Fibroblast growth factor 9 delivery during angiogenesis produces durable, vasoresponsive microvessels wrapped by smooth muscle cells

Embryo-endometrial interaction associated with the location of the embryo during the mobility phase in mares

Embryo-maternal crosstalk is essential to establish pregnancy, with the equine embryo moving throughout the uterus on days 9-15 (ovulation = day 0) as part of this interaction. We hypothesized that the presence of a mobile embryo induces local changes in the gene expression of the endometrium. On Day 12, the endometrial transcripts were compared among three groups: uterine horn with an embryo (P+, n = 7), without an embryo (P-, n = 7) in pregnant mares, and both uterine horns of nonbred mares (NB, n = 6). We identified 1,101 differentially expressed genes (DEGs) between P+ vs. NB and 1,229 DEGs between P- vs. NB. The genes upregulated in both P+ and P- relative to NB were involved in growth factor pathway and fatty acid activation, while downregulated genes were associated with oxytocin signaling pathway and estrogen receptor signaling. Comparing the transcriptome of P+ to that of P-, we found 59 DEGs, of which 30 genes had a higher expression in P+. These genes are associated with regulating vascular growth factors and the immune system, all known to be essential in early pregnancy. Overall, this study suggests that the mobile embryo influences the endometrial gene expression locally.

Circulating inflammatory biomarkers and risk of intracranial aneurysm: a Mendelian randomization study

BACKGROUND

Intracranial aneurysm (IA) accounts for a substantial source of non-traumatic subarachnoid hemorrhage, with inflammation postulated as a potential factor in its pathogenesis. The present study aims at evaluating the association between circulating inflammatory cytokines and risk of IA under a bidirectional two-sample Mendelian randomization (MR) design.

METHODS

For primary analysis, summary statistics of inflammatory regulators was obtained from a genome-wide association study (GWAS) comprising 8293 Finnish participants. Summary data of IA were extracted from a GWAS which comprised 7495 cases and 71,934 controls in European descent. For targeted analysis, summary statistics were extracted from two proteomic studies, which recruit 3301 and 5368 European participants, respectively. Summary data of IA were acquired from FinnGen study with 5342 cases and 342,673 controls. We employed inverse variance weighted (IVW) method as main approach, with sensitivity analyses using weighted median, MR-Egger, and MR-PRESSO methods. Reverse MR analyses were conducted to minimize bias from reverse causality.

RESULTS

No causation of cytokines with IA subtypes was identified in both primary and targeted analysis after Bonferroni correction. In primary analysis, vascular endothelial growth factor (VEGF) and fibroblast growth factor basic (bFGF) levels were suggestively associated with aneurysmal subarachnoid hemorrhage (aSAH) [VEGF → aSAH: OR = 1.15, 95%CI  1.04-1.26, P = 0.005; bFGF → aSAH: OR = 0.62, 95% CI 0.42-0.92, P = 0.02]. Statistical significance failed to replicate in targeted analysis. Instead, suggestive protective effects for aSAH were identified in FGF-9 (FGF-9 → aSAH: OR = 0.74, 95% CI 0.62-0.89, P = 0.001) and FGF-16 (FGF-16 → aSAH: OR = 0.84, 95% CI 0.72-0.97, P = 0.017). Furthermore, reverse analyses identified suggestive effect of unruptured IA on RANTES, MIF, GRO-alpha, FGF-16, and FGF-19. Result remained robust after applying sensitivity tests.

CONCLUSIONS

No causality of inflammatory biomarkers on the risk of IA subtypes was identified. Future large-scale studies are in need to evaluate the temporal dynamics of cytokines in conjunction with IA.

Vutiglabridin exerts anti-ageing effects in aged mice through alleviating age-related metabolic dysfunctions

BACKGROUND

Ageing alters the ECM, leading to mitochondrial dysfunction and oxidative stress, which triggers an inflammatory response that exacerbates with age. Age-related changes impact satellite cells, affecting muscle regeneration, and the balance of proteins. Furthermore, ageing causes a decline in NAD+ levels, and alterations in fat metabolism that impact our health. These various metabolic issues become intricately intertwined with ageing, leading to a variety of individual-level diseases and profoundly affecting individuals' healthspan. Therefore, we hypothesize that vutiglabridin capable of alleviating these metabolic abnormalities will be able to ameliorate many of the problems associated with ageing.

METHOD

The efficacy of vutiglabridin, which alleviates metabolic issues by enhancing mitochondrial function, was assessed in aged mice treated with vutiglabridin and compared to untreated elderly mice. On young mice, vutiglabridin-treated aged mice, and non-treated aged mice, the Senescence-associated beta-galactosidase staining and q-PCR for ageing marker genes were carried out. Bulk RNA-seq was carried out on GA muscle, eWAT, and liver from each group of mice to compare differences in gene expression in various gene pathways. Blood from each group of mice was used to compare and analyze the ageing lipid profile.

RESULTS

SA-β-gal staining of eWAT, liver, kidney, and spleen of ageing mice showed that vutiglabridin had anti-ageing effects compared to the control group, and q-PCR of ageing marker genes including Cdkn1a and Cdkn2a in each tissue showed that vutiglabridin reduced the ageing process. In aged mice treated with vutiglabridin, GA muscle showed improved homeostasis compared to controls, eWAT showed restored insulin sensitivity and prevented FALC-induced inflammation, and liver showed reduced inflammation levels due to prevented TLO formation, improved mitochondrial complex I assembly, resulting in reduced ROS formation. Furthermore, blood lipid analysis revealed that ageing-related lipid profile was relieved in ageing mice treated with vutiglabridin versus the control group.

CONCLUSION

Vutiglabridin slows metabolic ageing mechanisms such as decreased insulin sensitivity, increased inflammation, and altered NAD+ metabolism in adipose tissue in mice experiments, while also retaining muscle homeostasis, which is deteriorated with age. It also improves the lipid profile in the blood and restores mitochondrial function in the liver to reduce ROS generation.

Clearance of Stress-Induced Premature Senescent Cells Alleviates the Formation of Abdominal Aortic Aneurysms

Abdominal aortic aneurysm (AAA) is a multifactorial disease characterized by various pathophysiological processes, including chronic inflammation, oxidative stress, and proteolytic activity in the aortic wall. Stress-induced premature senescence (SIPS) has been implicated in regulating these pathophysiological processes, but whether SIPS contributes to AAA formation remains unknown. Here, we detected SIPS in AAA from patients and young mice. The senolytic agent ABT263 prevented AAA development by inhibiting SIPS. Additionally, SIPS promoted the transformation of vascular smooth muscle cells (VSMCs) from a contractile phenotype to a synthetic phenotype, whereas inhibition of SIPS by the senolytic drug ABT263 suppressed VSMC phenotypic switching. RNA sequencing and single-cell RNA sequencing analysis revealed that fibroblast growth factor 9 (FGF9), secreted by stress-induced premature senescent VSMCs, was a key regulator of VSMC phenotypic switching and that FGF9 knockdown abolished this effect. We further showed that the FGF9 level was critical for the activation of PDGFRβ/ERK1/2 signaling, facilitating VSMC phenotypic change. Taken together, our findings demonstrated that SIPS is critical for VSMC phenotypic switching through the activation of FGF9/PDGFRβ/ERK1/2 signaling, promoting AAA development and progression. Thus, targeting SIPS with the senolytic agent ABT263 may be a valuable therapeutic strategy for the prevention or treatment of AAA.

Depolymerizing self-immolative polymeric lanthanide chelates for vascular imaging

Medical imaging is widely used clinically and in research to understand disease progression and monitor responses to therapies. Vascular imaging enables the study of vascular disease and therapy, but exogenous contrast agents are generally needed to distinguish the vasculature from surrounding soft tissues. Lanthanide-based agents are commonly employed in MRI, but are also of growing interest for micro-CT, as the position of their k-edges allows them to provide enhanced contrast and also to be employed in dual-energy micro-CT, a technique that can distinguish contrast-enhanced blood vessels from tissues such as bone. Small molecule Gd3+ chelates are available, but are excreted too rapidly. At the same time, a lack of rapid clearance from the body for long-circulating agents presents toxicity concerns. To address these challenges, we describe here the use of self-immolative polymers for the development of new degradable chelates that depolymerize completely from end-to-end following the cleavage of a single end-cap from the polymer terminus. We demonstrate that tuning the end-cap allows the rate of depolymerization to be controlled, while tuning the polymer length enables the polymer to exhibit long circulation times in the blood of mice. After successfully providing one hour of blood contrast, depolymerization led to excretion of the resulting small molecule chelates into the bladder. Despite the high doses required for micro-CT, the agents were well tolerated in mice. Thus, these self-immolative polymeric chelates provide a new platform for the development of medical imaging contrast agents. STATEMENT OF SIGNIFICANCE: Vascular imaging is used clinically to diagnose and monitor vascular disease and in research to understand the progression of disease and study responses to new therapies. For techniques such as magnetic resonance imaging and x-ray computed tomography (CT), long circulating contrast agents are needed to differentiate the vasculature from surrounding tissues. However, if these agents are not rapidly excreted from the body, they can lead to toxicity. We present here a new polymeric system that can chelate hundreds of lanthanide ions for imaging contrast and can circulate for one hour in the blood, but then after end-cap cleavage breaks down completely into small molecules for excretion. The successful application of this system in micro-CT in mice is demonstrated.

The fundamentals of fibroblast growth factor 9

Fibroblast growth factor 9 (FGF9) was first identified during a screen for factors acting on cells of the central nervous system (CNS). Research over the subsequent two decades has revealed this protein to be a critically important and elegantly regulated growth factor. A hallmark control feature is reciprocal compartmentalization, particularly during development, with epithelium as a dominant source and mesenchyme a prime target. This mesenchyme selectivity is accomplished by the high affinity of FGF9 to the IIIc isoforms of FGFR1, 2, and 3. FGF9 is expressed widely in the embryo, including the developing heart and lungs, and more selectively in the adult, including the CNS and kidneys. Global Fgf9-null mice die shortly after birth due to respiratory failure from hypoplastic lungs. As well, their hearts are dilated and poorly vascularized, the skeleton is small, the intestine is shortened, and male-to-female sex reversal can be found. Conditional Fgf9-null mice have revealed CNS phenotypes, including ataxia and epilepsy. In humans, FGF9 variants have been found to underlie multiple synostoses syndrome 3, a syndrome characterized by multiple joint fusions. Aberrant FGF9 signaling has also been implicated in differences of sex development and cancer, whereas vascular stabilizing effects of FGF9 could benefit chronic diseases. This primer reviews the attributes of this vital growth factor.

Umbilical cord blood exosomes from very preterm infants with bronchopulmonary dysplasia aggravate lung injury in mice

Bronchopulmonary dysplasia (BPD) is characterized by abnormal development of the blood vessels and alveoli in lungs, which largely occurs in premature infants. Exosomes (EXO) from very preterm infants (VPI) with BPD (BPD-EXO) impair angiogenic activities of human umbilical vein endothelial cells (HUVECs) via EXO-miRNAs cargo. This study aimed to determine whether and how BPD-EXO affect the development of BPD in a mouse model. We showed that treating BPD mice with BPD-EXO chronically and irreversibly aggravated lung injury. BPD-EXO up-regulated 139 and down-regulated 735 genes in the mouse lung tissue. These differentially expressed genes were enriched to the MAPK pathway (e.g., Fgf9 and Cacna2d3), which is critical to angiogenesis and vascular remodeling. BPD-EXO suppressed expression of Fgf9 and Cacna2d3 in HUVECs and inhibited migration, tube formation, and increased cell apoptosis in HUVECs. These data demonstrate that BPD-EXO aggravate lung injury in BPD mice and impair lung angiogenesis, plausibly leading to adverse outcomes of VPI with BPD. These data also suggest that BPD-EXO could serve as promising targets for predicting and treating BPD.

Cell-Free Therapies: The Use of Cell Extracts to Mitigate Irradiation-Injured Salivary Glands

Radiotherapy is a standard treatment for head and neck cancer patients worldwide. However, millions of patients who received radiotherapy consequently suffer from xerostomia because of irreversible damage to salivary glands (SGs) caused by irradiation (IR). Current treatments for IR-induced SG hypofunction only provide temporary symptom alleviation but do not repair the damaged SG, thus resulting in limited treatment efficacy. Therefore, there has recently been a growing interest in regenerative treatments, such as cell-free therapies. This review aims to summarize cell-free therapies for IR-induced SG, with a particular emphasis on utilizing diverse cell extract (CE) administrations. Cell extract is a group of heterogeneous mixtures containing multifunctional inter-cellular molecules. This review discusses the current knowledge of CE's components and efficacy. We propose optimal approaches to improve cell extract treatment from multiple perspectives (e.g., delivery routes, preparation methods, and other details regarding CE administration). In addition, the advantages and limitations of CE treatment are systematically discussed by comparing it to other cell-free (such as conditioned media and exosomes) and cell-based therapies. Although a comprehensive identification of the bioactive factors within CEs and their mechanisms of action have yet to be fully understood, we propose cell extract therapy as an effective, practical, user-friendly, and safe option to conventional therapies in IR-induced SG.

A Comparative Analysis of the Wound Healing-Related Heterogeneity of Adipose-Derived Stem Cells Donors

Adipose-derived Stem cells (ASCs) are on the verge of being available for large clinical trials in wound healing. However, for developing advanced therapy medicinal products (ATMPs), potency assays mimicking the mode of action are required to control the product consistency of the cells. Thus, greater effort should go into the design of product assays. Therefore, we analyzed three ASC-based ATMPs from three different donors with respect to their surface markers, tri-lineage differentiation, proliferation, colony-forming unit capacity, and effect on fibroblast proliferation and migration, endothelial proliferation, migration, and angiogenesis. Furthermore, the transcriptome of all three cell products was analyzed through RNA-sequencing. Even though all products met the criteria by the International Society for Cell and Gene Therapy and the International Federation for Adipose Therapeutics and Science, we found one product to be consistently superior to others when exploring their potency in the wound healing specific assays. Our results indicate that certain regulatory genes associated with extracellular matrix and angiogenesis could be used as markers of a superior ASC donor from which to use ASCs to treat chronic wounds. Having a panel of assays capable of predicting the potency of the product would ensure the patient receives the most potent product for a specific indication, which is paramount for successful patient treatment and acceptance from the healthcare system.

Sulfonated Thermoresponsive Injectable Gel for Sequential Release of Therapeutic Proteins to Protect Cardiac Function after Myocardial Infarction

Myocardial infarction causes cardiomyocyte death and persistent inflammatory responses, which generate adverse pathological remodeling. Delivering therapeutic proteins from injectable materials in a controlled-release manner may present an effective biomedical approach for treating this disease. A thermoresponsive injectable gel composed of chitosan, conjugated with poly(N-isopropylacrylamide) and sulfonate groups, was developed for spatiotemporal protein delivery to protect cardiac function after myocardial infarction. The thermoresponsive gel delivered vascular endothelial growth factor (VEGF), interleukin-10 (IL-10), and platelet-derived growth factor (PDGF) in a sequential and sustained manner in vitro. An acute myocardial infarction mouse model was used to evaluate polymer biocompatibility and to determine therapeutic effects from the delivery system on cardiac function. Immunohistochemistry showed biocompatibility of the hydrogel, while the controlled delivery of the proteins reduced macrophage infiltration and increased vascularization. Echocardiography showed an improvement in ejection fraction and fractional shortening after injecting the thermal gel and proteins. A factorial design of experimental study was implemented to optimize the delivery system for the best combination and doses of proteins for further increasing stable vascularization and reducing inflammation using a subcutaneous injection mouse model. The results showed that VEGF, IL-10, and FGF-2 demonstrated significant contributions toward promoting long-term vascularization, while PDGF's effect was minimal.

Low-flow intussusception and metastable VEGFR2 signaling launch angiogenesis in ischemic muscle

Efforts to promote sprouting angiogenesis in skeletal muscles of individuals with peripheral artery disease have not been clinically successful. We discovered that, contrary to the prevailing view, angiogenesis following ischemic muscle injury in mice was not driven by endothelial sprouting. Instead, real-time imaging revealed the emergence of wide-caliber, primordial conduits with ultralow flow that rapidly transformed into a hierarchical neocirculation by transluminal bridging and intussusception. This process was accelerated by inhibiting vascular endothelial growth factor receptor-2 (VEGFR2). We probed this response by developing the first live-cell model of transluminal endothelial bridging using microfluidics. Endothelial cells subjected to ultralow shear stress could reposition inside the flowing lumen as pillars. Moreover, the low-flow lumen proved to be a privileged location for endothelial cells with reduced VEGFR2 signaling capacity, as VEGFR2 mechanosignals were boosted. These findings redefine regenerative angiogenesis in muscle as an intussusceptive process and uncover a basis for its launch.

Human Induced Pluripotent Stem Cell-Derived Vascular Cells: Recent Progress and Future Directions

Human induced pluripotent stem cells (hiPSCs) hold great promise for cardiovascular regeneration following ischemic injury. Considerable effort has been made toward the development and optimization of methods to differentiate hiPSCs into vascular cells, such as endothelial and smooth muscle cells (ECs and SMCs). In particular, hiPSC-derived ECs have shown robust potential for promoting neovascularization in animal models of cardiovascular diseases, potentially achieving significant and sustained therapeutic benefits. However, the use of hiPSC-derived SMCs that possess high therapeutic relevance is a relatively new area of investigation, still in the earlier investigational stages. In this review, we first discuss different methodologies to derive vascular cells from hiPSCs with a particular emphasis on the role of key developmental signals. Furthermore, we propose a standardized framework for assessing and defining the EC and SMC identity that might be suitable for inducing tissue repair and regeneration. We then highlight the regenerative effects of hiPSC-derived vascular cells on animal models of myocardial infarction and hindlimb ischemia. Finally, we address several obstacles that need to be overcome to fully implement the use of hiPSC-derived vascular cells for clinical application.

Therapeutic angiogenesis in coronary artery disease: a review of mechanisms and current approaches

INTRODUCTION

Despite tremendous advances, the shortcomings of current therapies for coronary disease are evidenced by the fact that it remains the leading cause of death in many parts of the world. There is hence a drive to develop novel therapies to tackle this disease. Therapeutic approaches to coronary angiogenesis have long been an area of interest in lieu of its incredible, albeit unrealized potential.

AREAS COVERED

This paper offers an overview of mechanisms of native angiogenesis and a description of angiogenic growth factors. It progresses to outline the advances in gene and stem cell therapy and provides a brief description of other investigational approaches to promote angiogenesis. Finally, the hurdles and limitations unique to this particular area of study are discussed.

EXPERT OPINION

An effective, sustained, and safe therapeutic option for angiogenesis truly could be the paradigm shift for cardiovascular medicine. Unfortunately, clinically meaningful therapeutic options remain elusive because promising animal studies have not been replicated in human trials. The sheer complexity of this process means that numerous major hurdles remain before therapeutic angiogenesis truly makes its way from the bench to the bedside.

Pathophysiological Aspects of the Development of Abdominal Aortic Aneurysm with a Special Focus on Mitochondrial Dysfunction and Genetic Associations

Abdominal aortic aneurysm (AAA) is a complex degenerative vascular disease, with considerable morbidity and mortality rates among the elderly population. The mortality of AAA is related to aneurysm expansion (the enlargement of the aortic diameter up to 30 mm and above) and the subsequent rupture. The pathogenesis of AAA involves several biological processes, including aortic mural inflammation, oxidative stress, vascular smooth muscle cell apoptosis, elastin depletion, and degradation of the extracellular matrix. Mitochondrial dysfunction was also found to be associated with AAA formation. The evidence accumulated to date supports a close relationship between environmental and genetic factors in AAA initiation and progression. However, a comprehensive pathophysiological understanding of AAA formation remains incomplete. The open surgical repair of AAA is the only therapeutic option currently available, while a specific pharmacotherapy is still awaited. Therefore, there is a great need to clarify pathophysiological cellular and molecular mechanisms underlying AAA formation that would help to develop effective pharmacological therapies. In this review, pathophysiological aspects of AAA development with a special focus on mitochondrial dysfunction and genetic associations were discussed.

Regenerated Microvascular Networks in Ischemic Skeletal Muscle

Skeletal muscle is the largest organ in humans. The viability and performance of this metabolically demanding organ are exquisitely dependent on the integrity of its microcirculation. The architectural and functional attributes of the skeletal muscle microvasculature are acquired during embryonic and early postnatal development. However, peripheral vascular disease in the adult can damage the distal microvasculature, together with damaging the skeletal myofibers. Importantly, adult skeletal muscle has the capacity to regenerate. Understanding the extent to which the microvascular network also reforms, and acquires structural and functional competence, will thus be critical to regenerative medicine efforts for those with peripheral artery disease (PAD). Herein, we discuss recent advances in studying the regenerating microvasculature in the mouse hindlimb following severe ischemic injury. We highlight new insights arising from real-time imaging of the microcirculation. This includes identifying otherwise hidden flaws in both network microarchitecture and function, deficiencies that could underlie the progressive nature of PAD and its refractoriness to therapy. Recognizing and overcoming these vulnerabilities in regenerative angiogenesis will be important for advancing treatment options for PAD.

Human endometrium-derived stem cell improves cardiac function after myocardial ischemic injury by enhancing angiogenesis and myocardial metabolism

BACKGROUND

The human endometrium in premenopausal women is an active site of physiological angiogenesis, with regenerative cells present, suggesting that the endometrium contains adult angiogenic stem cells. In the context of cardiac repair after ischemic injury, angiogenesis is a crucial process to rescue cardiomyocytes. We therefore investigated whether human endometrium-derived stem cells (hEMSCs) can be used for cardiac repair after ischemic injury and their possible underlying mechanisms.

METHODS

Comparisons were made between hEMSCs successfully isolated from 22 premenopausal women and human bone marrow mesenchymal stem cells (hBMSCs) derived from 25 age-matched patients. Cell proliferation, migration, differentiation, and angiogenesis were evaluated through in vitro experiments, while the ability of hEMSCs to restore cardiac function was examined by in vivo cell transplantation into the infarcted nude rat hearts.

RESULTS

In vitro data showed that hEMSCs had greater proliferative and migratory capacities, whereas hBMSCs had better adipogenic differentiation ability. Human umbilical cord vein endothelial cells, treated with conditioned medium from hEMSCs, had significantly higher tube formation than that from hBMSCs or control medium, indicating greater angiogenic potentials for hEMSCs. In vivo, hEMSC transplantation preserved cardiac function, decreased infarct size, and improved tissue repair post-injury. Cardiac metabolism, assessed by ¹⁸F-FDG uptake, showed that ¹⁸F-FDG uptake at the infarction area was significantly higher in both hBMSC and hEMSC groups, compared to the PBS control group, with hEMSCs having the highest uptake, suggesting hEMSC treatment improves cardiomyocyte metabolism and survival after injury. Mechanistic assessment of the angiogenic potential for hEMSCS revealed that angiogenesis-related factors angiopoietin 2, Fms-like tyrosine kinase 1, and FGF9 were significantly upregulated in hEMSC-implanted infarcted hearts, compared to the PBS control group.

CONCLUSION

hEMSCs, compared to hBMSCs, have greater capacity to induce angiogenesis, and improved cardiac function after ischemic injury.

Mixing Cells for Vascularized Kidney Regeneration

The worldwide rise in prevalence of chronic kidney disease (CKD) demands innovative bio-medical solutions for millions of kidney patients. Kidney regenerative medicine aims to replenish tissue which is lost due to a common pathological pathway of fibrosis/inflammation and rejuvenate remaining tissue to maintain sufficient kidney function. To this end, cellular therapy strategies devised so far utilize kidney tissue-forming cells (KTFCs) from various cell sources, fetal, adult, and pluripotent stem-cells (PSCs). However, to increase engraftment and potency of the transplanted cells in a harsh hypoxic diseased environment, it is of importance to co-transplant KTFCs with vessel forming cells (VFCs). VFCs, consisting of endothelial cells (ECs) and mesenchymal stem-cells (MSCs), synergize to generate stable blood vessels, facilitating the vascularization of self-organizing KTFCs into renovascular units. In this paper, we review the different sources of KTFCs and VFCs which can be mixed, and report recent advances made in the field of kidney regeneration with emphasis on generation of vascularized kidney tissue by cell transplantation.

Anti-Cancer Effect of Cordycepin on FGF9-Induced Testicular Tumorigenesis

Cordycepin, a bioactive constituent from the fungus Cordyceps sinensis, could inhibit cancer cell proliferation and promote cell death via induction of cell cycle arrest, apoptosis and autophagy. Our novel finding from microarray analysis of cordycepin-treated MA-10 mouse Leydig tumor cells is that cordycepin down-regulated the mRNA levels of FGF9, FGF18, FGFR2 and FGFR3 genes in MA-10 cells. Meanwhile, the IPA-MAP pathway prediction result showed that cordycepin inhibited MA-10 cell proliferation by suppressing FGFs/FGFRs pathways. The in vitro study further revealed that cordycepin decreased FGF9-induced MA-10 cell proliferation by inhibiting the expressions of p-ERK1/2, p-Rb and E2F1, and subsequently reducing the expressions of cyclins and CDKs. In addition, a mouse allograft model was performed by intratumoral injection of FGF9 and/or intraperitoneal injection of cordycepin to MA-10-tumor bearing C57BL/6J mice. Results showed that FGF9-induced tumor growth in cordycepin-treated mice was significantly smaller than that in a PBS-treated control group. Furthermore, cordycepin decreased FGF9-induced FGFR1-4 protein expressions in vitro and in vivo. In summary, cordycepin inhibited FGF9-induced testicular tumor growth by suppressing the ERK1/2, Rb/E2F1, cell cycle pathways, and the expressions of FGFR1-4 proteins, suggesting that cordycepin can be used as a novel anticancer drug for testicular cancers.

Interaction of FGF9 with FGFR3-IIIb/IIIc, a putative driver of growth and aggressive behaviour of hepatocellular carcinoma

BACKGROUND & AIMS

Recently, overexpression of the fibroblast growth factor receptor 3 (FGFR3) splice variants FGFR3-IIIb and FGFR3-IIIc was found in ~50% of hepatocellular carcinoma (HCC). Here, we aim to identify FGFR3-IIIb/IIIc ligands, which drive the progression of HCC.

METHODS

FACS, MTT assay and/or growth curves served to identify the FGFR3-IIIb/IIIc ligand being most effective to induce growth of hepatoma/hepatocarcinoma cell lines, established from human HCC. The most potent FGF was characterized regarding the expression levels in epithelial and stromal cells of liver and HCC and impact on neoangiogenesis, clonogenicity and invasive growth of hepatoma/hepatocarcinoma cells.

RESULTS

Among all FGFR3-IIIb/IIIc ligands tested, FGF9 was the most potent growth factor for hepatoma/hepatocarcinoma cells. Replication and/or sprouting of blood/lymphendothelial cells was stimulated as well. FGF9 occurred mainly in stromal cells of unaltered liver but in epithelial cells of HCC. Every fifth HCC exhibited overexpressed FGF9 and frequent co-upregulation of FGFR3-IIIb/IIIc. In hepatoma/hepatocarcinoma cells FGF9 enhanced the capability for clonogenicity and disintegration of the blood and lymphatic endothelium, being most pronounced in cells overexpressing FGFR3-IIIb or FGFR3-IIIc, respectively. Any of the FGF9 effects in hepatoma/hepatocarcinoma cells was blocked completely by applying the FGFR1-3-specific tyrosine kinase inhibitor BGJ398 or siFGFR3, while siFGFR1/2/4 were mostly ineffective.

CONCLUSIONS

FGF9 acts via FGFR3-IIIb/IIIc to enhance growth and aggressiveness of HCC cells. Accordingly, blockade of the FGF9-FGFR3-IIIb/IIIc axis may be an efficient therapeutic option for HCC patients.

Systematic Interrogation of Angiogenesis in the Ischemic Mouse Hind Limb: Vulnerabilities and Quality Assurance

Supplemental Digital Content is available in the text.

Objective:

There has been little success in translating preclinical studies of mouse hind limb ischemia into benefit for patients with peripheral artery disease. Using systematic strategies, we sought to define the injury and angiogenesis landscapes in mice subjected to hind limb ischemia and ascertain whether published studies to date have used an analysis strategy concordant with these data.

Approach and Results:

Maps of ischemic injury were generated from 22 different hind limb muscles and 33 muscle territories in 12-week-old C57BL/6 mice, based on loss or centralization of myofiber nuclei. Angiogenesis was similarly mapped based on CD (cluster of differentiation) 31–positive capillary content. Only 10 of 33 muscle territories displayed consistent muscle injury, with the distal anterior hind limb muscles most reliably injured. Angiogenesis was patchy and exclusively associated with zones of regenerated muscle (central nuclei). Angiogenesis was not observed in normal appearing muscle, necrotic muscle, or injury border zones. Systematic review of mouse hind limb angiogenesis studies identified 5147 unique publications, of which 509 met eligibility criteria for analysis. Only 7% of these analyzed manuscripts evaluated angiogenesis in distal anterior hind limb muscles and only 15% consistently examined for angiogenesis in zones of muscle regeneration.

Conclusions:

In 12-week C57BL/6 mice, angiogenesis postfemoral artery excision proceeds exclusively in zones of muscle regeneration. Only a minority of studies to date have analyzed angiogenesis in regions of demonstrably regenerating muscle or in high-likelihood territories. Quality assurance standards, informed by the atlas and mapping data herein, could augment data reliability and potentially help translate mouse hind limb ischemia studies to patient care.

Transcriptomic Analysis of Human Mesenchymal Stem Cell Therapy in Incontinent Rat Injured Urethra

Periurethral human mesenchymal stem cell (hMSC) injections are associated with functional improvement in animal models of postpartum stress urinary incontinence (SUI). However, limited data exist on the role of hMSCs in modulating gene expression in tissue repair after urethral injury. To this end, we quantified temporal gene expression modulation in hMSCs, and in injured rat urethral tissue, using RNA-seq in an animal model of SUI, over a 3-day period following urethral injury, and local hMSC injection. We injected PKH fluorescent-labeled hMSC into the periurethral space of rats following a 4 h vaginal distention (VD) (three rats per time point). Control rats underwent VD injury only, and all animals were euthanized at 12, 24, 36, 72 h postinjury. Rat urethral and vaginal tissues were frozen and sectioned. Fluorescent labeled hMSCs were distinguished from adjacent, unlabeled rat urethral tissue. RNA was prepared from hMSCs and urethral tissue obtained by laser dissection of frozen tissue sections and sequenced on an Illumina HiSeq 2500. Differentially expressed genes (DEGs) over 72 h were evaluated using a two-group t-test (p < 0.05). Our transcriptional analyses identified candidate genes involved in tissue injury that were broadly sorted by injury and exposure to hMSC throughout the first 72 h of acute phase of injury. DEGs in treated urethra, compared with untreated urethra, were functionally associated with tissue repair, angiogenesis, neurogenesis, and oxidative stress suppression. DEGs included a variety of cytokines, extracellular matrix stabilization and regeneration genes, cytokine signaling modification, cell cycle regulation, muscle differentiation, and stabilization. Moreover, our results revealed DEG changes in hMSCs (PKH-labeled) harvested from injured urethra. The expressions are related to DNA damage repair, transcription activation, stem cell regulation, cell survival, apoptosis, self-renewal, cell proliferation, migration, and injury response. Impact statement Stress urinary incontinence (SUI) affects nearly half of women over 40, resulting in reduced quality of life and increased health care cost. Development of SUI is multifactorial and strongly associated with vaginal delivery. While stem cell therapy in animal models of SUI and limited preliminary clinical trials demonstrate functional improvement of SUI, the role of stem cell therapy in modulating tissue repair is unclear impeding advanced clinical trials. Our work provides a new understanding of the transcriptional mechanisms with which human mesenchymal stem cells improve acute injury repair thus guiding the development of cell-based therapies for women with nonacute established SUI.

Obstruction of Small Arterioles in Patients with Critical Limb Ischemia due to Partial Endothelial-to-Mesenchymal Transition

Critical limb ischemia (CLI) is a hazardous manifestation of atherosclerosis and treatment failure is common. Abnormalities in the arterioles might underlie this failure but the cellular pathobiology of microvessels in CLI is poorly understood. We analyzed 349 intramuscular arterioles in lower limb specimens from individuals with and without CLI. Arteriolar densities were 1.8-fold higher in CLI muscles. However, 33% of small (<20 μm) arterioles were stenotic and 9% were completely occluded. The lumens were closed by bulky, re-oriented endothelial cells expressing abundant N-cadherin that uniquely localized between adjacent and opposing endothelial cells. S100A4 and SNAIL1 were also expressed, supporting an endothelial-to-mesenchymal transition. SMAD2/3 was activated in occlusive endothelial cells and TGFβ1 was increased in the adjacent mural cells. These findings identify a microvascular closure process based on mesenchymal transitions in a hyper-TGFß environment that may, in part, explain the limited success of peripheral artery revascularization procedures.

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Small arterioles in patients with critical limb ischemia can be narrowed or closed

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Arteriolar occlusion is due to bulky endothelial cells

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Bulky endothelial cells have partially transitioned to mesenchymal cells

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Occlusive cells interlock laterally and apically via N-cadherin neo-adhesions

Genetic and epigenetic regulation of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are focal dilations of the aorta that develop from degenerative changes in the media and adventitia of the vessel. Ruptured AAAs have a mortality of up to 85%, thus it is important to identify patients with AAA at increased risk for rupture who would benefit from increased surveillance and/or surgical repair. Although the exact genetic and epigenetic mechanisms regulating AAA formation are not completely understood, Mendelian cases of AAA, which result from pathologic variants in a single gene, have helped provide a basic understanding of AAA pathophysiology. More recently, genome wide associated studies (GWAS) have identified additional variants, termed single nucleotide polymorphisms, in humans that may be associated with AAAs. While some variants may be associated with AAAs and play causal roles in aneurysm pathogenesis, it should be emphasized that the majority of SNPs do not actually cause disease. In addition to GWAS, other studies have uncovered epigenetic causes of disease that regulate expression of genes known to be important in AAA pathogenesis. This review describes many of these genetic and epigenetic contributors of AAAs, which altogether provide a deeper insight into AAA pathogenesis.

The Use of Histidine-tryptophan-ketoglutarate Solution as a New Storage Medium for the Avulsed Tooth

INTRODUCTION

Histidine-tryptophan-ketoglutarate (HTK) is a preservation solution used for organ transplantation. The physiological pH and osmolality of this solution are known to facilitate cell proliferation and cell membrane stabilization. The purpose of the present study was to investigate the efficacy of several concentrations of HTK solution as a storage medium for avulsed teeth.

METHODS

Cultured human periodontal ligament cells were stored in different concentrations of HTK solutions. After 1, 3, 6, 12, 24, 48, and 72 hours, cell viability was assessed using the Cell-Counting Kit-8 (Dojindo Molecular Technologies, Kumamoto, Japan) and LIVE/DEAD (Invitrogen, Carlsbad, CA) assay. Cell response of the most effective concentrations of HTK solution were further analyzed by gene expression profiling, and their cell viability was compared with other storage media.

RESULTS

The highest cell viability was observed in 50% HTK solution in various concentrations of HTK solution (P < .05). In periodontal ligament cells stored in 50% HTK solution for 3 hours, the expression of genes related to angiogenesis, the inflammatory response, and cell proliferation was increased compared with the control. Compared with other storage media, the highest cell viability was observed in 50% HTK solution.

CONCLUSIONS

Our study suggests that 50% HTK solution containing cell culture medium represents a suitable storage medium for avulsed teeth.

Cell type-specific endometrial transcriptome changes during initial recognition of pregnancy in the mare

Previous endometrial gene expression studies during the time of conceptus migration did not provide final conclusions on the mechanisms of maternal recognition of pregnancy (MRP) in the mare. This called for a cell type-specific endometrial gene expression analysis in response to embryo signals to improve the understanding of gene expression regulation in the context of MRP. Laser capture microdissection was used to collect luminal epithelium (LE), glandular epithelium and stroma from endometrial biopsies from Day 12 of pregnancy and Day 12 of the oestrous cycle. RNA sequencing (RNA-Seq) showed greater expression differences between cell types than between pregnant and cyclic states; differences between the pregnant and cyclic states were mainly found in LE. Comparison with a previous RNA-Seq dataset for whole biopsy samples revealed the specific origin of gene expression differences. Furthermore, genes specifically differentially expressed (DE) in one cell type were found that were not detectable as DE in biopsies. Overall, this study revealed spatial information about endometrial gene expression during the phase of initial MRP. The conceptus induced changes in the expression of genes involved in blood vessel development, specific spatial regulation of the immune system, growth factors, regulation of prostaglandin synthesis, transport prostaglandin receptors, specifically prostaglandin F receptor (PTGFR) in the context of prevention of luteolysis.

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.

Tissue Engineering of the Microvasculature

The ability to generate new microvessels in desired numbers and at desired locations has been a long-sought goal in vascular medicine, engineering, and biology. Historically, the need to revascularize ischemic tissues nonsurgically (so-called therapeutic vascularization) served as the main driving force for the development of new methods of vascular growth. More recently, vascularization of engineered tissues and the generation of vascularized microphysiological systems have provided additional targets for these methods, and have required adaptation of therapeutic vascularization to biomaterial scaffolds and to microscale devices. Three complementary strategies have been investigated to engineer microvasculature: angiogenesis (the sprouting of existing vessels), vasculogenesis (the coalescence of adult or progenitor cells into vessels), and microfluidics (the vascularization of scaffolds that possess the open geometry of microvascular networks). Over the past several decades, vascularization techniques have grown tremendously in sophistication, from the crude implantation of arteries into myocardial tunnels by Vineberg in the 1940s, to the current use of micropatterning techniques to control the exact shape and placement of vessels within a scaffold. This review provides a broad historical view of methods to engineer the microvasculature, and offers a common framework for organizing and analyzing the numerous studies in this area of tissue engineering and regenerative medicine. © 2019 American Physiological Society. Compr Physiol 9:1155-1212, 2019.

Synergistic effects of laminin-1 peptides, VEGF and FGF9 on salivary gland regeneration

Hyposalivation is associated with radiation therapy, Sjögren's syndrome and/or aging, and is a significant clinical problem that decreases oral health and overall health in many patients and currently lacks effective treatment. Hence, methods to regenerate salivary glands and restore saliva secretion are urgently needed. To this end, this study describes the modification of fibrin hydrogels with a combination of laminin-1 peptides (YIGSR and A99) and human growth factors (vascular endothelial growth factor and fibroblast growth factor 9) to enhance regeneration in a salivary gland injury mouse model. Our results indicate that these fortified hydrogels enhanced angiogenesis and neurogenesis while promoting formation of acinar structures, thereby leading to enhanced saliva secretion. Such functional recovery indicates salivary gland regeneration and suggests that our technology may be useful in promoting gland regeneration and reversing hyposalivation in a clinical setting. STATEMENT OF SIGNIFICANCE: We engineered Fibrin Hydrogels (FH) to contain multiple regenerative cues including laminin-1 peptides (L_1p) and growth factors (GFs). L_1p and GF modified FH were used to induce salivary gland regeneration in a wounded mouse model. Treatment with L_1p and GF modified FH promoted salivary epithelial tissue regeneration, vascularization, neurogenesis and healing as compared to L_1p-FH or FH alone. Results indicate that L_1p and GF modified FH can be used for future therapeutic applications.

Vitamin D intervention does not improve vascular regeneration in diet-induced obese male mice with peripheral ischemia

Vitamin D appears to either promote or inhibit neovascularization in a disease context-dependent manner. The effects of vitamin D, alone or in combination with niacin, on endothelial cell (EC) angiogenic function and on revascularization in obese animals with peripheral ischemia are unknown. Here, we report that supplementation of high palmitate medium with vitamin D, niacin or both vitamins increased EC tube formation, which relies primarily on cell migration, and also maintained tube stability over time. Transcriptomic analyses revealed that both vitamins increased stress response and anti-inflammatory gene expression. However, vitamin D decreased cell cycle gene expression and inhibited proliferation, while niacin induced stable expression of miR-126-3p and -5p and maintained cell proliferation in high palmitate. To assess vascular regeneration, diet-induced obese mice received vitamin D, niacin or both vitamins following hind limb ischemic injury. Niacin, but not vitamin D or combined treatment, improved recovery of hind limb use. Histology of tibialis anterior sections revealed no improvements in revascularization, regeneration, inflammation or fibrosis with vitamin D or combined treatment. In summary, although both vitamin D and niacin increased angiogenic function of EC cultures in high fat, only niacin improved recovery of hind limb use following ischemic injury in obese mice. It is possible that inhibition of cell proliferation by vitamin D in high-fat conditions limits vascular regeneration and recovery from peripheral ischemia in obesity.

Fortifying Angiogenesis in Ischemic Muscle with FGF9-Loaded Electrospun Poly(Ester Amide) Fibers

Delivery of angiogenic growth factors lessens ischemia in preclinical models but has demonstrated little benefit in patients with peripheral vascular disease. Augmenting the wrapping of nascent microvessels by mural cells constitutes an alternative strategy to regenerating a functional microvasculature, particularly if integrated with a sustained delivery platform. Herein, electrospun poly(ester amide) (PEA) nanofiber mats are fabricated for delivering a mural cell-targeting factor, fibroblast growth factor 9 (FGF9). Proof-of-principle is established by placing FGF9/FGF2-loaded PEA fiber mats on the chick chorioallantoic membrane and identifying enhanced angiogenesis by 3D power Doppler micro-ultrasound imaging. To assess the delivery system in ischemic muscle, FGF9-loaded PEA fiber mats are implanted onto the surface of the tibialis anterior muscle of mice with hindlimb ischemia. The system supplies FGF9 into the tibialis anterior muscle and yields a neo-microvascular network with enhanced mural cell coverage up to 28 days after injury. The regenerating muscle that receives FGF9 display near-normal sized myofibers and reduced interstitial fibrosis. Moreover, the mice demonstrate improved locomotion. These findings of locally released FGF9 from PEA nanofibers raise prospects for a microvascular remodeling approach to improve muscle health in peripheral vascular disease.

Periostin and CCN2 Scaffolds Promote the Wound Healing Response in the Skin of Diabetic Mice

IMPACT STATEMENT

Nonhealing skin wounds remain a significant burden on health care systems, with diabetic patients 20 times as likely to undergo a lower extremity amputation due to impaired healing. Novel treatments that suppress the proinflammatory signature and induce the proliferative and remodeling phases are needed clinically. We demonstrate that the addition of periostin and CCN2 in a scaffold form increases closure rates of full-thickness skin wounds in diabetic mice, concomitant with enhanced angiogenesis. Our results demonstrate the efficacy of periostin- and CCN2-containing biomaterials to stimulate wound closure, which could represent a novel method for the treatment of diabetic skin wounds.

FGF9-induced ovarian cancer cell invasion involves VEGF-A/VEGFR2 augmentation by virtue of ETS1 upregulation and metabolic reprogramming

Ovarian cancer (OC) renders its lethality to enhanced metastasis and late detection. A plethora of growth factors including Vascular Endothelial Growth Factor (VEGF) and Fibroblast Growth Factor (FGF) stimulated signaling pathways regulate the invasive/metastatic behavior of ovarian tumors contributing to its aggressiveness. Autocrine VEGF-functioning by virtue of upregulated VEGFR2 contributes to the invasiveness of OC cells by modulating the MMPs. Studies have highlighted the interaction between FGF and VEGF signaling pathways during angiogenesis. Moreover, the previous involvement of FGF9 in controlling the OC invasiveness prompted us to investigate its role in regulating VEGF-A/VEGFR2 expression that may control the invasive behavior of the cells. Here we demonstrate that, FGF9-induction resulted in the augmentation of VEGF-A/VEGFR2 levels and the subsequent invasion of OC cells through the activation of the ERK-signaling pathway. Moreover, the ETS1 transcription factor was found to enhance the VEGFA/VEGFR2 expression by directly binding to their promoters and facilitated FGF9-dependent elevation of VEGF-signaling which augmented the metastatic potential of OC cells. Enhanced cellular invasiveness was associated with increased aerobic glycolysis, LDH-A expression, and lactate production. Lactate, in turn, controlled VEGF-A/VEGFR2 expression and the resulting cell invasion. Taken together, the augmentation of VEGF-A/VEGFR2 expression and subsequent invasion of OC cells were governed by FGF9-dependent enhancement of both ETS1 and LDH-A/lactate levels. Therefore, this study provides an insight into the mechanism governing elevated VEGF-autocrine functioning in OC that contributes to its invasive/metastatic behavior.

Syndecan-1 in mechanosensing of nanotopological cues in engineered materials

The cells of the vascular system are highly sensitive to biophysical cues from their local cellular microenvironment. To engineer improved materials for vascular devices and delivery of cell therapies, a key challenge is to understand the mechanisms that cells use to sense biophysical cues from their environment. Syndecans are heparan sulfate proteoglycans (HSPGs) that consist of a protein core modified with heparan sulfate glycosaminoglycan chains. Due to their presence on the cell surface and their interaction with cytoskeletal and focal adhesion associated molecules, cell surface proteoglycans are well poised to serve as mechanosensors of the cellular microenvironment. Nanotopological cues have become recognized as major regulators of cell growth, migration and phenotype. We hypothesized that syndecan-1 could serve as a mechanosensor for nanotopological cues and can mediate the responsiveness of vascular smooth muscle cells to nanoengineered materials. We created engineered substrates made of polyurethane acrylate with nanogrooves using ultraviolet-assisted capillary force lithography. We cultured vascular smooth muscle cells with knockout of syndecan-1 on engineered substrates with varying compliance and nanotopology. We found that knockout of syndecan-1 reduced alignment of vascular smooth muscle cells to the nanogrooves under inflammatory treatments. In addition, we found that loss of syndecan-1 increased nuclear localization of Yap/Taz and phospho-Smad2/3 in response to nanogrooves. Syndecan-1 knockout vascular smooth muscle cells also had elevated levels of Rho-associated protein kinase-1 (Rock1), leading to increased cell stiffness and an enhanced contractile state in the cells. Together, our findings support that syndecan-1 knockout leads to alterations in mechanosensing of nanotopographical cues through alterations of in rho-associated signaling pathways, cell mechanics and mediators of the Hippo and TGF-β signaling pathways.

Cardiovascular Risk Factors and Markers

Cardiovascular risk is assessed for the prediction and appropriate management of patients using collections of identified risk markers obtained from clinical questionnaire information, concentrations of certain blood molecules (e.g., N-terminal proB-type natriuretic peptide fragment and soluble receptors of tumor-necrosis factor-α and interleukin-2), imaging data using various modalities, and electrocardiographic variables, in addition to traditional risk factors.

Transplantation of bioengineered rat lungs recellularized with endothelial and adipose-derived stromal cells

Bioengineered lungs consisting of a decellularized lung scaffold that is repopulated with a patient's own cells could provide desperately needed donor organs in the future. This approach has been tested in rats, and has been partially explored in porcine and human lungs. However, existing bioengineered lungs are fragile, in part because of their immature vascular structure. Herein, we report the application of adipose-derived stem/stromal cells (ASCs) for engineering the pulmonary vasculature in a decellularized rat lung scaffold. We found that pre-seeded ASCs differentiated into pericytes and stabilized the endothelial cell (EC) monolayer in nascent pulmonary vessels, thereby contributing to EC survival in the regenerated lungs. The ASC-mediated stabilization of the ECs clearly reduced vascular permeability and suppressed alveolar hemorrhage in an orthotopic transplant model for up to 3 h after extubation. Fibroblast growth factor 9, a mesenchyme-targeting growth factor, enhanced ASC differentiation into pericytes but overstimulated their proliferation, causing a partial obstruction of the vasculature in the regenerated lung. ASCs may therefore provide a promising cell source for vascular regeneration in bioengineered lungs, though additional work is needed to optimize the growth factor or hormone milieu for organ culture.

Four-Dimensional Microvascular Analysis Reveals That Regenerative Angiogenesis in Ischemic Muscle Produces a Flawed Microcirculation

Rationale:

Angiogenesis occurs after ischemic injury to skeletal muscle, and enhancing this response has been a therapeutic goal. However, to appropriately deliver oxygen, a precisely organized and exquisitely responsive microcirculation must form. Whether these network attributes exist in a regenerated microcirculation is unknown, and methodologies for answering this have been lacking.

Objective:

To develop 4-dimensional methodologies for elucidating microarchitecture and function of the reconstructed microcirculation in skeletal muscle.

Methods and Results:

We established a model of complete microcirculatory regeneration after ischemia-induced obliteration in the mouse extensor digitorum longus muscle. Dynamic imaging of red blood cells revealed the regeneration of an extensive network of flowing neo-microvessels, which after 14 days structurally resembled that of uninjured muscle. However, the skeletal muscle remained hypoxic. Red blood cell transit analysis revealed slow and stalled flow in the regenerated capillaries and extensive arteriolar-venular shunting. Furthermore, spatial heterogeneity in capillary red cell transit was highly constrained, and red blood cell oxygen saturation was low and inappropriately variable. These abnormalities persisted to 120 days after injury. To determine whether the regenerated microcirculation could regulate flow, the muscle was subjected to local hypoxia using an oxygen-permeable membrane. Hypoxia promptly increased red cell velocity and flux in control capillaries, but in neocapillaries, the response was blunted. Three-dimensional confocal imaging revealed that neoarterioles were aberrantly covered by smooth muscle cells, with increased interprocess spacing and haphazard actin microfilament bundles.

Conclusions:

Despite robust neovascularization, the microcirculation formed by regenerative angiogenesis in skeletal muscle is profoundly flawed in both structure and function, with no evidence for normalizing over time. This network-level dysfunction must be recognized and overcome to advance regenerative approaches for ischemic disease.

Differentiation of arterioles from venules in mouse histology images using machine learning

Analysis and morphological comparison of the arteriolar and venular components of a microvascular network are essential to our understanding of multiple diseases affecting every organ system. We have developed and evaluated the first fully automatic software system for differentiation of arterioles from venules on high-resolution digital histology images of the mouse hind limb immunostained with smooth muscle [Formula: see text]-actin. Classifiers trained on statistical and morphological features by supervised machine learning provided useful classification accuracy for differentiation of arterioles from venules, achieving an area under the receiver operating characteristic curve of 0.89. Feature selection was consistent across cross validation iterations, and a small set of two features was required to achieve the reported performance, suggesting the generalizability of the system. This system eliminates the need for laborious manual classification of the hundreds of microvessels occurring in a typical sample and paves the way for high-throughput analysis of the arteriolar and venular networks in the mouse.

MicroRNA-182 prevents vascular smooth muscle cell dedifferentiation via FGF9/PDGFRβ signaling

The abnormal phenotypic transformation of vascular smooth muscle cells (SMCs) causes various proliferative vascular diseases. MicroRNAs (miRNAs or miRs) have been established to play important roles in SMC biology and phenotypic modulation. This study revealed that the expression of miR‑182 was markedly altered during rat vascular SMC phenotypic transformation in vitro. We aimed to investigate the role of miR‑182 in the vascular SMC phenotypic switch and to determine the potential molecular mechanisms involved. The expression of miR‑182 gene was significantly downregulated in cultured SMCs during dedifferentiation from a contractile to a synthetic phenotype. Conversely, the upregulation of miR‑182 increased the expression of SMC-specific contractile genes, such as α-smooth muscle actin, smooth muscle 22α and calponin. Additionally, miR‑182 overexpression potently inhibited SMC proliferation and migration under both basal conditions and under platelet-derived growth factor-BB stimulation. Furthermore, we identified fibroblast growth factor 9 (FGF9) as the target gene of miR‑182 for the phenotypic modulation of SMCs mediated through platelet-derived growth factor receptor β (PDGFRβ) signaling. These data suggest that miR‑182 may be a novel SMC phenotypic marker and a modulator that may be used to prevent SMC dedifferentiation via FGF9/PDGFRβ signaling.

Segmentation of digitized histological sections for quantification of the muscularized vasculature in the mouse hind limb

Immunohistochemical tissue staining enhances microvasculature characteristics, including the smooth muscle in the medial layer of the vessel walls that is responsible for regulation of blood flow. The vasculature can be imaged in a comprehensive fashion using whole-slide scanning. However, since each such image potentially contains hundreds of small vessels, manual vessel delineation and quantification is not practically feasible. In this work, we present a fully automatic segmentation and vasculature quantification algorithm for whole-slide images. We evaluated its performance on tissue samples drawn from the hind limbs of wild-type mice, stained for smooth muscle using 3,3'-Diaminobenzidine (DAB) immunostain. The algorithm was designed to be robust to vessel fragmentation due to staining irregularity, and artefactual staining of nonvessel objects. Colour deconvolution was used to isolate the DAB stain for detection of vessel wall fragments. Complete vessels were reconstructed from the fragments by joining endpoints of topological skeletons. Automatic measures of vessel density, perimeter, wall area and local wall thickness were taken. The segmentation algorithm was validated against manual measures, resulting in a Dice similarity coefficient of 89%. The relationships observed between these measures were as expected from a biological standpoint, providing further reinforcement of the accuracy of this system. This system provides a fully automated and accurate means of measuring the arteriolar and venular morphology of vascular smooth muscle.

Emerging drugs and therapeutics for systemic sclerosis

INTRODUCTION

Treatment of systemic sclerosis (SSc) is challenging despite advances in medical therapeutics for other rheumatologic diseases. Significant disease modifying therapy is lacking for most patients with SSc, due to the heterogeneous multisystem nature of SSc and its complex pathophysiology. The emergence of organ based management strategies has provided guidance in patient care as well as research and drug development. Areas covered: Design and development of new compounds focused on the underlying fibrotic disease processes have been sparse. Therefore, organ based strategies with targeted approaches have been directed towards the most devastating and life threatening features of systemic sclerosis. These include pulmonary arterial hypertension, interstitial lung disease, peripheral vasculopathy and skin thickening. In this context, new treatment regimens using older drugs as well as discovery of novel compounds based on recent insights of the disease pathophysiology are discussed. Expert opinion: Systemic sclerosis is a heterogeneous rare disease that carries a high burden of morbidity and mortality. Organ based management strategies have improved the natural history of systemic sclerosis using targeted interventions or strategies, particularly vascular features. However, more research is required to better understand disease mechanisms, including an ultimate unifying pathway that explains the multisystem nature of systemic sclerosis.

Hybrid Biomaterial with Conjugated Growth Factors and Mesenchymal Stem Cells for Ectopic Bone Formation

Bone is a highly vascularized tissue and efficient bone regeneration requires neovascularization, especially for critical-sized bone defects. We developed a novel hybrid biomaterial comprising nanocalcium sulfate (nCS) and fibrin hydrogel to deliver mesenchymal stem cells (MSCs) and angiogenic factors, vascular endothelial growth factor (VEGF) and fibroblast growth factor 9 (FGF9), to promote neovascularization and bone formation. MSC and growth factor(s)-loaded scaffolds were implanted subcutaneously into mice to examine their angiogenic and osteogenic potential. Micro CT, alkaline phosphatase activity assay, and histological analysis were used to evaluate bone formation, while immunohistochemistry was employed to assess neovessel formation. The presence of fibrin preserved the nCS scaffold structure and promoted de novo bone formation. In addition, the presence of bone morphogenic protein 2-expressing MSC in nCS and fibrin hydrogels improved bone regeneration significantly. While FGF9 alone had no significant effect, the combination FGF9 and VEGF conjugated in fibrin enhanced neovascularization and bone formation more than 4-fold compared to nCS with MSC. Overall, our results suggested that the combination of nCS (to support bone formation) with a fibrin-based VEGF/FGF9 release system (support vascular formation) is an innovative and effective strategy that significantly enhanced ectopic bone formation in vivo.

Niacin promotes revascularization and recovery of limb function in diet-induced obese mice with peripheral ischemia

Niacin can reduce vascular disease risk in individuals with metabolic syndrome, but in light of recent large randomized controlled trials outcomes, its biological actions and clinical utility remain controversial. Niacin can improve endothelial function, vascular inflammation, and vascular regeneration, independent of correcting dyslipidemia, in various lean rodent models of vascular injury. Here, we tested whether niacin could directly improve endothelial cell angiogenic function during combined exposure to excess fatty acids and hypoxia, and whether intervention with niacin during continued feeding of western diet could improve revascularization and functional recovery in obese, hyperlipidemic mice with peripheral ischemia. Treatment with niacin (10 μmol/L) increased human microvascular endothelial cell angiogenic function during exposure to high fatty acids and hypoxia (2% oxygen), as determined by tube formation on Matrigel. To assess revascularization in vivo, we used western diet-induced obese mice with unilateral hind limb femoral artery ligation and excision. Treatment for 14 days postinjury with once daily i.p. injections of a low dose of niacin (50 mg/kg) improved recovery of hind limb use, in association with enhanced revascularization and decreased inflammation of the tibialis anterior muscle. These effects were concomitant with decreased plasma triglycerides, but not increased plasma apoAI. Thus, niacin improves endothelial tube formation under lipotoxic and hypoxic conditions, and moreover, promotes revascularization and functional hind limb recovery following ischemic injury in diet-induced obese mice with hyperlipidemia. These data may have implications for niacin therapy in the treatment of peripheral ischemic vascular disease associated with metabolic syndrome.

Concurrent and Sustained Delivery of FGF2 and FGF9 from Electrospun Poly(ester amide) Fibrous Mats for Therapeutic Angiogenesis

Therapeutic angiogenesis has emerged as a potential strategy to treat ischemic vascular diseases. However, systemic or local administration of growth factors is usually inefficient for maintaining the effective concentration at the site of interest due to their rapid clearance or degradation. In this study, we report a differential and sustained release of an angiogenic factor, fibroblast growth factor-2 (FGF2), and an arteriogenic factor, fibroblast growth factor-9 (FGF9), from α-amino acid-derived biodegradable poly(ester amide) (PEA) fibers toward targeting neovessel formation and maturation. FGF2 and FGF9 were dual loaded using a mixed blend and emulsion electrospinning technique and exhibited differential and sustained release from PEA fibers over 28 days with preserved bioactivity. In vitro angiogenesis assays showed enhanced endothelial cell (EC) tube formation and directed migration of smooth muscle cells (SMCs) to platelet-derived growth factor (PDGF)-BB and stabilized EC/SMC tube formation. FGF2/FGF9-loaded PEA fibers did not induce inflammatory responses in vitro using human monocytes or in vivo after their subcutaneous implantation into mice. Histological examination showed that FGF2/FGF9-loaded fibers induced cell niche recruitment around the site of implantation. Furthermore, controlled in vivo delivery of FGF9 to mouse tibialis anterior (TA) muscle resulted in a dose-dependent expansion of mesenchymal progenitor-like cell layers and extracellular matrix deposition. Our data suggest that the release of FGF2 and FGF9 from PEA fibers offers an efficient differential and sustained growth factor delivery strategy with relevance to therapeutic angiogenesis.

Vascular smooth muscle cell differentiation from human stem/progenitor cells

Transplantation of vascular smooth muscle cells (VSMCs) is a promising cellular therapy to promote angiogenesis and wound healing. However, VSMCs are derived from diverse embryonic sources which may influence their role in the development of vascular disease and in its therapeutic modulation. Despite progress in understanding the mechanisms of VSMC differentiation, there remains a shortage of robust methods for generating lineage-specific VSMCs from pluripotent and adult stem/progenitor cells in serum-free conditions. Here we describe a method for differentiating pluripotent stem cells, such as embryonic and induced pluripotent stem cells, as well as skin-derived precursors, into lateral plate-derived VSMCs including 'coronary-like' VSMCs and neural crest-derived VSMC, respectively. We believe this approach will have broad applications in modeling origin-specific disease vulnerability and in developing personalized cell-based vascular grafts for regenerative medicine.

Fibroblast Growth Factor-9 Activates c-Kit Progenitor Cells and Enhances Angiogenesis in the Infarcted Diabetic Heart

We hypothesized that fibroblast growth factor-9 (FGF-9) would enhance angiogenesis via activating c-kit positive stem cells in the infarcted nondiabetic and diabetic heart. In brief, animals were divided into three groups: Sham, MI, and MI+FGF-9. Two weeks following MI or sham surgery, our data suggest that treatment with FGF-9 significantly diminished vascular apoptosis compared to the MI group in both C57BL/6 and db/db mice (p < 0.05). Additionally, the number of c-kit^+ve/SM α-actin^+ve cells and c-kit^+ve/CD31^+ve cells were greatly enhanced in the MI+FGF-9 groups relative to the MI suggesting FGF-9 enhances c-Kit cell activation and their differentiation into vascular smooth muscle cells and endothelial cells, respectively (p < 0.05). Histology shows that the total number of vessels were quantified for all groups and our data suggest that the FGF-9 treated groups had significantly more vessels than their MI counterparts (p < 0.05). Finally, echocardiographic data suggests a significant improvement in left ventricular output, as indicated by fractional shortening and ejection fraction in both nondiabetic and diabetic animals treated with FGF-9 (p < 0.05). Overall, our data suggests FGF-9 has the potential to attenuate vascular cell apoptosis, activate c-Kit progenitor cells, and enhance angiogenesis and neovascularization in C57BL/6 and db/db mice leading to improved cardiac function.

Fibroblast Growth Factor 9 Imparts Hierarchy and Vasoreactivity to the Microcirculation of Renal Tumors and Suppresses Metastases

Tumor vessel normalization has been proposed as a therapeutic paradigm. However, normal microvessels are hierarchical and vasoreactive with single file transit of red blood cells through capillaries. Such a network has not been identified in malignant tumors. We tested whether the chaotic tumor microcirculation could be reconfigured by the mesenchyme-selective growth factor, FGF9. Delivery of FGF9 to renal tumors in mice yielded microvessels that were covered by pericytes, smooth muscle cells, and a collagen-fortified basement membrane. This was associated with reduced pulmonary metastases. Intravital microvascular imaging revealed a haphazard web of channels in control tumors but a network of arterioles, bona fide capillaries, and venules in FGF9-expressing tumors. Moreover, whereas vasoreactivity was absent in control tumors, arterioles in FGF9-expressing tumors could constrict and dilate in response to adrenergic and nitric oxide releasing agents, respectively. These changes were accompanied by reduced hypoxia in the tumor core and reduced expression of the angiogenic factor VEGF-A. FGF9 was found to selectively amplify a population of PDGFRβ-positive stromal cells in the tumor and blocking PDGFRβ prevented microvascular differentiation by FGF9 and also worsened metastases. We conclude that harnessing local mesenchymal stromal cells with FGF9 can differentiate the tumor microvasculature to an extent not observed previously.