Agrin is required for survival and function of monocytic cells. Blood. 2012;119:5502-5511. [PMID: 22517892 DOI: 10.1182/blood-2011-09-382812]

Heparan sulfates and heparan sulfate proteoglycans in hematopoiesis

ABSTRACT

From signaling mediators in stem cells to markers of differentiation and lineage commitment to facilitators for the entry of viruses, such as HIV-1, cell surface heparan sulfate (HS) glycans with distinct modification patterns play important roles in hematopoietic biology. In this review, we provide an overview of the importance of HS and the proteoglycans (HSPGs) to which they are attached within the major cellular subtypes of the hematopoietic system. We summarize the roles of HSPGs, HS, and HS modifications within each main hematopoietic cell lineage of both myeloid and lymphoid arms. Lastly, we discuss the biological advances in the detection of HS modifications and their potential to further discriminate cell types within hematopoietic tissue.

Agrin is a novel oncogenic protein in thyroid cancer

Agrin (AGRN) is a matricellular glycoprotein involved in extracellular signal transduction. AGRN is involved in tumorigenesis and cancer progression; however, the role of AGRN in thyroid cancer (TC) remains unclear. In the present study, using cell lines derived from various subtypes of TC including CGTH, FTC-133 and BcPAP and transcriptomic data from patients with TC, the role of AGRN in TC was analyzed by migration, invasion, viability and proliferation assays as well as Western blot with EMT markers. AGRN expression was significantly increased in thyroid tumors and cell lines derived from various TC subtypes. The highest AGRN expression was found in follicular and papillary thyroid carcinoma subtypes. Immunocytochemistry revealed nuclear AGRN localization in normal (NTHY) and TC cells. Silencing of AGRN decreased viability, proliferation, migration and invasion of TC cell lines by upregulating vimentin and downregulating N-cadherin and E-cadherin. Furthermore, the expression of AGRN was associated with neutrophil infiltration in thyroid tumors. In conclusion, the present results indicated that increased AGRN expression promoted tumorigenic phenotypes of TC cells, while AGRN expression was associated with immune infiltration in thyroid tumors. AGRN may represent a target for future cancer therapy and requires further evaluation.

Transcriptional changes of the aging lung

Aging is a natural process associated with declined organ function and higher susceptibility to developing chronic diseases. A systemic single-cell type-based study provides a unique opportunity to understand the mechanisms behind age-related pathologies. Here, we use single-cell gene expression analysis comparing healthy young and aged human lungs from nonsmoker donors to investigate age-related transcriptional changes. Our data suggest that aging has a heterogenous effect on lung cells, as some populations are more transcriptionally dynamic while others remain stable in aged individuals. We found that monocytes and alveolar macrophages were the most transcriptionally affected populations. These changes were related to inflammation and regulation of the immune response. Additionally, we calculated the LungAge score, which reveals the diversity of lung cell types during aging. Changes in DNA damage repair, fatty acid metabolism, and inflammation are essential for age prediction. Finally, we quantified the senescence score in aged lungs and found that the more biased cells toward senescence are immune and progenitor cells. Our study provides a comprehensive and systemic analysis of the molecular signatures of lung aging. Our LungAge signature can be used to predict molecular signatures of physiological aging and to detect common signatures of age-related lung diseases.

Bioinformatics-based analysis of the roles of basement membrane-related gene AGRN in systemic lupus erythematosus and pan-cancer development

Introduction

Systemic lupus erythematosus (SLE) is an autoimmune disease involving many systems and organs, and individuals with SLE exhibit unique cancer risk characteristics. The significance of the basement membrane (BM) in the occurrence and progression of human autoimmune diseases and tumors has been established through research. However, the roles of BM-related genes and their protein expression mechanisms in the pathogenesis of SLE and pan-cancer development has not been elucidated.

Methods

In this study, we applied bioinformatics methods to perform differential expression analysis of BM-related genes in datasets from SLE patients. We utilized LASSO logistic regression, SVM-RFE, and RandomForest to screen for feature genes and construct a diagnosis model for SLE. In order to attain a comprehensive comprehension of the biological functionalities of the feature genes, we conducted GSEA analysis, ROC analysis, and computed levels of immune cell infiltration. Finally, we sourced pan-cancer expression profiles from the TCGA and GTEx databases and performed pan-cancer analysis.

Results

We screened six feature genes (AGRN, PHF13, SPOCK2, TGFBI, COL4A3, and COLQ) to construct an SLE diagnostic model. Immune infiltration analysis showed a significant correlation between AGRN and immune cell functions such as parainflammation and type I IFN response. After further gene expression validation, we finally selected AGRN for pan-cancer analysis. The results showed that AGRN's expression level varied according to distinct tumor types and was closely correlated with some tumor patients' prognosis, immune cell infiltration, and other indicators.

Discussion

In conclusion, BM-related genes play a pivotal role in the pathogenesis of SLE, and AGRN shows immense promise as a target in SLE and the progression of multiple tumors.

The neuroimmune axis of Alzheimer's disease

Alzheimer's disease (AD) is a genetically complex and heterogeneous disorder with multifaceted neuropathological features, including β-amyloid plaques, neurofibrillary tangles, and neuroinflammation. Over the past decade, emerging evidence has implicated both beneficial and pathological roles for innate immune genes and immune cells, including peripheral immune cells such as T cells, which can infiltrate the brain and either ameliorate or exacerbate AD neuropathogenesis. These findings support a neuroimmune axis of AD, in which the interplay of adaptive and innate immune systems inside and outside the brain critically impacts the etiology and pathogenesis of AD. In this review, we discuss the complexities of AD neuropathology at the levels of genetics and cellular physiology, highlighting immune signaling pathways and genes associated with AD risk and interactions among both innate and adaptive immune cells in the AD brain. We emphasize the role of peripheral immune cells in AD and the mechanisms by which immune cells, such as T cells and monocytes, influence AD neuropathology, including microglial clearance of amyloid-β peptide, the key component of β-amyloid plaque cores, pro-inflammatory and cytotoxic activity of microglia, astrogliosis, and their interactions with the brain vasculature. Finally, we review the challenges and outlook for establishing immune-based therapies for treating and preventing AD.

Regulation of stem cell fate by HSPGs: implication in hair follicle cycling

Heparan sulfate proteoglycans (HSPGs) are part of proteoglycan family. They are composed of heparan sulfate (HS)-type glycosaminoglycan (GAG) chains covalently linked to a core protein. By interacting with growth factors and/or receptors, they regulate numerous pathways including Wnt, hedgehog (Hh), bone morphogenic protein (BMP) and fibroblast growth factor (FGF) pathways. They act as inhibitor or activator of these pathways to modulate embryonic and adult stem cell fate during organ morphogenesis, regeneration and homeostasis. This review summarizes the knowledge on HSPG structure and classification and explores several signaling pathways regulated by HSPGs in stem cell fate. A specific focus on hair follicle stem cell fate and the possibility to target HSPGs in order to tackle hair loss are discussed in more dermatological and cosmeceutical perspectives.

Deconstruction of Neurotrypsin Reveals a Multi-factorially Regulated Activity Affecting Myotube Formation and Neuronal Excitability

Neurotrypsin (NT) is a highly specific nervous system multi-domain serine protease best known for its selective processing of the potent synaptic organizer agrin. Its enzymatic activity is thought to influence processes of synaptic plasticity, with its deregulation causing accelerated neuromuscular junction (NMJ) degeneration or contributing to forms of mental retardation. These biological effects are likely to stem from NT-based regulation of agrin signaling. However, dissecting the exact biological implications of NT-agrin interplay is difficult, due to the scarce molecular detail regarding NT activity and NT-agrin interactions. We developed a strategy to reliably produce and purify a catalytically competent engineered variant of NT called "NT-mini" and a library of C-terminal agrin fragments, with which we performed a thorough biochemical and biophysical characterization of NT enzyme functionality. We studied the regulatory effects of calcium ions and heparin, identified NT's heparin-binding domain, and discovered how zinc ions induce modulation of enzymatic activity. Additionally, we investigated myotube differentiation and hippocampal neuron excitability, evidencing a dose-dependent increase in neuronal activity alongside a negative impact on myoblast fusion when using the active NT enzyme. Collectively, our results provide in vitro and cellular foundations to unravel the molecular underpinnings and biological significance of NT-agrin interactions.

Neuronal Agrin Promotes Proliferation of Primary Human Myoblasts in an Age-Dependent Manner

Neuronal agrin, a heparan sulphate proteoglycan secreted by the α-motor neurons, promotes the formation and maintenance of the neuromuscular junction by binding to Lrp4 and activating muscle-specific kinase (MuSK). Neuronal agrin also promotes myogenesis by enhancing differentiation and maturation of myotubes, but its effect on proliferating human myoblasts, which are often considered to be unresponsive to agrin, remains unclear. Using primary human myoblasts, we determined that neuronal agrin induced transient dephosphorylation of ERK1/2, while c-Abl, STAT3, and focal adhesion kinase were unresponsive. Gene silencing of Lrp4 and MuSK markedly reduced the BrdU incorporation, suggesting the functional importance of the Lrp4/MuSK complex for myoblast proliferation. Acute and chronic treatments with neuronal agrin increased the proliferation of human myoblasts in old donors, but they did not affect the proliferation of myoblasts in young donors. The C-terminal fragment of agrin which lacks the Lrp4-binding site and cannot activate MuSK had a similar age-dependent effect, indicating that the age-dependent signalling pathways activated by neuronal agrin involve the Lrp4/MuSK receptor complex as well as an Lrp4/MuSK-independent pathway which remained unknown. Collectively, our results highlight an age-dependent role for neuronal agrin in promoting the proliferation of human myoblasts.

The extracellular matrix of hematopoietic stem cell niches

•

Comprehensive overview of different classes of ECM molecules in the HSC niche.

•

Overview of current knowledge on role of biophysics of the HSC niche.

•

Description of approaches to create artificial stem cell niches for several application.

•

Importance of considering ECM in drug development and testing.

Hematopoietic stem cells (HSCs) are the life-long source of all types of blood cells. Their function is controlled by their direct microenvironment, the HSC niche in the bone marrow. Although the importance of the extracellular matrix (ECM) in the niche by orchestrating niche architecture and cellular function is widely acknowledged, it is still underexplored. In this review, we provide a comprehensive overview of the ECM in HSC niches. For this purpose, we first briefly outline HSC niche biology and then review the role of the different classes of ECM molecules in the niche one by one and how they are perceived by cells. Matrix remodeling and the emerging importance of biophysics in HSC niche function are discussed. Finally, the application of the current knowledge of ECM in the niche in form of artificial HSC niches for HSC expansion or targeted differentiation as well as drug testing is reviewed.

Mechanobiological Principles Influence the Immune Response in Regeneration: Implications for Bone Healing

A misdirected or imbalanced local immune composition is often one of the reasons for unsuccessful regeneration resulting in scarring or fibrosis. Successful healing requires a balanced initiation and a timely down-regulation of the inflammation for the re-establishment of a biologically and mechanically homeostasis. While biomaterial-based approaches to control local immune responses are emerging as potential new treatment options, the extent to which biophysical material properties themselves play a role in modulating a local immune niche response has so far been considered only occasionally. The communication loop between extracellular matrix, non-hematopoietic cells, and immune cells seems to be specifically sensitive to mechanical cues and appears to play a role in the initiation and promotion of a local inflammatory setting. In this review, we focus on the crosstalk between ECM and its mechanical triggers and how they impact immune cells and non-hematopoietic cells and their crosstalk during tissue regeneration. We realized that especially mechanosensitive receptors such as TRPV4 and PIEZO1 and the mechanosensitive transcription factor YAP/TAZ are essential to regeneration in various organ settings. This indicates novel opportunities for therapeutic approaches to improve tissue regeneration, based on the immune-mechanical principles found in bone but also lung, heart, and skin.

Immunomodulatory Role of the Extracellular Matrix Within the Liver Disease Microenvironment

Chronic liver disease when accompanied by underlying fibrosis, is characterized by an accumulation of extracellular matrix (ECM) proteins and chronic inflammation. Although traditionally considered as a passive and largely architectural structure, the ECM is now being recognized as a source of potent damage-associated molecular pattern (DAMP)s with immune-active peptides and domains. In parallel, the ECM anchors a range of cytokines, chemokines and growth factors, all of which are capable of modulating immune responses. A growing body of evidence shows that ECM proteins themselves are capable of modulating immunity either directly via ligation with immune cell receptors including integrins and TLRs, or indirectly through release of immunoactive molecules such as cytokines which are stored within the ECM structure. Notably, ECM deposition and remodeling during injury and fibrosis can result in release or formation of ECM-DAMPs within the tissue, which can promote local inflammatory immune response and chemotactic immune cell recruitment and inflammation. It is well described that the ECM and immune response are interlinked and mutually participate in driving fibrosis, although their precise interactions in the context of chronic liver disease are poorly understood. This review aims to describe the known pro-/anti-inflammatory and fibrogenic properties of ECM proteins and DAMPs, with particular reference to the immunomodulatory properties of the ECM in the context of chronic liver disease. Finally, we discuss the importance of developing novel biotechnological platforms based on decellularized ECM-scaffolds, which provide opportunities to directly explore liver ECM-immune cell interactions in greater detail.

Transcriptome sequencing supports a conservation of macrophage polarization in fish

Mammalian macrophages can adopt polarization states that, depending on the exact stimuli present in their extracellular environment, can lead to very different functions. Although these different polarization states have been shown primarily for macrophages of humans and mice, it is likely that polarized macrophages with corresponding phenotypes exist across mammals. Evidence of functional conservation in macrophages from teleost fish suggests that the same, or at least comparable polarization states should also be present in teleosts. However, corresponding transcriptional profiles of marker genes have not been reported thus far. In this study we confirm that macrophages from common carp can polarize into M1- and M2 phenotypes with conserved functions and corresponding transcriptional profiles compared to mammalian macrophages. Carp M1 macrophages show increased production of nitric oxide and a transcriptional profile with increased pro-inflammatory cytokines and mediators, including il6, il12 and saa. Carp M2 macrophages show increased arginase activity and a transcriptional profile with increased anti-inflammatory mediators, including cyr61, timp2b and tgm2b. Our RNA sequencing approach allowed us to list, in an unbiased manner, markers discriminating between M1 and M2 macrophages of teleost fish. We discuss the importance of our findings for the evaluation of immunostimulants for aquaculture and for the identification of gene targets to generate transgenic zebrafish for detailed studies on M1 and M2 macrophages. Above all, we discuss the striking degree of evolutionary conservation of macrophage polarization in a lower vertebrate.

Agrin Promotes Coordinated Therapeutic Processes Leading to Improved Cardiac Repair in Pigs

BACKGROUND

Ischemic heart diseases are leading causes of death and reduced life quality worldwide. Although revascularization strategies significantly reduce mortality after acute myocardial infarction (MI), a large number of patients with MI develop chronic heart failure over time. We previously reported that a fragment of the extracellular matrix protein agrin promotes cardiac regeneration after MI in adult mice.

METHODS

To test the therapeutic potential of agrin in a preclinical porcine model, we performed ischemia-reperfusion injuries using balloon occlusion for 60 minutes followed by a 3-, 7-, or 28-day reperfusion period.

RESULTS

We demonstrated that local (antegrade) delivery of recombinant human agrin to the infarcted pig heart can target the affected regions in an efficient and clinically relevant manner. A single dose of recombinant human agrin improved heart function, infarct size, fibrosis, and adverse remodeling parameters 28 days after MI. Short-term MI experiments along with complementary murine studies revealed myocardial protection, improved angiogenesis, inflammatory suppression, and cell cycle reentry as agrin's mechanisms of action.

CONCLUSIONS

A single dose of agrin is capable of reducing ischemia-reperfusion injury and improving heart function, demonstrating that agrin could serve as a therapy for patients with acute MI and potentially heart failure.

Dissecting the Extracellular Complexity of Neuromuscular Junction Organizers

Synapse formation is a very elaborate process dependent upon accurate coordination of pre and post-synaptic specialization, requiring multiple steps and a variety of receptors and signaling molecules. Due to its relative structural simplicity and the ease in manipulation and observation, the neuromuscular synapse or neuromuscular junction (NMJ)-the connection between motor neurons and skeletal muscle-represents the archetype junction system for studying synapse formation and conservation. This junction is essential for survival, as it controls our ability to move and breath. NMJ formation requires coordinated interactions between motor neurons and muscle fibers, which ultimately result in the formation of a highly specialized post-synaptic architecture and a highly differentiated nerve terminal. Furthermore, to ensure a fast and reliable synaptic transmission following neurotransmitter release, ligand-gated channels (acetylcholine receptors, AChRs) are clustered on the post-synaptic muscle cell at high concentrations in sites opposite the presynaptic active zone, supporting a direct role for nerves in the organization of the post-synaptic membrane architecture. This organized clustering process, essential for NMJ formation and for life, relies on key signaling molecules and receptors and is regulated by soluble extracellular molecules localized within the synaptic cleft. Notably, several mutations as well as auto-antibodies against components of these signaling complexes have been related to neuromuscular disorders. The recent years have witnessed strong progress in the understanding of molecular identities, architectures, and functions of NMJ macromolecules. Among these, prominent roles have been proposed for neural variants of the proteoglycan agrin, its receptor at NMJs composed of the lipoprotein receptor-related protein 4 (LRP4) and the muscle-specific kinase (MuSK), as well as the regulatory soluble synapse-specific protease Neurotrypsin. In this review we summarize the current state of the art regarding molecular structures and (agrin-dependent) canonical, as well as (agrin-independent) non-canonical, MuSK signaling mechanisms that underscore the formation of neuromuscular junctions, with the aim of providing a broad perspective to further stimulate molecular, cellular and tissue biology investigations on this fundamental intercellular contact.

Serum agrin and talin are increased in major depression while agrin and creatine phosphokinase are associated with chronic fatigue and fibromyalgia symptoms in depression

Chronic fatigue and fibromyalgia symptoms frequently occur in major depressive disorder (MDD). The pathophysiology of these symptoms may in part, be ascribed to activated immune pathways, although it is unclear whether muscular factors play a role in their onset. The aim of the present study is to examine the role of muscle proteins in major depression in association with symptoms of chronic fatigue and fibromyalgia. We measured serum levels of agrin, talin-2, titin, and creatine phosphokinase (CPK) as well as the FibroFatigue (FF), the Hamilton Depression Rating Scale (HAM-D) and the Beck Depression Inventory (BDI-II) scores in 60 MDD patients and 30 healthy controls. The results show a significant increase in agrin and talin-2 in MDD patients as compared with controls. There were highly significant correlations between agrin and HAM-D, BDI-II and FF scores. Agrin, but not talin or titin, was significantly and positively associated with all 12 items of the FF scale. We found that a large part of the variance in HAM-D (47.4%), BDI-II (43.4%) and FF (43.5%) scores was explained by the regression on agrin, smoking, female sex (positively associated) and education (inversely associated). CPK was significantly and inversely associated with the total FF score and with muscle and gastro-intestinal symptoms, fatigue, a flu-like malaise, headache and memory, autonomic and sleep disturbances. These results suggest that aberrations in neuromuscular (NMJs) and myotendinous junctions play a role in MDD and that the aberrations in NMJs coupled with lowered CPK may play a role in chronic fatigue and fibromyalgia symptoms in MDD. Moreover, the increase of agrin in MDD probably functions as part of the compensatory immune-regulatory system (CIRS).

Extracellular signal-regulated kinases 1 and 2 regulate neuromuscular junction and myofiber phenotypes in mammalian skeletal muscle

The neuromuscular junction is the synapse between a motor neuron of the spinal cord and a skeletal muscle fiber in the periphery. Reciprocal interactions between these excitable cells, and between them and others cell types present within the muscle tissue, shape the development, homeostasis and plasticity of skeletal muscle. An important aim in the field is to understand the molecular mechanisms underlying these cellular interactions, which include identifying the nature of the signals and receptors involved but also of the downstream intracellular signaling cascades elicited by them. This review focuses on work that shows that skeletal muscle fiber-derived extracellular signal-regulated kinases 1 and 2 (ERK1/2), ubiquitous and prototypical intracellular mitogen-activated protein kinases, have modulatory roles in the maintenance of the neuromuscular synapse and in the acquisition and preservation of fiber type identity in skeletal muscle.

Pathogenic effects of agrin V1727F mutation are isoform specific and decrease its expression and affinity for HSPGs and LRP4

Agrin is a large extracellular matrix protein whose isoforms differ in their tissue distribution and function. Motoneuron-derived y+z+ agrin regulates the formation of the neuromuscular junction (NMJ), while y-z- agrin is widely expressed and has diverse functions. Previously we identified a missense mutation (V1727F) in the second laminin globular (LG2) domain of agrin that causes severe congenital myasthenic syndrome. Here, we define pathogenic effects of the agrin V1727F mutation that account for the profound dysfunction of the NMJ. First, by expressing agrin variants in heterologous cells, we show that the V1727F mutation reduces the secretion of y+z+ agrin compared to wild type, whereas it has no effect on the secretion of y-z- agrin. Second, we find that the V1727F mutation significantly impairs binding of y+z+ agrin to both heparin and the low-density lipoprotein receptor-related protein 4 (LRP4) coreceptor. Third, molecular modeling of the LG2 domain suggests that the V1727F mutation primarily disrupts the y splice insert, and consistent with this we find that it partially occludes the contribution of the y splice insert to agrin binding to heparin and LRP4. Together, these findings identify several pathogenic effects of the V1727F mutation that reduce its expression and ability to bind heparan sulfate proteoglycan and LRP4 coreceptors involved in the muscle-specific kinase signaling pathway. These defects primarily impair the function of neural y+z+ agrin and combine to cause a severe CMS phenotype, whereas y-z- agrin function in other tissues appears preserved.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

Effect of Polarization and Chronic Inflammation on Macrophage Expression of Heparan Sulfate Proteoglycans and Biosynthesis Enzymes

Heparan sulfate (HS) proteoglycans on immune cells have the ability to bind to and regulate the bioactivity more than 400 bioactive protein ligands, including many chemokines, cytokines, and growth factors. This makes them important regulators of the phenotype and behavior of immune cells. Here we review how HS biosynthesis in macrophages is regulated during polarization and in chronic inflammatory diseases such as rheumatoid arthritis, atherosclerosis, asthma, chronic obstructive pulmonary disease and obesity, by analyzing published micro-array data and mechanistic studies in this area. We describe that macrophage expression of many HS biosynthesis and core proteins is strongly regulated by macrophage polarization, and that these expression patterns are recapitulated in chronic inflammation. Such changes in HS biosynthetic enzyme expression are likely to have a significant impact on the phenotype of macrophages in chronic inflammatory diseases by altering their interactions with chemokines, cytokines, and growth factors.

Association between preoperative peripheral blood mononuclear cell gene expression profiles, early postoperative organ function recovery potential and long-term survival in advanced heart failure patients undergoing mechanical circulatory support

BACKGROUND

Multiorgan dysfunction syndrome contributes to adverse outcomes in advanced heart failure (AdHF) patients after mechanical circulatory support (MCS) implantation and is associated with aberrant leukocyte activity. We tested the hypothesis that preoperative peripheral blood mononuclear cell (PBMC) gene expression profiles (GEP) can predict early postoperative improvement or non-improvement in patients undergoing MCS implantation. We believe this information may be useful in developing prognostic biomarkers.

METHODS & DESIGN

We conducted a study with 29 patients undergoing MCS-surgery in a tertiary academic medical center from 2012 to 2014. PBMC samples were collected one day before surgery (day -1). Clinical data was collected on day -1 and day 8 postoperatively. Patients were classified by Sequential Organ Failure Assessment score and Model of End-stage Liver Disease Except INR score (measured eight days after surgery): Group I = improving (both scores improved from day -1 to day 8, n = 17) and Group II = not improving (either one or both scores did not improve from day -1 to day 8, n = 12). RNA-sequencing was performed on purified mRNA and analyzed using Next Generation Sequencing Strand. Differentially expressed genes (DEGs) were identified by Mann-Whitney test with Benjamini-Hochberg correction. Preoperative DEGs were used to construct a support vector machine algorithm to predict Group I vs. Group II membership.

RESULTS

Out of 28 MCS-surgery patients alive 8 days postoperatively, one-year survival was 88% in Group I and 27% in Group II. We identified 28 preoperative DEGs between Group I and II, with an average 93% prediction accuracy. Out of 105 DEGs identified preoperatively between year 1 survivors and non-survivors, 12 genes overlapped with the 28 predictive genes.

CONCLUSIONS

In AdHF patients following MCS implantation, preoperative PBMC-GEP predicts early changes in organ function scores and correlates with long-term outcomes. Therefore, gene expression lends itself to outcome prediction and warrants further studies in larger longitudinal cohorts.

The extracellular matrix protein agrin promotes heart regeneration in mice

The adult mammalian heart is non-regenerative owing to the post-mitotic nature of cardiomyocytes. The neonatal mouse heart can regenerate, but only during the first week of life. Here we show that changes in the composition of the extracellular matrix during this week can affect cardiomyocyte growth and differentiation in mice. We identify agrin, a component of neonatal extracellular matrix, as required for the full regenerative capacity of neonatal mouse hearts. In vitro, recombinant agrin promotes the division of cardiomyocytes that are derived from mouse and human induced pluripotent stem cells through a mechanism that involves the disassembly of the dystrophin-glycoprotein complex, and Yap- and ERK-mediated signalling. In vivo, a single administration of agrin promotes cardiac regeneration in adult mice after myocardial infarction, although the degree of cardiomyocyte proliferation observed in this model suggests that there are additional therapeutic mechanisms. Together, our results uncover a new inducer of mammalian heart regeneration and highlight fundamental roles of the extracellular matrix in cardiac repair.

Heparan sulfate proteoglycans as key regulators of the mesenchymal niche of hematopoietic stem cells

The complex microenvironment that surrounds hematopoietic stem cells (HSCs) in the bone marrow niche involves different coordinated signaling pathways. The stem cells establish permanent interactions with distinct cell types such as mesenchymal stromal cells, osteoblasts, osteoclasts or endothelial cells and with secreted regulators such as growth factors, cytokines, chemokines and their receptors. These interactions are mediated through adhesion to extracellular matrix compounds also. All these signaling pathways are important for stem cell fates such as self-renewal, proliferation or differentiation, homing and mobilization, as well as for remodeling of the niche. Among these complex molecular cues, this review focuses on heparan sulfate (HS) structures and functions and on the role of enzymes involved in their biosynthesis and turnover. HS associated to core protein, constitute the superfamily of heparan sulfate proteoglycans (HSPGs) present on the cell surface and in the extracellular matrix of all tissues. The key regulatory effects of major medullar HSPGs are described, focusing on their roles in the interactions between hematopoietic stem cells and their endosteal niche, and on their ability to interact with Heparin Binding Proteins (HBPs). Finally, according to the relevance of HS moieties effects on this complex medullar niche, we describe recent data that identify HS mimetics or sulfated HS signatures as new glycanic tools and targets, respectively, for hematopoietic and mesenchymal stem cell based therapeutic applications.

Identification of a novel agrin-dependent pathway in cell signaling and adhesion within the erythroid niche

Establishment of cell–cell adhesion is crucial in embryonic development as well as within the stem cell niches of an adult. Adhesion between macrophages and erythroblasts is required for the formation of erythroblastic islands, specialized niches where erythroblasts proliferate and differentiate to produce red blood cells throughout life. The Eph family is the largest known family of receptor tyrosine kinases (RTKs) and controls cell adhesion, migration, invasion and morphology by modulating integrin and adhesion molecule activity and by modifying the actin cytoskeleton. Here, we identify the proteoglycan agrin as a novel regulator of Eph receptor signaling and characterize a novel mechanism controlling cell–cell adhesion and red cell development within the erythroid niche. We demonstrate that agrin induces clustering and activation of EphB1 receptors on developing erythroblasts, leading to the activation of α5β1 integrins. In agreement, agrin knockout mice display severe anemia owing to defective adhesion to macrophages and impaired maturation of erythroid cells. These results position agrin-EphB1 as a novel key signaling couple regulating cell adhesion and erythropoiesis.

Ability of circulating human hematopoietic lineage negative cells to support hematopoiesis

Hematopoietic stem cell (HSC) self-renewal is regulated by osteoblast and/or endothelial cells within the hematopoietic niche. However, the true identity of the supporting cells and the nature of the secreted factors remain uncertain. We developed a novel mouse model and analyzed whether circulating human peripheral hematopoietic lineage negative/AP+ (lin-/AP+) cells support hematopoiesis in vivo. Thus, immunocompromised (Rag) mice expressing thymidine kinase (Tk) under the control of the 3.6Col1α1 promoter (Tk-Rag) were treated with ganciclovir, resulting in osteoblast progenitor cell ablation and subsequent loss of hematopoiesis (evaluated by measuring mouse Ter119+ erythroid cells). Following hematopoietic cell depletion, human bone marrow-derived marrow stromal cells (MSCs) or lin-/AP+ cells were infused into Tk-Rag mice and compared with saline infusions. Ganciclovir significantly reduced (7.4-fold) Ter119+ cells in the bone marrow of Tk-Rag mice compared to saline injections. Infusion of either MSCs or lin-/AP+ cells into ganciclovir-treated mice resulted in a 3.3-fold and 2.7-fold increase (P < 0.01), respectively, in Ter119+ cells compared to mice receiving saline. Relative to lin-/AP- cells, lin-/AP+ cells expressed high levels of mesenchymal, endothelial, and hematopoiesis supporting genes. Thus, human peripheral blood lin-/AP+ cells represent a novel cell type capable of supporting hematopoiesis in a manner comparable to MSCs.

Proteoglycans in liver cancer

Proteoglycans are a group of molecules that contain at least one glycosaminoglycan chain, such as a heparan, dermatan, chondroitin, or keratan sulfate, covalently attached to the protein core. These molecules are categorized based on their structure, localization, and function, and can be found in the extracellular matrix, on the cell surface, and in the cytoplasm. Cell-surface heparan sulfate proteoglycans, such as syndecans, are the primary type present in healthy liver tissue. However, deterioration of the liver results in overproduction of other proteoglycan types. The purpose of this article is to provide a current summary of the most relevant data implicating proteoglycans in the development and progression of human and experimental liver cancer. A review of our work and other studies in the literature indicate that deterioration of liver function is accompanied by an increase in the amount of chondroitin sulfate proteoglycans. The alteration of proteoglycan composition interferes with the physiologic function of the liver on several levels. This article details and discusses the roles of syndecan-1, glypicans, agrin, perlecan, collagen XVIII/endostatin, endocan, serglycin, decorin, biglycan, asporin, fibromodulin, lumican, and versican in liver function. Specifically, glypicans, agrin, and versican play significant roles in the development of liver cancer. Conversely, the presence of decorin could potentially provide protective effects.

The Basement Membrane Proteoglycans Perlecan and Agrin: Something Old, Something New

Several members of the proteoglycan family are integral components of basement membranes; other proteoglycan family members interact with or bind to molecular residents of the basement membrane. Proteoglycans are polyfunctional molecules, for they derive their inherent bioactivity from the amino acid motifs embedded in the core protein structure as well as the glycosaminoglycan (GAG) chains that are covalently attached to the core protein. The presence of the covalently attached GAG chains significantly expands the "partnering" potential of proteoglycans, permitting them to interact with a broad spectrum of targets, including growth factors, cytokines, chemokines, and morphogens. Thus proteoglycans in the basement membrane are poised to exert diverse effects on the cells intimately associated with basement membranes.

Decoding the Matrix: Instructive Roles of Proteoglycan Receptors

The extracellular matrix is a dynamic repository harboring instructive cues that embody substantial regulatory dominance over many evolutionarily conserved intracellular activities, including proliferation, apoptosis, migration, motility, and autophagy. The matrix also coordinates and parses hierarchical information, such as angiogenesis, tumorigenesis, and immunological responses, typically providing the critical determinants driving each outcome. We provide the first comprehensive review focused on proteoglycan receptors, that is, signaling transmembrane proteins that use secreted proteoglycans as ligands, in addition to their natural ligands. The majority of these receptors belong to an exclusive subset of receptor tyrosine kinases and assorted cell surface receptors that specifically bind, transduce, and modulate fundamental cellular processes following interactions with proteoglycans. The class of small leucine-rich proteoglycans is the most studied so far and constitutes the best understood example of proteoglycan-receptor interactions. Decorin and biglycan evoke autophagy and immunological responses that deter, suppress, or exacerbate pathological conditions such as tumorigenesis, angiogenesis, and chronic inflammatory disease. Basement membrane-associated heparan sulfate proteoglycans (perlecan, agrin, and collagen XVIII) represent a unique cohort and provide proteolytically cleaved bioactive fragments for modulating cellular behavior. The receptors that bind the genuinely multifactorial and multivalent proteoglycans represent a nexus in understanding basic biological pathways and open new avenues for therapeutic and pharmacological intervention.

Effect of systemic heparan sulfate haploinsufficiency on steady state hematopoiesis and engraftment of hematopoietic stem cells

Heparan sulfate (HS) proteoglycans on stromal and hematopoietic stem/progenitor cells (HSPC) help form the stem cell niche, co-localize molecules that direct stem cell fate, and modulate HSPC homing and retention. Inhibition of HS function mobilizes marrow HSPC. In vitro, HSPC maintenance is influenced by stromal HS structure and concentration. Because inhibition of HS activity or synthesis may be developed for HSPC transplantation, it is important to examine if systemic HS deficiency influences hematopoiesis in vivo. In a transgenic mouse model of HS haploinsufficiency, we examined endogenous hematopoiesis and engraftment of allogeneic bone marrow. Endogenous hematopoiesis was normal except gender-specific alterations in peripheral blood monocyte and platelet counts. Donor engraftment was achieved in all mice following myeloablative irradiation, but HS deficiency in the stromal microenvironment, on HSPC, or both (the 3 test conditions), was associated with a trend towards lower donor engraftment percentage in the bone marrow. Following non-myeloablative irradiation, competitive engraftment was achieved in 22% of mice in the test conditions, vs 50% of control animals (P = 0.03). HS deficiency did not re-direct donor engraftment from bone marrow to spleen or liver. Normal HS levels in the stromal microenvironment and HSPC are required for HSPC engraftment following non-myeloablative conditioning.

RING finger protein 11 (RNF11) modulates susceptibility to 6-OHDA-induced nigral degeneration and behavioral deficits through NF-κB signaling in dopaminergic cells

Chronic activation of the NF-κB pathway is associated with progressive neurodegeneration in Parkinson's disease (PD). Given the role of neuronal RING finger protein 11 (RNF11) as a negative regulator of the NF-κB pathway, in this report we investigated the function of RNF11 in dopaminergic cells in PD-associated neurodegeneration. We found that RNF11 knockdown in an in vitro model of PD mediated protection against 6-OHDA-induced toxicity. In converse, over-expression of RNF11 enhanced 6-OHDA-induced dopaminergic cell death. Furthermore, by directly manipulating NF-κB signaling, we showed that the observed RNF11-enhanced 6-OHDA toxicity is mediated through inhibition of NF-κB-dependent transcription of TNF-α, antioxidants GSS and SOD1, and anti-apoptotic factor BCL2. Experiments in an in vivo 6-OHDA rat model of PD recapitulated the in vitro results. In vivo targeted RNF11 over-expression in nigral neurons enhanced 6-OHDA toxicity, as evident by increased amphetamine-induced rotations and loss of nigral dopaminergic neurons as compared to controls. This enhanced toxicity was coupled with the downregulation of NF-κB transcribed GSS, SOD1, BCL2, and neurotrophic factor BDNF mRNA levels, in addition to decreased TNF-α mRNA levels in ventral mesenchephalon samples. In converse, knockdown of RNF11 was associated with protective phenotypes and increased expression of above-mentioned NF-κB transcribed genes. Collectively, our in vitro and in vivo data suggest that RNF11-mediated inhibition of NF-κB in dopaminergic cells exaggerates 6-OHDA toxicity by inhibiting neuroprotective responses while loss of RNF11 inhibition on NF-κB activity promotes neuronal survival. The decreased expression of RNF11 in surviving cortical and nigral tissue detected in PD patients, thus implies a compensatory response in the diseased brain to PD-associated insults. In summary, our findings demonstrate that RNF11 in neurons can modulate susceptibility to 6-OHDA toxicity through NF-κB mediated responses. This neuron-specific role of RNF11 in the brain has important implications for targeted therapeutics aimed at preventing neurodegeneration.