Hedgehog-dependent regulation of angiogenesis and myogenesis is impaired in aged mice

Comparison of Three Antagonists of Hedgehog Pathway to Promote Skeletal Muscle Regeneration after High Dose Irradiation

The current geopolitical context has brought the radiological nuclear risk to the forefront of concerns. High-dose localized radiation exposure leads to the development of a musculocutaneous radiation syndrome affecting the skin and subcutaneous muscles. Despite the implementation of a gold standard treatment based on an invasive surgical procedure coupled with autologous cell therapy, a muscular defect frequently persists. Targeting the modulation of the Hedgehog (Hh) signaling pathway appears to be a promising therapeutic approach. Activation of this pathway enhances cell survival and promotes proliferation after irradiation, while inhibition by Cyclopamine facilitates differentiation. In this study, we compared the effects of three antagonists of Hh, Cyclopamine (CA), Vismodegib (VDG) and Sonidegib (SDG) on differentiation. A stable cell line of murine myoblasts, C2C12, was exposed to X-ray radiation (5 Gy) and treated with CA, VDG or SDG. Analysis of proliferation, survival (apoptosis), morphology, myogenesis genes expression and proteins production were performed. According to the results, VDG does not have a significant impact on C2C12 cells. SDG increases the expression/production of differentiation markers to a similar extent as CA, while morphologically, SDG proves to be more effective than CA. To conclude, SDG can be used in the same way as CA but already has a marketing authorization with an indication against basal cell cancers, facilitating their use in vivo. This proof of concept demonstrates that SDG represents a promising alternative to CA to promotes differentiation of murine myoblasts. Future studies on isolated and cultured satellite cells and in vivo will test this proof of concept.

Impact of thyroid hormone perturbations in adult mice: brain weight and blood vessel changes, gene expression variation, and neurobehavioral outcomes

Mouse models of hyper- and hypothyroidism were used to examine the effects of thyroid hormone (TH) dyshomeostasis on the aging mammalian brain. 13-14 month-old mice were treated for 4months with either levothyroxine (hyperthyroid) or a propylthiouracil and methimazole combination (PTU/Met; hypothyroid). Hyperthyroid mice performed better on Morris Water Maze than control mice, while hypothyroid mice performed worse. Brain weight was increased in thyroxine-treated, and decreased in PTU/Met-treated animals. The brain weight change was strongly correlated with circulating and tissue T4. Quantitative measurements of microvessels were compared using digital neuropathologic methods. There was an increase in microvessel area in hyperthyroid mice. Hypothyroid mice showed a trend for elevated glial fibrillary acidic protein-immunoreactive astrocytes, indicating an increase in neuroinflammation. Gene expression alterations were associated with TH perturbation and astrocyte-expressed transcripts were particularly affected. For example, expression of Gli2 and Gli3, mediators in the Sonic Hedgehog signaling pathway, were strongly impacted by both treatments. We conclude that TH perturbations produce robust neurobehavioral, pathological, and brain gene expression changes in aging mouse models.

Praliciguat Promotes Ischemic Leg Reperfusion in Leptin Receptor-Deficient Mice

BACKGROUND

Lower-limb peripheral artery disease is one of the major complications of diabetes. Peripheral artery disease is associated with poor limb and cardiovascular prognoses, along with a dramatic decrease in life expectancy. Despite major medical advances in the treatment of diabetes, a substantial therapeutic gap remains in the peripheral artery disease population. Praliciguat is an orally available sGC (soluble guanylate cyclase) stimulator that has been reported both preclinically and in early stage clinical trials to have favorable effects in metabolic and hemodynamic outcomes, suggesting that it may have a potential beneficial effect in peripheral artery disease.

METHODS

We evaluated the effect of praliciguat on hind limb ischemia recovery in a mouse model of type 2 diabetes. Hind limb ischemia was induced in leptin receptor-deficient (Lepr^db/db) mice by ligation and excision of the left femoral artery. Praliciguat (10 mg/kg/day) was administered in the diet starting 3 days before surgery.

RESULTS

Twenty-eight days after surgery, ischemic foot perfusion and function parameters were better in praliciguat-treated mice than in vehicle controls. Improved ischemic foot perfusion was not associated with either improved traditional cardiovascular risk factors (ie, weight, glycemia) or increased angiogenesis. However, treatment with praliciguat significantly increased arteriole diameter, decreased ICAM1 (intercellular adhesion molecule 1) expression, and prevented the accumulation of oxidative proangiogenic and proinflammatory muscle fibers. While investigating the mechanism underlying the beneficial effects of praliciguat therapy, we found that praliciguat significantly downregulated Myh2 and Cxcl12 mRNA expression in cultured myoblasts and that conditioned medium form praliciguat-treated myoblast decreased ICAM1 mRNA expression in endothelial cells. These results suggest that praliciguat therapy may decrease ICAM1 expression in endothelial cells by downregulating Cxcl12 in myocytes.

CONCLUSIONS

Our results demonstrated that praliciguat promotes blood flow recovery in the ischemic muscle of mice with type 2 diabetes, at least in part by increasing arteriole diameter and by downregulating ICAM1 expression.

GLI3 regulates muscle stem cell entry into GAlert and self-renewal

Satellite cells are required for the growth, maintenance, and regeneration of skeletal muscle. Quiescent satellite cells possess a primary cilium, a structure that regulates the processing of the GLI family of transcription factors. Here we find that GLI3 processing by the primary cilium plays a critical role for satellite cell function. GLI3 is required to maintain satellite cells in a G0 dormant state. Strikingly, satellite cells lacking GLI3 enter the GAlert state in the absence of injury. Furthermore, GLI3 depletion stimulates expansion of the stem cell pool. As a result, satellite cells lacking GLI3 display rapid cell-cycle entry, increased proliferation and augmented self-renewal, and markedly enhanced regenerative capacity. At the molecular level, we establish that the loss of GLI3 induces mTORC1 signaling activation. Therefore, our results provide a mechanism by which GLI3 controls mTORC1 signaling, consequently regulating muscle stem cell activation and fate.

Muscle regeneration after high-dose radiation exposure: therapeutic potential of Hedgehog pathway modulation?

Purpose: Intentional or accidental exposure of relatively large as well as localized areas of the skin to ionizing radiation can lead to severe damage of many of its cellular components and cutaneous radiation syndrome. Patients can be treated with an invasive surgical procedure coupled with autologous cell therapy. However, this approach remains perfectible, especially for muscle repair. Indeed, a severe underlying muscle defect persists, in particular because of the damage to the satellite cells which ensure muscle regeneration. To overcome these shortcomings, a solution could be to develop new therapeutic strategies based on pharmacological treatments to improve post-irradiation muscle regeneration. In this study, we focus on the Hedgehog signaling pathway as a target, due to its involvement in myogenesis.Materials and methods: To evaluate the benefit of the pro-myogenic Hedgehog signaling pathway modulation, recombinant Sonic Hedgehog (rShh; agonist) or Cyclopamine (antagonist) were used in a stable cell line of mouse C2C12 myoblasts exposed to radiation (X-rays; 5 Gy). Our in vitro studies were carried out under either proliferation or differentiation conditions. Proliferation, migration, survival (apoptosis) and expression of myogenic genes/proteins were evaluated.Results: A high dose of radiation was shown to exert a serious negative impact in our in vitro model of mouse muscle progenitors after irradiation in proliferation or differentiation conditions. Interestingly, Hh pathway stimulation by rShh promotes the proliferation of myoblasts and their survival while its blockade by Cyclopamine significantly increases cell differentiation toward mature myotubes.Conclusion: These data suggest that, after irradiation, the sequence of activation and inhibition of the Hh pathway could allow rescue and proliferation of satellite cells, followed by their differentiation to regenerate new fibers. On the basis of these encouraging in vitro results, the second phase of our study will involve the in vivo validation of this treatment in a new murine model of ultra-localized muscle irradiation.

Developmental and regenerative paradigms of cilia regulated hedgehog signaling

Primary cilia are immotile appendages that have evolved to receive and interpret a variety of different extracellular cues. Cilia play crucial roles in intercellular communication during development and defects in cilia affect multiple tissues accounting for a heterogeneous group of human diseases called ciliopathies. The Hedgehog (Hh) signaling pathway is one of these cues and displays a unique and symbiotic relationship with cilia. Not only does Hh signaling require cilia for its function but the majority of the Hh signaling machinery is physically located within the cilium-centrosome complex. More specifically, cilia are required for both repressing and activating Hh signaling by modifying bifunctional Gli transcription factors into repressors or activators. Defects in balancing, interpreting or establishing these repressor/activator gradients in Hh signaling either require cilia or phenocopy disruption of cilia. Here, we will summarize the current knowledge on how spatiotemporal control of the molecular machinery of the cilium allows for a tight control of basal repression and activation states of the Hh pathway. We will then discuss several paradigms on how cilia influence Hh pathway activity in tissue morphogenesis during development. Last, we will touch on how cilia and Hh signaling are being reactivated and repurposed during adult tissue regeneration. More specifically, we will focus on mesenchymal stem cells within the connective tissue and discuss the similarities and differences of how cilia and ciliary Hh signaling control the formation of fibrotic scar and adipose tissue during fatty fibrosis of several tissues.

Hedgehog signaling promotes endoneurial fibroblast migration and Vegf-A expression following facial nerve injury

BACKGROUND

Peripheral nerve injuries are a common clinical problem which may result in permanent loss of motor or sensory function. A better understanding of the signaling pathways that lead to successful nerve regeneration may help in discovering new therapeutic targets. The Hedgehog (Hh) signaling pathway plays significant roles in nerve development and regeneration. In a mouse model of facial nerve injury, Hedgehog-responsive fibroblasts increase in number both at the site of injury and within the distal nerve. However, the role of these cells in facial nerve regeneration is not fully understood. We hypothesize that the Hh pathway plays an angiogenic and pro-migratory role following facial nerve injury.

METHODS

Hedgehog pathway modulators were applied to murine endoneurial fibroblasts isolated from the murine facial nerve. The impact of pathway modulation on endoneurial fibroblast migration and cell proliferation was assessed. Gene expression changes of known Hedgehog target genes and the key angiogenic factor Vegf-A were determined by qPCR. In vivo, mice were treated with pathway agonist (SAG21k) and injured facial nerve specimens were analyzed via immunofluorescence and in situ hybridization.

RESULTS

Hedgehog pathway activation in facial nerve fibroblasts via SAG21k treatment increases Gli1 and Ptch1 expression, the rate of cellular migration, and Vegf-A expression in vitro. In vivo, expression of Gli1 and Vegf-A expression appears to increase after injury, particularly at the site of nerve injury and the distal nerve, as detected by immunofluorescence and in situ hybridization. Additionally, Gli1 transcripts co-localize with Vegf-A following transection injury to the facial nerve.

DISCUSSION

These findings describe an angiogenic and pro-migratory role for the Hedgehog pathway mediated through effects on nerve fibroblasts. Given the critical role of Vegf-A in nerve regeneration, modulation of this pathway may represent a potential therapeutic target to improve facial nerve regeneration following injury.

Restoring Endothelial Function by Targeting Desert Hedgehog Downstream of Klf2 Improves Critical Limb Ischemia in Adults

RATIONALE

Klf (kruppel-like factor) 2 is critical to establish and maintain endothelial integrity.

OBJECTIVE

Therefore, determining upstream and downstream mediators of Klf2 would lead to alternative therapeutic targets in cardiovascular disease management.

METHODS AND RESULTS

Here we identify Dhh (desert hedgehog) as a downstream effector of Klf2, whose expression in endothelial cells (ECs) is upregulated by shear stress and decreased by inflammatory cytokines. Consequently, we show that Dhh knockdown in ECs promotes endothelial permeability and EC activation and that Dhh agonist prevents TNF-α (tumor necrosis factor alpha) or glucose-induced EC dysfunction. Moreover, we demonstrate that human critical limb ischemia, a pathological condition linked to diabetes mellitus and inflammation, is associated to major EC dysfunction. By recreating a complex model of critical limb ischemia in diabetic mice, we found that Dhh-signaling agonist significantly improved EC function without promoting angiogenesis, which subsequently improved muscle perfusion.

CONCLUSION

Restoring EC function leads to significant critical limb ischemia recovery. Dhh appears to be a promising target, downstream of Klf2, to prevent the endothelial dysfunction involved in ischemic vascular diseases.

Role of Hedgehog Signaling in Vasculature Development, Differentiation, and Maintenance

The role of Hedgehog (Hh) signaling in vascular biology has first been highlighted in embryos by Pepicelli et al. in 1998 and Rowitch et al. in 1999. Since then, the proangiogenic role of the Hh ligands has been confirmed in adults, especially under pathologic conditions. More recently, the Hh signaling has been proposed to improve vascular integrity especially at the blood–brain barrier (BBB). However, molecular and cellular mechanisms underlying the role of the Hh signaling in vascular biology remain poorly understood and conflicting results have been reported. As a matter of fact, in several settings, it is currently not clear whether Hh ligands promote vessel integrity and quiescence or destabilize vessels to promote angiogenesis. The present review relates the current knowledge regarding the role of the Hh signaling in vasculature development, maturation and maintenance, discusses the underlying proposed mechanisms and highlights controversial data which may serve as a guideline for future research. Most importantly, fully understanding such mechanisms is critical for the development of safe and efficient therapies to target the Hh signaling in both cancer and cardiovascular/cerebrovascular diseases.

Intercellular Communication between Hepatic Cells in Liver Diseases

Liver diseases are perpetuated by the orchestration of hepatocytes and other hepatic non-parenchymal cells. These cells communicate and regulate with each other by secreting mediators such as peptides, hormones, and cytokines. Extracellular vesicles (EVs), small particles secreted from cells, contain proteins, DNAs, and RNAs as cargos. EVs have attracted recent research interests since they can communicate information from donor cells to recipient cells thereby regulating physiological events via delivering of specific cargo mediators. Previous studies have demonstrated that liver cells secrete elevated numbers of EVs during diseased conditions, and those EVs are internalized into other liver cells inducing disease-related reactions such as inflammation, angiogenesis, and fibrogenesis. Reactions in recipient cells are caused by proteins and RNAs carried in disease-derived EVs. This review summarizes cell-to-cell communication especially via EVs in the pathogenesis of liver diseases and their potential as a novel therapeutic target.

Isoflurane Post-conditioning Ameliorates Cerebral Ischemia/Reperfusion Injury by Enhancing Angiogenesis Through Activating the Shh/Gli Signaling Pathway in Rats

Background: Stroke is the second leading cause of death worldwide. Angiogenesis facilitates the formation of microvascular networks and promotes recovery after stroke. The Shh/Gli signaling pathway is implicated in angiogenesis and cerebral ischemia-reperfusion (I/R) injury. This study aimed at investigating the influence of isoflurane (ISO) post-conditioning on brain lesions and angiogenesis after I/R injury.

Methods: Adult male Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO), 1.5 h occlusion and 24 h reperfusion (MCAO/R). The ISO post-conditioning group (ISO group) received 1 h ISO post-conditioning when reperfusion was initiated. Neurobehavioral tests, TTC staining, HE staining, Nissl staining, TUNEL staining, immunofluorescence (IF), immunohistochemistry (IH) and Western blot were performed to assess the effect of ISO after I/R injury.

Results: ISO post-conditioning resulted in lower infarct volumes and neurologic deficit scores, higher rate of neurons survival, and less damaged and apoptotic cells after cerebral I/R injury in rats. Meanwhile, ISO post-conditioning significantly increased the expression levels of vascular endothelial growth factor (VEGF) and CD34 in the ischemic penumbra, relative to that in the Sham and I/R groups. However, cyclopamine, the specific inhibitor of the Sonic hedgehog (Shh) signaling pathway, decreased the expression levels of VEGF and CD34, and counteracted the protective effects of ISO post-conditioning against I/R injury in rats.

Conclusions: ISO post-conditioning enhances angiogenesis in vivo partly via the Shh/Gli signaling pathway. Thus, Shh/Gli may represent new therapeutic targets for aiding recovery from stroke.

Dl-3-N-butylphthalide promotes angiogenesis and upregulates sonic hedgehog expression after cerebral ischemia in rats

INTRODUCTION

Dl-3-N-butylphthalide (NBP), a small molecule drug used clinically in the acute phase of ischemic stroke, has been shown to improve functional recovery and promote angiogenesis and collateral vessel circulation after experimental cerebral ischemia. However, the underlying molecular mechanism is unknown.

AIMS

To explore the potential molecular mechanism of angiogenesis induced by NBP after cerebral ischemia.

RESULTS

NBP treatment attenuated body weight loss, reduced brain infarct volume, and improved neurobehavioral outcomes during focal ischemia compared to the control rats (P < 0.05). NBP increased the number of CD31⁺ microvessels, the number of CD31⁺ /BrdU⁺ proliferating endothelial cells, and the functional vascular density (P < 0.05). Further study demonstrated that NBP also promoted the expression of vascular endothelial growth factor and angiopoietin-1 (P < 0.05), which was accompanied by upregulated sonic hedgehog expression in astrocytes in vivo and in vitro.

CONCLUSION

NBP treatment promoted the expression of vascular endothelial growth factor and angiopoietin-1, induced angiogenesis, and improved neurobehavioral recovery. These effects were associated with increased sonic hedgehog expression after NBP treatment. Our results broadened the clinical application of NBP to include the later phase of ischemia.

Sonic hedgehog regulation of cavernous nerve regeneration and neurite formation in aged pelvic plexus

INTRODUCTION

Erectile dysfunction (ED) is a significant health concern that greatly impacts quality of life, and is common in men as they age, impacting 52% of men between the ages of 40 and 70. A significant underlying cause of ED development is injury to the cavernous nerve (CN), a peripheral nerve that innervates the penis. CN injury also occurs in up to 82% of prostatectomy patients. We recently showed that Sonic hedgehog (SHH) protein delivered by peptide amphiphile (PA) nanofiber hydrogel to the CN and penis of a prostatectomy model of CN injury, is neuroprotective, accelerates CN regeneration, improves erectile function ~60%, preserves penile smooth muscle 56% and suppresses collagen deposition 30%. This regenerative potential is substantial in an adult prostatectomy model (P120). However prostatectomy patients are typically older (61.5 ± 9.6 years) and our models should mimic patient conditions more effectively when considering translation. In this study we examine regenerative potential in an aged prostatectomy model (P200-329).

METHODS

The caudal portion of the pelvic ganglia (MPG) and CN were dissected from adult (n = 11), and aged (n = 13) Sprague Dawley rats, and were grown in organ culture 3 days. Uninjured and 2 day CN crushed MPG/CN were exposed to Affi-Gel beads containing SHH protein, PBS (control), or 5e1 SHH inhibitor. Neurites were quantified by counting the number of growth cones normalized by tissue perimeter (mm) and immunohistochemistry for SHH, patched1 (PTCH1), smoothened (SMO), GLI1-3, and GAP43 were performed.

RESULTS

SHH treatment increased neurites 3.5-fold, in uninjured adult, and 5.7-fold in aged rats. Two days after CN crush, SHH treatment increased neurites 1.8-fold in adult rats and 2.5-fold in aged rats. SHH inhibition inhibited neurite formation in uninjured MPG/CN but not in 2 day CN crushed MPG/CN. PTCH1 and SMO (SHH receptors), and SHH transcriptional activators/repressors, GLI1-3, were abundant in aged MPG/CN with unaltered localization. ROCK1 was induced with SHH treatment.

CONCLUSIONS

Reintroduction of SHH protein in an aged prostatectomy model is even more effective in promoting neurite formation/CN regeneration than in the adult. The first 48 h after CN injury are a critical window when growth factors are released, that impact later neurite formation. These studies are significant because most prostatectomy patients are not young and healthy, as with adult rats, so the aged prostatectomy model will more accurately simulate ED patient response. Understanding how neurite formation changes with age is critical for clinical translation of SHH PA to prostatectomy patients.

Gene correlation network analysis to identify regulatory factors in idiopathic pulmonary fibrosis

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a severe lung disease characterised by extensive pathological changes. The objective for this study was to identify the gene network and regulators underlying disease pathology in IPF and its association with lung function.

METHODS

Lung Tissue Research Consortium dataset with 262 IPF and control subjects (GSE47460) was randomly divided into two non-overlapping groups for cross-validated differential gene expression analysis. Consensus weighted gene coexpression network analysis identified overlapping coexpressed gene modules between both IPF groups. Modules were correlated with lung function (diffusion capacity, DL_CO; forced expiratory volume in 1 s, FEV₁; forced vital capacity, FVC) and enrichment analyses used to identify biological function and transcription factors. Module correlation with miRNA data (GSE72967) identified associated regulators. Clinical relevance in IPF was assessed in a peripheral blood gene expression dataset (GSE93606) to identify modules related to survival.

RESULTS

Correlation network analysis identified 16 modules in IPF. Upregulated modules were associated with cilia, DNA replication and repair, contractile fibres, B-cell and unfolded protein response, and extracellular matrix. Downregulated modules were associated with blood vessels, T-cell and interferon responses, leucocyte activation and degranulation, surfactant metabolism, and cellular metabolic and catabolic processes. Lung function correlated with nine modules (eight with DL_CO, five with FVC). Intermodular network of transcription factors and miRNA showed clustering of fibrosis, immune response and contractile modules. The cilia-associated module was able to predict survival (p=0.0097) in an independent peripheral blood IPF cohort.

CONCLUSIONS

We identified a correlation gene expression network with associated regulators in IPF that provides novel insight into the pathological process of this disease.

Sonic Hedgehog Signaling Pathway in Endothelial Progenitor Cell Biology for Vascular Medicine

The Hedgehog (HH) signaling pathway plays an important role in embryonic and postnatal vascular development and in maintaining the homeostasis of organs. Under physiological conditions, Sonic Hedgehog (SHH), a secreted protein belonging to the HH family, regulates endothelial cell growth, promotes cell migration and stimulates the formation of new blood vessels. The present review highlights recent advances made in the field of SHH signaling in endothelial progenitor cells (EPCs). The canonical and non-canonical SHH signaling pathways in EPCs and endothelial cells (ECs) related to homeostasis, SHH signal transmission by extracellular vesicles (EVs) or exosomes containing single-strand non-coding miRNAs and impaired SHH signaling in cardiovascular diseases are discussed. As a promising therapeutic tool, the possibility of using the SHH signaling pathway for the activation of EPCs in patients suffering from cardiovascular diseases is further explored.

Sonic hedgehog regulation of human rhabdosphincter muscle:Potential implications for treatment of stress urinary incontinence

AIMS

Rhabdosphincter (RS) muscle injury occurs during prostatectomy, and is a leading cause of stress urinary incontinence (SUI). Current SUI treatments engender significant side effects, which negatively impact patient quality of life. Thus an unmet need exists to develop novel RS regeneration methods. We have shown that Sonic hedgehog (SHH) is a critical regulator of penile smooth muscle, and we have developed novel peptide amphiphile nanofiber hydrogel delivery of SHH protein to the penis to regenerate smooth muscle after prostatectomy induced injury. If similar SHH signaling mechanisms regulate RS muscle homeostasis, this innovative technology may be adapted for RS regeneration post-prostatectomy. We examine the SHH pathway in human RS muscle.

METHODS

Human RS obtained during radical cystoprostatectomy (n = 13), underwent SHH pathway analysis. Primary cultures were established (n = 5), and RS cells were treated with SHH protein, SHH inhibitor, or PBS (control). Immunohistochemical analysis for SHH pathway, skeletal muscle actin, and trichrome stain were performed. RS growth was quantified at 3 and 6 days.

RESULTS

SHH, it is receptors patched and smoothened, and transcriptional activators, GLI proteins, were identified in human RS muscle. At 3 and 6 days, RS cells increased 62% and 78% (P = 0.0001) with SHH treatment and decreased 40% (P = 0.0001) and 18% (P = 0.039) with SHH inhibition.

CONCLUSIONS

The SHH pathway was identified in human RS. RS growth increased with SHH treatment, indicating intervention may be possible to enhance RS regeneration, and impact SUI. Peptide amphiphile delivery of SHH may be applicable for RS regeneration and SUI prevention.

Emerging Roles of Sonic Hedgehog in Adult Neurological Diseases: Neurogenesis and Beyond

Sonic hedgehog (Shh), a member of the hedgehog (Hh) family, was originally recognized as a morphogen possessing critical characters for neural development during embryogenesis. Recently, however, Shh has emerged as an important modulator in adult neural tissues through different mechanisms such as neurogenesis, anti-oxidation, anti-inflammation, and autophagy. Therefore, Shh may potentially have clinical application in neurodegenerative diseases and brain injuries. In this article, we present some examples, including ours, to show different aspects of Shh signaling and how Shh agonists or mimetics are used to alter the neuronal fates in various disease models, both in vitro and in vivo. Other potential mechanisms that are discussed include alteration of mitochondrial function and anti-aging effect; both are critical for age-related neurodegenerative diseases. A thorough understanding of the protective mechanisms elicited by Shh may provide a rationale to design innovative therapeutic regimens for various neurodegenerative diseases.

The role of angiogenesis in Group 3 medulloblastoma pathogenesis and survival

Background

Of the 4 medulloblastoma subgroups, Group 3 is the most aggressive but the importance of angiogenesis is unknown. This study sought to determine the role of angiogenesis and identify clinically relevant biomarkers of tumor vascularity and survival in Group 3 medulloblastoma.

Methods

VEGFA mRNA expression and survival from several patient cohorts were analyzed. Group 3 xenografts were implanted intracranially in nude rats. Dynamic susceptibility weighted (DSC) MRI and susceptibility weighted imaging (SWI) were obtained. DSC MRI was used to calculate relative cerebral blood volume (rCBV) and flow (rCBF). Tumor vessel density and rat vascular endothelial growth factor alpha (VEGFA) expression were determined.

Results

Patient VEGFA mRNA levels were significantly elevated in Group 3 compared with the other subgroups (P < 0.001) and associated with survival. Xenografts D283, D341, and D425 were identified as Group 3 by RNA hierarchical clustering and MYC amplification. The D283 group had the lowest rCBV and rCBF, followed by D341 and D425 (P < 0.05). These values corresponded to histological vessel density (P < 0.05), rat VEGFA expression (P < 0.05), and survival (P = 0.002). Gene set enrichment analysis identified 5 putative genes with expression profiles corresponding with these findings: RNH1, SCG2, VEGFA, AGGF1, and PROK2. SWI identified 3 xenograft-independent categories of intratumoral vascular architecture with distinct survival (P = 0.004): organized, diffuse microvascular, and heterogeneous.

Conclusions

Angiogenesis plays an important role in Group 3 medulloblastoma pathogenesis and survival. DSC MRI and SWI are clinically relevant biomarkers for tumor vascularity and overall survival and can be used to direct the use of antivascular therapies for patients with Group 3 medulloblastoma.

G Protein-Coupled Receptors at the Crossroad between Physiologic and Pathologic Angiogenesis: Old Paradigms and Emerging Concepts

G protein-coupled receptors (GPCRs) have been implicated in transmitting signals across the extra- and intra-cellular compartments, thus allowing environmental stimuli to elicit critical biological responses. As GPCRs can be activated by an extensive range of factors including hormones, neurotransmitters, phospholipids and other stimuli, their involvement in a plethora of physiological functions is not surprising. Aberrant GPCR signaling has been regarded as a major contributor to diverse pathologic conditions, such as inflammatory, cardiovascular and neoplastic diseases. In this regard, solid tumors have been demonstrated to activate an angiogenic program that relies on GPCR action to support cancer growth and metastatic dissemination. Therefore, the manipulation of aberrant GPCR signaling could represent a promising target in anticancer therapy. Here, we highlight the GPCR-mediated angiogenic function focusing on the molecular mechanisms and transduction effectors driving the patho-physiological vasculogenesis. Specifically, we describe evidence for the role of heptahelic receptors and associated G proteins in promoting angiogenic responses in pathologic conditions, especially tumor angiogenesis and progression. Likewise, we discuss opportunities to manipulate aberrant GPCR-mediated angiogenic signaling for therapeutic benefit using innovative GPCR-targeted and patient-tailored pharmacological strategies.

Sonic hedgehog (SHH) signaling improves the angiogenic potential of Wharton's jelly-derived mesenchymal stem cells (WJ-MSC)

Background

Wharton’s jelly-derived mesenchymal stem cells (WJ-MSC) show remarkable therapeutic potential to repair tissue upon injury via paracrine signaling by secreting diverse trophic factors that promote angiogenesis. However, the mechanisms and signaling pathways that regulate the induction of these specific factors are still mostly unknown. Emerging evidence suggests that Sonic hedgehog (SHH) plays a central role in angiogenesis and tissue maintenance. However, its contribution to the angiogenic potential of MSC has not been fully addressed. The aim of this work was to characterize the expression of the SHH pathway components in WJ-MSC primary cultures and to evaluate their angiogenic responsiveness to SHH signaling.

Methods

Primary cell cultures obtained from human umbilical cords were treated with pharmacological modulators of the SHH pathway. We evaluated the modulation of diverse trophic factors in cell lysates, conditioned medium, and functional in vitro assays. In addition, we determined the angiogenic potential of the SHH pathway in the chicken chorioallantoic membrane, an in vivo model.

Results

Our results show that WJ-MSC express components of the canonical SHH pathway and are activated by its signaling. In fact, we provide evidence of basal autocrine/paracrine SHH signaling in WJ-MSC. SHH pathway stimulation promotes the secretion of angiogenic factors such as activin A, angiogenin, angiopoietin 1, granulocyte-macrophage colony-stimulating factor, matrix metallometallopeptidase -9, and urokinase-type plasminogen activator, enhancing the pro-angiogenic capabilities of WJ-MSC both in vitro and in vivo.

Conclusion

WJ-MSC are a cell population responsive to SHH pathway stimulation. Basal SHH signaling is in part responsible for the angiogenic inductive properties of WJ-MSC. Overall, exogenous activation of the SHH pathway enhances the angiogenic properties of WJ-MSC, making this cell population an ideal target for treating tissue injury.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0653-8) contains supplementary material, which is available to authorized users.

Hh signaling in regeneration of the ischemic heart

Myocardial infarction (MI) is caused by the occlusion of a coronary artery due to underlying atherosclerosis complicated by localized thrombosis. The blockage of blood flow leads to cardiomyocyte (CM) death in the infarcted area. Adult mammalian cardiomyocytes have little capacity to proliferate in response to injury; however, some pathways active during embryogenesis and silent during adult life are recruited in response to tissue injury. One such example is hedgehog (Hh) signaling. Hh is involved in the embryonic development of the heart and coronary vascular system. Pathological conditions including ischemia activate Hh signaling in adult tissues. This review highlights the involvement of Hh signaling in ischemic tissue regeneration with a particular emphasis on heart regeneration and discusses its potential role as a therapeutic agent.

Skeletal Muscle Microvasculature: A Highly Dynamic Lifeline

Skeletal muscle is highly irrigated by blood vessels. Beyond oxygen and nutrient supply, new vessel functions have been identified. This review presents vessel microanatomy and functions at tissue, cellular, and molecular levels. Mechanisms of vessel plasticity are described during skeletal muscle development and acute regeneration, and in physiological and pathological contexts.

Denervation in Femoral Artery-Ligated Hindlimbs Diminishes Ischemic Recovery Primarily via Impaired Arteriogenesis

Aims

Multiple factors regulate arteriogenesis. Peripheral nerves play a crucial role in vascular remodeling, but the function of peripheral nerves during arteriogenesis is obscure. Our study investigated the contribution of denervation to arteriogenesis during post-ischemic recovery from hindlimb femoral artery ligation.

Methods and Results

Sprague-Dawley rats were randomly allocated into four groups of normal control (NC), hindlimb ischemia (HI), hindlimb ischemia with denervation (HID) and hindlimb simple denervation (HD). Hindlimb ischemic recovery was assessed by clinical assessment and tibialis anterior muscle remodeling on day 28 post-surgery. Blood flow was determined by laser Doppler imaging on day 0, 3, 7, 14 and 28 post-surgery. Collateral number of hindlimb was observed by angiography and gracilis muscles were tested by immunostaining on day 7 and 28 post-surgery. Angiogenesis was accessed by counting CD31 positive capillaries in tibialis anterior muscles on day 28 post-surgery. Group HID showed impaired ischemic recovery compared with the other 3 groups and impaired blood flow recovery compared with group HI on day 28 post-surgery. The collateral number and capillary density of group HID were lower than group HI. The collateral diameter of both group HID and group HI significantly increased compared with group NC. However, the lumen diameter was much narrower and the vessel wall was much thicker in group HID than group HI. We also demonstrated that the thickened neointima of collaterals in group HID comprised of smooth muscle cells and endothelial cells.

Conclusions

Denervation of the ligated femoral artery in the hindlimb impairs ischemic recovery via impaired perfusion. The possible mechanisms of impaired perfusion are lower collateral number, lower capillary density and most likely narrower lumen, which damage ischemic recovery. This study illustrates the crucial role of peripheral nerves in arteriogenesis using a model combined ischemia with denervation in hindlimb.

Role of Growth Factors in Modulation of the Microvasculature in Adult Skeletal Muscle

Post-natal skeletal muscle is a highly plastic tissue that has the capacity to regenerate rapidly following injury, and to undergo significant modification in tissue mass (i.e. atrophy/hypertrophy) in response to global metabolic changes. These processes are reliant largely on soluble factors that directly modulate muscle regeneration and mass. However, skeletal muscle function also depends on an adequate blood supply. Thus muscle regeneration and changes in muscle mass, particularly hypertrophy, also demand rapid changes in the microvasculature. Recent evidence clearly demonstrates a critical role for soluble growth factors in the tight regulation of angiogenic expansion of the muscle microvasculature. Furthermore, exogenous modulation of these factors has the capacity to impact directly on angiogenesis and thus, indirectly, on muscle regeneration, growth and performance. This chapter reviews recent developments in understanding the role of growth factors in modulating the skeletal muscle microvasculature, and the potential therapeutic applications of exogenous angiogenic and anti-angiogenic mediators in promoting effective growth and regeneration, and ameliorating certain diseases, of skeletal muscle.

Extracellular vesicles as therapeutic tools in cardiovascular diseases

Extracellular vesicles (EVs), including microvesicles (MVs) and exosomes, are small vesicles secreted from a wide variety of cells. Whereas MVs are particles released by the outward budding of the plasma membrane, exosomes are derived from endocytic compartments. Secretion of EVs can be enhanced by specific stimuli, and increased plasma circulating levels of EVs have been correlated with pathophysiological situations. MVs, already present in the blood of healthy individuals, are considerably elevated in several cardiovascular diseases associated with inflammation, suggesting that they can mediate deleterious effects such as endothelial dysfunction or thrombosis. Nonetheless, very recent studies also demonstrate that MVs may act as biological information vectors transferring proteins or genetic material to maintain cell homeostasis, favor cell repair, or even promote angiogenesis. Additionally, exosomes have also been shown to have pro-angiogenic and cardio-protective properties. These beneficial effects, therefore, reveal the potential therapeutical use of EVs in the field of cardiovascular medicine and regenerative therapy. In this review, we will provide an update of cellular processes modulated by EVs of specific interest in the treatment of cardiovascular pathologies. A special focus will be made on the morphogen sonic hedgehog (Shh) associated with EVs (EVs^Shh+), which have been shown to mediate many pro-angiogenic effects. In addition to offer a potential source of cardiovascular markers, therapeutical potential of EVs reveal exciting opportunities to deliver specific agents by non-immunogenic means to cardiovascular system.

Sonic hedgehog mediates a novel pathway of PDGF-BB-dependent vessel maturation

Recruitment of mural cells (MCs), namely pericytes and smooth muscle cells (SMCs), is essential to improve the maturation of newly formed vessels. Sonic hedgehog (Shh) has been suggested to promote the formation of larger and more muscularized vessels, but the underlying mechanisms of this process have not yet been elucidated. We first identified Shh as a target of platelet-derived growth factor BB (PDGF-BB) and found that SMCs respond to Shh by upregulating extracellular signal-regulated kinase 1/2 and Akt phosphorylation. We next showed that PDGF-BB-induced SMC migration was reduced after inhibition of Shh or its signaling pathway. Moreover, we found that PDGF-BB-induced SMC migration involves Shh-mediated motility. In vivo, in the mouse model of corneal angiogenesis, Shh is expressed by MCs of newly formed blood vessels. PDGF-BB inhibition reduced Shh expression, demonstrating that Shh is a target of PDGF-BB, confirming in vitro experiments. Finally, we found that in vivo inhibition of either PDGF-BB or Shh signaling reduces NG2(+) MC recruitment into neovessels and subsequently reduces neovessel life span. Our findings demonstrate, for the first time, that Shh is involved in PDGF-BB-induced SMC migration and recruitment of MCs into neovessels and elucidate the molecular signaling pathway involved in this process.