novel primary target of the TGF-β signaling pathway. We show that STOX2 might act as a novel SMAD2/4 cofactor. Taken together, our results provide insights into the effect of cell signaling on the transcription profile of human pluripotent cells

The role of bone morphogenetic protein signaling in vascular calcification

Vascular calcification is associated with atherosclerosis, chronic kidney disease, and diabetes, and results from processes resembling endochondral or intramembranous ossification, or from processes that are distinct from ossification. Bone morphogenetic proteins (BMP), as well as other ligands, receptors, and regulators of the transforming growth factor beta (TGFβ) family regulate vascular and valvular calcification by modulating the phenotypic plasticity of multipotent progenitor lineages associated with the vasculature or valves. While osteogenic ligands BMP2 and BMP4 appear to be both markers and drivers of vascular calcification, particularly in atherosclerosis, BMP7 may serve to protect against calcification in chronic kidney disease. BMP signaling regulators such as matrix Gla protein and BMP-binding endothelial regulator protein (BMPER) play protective roles in vascular calcification. The effects of BMP signaling molecules in vascular calcification are context-dependent, tissue-dependent, and cell-type specific. Here we review the current knowledge on mechanisms by which BMP signaling regulates vascular calcification and the potential therapeutic implications.

A Functional SMAD2/3 Binding Site in the PEX11β Promoter Identifies a Role for TGFβ in Peroxisome Proliferation in Humans

In mammals, peroxisomes perform crucial functions in cellular metabolism, signaling and viral defense which are essential to the viability of the organism. Molecular cues triggered by changes in the cellular environment induce a dynamic response in peroxisomes, which manifests itself as a change in peroxisome number, altered enzyme levels and adaptations to the peroxisomal morphology. How the regulation of this process is integrated into the cell's response to different stimuli, including the signaling pathways and factors involved, remains unclear. Here, a cell-based peroxisome proliferation assay has been applied to investigate the ability of different stimuli to induce peroxisome proliferation. We determined that serum stimulation, long-chain fatty acid supplementation and TGFβ application all increase peroxisome elongation, a prerequisite for proliferation. Time-resolved mRNA expression during the peroxisome proliferation cycle revealed a number of peroxins whose expression correlated with peroxisome elongation, including the β isoform of PEX11, but not the α or γ isoforms. An initial map of putative regulatory motif sites in the respective promoters showed a difference between binding sites in PEX11α and PEX11β, suggesting that these genes may be regulated by distinct pathways. A functional SMAD2/3 binding site in PEX11β points to the involvement of the TGFβ signaling pathway in expression of this gene and thus peroxisome proliferation/dynamics in humans.

The glial-specific hypermethylated 3' untranslated region of histone deacetylase 1 may modulates several signal pathways in Alzheimer's disease

AIMS

Epigenetic regulation plays an important role in the progression of Alzheimer's disease (AD). Here, we identified differential methylation probes (DMP) and investigated their potential mechanistic roles in AD.

MAIN METHODS

DMPs were identified via bioinformatic analysis of GSE66351, which was made up with 106 AD samples and 84 control samples derived from three separate brain regions. Differentially expressed genes (DEGs) were analyzed based on GSE5281 comprising 45 control samples and 58 AD samples. Gene ontology (GO), gene set enrichment analysis (GSEA), and protein-protein interaction (PPI) were used to identify pathways and hub genes.

KEY FINDINGS

We found 9007 DMPs in Occipital Cortex glia, 1527 in OC neurons, 100 in Temporal Cortex, and 194 in Frontal Cortex. 74 DEGs were identified in Primary Visual Cortex, 67 of which were downregulated while seven upregulated. 482 were upregulated and 697 downregulated in medial temporal gyrus. In superior frontal gyrus, 687 were upregulated and 85 downregulated. GO and PPI revealed that pathways involving epithelial-cell differentiation, cellular responses to lipids, transcription corepressor activities, apoptotic and organ growth were modulated by histone deacetylase 1 (HDAC1) and associated with AD. Additionally, GSEA illustrated that the transforming growth factor beta signaling pathway was significantly enriched in some brain regions and HDAC1 played an important role in this pathway.

SIGNIFICANCE

We found the glial-specific 3'UTR of HDAC1 was hypermethylated and HDAC1 was overexpressed in AD patients. Moreover, we also speculate that HDAC1 triggered signaling pathways linked to many different biological processes and functions via the regulation of histone deacetylation.

The dichotomous role of TGF-β in controlling liver cancer cell survival and proliferation

Hepatocellular carcinoma (HCC) is the major form of primary liver cancer and one of the most prevalent and life-threatening malignancies globally. One of the hallmarks in HCC is the sustained cell survival and proliferative signals, which are determined by the balance between oncogenes and tumor suppressors. Transforming growth factor beta (TGF-β) is an effective growth inhibitor of epithelial cells including hepatocytes, through induction of cell cycle arrest, apoptosis, cellular senescence, or autophagy. The antitumorigenic effects of TGF-β are bypassed during liver tumorigenesis via multiple mechanisms. Furthermore, along with malignant progression, TGF-β switches to promote cancer cell survival and proliferation. This dichotomous nature of TGF-β is one of the barriers to therapeutic targeting in liver cancer. Thereafter, understanding the underlying molecular mechanisms is a prerequisite for discovering novel antitumor drugs that may specifically disable the growth-promoting branch of TGF-β signaling or restore its tumor-suppressive arm. This review summarizes how TGF-β inhibits or promotes liver cancer cell survival and proliferation, highlighting the functional switch mechanisms during the process.

Primary Ciliary Signaling in the Skin-Contribution to Wound Healing and Scarring

Primary cilia (PC) are solitary, post-mitotic, microtubule-based, and membrane-covered protrusions that are found on almost every mammalian cell. PC are specialized cellular sensory organelles that transmit environmental information to the cell. Signaling through PC is involved in the regulation of a variety of cellular processes, including proliferation, differentiation, and migration. Conversely, defective, or abnormal PC signaling can contribute to the development of various pathological conditions. Our knowledge of the role of PC in organ development and function is largely based on ciliopathies, a family of genetic disorders with mutations affecting the structure and function of PC. In this review, we focus on the role of PC in their major signaling pathways active in skin cells, and their contribution to wound healing and scarring. To provide comprehensive insights into the current understanding of PC functions, we have collected data available in the literature, including evidence across cell types, tissues, and animal species. We conclude that PC are underappreciated subcellular organelles that significantly contribute to both physiological and pathological processes of the skin development and wound healing. Thus, PC assembly and disassembly and PC signaling may serve as attractive targets for antifibrotic and antiscarring therapies.

Structural basis for inhibitory effects of Smad7 on TGF-β family signaling

Smad6 and Smad7 are classified as inhibitory Smads (I-Smads). They are crucial in the fine-tuning of signals by cytokines of the transforming growth factor-β (TGF-β) family. They are negative feedback regulators and principally target the activated type I receptors as well as the activated Smad complexes, but with distinct specificities. Smad7 inhibits Smad signaling from all seven type I receptors of the TGF-β family, whereas Smad6 preferentially inhibits Smad signaling from the bone morphogenetic protein (BMP) type I receptors, BMPR1A and BMPR1B. The target specificities are attributed to the C-terminal MH2 domain. Notably, Smad7 utilizes two alternative molecular surfaces for its inhibitory function against type I receptors. One is a basic groove composed of the first α-helix and the L3 loop, a structure that is shared with Smad6 and receptor-regulated Smads (R-Smads). The other is a three-finger-like structure (consisting of residues 331-361, 379-387, and the L3 loop) that is unique to Smad7. The underlying structural basis remains to be elucidated in detail. Here, we report the crystal structure of the MH2 domain of mouse Smad7 at 1.9 Å resolution. The three-finger-like structure is stabilized by a network of hydrogen bonds between residues 331-361 and 379-387, thus forming a molecular surface unique to Smad7. Furthermore, we discuss how Smad7 antagonizes the activated Smad complexes composed of R-Smad and Smad4, a common partner Smad.

The role of Smad signaling cascades in cardiac fibrosis

Most myocardial pathologic conditions are associated with cardiac fibrosis, the expansion of the cardiac interstitium through deposition of extracellular matrix (ECM) proteins. Although replacement fibrosis plays a reparative role after myocardial infarction, excessive, unrestrained or dysregulated myocardial ECM deposition is associated with ventricular dysfunction, dysrhythmias and adverse prognosis in patients with heart failure. The members of the Transforming Growth Factor (TGF)-β superfamily are critical regulators of cardiac repair, remodeling and fibrosis. TGF-βs are released and activated in injured tissues, bind to their receptors and transduce signals in part through activation of cascades involving a family of intracellular effectors the receptor-activated Smads (R-Smads). This review manuscript summarizes our knowledge on the role of Smad signaling cascades in cardiac fibrosis. Smad3, the best-characterized member of the family plays a critical role in activation of a myofibroblast phenotype, stimulation of ECM synthesis, integrin expression and secretion of proteases and anti-proteases. In vivo, fibroblast Smad3 signaling is critically involved in scar organization and exerts matrix-preserving actions. Although Smad2 also regulates fibroblast function in vitro, its in vivo role in rodent models of cardiac fibrosis seems more limited. Very limited information is available on the potential involvement of the Smad1/5/8 cascade in cardiac fibrosis. Dissection of the cellular actions of Smads in cardiac fibrosis, and identification of patient subsets with overactive or dysregulated myocardial Smad-dependent fibrogenic responses are critical for design of successful therapeutic strategies in patients with fibrosis-associated heart failure.

Cardiac fibrosis

Myocardial fibrosis, the expansion of the cardiac interstitium through deposition of extracellular matrix proteins, is a common pathophysiologic companion of many different myocardial conditions. Fibrosis may reflect activation of reparative or maladaptive processes. Activated fibroblasts and myofibroblasts are the central cellular effectors in cardiac fibrosis, serving as the main source of matrix proteins. Immune cells, vascular cells and cardiomyocytes may also acquire a fibrogenic phenotype under conditions of stress, activating fibroblast populations. Fibrogenic growth factors (such as transforming growth factor-β and platelet-derived growth factors), cytokines [including tumour necrosis factor-α, interleukin (IL)-1, IL-6, IL-10, and IL-4], and neurohumoral pathways trigger fibrogenic signalling cascades through binding to surface receptors, and activation of downstream signalling cascades. In addition, matricellular macromolecules are deposited in the remodelling myocardium and regulate matrix assembly, while modulating signal transduction cascades and protease or growth factor activity. Cardiac fibroblasts can also sense mechanical stress through mechanosensitive receptors, ion channels and integrins, activating intracellular fibrogenic cascades that contribute to fibrosis in response to pressure overload. Although subpopulations of fibroblast-like cells may exert important protective actions in both reparative and interstitial/perivascular fibrosis, ultimately fibrotic changes perturb systolic and diastolic function, and may play an important role in the pathogenesis of arrhythmias. This review article discusses the molecular mechanisms involved in the pathogenesis of cardiac fibrosis in various myocardial diseases, including myocardial infarction, heart failure with reduced or preserved ejection fraction, genetic cardiomyopathies, and diabetic heart disease. Development of fibrosis-targeting therapies for patients with myocardial diseases will require not only understanding of the functional pluralism of cardiac fibroblasts and dissection of the molecular basis for fibrotic remodelling, but also appreciation of the pathophysiologic heterogeneity of fibrosis-associated myocardial disease.

Beyond just a tight fortress: contribution of stroma to epithelial-mesenchymal transition in pancreatic cancer

Novel effective treatment is direly needed for patients with pancreatic ductal adenocarcinoma (PDAC). Therapeutics that target the driver mutations, especially the KRAS oncoprotein and its effector cascades, have been ineffective. It is increasing clear that the extensive fibro-inflammatory stroma (or desmoplasia) of PDAC plays an active role in the progression and therapeutic resistance of PDAC. The desmoplastic stroma is composed of dense extracellular matrix (ECM) deposited mainly by the cancer-associated-fibroblasts (CAFs) and infiltrated with various types of immune cells. The dense ECM functions as a physical barrier that limits tumor vasculatures and distribution of therapeutics to PDAC cells. In addition, mounting evidence have demonstrated that both CAFs and ECM promote PDAC cells aggressiveness through multiple mechanisms, particularly engagement of the epithelial-mesenchymal transition (EMT) program. Acquisition of a mesenchymal-like phenotype renders PDAC cells more invasive and resistant to therapy-induced apoptosis. Here, we critically review seminal and recent articles on the signaling mechanisms by which each stromal element promotes EMT in PDAC. We discussed the experimental models that are currently employed and best suited to study EMT in PDAC, which are instrumental in increasing the chance of successful clinical translation.

Chromatin accessibility dynamics of Chlamydia-infected epithelial cells

Chlamydia are Gram-negative, obligate intracellular bacterial pathogens responsible for a broad spectrum of human and animal diseases. In humans, Chlamydia trachomatis is the most prevalent bacterial sexually transmitted infection worldwide and is the causative agent of trachoma (infectious blindness) in disadvantaged populations. Over the course of its developmental cycle, Chlamydia extensively remodels its intracellular niche and parasitises the host cell for nutrients, with substantial resulting changes to the host cell transcriptome and proteome. However, little information is available on the impact of chlamydial infection on the host cell epigenome and global gene regulation. Regions of open eukaryotic chromatin correspond to nucleosome-depleted regions, which in turn are associated with regulatory functions and transcription factor binding. We applied formaldehyde-assisted isolation of regulatory elements enrichment followed by sequencing (FAIRE-Seq) to generate temporal chromatin maps of C. trachomatis-infected human epithelial cells in vitro over the chlamydial developmental cycle. We detected both conserved and distinct temporal changes to genome-wide chromatin accessibility associated with C. trachomatis infection. The observed differentially accessible chromatin regions include temporally-enriched sets of transcription factors, which may help shape the host cell response to infection. These regions and motifs were linked to genomic features and genes associated with immune responses, re-direction of host cell nutrients, intracellular signalling, cell-cell adhesion, extracellular matrix, metabolism and apoptosis. This work provides another perspective to the complex response to chlamydial infection, and will inform further studies of transcriptional regulation and the epigenome in Chlamydia-infected human cells and tissues.

Transforming Growth Factor-β: A Multifunctional Regulator of Cancer Immunity

Transforming growth factor-β (TGF-β) was originally identified as an anti-tumour cytokine. However, there is increasing evidence that it has important roles in the tumour microenvironment (TME) in facilitating cancer progression. TGF-β actively shapes the TME via modulating the host immunity. These actions are highly cell-type specific and complicated, involving both canonical and non-canonical pathways. In this review, we systemically update how TGF-β signalling acts as a checkpoint regulator for cancer immunomodulation. A better appreciation of the underlying pathogenic mechanisms at the molecular level can lead to the discovery of novel and more effective therapeutic strategies for cancer.

Transforming Growth Factor-β: A Multifunctional Regulator of Cancer Immunity

Simple Summary

Transforming growth factor beta (TGF-β) is a multifunctional cytokine that can restrict cancer onset but also promote cancer progression at late stages of cancer. The ability of TGF-β in producing diverse and sometimes opposing effects relies on its potential to control different cellular signalling and gene expression in distinct cell types, and environmental settings. The tumour promoting role of TGF-β is primarily mediated through its effects on the local tumour microenvironment (TME) of the cancer cells. In this review, we discuss the most recent research on the role and regulation of TGF-β, with a specific focus on its functions on promoting cancer progression through targeting different immune cells in the TME as well as its therapeutic perspectives.

Abstract

Transforming growth factor-β (TGF-β) was originally identified as an anti-tumour cytokine. However, there is increasing evidence that it has important roles in the tumour microenvironment (TME) in facilitating cancer progression. TGF-β actively shapes the TME via modulating the host immunity. These actions are highly cell-type specific and complicated, involving both canonical and non-canonical pathways. In this review, we systemically update how TGF-β signalling acts as a checkpoint regulator for cancer immunomodulation. A better appreciation of the underlying pathogenic mechanisms at the molecular level can lead to the discovery of novel and more effective therapeutic strategies for cancer.

Current perspectives on inhibitory SMAD7 in health and disease

Transforming growth factor β (TGF-β) family members play an extensive role in cellular communication that orchestrates both early development and adult tissue homeostasis. Aberrant TGF-β family signaling is associated with a pathological outcome in numerous diseases, and in-depth understanding of molecular and cellular processes could result in therapeutic benefit for patients. Canonical TGF-β signaling is mediated by receptor-regulated SMADs (R-SMADs), a single co-mediator SMAD (Co-SMAD), and inhibitory SMADs (I-SMADs). SMAD7, one of the I-SMADs, is an essential negative regulator of the pleiotropic TGF-β and bone morphogenetic protein (BMP) signaling pathways. In a negative feedback loop, SMAD7 inhibits TGF-β signaling by providing competition for TGF-β type-1 receptor (TβRI), blocking phosphorylation and activation of SMAD2. Moreover, SMAD7 recruits E3 ubiquitin SMURF ligases to the type I receptor to promote ubiquitin-mediated proteasomal degradation. In addition to its role in TGF-β and BMP signaling, SMAD7 is regulated by and implicated in a variety of other signaling pathways and functions as a mediator of crosstalk. This review is focused on SMAD7, its function in TGF-β and BMP signaling, and its role as a downstream integrator and crosstalk mediator. This crucial signaling molecule is tightly regulated by various mechanisms. We provide an overview of the ways by which SMAD7 is regulated, including noncoding RNAs (ncRNAs) and post-translational modifications (PTMs). Finally, we discuss its role in diseases, such as cancer, fibrosis, and inflammatory bowel disease (IBD).

Opposing and potentially antagonistic effects of BMP and TGF-β in multiple sclerosis: The "Yin and Yang" of neuro-immune Signaling

Bone Morphogenetic Proteins (BMP) and Transforming Growth Factor-beta (TGF-β) are cytokines with similar receptors and messengers. They are important for immune cell function, with BMPs exerting mainly proinflammatory but also anti-inflammatory effects, and TGF-β suppressing inflammation. Patients with Multiple Sclerosis exhibit BMP overactivity and suppressed TGF-β signaling. This dysregulated signaling participates in the crosstalk between infiltrating immune cells and glia, where BMP inhibits remyelination. Reciprocal antagonism between the two pathways takes place via a variety of mechanisms. Although this antagonism has not been studied in the setting of Multiple Sclerosis, it could inform further research and treatment discovery.

Influence of the TGF-β Superfamily on Osteoclasts/Osteoblasts Balance in Physiological and Pathological Bone Conditions

The balance between bone forming cells (osteoblasts/osteocytes) and bone resorbing cells (osteoclasts) plays a crucial role in tissue homeostasis and bone repair. Several hormones, cytokines, and growth factors-in particular the members of the TGF-β superfamily such as the bone morphogenetic proteins-not only regulate the proliferation, differentiation, and functioning of these cells, but also coordinate the communication between them to ensure an appropriate response. Therefore, this review focuses on TGF-β superfamily and its influence on bone formation and repair, through the regulation of osteoclastogenesis, osteogenic differentiation of stem cells, and osteoblasts/osteoclasts balance. After introducing the main types of bone cells, their differentiation and cooperation during bone remodeling and fracture healing processes are discussed. Then, the TGF-β superfamily, its signaling via canonical and non-canonical pathways, as well as its regulation by Wnt/Notch or microRNAs are described and discussed. Its important role in bone homeostasis, repair, or disease is also highlighted. Finally, the clinical therapeutic uses of members of the TGF-β superfamily and their associated complications are debated.

Receptor binding competition: A paradigm for regulating TGF-β family action

The transforming growth factor (TGF)-β family is a group of structurally related, multifunctional growth factors, or ligands that are crucially involved in the development, regulation, and maintenance of animal tissues. In humans, the family counts over 33 members. These secreted ligands typically form multimeric complexes with two type I and two type II receptors to activate one of two distinct signal transduction branches. A striking feature of the family is its promiscuity, i.e., many ligands bind the same receptors and compete with each other for binding to these receptors. Although several explanations for this feature have been considered, its functional significance has remained puzzling. However, several recent reports have promoted the idea that ligand-receptor binding promiscuity and competition are critical features of the TGF-β family that provide an essential regulating function. Namely, they allow a cell to read and process multi-ligand inputs. This capability may be necessary for producing subtle, distinctive, or adaptive responses and, possibly, for facilitating developmental plasticity. Here, we review the molecular basis for ligand competition, with emphasis on molecular structures and binding affinities. We give an overview of methods that were used to establish experimentally ligand competition. Finally, we discuss how the concept of ligand competition may be fundamentally tied to human physiology, disease, and therapy.

GAS5 protects against osteoporosis by targeting UPF1/SMAD7 axis in osteoblast differentiation

Osteoporosis is a common systemic skeletal disorder resulting in bone fragility and increased fracture risk. It is still necessary to explore its detailed mechanisms and identify novel targets for the treatment of osteoporosis. Previously, we found that a lncRNA named GAS5 in human could negatively regulate the lipoblast/adipocyte differentiation. However, it is still unclear whether GAS5 affects osteoblast differentiation and whether GAS5 is associated with osteoporosis. Our current research found that GAS5 was decreased in the bones and BMSCs, a major origin of osteoblast, of osteoporosis patients. Mechanistically, GAS5 promotes the osteoblast differentiation by interacting with UPF1 to degrade SMAD7 mRNA. Moreover, a decreased bone mass and impaired bone repair ability were observed in Gas5 heterozygous mice, manifesting in osteoporosis. The systemic supplement of Gas5-overexpressing adenoviruses significantly ameliorated bone loss in an osteoporosis mouse model. In conclusion, GAS5 promotes osteoblast differentiation by targeting the UPF1/SMAD7 axis and protects against osteoporosis.

Non-hormonal mediators of uterine fibroid growth

PURPOSE OF REVIEW

Uterine fibroids are the most common benign neoplasms of the female reproductive tract and one of the major public health concerns. Although most women with uterine fibroids are asymptomatic, over 30% of them will present with varying symptoms. This review focuses on the role of non-hormonal mediators and pathways in uterine fibroid biology. Furthermore, it provides data regarding the most recent findings in the field of compounds, which use those non-hormonal pathways in the medical therapy of uterine fibroids.

RECENT FINDINGS

Complex signaling pathway alterations are crucial for uterine fibroid development. The topic of the pathophysiology of uterine fibroids focuses mostly on steroids and other hormones. However, other very important pathways exist, and some of them are independent of hormones. Some of the most important pathways, which are non-hormonal, but in some cases still hormone-depended, include growth factors, cytokines and inflammation, Smad proteins, wingless type/β-catenin and others.

SUMMARY

Much more is known about hormonal than about non-hormonal signaling in uterine fibroids. Growth factors, early life exposure and inflammation are key factors in uterine fibroid biology. Numerous agents depend on those pathways and may find their place in the current and future therapy of uterine fibroids.

Genetics of renovascular hypertension in children

OBJECTIVE

In most cases of renovascular hypertension in children, the cause is unclear. The aim of this study was to investigate genetic variation as a factor in the development of renovascular hypertension in children.

METHODS

In a cohort of 37 unrelated children from a single tertiary referral center, exome sequencing was performed. We assessed variants in recognized and suspected disease genes and searched for novel ones with a gene-based variant-burden analysis.

RESULTS

In the majority of patients, exome sequencing could not identify causative variants. We found a pathogenic variant in a recognized associated disease gene in five patients (three pathogenic variants in NF1, one in ELN and a deletion of chromosome 7q11.23, consistent with Williams syndrome). In two other patients, (likely) pathogenic variants were found in putative renovascular hypertension genes (SMAD6 and GLA), with clinical implications for both. Ten additional patients carried variants of uncertain significance (VUS) in known (n = 4) or putative (n = 6) renovascular hypertension disease genes. Rare variant burden analysis yielded no further candidate genes.

CONCLUSION

Genetic contributors, such as germline mutations in NF1, ELN, 7q11.23del were present in only 5 out of 37 (14%) children with renovascular hypertension. Twelve other children (32%) had potentially causal variants identified, including a pathogenic variant in SMAD6; a vasculopathy gene hitherto unknown to link with renovascular hypertension. Most importantly, our data show that exome sequencing can rarely identify the cause of renovascular hypertension in nonsyndromic children. We suggest that nongenetic factors or somatic genetic variation will play a more important role.

Biological basis for efficacy of activin receptor ligand traps in myelodysplastic syndromes

Signaling by the TGF-β superfamily is important in the regulation of hematopoiesis and is dysregulated in myelodysplastic syndromes (MDSs), contributing to ineffective hematopoiesis and clinical cytopenias. TGF-β, activins, and growth differentiation factors exert inhibitory effects on red cell formation by activating canonical SMAD2/3 pathway signaling. In this Review, we summarize evidence that overactivation of SMAD2/3 signaling pathways in MDSs causes anemia due to impaired erythroid maturation. We also describe the basis for biological activity of activin receptor ligand traps, novel fusion proteins such as luspatercept that are promising as erythroid maturation agents to alleviate anemia and related comorbidities in MDSs and other conditions characterized by impaired erythroid maturation.

The Relationship Between Single Nucleotide Polymorphisms of SMAD3/SMAD6 and Risk of Esophageal Squamous Cell Carcinoma in Chinese Population

Background

The TGF-β signal pathways play a key role in the development and promotion of squamous cell carcinoma (SCC). The pathway is mediated by the SMAD family proteins that include SMAD3 and SMAD6. Our study aimed to evaluate the relationship between single nucleotide polymorphism (SNP) of SMAD3/SMAD6 and susceptibility to esophageal squamous cell carcinoma (ESCC) in the Chinese population.

Patients and Methods

This was a hospital-based case-control study compromised of 1043 ESCC patients and 1315 non-cancer patients. Seven SMAD3/SMAD6 (rs8028147, rs3743343, rs3743342, rs8025774, rs8031440, rs803167, and rs34643453) SNPs were selected and used to evaluate their correlation with ESCC susceptibility. Genetic model tests, stratified analyses, linkage disequilibrium analyses, and haplotype analyses were performed in our study.

Results

Participants with SMAD3 rs3743342 C>T, rs8025774 C>T, rs8031440 G>A or rs8031627 G>A had a significantly higher risk of ESCC. This was more evident in males, older patients (>63 years), smokers, and non-alcohol drinking participants. Linkage disequilibrium analyses further revealed that there were strong correlations between SMAD3 rs3743342 C>T, rs8025774 C>T, rs8031440 G>A, and rs8031627 G>A. In the same line, haplotype analyses revealed that SMAD3 ACCCGGSMAD6A and SMAD3AGCCGGSMAD6A were associated with less susceptibility to ESCC while SMAD3ATTTAASMAD6A was associated with a higher risk of ESCC.

Conclusion

SNPs of SMAD3 were related to higher susceptibility to ESCC. As such, they may contribute to the development of viable strategies for early diagnosis and treatment of ESCC. However, more detailed association mechanisms between SMAD3/SMAD6 SNPs and ESCC need further experiments to prove.

Protective effect of trimetazidine in radiation-induced cardiac fibrosis in mice

Radiation-induced heart damage is a serious side effect caused by radiotherapy, especially during the treatment of cancer near the chest. Trimetazidine is effective at reducing inflammation in the heart, but how it affects radiation-induced cardiac fibrosis (RICF) is unknown. To investigate the potential effect and molecular mechanism, we designed this project with a C57BL6 male mouse model supposing trimetazidine could inhibit RICF in mice. During the experiment, mice were randomly divided into six groups including a control group (Con), radiation-damaged model group (Mod) and four experimental groups receiving low-dose (10 mg/kg/day) or high-dose (20 mg/kg/day) trimetazidine before or after radiation treatment. Apart from the control group, all mice chests were exposed to 6 MV X-rays at a single dose of 20 Gy to induce RICF, and tissue analysis was done at 8 weeks after irradiation. Fibroblast or interstitial tissues and cardiac fibrosis-like characteristics were determined using haematoxylin and eosin and Masson staining, which can be used to assess myocardial fibrosis. Immunohistochemical analysis and RT-PCR were used to determine gene expression and study the molecular mechanism. As a result, this study suggests that trimetazidine inhibits RICF by reducing gene expression related to myocyte apoptosis and fibrosis formation, i.e. connective tissue growth factor (CTGF), transforming growth factor (TGF)-β1, smad2 and smad3. In conclusion, by regulating the CTGF/TGF-β1/Smad pathway, trimetazidine could be a prospective drug for clinical treatment of RICF.

Bone morphogenic proteins in iron homeostasis

The bone morphogenetic protein (BMP)-SMAD signaling pathway plays a central role in regulating hepcidin, which is the master hormone governing systemic iron homeostasis. Hepcidin is produced by the liver and acts on the iron exporter ferroportin to control iron absorption from the diet and iron release from body stores, thereby providing adequate iron for red blood cell production, while limiting the toxic effects of excess iron. BMP6 and BMP2 ligands produced by liver endothelial cells bind to BMP receptors and the coreceptor hemojuvelin (HJV) on hepatocytes to activate SMAD1/5/8 signaling, which directly upregulates hepcidin transcription. Most major signals that influence hepcidin production, including iron, erythropoietic drive, and inflammation, intersect with the BMP-SMAD pathway to regulate hepcidin transcription. Mutation or inactivation of BMP ligands, BMP receptors, HJV, SMADs or other proteins that modulate the BMP-SMAD pathway result in hepcidin dysregulation, leading to iron-related disorders, such as hemochromatosis and iron refractory iron deficiency anemia. Pharmacologic modulators of the BMP-SMAD pathway have shown efficacy in pre-clinical models to regulate hepcidin expression and treat iron-related disorders. This review will discuss recent insights into the role of the BMP-SMAD pathway in regulating hepcidin to control systemic iron homeostasis.

SMAD6 variants in craniosynostosis: genotype and phenotype evaluation

PURPOSE

Enrichment of heterozygous missense and truncating SMAD6 variants was previously reported in nonsyndromic sagittal and metopic synostosis, and interaction of SMAD6 variants with a common polymorphism nearBMP2 (rs1884302) was proposed to contribute to inconsistent penetrance. We determined the occurrence of SMAD6 variants in all types of craniosynostosis, evaluated the impact of different missense variants on SMAD6 function, and tested independently whether rs1884302 genotype significantly modifies the phenotype.

METHODS

We performed resequencing of SMAD6 in 795 unsolved patients with any type of craniosynostosis and genotyped rs1884302 in SMAD6-positive individuals and relatives. We examined the inhibitory activity and stability of SMAD6 missense variants.

RESULTS

We found 18 (2.3%) different rare damaging SMAD6 variants, with the highest prevalence in metopic synostosis (5.8%) and an 18.3-fold enrichment of loss-of-function variants comparedwith gnomAD data (P < 10-7). Combined with eight additional variants, ≥20/26 were transmitted from an unaffected parent but rs1884302 genotype did not predict phenotype.

CONCLUSION

Pathogenic SMAD6 variants substantially increase the risk of both nonsyndromic and syndromic presentations of craniosynostosis, especially metopic synostosis. Functional analysis is important to evaluate missense variants. Genotyping of rs1884302 is not clinically useful. Mechanisms to explain the remarkable diversity of phenotypes associated with SMAD6 variants remain obscure.

Endothelial-to-Mesenchymal Transition: Role in Cardiac Fibrosis

Endothelial-to-mesenchymal transition (EndMT) is a complex biological process by which endothelial cells lose their endothelial cell characteristics and acquire mesenchymal cell properties under certain physiological or pathological conditions. Recently, it has been found that EndMT plays an important role in the occurrence and development of fibrotic cardiovascular diseases. In this review, we first summarize the main induction pathways involved in EndMT process. In addition, we discuss the role of EndMT in fibrotic cardiovascular diseases and its potential implication in new therapeutic interventions.

Targeting Smad-Mediated TGFß Pathway in Coronary Artery Bypass Graft

Revascularization surgeries such as coronary artery bypass grafting (CABG) are sometimes necessary to manage coronary heart disease (CHD). However, more than half of these surgeries fail within 10 years due to the development of intimal hyperplasia (IH) among others. The cytokine transforming growth factor-beta (TGFß) and its signaling components have been found to be upregulated in diseased or injured vessels, and to promote IH after grafting. Interventions that globally inhibit TGFß in CABG have yielded contrasting outcomes in in vitro and in vivo studies including clinical trials. With advances in molecular biology, it becomes clear that TGFß exhibits both protective and damaging roles, and only specific components such as some Smad-dependent TGFß signaling mediate vascular IH. The activin receptor-like kinase (ALK)-mediated Smad-dependent TGFß signaling pathways have been found to be activated in human vascular smooth muscle cells (VSMCs) following injury and in hyperplastic preimplantation vein grafts. It appears that focused targeting of TGFß pathway constitutes a promising therapeutic target to improve the outcome of CABG. This study dissects the role of TGFß pathway in CABG failure, with particular emphasis on the therapeutic potentials of specific targeting of Smad-dependent and ALK-mediated signaling.

TGFβ as a gatekeeper of BMP action in the developing growth plate

The ligands that comprise the Transforming Growth Factor β superfamily highly govern the development of the embryonic growth plate. Members of this superfamily activate canonical TGFβ and/or BMP (Bone Morphogenetic Protein) signaling pathways. How these pathways interact with one another is an area of active investigation. These two signaling pathways have been described to negatively regulate one another through crosstalk involving Smad proteins, the primary intracellular effectors of canonical signaling. More recently, a mechanism for regulation of the BMP pathway through TGFβ and BMP receptor interactions has been described. Here in this review, we demonstrate examples of how TGFβ is a gatekeeper of BMP action in the developing growth plate at both the receptor and transcriptional levels.

The myofibroblast at a glance

In 1971, Gabbiani and co-workers discovered and characterized the “modification of fibroblasts into cells which are capable of an active spasm” (contraction) in rat wound granulation tissue and, accordingly, named these cells ‘myofibroblasts’. Now, myofibroblasts are not only recognized for their physiological role in tissue repair but also as cells that are key in promoting the development of fibrosis in all organs. In this Cell Science at a Glance and the accompanying poster, we provide an overview of the current understanding of central aspects of myofibroblast biology, such as their definition, activation from different precursors, the involved signaling pathways and most widely used models to study their function. Myofibroblasts will be placed into context with their extracellular matrix and with other cell types communicating in the fibrotic environment. Furthermore, the challenges and strategies to target myofibroblasts in anti-fibrotic therapies are summarized to emphasize their crucial role in disease progression.

The effective role of sodium copper chlorophyllin on the dysfunction of bone marrow mesenchymal stem cells in multiple myeloma via regulating TGF-β1

BACKGROUND

The osteoblast differentiation of bone marrow-derived stem cells (BMSCs) is impaired in multiple myeloma (MM). We investigated the effects of sodium copper chlorophyllin (SCC) on osteoblast differentiation ability of BMSCs from MM.

METHODS

Clinical bone marrow samples were collected. Fluorescence Activated Cell Sorter (FACS) was used to identify surface markers of BMSCs. BMSCs were treated with different concentrations of SCC and cell viability was detected by MTT assay. Relative mRNA and protein expressions of transforming growth factor-β1 (TGF-β1), SMAD2/3, osteogenic differentiation indicators (RUNX2 and OCN) were measured by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. Alkaline phosphatase (ALP) was stained for activity detection. Formation of calcium nodus of BMSCs was examined by Alizarin Red S staining.

RESULTS

CD90 and CD105 were high-expressed, but CD34 and CD45 were not expressed in BMSCs. BMSCs in MM group showed a lower expression of TGF-β1 and a lower degree of osteogenic differentiation. SCC enhanced activities of BMSCs, ALP activity, and formation of calcium nodus, activated TGF-β1, SMAD2/3 pathway and increased RUNX2 and OCN expressions in BMSCs. Silencing TGF-β1 reversed the effects of SCC on BMSCs in MM.

CONCLUSION

SCC could effectively improve the proliferation and osteogenic differentiation of BMSCs in MM through regulating TGF-β1.

RGFP966, a histone deacetylase 3 inhibitor, promotes glioma stem cell differentiation by blocking TGF-β signaling via SMAD7

Glioma stem cells (GSC) play a major role in drug resistance and tumor recurrence. Using a genetic screen with a set of shRNAs that can target chromatin regulators in a GSC model, we have HDAC3 as a major negative regulator of GSC differentiation. Inhibition of HDAC3 using a pharmacological inhibitor or a siRNA led to the induction of GSC differentiation into astrocytes. Consequently, HDAC3-inhibition also caused a strong reduction of tumor-promoting and self-renewal capabilities of GSCs. These phenotypes were highly associated with an increased acetylation of SMAD7, which protected its ubiquitination. SMAD7 inhibits a TGF-β signaling axis that is required for maintaining stemness. These results demonstrate that HDAC3 appears to be a proper target in anti-glioma therapy.

Current potential therapeutic strategies targeting the TGF-β/Smad signaling pathway to attenuate keloid and hypertrophic scar formation

Aberrant scar formation, which includes keloid and hypertrophic scars, is associated with a pathological disorganized wound healing process with chronic inflammation. The TGF-β/Smad signaling pathway is the most canonical pathway through which the formation of collagen in the fibroblasts and myofibroblasts is regulated. Sustained activation of the TGF-β/Smad signaling pathway results in the long-term overactivation of fibroblasts and myofibroblasts, which is necessary for the excessive collagen formation in aberrant scars. There are two categories of therapeutic strategies that aim to target the TGF-β/Smad signaling pathway in fibroblasts and myofibroblasts to interfere with their cellular functions and reduce cell proliferation. The first therapeutic strategy includes medications, and the second strategy is composed of genetic and cellular therapeutics. Therefore, the focus of this review is to critically evaluate these two main therapeutic strategies that target the TGF-β/Smad pathway to attenuate abnormal skin scar formation.

RAC1B Induces SMAD7 via USP26 to Suppress TGFβ1-Dependent Cell Migration in Mesenchymal-Subtype Carcinoma Cells

The small GTPase RAC1B has been shown to act as a powerful inhibitor of the transforming growth factor (TGF)β type I receptor ALK5 and TGFβ1/ALK5-induced epithelial–mesenchymal transition and cell motility. However, the precise mechanism has remained elusive. RNAi-mediated knockdown of RAC1B in the pancreatic ductal adenocarcinoma (PDAC)-derived cell line Panc1 failed to alter transcriptional activity from a transfected ALK5 promoter–reporter construct. In contrast, pharmacological inhibition of the proteasome decreased the abundance of ALK5 protein in cell lines of the mesenchymal subtype (Panc1, IMIM-PC-1, and breast cancer MDA-MB-231), but not in a PDAC cell line of the epithelial subtype (Colo357). Here, we focused on the inhibitory Smad protein, SMAD7, as a potential candidate for RAC1B-mediated inhibition of cell migration. In Panc1 cells devoid of RAC1B, SMAD7 protein was dramatically reduced and these cells were refractory to TGFβ1-induced upregulation of SMAD7 protein but not mRNA expression. Intriguingly, RNAi-mediated knockdown or ectopic overexpression of SMAD7 in Panc1 cells up- or downregulated, respectively, ALK5 protein expression and mimicked the suppressive effect of RAC1B on TGFβ/SMAD3-dependent transcriptional activity, target gene expression and cell migration. Transfection of SMAD7 was further able to partially rescue cells from the RAC1B knockdown-mediated increase in migratory properties. Conversely, knockdown of SMAD7 was able to partially rescue Panc1 and MDA-MB-231 cells from the antimigratory effect of ectopically expressed RAC1B. Finally, we demonstrate that RAC1B upregulation of SMAD7 protein requires intermittent transcriptional induction of the deubiquitinating enzyme USP26. Our data suggest that RAC1B induces SMAD7 by promoting its deubiquitination and establishes this Smad as one of RAC1B’s downstream effectors in negative regulation of ALK5 and TGFβ1-induced cell migration in mesenchymal-type carcinoma cells.

Dual role of TGF-β in early pregnancy: clues from tumor progression

TGF-β signaling in the endometrium is active during the implantation period and has a pivotal role in regulating endometrial receptivity and embryo implantation. During embryo implantation, both apoptosis and proliferation of endometrial cells happen at the same time and it seems TGF-β is the factor that controls both of these processes. As shown in cancer cells, in special conditions this cytokine can have a dual effect and switch the action from apoptosis to proliferation. Owing to the similarity between embryo implantation and cancer development and also unusual pattern of proliferation and remodeling in the uterus, in this review we suggest the existence of such a switching in endometrium during the early pregnancy. Moreover, we address some potential mechanisms that could regulate the switching. A better understanding of the molecular mechanisms regulating TGF-β action and signaling during the implantation period could pave the way for introducing novel therapeutic strategies in order to solve implantation-associated issues such as repeated implantation failure.

BMP9 is a potential therapeutic agent for use in oral and maxillofacial bone tissue engineering

Oral and maxillofacial surgery is often challenging due to defective bone healing owing to the microbial environment of the oral cavity, the additional involvement of teeth and esthetic concerns. Insufficient bone volume as a consequence of aging and some oral and maxillofacial surgical procedures, such as tumor resection of the jaw, may further impact facial esthetics and cause the failure of certain procedures, such as oral and maxillofacial implantation. Bone morphogenetic protein (BMP) 9 (BMP9) is one of the most effective BMPs to induce the osteogenic differentiation of different stem cells. A large cross-talk network that includes the BMP9, Wnt/β, Hedgehog, EGF, TGF-β and Notch signaling pathways finely regulates osteogenesis induced by BMP9. Epigenetic control during BMP9-induced osteogenesis is mainly dependent on histone deacetylases (HDACs), microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), which adds another layer of complexity. As a result, all these factors work together to orchestrate the molecular and cellular events underlying BMP9-related tissue engineering. In this review, we summarize our current understanding of the SMAD-dependent and SMAD-independent BMP9 pathways, with a particular focus on cross-talk and cross-regulation between BMP9 and other major signaling pathways in BMP9-induced osteogenesis. Furthermore, recently discovered epigenetic regulation of BMP9 pathways and the molecular and cellular basis of the application of BMP9 in tissue engineering in current oral and maxillofacial surgery and other orthopedic-related clinical settings are also discussed.

Transforming growth factor-β1 in intrauterine adhesion

Intrauterine adhesion (IUA), led by trauma to the basal layer, can prevent the endometrium from growing, resulting in complications in females, such as infertility and amenorrhea. Transforming growth factor-β1 (TGF-β1) plays a crucial role in inducing and promoting the differentiation and proliferation of mesenchymal cells, in the secretion of extracellular matrix-associated components, and is a major cytokine in initiating and terminating tissue repair downstream of the TGF-β/Smad signaling pathway. Some evidence supports that TGF-β1 is closely associated with the occurrence and development of IUA, and is regarded as an early risk factor of disease recurrence. Furthermore, the role of TGF-β1 has been demonstrated to be potentially regulated by a variety of cytokines, hormones, enzymes, and microRNAs. This review provides an overview of the expression, function, and regulation of TGF-β1 in IUA, with a brief discussion and perspectives on its future clinical implications on the diagnosis and treatment of IUA.

The role of cytokine and immune responses in intestinal fibrosis

The rapidly increasing incidence of inflammatory bowel disease (IBD) in South America, eastern Europe, Asia, and Africa has resulted in a global public health challenge. Intestinal fibrosis is a common complication in patients with long-term IBD, which may develop into stenosis and subsequent obstruction. Hitherto, the origin of IBD is unclear and several factors may be involved, including genetic, immune, environmental and microbial influences. Little is known about how the recurrent inflammation in patients with IBD develops into intestinal fibrosis and currently, there is no suitable treatment to reverse intestinal fibrosis in these patients. Here, we review the role of immune components in the pathogenesis of IBD and intestinal fibrosis, including cytokine networks, host-microbiome interactions, and immune cell trafficking.