Endothelial progenitor cells in ischemic stroke: an exploration from hypothesis to therapy

Carotid artery transplantation of brain endothelial cells enhances neuroprotection and neurorepair in ischaemic stroke rats

Brain microvascular endothelial cells (BMECs), an important component of the neurovascular unit, can promote angiogenesis and synaptic formation in ischaemic mice after brain parenchyma transplantation. Since the therapeutic efficacy of cell-based therapies depends on the extent of transplanted cell residence in the target tissue and cell migration ability, the delivery route has become a hot research topic. In this study, we investigated the effects of carotid artery transplantation of BMECs on neuronal injury, neurorepair, and neurological dysfunction in rats after cerebral ischaemic attack. Purified passage 1 endothelial cells (P1-BMECs) were prepared from mouse brain tissue. Adult rats were subjected to transient middle cerebral artery occlusion (MCAO) for 30 min. Then, the rats were treated with 5 × 105 P1-BMECs through carotid artery infusion or tail vein injection. We observed that carotid artery transplantation of BMECs produced more potent neuroprotective effects than caudal injection in MCAO rats, including reducing infarct size and alleviating neurological deficits in behavioural tests. Carotid artery-transplanted BMECs displayed a wider distribution in the ischaemic rat brain. Immunostaining for endothelial progenitor cells and the mature endothelial cell markers CD34 and RECA-1 showed that carotid artery transplantation of BMECs significantly increased angiogenesis. Carotid artery transplantation of BMECs significantly increased the number of surviving neurons, decreased the cerebral infarction volume, and alleviated neurological deficits. In addition, we found that carotid artery transplantation of BMECs significantly enhanced ischaemia-induced hippocampal neurogenesis, as measured by doublecortin (DCX) and Ki67 double staining within 2 weeks after ischaemic injury. We conclude that carotid artery transplantation of BMECs can promote cerebral angiogenesis, neurogenesis, and neurological function recovery in adult rats after ischaemic stroke. Our results suggest that carotid injection of BMECs may be a promising new approach for treating acute brain injuries.

Gemigliptin, a potent selective dipeptidyl peptidase 4 inhibitor, protects endothelial progenitor cells by oxidative stress via caspase-3 dependent pathway

Endothelial progenitor cells (EPCs) are exclusive players in vasculogenesis and endothelial regeneration. EPCs are of two types and their differentiation is mediated by different growth factors. A decrease in EPC number and function causes cardiovascular abnormalities and reduced angiogenesis. Various studies has documented a role of EPCs in diabetes. EPCs treatment with different drugs improve insulin secretion but causes other abnormalities. In vivo and in vitro studies have reported anti glycation effect of gemigliptin but no data is available on in vitro effect of gemigliptin on EPC number and functional credibility. The current study was aimed to find an in vitro effect of gemigliptin on EPC number and function along with an effective treatment dose of gemigliptin. EPCs were isolated, cultured and phenotypically characterized using Dil- AcLDL and ulex-lectin fluorescence staining. EPCs were then treated with different doses of Zemiglo and their viability analyzed with viability assay using water-soluble tetrazolium salt (WST-1), by Annexin V and Propidium Iodide (PI) staining, senescence-associated beta-galactosidase (SA-β-gal) staining, western blot and Flow cytometric analysis of apoptotic signals. The results demonstrated that the isolated EPCs has typical endothelial phenotypes. And these EPCs were of two types based on morphology i.e., early and late EPCs. Gemigliptin dose dependently improved the EPCs morphology and increased EPCs viability, the most effective dose being the 20 μM. Gemigliptin at 10 μM, 20 μM and 50 μM significantly increased the BCL-2 levels and at 20 μM significantly decreased the Caspase-3 levels in EPCs. In conclusion, gemigliptin dose dependently effects the EPCs viability and morphology through Caspase-3 signaling. Our results are the first report of gemigliptin effect on EPC viability and morphology.

An update on stem cell therapy for stroke patients: Where are we now?

With a foundation built upon initial work from the 1980s demonstrating graft viability in cerebral ischemia, stem cell transplantation has shown immense promise in promoting survival, enhancing neuroprotection and inducing neuroregeneration, while mitigating both histological and behavioral deficits that frequently accompany ischemic stroke. These findings have led to a number of clinical trials that have thoroughly supported a strong safety profile for stem cell therapy in patients but have generated variable efficacy. As preclinical evidence continues to expand through the investigation of new cell lines and optimization of stem cell delivery, it remains critical for translational models to adhere to the protocols established through basic scientific research. With the recent shift in approach towards utilization of stem cells as a conjunctive therapy alongside standard thrombolytic treatments, key issues including timing, route of administration, and stem cell type must each be appropriately translated from the laboratory in order to resolve the question of stem cell efficacy for cerebral ischemia that ultimately will enhance therapeutics for stroke patients towards improving quality of life.

Human Cord Blood Endothelial Progenitor Cells and Pregnancy Complications (Preeclampsia, Gestational Diabetes Mellitus, and Fetal Growth Restriction)

Hemangioblasts give rise to endothelial progenitor cells (EPCs), which also express the cell surface markers CD133 and c-kit. They may differentiate into the outgrowth endothelial cells (OECs) that control neovascularization in the developing embryo. According to numerous studies, reduced levels of EPCs in circulation have been linked to human cardiovascular disorders. Furthermore, preeclampsia and senescence have been linked to levels of EPCs produced from cord blood. Uncertainties surround how preeclampsia affects the way EPCs function. It is reasonable to speculate that preeclampsia may have an impact on the function of fetal EPCs during the in utero period; however, the present literature suggests that maternal vasculopathies, including preeclampsia, damage fetal circulation. Additionally, the differentiation potential and general activity of EPCs may serve as an indicator of the health of the fetal vascular system as they promote neovascularization and repair during pregnancy. Thus, the purpose of this review is to compare-through the assessment of their quantity, differentiation potency, angiogenic activity, and senescence-the angiogenic function of fetal EPCs obtained from cord blood for normal and pregnancy problems (preeclampsia, gestational diabetes mellitus, and fetal growth restriction). This will shed light on the relationship between the angiogenic function of fetal EPCs and pregnancy complications, which could have an effect on the management of long-term health issues like metabolic and cardiovascular disorders in offspring with abnormal vasculature development.

Stem cell-based interventions for the treatment of stroke in newborn infants

BACKGROUND

Perinatal stroke refers to a diverse but specific group of cerebrovascular diseases that occur between 20 weeks of fetal life and 28 days of postnatal life. Acute treatment options for perinatal stroke are limited supportive care, such as controlling hypoglycemia and seizures. Stem cell-based therapies offer a potential therapeutic approach to repair, restore, or regenerate injured brain tissue. Preclinical findings have culminated in ongoing human neonatal studies.

OBJECTIVES

To evaluate the benefits and harms of stem cell-based interventions for the treatment of stroke in newborn infants compared to control (placebo or no treatment) or stem-cell based interventions of a different type or source.

SEARCH METHODS

We searched CENTRAL, PubMed, Embase, and three trials registries in February 2023. We planned to search the reference lists of included studies and relevant systematic reviews for studies not identified by the database searches.

SELECTION CRITERIA

We attempted to include randomized controlled trials, quasi-randomized controlled trials, and cluster trials that evaluated any of the following comparisons. • Stem cell-based interventions (any type) versus control (placebo or no treatment) • Mesenchymal stem/stromal cells (MSCs) of a specifictype (e.g. number of doses or passages) or source (e.g. autologous/allogeneic or bone marrow/cord) versus MSCs of another type or source • Stem cell-based interventions (other than MSCs) of a specific type (e.g. mononuclear cells, oligodendrocyte progenitor cells, neural stem cells, hematopoietic stem cells, or induced pluripotent stem cell-derived cells) or source (e.g. autologous/allogeneic or bone marrow/cord) versus stem cell-based interventions (other than MSCs) of another type or source • MSCs versus stem cell-based interventions other than MSCs We planned to include all types of transplantation regardless of cell source (bone marrow, cord blood, Wharton's jelly, placenta, adipose tissue, peripheral blood), type of graft (autologous or allogeneic), and dose.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were all-cause neonatal mortality, major neurodevelopmental disability, and immune rejection or any serious adverse event. Our secondary outcomes included all-cause mortality prior to first hospital discharge, seizures, adverse effects, and death or major neurodevelopmental disability at 18 to 24 months of age. We planned to use GRADE to assess the certainty of evidence for each outcome.

MAIN RESULTS

We identified no completed or ongoing randomized trials that met our inclusion criteria. We excluded three studies: two were phase 1 trials, and one included newborn infants with conditions other than stroke (i.e. cerebral ischemia and anemia). Among the three excluded studies, we identified the first phase 1 trial on the use of stem cells for neonatal stroke. It reported that a single intranasal application of bone marrow-derived MSCs in term neonates with a diagnosis of perinatal arterial ischemic stroke (PAIS) was feasible and apparently not associated with severe adverse events. However, the trial included only 10 infants, and follow-up was limited to three months.

AUTHORS' CONCLUSIONS

No evidence is currently available to evaluate the benefits and harms of stem cell-based interventions for treatment of stroke in newborn infants. We identified no ongoing studies. Future clinical trials should focus on standardizing the timing and method of cell delivery and cell processing to optimize the therapeutic potential of stem cell-based interventions and safety profiles. Phase 1 and large animal studies might provide the groundwork for future randomized trials. Outcome measures should include all-cause mortality, major neurodevelopmental disability and immune rejection, and any other serious adverse events.

Targeting endothelial cells with golden spice curcumin: A promising therapy for cardiometabolic multimorbidity

Cardiometabolic multimorbidity (CMM) is an increasingly significant global public health concern. It encompasses the coexistence of multiple cardiometabolic diseases, including hypertension, stroke, heart disease, atherosclerosis, and T2DM. A crucial component to the development of CMM is the disruption of endothelial homeostasis. Therefore, therapies targeting endothelial cells through multi-targeted and multi-pathway approaches hold promise for preventing and treatment of CMM. Curcumin, a widely used dietary supplement derived from the golden spice Carcuma longa, has demonstrated remarkable potential in treatment of CMM through its interaction with endothelial cells. Numerous studies have identified various molecular targets of curcumin (such as NF-κB/PI3K/AKT, MAPK/NF-κB/IL-1β, HO-1, NOs, VEGF, ICAM-1 and ROS). These findings highlight the efficacy of curcumin as a therapeutic agent against CMM through the regulation of endothelial function. It is worth noting that there is a close relationship between the progression of CMM and endothelial damage, characterized by oxidative stress, inflammation, abnormal NO bioavailability and cell adhesion. This paper provides a comprehensive review of curcumin, including its availability, pharmacokinetics, pharmaceutics, and therapeutic application in treatment of CMM, as well as the challenges and future prospects for its clinical translation. In summary, curcumin shows promise as a potential treatment option for CMM, particularly due to its ability to target endothelial cells. It represents a novel and natural lead compound that may offer significant therapeutic benefits in the management of CMM.

Verification of Therapeutic Effect through Accelerator Mass Spectrometry-Based Single Cell Level Quantification of hESC-Endothelial Cells Distributed into an Ischemic Model

As the potential of pluripotent stem cell-derived differentiated cells has been demonstrated in regenerative medicine, differentiated vascular endothelial cells (ECs) are emerging as a therapeutic agent for the cardiovascular system. To verify the therapeutic efficacy of differentiated ECs in an ischemic model, human embryonic stem cells (hESCs) are induced as EC lineage and produce high-purity ECs through fluorescence-activated cell sorting (FACS). When hESC-ECs are transplanted into a hindlimb ischemic model, it is confirmed that blood flow and muscle regeneration are further improved by creating new blood vessels together with autologous ECs than the primary cell as cord blood endothelial progenitor cells (CB-EPCs). In addition, previously reported studies show the detection of transplanted cells engrafted in blood vessels through various tracking methods, but fail to provide accurate quantitative values over time. In this study, it is demonstrated that hESC-ECs are engrafted approximately sevenfold more than CB-EPCs by using an accelerator mass spectrometry (AMS)-based cell tracking technology that can perform quantification at the single cell level. An accurate quantification index is suggested. It has never been reported in in vivo kinetics of hESC-ECs that can act as therapeutic agents.

Pericyte-Mediated Molecular Mechanisms Underlying Tissue Repair and Functional Recovery after Ischemic Stroke

There are still many patients suffering from ischemic stroke and related disabilities worldwide. To develop a treatment that promotes functional recovery after acute ischemic stroke, we need to elucidate endogenous tissue repair mechanisms. The concept of a neurovascular unit (NVU) indicates the importance of a complex orchestration of cell-cell interactions and their microenvironment in the physiology and pathophysiology of various central nervous system diseases, particularly ischemic stroke. In this concept, microvascular pericytes play a crucial role in regulating the blood-brain barrier integrity, cerebral blood flow (CBF), and vascular stability. Recent evidence suggests that pericytes are also involved in the tissue repair leading to functional recovery following acute ischemic stroke through the interaction with other cell types constituting the NVU; pericytes may organize CBF recovery, macrophage-mediated clearance of myelin debris, intrainfarct fibrosis, and periinfarct astrogliosis and remyelination. In this review, we will discuss the physiological and pathophysiological functions of pericytes, their involvement in the molecular mechanisms underlying tissue repair and functional recovery after ischemic stroke, and a therapeutic strategy to promote endogenous regeneration.

Stem cell‐based interventions for the treatment of stroke in newborn infants

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To evaluate the benefits and harms of stem cell‐based interventions for the treatment of stroke in newborn infants compared to control (placebo or no treatment) or stem‐cell based interventions of a different type or source.

Utility of Exosomes in Ischemic and Hemorrhagic Stroke Diagnosis and Treatment

Stroke is the leading cause of death and neurological disorders worldwide. However, diagnostic techniques and treatments for stroke patients are still limited for certain types of stroke. Intensive research has been conducted so far to find suitable diagnostic techniques and treatments, but so far there has been no success. In recent years, various studies have drawn much attention to the clinical value of utilizing the mechanism of exosomes, low toxicity, biodegradability, and the ability to cross the blood–brain barrier. Recent studies have been reported on the use of biomarkers and protective and recovery effects of exosomes derived from stem cells or various cells in the diagnostic stage after stroke. This review focuses on publications describing changes in diagnostic biomarkers of exosomes following various strokes and processes for various potential applications as therapeutics.

OUP accepted manuscript

Fetal growth restriction (FGR) occurs when a fetus is unable to grow normally due to inadequate nutrient and oxygen supply from the placenta. Children born with FGR are at high risk of lifelong adverse neurodevelopmental outcomes, such as cerebral palsy, behavioral issues, and learning and attention difficulties. Unfortunately, there is no treatment to protect the FGR newborn from these adverse neurological outcomes. Chronic inflammation and vascular disruption are prevalent in the brains of FGR neonates and therefore targeted treatments may be key to neuroprotection. Tissue repair and regeneration via stem cell therapies have emerged as a potential clinical intervention for FGR babies at risk for neurological impairment and long-term disability. This review discusses the advancement of research into stem cell therapy for treating neurological diseases and how this may be extended for use in the FGR newborn. Leading preclinical studies using stem cell therapies in FGR animal models will be highlighted and the near-term steps that need to be taken for the development of future clinical trials.

Single Intraosseous Simvastatin Application Induces Endothelial Progenitor Cell Mobilization and Therapeutic Angiogenesis in a Diabetic Hindlimb Ischemia Rat Model

BACKGROUND

Endothelial progenitor cells have shown the ability to enhance neovascularization. In this study, the authors tested whether intraosseous delivery of simvastatin could mobilize endothelial progenitor cells and enhance recovery in a hindlimb ischemia model.

METHODS

There are eight groups of rats in this study: normal control; type 1 diabetes mellitus control group control without drug intervention; and type 1 diabetes mellitus rats that randomly received intraosseous simvastatin (0, 0.5, or 1 mg) or oral simvastatin administration (0, 20, or 400 mg). All type 1 diabetes mellitus rats had induced hindlimb ischemia. The number of endothelial progenitor cells in peripheral blood, and serum markers, were detected. The recovery of blood flow at 21 days after treatment was used as the main outcome.

RESULTS

The authors demonstrated that endothelial progenitor cell mobilization was increased in the simvastatin 0.5- and 1-mg groups compared with the type 1 diabetes mellitus control and simvastatin 0-mg groups at 1, 2, and 3 weeks. Serum vascular endothelial growth factor levels were significantly increased at 2 weeks in the simvastatin 0.5- and 1-mg groups, in addition to the increase of the blood flow and the gastrocnemius weight at 3 weeks. Similar increase can also been seen in simvastatin 400 mg orally but not in simvastatin 20 mg orally.

CONCLUSION

These findings demonstrate that a single intraosseous administration of simvastatin mobilized endothelial progenitor cells at a dose one-hundredth of the required daily oral dose in rats, and this potent mobilization of endothelial progenitor cells markedly improved diabetic limb ischemia by means of neovascularization.

Preparation of controlled degradation of insulin-like growth factor 1/spider silk protein nanofibrous membrane and its effect on endothelial progenitor cell viability

The present study aimed to prepare a kind of controlled-releasing insulin-like growth factor 1 (IGF-1)/spider silk protein nanofibrous membrane using a electrostatic spinning method and evaluated its effect on the cell viability of endothelial progenitor cells (EPCs). Recombinant spidroin named as GMCDRSSP-IgF-1 was electro-spun into nanofibrous membrane which can be degraded by protease and be capable of sustained-release of IGF-1. The membrane can be degraded after being treated with thrombin. The release assay results showed that IGF-1 concentration could be maintained at 20 ng/ml for a long time with treatment of Tobacco Etch Virus (TEV) protease. The viability of EPCs on GMCDRSSP-IgF-1 nanofibrous membrane was significantly increased with the presence of TEV protease. The controlled and sustained release of IGF-1 from the nanofibrous membrane could promote the adhesion and viability of EPCs. In summary, the nanofibrous membrane that exhibits controlled degradation and sustained release of IGF-1 was prepared with electrostatic spinning from genetically modified recombinant spider silk protein. The nanofibrous membrane exhibited good blood compatibility and cytocompatibility. With the presence of TEV protease, the sustained-release of IGF-1 significantly promoted the adhesion and viability of EPCs. The new nanofibrous membrane can be potentially used as a scaffold for EPCs culture in vitro and future in vivo studies.

Combination of Stem Cells and Rehabilitation Therapies for Ischemic Stroke

Stem cell transplantation with rehabilitation therapy presents an effective stroke treatment. Here, we discuss current breakthroughs in stem cell research along with rehabilitation strategies that may have a synergistic outcome when combined together after stroke. Indeed, stem cell transplantation offers a promising new approach and may add to current rehabilitation therapies. By reviewing the pathophysiology of stroke and the mechanisms by which stem cells and rehabilitation attenuate this inflammatory process, we hypothesize that a combined therapy will provide better functional outcomes for patients. Using current preclinical data, we explore the prominent types of stem cells, the existing theories for stem cell repair, rehabilitation treatments inside the brain, rehabilitation modalities outside the brain, and evidence pertaining to the benefits of combined therapy. In this review article, we assess the advantages and disadvantages of using stem cell transplantation with rehabilitation to mitigate the devastating effects of stroke.

Neovascularization and tissue regeneration by endothelial progenitor cells in ischemic stroke

Endothelial progenitor cells (EPCs) are immature endothelial cells (ECs) capable of proliferating and differentiating into mature ECs. These progenitor cells migrate from bone marrow (BM) after vascular injury to ischemic areas, where they participate in the repair of injured endothelium and new blood vessel formation. EPCs also secrete a series of protective cytokines and growth factors that support cell survival and tissue regeneration. Thus, EPCs provide novel and promising potential therapies to treat vascular disease, including ischemic stroke. However, EPCs are tightly regulated during the process of vascular repair and regeneration by numerous endogenous cytokines that are associated closely with the therapeutic efficacy of the progenitor cells. The regenerative capacity of EPCs also is affected by a range of exogenous factors and drugs as well as vascular risk factors. Understanding the functional properties of EPCs and the factors related to their regenerative capacity will facilitate better use of these progenitor cells in treating vascular disease. Here, we review the current knowledge of EPCs in cerebral neovascularization and tissue regeneration after cerebral ischemia and the factors associated with their regenerative function to better understand the underlying mechanisms and provide more effective strategies for the use of EPCs in treating ischemic stroke.

Therapeutic Potential of Cytokines in Demyelinating Lesions After Stroke

White matter damage is a component of most human stroke and usually accounts for at least half of the lesion volume. Subcortical white matter stroke (WMS) accounts for 25% of all strokes and causes severe motor and cognitive dysfunction. The adult brain has a very limited ability to repair white matter damage. Pathological analysis shows that demyelination or myelin loss is the main feature of white matter injury and plays an important role in long-term sensorimotor and cognitive dysfunction. This suggests that demyelination is a major therapeutic target for ischemic stroke injury. An acute inflammatory reaction is triggered by brain ischemia, which is accompanied by cytokine production. The production of cytokines is an important factor affecting demyelination and myelin regeneration. Different cytokines have different effects on myelin damage and myelin regeneration. Exploring the role of cytokines in demyelination and remyelination after stroke and the underlying molecular mechanisms of demyelination and myelin regeneration after ischemic injury is very important for the development of rehabilitation treatment strategies. This review focuses on recent findings on the effects of cytokines on myelin damage and remyelination as well as the progress of research on the role of cytokines in ischemic stroke prognosis to provide a new treatment approach for amelioration of white matter damage after stroke.

Cerebral angiogenesis ameliorates pathological disorders in Nemo-deficient mice with small-vessel disease

Cerebral small-vessel diseases (SVDs) often follow a progressive course. Little is known about the function of angiogenesis, which potentially induces regression of SVDs. Here, we investigated angiogenesis in a mouse model of incontinentia pigmenti (IP), a genetic disease comprising features of SVD. IP is caused by inactivating mutations of Nemo, the essential component of NF-κB signaling. When deleting Nemo in the majority of brain endothelial cells (Nemo^beKO mice), the transcriptional profile of vessels indicated cell proliferation. Brain endothelial cells expressed Ki67 and showed signs of DNA synthesis. In addition to cell proliferation, we observed sprouting and intussusceptive angiogenesis in Nemo^beKO mice. Angiogenesis occurred in all segments of the vasculature and in proximity to vessel rarefaction and tissue hypoxia. Apparently, NEMO was required for productive angiogenesis because endothelial cells that had escaped Nemo inactivation showed a higher proliferation rate than Nemo-deficient cells. Therefore, newborn endothelial cells were particularly vulnerable to ongoing recombination. When we interfered with productive angiogenesis by inducing ongoing ablation of Nemo, mice did not recover from IP manifestations but rather showed severe functional deficits. In summary, the data demonstrate that angiogenesis is present in this model of SVD and suggest that it may counterbalance the loss of vessels.

Characterization and Functional Assessment of Endothelial Progenitor Cells in Ischemic Stroke Patients

Endothelial dysfunction has been implicated in atherosclerosis, ischemic heart disease, and stroke. Endothelial progenitor cells (EPCs), found in the bone marrow and peripheral blood as rare cell population, demonstrated a high proliferation and differentiation capacity. Understanding how such diseases influence the quantity and functionality of EPCs is essential for the development of novel therapies. This study aims to investigate the factors that affect the quantity and functionality of circulating EPCs in stroke patients and healthy controls. Blood samples were collected once from healthy donors (n = 30) and up to 3 times (within 7 days (baseline), 3 and 12 months post-stroke) from stroke patients (n = 207). EPC subpopulations were isolated with flow cytometry for characterization. The Matrigel tubular formation assay was performed as a measure of functionality. An increased amount of circulating EPCs was observed in stroke patients over 45 years when compared to age-matched healthy individuals. EPCs showed a rising trend in stroke patients over the 12-month post-stroke period, reaching statistical significance at 12 months post-stroke. Isolated CD34⁺KDR⁺ cells from stroke patients showed impairment in tubular formation capability when compared to cells from healthy donors. The quantity and vasculogenic function of circulating EPCs in peripheral blood have been effectively evaluated in stroke patients and healthy control donors in this study. Age and stroke are found to be 2 influencing factors on the angiogenic capacity. It is suggested that the increase in EPC number is triggered by the recovery response following ischemic stroke.

Theta-burst transcranial magnetic stimulation promotes stroke recovery by vascular protection and neovascularization

Rationale: The integrity and function of the blood-brain barrier (BBB) is compromised after stroke. The current study was performed to examine potential beneficial effects and underlying mechanisms of repetitive transcranial magnetic stimulation (rTMS) on angiogenesis and vascular protection, function, and repair following stroke, which are largely unknown.

Methods: Using a rat photothrombotic (PT) stroke model, continuous theta-burst rTMS was administered once daily to the infarcted hemisphere for 5 min, beginning 3 h after PT stroke. This treatment was applied for 6 days. BBB integrity, blood flow, vascular associated proteins, angiogenesis, integrity of neuronal morphology and structure, and behavioral outcome were measured and analyzed at 6 and/or 22 days after PT stroke.

Results: We report that rTMS significantly mitigated BBB permeabilization and preserved important BBB components ZO-1, claudin-5, occludin, and caveolin-1 from PT-induced degradation. Damage to vascular structure, morphology, and perfusion was ameliorated by rTMS, resulting in improved local tissue oxygenation. This was accompanied with robust protection of critical vascular components and upregulation of regulatory factors. A complex cytokine response was induced by PT, particularly at the late phase. Application of rTMS modulated this response, ameliorating levels of cytokines related to peripheral immune cell infiltration. Further investigation revealed that rTMS promoted and sustained post-ischemic angiogenesis long-term and reduced apoptosis of newborn and existing vascular endothelial cells. Application of rTMS also inhibited PT-induced excessive astrocyte-vasculature interactions and stimulated an A1 to A2 shift in vessel-associated astrocytes. Mechanistic studies revealed that rTMS dramatically increased levels of PDGFRβ associated with A2 astrocytes and their adjacent vasculature. As well, A2 astrocytes displayed marked amplification of the angiogenesis-related factors VEGF and TGFβ. PT induced a rise in vessel-associated expression of HIF-1α that was starkly intensified by rTMS treatment. Finally, rTMS preserved neuronal morphology, synaptic structure integrity and behavioral outcome.

Conclusions: These results indicate that rTMS can exert powerful protective and restorative effects on the peri-infarct microvasculature after PT stroke by, in part, promoting HIF-1α signaling and shifting vessel-associated astrocytic polarization to the A2 phenotype. This study provides further support for the potent protective effects of rTMS in the context of ischemic stroke, and these findings implicate vascular repair and protection as an important underlying phenomenon.

Predicting in vivo therapeutic efficacy of bioorthogonally labeled endothelial progenitor cells in hind limb ischemia models via non-invasive fluorescence molecular tomography

Human embryonic stem cells-derived endothelial progenitor cells (hEPCs) were utilized as cell therapeutics for the treatment of ischemic diseases. However, in vivo tracking of hEPCs for predicting their therapeutic efficacy is very difficult. Herein, we developed bioorthogonal labeling strategy of hEPCs that could non-invasively track them after transplantation in hind limb ischemia models. First, hEPCs were treated with tetraacylated N-azidomannosamine (Ac₄ManNAz) for generating unnatural azide groups on the hEPCs surface. Second, near-infrared fluorescence (NIRF) dye, Cy5, conjugated dibenzocylooctyne (DBCO-Cy5) was chemically conjugated to the azide groups on the hEPC surface via copper-free click chemistry, resulting Cy5-hEPCs. The bioorthogonally labeled Cy5-hEPCs showed strong NIRF signal without cytotoxicity and functional perturbation in tubular formation, oxygen consumption and paracrine effect of hEPCs in vitro. In hind limb ischemia models, the distribution and migration of transplanted Cy5-hEPCs were successfully monitored via fluorescence molecular tomography (FMT) for 28 days. Notably, blood reperfusion and therapeutic neovascularization effects were significantly correlated with the initial transplantation forms of Cy5-hEPCs such as 'condensed round shape' and 'spread shape' in the ischemic lesion. The condensed transplanted Cy5-hEPCs substantially increased the therapeutic efficacy of hind limb ischemia, compared to that of spread Cy5-hEPCs. Therefore, our new stem cell labeling strategy can be used to predict therapeutic efficacy in hind limb ischemia and it can be applied a potential application in developing cell therapeutics for regenerative medicine.

Endothelial Progenitor Cells as a Marker of Vascular Damage But not a Predictor in Acute Microangiopathy-Associated Stroke

Background: The aim of the study was to assess the number of endothelial progenitor cells (EPCs) in patients with acute stroke due to cerebral microangiopathy and evaluate whether there is a relationship between their number and clinical status, radiological findings, risk factors, selected biochemical parameters, and prognosis, both in ischemic and hemorrhagic stroke. Methods: In total, 66 patients with lacunar ischemic stroke, 38 patients with typical location hemorrhagic stroke, and 22 subjects from the control group without acute cerebrovascular incidents were included in the prospective observational study. The number of EPCs was determined in serum on the first and eighth day after stroke onset using flow cytometry and identified with the immune-phenotype classification determinant (CD)45−, CD34+, CD133+. Results: We demonstrated a significantly higher number of EPCs on the first day of stroke compared to the control group (med. 17.75 cells/µL (0–488 cells/µL) vs. 5.24 cells/µL (0–95 cells/µL); p = 0.0006). We did not find a relationship between the number of EPCs in the acute phase of stroke and the biochemical parameters, vascular risk factors, or clinical condition. In females, the higher number of EPCs on the first day of stroke is related to a favorable functional outcome on the eighth day after the stroke onset compared to males (p = 0.0355). We found that a higher volume of the hemorrhagic focus on the first day was correlated with a lower number of EPCs on the first day (correlation coefficient (R) = −0.3378, p = 0.0471), and a higher number of EPCs on the first day of the hemorrhagic stroke was correlated with a lower degree of regression of the hemorrhagic focus (R = −0.3896, p = 0.0367). Conclusion: The study showed that endothelial progenitor cells are an early marker in acute microangiopathy-associated stroke regardless of etiology and may affect the radiological findings in hemorrhagic stroke. Nevertheless, their prognostic value remains doubtful in stroke patients.

microRNA-381-3p Confers Protection Against Ischemic Stroke Through Promoting Angiogenesis and Inhibiting Inflammation by Suppressing Cebpb and Map3k8

Ischemic stroke is a serious disease with limited prevention methods, and various genes and microRNAs (miRNAs) have been found to be dysregulated in the pathogenesis of this disease. This study aims to explore the potential role of miR-381-3p in ischemic stroke, along with its underlying mechanism. A mouse model of ischemic stroke was developed using middle cerebral artery occlusion. Next, the expression of mitogen-activated protein kinase kinase kinase 8 (Map3k8) and CCAAT enhancer binding protein beta (Cebpb) was determined by RT-qPCR. Gain- and loss-of-function approaches were applied to analyze the effects of miR-381-3p, Cebpb and Map3k8 on the biological functions of endothelial progenitor cells (EPCs) with the involvement of the tumor necrosis factor-α (TNF-α) signaling pathway. In addition, dual luciferase reporter gene assay was performed for the analysis of the relationship among miR-381-3p, Map3k8 and Cebpb. Further, rescue experiment was performed with the help of JNK/p38 specific agonist, Anisomycin. Map3k8 and Cebpb were highly expressed in ischemic stroke. Loss-of-function of Map3k8 or Cebpb in EPCs contributed to accelerated proliferation, migration and angiogenesis of EPCs. Next, miR-381-3p downregulated the expression of its two target genes, Map3k8 and Cebpb. miR-381-3p overexpression promoted angiogenesis of EPCs, and inhibited inflammation, which could be reversed by restoration of Map3k8 or Cebpb. Additionally, silencing Map3k8 or Cebpb inhibited the activation of TNF-α signaling pathway. Furthermore, Anisomycin treatment could enhance inflammation and inhibit angiogenesis. Taken together, miR-381-3p downregulates Map3k8 and Cebpb to protect against ischemic stroke, broadening our understanding of the pathogenesis of ischemic stroke.

Clonal isolation of endothelial colony-forming cells from early gestation chorionic villi of human placenta for fetal tissue regeneration

BACKGROUND

Endothelial colony-forming cells (ECFCs) have been implicated in the process of vascularization, which includes vasculogenesis and angiogenesis. Vasculogenesis is a de novo formation of blood vessels, and is an essential physiological process that occurs during embryonic development and tissue regeneration. Angiogenesis is the growth of new capillaries from pre-existing blood vessels, which is observed both prenatally and postnatally. The placenta is an organ composed of a variety of fetal-derived cells, including ECFCs, and therefore has significant potential as a source of fetal ECFCs for tissue engineering.

AIM

To investigate the possibility of isolating clonal ECFCs from human early gestation chorionic villi (CV-ECFCs) of the placenta, and assess their potential for tissue engineering.

METHODS

The early gestation chorionic villus tissue was dissociated by enzyme digestion. Cells expressing CD31 were selected using magnetic-activated cell sorting, and plated in endothelial-specific growth medium. After 2-3 wks in culture, colonies displaying cobblestone-like morphology were manually picked using cloning cylinders. We characterized CV-ECFCs by flow cytometry, immunophenotyping, tube formation assay, and Dil-Ac-LDL uptake assay. Viral transduction of CV-ECFCs was performed using a Luciferase/tdTomato-containing lentiviral vector, and transduction efficiency was tested by fluorescent microscopy and flow cytometry. Compatibility of CV-ECFCs with a delivery vehicle was determined using an FDA approved, small intestinal submucosa extracellular matrix scaffold.

RESULTS

After four passages in 6-8 wks of culture, we obtained a total number of 1.8 × 10⁷ CV-ECFCs using 100 mg of early gestational chorionic villus tissue. Immunophenotypic analyses by flow cytometry demonstrated that CV-ECFCs highly expressed the endothelial markers CD31, CD144, CD146, CD105, CD309, only partially expressed CD34, and did not express CD45 and CD90. CV-ECFCs were capable of acetylated low-density lipoprotein uptake and tube formation, similar to cord blood-derived ECFCs (CB-ECFCs). CV-ECFCs can be transduced with a Luciferase/tdTomato-containing lentiviral vector at a transduction efficiency of 85.1%. Seeding CV-ECFCs on a small intestinal submucosa extracellular matrix scaffold confirmed that CV-ECFCs were compatible with the biomaterial scaffold.

CONCLUSION

In summary, we established a magnetic sorting-assisted clonal isolation approach to derive CV-ECFCs. A substantial number of CV-ECFCs can be obtained within a short time frame, representing a promising novel source of ECFCs for fetal treatments.

Dietary Supplemental Glutamine Enhances the Percentage of Circulating Endothelial Progenitor Cells in Mice with High-Fat Diet-Induced Obesity Subjected to Hind Limb Ischemia

This study investigated whether glutamine (GLN) pretreatment can enhance circulating endothelial progenitor cells (EPCs) and attenuate inflammatory reaction in high-fat diet-induced obese mice with limb ischemia. Mice were assigned to a normal control (NC), high-fat control (HC), limb ischemia (HI), and GLN limb ischemia (HG) groups. The NC group provided chow diet and treated as a negative control. Mice in the HC and HI groups were fed a high-fat diet which 60% energy provided by fat for 8 weeks. Mice in the HG group were fed the same diet for 4 weeks and then transferred to a high-fat diet with 25% of total protein nitrogen provided as GLN to replace part of the casein for the subsequent 4 weeks. After feeding 8 weeks, mice in the HC group were sham-operated, while the HI and HG groups underwent an operation to induce limb ischemia. All mice except the NC group were euthanized on either day 1 or 7 after the operation. The results showed that the 8 weeks' high-fat diet feeding resulted in obesity. The HG group had higher circulating EPCs on day 1 while muscle vascular endothelial growth factor, matrix metalloproteinase-9, and hypoxia-inducible factor-1 gene expressions were higher on day 7 postischemia than those of the HI group. The superoxide dismutase activity and reduced glutathione content in affected muscles were higher, whereas mRNA expressions of interleukin-6 and tumor necrosis factor-α were lower in the HG than those in the HI group. These findings suggest that obese mice pretreated with GLN-supplemented high-fat diet increased circulating EPC percentage, enhanced the antioxidant capacity, and attenuated inflammatory reactions in response to limb ischemia.

Anti-inflammatory cytokines IL-35 and IL-10 block atherogenic lysophosphatidylcholine-induced, mitochondrial ROS-mediated innate immune activation, but spare innate immune memory signature in endothelial cells

It has been shown that anti-inflammatory cytokines interleukin-35 (IL-35) and IL-10 could inhibit acute endothelial cell (EC) activation, however, it remains unknown if and by what pathways IL-35 and IL-10 could block atherogenic lipid lysophosphatidylcholine (LPC)-induced sustained EC activation; and if mitochondrial reactive oxygen species (mtROS) can differentiate mediation of EC activation from trained immunity (innate immune memory). Using RNA sequencing analyses, biochemical assays, as well as database mining approaches, we compared the effects of IL-35 and IL-10 in LPC-treated human aortic ECs (HAECs). Principal component analysis revealed that both IL-35 and IL-10 could similarly and partially reverse global transcriptome changes induced by LPC. Gene set enrichment analyses showed that while IL-35 and IL-10 could both block acute EC activation, characterized by upregulation of cytokines/chemokines and adhesion molecules, IL-35 is more potent than IL-10 in suppressing innate immune signatures upregulated by LPC. Surprisingly, LPC did not induce the expression of trained tolerance itaconate pathway enzymes but induced trained immunity enzyme expressions; and neither IL-35 nor IL-10 was found to affect LPC-induced trained immunity gene signatures. Mechanistically, IL-35 and IL-10 could suppress mtROS, which partially mediate LPC-induced EC activation and innate immune response. Therefore, anti-inflammatory cytokines could reverse mtROS-mediated acute and innate immune trans-differentiation responses in HAECs, but it could spare metabolic reprogramming and trained immunity signatures, which may not fully depend on mtROS. Our characterizations of anti-inflammatory cytokines in blocking mtROS-mediated acute and prolonged EC activation, and sparing trained immunity are significant for designing novel strategies for treating cardiovascular diseases, other inflammatory diseases, and cancers.

Critical limb ischemia: Current and novel therapeutic strategies

Critical limb ischemia (CLI) is the advanced stage of peripheral artery disease spectrum and is defined by limb pain or impending limb loss because of compromised blood flow to the affected extremity. Current conventional therapies for CLI include amputation, bypass surgery, endovascular therapy, and pharmacological approaches. Although these conventional therapeutic strategies still remain as the mainstay of treatments for CLI, novel and promising therapeutic approaches such as proangiogenic gene/protein therapies and stem cell-based therapies have emerged to overcome, at least partially, the limitations and disadvantages of current conventional therapeutic approaches. Such novel CLI treatment options may become even more effective when other complementary approaches such as utilizing proper bioscaffolds are used to increase the survival and engraftment of delivered genes and stem cells. Therefore, herein, we address the benefits and disadvantages of current therapeutic strategies for CLI treatment and summarize the novel and promising therapeutic approaches for CLI treatment. Our analyses also suggest that these novel CLI therapeutic strategies show considerable advantages to be used when current conventional methods have failed for CLI treatment.

Modern Concepts in Regenerative Therapy for Ischemic Stroke: From Stem Cells for Promoting Angiogenesis to 3D-Bioprinted Scaffolds Customized via Carotid Shear Stress Analysis

Ischemic stroke is associated with a tremendous economic and societal burden, and only a few therapies are currently available for the treatment of this devastating disease. The main therapeutic approaches used nowadays for the treatment of ischemic brain injury aim to achieve reperfusion, neuroprotection and neurorecovery. Therapeutic angiogenesis also seems to represent a promising tool to improve the prognosis of cerebral ischemia. This review aims to present the modern concepts and the current status of regenerative therapy for ischemic stroke and discuss the main results of major clinical trials addressing the effectiveness of stem cell therapy for achieving neuroregeneration in ischemic stroke. At the same time, as a glimpse into the future, this article describes modern concepts for stroke prevention, such as the implantation of bioprinted scaffolds seeded with stem cells, whose 3D geometry is customized according to carotid shear stress.

Concise Review: Stem Cell Therapy for Stroke Patients: Are We There Yet?

Four decades of preclinical research demonstrating survival, functional integration, and behavioral effects of transplanted stem cells in experimental stroke models have provided ample scientific basis for initiating limited clinical trials of stem cell therapy in stroke patients. Although safety of the grafted cells has been overwhelmingly documented, efficacy has not been forthcoming. Two recently concluded stroke clinical trials on mesenchymal stem cells (MSCs) highlight the importance of strict adherence to the basic science findings of optimal transplant regimen of cell dose, timing, and route of delivery in enhancing the functional outcomes of cell therapy. Echoing the Stem Cell Therapeutics as an Emerging Paradigm for Stroke and Stroke Treatment Academic Industry Roundtable call for an NIH‐guided collaborative consortium of multiple laboratories in testing the safety and efficacy of stem cells and their derivatives, not just as stand‐alone but preferably in combination with approved thrombolytic or thrombectomy, may further increase the likelihood of successful fruition of translating stem cell therapy for stroke clinical application. The laboratory and clinical experience with MSC therapy for stroke may guide the future translational research on stem cell‐based regenerative medicine in neurological disorders. stem cells translational medicine2019;8:983&988

Silica-coated magnetic nanoparticles labeled endothelial progenitor cells alleviate ischemic myocardial injury and improve long-term cardiac function with magnetic field guidance in rats with myocardial infarction

Low retention of endothelial progenitor cells (EPCs) in the infarct area has been suggested to be responsible for the poor clinical efficacy of EPC therapy for myocardial infarction (MI). This study aimed to evaluate whether magnetized EPCs guided through an external magnetic field could augment the aggregation of EPCs in an ischemia area, thereby enhancing therapeutic efficacy. EPCs from male rats were isolated and labeled with silica‐coated magnetic iron oxide nanoparticles to form magnetized EPCs. Then, the proliferation, migration, vascularization, and cytophenotypic markers of magnetized EPCs were analyzed. Afterward, the magnetized EPCs (1 × 10⁶) were transplanted into a female rat model of MI via the tail vein at 7 days after MI with or without the guidance of an external magnet above the infarct area. Cardiac function, myocardial fibrosis, and the apoptosis of cardiomyocytes were observed at 4 weeks after treatment. In addition, EPC retention and the angiogenesis of ischemic myocardium were evaluated. Labeling with magnetic nanoparticles exhibited minimal influence to the biological functions of EPCs. The transplantation of magnetized EPCs guided by an external magnet significantly improved the cardiac function, decreased infarction size, and reduced myocardial apoptosis in MI rats. Moreover, enhanced aggregations of magnetized EPCs in the infarcted border zone were observed in rats with external magnet‐guided transplantation, accompanied by the significantly increased density of microvessels and upregulated the expression of proangiogenic factors, when compared with non‐external‐magnet‐guided rats. The magnetic field‐guided transplantation of magnetized EPCs was associated with the enhanced aggregation of EPCs in the infarcted border zone, thereby improving the therapeutic efficacy of MI.

Astrocytes-derived VEGF exacerbates the microvascular damage of late delayed RBI

Overexpression of vascular endothelial growth factor (VEGF) is considered the most critical factor in radiation-induced brain injury (RBI). To investigate the role of VEGF and the mechanism underlying microvascular damage in RBI, wild type mice, and transgenic mice overexpressing VEGF derived from astrocytes, were separately and randomly exposed to whole-brain or sham irradiation. Pathophysiologic changes in the brain tissue were detected 90 days after irradiation. Compared with wild type mice, the secretion of VEGF and angiopoietin-2 (Ang-2) was up-regulated in transgenic mice, whether irradiated or not, while elevated expression of VEGF, Ang-2, and glial fibrillary acidic protein (GFAP) was detected after whole-brain irradiation using western blotting. Impairment of the blood-brain barrier (BBB) was demonstrated by the leakage of dyes observed using two-photon imaging and decreased expression of zonula occludens-1 (ZO-1) and Occludin. Hematoxylin-eosin (HE) staining revealed obvious structural damage in the irradiated brains. Furthermore, damage to the BBB and histopathology in the transgenic mice were worse than those of wild type mice in the irradiated groups. There was a positive correlation among VEGF and Ang-2 expression and RBI severity. These data reveal that VEGF and Ang-2 expression is closely associated with the microvascular injury in RBI. Further, overexpression of VEGF can cause up-regulation of Ang-2 and exacerbation of RBI. Therefore, Ang-2 might be the cytokine that acts as a mediator between VEGF and microvascular injury, and is likely a new intervention target for RBI.

Co-signaling receptors regulate T-cell plasticity and immune tolerance

We took an experimental database mining analysis to determine the expression of 28 co-signaling receptors in 32 human tissues in physiological/pathological conditions. We made the following significant findings: 1) co-signaling receptors are differentially expressed in tissues; 2) heart, trachea, kidney, mammary gland and muscle express co-signaling receptors that mediate CD4⁺T cell functions such as priming, differentiation, effector, and memory; 3) urinary tumor, germ cell tumor, leukemia and chondrosarcoma express high levels of co-signaling receptors for T cell activation; 4) expression of inflammasome components are correlated with the expression of co-signaling receptors; 5) CD40, SLAM, CD80 are differentially expressed in leukocytes from patients with trauma, bacterial infections, polarized macrophages and in activated endothelial cells; 6) forward and reverse signaling of 50% co-inhibition receptors are upregulated in endothelial cells during inflammation; and 7) STAT1 deficiency in T cells upregulates MHC class II and co-stimulation receptors. Our results have provided novel insights into co-signaling receptors as physiological regulators and potentiate identification of new therapeutic targets for the treatment of sterile inflammatory disorders.

Safety and Optimization of Metabolic Labeling of Endothelial Progenitor Cells for Tracking

Metabolic labeling is one of the most powerful methods to label the live cell for in vitro and in vivo tracking. However, the cellular mechanisms by modified glycosylation due to metabolic agents are not fully understood. Therefore, metabolic labeling has not yet been widely used in EPC tracking and labeling. In this study, cell functional properties such as proliferation, migration and permeability and gene expression patterns of metabolic labeling agent-treated hUCB-EPCs were analyzed to demonstrate cellular effects of metabolic labeling agents. As the results, 10 μM Ac4ManNAz treatment had no effects on cellular function or gene regulations, however, higher concentration of Ac4ManNAz (>20 μM) led to the inhibition of functional properties (proliferation rate, viability and rate of endocytosis) and down-regulation of genes related to cell adhesion, PI3K/AKT, FGF and EGFR signaling pathways. Interestingly, the new blood vessel formation and angiogenic potential of hUCB-EPCs were not affected by Ac4ManNAz concentration. Based on our results, we suggest 10 μM as the optimal concentration of Ac4ManNAz for in vivo hUCB-EPC labeling and tracking. Additionally, we expect that our approach can be used for understanding the efficacy and safety of stem cell-based therapy in vivo.

Autologous Endothelial Progenitor Cells Transplantation for Acute Ischemic Stroke: A 4-Year Follow-Up Study

Transplantation of endothelial progenitor cells (EPCs) is a proven safe and effective method for treatment of cerebral ischemia in animal experiments. However, safety and efficacy need to be determined in clinical trials. We performed a two‐center, randomized, placebo‐controlled phase I/IIa trial with blinded outcome assessment on 18 patients with acute cerebral infarct within the middle cerebral artery territory, and followed for up to 4 years. Autologous ex vivo expanded EPCs were injected intravenously in the EPC group, and patients who received saline or autologous bone marrow stromal cells served as control groups. Mortality of any cause, adverse events, and new‐onset comorbidities were monitored. Changes in neurological deficits were assessed at different time points. We found no toxicity events or infusional or allergic reactions in any treated group. Three patients in the placebo group died during the 4‐year follow‐up. We found that the EPC group had fewer serious adverse events compared with the placebo‐controlled group, although there were no statistical differences in mortality among the three groups. Furthermore, there was no significant difference in neurological or functional improvement observed among the three groups, except for the Scandinavia Stroke Scale score at 3 months between the EPC group and placebo‐controlled group. Autologous transplantation of EPCs appears to improve long‐term safety in acute cerebral infarct patients, supporting the feasibility of this novel method for treatment of ischemic stroke (ClinicalTrials.gov: NCT01468064). Stem Cells Translational Medicine2019;8:14–21

Revascularization and endothelial progenitor cells in stroke

Stroke is one of the leading causes of death and disability worldwide. Tremendous improvements have been achieved in the acute care of stroke patients with the implementation of stroke units, thrombolytic drugs, and endovascular trombectomies. However, stroke survivors with neurological deficits require long periods of neurorehabilitation, which is the only approved therapy for poststroke recovery. With this scenario, more treatments are urgently needed, and only the understanding of the mechanisms of brain recovery might contribute to identify new therapeutic agents. Fortunately, brain injury after stroke is counteracted by the birth and migration of several populations of progenitor cells towards the injured areas, where angiogenesis and vascular remodeling play a key role providing trophic support and guidance during neurorepair. Endothelial progenitor cells (EPCs) constitute a pool of circulating bone-marrow derived cells that mobilize after an ischemic injury with the potential to incorporate into the damaged endothelium, to form new vessels, or to secrete trophic factors stimulating vessel remodeling. The circulating levels of EPCs are altered after stroke, and several subpopulations have proved to boost brain neurorepair in preclinical models of cerebral ischemia. The goal of this review is to discuss the current state of the neuroreparative actions of EPCs, focusing on their paracrine signaling mechanisms thorough their secretome and released extracellular vesicles.

Lysophospholipids induce innate immune transdifferentiation of endothelial cells, resulting in prolonged endothelial activation

Innate immune cells express danger-associated molecular pattern (DAMP) receptors, T-cell costimulation/coinhibition receptors, and major histocompatibility complex II (MHC-II). We have recently proposed that endothelial cells can serve as innate immune cells, but the molecular mechanisms involved still await discovery. Here, we investigated whether human aortic endothelial cells (HAECs) could be transdifferentiated into innate immune cells by exposing them to hyperlipidemia-up-regulated DAMP molecules, i.e. lysophospholipids. Performing RNA-seq analysis of lysophospholipid-treated HAECs, we found that lysophosphatidylcholine (LPC) and lysophosphatidylinositol (LPI) regulate largely distinct gene programs as revealed by principal component analysis. Metabolically, LPC up-regulated genes that are involved in cholesterol biosynthesis, presumably through sterol regulatory element-binding protein 2 (SREBP2). By contrast, LPI up-regulated gene transcripts critical for the metabolism of glucose, lipids, and amino acids. Of note, we found that LPC and LPI both induce adhesion molecules, cytokines, and chemokines, which are all classic markers of endothelial cell activation, in HAECs. Moreover, LPC and LPI shared the ability to transdifferentiate HAECs into innate immune cells, including induction of potent DAMP receptors, such as CD36 molecule, T-cell costimulation/coinhibition receptors, and MHC-II proteins. The induction of these innate-immunity signatures by lysophospholipids correlated with their ability to induce up-regulation of cytosolic calcium and mitochondrial reactive oxygen species. In conclusion, lysophospholipids such as LPC and LPI induce innate immune cell transdifferentiation in HAECs. The concept of prolonged endothelial activation, discovered here, is relevant for designing new strategies for managing cardiovascular diseases.

Effects of Angiotensin-Converting Enzyme Inhibition on Circulating Endothelial Progenitor Cells in Patients with Acute Ischemic Stroke

Background

Therapeutic neovascularization might represent an important strategy to salvage tissue after ischemia. Circulating bone marrow-derived endothelial progenitor cells (EPCs) were previously shown to augment the neovascularization of ischemic tissue. Angiotensin-converting enzyme inhibitors (ACEIs) might modulate EPC mobilization. We evaluated populations of circulating stem cells and early EPCs in acute ischemic stroke (AIS) patients and the effect of ACEI on circulating EPCs in these patients with respect to aspects of stroke pathogenesis.

Methods

We studied 43 AIS patients (group I), comprising 33 treated with ACEI (group Ia) and 10 untreated (group Ib). Risk factor controls (group II) included 22 subjects. EPCs were measured by flow cytometry.

Results

In AIS patients, the number of circulating stem cells and early EPCs upon admission was similar to that in control group individuals. There were no significant differences in the numbers of stem cells and early EPCs over subsequent days after AIS. There were also no significant differences in stem cell and early EPC numbers over the first 3 days between group Ia and group Ib. However, on day 7, these numbers were significantly higher in group Ib than in group Ia (p < 0.05). In AIS patients chronically treated with ACEI, there was a negative correlation between CD133⁺ cell number and neurological deficit on the first, third, and seventh days (p < 0.005).

Conclusions

An increased number of circulating stem cells and early EPCs were not observed in stroke patients chronically treated with ACEI. In patients chronically treated with ACEI, a significant correlation was observed between decreased neurological deficit and higher levels of CD133⁺ cells; this could be due to the positive influence of these cells on the regeneration of the endothelium and improved circulation in the ischemic penumbra.

Circulating CD34+ and CD34+VEGFR2+ progenitor cells are associated with KLOTHO KL-VS polymorphism

BACKGROUND

KLOTHO is a regulator of endothelial cells activity and integrity. It has been described for the first time because of its anti-aging properties. KLOTHO encoding gene is present in many functional variants in humans, including "KL-VS" variant that has been connected with longevity and cardiovascular disease development. Few mechanisms have been proposed to explain these associations, but none of them focused on cells from CD34+ population. The aim of our study was to investigate influence of KLOTHO KL-VS polymorphism on populations of CD34+ and CD34+VEGFR2+ cells.

METHODS AND RESULTS

We examined 167 Polish subjects from Pomeranian region. The analysis concerned KL-VS polymorphism, flow cytometry evaluation of whole blood cells and determination of endothelium-associated serum/plasma factors. Our results indicate that individuals possessing at least one KL-VS allele are characterized by greater number of CD34+ and CD34+VEGFR2+ and their various subpopulations (CD34+CD133+, CD34+c-Kit+, CD34+CXCR4+ and CD34+VEGFR2+c-Kit+) than wild-type volunteers. This group also exhibited more favorable lipid profile and statistically insignificant decrease of vWF and angiotensin II in their blood, whereas VEGF levels were elevated.

CONCLUSION

One of the mechanisms that are responsible for previously described KL-VS heterozygote advantage may be connected with maintaining greater size of hematopoietic and endothelial progenitor cells population.

Blood-brain barrier-supported neurogenesis in healthy and diseased brain

Adult neurogenesis is one of the most important mechanisms contributing to brain development, learning, and memory. Alterations in neurogenesis underlie a wide spectrum of brain diseases. Neurogenesis takes place in highly specialized neurogenic niches. The concept of neurogenic niches is becoming widely accepted due to growing evidence of the important role of the microenvironment established in the close vicinity to stem cells in order to provide adequate control of cell proliferation, differentiation, and apoptosis. Neurogenic niches represent the platform for tight integration of neurogenesis and angiogenesis supported by specific properties of cerebral microvessel endothelial cells contributing to establishment of partially compromised blood-brain barrier (BBB) for the adjustment of local conditions to the current metabolic needs of stem and progenitor cells. Here, we review up-to-date data on microvascular dynamics in activity-dependent neurogenesis, specific properties of BBB in neurogenic niches, endothelial-driven mechanisms of clonogenic activity, and future perspectives for reconstructing the neurogenic niches in vitro.

IL-35 (Interleukin-35) Suppresses Endothelial Cell Activation by Inhibiting Mitochondrial Reactive Oxygen Species-Mediated Site-Specific Acetylation of H3K14 (Histone 3 Lysine 14)

OBJECTIVE

IL-35 (interleukin-35) is an anti-inflammatory cytokine, which inhibits immune responses by inducing regulatory T cells and regulatory B cells and suppressing effector T cells and macrophages. It remains unknown whether atherogenic stimuli induce IL-35 and whether IL-35 inhibits atherogenic lipid-induced endothelial cell (EC) activation and atherosclerosis. EC activation induced by hyperlipidemia stimuli, including lysophosphatidylcholine is considered as an initiation step for monocyte recruitment and atherosclerosis. In this study, we examined the expression of IL-35 during early atherosclerosis and the roles and mechanisms of IL-35 in suppressing lysophosphatidylcholine-induced EC activation.

APPROACH AND RESULTS

Using microarray and ELISA, we found that IL-35 and its receptor are significantly induced during early atherosclerosis in the aortas and plasma of ApoE (apolipoprotein E) knockout mice-an atherosclerotic mouse model-and in the plasma of hypercholesterolemic patients. In addition, we found that IL-35 suppresses lysophosphatidylcholine-induced monocyte adhesion to human aortic ECs. Furthermore, our RNA-sequencing analysis shows that IL-35 selectively inhibits lysophosphatidylcholine-induced EC activation-related genes, such as ICAM-1 (intercellular adhesion molecule-1). Mechanistically, using flow cytometry, mass spectrometry, electron spin resonance analyses, and chromatin immunoprecipitation-sequencing analyses, we found that IL-35 blocks lysophosphatidylcholine-induced mitochondrial reactive oxygen species, which are required for the induction of site-specific H3K14 (histone 3 lysine 14) acetylation, increased binding of proinflammatory transcription factor AP-1 in the promoter of ICAM-1, and induction of ICAM-1 transcription in human aortic EC. Finally, IL-35 cytokine therapy suppresses atherosclerotic lesion development in ApoE knockout mice.

CONCLUSIONS

IL-35 is induced during atherosclerosis development and inhibits mitochondrial reactive oxygen species-H3K14 acetylation-AP-1-mediated EC activation.

Genetically‑modified stem cells in treatment of human diseases: Tissue kallikrein (KLK1)‑based targeted therapy (Review)

The tissue kallikrein-kinin system (KKS) is an endogenous multiprotein metabolic cascade which is implicated in the homeostasis of the cardiovascular, renal and central nervous system. Human tissue kallikrein (KLK1) is a serine protease, component of the KKS that has been demonstrated to exert pleiotropic beneficial effects in protection from tissue injury through its anti-inflammatory, anti-apoptotic, anti-fibrotic and anti-oxidative actions. Mesenchymal stem cells (MSCs) or endothelial progenitor cells (EPCs) constitute populations of well-characterized, readily obtainable multipotent cells with special immunomodulatory, migratory and paracrine properties rendering them appealing potential therapeutics in experimental animal models of various diseases. Genetic modification enhances their inherent properties. MSCs or EPCs are competent cellular vehicles for drug and/or gene delivery in the targeted treatment of diseases. KLK1 gene delivery using adenoviral vectors or KLK1 protein infusion into injured tissues of animal models has provided particularly encouraging results in attenuating or reversing myocardial, renal and cerebrovascular ischemic phenotype and tissue damage, thus paving the way for the administration of genetically modified MSCs or EPCs with the human tissue KLK1 gene. Engraftment of KLK1-modified MSCs and/or KLK1-modified EPCs resulted in advanced beneficial outcome regarding heart and kidney protection and recovery from ischemic insults. Collectively, findings from pre-clinical studies raise the possibility that tissue KLK1 may be a novel future therapeutic target in the treatment of a wide range of cardiovascular, cerebrovascular and renal disorders.

Homocysteine inhibits endothelial progenitor cells proliferation via DNMT1-mediated hypomethylation of Cyclin A

Endothelial progenitor cells (EPCs) contribute to neovasculogenesis and reendothelialization of damaged blood vessels to maintain the endothelium. Dysfunction of EPCs is implicated in the pathogenesis of vascular injury induced by homocysteine (Hcy). We aimed to investigate the role of Cyclin A in Hcy-induced EPCs dysfunction and explore its molecular mechanism. In this study, by treatment of EPCs with Hcy, we found that the expression of Cyclin A mRNA and protein were significantly downregulated in a dose-dependent manner. Knockdown of Cyclin A prominently reduced proliferation of EPCs, while over-expression of Cyclin A significantly promoted the cell proliferation, suggesting that Hcy inhibits EPCs proliferation through downregulation of Cyclin A expression. In addition, epigenetic study also demonstrated that Hcy induces DNA hypomethylation of the Cyclin A promoter in EPCs through downregulated expression of DNMT1. Moreover, we found that Hcy treatment of EPCs leads to increased SAM, SAH and MeCP2, while the ratio of SAM/SAH and MBD expression decrease. In summary, our results indicate that Hcy inhibits Cyclin A expression through hypomethylation of Cyclin A and thereby suppress EPCs proliferation. These findings demonstrate a novel mechanism of DNA methylation mediated by DNMT1 in prevention of Hcy associated cardiovascular disease.

A comprehensive data mining study shows that most nuclear receptors act as newly proposed homeostasis-associated molecular pattern receptors

Background

Nuclear receptors (NRs) can regulate gene expression; therefore, they are classified as transcription factors. Despite the extensive research carried out on NRs, still several issues including (1) the expression profile of NRs in human tissues, (2) how the NR expression is modulated during atherosclerosis and metabolic diseases, and (3) the overview of the role of NRs in inflammatory conditions are not fully understood.

Methods

To determine whether and how the expression of NRs are regulated in physiological/pathological conditions, we took an experimental database analysis to determine expression of all 48 known NRs in 21 human and 17 murine tissues as well as in pathological conditions.

Results

We made the following significant findings: (1) NRs are differentially expressed in tissues, which may be under regulation by oxygen sensors, angiogenesis pathway, stem cell master regulators, inflammasomes, and tissue hypo-/hypermethylation indexes; (2) NR sequence mutations are associated with increased risks for development of cancers and metabolic, cardiovascular, and autoimmune diseases; (3) NRs have less tendency to be upregulated than downregulated in cancers, and autoimmune and metabolic diseases, which may be regulated by inflammation pathways and mitochondrial energy enzymes; and (4) the innate immune sensor inflammasome/caspase-1 pathway regulates the expression of most NRs.

Conclusions

Based on our findings, we propose a new paradigm that most nuclear receptors are anti-inflammatory homeostasis-associated molecular pattern receptors (HAMPRs). Our results have provided a novel insight on NRs as therapeutic targets in metabolic diseases, inflammations, and malignancies.

Electronic supplementary material

The online version of this article (10.1186/s13045-017-0526-8) contains supplementary material, which is available to authorized users.

Yoder M, Majluf-Cruz A, Alvarado-Moreno JA. Reduced proliferation of endothelial colony-forming cells in unprovoked venous thromboembolic disease as a consequence of endothelial dysfunction

BACKGROUND

Venous thromboembolic disease (VTD) is a public health problem. We recently reported that endothelial colony-forming cells (ECFCs) derived from endothelial cells (EC) (ECFC-ECs) from patients with VTD have a dysfunctional state. For this study, we proposed that a dysfunctional status of these cells generates a reduction of its proliferative ability, which is also associated with senescence and reactive oxygen species (ROS).

METHODS AND RESULTS

Human mononuclear cells (MNCs) were obtained from peripheral blood from 40 healthy human volunteers (controls) and 50 patients with VTD matched by age (20-50 years) and sex to obtain ECFCs. We assayed their proliferative ability with plasma of patients and controls and supernatants of cultures from ECFC-ECs, senescence-associated β-galactosidase (SA-β-gal), ROS, and expression of ephrin-B2/Eph-B4 receptor. Compared with cells from controls, cells from VTD patients showed an 8-fold increase of ECFCs that emerged 1 week earlier, reduced proliferation at long term (39%) and, in passages 4 and 10, a highly senescent rate (30±1.05% vs. 91.3±15.07%, respectively) with an increase of ROS and impaired expression of ephrin-B2/Eph-4 genes. Proliferation potential of cells from VTD patients was reduced in endothelial medium [1.4±0.22 doubling population (DP)], control plasma (1.18±0.31 DP), or plasma from VTD patients (1.65±0.27 DP).

CONCLUSIONS

As compared with controls, ECFC-ECs from individuals with VTD have higher oxidative stress, proliferation stress, cellular senescence, and low proliferative potential. These findings suggest that patients with a history of VTD are ECFC-ECs dysfunctional that could be associated to permanent risk for new thrombotic events.

Endothelial Progenitor Cells for Ischemic Stroke: Update on Basic Research and Application

Ischemic stroke is one of the leading causes of human death and disability worldwide. So far, ultra-early thrombolytic therapy is the most effective treatment. However, most patients still live with varying degrees of neurological dysfunction due to its narrow therapeutic time window. It has been confirmed in many studies that endothelial progenitor cells (EPCs), as a kind of adult stem cells, can protect the neurovascular unit by repairing the vascular endothelium and its secretory function, which contribute to the recovery of neurological function after an ischemic stroke. This paper reviews the basic researches and clinical trials of EPCs especially in the field of ischemic stroke and addresses the combination of EPC application with new technologies, including neurovascular intervention, synthetic particles, cytokines, and EPC modification, with the aim of shedding some light on the application of EPCs in treating ischemic stroke in the future.

Metabolism-associated danger signal-induced immune response and reverse immune checkpoint-activated CD40+ monocyte differentiation

Adaptive immunity is critical for disease progression and modulates T cell (TC) and antigen-presenting cell (APC) functions. Three signals were initially proposed for adaptive immune activation: signal 1 antigen recognition, signal 2 co-stimulation or co-inhibition, and signal 3 cytokine stimulation. In this article, we propose to term signal 2 as an immune checkpoint, which describes interactions of paired molecules leading to stimulation (stimulatory immune checkpoint) or inhibition (inhibitory immune checkpoint) of an immune response. We classify immune checkpoint into two categories: one-way immune checkpoint for forward signaling towards TC only, and two-way immune checkpoint for both forward and reverse signaling towards TC and APC, respectively. Recently, we and others provided evidence suggesting that metabolic risk factors (RF) activate innate and adaptive immunity, involving the induction of immune checkpoint molecules. We summarize these findings and suggest a novel theory, metabolism-associated danger signal (MADS) recognition, by which metabolic RF activate innate and adaptive immunity. We emphasize that MADS activates the reverse immune checkpoint which leads to APC inflammation in innate and adaptive immunity. Our recent evidence is shown that metabolic RF, such as uremic toxin or hyperhomocysteinemia, induced immune checkpoint molecule CD40 expression in monocytes (MC) and elevated serum soluble CD40 ligand (sCD40L) resulting in CD40⁺ MC differentiation. We propose that CD40⁺ MC is a novel pro-inflammatory MC subset and a reliable biomarker for chronic kidney disease severity. We summarize that CD40:CD40L immune checkpoint can induce TC and APC activation via forward stimulatory, reverse stimulatory, and TC contact-independent immune checkpoints. Finally, we modeled metabolic RF-induced two-way stimulatory immune checkpoint amplification and discussed potential signaling pathways including AP-1, NF-κB, NFAT, STAT, and DNA methylation and their contribution to systemic and tissue inflammation.

Regulatory effects of miR-146a/b on the function of endothelial progenitor cells in acute ischemic stroke in mice

The study aims to explore how microRNA-146a/b (miR-146a/b) regulates the function of endothelial progenitor cells (EPCs) in acute ischemic stroke in mice. Eighty male SPF C57BL/6J mice were evenly divided into the model-6 h, model-12 h, model-24 h (mice suffered from middle cerebral artery occlusion [MCAO] for 6 h, 12 h and model-24 h) and normal groups. EPCs were transfected and assigned into the control, MCAO, MCAO-miR-146a, MCAO-miR-146b and MCAO-miR-146a/b groups. The qRT-PCR was used to detect miR-146a/b expression in EPCs. Expressions of tumor necrosis factor receptor-associated factor 6 (TRAF6) and interleukin-1 receptor-associated kinase 1 (IRAK1) were detected using western blotting. Cell proliferation and migration of EPCs were testified using CCK-8 assay and scratch test, respectively. Angiogenesis ability of EPCs was observed under microscope. MiR-146a and miR-146b expressions were lower in the model groups than the normal group. There were up-regulated TRAF6 and IRAK1 expressions in the model-6 h, model-12 h and model-24 h groups compared with the normal group. And there were down-regulated TRAF6 and IRAK1 expressions in the MCAO-miR-146a, MCAO-miR-146b and MCAO-miR-146a/b groups than in the MCAO group. Compared with the control group, the proliferation, migration and angiogenesis ability of EPCs were significantly lower in the MCAO group, but higher in the MCAO-miR-146a, MCAO-miR-146b and MCAO-miR-146a/b groups. Besides, the miR-146a/b group showed more enhancement than the MCAO-miR-146a and MCAO-miR-146b groups. MiR-146a/b could down-regulate the TRAF6 and IRAK1 expressions and promote proliferation, migration and angiogenesis ability of EPCs, which was important for recovery of patients with hyperacute ischemic stroke.

The Therapeutic Value of Bone Marrow-Derived Endothelial Progenitor Cell Transplantation after Intracerebral Hemorrhage in Rats

Aims

To study the effect of endothelial progenitor cell (EPC) treatment on intracerebral hemorrhage (ICH) in rats and elucidate possible mechanisms.

Methods

The rats were randomly divided into three groups: (1) EPC group: ICH + EPC, (2) phosphate-buffered saline group: ICH + PBS, and (3) sham group. EPCs were transplanted intravenously 6 h after ICH. Modified neurological severity score was used to evaluate neurological function. Blood–brain barrier (BBB) integrity was evaluated. Dead cells, inflammatory cytokines, and neuroprotective cytokines were assessed to investigate possible mechanisms.

Results

The animals in the EPC group showed significant improvement in neurological function at 48 h, 72 h, and 7 days after ICH, compared with those in the PBS group. EPC transplantation significantly reduced brain edema and the number of dead cells in the hematoma boundary areas. The intensity of Evans Blue was decreased, and expression levels of zonula occluden-1 and claudin-5 were increased in the EPC group. Proinflammatory cytokines, including interferon-γ, IL-6, and TNF-α, were decreased, whereas anti-inflammatory cytokines, including transforming growth factor-β1 and IL-10, were increased in the EPC group. In addition, expression levels of brain-derived neurotrophic factor, vascular endothelial growth factor, and neurotrophic growth factor were increased following transplantation of EPCs.

Conclusion

EPC transplantation could improve neurological function of ICH rats. The protective effect may be mediated by promotion of neuroprotective cytokine secretion, restoration of the BBB, reduction of cell death, and the decrease in inflammation.

Endothelial Progenitor Cells' Classification and Application in Neurological Diseases

The therapeutic effects of endothelial progenitor cells (EPCs) on ischemic stroke have been extensively studied in recent years. However, the differences in early EPCs and endothelial outgrowth cells (EOCs) are still unclear. Clarifications of their respective properties and specific functioning characteristics contribute to better applications of EPCs in ischemic diseases. In this review, we discuss cellular origin, isolation, culture, surface markers of early EPCs and EOCs and relevant applications in neurological diseases. We conclude that EOCs possess all characteristics of true endothelial progenitors and have potent advantages in EPC-based therapies for ischemic diseases. A number of preclinical and clinical applications of EPCs in neurological diseases are under study. More studies are needed to determine the specific characteristics of EPCs and the relevant mechanisms of EPCs for neurological diseases.