Platelet-derived growth factor β-receptor, transforming growth factor β type I receptor, and CD44 protein modulate each other's signaling and stability

A Multifunctional Therapeutic Strategy Using P7C3 as A Countermeasure Against Bone Loss and Fragility in An Ovariectomized Rat Model of Postmenopausal Osteoporosis

By 2060, an estimated one in four Americans will be elderly. Consequently, the prevalence of osteoporosis and fragility fractures will also increase. Presently, no available intervention definitively prevents or manages osteoporosis. This study explores whether Pool 7 Compound 3 (P7C3) reduces progressive bone loss and fragility following the onset of ovariectomy (OVX)-induced osteoporosis. Results confirm OVX-induced weakened, osteoporotic bone together with a significant gain in adipogenic body weight. Treatment with P7C3 significantly reduced osteoclastic activity, bone marrow adiposity, whole-body weight gain, and preserved bone area, architecture, and mechanical strength. Analyses reveal significantly upregulated platelet derived growth factor-BB and leukemia inhibitory factor, with downregulation of interleukin-1 R6, and receptor activator of nuclear factor kappa-B (RANK). Together, proteomic data suggest the targeting of several key regulators of inflammation, bone, and adipose turnover, via transforming growth factor-beta/SMAD, and Wingless-related integration site/be-catenin signaling pathways. To the best of the knowledge, this is first evidence of an intervention that drives against bone loss via RANK. Metatranscriptomic analyses of the gut microbiota show P7C3 increased Porphyromonadaceae bacterium, Candidatus Melainabacteria, and Ruminococcaceae bacterium abundance, potentially contributing to the favorable inflammatory, and adipo-osteogenic metabolic regulation observed. The results reveal an undiscovered, and multifunctional therapeutic strategy to prevent the pathological progression of OVX-induced bone loss.

Tobacco Smoke Condensate Induces Morphologic Changes in Human Papillomavirus-Positive Cervical Epithelial Cells Consistent with Epithelial to Mesenchymal Transition (EMT) with Activation of Receptor Tyrosine Kinases and Regulation of TGFB

High-risk human papillomavirus (HR-HPV; HPV-16) and cigarette smoking are associated with cervical cancer (CC); however, the underlying mechanism(s) remain unclear. Additionally, the carcinogenic components of tobacco have been found in the cervical mucus of women smokers. Here, we determined the effects of cigarette smoke condensate (CSC; 3R4F) on human ectocervical cells (HPV-16 Ect/E6E7) exposed to CSC at various concentrations (10-6-100 μg/mL). We found CSC (10-3 or 10 μg/mL)-induced proliferation, enhanced migration, and histologic and electron microscopic changes consistent with EMT in ectocervical cells with a significant reduction in E-cadherin and an increase in the vimentin expression compared to controls at 72 h. There was increased phosphorylation of receptor tyrosine kinases (RTKs), including Eph receptors, FGFR, PDGFRA/B, and DDR2, with downstream Ras/MAPK/ERK1/2 activation and upregulation of common EMT-related genes, TGFB SNAI2, PDGFRB, and SMAD2. Our study demonstrated that CSC induces EMT in ectocervical cells with the upregulation of EMT-related genes, expression of protein biomarkers, and activation of RTKs that regulate TGFB expression, and other EMT-related genes. Understanding the molecular pathways and environmental factors that initiate EMT in ectocervical cells will help delineate molecular targets for intervention and define the role of EMT in the initiation and progression of cervical intraepithelial neoplasia and CC.

A new approach of nano-metformin as a protector against radiation-induced cardiac fibrosis and inflammation via CXCL1/TGF-Β pathway

The present work investigates the potential role of metformin nanoparticles (MTF-NPs) as a radio-protector against cardiac fibrosis and inflammation induced by gamma radiation via CXCL1/TGF-β pathway. Lethal dose fifty of nano-metformin was determined in mice, then 21 rats (male albino) were equally divided into three groups: normal control (G1), irradiated control (G2), and MTF-NPs + IRR (G3). The possible protective effect of MTF-NPs is illustrated via decreasing cardiac contents of troponin, C-X-C motif Ligand 1 (CXCL1), tumor growth factor β (TGF-β), protein kinase B (AKT), and nuclear factor-κB (NF-κB). Also, the positive effect of MTF-NPs on insulin-like growth factor (IGF) and platelet-derived growth factor (PDGF) in heart tissues using immunohistochemical technique is illustrated in the present study. Histopathological examination emphasizes the biochemical findings. The current investigation suggests that MTF-NPs might be considered as a potent novel treatment for the management of cardiac fibrosis and inflammation in patients who receive radiotherapy or workers who may be exposed to gamma radiation.

Transforming growth factor-β receptors: versatile mechanisms of ligand activation

Transforming growth factor-β (TGF-β) signaling is initiated by activation of transmembrane TGF-β receptors (TGFBR), which deploys Smad2/3 transcription factors to control cellular responses. Failure or dysregulation in the TGF-β signaling pathways leads to pathological conditions. TGF-β signaling is regulated at different levels along the pathways and begins with the liberation of TGF-β ligand from its latent form. The mechanisms of TGFBR activation display selectivity to cell types, agonists, and TGF-β isoforms, enabling precise control of TGF-β signals. In addition, the cell surface compartments used to release active TGF-β are surprisingly vibrant, using thrombospondins, integrins, matrix metalloproteinases and reactive oxygen species. The scope of TGFBR activation is further unfolded with the discovery of TGFBR activation initiated by other signaling pathways. The unique combination of mechanisms works in series to trigger TGFBR activation, which can be explored as therapeutic targets. This comprehensive review provides valuable insights into the diverse mechanisms underpinning TGFBR activation, shedding light on potential avenues for therapeutic exploration.

The Superior Effect of Radiofrequency With Targeted Ultrasound for Facial Rejuvenation by Inducing Hyaluronic Acid Synthesis: A Pilot Preclinical Study

Background

The level of dermal hyaluronic acid (HA) can be depleted by 75% at age 70. HA provides dermal hydration, volume, and thickness, making it a major component of the extracellular matrix. Restoration of dermal and epidermal HA can be achieved by combining radiofrequency (RF) energy and targeted ultrasound (TUS). The monopolar RF generates heat, with the TUS stimulating HA production. The heat induces a regenerative response in the skin, increasing the fibroblast activity and producing various extracellular matrix compounds, including HA.

Objectives

To investigate the effect of the simultaneous application of RF + TUS or RF + US on the stimulation of HA production.

Methods

Twelve animals underwent 4 treatments. Six were treated with transcutaneous RF + TUS and 6 with the combination RF + US. The opposite untreated side served as a control. Punch biopsies of the skin were taken at baseline, immediately posttreatment, 1 month, and 2 months posttreatment. The tissue was evaluated with real-time quantitative polymerase chain reaction (RT-qPCR), matrix-assisted laser desorption (MALDI) and time of flight (TOF), and confocal microscopy.

Results

The RT-qPCR focused on assessing the production of has1 and has2, enzymes responsible for HA synthesis. RT-qPCR results of the RF + TUS group revealed a +98% and +45% increase in hyaluronic synthetase (HAS) 1 and HAS2 production after the treatments, respectively. The MALDI-TOF revealed a +224% increase in measured HA 2 months after the treatments. The changes were also visible in the confocal microscopy. The control group showed no significant (P > .05) results in either of the evaluation methods.

Conclusions

Concurrent application of RF and TUS significantly enhances the natural regenerative processes in skin tissue.

Level of Evidence 5

CD44 acts as a coreceptor for cell-specific enhancement of signaling and regulatory T cell induction by TGM1, a parasite TGF-β mimic

Long-lived parasites evade host immunity through highly evolved molecular strategies. The murine intestinal helminth, Heligmosomoides polygyrus, down-modulates the host immune system through release of an immunosuppressive TGF-β mimic, TGM1, which is a divergent member of the CCP (Sushi) protein family. TGM1 comprises 5 domains, of which domains 1-3 (D1/2/3) bind mammalian TGF-β receptors, acting on T cells to induce Foxp3+ regulatory T cells; however, the roles of domains 4 and 5 (D4/5) remain unknown. We noted that truncated TGM1, lacking D4/5, showed reduced potency. Combination of D1/2/3 and D4/5 as separate proteins did not alter potency, suggesting that a physical linkage is required and that these domains do not deliver an independent signal. Coprecipitation from cells treated with biotinylated D4/5, followed by mass spectrometry, identified the cell surface protein CD44 as a coreceptor for TGM1. Both full-length and D4/5 bound strongly to a range of primary cells and cell lines, to a greater degree than D1/2/3 alone, although some cell lines did not respond to TGM1. Ectopic expression of CD44 in nonresponding cells conferred responsiveness, while genetic depletion of CD44 abolished enhancement by D4/5 and ablated the ability of full-length TGM1 to bind to cell surfaces. Moreover, CD44-deficient T cells showed attenuated induction of Foxp3 by full-length TGM1, to levels similar to those induced by D1/2/3. Hence, a parasite protein known to bind two host cytokine receptor subunits has evolved a third receptor specificity, which serves to raise the avidity and cell type-specific potency of TGF-β signaling in mammalian cells.

Pharmacology and Rationale for Seralutinib in the Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a complex disorder characterized by vascular remodeling and a consequent increase in pulmonary vascular resistance. The histologic hallmarks of PAH include plexiform and neointimal lesions of the pulmonary arterioles, which are composed of dysregulated, apoptosis-resistant endothelial cells and myofibroblasts. Platelet-derived growth factor receptors (PDGFR) α and β, colony stimulating factor 1 receptor (CSF1R), and mast/stem cell growth factor receptor kit (c-KIT) are closely related kinases that have been implicated in PAH progression. In addition, emerging data indicate significant crosstalk between PDGF signaling and the bone morphogenetic protein receptor type 2 (BMPR2)/transforming growth factor β (TGFβ) receptor axis. This review will discuss the importance of the PDGFR-CSF1R-c-KIT signaling network in PAH pathogenesis, present evidence that the inhibition of all three nodes in this kinase network is a potential therapeutic approach for PAH, and highlight the therapeutic potential of seralutinib, currently in development for PAH, which targets these pathways.

Inhaled seralutinib exhibits potent efficacy in models of pulmonary arterial hypertension

BACKGROUND

Signalling through platelet-derived growth factor receptor (PDGFR), colony-stimulating factor 1 receptor (CSF1R) and mast/stem cell growth factor receptor kit (c-KIT) plays a critical role in pulmonary arterial hypertension (PAH). We examined the preclinical efficacy of inhaled seralutinib, a unique small-molecule PDGFR/CSF1R/c-KIT kinase inhibitor in clinical development for PAH, in comparison to a proof-of-concept kinase inhibitor, imatinib.

METHODS

Seralutinib and imatinib potency and selectivity were compared. Inhaled seralutinib pharmacokinetics/pharmacodynamics were studied in healthy rats. Efficacy was evaluated in two rat models of PAH: SU5416/Hypoxia (SU5416/H) and monocrotaline pneumonectomy (MCTPN). Effects on inflammatory/cytokine signalling were examined. PDGFR, CSF1R and c-KIT immunohistochemistry in rat and human PAH lung samples and microRNA (miRNA) analysis in the SU5416/H model were performed.

RESULTS

Seralutinib potently inhibited PDGFRα/β, CSF1R and c-KIT. Inhaled seralutinib demonstrated dose-dependent inhibition of lung PDGFR and c-KIT signalling and increased bone morphogenetic protein receptor type 2 (BMPR2). Seralutinib improved cardiopulmonary haemodynamic parameters and reduced small pulmonary artery muscularisation and right ventricle hypertrophy in both models. In the SU5416/H model, seralutinib improved cardiopulmonary haemodynamic parameters, restored lung BMPR2 protein levels and decreased N-terminal pro-brain natriuretic peptide (NT-proBNP), more than imatinib. Quantitative immunohistochemistry in human lung PAH samples demonstrated increased PDGFR, CSF1R and c-KIT. miRNA analysis revealed candidates that could mediate seralutinib effects on BMPR2.

CONCLUSIONS

Inhaled seralutinib was an effective treatment of severe PAH in two animal models, with improved cardiopulmonary haemodynamic parameters, a reduction in NT-proBNP, reverse remodelling of pulmonary vascular pathology and improvement in inflammatory biomarkers. Seralutinib showed greater efficacy compared to imatinib in a preclinical study.

A Promising Candidate in Tendon Healing Events—PDGF-BB

Tendon injuries are one of the most common musculoskeletal disorders for which patients seek medical aid, reducing not only the quality of life of the patient but also imposing a significant economic burden on society. The administration of growth factors at the wound site is a feasible solution for enhancing tendon healing. Platelet-derived growth factor-BB (PDGF-BB) has a well-defined safety profile compared to other growth factors and has been approved by the Food and Drug Administration (FDA). The purpose of this review is to summarize the role of PDGF-BB in tendon healing through a comprehensive review of the published literature. Experimental studies suggest that PDGF-BB has a positive effect on tendon healing by enhancing inflammatory responses, speeding up angiogenesis, stimulating tendon cell proliferation, increasing collagen synthesis and increasing the biomechanics of the repaired tendon. PDGF-BB is regarded as a promising candidate in tendon healing. However, in order to realize its full potential, we still need to carefully consider and study key issues such as dose and application time in the future, so as to explore further applications of PDGF-BB in the tendon healing process.

Development of a Novel Anti-CD44 Monoclonal Antibody for Multiple Applications against Esophageal Squamous Cell Carcinomas

CD44 is a cell surface glycoprotein, which is expressed on normal cells, and overexpressed on cancer cells. CD44 is involved in cell adhesion, migration, proliferation, survival, stemness, and chemo-resistance. Therefore, CD44 is thought to be a promising target for cancer diagnosis and therapy. In this study, we established anti-CD44 monoclonal antibodies (mAbs) by immunizing mice with a CD44 variant (CD44v3-10) ectodomain and screening using enzyme-linked immunosorbent assay. We then characterized them using flow cytometry, Western blotting, and immunohistochemistry. One of the established clones (C₄₄Mab-46; IgG₁, kappa) reacted with CD44 standard isoform (CD44s)-overexpressed Chinese hamster ovary-K1 cells (CHO/CD44s) or esophageal squamous cell carcinoma (ESCC) cell lines (KYSE70 and KYSE770). The apparent K_D of C₄₄Mab-46 for CHO/CD44s, KYSE70, and KYSE770 was 1.1 × 10^-8 M, 4.9 × 10^-8 M, and 4.1 × 10^-8 M, respectively. C₄₄Mab-46 detected CD44s of CHO/CD44s and KYSE70, and CD44 variants of KYSE770 in Western blot analysis. Furthermore, C₄₄Mab-46 strongly stained the formalin-fixed paraffin-embedded ESCC tissues in immunohistochemistry. Collectively, C₄₄Mab-46 is very useful for detecting CD44 in various applications.

Characterisation of PDGF-BB:PDGFRβ signalling pathways in human brain pericytes: evidence of disruption in Alzheimer's disease

Platelet-derived growth factor-BB (PDGF-BB):PDGF receptor-β (PDGFRβ) signalling in brain pericytes is critical to the development, maintenance and function of a healthy blood-brain barrier (BBB). Furthermore, BBB impairment and pericyte loss in Alzheimer’s disease (AD) is well documented. We found that PDGF-BB:PDGFRβ signalling components were altered in human AD brains, with a marked reduction in vascular PDGFB. We hypothesised that reduced PDGF-BB:PDGFRβ signalling in pericytes may impact on the BBB. We therefore tested the effects of PDGF-BB on primary human brain pericytes in vitro to define pathways related to BBB function. Using pharmacological inhibitors, we dissected distinct aspects of the PDGF-BB response that are controlled by extracellular signal-regulated kinase (ERK) and Akt pathways. PDGF-BB promotes the proliferation of pericytes and protection from apoptosis through ERK signalling. In contrast, PDGF-BB:PDGFRβ signalling through Akt augments pericyte-derived inflammatory secretions. It may therefore be possible to supplement PDGF-BB signalling to stabilise the cerebrovasculature in AD.

Smyth et al. use tissue microarrays from Alzheimer’s disease (AD) patient brains to show that PDGF-BB:PDGFRβ signalling components are reduced in AD. They then use primary human brain pericytes to elucidate a pathway by which PDGF-BB:PDGFRβ signalling in brain pericytes is disrupted in AD, thus impairing the blood brain barrier.

TORREY, a Phase 2 study to evaluate the efficacy and safety of inhaled seralutinib for the treatment of pulmonary arterial hypertension

Aberrant kinase signaling that involves platelet-derived growth factor receptor (PDGFR) α/β, colony stimulating factor 1 receptor (CSF1R), and stem cell factor receptor (c-KIT) pathways may be responsible for vascular remodeling in pulmonary arterial hypertension. Targeting these specific pathways may potentially reverse the pathological inflammation, cellular proliferation, and fibrosis associated with pulmonary arterial hypertension progression. Seralutinib (formerly known as GB002) is a novel, potent, clinical stage inhibitor of PDGFRα/β, CSF1R, and c-KIT delivered via inhalation that is being developed for patients with pulmonary arterial hypertension. Here, we report on an ongoing Phase 2 randomized, double-blind, placebo-controlled trial (NCT04456998) evaluating the efficacy and safety of seralutinib in subjects with World Health Organization Group 1 Pulmonary Hypertension who are classified as Functional Class II or III. A total of 80 subjects will be enrolled and randomized to receive either study drug or placebo for 24 weeks followed by an optional 72-week open-label extension study. The primary endpoint is the change from baseline to Week 24 in pulmonary vascular resistance by right heart catheterization. The secondary endpoint is the change in distance from baseline to Week 24 achieved in the 6-min walk test. A computerized tomography sub-study will examine the effect of seralutinib on pulmonary vascular remodelling. A separate heart rate monitoring sub-study will examine the effect of seralutinib on cardiac effort during the 6-min walk test.

Smad2 inhibition of MET transcription potentiates human vascular smooth muscle cell apoptosis

Background:

Vascular smooth muscle cell (SMC) apoptosis is involved in major cardiovascular diseases. Smad2 is a transcription factor implicated in aortic aneurysm. The molecular mediators of Smad2-driven SMC apoptosis are not well defined. Here we have identified a Smad2-directed mechanism involving MET and FAS, both encoding cell membrane signaling receptors.

Methods and results:

Guided by microarray analysis in human primary aortic SMCs, loss/gain-of-function (siRNA/overexpression) indicated that Smad2 negatively and positively regulated, respectively, the gene expression of Met which was identified herein as anti-apoptotic and that of Fas, a known pro-apoptotic factor. While co-immunoprecipitation suggested a physical association of Smad2 with p53, chromatin immunoprecipitation followed by quantitative PCR revealed their co-occupancy in the same region of the MET promoter. Activating p53 with nutlin3a further potentiated the suppression of MET promoter-dependent luciferase activity and the exacerbation of SMC apoptosis that were caused by Smad2 overexpression. These results indicated that Smad2 in SMCs repressed the transcription of MET by cooperating with p53, and that Smad2 also activated FAS, a target gene of its transcription factor activity.

Conclusions:

Our study suggests a pro-apoptotic mechanism in human SMCs, whereby Smad2 negatively and positively regulates MET and FAS, genes encoding anti-apoptotic and pro-apoptotic factors, respectively.

Regenerative cross talk between cardiac cells and macrophages

Aside from the first week postnatal, murine heart regeneration is restricted and responses to damage follow classic fibrotic remodeling. Recent transcriptomic analyses have suggested that significant cross talk with the sterile immune response could maintain a more embryonic-like signaling network that promotes acute, transient responses. However, with age, this response-likely mediated by neonatal yolk sac macrophages-then transitions to classical macrophage-mediated, cardiac fibroblast (CF)-based remodeling of the extracellular matrix (ECM) after myocardial infarction (MI). The molecular mechanisms that govern the change with age and drive fibrosis via inflammation are poorly understood. Using multiple ribonucleic acid sequencing (RNA-Seq) datasets, we attempt to resolve the relative contributions of CFs and macrophages in the bulk-healing response of regenerative (postnatal day 1) and nonregenerative hearts (postnatal day 8+). We performed an analysis of bulk RNA-Seq datasets from myocardium and cardiac fibroblasts as well as a single-cell RNA-Seq dataset from cardiac macrophages. MI-specific pathway differences revealed that nonregenerative hearts generated more ECM and had larger matricellular responses correlating with inflammation, produced greater chemotactic gradients to recruit macrophages, and expressed receptors for danger-associated molecular patterns at higher levels than neonates. These changes could result in elevated stress-response pathways compared with neonates, converging at NF-κB and activator protein-1 (AP-1) signaling. Profibrotic gene programs, which greatly diverge on day 3 post MI, lay the foundation for chronic fibrosis, and thus postnatal hearts older than 7 days typically exhibit significantly less regeneration. Our analyses suggest that the macrophage ontogenetic shift in the heart postnatally could result in detrimental stress signaling that suppresses regeneration.NEW & NOTEWORTHY Immediately postnatal mammalian hearts are able to regenerate after infarction, but the cells, pathways, and molecules that regulate this behavior are unclear. By comparing RNA-Seq datasets from regenerative mouse hearts and older, nonregenerative hearts, we are able to identify biological processes that are hallmarks of regeneration. We find that sterile inflammatory processes are upregulated in nonregenerative hearts, initiating profibrotic gene programs 3 days after myocardial infarction that can cause myocardial disease.

The Secreted Protein C10orf118 Is a New Regulator of Hyaluronan Synthesis Involved in Tumour-Stroma Cross-Talk

Simple Summary

Hyaluronan is a main glycosaminoglycan in extracellular matrix with an important role in breast cancer progression. Alterations in its synthesis and size may affect tu-mour growth and metastasis. Communication between stromal and breast cancer cells consists of the secretion of factors that provoke a series of cell signalling that influence cell fate and tis-sue microenvironment, by favouring tumour cell survival and motility. Here, we present the c10orf118 protein expressed in high amounts by breast tumour cells as a new regulator in hya-luronan synthesis. This protein is found both in Golgi and secreted in the extracellular matrix, whereas its role is still unknown. The secreted c10orf118 is found to induce hyaluronan synthase 2 in normal fibroblasts. Importantly, high expression of c10orf118 is positively correlated to pa-tient’s survival and to a low metastasis.

Abstract

Interaction between cancer cells and their microenvironment is central in defining the fate of cancer development. Tumour cells secrete signals (cytokines, chemokines, growth factors) that modify the surrounding area, while the niche supplies structures and activities necessary for tumour maintenance and growth. Hyaluronan (HA) is a glycosaminoglycan that constitute cancer cell niche and is known to influence tumour functions such as proliferation, migration and neoangiogenesis. The knowledge of the factors regulating HA synthesis and size is crucial in understanding the mechanisms sustaining tumour development. Here we show that a yet uncharacterized protein secreted by breast tumour cell lines, named c10orf118 (accession number NM_018017 in NCBI/BLAST, and Q7z3E2 according to the Uniprot identifier), with a predicted length of 898 amino acids, can induce the secretion of HA by stromal fibroblasts through the up-regulation of the hyaluronan synthase 2 gene (HAS2). Intracellularly, this protein is localized in the Golgi apparatus with a possible role in vesicle maturation and transport. The expression of c10orf118 was verified in breast cancer patient specimens and was found to be associated with the presence of estrogen receptor that characterizes a good patient survival. We suggest c10orf118 as a new player that influences the HA amount in breast cancer microenvironment and is associated with low aggressiveness of cancer.

TRAF4/6 Is Needed for CD44 Cleavage and Migration via RAC1 Activation

The hyaluronan receptor CD44 can undergo proteolytic cleavage in two steps, leading to the release of its intracellular domain; this domain is translocated to the nucleus, where it affects the transcription of target genes. We report that CD44 cleavage in A549 lung cancer cells and other cells is promoted by transforming growth factor-beta (TGFβ) in a manner that is dependent on ubiquitin ligase tumor necrosis factor receptor-associated factor 4 or 6 (TRAF4 or TRAF6, respectively). Stem-like A549 cells grown in spheres displayed increased TRAF4-dependent expression of CD44 variant isoforms, CD44 cleavage, and hyaluronan synthesis. Mechanistically, TRAF4 activated the small GTPase RAC1. CD44-dependent migration of A549 cells was inhibited by siRNA-mediated knockdown of TRAF4, which was rescued by the transfection of a constitutively active RAC1 mutant. Our findings support the notion that TRAF4/6 mediates pro-tumorigenic effects of CD44, and suggests that inhibitors of CD44 signaling via TRAF4/6 and RAC1 may be beneficial in the treatment of tumor patients.

A guide to the composition and functions of the extracellular matrix

Extracellular matrix (ECM) is a dynamic 3-dimensional network of macromolecules that provides structural support for the cells and tissues. Accumulated knowledge clearly demonstrated over the last decade that ECM plays key regulatory roles since it orchestrates cell signaling, functions, properties and morphology. Extracellularly secreted as well as cell-bound factors are among the major members of the ECM family. Proteins/glycoproteins, such as collagens, elastin, laminins and tenascins, proteoglycans and glycosaminoglycans, hyaluronan, and their cell receptors such as CD44 and integrins, responsible for cell adhesion, comprise a well-organized functional network with significant roles in health and disease. On the other hand, enzymes such as matrix metalloproteinases and specific glycosidases including heparanase and hyaluronidases contribute to matrix remodeling and affect human health. Several cell processes and functions, among them cell proliferation and survival, migration, differentiation, autophagy, angiogenesis, and immunity regulation are affected by certain matrix components. Structural alterations have been also well associated with disease progression. This guide on the composition and functions of the ECM gives a broad overview of the matrisome, the major ECM macromolecules, and their interaction networks within the ECM and with the cell surface, summarizes their main structural features and their roles in tissue organization and cell functions, and emphasizes the importance of specific ECM constituents in disease development and progression as well as the advances in molecular targeting of ECM to design new therapeutic strategies.

Induction of muscle-regenerative multipotent stem cells from human adipocytes by PDGF-AB and 5-azacytidine

Terminally differentiated murine osteocytes and adipocytes can be reprogrammed using platelet-derived growth factor-AB and 5-azacytidine into multipotent stem cells with stromal cell characteristics. We have now optimized culture conditions to reprogram human adipocytes into induced multipotent stem (iMS) cells and characterized their molecular and functional properties. Although the basal transcriptomes of adipocyte-derived iMS cells and adipose tissue-derived mesenchymal stem cells were similar, there were changes in histone modifications and CpG methylation at cis-regulatory regions consistent with an epigenetic landscape that was primed for tissue development and differentiation. In a non-specific tissue injury xenograft model, iMS cells contributed directly to muscle, bone, cartilage, and blood vessels, with no evidence of teratogenic potential. In a cardiotoxin muscle injury model, iMS cells contributed specifically to satellite cells and myofibers without ectopic tissue formation. Together, human adipocyte-derived iMS cells regenerate tissues in a context-dependent manner without ectopic or neoplastic growth.

Olfactomedin-like 3 promotes PDGF-dependent pericyte proliferation and migration during embryonic blood vessel formation

Pericytes promote vessel stability and their dysfunction causes pathologies due to blood vessel leakage. Previously, we reported that Olfactomedin-like 3 (Olfml3) is a matricellular protein with proangiogenic properties. Here, we explored the role of Olfml3 in a knockout mouse model engineered to suppress this protein. The mutant mice exhibited vascular defects in pericyte coverage, suggesting that pericytes influence blood vessel formation in an Olfml3-dependent manner. Olfml3-deficient mice exhibited abnormalities in the vasculature causing partial lethality of embryos and neonates. Reduced pericyte coverage was observed at embryonic day 12.5 and persisted throughout development, resulting in perinatal death of 35% of Olfml3-deficient mice. Cultured Olfml3-deficient pericytes exhibited aberrant motility and altered pericyte association to endothelial cells. Furthermore, the proliferative response of Olfml3^-/- pericytes upon PDGF-B stimulation was significantly diminished. Subsequent experiments revealed that intact PDGF-B signaling, mediated via Olfml3 binding, is required for pericyte proliferation and activation of downstream kinase pathways. Our findings suggest a model wherein pericyte recruitment to endothelial cells requires Olfml3 to provide early instructive cue and retain PDGF-B along newly formed vessels to achieve optimal angiogenesis.

Interplay between Cell-Surface Receptors and Extracellular Matrix in Skin

Skin consists of the epidermis and dermis, which are connected by a specialized basement membrane-the epidermal basement membrane. Both the epidermal basement membrane and the underlying interstitial extracellular matrix (ECM) created by dermal fibroblasts contain distinct network-forming macromolecules. These matrices play various roles in order to maintain skin homeostasis and integrity. Within this complex interplay of cells and matrices, cell surface receptors play essential roles not only for inside-out and outside-in signaling, but also for establishing mechanical and biochemical properties of skin. Already minor modulations of this multifactorial cross-talk can lead to severe and systemic diseases. In this review, major epidermal and dermal cell surface receptors will be addressed with respect to their interactions with matrix components as well as their roles in fibrotic, inflammatory or tumorigenic skin diseases.

TGFβ acts through PDGFRβ to activate mTORC1 via the Akt/PRAS40 axis and causes glomerular mesangial cell hypertrophy and matrix protein expression

Interaction of transforming growth factor-β (TGFβ)-induced canonical signaling with the noncanonical kinase cascades regulates glomerular hypertrophy and matrix protein deposition, which are early features of glomerulosclerosis. However, the specific target downstream of the TGFβ receptor involved in the noncanonical signaling is unknown. Here, we show that TGFβ increased the catalytic loop phosphorylation of platelet-derived growth factor receptor β (PDGFRβ), a receptor tyrosine kinase expressed abundantly in glomerular mesangial cells. TGFβ increased phosphorylation of the PI 3-kinase-interacting Tyr-751 residue of PDGFRβ, thus activating Akt. Inhibition of PDGFRβ using a pharmacological inhibitor and siRNAs blocked TGFβ-stimulated phosphorylation of proline-rich Akt substrate of 40 kDa (PRAS40), an intrinsic inhibitory component of mTORC1, and prevented activation of mTORC1 in the absence of any effect on Smad 2/3 phosphorylation. Expression of constitutively active myristoylated Akt reversed the siPDGFRβ-mediated inhibition of mTORC1 activity; however, co-expression of the phospho-deficient mutant of PRAS40 inhibited the effect of myristoylated Akt, suggesting a definitive role of PRAS40 phosphorylation in mTORC1 activation downstream of PDGFRβ in mesangial cells. Additionally, we demonstrate that PDGFRβ-initiated phosphorylation of PRAS40 is required for TGFβ-induced mesangial cell hypertrophy and fibronectin and collagen I (α2) production. Increased activating phosphorylation of PDGFRβ is also associated with enhanced TGFβ expression and mTORC1 activation in the kidney cortex and glomeruli of diabetic mice and rats, respectively. Thus, pursuing TGFβ noncanonical signaling, we identified how TGFβ receptor I achieves mTORC1 activation through PDGFRβ-mediated Akt/PRAS40 phosphorylation to spur mesangial cell hypertrophy and matrix protein accumulation. These findings provide support for targeting PDGFRβ in TGFβ-driven renal fibrosis.

Heat shock protein 90 inhibitor AUY922 attenuates platelet-derived growth factor-BB-induced migration and proliferation of vascular smooth muscle cells

Luminespib (AUY922), a heat shock proteins 90 inhibitor, has anti-neoplastic and antitumor effects. However, it is not clear whether AUY922 affects events in vascular diseases. We investigated the effects of AUY922 on the platelet-derived growth factor (PDGF)-BB-stimulated proliferation and migration of vascular smooth muscle cells (VSMC). VSMC viability was detected using the XTT (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) reagent. To detect the attenuating effects of AUY922 on PDGF-BB-induced VSMCs migration in vitro, we performed the Boyden chamber and scratch wound healing assays. To identify AUY922-mediated changes in the signaling pathway, the phosphorylation of protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) 1/2 was analyzed by immunoblotting. The inhibitory effects of AUY922 on migration and proliferation ex vivo were tested using an aortic ring assay. AUY922 was not cytotoxic at concentrations up to 5 nM. PDGF-BB-induced VSMC proliferation, migration, and sprout outgrowth were significantly decreased by AUY922 in a dose-dependent manner. AUY922 significantly reduced the PDGF-BB-stimulated phosphorylation of Akt and ERK1/2. Furthermore, PD98059 (a selective ERK1/2 inhibitor) and LY294002 (a selective Akt inhibitor) decreased VSMC migration and proliferation by inhibiting phosphorylation of Akt and ERK1/2. Greater attenuation of PDGF-BB-induced cell viability and migration was observed upon treatment with PD98059 or LY294002 in combination with AUY922. AUY922 showed anti-proliferation and anti-migration effects towards PDGF-BBinduced VSMCs by regulating the phosphorylation of ERK1/2 and Akt. Thus, AUY922 is a candidate for the treatment of atherosclerosis and restenosis.

Inhibitory Effects of PRG4 on Migration and Proliferation of Human Venous Cells

BACKGROUND

Proteoglycan 4 (PRG4; lubricin) is a member of two gene co-expression network modules associated with human vein graft failure. However, little is known about PRG4 and the vascular system. Therefore, we have investigated the effects of recombinant human PRG4 (rhPRG4) on cell migration and proliferation in human veins.

METHODS

Effects of rhPRG4 on cell migration, proliferation, and neointima formation were determined in human venous tissue and cultured venous smooth muscle cells (SMCs), adventitial cells, and endothelial cells. Expression of PRG4 by cultured human saphenous veins, failed vein grafts, and varicose veins was determined by immunostaining or Western blotting.

RESULTS

Limited expression of PRG4 in fresh saphenous veins was dramatically increased around medial SMCs after culture ex vivo. rhPRG4 inhibited the migration of cultured SMCs, adventitial cells, and endothelial cells, as well as the proliferation of endothelial cells. rhPRG4 also inhibited the migration of SMCs and adventitial cells from tissue explants, but there was no effect on cell proliferation or neointima formation in ex vivo whole veins. Finally, PRG4 was largely absent in two examples of venous pathology, that is, failed human vein grafts and varicose veins.

CONCLUSIONS

Although rhPRG4 can inhibit the migration of venous SMCs, endothelial cells, and adventitial cells, and the proliferation of endothelial cells, PRG4 was only increased around medial SMCs in veins after ex vivo culture. PRG4 was not observed around medial SMCs in failed human vein grafts and varicose veins, suggesting the possibility that a failure of PRG4 upregulation may promote these pathologies.

Cell-specific expression of the transcriptional regulator RHAMM provides a timing mechanism that controls appropriate wound re-epithelialization

Prevention of aberrant cutaneous wound repair and appropriate regeneration of an intact and functional integument require the coordinated timing of fibroblast and keratinocyte migration. Here, we identified a mechanism whereby opposing cell-specific motogenic functions of a multifunctional intracellular and extracellular protein, the receptor for hyaluronan-mediated motility (RHAMM), coordinates fibroblast and keratinocyte migration speed and ensures appropriate timing of excisional wound closure. We found that, unlike in WT mice, in Rhamm-null mice, keratinocyte migration initiates prematurely in the excisional wounds, resulting in wounds that have re-surfaced before the formation of normal granulation tissue, leading to a defective epidermal architecture. We also noted aberrant keratinocyte and fibroblast migration in the Rhamm-null mice, indicating that RHAMM suppresses keratinocyte motility but increases fibroblast motility. This cell context-dependent effect resulted from cell-specific regulation of extracellular signal-regulated kinase 1/2 (ERK1/2) activation and expression of a RHAMM target gene encoding matrix metalloprotease 9 (MMP-9). In fibroblasts, RHAMM promoted ERK1/2 activation and MMP-9 expression, whereas in keratinocytes, RHAMM suppressed these activities. In keratinocytes, loss of RHAMM function or expression promoted epidermal growth factor receptor-regulated MMP-9 expression via ERK1/2, which resulted in cleavage of the ectodomain of the RHAMM partner protein CD44 and thereby increased keratinocyte motility. These results identify RHAMM as a key factor that integrates the timing of wound repair by controlling cell migration.

Involvement of hyaluronan and CD44 in cancer and viral infections

Hyaluronan and its major receptor CD44 are ubiquitously distributed. They have important structural as well as signaling roles, regulating tissue homeostasis, and their expression levels are tightly regulated. In addition to signaling initiated by the interaction of the intracellular domain of CD44 with cytoplasmic signaling molecules, CD44 has important roles as a co-receptor for different types of receptors of growth factors and cytokines. Dysregulation of hyaluronan-CD44 interactions is seen in diseases, such as inflammation and cancer. In the present communication, we discuss the mechanism of hyaluronan-induced signaling via CD44, as well as the involvement of hyaluronan-engaged CD44 in malignancies and in viral infections.

Myocardial regeneration: role of epicardium and implicated genes

Lower invertebrates' hearts such as those of zebrafish have the capacity for scarless myocardial regeneration which is lost by mammalian hearts as they form a fibrotic scar tissue instead of regenerating the injured area. However, neonatal mammalian hearts have a remarkable capacity for regeneration highlighting conserved evolutionary mechanisms underlying such a process. Studies investigated the underlying mechanism of myocardial regeneration in species capable to do so, to see its applicability on mammals. The epicardium, the mesothelial outer layer of the vertebrate heart, has proven to play an important role in the process of repair and regeneration. It serves as an important source of smooth muscle cells, cardiac fibroblasts, endothelial cells, stem cells, and signaling molecules that are involved in this process. Here we review the role of the epicardium in myocardial regeneration focusing on the different involved; Activation, epithelial to mesenchymal transition, and differentiation. In addition, we will discuss its contributory role to different aspects that support myocardial regeneration. Of these we will discuss angiogenesis and the formation of a regenerate extracellular matrix. Moreover, we will discuss several factors that act on the epicardium to affect regeneration. Finally, we will highlight the utility of the epicardium as a mode of cell therapy in the treatment of myocardial injury.

Chitosan-hyaluronan: promotion of mucociliary differentiation of respiratory epithelial cells and development of olfactory receptor neurons

Developing a biomaterial that promotes regeneration of both respiratory epithelium (RE) and olfactory neuroepithelium (ON) improves the surgical outcome of endoscopic sinus surgery. Although chitosan (CS) inhibits mucociliary differentiation of RE, it has been reported to regenerate ON. In addition, hyaluronic acid (HA) has been demonstrated to promote regeneration of RE. Whether the composite CS + HA would simultaneously benefit RE and ON remains unexplored. Human nasal respiratory epithelial cells (RECs) and olfactory neuroepithelial cells (ONCs) are respectively obtained from the RE and the ON. They are cultured in vitro and divided into groups undergoing four treatments, control, CS, HA, and CS + HA and assessed by scanning electron microscope, immunocytochemistry, and Western blots following indicated growth conditions. RECs keep polygonal morphology with mucociliary differentiation in the CS + HA group. The levels of E-cadherin, zonula occludens-1, mucin 5AC, and forkhead box protein J1 are significantly higher in the CS + HA group than in the CS alone group. In addition, ONCs express lower cytokeratin 18 (CK18) and higher olfactory marker protein (OMP) in the CS + HA group than in HA alone group. ONCs express more signal transduction apparatuses, adenylate cyclase 3, in CS and CS + HA groups than in HA and controls. Chitosan-hyaluronan plays a part in promoting differentiation of ORNs and facilitating mucociliary differentiation of RECs. This composite is a promising biomaterial for the sinonasal application.

CD44 inhibits α-SMA gene expression via a novel G-actin/MRTF-mediated pathway that intersects with TGFβR/p38MAPK signaling in murine skin fibroblasts

Well-regulated differentiation of fibroblasts into myofibroblasts (MF) is critical for skin wound healing. Neoexpression of α-smooth muscle actin (α-SMA), an established marker for MF differentiation, is driven by TGFβ receptor (TGFβR)-mediated signaling. Hyaluronan (HA) and its receptor CD44 may also participate in this process. To further understand this process, primary mouse skin fibroblasts were isolated and treated in vitro with recombinant TGF-β1 (rTGF-β1) to induce α-SMA expression. CD44 expression was also increased. Paradoxically, CD44 knockdown by RNA interference (RNAi) led to increased α-SMA expression and α-SMA-containing stress fibers. Removal of extracellular HA or inhibition of HA synthesis had no effect on α-SMA levels, suggesting a dispensable role for HA. Exploration of mechanisms linking CD44 knockdown to α-SMA induction, using RNAi and chemical inhibitors, revealed a requirement for noncanonical TGFβR signaling through p38MAPK. Decreased monomeric G-actin but increased filamentous F-actin following CD44 RNAi suggested a possible role for myocardin-related transcription factor (MRTF), a known regulator of α-SMA transcription and itself regulated by G-actin binding. CD44 RNAi promoted nuclear accumulation of MRTF and the binding to its transcriptional cofactor SRF. MRTF knockdown abrogated the increased α-SMA expression caused by CD44 RNAi, suggesting that MRTF is required for CD44-mediated regulation of α-SMA. Finally, chemical inhibition of p38MAPK reversed nuclear MRTF accumulation after rTGF-β1 addition or CD44 RNAi, revealing a central involvement of p38MAPK in both cases. We concluded that CD44 regulates α-SMA gene expression through cooperation between two intersecting signaling pathways, one mediated by G-actin/MRTF and the other via TGFβR/p38MAPK.

Specificity, versatility, and control of TGF-β family signaling

Encoded in mammalian cells by 33 genes, the transforming growth factor-β (TGF-β) family of secreted, homodimeric and heterodimeric proteins controls the differentiation of most, if not all, cell lineages and many aspects of cell and tissue physiology in multicellular eukaryotes. Deregulation of TGF-β family signaling leads to developmental anomalies and disease, whereas enhanced TGF-β signaling contributes to cancer and fibrosis. Here, we review the fundamentals of the signaling mechanisms that are initiated upon TGF-β ligand binding to its cell surface receptors and the dependence of the signaling responses on input from and cooperation with other signaling pathways. We discuss how cells exquisitely control the functional presentation and activation of heteromeric receptor complexes of transmembrane, dual-specificity kinases and, thus, define their context-dependent responsiveness to ligands. We also introduce the mechanisms through which proteins called Smads act as intracellular effectors of ligand-induced gene expression responses and show that the specificity and impressive versatility of Smad signaling depend on cross-talk from other pathways. Last, we discuss how non-Smad signaling mechanisms, initiated by distinct ligand-activated receptor complexes, complement Smad signaling and thus contribute to cellular responses.

The Role of Stroma in Cholangiocarcinoma: The Intriguing Interplay between Fibroblastic Component, Immune Cell Subsets and Tumor Epithelium

Cholangiocarcinoma (CCA) is a severe and mostly intractable adenocarcinoma of biliary epithelial cells. A typical feature of CCA is its highly desmoplastic microenvironment containing fibrogenic connective tissue and an abundance of immune cells (T lymphocytes, Natural Killer (NK) cells, and macrophages) infiltrating tumor epithelium. This strong desmoplasia is orchestrated by various soluble factors and signals, suggesting a critical role in shaping a tumor growth-permissive microenvironment that is responsible for CCA poor clinical outcome. Indeed stroma not only provides an abundance of factors that facilitate CCA initiation, growth and progression, but also a prejudicial impact on therapeutic outcome. This review will give an overview of tumor-stroma signaling in a microenvironment critically regulating CCA development and progression. Identification of CCA secreted factors by both the fibroblast component and immune cell subsets might provide ample opportunities for pharmacological targeting of this type of cancer.

TGF-β receptors: In and beyond TGF-β signaling

Transforming growth factor β (TGF-β) plays an important role in normal development and homeostasis. Dysregulation of TGF-β responsiveness and its downstream signaling pathways contribute to many diseases, including cancer initiation, progression, and metastasis. TGF-β ligands bind to three isoforms of the TGF-β receptor (TGFBR) with different affinities. TGFBR1 and 2 are both serine/threonine and tyrosine kinases, but TGFBR3 does not have any kinase activity. They are necessary for activating canonical or noncanonical signaling pathways, as well as for regulating the activation of other signaling pathways. Another prominent feature of TGF-β signaling is its context-dependent effects, temporally and spatially. The diverse effects and context dependency are either achieved by fine-tuning the downstream components or by regulating the expressions and activities of the ligands or receptors. Focusing on the receptors in events in and beyond TGF-β signaling, we review the membrane trafficking of TGFBRs, the kinase activity of TGFBR1 and 2, the direct interactions between TGFBR2 and other receptors, and the novel roles of TGFBR3.

Hyaluronan antagonizes the differentiation effect of TGF-β1 on nasal epithelial cells through down-regulation of TGF-β type I receptor

Although hyaluronan (HA)-based biomaterials have been proposed to promote mucociliary differentiation of nasal epithelial cells (NECs), the mechanism by which HA affects the growth and differentiation of NECs has not been thoroughly explored. This study investigates the effect and mechanism of HA on the differentiation of NECs. The experiment cultures human NECs in four conditions, namely controls, transforming growth factor (TGF)-β1, TGF-β1 + HA and HA groups. In the TGF group, the NECs become irregular shape without formation of tight junction and mucociliary differentiation of NECs is inhibited. Epithelial-mesenchymal transition (EMT) of NECs also occurs in the TGF group. However, with addition of HA in TGF groups, NECs reveal the mucociliary phenotypes of epithelial cells with tight junction expression. Incubation of TGF-β1 in an NEC culture leads to an increase in phosphorylated type 1 TGF-β receptors (p-TβRI). This increase is attenuated when NECs are cultured in the presence of HA. Similar expressions are observed in phosphorylated smad2/smad3. Additionally, HA-dependent inhibition of TGF-β1 signalling is inhibited by co-incubation with a blocking antibody to CD44. Experimental results indicate that HA can antagonize TGF-β1 effect on EMT and mucociliary differentiation of NECs by down-regulation of TβR I, which is via CD44.

Substrate stiffness modulates the multipotency of human neural crest derived ectomesenchymal stem cells via CD44 mediated PDGFR signaling

Mesenchymal stem cells (MSCs) have been isolated from various mesodermal and ectodermal tissues. While the phenotypic and functional heterogeneity of MSCs stemming from their developmental origins has been acknowledged, the genetic and environmental factors underpinning these differences are not well-understood. Here, we investigated whether substrate stiffness mediated mechanical cues can directly modulate the development of ectodermal MSCs (eMSCs) from a precursor human neural crest stem cell (NCSC) population. We showed that NCSC-derived eMSCs were transcriptionally and functionally distinct from mesodermal bone marrow MSCs. eMSCs derived on lower substrate stiffness specifically increased their expression of the MSC marker, CD44 in a Rho-ROCK signaling dependent manner, which resulted in a concomitant increase in the eMSCs' adipogenic and chondrogenic differentiation potential. This mechanically-induced effect can only be maintained for short-term upon switching back to a stiff substrate but can be sustained for longer-term when the eMSCs were exclusively maintained on soft substrates. We also discovered that CD44 expression modulated eMSC self-renewal and multipotency via the downregulation of downstream platelet-derived growth factor receptor beta (PDGFRβ) signaling. This is the first instance demonstrating that substrate stiffness not only influences the differentiation trajectories of MSCs but also their derivation from upstream progenitors, such as NCSCs.

Antibody neutralization of cell-surface gC1qR/HABP1/SF2-p32 prevents lamellipodia formation and tumorigenesis

We previously demonstrated that cell-surface gC1qR is a key regulator of lamellipodia formation and cancer metastasis. Here, we screened a monoclonal mouse antibody against gC1qR to prevent cell migration by neutralizing cell-surface gC1qR. The anti-gC1qR antibody prevented growth factor-stimulated lamellipodia formation, cell migration and focal adhesion kinase activation by inactivating receptor tyrosine kinases (RTKs) in various cancer cells such as A549, MDA-MB-231, MCF7 and HeLa cells. The antibody neutralization of cell-surface gC1qR also inhibited angiogenesis because the anti-gC1qR antibody prevented growth factor-stimulated RTK activation, lamellipodia formation, cell migration and tube formation in HUVEC. In addition, we found that A549 tumorigenesis was reduced in a xenograft mouse model by following the administration of the anti-gC1qR antibody. With these data, we can conclude that the antibody neutralization of cell-surface gC1qR could be a good therapeutic strategy for cancer treatment.

CD44v6-competent tumor exosomes promote motility, invasion and cancer-initiating cell marker expression in pancreatic and colorectal cancer cells

Cancer-initiating cells (CIC) account for metastatic spread, which may rely mostly on CIC exosomes (TEX) that affect host cells and can transfer CIC features into Non-CIC. The CIC marker CD44 variant isoform v6 (CD44v6) being known for metastasis-promotion, we elaborated in cells its contribution to migration and invasion and in TEX the tranfer of migratory and invasive capacity to Non-CIC, using a CD44v6 knockdown (CD44v6kd) as Non-CIC model.A CD44v6kd in human pancreatic and colorectal cancer (PaCa, CoCa) lines led to loss of CIC characteristics including downregulation of additional CIC markers, particularly Tspan8. This aggravated the loss of CD44v6-promoted motility and invasion. Loss of motility relies on the distorted cooperation of CD44v6 and Tspan8 with associated integrins and loss of invasiveness on reduced protease expression. These deficits, transferred into TEX, severely altered the CD44v6kd-TEX composition. As a consequence, unlike the CIC-TEX, CD44v6kd TEX were not taken up by CD44v6kd cells and CIC. The uptake of CIC-TEX was accompanied by partial correction of CIC marker and protease expression in CD44v6kd cells, which regained migratory, invasive and metastatic competence. CIC-TEX also fostered angiogenesis and expansion of myeloid cells, likely due to a direct impact of CIC-TEX on the host, which could be supported by reprogrammed CD44v6kd cells.Taken together, the striking loss of tumor progression by a CD44v6kd relies on the capacity of CD44v6 to cooperate with associating integrins and proteases and its promotion of additional CIC marker expression. The defects by a CD44v6kd are efficiently corrected upon CIC-TEX uptake.

Growth factor delivery strategies for rotator cuff repair and regeneration

The high incidence of degenerative tears and prevalence of retears (20-95%) after surgical repair makes rotator cuff injuries a significant health problem. This high retear rate is attributed to the failure of the repaired tissue to regenerate the native tendon-to-bone insertion (enthesis). Biological augmentation of surgical repair such as autografts, allografts, and xenografts are confounded by donor site morbidity, immunogenicity, and disease transmission, respectively. In contrast, these risks may be alleviated via growth factor therapy, which can actively influence the healing environment to promote functional repair. Several challenges have to be overcome before growth factor delivery can translate into clinical practice such as the selection of optimal growth factor(s) or combination, identification of the most efficient stage and duration of delivery, and the design considerations for the delivery device. Emerging insight into the injury-repair microenvironment and our understanding of growth factor mechanisms in healing are informing the design of advanced delivery scaffolds to effectively treat rotator cuff tears. Here, we review potential growth factor candidates, design parameters and material selection for growth factor delivery, innovative and dynamic delivery scaffolds, and novel therapeutic targets from tendon and developmental biology for the structural and functional healing of rotator cuff repair.

CD44/CD44v6 a Reliable Companion in Cancer-Initiating Cell Maintenance and Tumor Progression

Metastasis is the leading cause of cancer death, tumor progression proceeding through emigration from the primary tumor, gaining access to the circulation, leaving the circulation, settling in distant organs and growing in the foreign environment. The capacity of a tumor to metastasize relies on a small subpopulation of cells in the primary tumor, so called cancer-initiating cells (CIC). CIC are characterized by sets of markers, mostly membrane anchored adhesion molecules, CD44v6 being the most frequently recovered marker. Knockdown and knockout models accompanied by loss of tumor progression despite unaltered primary tumor growth unraveled that these markers are indispensable for CIC. The unexpected contribution of marker molecules to CIC-related activities prompted research on underlying molecular mechanisms. This review outlines the contribution of CD44, particularly CD44v6 to CIC activities. A first focus is given to the impact of CD44/CD44v6 to inherent CIC features, including the crosstalk with the niche, apoptosis-resistance, and epithelial mesenchymal transition. Following the steps of the metastatic cascade, we report on supporting activities of CD44/CD44v6 in migration and invasion. These CD44/CD44v6 activities rely on the association with membrane-integrated and cytosolic signaling molecules and proteases and transcriptional regulation. They are not restricted to, but most pronounced in CIC and are tightly regulated by feedback loops. Finally, we discuss on the engagement of CD44/CD44v6 in exosome biogenesis, loading and delivery. exosomes being the main acteurs in the long-distance crosstalk of CIC with the host. In brief, by supporting the communication with the niche and promoting apoptosis resistance CD44/CD44v6 plays an important role in CIC maintenance. The multifaceted interplay between CD44/CD44v6, signal transducing molecules and proteases facilitates the metastasizing tumor cell journey through the body. By its engagement in exosome biogenesis CD44/CD44v6 contributes to disseminated tumor cell settlement and growth in distant organs. Thus, CD44/CD44v6 likely is the most central CIC biomarker.

CD146 coordinates brain endothelial cell-pericyte communication for blood-brain barrier development

The blood-brain barrier (BBB) establishes a protective interface between the central neuronal system and peripheral blood circulation and is crucial for homeostasis of the CNS. BBB formation starts when the endothelial cells (ECs) invade the CNS and pericytes are recruited to the nascent vessels during embryogenesis. Despite the essential function of pericyte-EC interaction during BBB development, the molecular mechanisms coordinating the pericyte-EC behavior and communication remain incompletely understood. Here, we report a single cell receptor, CD146, that presents dynamic expression patterns in the cerebrovasculature at the stages of BBB induction and maturation, coordinates the interplay of ECs and pericytes, and orchestrates BBB development spatiotemporally. In mouse brain, CD146 is first expressed in the cerebrovascular ECs of immature capillaries without pericyte coverage; with increased coverage of pericytes, CD146 could only be detected in pericytes, but not in cerebrovascular ECs. Specific deletion of Cd146 in mice ECs resulted in reduced brain endothelial claudin-5 expression and BBB breakdown. By analyzing mice with specific deletion of Cd146 in pericytes, which have defects in pericyte coverage and BBB integrity, we demonstrate that CD146 functions as a coreceptor of PDGF receptor-β to mediate pericyte recruitment to cerebrovascular ECs. Moreover, we found that the attached pericytes in turn down-regulate endothelial CD146 by secreting TGF-β1 to promote further BBB maturation. These results reveal that the dynamic expression of CD146 controls the behavior of ECs and pericytes, thereby coordinating the formation of a mature and stable BBB.

TGF-β promotes PI3K-AKT signaling and prostate cancer cell migration through the TRAF6-mediated ubiquitylation of p85α

Transforming growth factor-β (TGF-β) is a pluripotent cytokine that regulates cell fate and plasticity in normal tissues and tumors. The multifunctional cellular responses evoked by TGF-β are mediated by the canonical SMAD pathway and by noncanonical pathways, including mitogen-activated protein kinase (MAPK) pathways and the phosphatidylinositol 3'-kinase (PI3K)-protein kinase B (AKT) pathway. We found that TGF-β activated PI3K in a manner dependent on the activity of the E3 ubiquitin ligase tumor necrosis factor receptor-associated factor 6 (TRAF6). TRAF6 polyubiquitylated the PI3K regulatory subunit p85α and promoted the formation of a complex between the TGF-β type I receptor (TβRI) and p85α, which led to the activation of PI3K and AKT. Lys⁶³-linked polyubiquitylation of p85α on Lys⁵¹³ and Lys⁵¹⁹ in the iSH2 (inter-Src homology 2) domain was required for TGF-β-induced activation of PI3K-AKT signaling and cell motility in prostate cancer cells and activated macrophages. Unlike the activation of SMAD pathways, the TRAF6-mediated activation of PI3K and AKT was not dependent on the kinase activity of TβRI. In situ proximity ligation assays revealed that polyubiquitylation of p85α was evident in aggressive prostate cancer tissues. Thus, our data reveal a molecular mechanism by which TGF-β activates the PI3K-AKT pathway to drive cell migration.

Platelet-Rich Fibrin Lysate Can Ameliorate Dysfunction of Chronically UVA-Irradiated Human Dermal Fibroblasts

To determine whether platelet-rich fibrin lysate (PRF-L) could restore the function of chronically ultraviolet-A (UVA)-irradiated human dermal fibroblasts (HDFs), we isolated and sub-cultured HDFs from six different human foreskins. HDFs were divided into two groups: those that received chronic UVA irradiation (total dosages of 10 J cm⁻²) and those that were not irradiated. We compared the proliferation rates, collagen deposition, and migration rates between the groups and between chronically UVA-irradiated HDFs in control and PRF-L-treated media. Our experiment showed that chronic UVA irradiation significantly decreased (p<0.05) the proliferation rates, migration rates, and collagen deposition of HDFs, compared to controls. Compared to control media, chronically UVA-irradiated HDFs in 50% PRF-L had significantly increased proliferation rates, migration rates, and collagen deposition (p<0.05), and the migration rates and collagen deposition of chronically UVA-irradiated HDFs in 50% PRF-L were equal to those of normal fibroblasts. Based on this experiment, we concluded that PRF-L is a good candidate material for treating UVA-induced photoaging of skin, although the best method for its clinical application remains to be determined.

Signaling Receptors for TGF-β Family Members

Transforming growth factor β (TGF-β) family members signal via heterotetrameric complexes of type I and type II dual specificity kinase receptors. The activation and stability of the receptors are controlled by posttranslational modifications, such as phosphorylation, ubiquitylation, sumoylation, and neddylation, as well as by interaction with other proteins at the cell surface and in the cytoplasm. Activation of TGF-β receptors induces signaling via formation of Smad complexes that are translocated to the nucleus where they act as transcription factors, as well as via non-Smad pathways, including the Erk1/2, JNK and p38 MAP kinase pathways, and the Src tyrosine kinase, phosphatidylinositol 3'-kinase, and Rho GTPases.

Pancreatic cancer stem cell markers and exosomes - the incentive push

Pancreatic cancer (PaCa) has the highest death rate and incidence is increasing. Poor prognosis is due to late diagnosis and early metastatic spread, which is ascribed to a minor population of so called cancer stem cells (CSC) within the mass of the primary tumor. CSC are defined by biological features, which they share with adult stem cells like longevity, rare cell division, the capacity for self renewal, differentiation, drug resistance and the requirement for a niche. CSC can also be identified by sets of markers, which for pancreatic CSC (Pa-CSC) include CD44v6, c-Met, Tspan8, alpha6beta4, CXCR4, CD133, EpCAM and claudin7. The functional relevance of CSC markers is still disputed. We hypothesize that Pa-CSC markers play a decisive role in tumor progression. This is fostered by the location in glycolipid-enriched membrane domains, which function as signaling platform and support connectivity of the individual Pa-CSC markers. Outside-in signaling supports apoptosis resistance, stem cell gene expression and tumor suppressor gene repression as well as miRNA transcription and silencing. Pa-CSC markers also contribute to motility and invasiveness. By ligand binding host cells are triggered towards creating a milieu supporting Pa-CSC maintenance. Furthermore, CSC markers contribute to the generation, loading and delivery of exosomes, whereby CSC gain the capacity for a cell-cell contact independent crosstalk with the host and neighboring non-CSC. This allows Pa-CSC exosomes (TEX) to reprogram neighboring non-CSC towards epithelial mesenchymal transition and to stimulate host cells towards preparing a niche for metastasizing tumor cells. Finally, TEX communicate with the matrix to support tumor cell motility, invasion and homing. We will discuss the possibility that CSC markers are the initial trigger for these processes and what is the special contribution of CSC-TEX.

Platelet-derived growth factor (PDGF)-induced activation of Erk5 MAP-kinase is dependent on Mekk2, Mek1/2, PKC and PI3-kinase, and affects BMP signaling

Platelet-derived growth factor-BB (PDGF-BB) binds to its tyrosine kinase receptors (PDGFRs) and stimulates mitogenicity and survival of cells of mesenchymal origin. Activation of PDGFRs initiates a number of downstream signaling pathways, including phosphatidyl 3'-inositol kinase (PI3-kinase), phospholipase Cγ and MAP kinase pathways. In this report, we show that Erk5 MAP kinase is activated in response to PDGF-BB in the smooth muscle cell line MOVAS in a manner dependent on Mekk2, Mek1/2, Mek5, PI3-kinase and protein kinase C (PKC). The co-operation of Mek1/2 and Mekk2 in the activation of Erk5, suggests a close co-regulation between the Erk1/2 and Erk5 MAP kinase pathways. Furthermore, we found that classical PKCs are important for Erk5 activation. In addition, we found that PKCζ interacts with Erk5 and may exert a negative feed-back effect. We observed no nuclear accumulation of Erk5 in response to PDGF-BB stimulation, however, we identified a mechanism by which cytoplasmic Erk5 influences gene expression; Erk5 was essential for PDGF-BB-mediated Smad1/5/8 signaling by stimulating release and/or activation of bone morphogenetic protein(s) (BMPs). Thus, PDGF-BB-induced Erk5 activation involves parallel stimulatory and inhibitory pathways and promotes Smad1/5/8 signaling.

Surface proteome analysis identifies platelet derived growth factor receptor-alpha as a critical mediator of transforming growth factor-beta-induced collagen secretion

Fibroblasts are extracellular matrix-producing cells in the lung. Fibroblast activation by transforming growth factor-beta leads to myofibroblast-differentiation and increased extracellular matrix deposition, a hallmark of pulmonary fibrosis. While fibroblast function with respect to migration, invasion, and extracellular matrix deposition has been well-explored, little is known about the surface proteome of lung fibroblasts in general and its specific response to fibrogenic growth factors, in particular transforming growth factor-beta. We thus performed a cell-surface proteome analysis of primary human lung fibroblasts in presence/absence of transforming growth factor-beta, followed by characterization of our findings using FACS analysis, Western blot, and siRNA-mediated knockdown experiments. We identified 213 surface proteins significantly regulated by transforming growth factor-beta, platelet derived growth factor receptor-alpha being one of the top down-regulated proteins. Transforming growth factor beta-induced downregulation of platelet derived growth factor receptor-alpha induced upregulation of platelet derived growth factor receptor-beta expression and phosphorylation of Akt, a downstream target of platelet derived growth factor signaling. Importantly, collagen type V expression and secretion was strongly increased after forced knockdown of platelet derived growth factor receptor-alpha, an effect that was potentiated by transforming growth factor-beta. We therefore show previously underappreciated cross-talk of transforming growth factor-beta and platelet derived growth factor signaling in human lung fibroblasts, resulting in increased extracellular matrix deposition in a platelet derived growth factor receptor-alpha dependent manner. These findings are of particular importance for the treatment of lung fibrosis patients with high pulmonary transforming growth factor-beta activity.

Multiple routes of endocytic internalization of PDGFRβ contribute to PDGF-induced STAT3 signaling

Platelet-derived growth factor receptor β (PDGFRβ) is a receptor tyrosine kinase which upon activation by PDGF-BB stimulates cell proliferation, migration and angiogenesis. Ligand binding induces intracellular signaling cascades but also internalization of the receptor, eventually resulting in its lysosomal degradation. However, endocytic trafficking of receptors often modulates their downstream signaling. We previously reported that internalization of PDGFRβ occurs via dynamin-dependent and -independent pathways but their further molecular determinants remained unknown. Here we show that in human fibroblasts expressing endogenous PDGFRβ and stimulated with 50 ng/ml PDGF-BB, ligand-receptor uptake proceeds via parallel routes of clathrin-mediated endocytosis (CME) and clathrin-independent endocytosis (CIE). CME involves the canonical AP2 complex as a clathrin adaptor, while CIE requires RhoA-ROCK, Cdc42 and galectin-3, the latter indicating lectin-mediated internalization via clathrin-independent carriers (CLICs). Although different uptake routes appear to be partly interdependent, they cannot fully substitute for each other. Strikingly, inhibition of any internalization mechanism impaired activation of STAT3 but not of other downstream effectors of PDGFRβ. Our data indicate that multiple routes of internalization of PDGFRβ contribute to a transcriptional and mitogenic response of cells to PDGF.

Extracellular component hyaluronic acid and its receptor Hmmr are required for epicardial EMT during heart regeneration

AIMS

After injury, the adult zebrafish can regenerate the heart. This requires the activation of the endocardium and epicardium as well as the proliferation of pre-existing cardiomyocytes to replace the lost tissue. However, the molecular mechanisms involved in this process are not completely resolved. In this work, we aim to identify the proteins involved in zebrafish heart regeneration and to explore their function.

METHODS AND RESULTS

Using a proteomic approach, we identified Hyaluronan-mediated motility receptor (Hmmr), a hyaluronic acid (HA) receptor, to be expressed following ventricular resection in zebrafish. Moreover, enzymes that produce HA, hyaluronic acid synthases (has), were also expressed following injury, suggesting that this pathway may serve important functions in the regenerating heart. Indeed, suppression of HA production, as well as depletion of Hmmr, blocked cardiac regeneration. Mechanistically, HA and Hmmr are required for epicardial cell epithelial-mesenchymal transition (EMT) and their subsequent migration into the regenerating ventricle. Furthermore, chemical inhibition of Focal Adhesion Kinase (FAK) or inhibition of Src kinases, downstream effectors of Hmmr, also prevented epicardial cell migration, implicating a HA/Hmmr/FAK/Src pathway in this process. In a rat model of myocardial infarction, both HA and HMMR were up-regulated and localized in the infarct area within the first few days following damage, suggesting that this pathway may also play an important role in cardiac repair in mammals.

CONCLUSION

HA and Hmmr are required for activated epicardial cell EMT and migration involving the FAK/Src pathway for proper heart regeneration.

CD44, Hyaluronan, the Hematopoietic Stem Cell, and Leukemia-Initiating Cells

CD44 is an adhesion molecule that varies in size due to glycosylation and insertion of so-called variant exon products. The CD44 standard isoform (CD44s) is highly expressed in many cells and most abundantly in cells of the hematopoietic system, whereas expression of CD44 variant isoforms (CD44v) is more restricted. CD44s and CD44v are known as stem cell markers, first described for hematopoietic stem cells and later on confirmed for cancer- and leukemia-initiating cells. Importantly, both abundantly expressed CD44s as well as CD44v actively contribute to the maintenance of stem cell features, like generating and embedding in a niche, homing into the niche, maintenance of quiescence, and relative apoptosis resistance. This is surprising, as CD44 is not a master stem cell gene. I here will discuss that the functional contribution of CD44 relies on its particular communication skills with neighboring molecules, adjacent cells and, last not least, the surrounding matrix. In fact, it is the interaction of the hyaluronan receptor CD44 with its prime ligand, which strongly assists stem cells to fulfill their special and demanding tasks. Recent fundamental progress in support of this “old” hypothesis, which may soon pave the way for most promising new therapeutics, is presented for both hematopoietic stem cell and leukemia-initiating cell. The contribution of CD44 to the generation of a stem cell niche, to homing of stem cells in their niche, to stem cell quiescence and apoptosis resistance will be in focus.