Vascular Plasticity Research Articles

Abstract 4134531: BST2 induces vascular smooth muscle cell plasticity and phenotype switching during cancer progression

Rationale: Smooth muscle cell (SMC) plasticity and phenotypic switching play prominent roles in the pathogenesis of multiple diseases like atherosclerosis and pulmonary hypertension, but their role in tumorigenesis is unknown. Objective: To investigate SMC diversity and plasticity in tumor angiogenesis and its underlying molecular drivers. Methods and Results: Here we use SMC-specific lineage-tracing mouse models and single cell RNA sequencing (scRNA-seq) to observe the phenotypic diversity of SMCs participating in tumor vascularization. We find that around 10% of SMCs adopt a phenotype which includes features traditionally associated with macrophage-like cells, suggesting they may contribute to the immune profile of the tumor microenvironment (TME). These cells are transcriptionally similar to ‘resolution phase’ M2b macrophages, which have been described to have a role in inflammation resolution. Signaling from bone marrow stromal antigen 2 (BST2) on the surface of tumor cells to PIRA2 on SMC promotes this phenotypic transition, leading to a SMC phenotype that is more proliferative, migratory, and phagocytic. Knockdown of BST2 in the tumor significantly decreases the transition towards a macrophage-like phenotype, and the cells that were able to transition had a comparatively higher inflammatory signal typically associated with anti-tumor effect. Conclusions: As BST2 is known to be a poor prognostic marker in multiple cancers where it is associated with an M2 macrophage-skewed TME, these studies suggest that phenotypically switched SMCs may have a previously unidentified role in this immunosuppressive milieu. The novel concept of SMC contribution to the immune landscape suggests manipulation of SMC phenotypic switching as an approach to altering cancer pathogenesis. Further translational work is needed to understand how this phenotypic switch could influence response to anti-cancer agents and if targeted inhibition of SMC plasticity would be therapeutically beneficial.

The Cerebrovascular Side of Plasticity: Microvascular Architecture across Health and Neurodegenerative and Vascular Diseases.

The delivery of nutrients to the brain is provided by a 600 km network of capillaries and microvessels. Indeed, the brain is highly energy demanding and, among a total amount of 100 billion neurons, each neuron is located just 10-20 μm from a capillary. This vascular network also forms part of the blood-brain barrier (BBB), which maintains the brain's stable environment by regulating chemical balance, immune cell transport, and blocking toxins. Typically, brain microvascular endothelial cells (BMECs) have low turnover, indicating a stable cerebrovascular structure. However, this structure can adapt significantly due to development, aging, injury, or disease. Temporary neural activity changes are managed by the expansion or contraction of arterioles and capillaries. Hypoxia leads to significant remodeling of the cerebrovascular architecture and pathological changes have been documented in aging and in vascular and neurodegenerative conditions. These changes often involve BMEC proliferation and the remodeling of capillary segments, often linked with local neuronal changes and cognitive function. Cerebrovascular plasticity, especially in arterioles, capillaries, and venules, varies over different time scales in development, health, aging, and diseases. Rapid changes in cerebral blood flow (CBF) occur within seconds due to increased neural activity. Prolonged changes in vascular structure, influenced by consistent environmental factors, take weeks. Development and aging bring changes over months to years, with aging-associated plasticity often improved by exercise. Injuries cause rapid damage but can be repaired over weeks to months, while neurodegenerative diseases cause slow, varied changes over months to years. In addition, if animal models may provide useful and dynamic in vivo information about vascular plasticity, humans are more complex to investigate and the hypothesis of glymphatic system together with Magnetic Resonance Imaging (MRI) techniques could provide useful clues in the future.

BST2 induces vascular smooth muscle cell plasticity and phenotype switching during cancer progression.

Smooth muscle cell (SMC) plasticity and phenotypic switching play prominent roles in the pathogenesis of multiple diseases, but their role in tumorigenesis is unknown. We investigated whether and how SMC diversity and plasticity plays a role in tumor angiogenesis and the tumor microenvironment. We use SMC-specific lineage-tracing mouse models and single cell RNA sequencing to observe the phenotypic diversity of SMCs participating in tumor vascularization. We find that a significant proportion of SMCs adopt a phenotype traditionally associated with macrophage-like cells. These cells are transcriptionally similar to 'resolution phase' M2b macrophages, which have been described to have a role in inflammation resolution. Computationally predicted by the ligand-receptor algorithm CellChat, signaling from BST2 on the surface of tumor cells to PIRA2 on SMCs promote this phenotypic transition; in vitro SMC assays demonstrate upregulation of macrophage transcriptional programs, and increased proliferation, migration, and phagocytic ability when exposed to BST2. Knockdown of BST2 in the tumor significantly decreases the transition towards a macrophage-like phenotype, and cells that do transition have a comparatively higher inflammatory signal typically associated with anti-tumor effect. As BST2 is known to be a poor prognostic marker in multiple cancers where it is associated with an M2 macrophage-skewed TME, these studies suggest that phenotypically switched SMCs may have a previously unidentified role in this immunosuppressive milieu. Further translational work is needed to understand how this phenotypic switch could influence the response to anti-cancer agents and if targeted inhibition of SMC plasticity would be therapeutically beneficial.

Regulation of Ptbp1-controlled alternative splicing of pyruvate kinase muscle by liver kinase B1 governs vascular smooth muscle cell plasticity in vivo.

Vascular smooth muscle cell (VSMC) plasticity is a state in which VSMCs undergo phenotypic switching from a quiescent contractile phenotype into other functionally distinct phenotypes. Although emerging evidence suggests that VSMC plasticity plays critical roles in the development of vascular diseases, little is known about the key determinant for controlling VSMC plasticity and fate. We found that smooth muscle cell-specific deletion of Lkb1 in tamoxifen-inducible Lkb1flox/flox;Myh11-Cre/ERT2 mice spontaneously and progressively induced aortic/arterial dilation, aneurysm, rupture, and premature death. Single-cell RNA sequencing and imaging-based lineage tracing showed that Lkb1-deficient VSMCs transdifferentiated gradually from early modulated VSMCs to fibroblast-like and chondrocyte-like cells, leading to ossification and blood vessel rupture. Mechanistically, Lkb1 regulates polypyrimidine tract binding protein 1 (Ptbp1) expression and controls alternative splicing of pyruvate kinase muscle (PKM) isoforms 1 and 2. Lkb1 loss in VSMC results in an increased PKM2/PKM1 ratio and alters the metabolic profile by promoting aerobic glycolysis. Treatment with PKM2 activator TEPP-46 rescues VSMC transformation and aortic dilation in Lkb1flox/flox;Myh11-Cre/ERT2 mice. Furthermore, we found that Lkb1 expression decreased in human aortic aneurysm tissue compared to control tissue, along with changes in markers of VSMC fate. Lkb1, via its regulation of Ptbp1-dependent alterative splicing of PKM, maintains VSMC in contractile states by suppressing VSMC plasticity.

Vascular Signaling Plasticity Reprograms Blood Delivery Mechanisms to Meet Fluctuating Neuronal Energy Needs

Neuronal computation is metabolically expensive and depends on precision delivery of energy substrates—oxygen and glucose—via tightly coordinated blood flow to ensure that energy demands are continually met. This is facilitated by neurovascular coupling (NVC)—a range of mechanisms matching neural activity to local blood flow. These NVC mechanisms are typically considered invariant, and whether they are reshaped according to ever-changing neuronal metabolic needs has not been examined. We present evidence that neural activity continually reprograms the blood flow control mechanisms embedded in the local vasculature, a process we refer to as ‘vascular signaling plasticity’ (VSP). Using an established enrichment paradigm, we find that animals housed in conditions that increase input to the barrel cortex for 7 days exhibit profound neuronal plasticity in this region. This resculpts local vascular reactivity to elevate blood delivery. Indeed, VSP results in increased basal capillary blood flow and augmented activity of vasodilatory agents in vivo manifesting as increased red blood cell (RBC) flux responses to capillary stimulation and upstream diameter changes measured using 2-photon laser scanning microscopy. Moreover, the sensitivity of capillaries to stimulation is also dramatically elevated in an ex vivo isolated capillary-arteriole preparation. Using K+-mediated capillary-to-arteriole electrical signaling as a springboard to study the molecular underpinnings of VSP, we find that this process induces a ~70% increase in the density of strong inward rectifier K+ (Kir2.1) currents in capillary endothelial cells, which profoundly augments the retrograde hyperpolarization generated by these channels to control upstream diameter at the level of the penetrating arteriole. Through whole-cell patch clamp electrophysiology, we characterize the mechanism of VSP induction and recapitulate this phenomenon in vitro. We validate our findings through Crispr/Cas9-mediated endothelial cell-specific knockout of the transcription factor responsible for VSP induction. Our data thus recast the vasculature as a plastic, brain-wide activity sensing network that is continually reshaped at the molecular level by local neuronal input, leading to precisely-tuned blood delivery to meet continually fluctuating neural energy needs. VSP represents a new dimension to brain plasticity that may underpin a range of vital physiological processes and is likely disrupted in numerous brain pathologies with a blood flow component. This work was supported by the American Heart Association (23POST1023086), and NIH grants 1DP2NS121347, 1R01AG066645, and 5R01NS115401. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Functional profiling of resident cells during vascular aging

Introduction: Depending on surrounding cell types, substrate mechanics, and chemical agonists, vascular cell types – including endothelial (ECs) and smooth muscle cells (VSMC) — modulate their behavior to maintain homeostasis. Aging perturbs this homeostasis resulting in EC and SMC dysfunction, marked by impaired barrier integrity and pathological ECM remodeling. Endothelial-to-mesenchymal transition (EndMT) in ECs and “dedifferentiation” of VSMCs towards a synthetic phenotype are phenomenon under investigation as cellular drivers of the widespread dysregulation seen with aging. The overall goal of this project is to understand the effect of cross-talk between ECM and growth factor signaling on vascular cell plasticity during aging. Materials and Methods: Human aortic endothelial cells (HAECs) were seeded onto transwell inserts after seven days treatment with or without TGF-β. After growing to confluence on the insert, cells were subjected to a FITC-dextran transwell assay. A parallel group of cells was seeded onto fibronectin coated glass-bottom dishes and stained for the expression of focal adhesion proteins and cell-type markers. Mouse aortic smooth muscle cells (maSMCs) were isolated from C57Bl6 mice at 3 (young), 6 (early middle-aged; EMA), 9 (middle-age; MA), or greater than 18 months of age (old). Cells were seeded onto dye-quenched (DQ) collagen type I (Col-I) substrate before gain of fluorescence was measured in proximity to the cell as well as in the surrounding media. A parallel group of cells were allowed to grow in media containing FITC Col-I, and gain of fluorescence was measured in proximity to the cells. Each cell type (3M, 6M, 9M, and 18M) in both experiments (DQ and FITC) were further treated with MMP inhibitor, TG2 inhibitor and TGF-β1 to measure their impacts on Col-I turnover. Results: Barrier function was not impaired in ECs cultured with TGF-β1, relative to their untreated counterparts. Mouse aortic SMCs isolated from older mice had decreased rates of Col-I cleavage and were more susceptible to MMP inhibition than their younger counterparts. Conclusions: maSMCs from older mice have lower Col-I turnover than their younger counterparts. This is consistent with bulk tissue behavior, as it is well known that relative collagen levels increase in the elastic vasculature as we age. TGF-β1 treatment did not have an effect on permeability of 4kd FITC-dextran, it is feasible that there will be an impact on the larger 70kd fragments. Travis Brady is supported by the NASEM Ford Foundation Pre-doctoral Fellowship. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Blood Vessel-Targeted Therapy in Colorectal Cancer: Current Strategies and Future Perspectives.

The vasculature is a key player and regulatory component in the multicellular microenvironment of solid tumors and, consequently, a therapeutic target. In colorectal carcinoma (CRC), antiangiogenic treatment was approved almost 20 years ago, but there are still no valid predictors of response. In addition, treatment resistance has become a problem. Vascular heterogeneity and plasticity due to species-, organ-, and milieu-dependent phenotypic and functional differences of blood vascular cells reduced the hope of being able to apply a standard approach of antiangiogenic therapy to all patients. In addition, the pathological vasculature in CRC is characterized by heterogeneous perfusion, impaired barrier function, immunosuppressive endothelial cell anergy, and metabolic competition-induced microenvironmental stress. Only recently, angiocrine proteins have been identified that are specifically released from vascular cells and can regulate tumor initiation and progression in an autocrine and paracrine manner. In this review, we summarize the history and current strategies for applying antiangiogenic treatment and discuss the associated challenges and opportunities, including normalizing the tumor vasculature, modulating milieu-dependent vascular heterogeneity, and targeting functions of angiocrine proteins. These new strategies could open perspectives for future vascular-targeted and patient-tailored therapy selection in CRC.

Arterial Stiffness: From Basic Primers to Integrative Physiology.

The elastic properties of conductance arteries are one of the most important hemodynamic functions in the body, and data continue to emerge regarding the importance of their dysfunction in vascular aging and a range of cardiovascular diseases. Here, we provide new insight into the integrative physiology of arterial stiffening and its clinical consequence. We also comprehensively review progress made on pathways/molecules that appear today as important basic determinants of arterial stiffness, particularly those mediating the vascular smooth muscle cell (VSMC) contractility, plasticity and stiffness. We focus on membrane and nuclear mechanotransduction, clearance function of the vascular wall, phenotypic switching of VSMCs, immunoinflammatory stimuli and epigenetic mechanisms. Finally, we discuss the most important advances of the latest clinical studies that revisit the classical therapeutic concepts of arterial stiffness and lead to a patient-by-patient strategy according to cardiovascular risk exposure and underlying disease.

Molecular mechanisms and biomarkers underlying the protective roles of the nutraceutical laminarin against ischaemic strokes

ABSTRACT Stroke is the second leading cause of death and a major cause of disability worldwide. Ischemic stroke accounts for approximately >60% of all stroke, and >80% of strokes can be prevented. Middle cerebral artery occlusion (MCAO) is a common cause of stroke in humans. MCAO is associated with blood vessel-related problems, such as reduced vascular plasticity and hypertension. These problems can be attenuated by the use of nutraceuticals such as laminarin. Laminarin is a storage glucan commonly found in brown algae. Accumulating evidence and studies have revealed that laminarin is a promising candidate drug for treating ischaemic stroke. However, details on pharmaceutical targets and molecular mechanisms underlying laminarin’s beneficial effects for treating ischaemic stroke remains largely unknown. Herein, we applied network pharmacology, bioinformatic analysis, and middle cerebral artery occlusion model to delineate the protective role of laminarin. By comparing the laminarin- and MCAO-associated genes, we identified 23 potential targets including tumour necrosis factor (TNF), vascular endothelial growth factor A, selectin P, presenilin 1, fibroblast growth factor 2, microtubule-associated protein tau, caspase 3, matrix metallopeptidase 1, 5-hydroxytryptamine receptor 2A, telomerase reverse transcriptase, interleukin 2, signal transducer and activator of transcription 3 (STAT3), ATP binding cassette subfamily B member 1, catalase, superoxide dismutase 2, adenosine A1 receptor, adenosine A2a receptor, 5-hydroxytryptamine receptor 1B, heat shock protein 90 alpha family class A member 1, matrix metallopeptidase 8, BCL2-like 1, galectin 3, and epoxide hydrolase 2 of laminarin against ischaemic stroke. The gene ontology enrichment and Kyoto Encyclopedia of Genes and Genomes enrichment analyses highlighted the importance of this gene cluster in the development of blood vessels, neuronal cell death, brain functions, and neuroinflammation. Furthermore, molecular docking analysis suggested a direct binding of laminarin to its target proteins STAT3 and TNF. Our results provide the pharmaceutical targets and delineate the details regarding the molecular mechanisms underlying the beneficial effects of laminarin against ischaemic stroke. Moreover, our findings support those of previous studies suggesting laminarin as a promising drug for treating ischaemic stroke.

Glioblastoma vascular plasticity limits effector T-cell infiltration and is blocked by cAMP activation.

Glioblastoma (GBM) is the deadliest form of brain cancer, characterized as a highly angiogenetic and immunosuppressive malignancy. Although immune checkpoint blockades have revolutionized cancer therapy, their therapeutic efficacy in GBM has been far less than expected or even ineffective. Here, we reveal that the genomic signature of glioma-derived endothelial cells (GdECs) correlates with an immunosuppressive state and poor prognosis of glioma patients. In vitro model of GdECs differentiation is established for drug screening, and we identify that cAMP activators could effectively block the GdECs formation by inducing oxidative stress. cAMP activator impairs the GdECs differentiation in vivo, normalizes the tumor vessels, and alters the immune profile, especially increasing the influx and function of CD8+ effector T cells. The dual blockade of GdECs and PD-1 induces tumor regression and establishes anti-tumor immune memory. Our study reveals that endothelial transdifferentiation of GBM shapes an endothelial immune cell barrier and supports the clinical development of combining GdECs blockade and immunotherapy for GBM.

A phloem-localized Arabidopsis metacaspase (AtMC3) improves drought tolerance.

Increasing drought phenomena pose a serious threat to agricultural productivity. Although plants have multiple ways to respond to the complexity of drought stress, the underlying mechanisms of stress sensing and signaling remain unclear. The role of the vasculature, in particular the phloem, in facilitating inter-organ communication is critical and poorly understood. Combining genetic, proteomic and physiological approaches, we investigated the role of AtMC3, a phloem-specific member of the metacaspase family, in osmotic stress responses in Arabidopsis thaliana. Analyses of the proteome in plants with altered AtMC3 levels revealed differential abundance of proteins related to osmotic stress pointing into a role of the protein in water-stress-related responses. Overexpression of AtMC3 conferred drought tolerance by enhancing the differentiation of specific vascular tissues and maintaining higher levels of vascular-mediated transportation, while plants lacking the protein showed an impaired response to drought and inability to respond effectively to the hormone abscisic acid. Overall, our data highlight the importance of AtMC3 and vascular plasticity in fine-tuning early drought responses at the whole plant level without affecting growth or yield.

Heterogeneous expression of alternatively spliced lncRNA mediates vascular smooth cell plasticity

9p21.3 locus polymorphisms have the strongest correlation with coronary artery disease, but as a noncoding locus, disease connection is enigmatic. The lncRNA ANRIL found in 9p21.3 may regulate vascular smooth muscle cell (VSMC) phenotype to contribute to disease risk. We observed significant heterogeneity in induced pluripotent stem cell-derived VSMCs from patients homozygous for risk versus isogenic knockout or nonrisk haplotypes. Subpopulations of risk haplotype cells exhibited variable morphology, proliferation, contraction, and adhesion. When sorted by adhesion, risk VSMCs parsed into synthetic and contractile subpopulations, i.e., weakly adherent and strongly adherent, respectively. Of note, >90% of differentially expressed genes coregulated by haplotype and adhesion and were associated with Rho GTPases, i.e., contractility. Weakly adherent subpopulations expressed more short isoforms of ANRIL, and when overexpressed in knockout cells, ANRIL suppressed adhesion, contractility, and αSMA expression. These data suggest that variable lncRNA penetrance may drive mixed functional outcomes that confound pathology.

Effect of ECM and mechanical strain on vascular cell plasticity

Introduction: Depending on surrounding cell types, substrate mechanics, and chemical agonists, vascular smooth muscle cells (VSMCs) alternate between a contractile and synthetic phenotype. While endothelial cells (ECs) do not modulate their phenotype in this way, their behavior is highly dependent on location within the body. These variations are part of healthy vascular function, but improper phenotype has been implicated in cardiovascular disease. Atherosclerotic lesions, for example, have been found to be high in dedifferentiated, synthetic VSMCs as well as endothelial cells that have undergone endothelial to mesenchymal transition (EndMT). The overall goal of this project is to understand the effect of cross-talk between ECM and mechanical strain on vascular cell plasticity during aging. Materials and Methods: Mouse aortic smooth muscle cells (maSMCs) were isolated from C57Bl6 mice at less than 3 months (young), 6 to 10 months of age (middle-aged; MA), or greater than 15 months of age (old). Cells were then seeded onto dye-quenched (DQ) collagen type I (Col-I) substrate and measured for gain of fluorescent signal over 3 days. Human aortic endothelial cells (HAECs) were seeded onto glass cover slips or fibronectin coated PDMS chambers. Cells were further treated with or without TGF-β2 with daily media changes over 3 days. IF images were captured with a Leica Confocal microscope and quantification was performed using ImageJ. Results: ECs cultured on glass or treated with TGF-β2 show increased expression of SM22α and decreased expression of VECAD. Physiological strain (10%) did not cause changes in expression relative to static (0%). Mouse aortic SMCs isolated from older mice had significantly decreased rates of Col-I cleavage. Conclusions: maSMCs from older mice have lower Col-I turnover than their younger counterparts. This is consistent with bulk tissue behavior, as it is well known that relative collagen levels increase in the elastic vasculature as we age. HAECs on stiff substrates are more likely to show signs of EndMT – consistent with other studies. The addition of agonists such as TGF-β2 can reproduce this behavior in cells cultured on soft substrates. NASEM Ford Foundation Pre-Doctoral Fellowship and NHBLI grant R01HL148112 01 (L.S.) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Vascular signaling plasticity reprograms neurovascular coupling pathways to precisely match energy delivery to neuronal metabolic needs

Neuronal computation is metabolically expensive and relies on the timely delivery of energy substrates via tightly controlled blood flow to prevent energetic deficits. The range of mechanisms responsible for this coupling of neural activity to blood flow are collectively termed ‘neurovascular coupling’ (NVC). These NVC mechanisms are typically assumed to be invariant and the possibility that they may be plastic, allowing reshaping of energy delivery according to ever-shifting neuronal metabolic needs, has not been considered. We present evidence that neuronal activity resculpts blood flow control mechanisms inherent to the endothelium, which forms the inner lining of all blood vessels, through a process we refer to as vascular signalling plasticity (VSP). Using an environmental enrichment paradigm, we find that housing mice in an environment that increases input to the barrel cortex drives profound synaptic plasticity within this network. This is accompanied by a remarkable resculpting of local vascular reactivity, augmenting the efficacy of mechanisms that signal for an increase in blood flow. This increase in sensitivity manifests as an increase red blood cell flux to capillary stimulation with extracellular K+, which activates strong inward rectifier K+ (Kir2.1) channel-dependent capillary-to-arteriole electrical signalling to elicit hyperemia. To support this augmentation, we find that VSP induces a ~70% increase in the density of Kir2.1 channels in endothelial cells membranes which is underlain by transcriptional and translational changes in capillary ECs. Using an ex vivo capillary-arteriole preparation, we demonstrate that this increase in membrane Kir2.1 channels translates into a profound shift in the sensitivity of capillaries to K+ stimulation to evoke upstream arteriolar dilation. Together, these results suggest that increasing neuronal energy consumption leads to a profound potentiation of the retrograde hyperpolarization generated by the endothelium during activity, enhancing upstream dilation at the penetrating arteriole and augmenting blood delivery to match enhanced local needs. Our data thus recast the capillary bed as a plastic, brain-wide, neural activity sensing network that is modulated at the molecular level by local neural input. This allows fine-tuning of existing blood delivery mechanisms to meet continually fluctuating neural energy needs. VSP represents a novel facet of brain plasticity that may be utilised by various physiological processes and may be disrupted in aging and in the broad range of brain pathologies that have a vascular component. Support for this work was provided by the NIH National Institute on Aging and National Institute of Neurological Disorders and Stroke (1R01AG066645, 5R01NS115401 [PI: S. Sakadžić], and 1DP2NS121347-01, to T.A.L), the American Heart Association (Awards 17SDG33670237 and 19IPLOI34660108 to T.A.L) and an NIH S10 grant (S10 OD026698, to University of Maryland School of Medicine CIBR Core Confocal Facility). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Abstract 396: Plasticity Of The Tumor Vasculature Is Induced By Tumor Cells Via Cell Surface Receptor Tetherin

It is increasingly clear that cardiovascular disease and cancer have shared pathophysiological mechanisms beyond traditional risk factors. Murine models have demonstrated tumors grow more quickly in the presence of cardiovascular abnormalities, and targeting of shared signaling pathways has proven efficacious in both diseases. It is unknown, however, if smooth muscle cell (SMC) plasticity as seen in atherogenesis represents yet another biologic parallel. Our aim was to understand if SMC plasticity occurs in tumor vasculature, and how those transitions are induced. Syngeneic tumor cell lines were implanted on the flanks of SMC lineage-traced mice and allowed to grow for 11 days. Fluorescent microscopy of the tumors revealed a population of SMCs that moved away from angiogenic vessels and lost canonical SMC markers. We used single cell RNA sequencing to characterize the in vivo transcriptional phenotype of SMCs within the tumor. Principal component analysis demonstrated distinct SMC populations, with pseudotime analysis suggesting transitions from a contractile SMC towards a more macrophage-like transcriptional state. CellChat ligand-receptor analysis was leveraged to examine differential interactions between tumor cells and classic macrophages versus macrophage-like SMCs. The only unique interaction was between cell surface receptors Tetherin on tumor cells and paired immunoglobulin-like receptor A2 (PIRA2) on macrophage-like SMCs. In vitro murine SMCs treated with recombinant Tetherin decreased contractile SMC markers and increased macrophage markers by qPCR. Exposure to recombinant Tetherin also increased overall proliferative rate, migratory capacity, and phagocytic ability compared to untreated SMCs. The knockdown of PIRA2 in murine SMCs abrogates these apparent effects of Tetherin. Our findings demonstrate that SMCs in tumor vasculature, like those in atherogenesis, demonstrate significant degrees of plasticity. One of the phenotypic changes is towards a macrophage-like state. In vitro studies suggest interaction between Tetherin and PIRA2 receptors is sufficient to induce this switching. Ongoing murine studies will establish whether in vivo inhibition of the Tetherin-PIRA2 axis decreases vascular plasticity.

Alzheimer’s Disease from the Amyloidogenic Theory to the Puzzling Crossroads between Vascular, Metabolic and Energetic Maladaptive Plasticity

Alzheimer's disease (AD) is a progressive and degenerative disease producing the most common type of dementia worldwide. The main pathogenetic hypothesis in recent decades has been the well-known amyloidogenic hypothesis based on the involvement of two proteins in AD pathogenesis: amyloid β (Aβ) and tau. Amyloid deposition reported in all AD patients is nowadays considered an independent risk factor for cognitive decline. Vascular damage and blood-brain barrier (BBB) failure in AD is considered a pivotal mechanism for brain injury, with increased deposition of both immunoglobulins and fibrin. Furthermore, BBB dysfunction could be an early sign of cognitive decline and the early stages of clinical AD. Vascular damage generates hypoperfusion and relative hypoxia in areas with high energy demand. Long-term hypoxia and the accumulation within the brain parenchyma of neurotoxic molecules could be seeds of a self-sustaining pathological progression. Cellular dysfunction comprises all the elements of the neurovascular unit (NVU) and neuronal loss, which could be the result of energy failure and mitochondrial impairment. Brain glucose metabolism is compromised, showing a specific region distribution. This energy deficit worsens throughout aging. Mild cognitive impairment has been reported to be associated with a glucose deficit in the entorhinal cortex and in the parietal lobes. The current aim is to understand the complex interactions between amyloid β (Aβ) and tau and elements of the BBB and NVU in the brain. This new approach aimed at the study of metabolic mechanisms and energy insufficiency due to mitochondrial impairment would allow us to define therapies aimed at predicting and slowing down the progression of AD.

Variation of the Bifurcation of Brachial Artery: A Cadaveric Study

INTRODUCTION Knowledge of variation in origin, course and bifurcation of brachial artery is significant for the vascular surgeons or radiologist for accurate diagnostic interpretation as well as while performing traumatic vascular repair, bypass procedures and constructive plastic surgeries. Therefore, the anatomical knowledge of the higher bifurcation of brachial artery is substantial for all cases of traumatic amputations and revascularization techniques. The present study aims to find out prevalence of variation of bifurca- tion of brachial artery in cadavers in the Department of Anatomy. MATERIAL AND METHODS An institutional based descriptive cross-sectional study was conducted on 15 formalin fixed embalmed adult human cadavers in the Department of Anatomy (Dissection Hall) at Universal College of Medical Sciences, Bhairahawa, Nepal. The study duration was from July 2021 to 15th October 2021. The finer dissection was made, the brachial artery was exposed, the level of variation was noted as well as length of brachial artery was measured then it was photographed by using digital camera. RESULTS In fifteen cadavers (right upper limb 15 and left upper limb 15), the site of termination was at the level of neck of radius 86.6% while, higher termination of brachial artery was observed in 2 upper extremities (6.7%) and, distal level of termination 2 (6.7%). CONCLUSION Knowing anatomical variations of arteries are of mandatory requirement for planning invasive and surgical treatment since lack of knowledge can cause serious vascular lesions. However, the prevalence of variation of bifurcation of brachial artery in our study is less than other similar studies. Hence, it may cause difficulty in clinical and surgical procedures.

Lymphatic/blood vessel plasticity: motivation for a future research area based on present and past observations.

The lymphatic system plays a significant role in homeostasis and drainage of excess fluid back into venous circulation. Lymphatics are also associated with a number of diseases including lymphedema, tumor metastasis, and various lymphatic malformations. Emerging evidence suggests that lymphatics might have a bigger connection to the blood vascular system than originally presumed. As these two systems are often studied in isolation, several knowledge gaps exist surrounding what constitutes lymphatic vascular plasticity, under what conditions it arises, and where structures characteristic of plasticity can form. The objective of this review is to overview current structural, cell lineage-based, and cell identity-based evidence for lymphatic plasticity. These examples of plasticity will then be considered in the context of potential clinical and surgical implications of this evolving research area. This review details our current understanding of lymphatic plasticity, highlights key unanswered questions in the field, and motivates future research aimed at clarifying the role and therapeutic potential of lymphatic plasticity in disease.

Transcription factor GATA6 promotes migration of human coronary artery smooth muscle cells in vitro.

Vascular smooth muscle cell plasticity plays a pivotal role in the pathophysiology of vascular diseases. Despite compelling evidence demonstrating the importance of transcription factor GATA6 in vascular smooth muscle, the functional role of GATA6 remains poorly understood. The aim of this study was to elucidate the role of GATA6 on cell migration and to gain insight into GATA6-sensitive genes in smooth muscle. We found that overexpression of GATA6 promotes migration of human coronary artery smooth muscle cells in vitro, and that silencing of GATA6 in smooth muscle cells resulted in reduced cellular motility. Furthermore, a complete microarray screen of GATA6-sensitive gene transcription resulted in 739 upregulated and 248 downregulated genes. Pathways enrichment analysis showed involvement of transforming growth factor beta (TGF-β) signaling which was validated by measuring mRNA expression level of several members. Furthermore, master regulators prediction based on microarray data revealed several members of (mitogen activated protein kinase) MAPK pathway as a master regulators, reflecting involvement of MAPK pathway also. Our findings provide further insights into the functional role of GATA6 in vascular smooth muscle and suggest that targeting GATA6 may constitute as a new approach to inhibit vascular smooth muscle migration.

Hippocampal blood flow rapidly and preferentially increases after a bout of moderate-intensity exercise in older adults with poor cerebrovascular health.

Over the course of aging, there is an early degradation of cerebrovascular health, which may be attenuated with aerobic exercise training. Yet, the acute cerebrovascular response to a single bout of exercise remains elusive, particularly within key brain regions most affected by age-related disease processes. We investigated the acute global and region-specific cerebral blood flow (CBF) response to 15minutes of moderate-intensity aerobic exercise in older adults (≥65years; n = 60) using arterial spin labeling magnetic resonance imaging. Within 0-6min post-exercise, CBF decreased across all regions, an effect that was attenuated in the hippocampus. The exercise-induced CBF drop was followed by a rebound effect over the 24-minute postexercise assessment period, an effect that was most robust in the hippocampus. Individuals with low baseline perfusion demonstrated the greatest hippocampal-specific CBF effect post-exercise, showing no immediate drop and a rapid increase in CBF that exceeded baseline levels within 6-12minutes postexercise. Gains in domain-specific cognitive performance postexercise were not associated with changes in regional CBF, suggesting dissociable effects of exercise on acute neural and vascular plasticity. Together, the present findings support a precision-medicine framework for the use of exercise to target brain health that carefully considers age-related changes in the cerebrovascular system.