Endothelial Progenitor Cells Modulate Inflammation-Associated Stroke Vasculome

Anti-inflammatory Prowess of endothelial progenitor cells in the realm of biology and medicine

Endothelial inflammation plays a crucial role in vascular-related diseases, a leading cause of global mortality. Among various cellular players, endothelial progenitor cells (EPCs) emerge as non-differentiated endothelial cells circulating in the bloodstream. Recent evidence highlights the transformative role of EPCs in shifting from an inflammatory/immunosuppressive crisis to an anti-inflammatory/immunomodulatory response. Despite the importance of these functions, the regulatory mechanisms governing EPC activities and their physiological significance in vascular regenerative medicine remain elusive. Surprisingly, the current literature lacks a comprehensive review of EPCs' effects on inflammatory processes. This narrative review aims to fill this gap by exploring the cutting-edge role of EPCs against inflammation, from molecular intricacies to broader medical perspectives. By examining how EPCs modulate inflammatory responses, we aim to unravel their anti-inflammatory significance in vascular regenerative medicine, deepening insights into EPCs' molecular mechanisms and guiding future therapeutic strategies targeting vascular-related diseases.

Site-specific Atg13 methylation-mediated autophagy regulates epithelial inflammation in PM2.5-induced pulmonary fibrosis

Fine particulate matters (PM2.5) increased the risk of pulmonary fibrosis. However, the regulatory mechanisms of lung epithelium in pulmonary fibrosis remained elusive. Here we developed PM2.5-exposure lung epithelial cells and mice models to investigate the role of autophagy in lung epithelia mediating inflammation and pulmonary fibrosis. PM2.5 exposure induced autophagy in lung epithelial cells and then drove pulmonary fibrosis by activation of NF-κB/NLRP3 signaling pathway. PM2.5-downregulated ALKBH5 protein expression promotes m6A modification of Atg13 mRNA at site 767 in lung epithelial cells. Atg13-mediated ULK complex positively regulated autophagy and inflammation in epithelial cells with PM2.5 treatment. Knockout of ALKBH5 in mice further accelerated ULK complex-regulated autophagy, inflammation and pulmonary fibrosis. Thus, our results highlighted that site-specific m6A methylation on Atg13 mRNA regulated epithelial inflammation-driven pulmonary fibrosis in an autophagy-dependent manner upon PM2.5 exposure, and it provided target intervention strategies towards PM2.5-induced pulmonary fibrosis.

Established Immortalized Cavernous Endothelial Cells Improve Erectile Dysfunction in Rats with Cavernous Nerve Injury

The main cause of erectile dysfunction (ED) is the damage in penile cavernous endothelial cells (EC). Murine primary ECs have a limited growth potential, and the easy availability of murine ECs will facilitate the study of cavernous endothelial dysfunction in rats. This study was performed to establish immortalized rat penile cavernous ECs (rEC) and investigate how they could repair erectile dysfunction in rats with cavernous nerve injury (CNI). rEC was isolated enzymatically by collagenase digestion and were cultured. An amphotropic replication-incompetent retroviral vector encoding v-myc oncogene was used to transfect rEC for immortalization (vREC). Morphological and immunohistochemical properties of vREC were examined. Eight-week-old male Sprague-Dawley rats were divided into three groups of five rats each, including group 1 = sham operation, group 2 = bilateral CN injury, group 3 = vREC (1 × 106 cells) treatment after CNI. Erectile response was assessed at 2, 4 weeks after transplantation of vREC., Penile tissue were harvested at 4 weeks after transplantation and immune−histochemical examination was performed. vREC showed the expression of CD31, vWF, cell type-specific markers for EC by RT-PCR and flowcytometry. At 2, 4 weeks after transplantation, rats with CNI had significantly lower erectile function than control group (p < 0.05). The group transplanted with vREC showed higher erectile function than the group without vRECs (p < 0.05). vREC was established and repaired erectile dysfunction in rats with CNI. This cell line may be useful for studying mechanisms and drug screening of erectile dysfunction of rats.

Transplantation of Endothelial Progenitor Cells: Summary and prospect

Endothelial Progenitor Cells (EPCs) are precursor cells of endothelial cells (ECs), which can differentiate into vascular ECs, protect from endothelial dysfunction and tissue ischemia, and reduce vascular hyperplasia. Due to these functions, EPCs are used as a candidate cell source for transplantation strategies. In recent years, a great progress was achieved in EPCs biology research, and EPCs transplantation has become a research hotspot. At present, transplanted EPCs have been used to treat ischemic diseases due to their powerful vasculogenesis and beneficial paracrine effects. Although EPCs transplantation has been proved to play an important role, the clinical application of EPCs still faces many challenges. This review briefly summarized the basic characteristics of EPCs, the process of EPCs transplantation promoting the healing of ischemic tissue, and the ways to improve the efficiency of EPCs transplantation. In addition, the application of EPCs in neurological improvement, cardiovascular and respiratory diseases and the challenges and problems in clinical application of EPCs were also discussed. In the end, the application of EPCs transplantation in regenerative medicine and tissue engineering was discussed.

CD34 positive cells as endothelial progenitor cells in biology and medicine

CD34 is a cell surface antigen expressed in numerous stem/progenitor cells including hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPCs), which are known to be rich sources of EPCs. Therefore, regenerative therapy using CD34⁺ cells has attracted interest for application in patients with various vascular, ischemic, and inflammatory diseases. CD34⁺ cells have recently been reported to improve therapeutic angiogenesis in a variety of diseases. Mechanistically, CD34⁺ cells are involved in both direct incorporation into the expanding vasculature and paracrine activity through angiogenesis, anti-inflammatory, immunomodulatory, and anti-apoptosis/fibrosis roles, which support the developing microvasculature. Preclinical, pilot, and clinical trials have well documented a track record of safety, practicality, and validity of CD34⁺ cell therapy in various diseases. However, the clinical application of CD34⁺ cell therapy has triggered scientific debates and controversies in last decade. This review covers all preexisting scientific literature and prepares an overview of the comprehensive biology of CD34⁺ cells as well as the preclinical/clinical details of CD34⁺ cell therapy for regenerative medicine.

Improvement of erectile dysfunction using endothelial progenitor cells from fetal cerebral vasculature in the cavernous nerve injury of rats

BACKGROUND

Because of limited differentiation to endothelium from mesenchymal stem cells, it has been strongly recommended to use endothelial progenitor cells for the regeneration of the damaged endothelium of corpora cavernosa. This study was performed to investigate the immortalized human cerebral endothelial cells and their capability for repairing erectile dysfunction in a rat model of cavernous nerve injury. Circulating endothelial progenitor cells were isolated from human fetal brain vasculature at the periventricular region of telencephalic tissues. Over 95% of CD 31-positive cells were sorted and cultured for 10 days. Human cerebral endothelial progenitor cells were injected into the cavernosa of rats with cavernous nerve injury. Erectile response was then assessed. In in vivo assays, rats were divided into three groups: group 1, sham operation: group 2, bilateral cavernous nerve injury: and group 3, treatment with human cerebral endothelial cells after cavernous nerve injury.

RESULTS

Established immortalized circulating endothelial progenitor cells showed expression of human telomerase reverse transcriptase transcript by RT-PCR. They also showed the expression of vascular endothelial growth factor, von Willebrand factor, vascular endothelial growth factor receptor, and CD31, cell type-specific markers for endothelial cells by RT-PCR. In in vitro angiogenesis assays, they demonstrated tube formation that suggested morphological properties of endothelial progenitor cells. In in vivo assays, impaired erectile function of rat with cavernous nerve injury recovered at 2, 4, and 12 weeks after transplantation of human cerebral endothelial cells into the cavernosa.

CONCLUSIONS

Telomerase reverse transcriptase-circulating endothelial progenitor cells from fetal brain vasculature could repair erectile dysfunction of rats with cavernous nerve injury.

Bradykinin/bradykinin 1 receptor promotes brain microvascular endothelial cell permeability and proinflammatory cytokine release by downregulating Wnt3a

Stroke is a life-threatening disease with limited therapeutic options. Damage to the blood-brain barrier (BBB) is the key pathological feature of ischemic stroke. This study explored the role of the bradykinin (BK)/bradykinin 1 receptor (B1R) and its mechanism of action in the BBB. Human brain microvascular endothelial cells (BMECs) were used to test for cellular responses to BK by using the Cell Counting Kit-8 assay, 5-ethynyl-2'-deoxyuridine staining, enzyme-linked immunosorbent assay, flow cytometry, immunofluorescence, cellular permeability assays, and western blotting to evaluate cell viability, cytokine production, and reactive oxygen species (ROS) levels in vitro. A BBB induced by middle cerebral artery occlusion was used to evaluate BBB injuries, and the role played by BK/B1R in ischemic/reperfusion (I/R) was explored in a rat model. Results showed that BK reduced the viability of BMECs and increased the levels of proinflammatory cytokines (interleukin 6 [IL-6], IL-18, and monocyte chemoattractant protein-1) and ROS. Additionally, cellular permeability was increased by BK treatment, and the expression of tight junction proteins (claudin-5 and occludin) was decreased. Interestingly, Wnt3a expression was inhibited by BK and exogenous Wnt3a restored the effects of BK on BMECs. In an in vivo I/R rat model, knockdown of B1R significantly decreased infarct volume and inflammation in I/R rats. Our results suggest that BK might be a key inducer of BBB injury and B1R knockdown might provide a beneficial effect by upregulating Wnt3a.

Exosome in Crosstalk between Inflammation and Angiogenesis: A Potential Therapeutic Strategy for Stroke

The endothelial dysfunction, associated with inflammation and vascular permeability, remains the key event in the pathogenesis of cerebral ischemic stroke. Angiogenesis is essential for neuroprotection and neural repair following stroke. The neuroinflammatory reaction plays a vital role in stroke, and inhibition of inflammation contributes to establishing an appropriate external environment for angiogenesis. Exosomes are the heterogeneous population of extracellular vesicles which play critical roles in intercellular communication through transmitting various proteins and nucleic acids to nearby and distant recipient cells by body fluids and circulation. Recent reports have shown that exosomal therapy is a valuable and potential treatment strategy for stroke. In this review, we discussed the exosomes in complex interaction mechanisms of angiogenesis and inflammation following stroke as well as the challenges of exosomal studies such as secretion, uptake, modification, and application.

3,6'- and 1,6'-Dithiopomalidomide Mitigate Ischemic Stroke in Rats and Blunt Inflammation

(1) Background: An important concomitant of stroke is neuroinflammation. Pomalidomide, a clinically available immunomodulatory imide drug (IMiD) used in cancer therapy, lowers TNF-α generation and thus has potent anti-inflammatory actions. Well-tolerated analogs may provide a stroke treatment and allow evaluation of the role of neuroinflammation in the ischemic brain. (2) Methods: Two novel pomalidomide derivatives, 3,6'-dithiopomalidomide (3,6'-DP) and 1,6'-dithiopomalidomide (1,6'-DP), were evaluated alongside pomalidomide in a rat middle cerebral artery occlusion (MCAo) stroke model, and their anti-inflammatory actions were characterized. (3) Results: Post-MCAo administration of all drugs lowered pro-inflammatory TNF-α and IL1-β levels, and reduced stroke-induced postural asymmetry and infarct size. Whereas 3,6'- and 1,6'-DP, like pomalidomide, potently bound to cereblon in cellular studies, 3,6'-DP did not lower Ikaros, Aiolos or SALL4 levels-critical intermediates mediating the anticancer/teratogenic actions of pomalidomide and IMiDs. 3,6'-DP and 1,6'-DP lacked activity in mammalian chromosome aberration, AMES and hERG channel assays -critical FDA regulatory tests. Finally, 3,6'- and 1,6'-DP mitigated inflammation across rat primary dopaminergic neuron and microglia mixed cultures challenged with α-synuclein and mouse LPS-challenged RAW 264.7 cells. (4) Conclusion: Neuroinflammation mediated via TNF-α plays a key role in stroke outcome, and 3,6'-DP and 1,6'-DP may prove valuable as stroke therapies and thus warrant further preclinical development.

Transplantation of Fibroblast Sheets with Blood Mononuclear Cell Culture Exerts Cardioprotective Effects by Enhancing Anti-Inflammation and Vasculogenic Potential in Rat Experimental Autoimmune Myocarditis Model

Simple Summary

Fulminant myocarditis (FM) is a serious inflammatory lesion of the myocardium accompanied by cardiac dysfunction, transitioning to end-stage heart failure. Due to such a difficult pathology, a therapeutic strategy that exerts a steadfast effect has yet to be developed. Blood mononuclear cells (MNCs) have been previously shown to enhance the quality and quantity of cellular fractions (QQMNCs) with anti-inflammatory and vasculogenic potential using the one culture system. The aim of this study was to investigate whether transplantation therapy with hybrid cell sheets of fibroblasts and QQMNCs improves cardiac function in a rat model with experimental autoimmune myocarditis (EAM) induced by purified porcine cardiac myosin. The transplanted hybrid cell sheet exerts cardioprotective effects against EAM, resulting in limited left ventricular remodeling and partially improved cardiac functions due to revascularization, anti-inflammation, and anti-fibrosis. Thus, tissue engineering using hybrid cell sheets of fibroblasts constructed with QQMNCs is expected to provide an effective therapeutic option for patients with severe FM.

Abstract

Fulminant myocarditis causes impaired cardiac function, leading to poor prognosis and heart failure. Cell sheet engineering is an effective therapeutic option for improving cardiac function. Naïve blood mononuclear cells (MNCs) have been previously shown to enhance the quality and quantity of cellular fractions (QQMNCs) with anti-inflammatory and vasculogenic potential using the one culture system. Herein, we investigated whether autologous cell sheet transplant with QQMNCs improves cardiac function in a rat model with experimental autoimmune myocarditis (EAM). Fibroblast sheets (F-sheet), prepared from EAM rats, were co-cultured with or without QQMNCs (QQ+F sheet) on temperature-responsive dishes. QQ+F sheet induced higher expression of anti-inflammatory and vasculogenic genes (Vegf-b, Hgf, Il-10, and Mrc1/Cd206) than the F sheet. EAM rats were transplanted with either QQ+F sheet or F-sheet, and the left ventricular (LV) hemodynamic analysis was performed using cardiac catheterization. Among the three groups (QQ+F sheet, F-sheet, operation control), the QQ+F sheet transplant group showed alleviation of end-diastolic pressure–volume relationship on a volume load to the same level as that in the healthy group. Histological analysis revealed that QQ+F sheet transplantation promoted revascularization and mitigated fibrosis by limiting LV remodeling. Therefore, autologous QQMNC-modified F-sheets may be a beneficial therapeutic option for EAM.

Associations Between Inflammation, Cardiovascular Regenerative Capacity, and Cardiovascular Events: A Cohort Study

Objective

Circulating progenitor cells possess immune modulatory properties and might mitigate inflammation that is characteristic of patients with coronary artery disease. We hypothesized that patients with fewer circulating progenitor cells (CPCs) will have higher inflammatory markers and worse outcomes.

Approach and Results

Patients with stable coronary artery disease were enrolled in a prospective study enumerating CPCs as CD (cluster of differentiation)-34-expressing mononuclear cells (CD34+) and inflammation as levels of IL (interleukin)-6 and high-sensitivity CRP (C-reactive protein) levels. Patients were followed for 5 years for the end points of death and myocardial infarction with repeat inflammatory biomarkers measured after a median of 2 years. In the entire cohort of 392 patients, IL-6 and high-sensitivity CRP levels remained unchanged (0.3+/-2.4 pg/mL and 0.1+/-1.0 mg/L; P=0.45) after 2 years. CPC counts (log-transformed) were inversely correlated with the change in IL-6 levels (r, -0.17; P<0.001). Using linear regression, IL-6 and high-sensitivity CRP levels declined by -0.59 (95% CI, -0.90 to -0.20) pg/mL and -0.13 (-0.28 to 0.01) mg/L per 1 log higher CPC counts after adjustment for the demographic and clinical variables, as well as medications. Using Cox models adjusted for these risk factors, a rise in 1 pg/mL of IL-6 was associated with a 11% (95% CI, 9-13) greater risk of death/myocardial infarction. We found that the change in IL6 level partly (by 40%) mediated the higher risk of adverse events among those with low CPC counts.

Conclusions

Reduced cardiovascular regenerative capacity is independently associated with progressive inflammation in patients with coronary artery disease that in turn is associated with poor outcomes.

Isolation Methods for Human CD34 Subsets Using Fluorescent and Magnetic Activated Cell Sorting: an In Vivo Comparative Study

INTRODUCTION

Acute myocardial infarction (AMI) and resulting cardiac damage and heart failure are leading causes of morbidity and mortality worldwide. Multiple studies have examined the utility of CD34⁺ cells for the treatment of acute and ischemic heart disease. However, the optimal strategy to enrich CD34 cells from clinical sources is not known. We examined the efficacy of fluorescence activated cell sorting (FACS) and magnetic beads cell sorting (MACS) methods for CD34 cell isolation from mobilized human mononuclear peripheral blood cells (mhPBMNCs).

METHODS

mhPBCs were processed following acquisition using FACS or MACS according to clinically established protocols. Cell viability, CD34 cell purity and characterization of surface marker expression were assessed using a flow cytometer. For in vivo characterization of cardiac repair, we conducted LAD ligation surgery on 8-10 weeks female NOD/SCID mice followed by intramyocardial transplantation of unselected mhPBMNCs, FACS or MACS enriched CD34⁺ cells.

RESULTS

Both MACS and FACS isolation methods achieved high purity rates, viability, and enrichment of CD34⁺ cells. In vivo studies following myocardial infarction demonstrated retention of CD34⁺ in the peri-infarct region for up to 30 days after transplantation. Retained CD34⁺ cells were associated with enhanced angiogenesis and reduced inflammation compared to unselected mhPBMNCs or PBS treatment arms. Cardiac scar and fibrosis as assessed by immunohistochemistry were reduced in FACS and MACS CD34⁺ treatment groups. Finally, reduced scar and augmented angiogenesis resulted in improved cardiac functional recovery, both on the global and regional function and remodeling assessments by echocardiography.

CONCLUSION

Cell based therapy using enriched CD34⁺ cells sorted by FACS or MACS result in better cardiac recovery after ischemic injury compared to unselected mhPBMNCs. Both enrichment techniques offer excellent recovery and purity and can be equally used for clinical applications.

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. Graphical abstract.

Tyrosine-Protein Phosphatase Non-receptor Type 9 (PTPN9) Negatively Regulates the Paracrine Vasoprotective Activity of Bone-Marrow Derived Pro-angiogenic Cells: Impact on Vascular Degeneration in Oxygen-Induced Retinopathy

Background and Aim

Insufficient post-ischemic neovascularization is an initial key step in the pathogenesis of Oxygen-Induced Retinopathy (OIR). During neovascularization, pro-angiogenic cells (PACs) are mobilized from the bone marrow and integrate into ischemic tissues to promote angiogenesis. However, the modulation of PAC paracrine activity during OIR and the specific mechanisms involved remain to be explored. Because Tyrosine-protein phosphatase non-receptor type 9 (PTPN9) is reported to be a negative regulator of stem cell differentiation and angiogenesis signaling, we investigated its effect on PAC activity in the context of OIR.

Methods and Results

In a rat model of OIR, higher levels of PTPN9 in the retina and in bone marrow derived PACs are associated with retinal avascular areas, lower levels of the mobilization factor SDF-1 and decreased number of CD34⁺/CD117⁺/CD133⁺ PACs. PACs exposed ex vivo to hyperoxia display increased PTPN9 expression, which is associated with impaired ability of PAC secretome to promote angiogenesis ex vivo (choroidal vascular sprouting) and in vitro (endothelial cell tubule formation) compared to the secretome of PACs maintained in normoxia. Suppression of PTPN9 (using siRNA) increases VEGF and SDF-1 expression to normalize PAC secretome during hyperoxia, leading to restored angiogenic ability of PAC secretome. Moreover, endothelial cells exposed to the secretome of siPTPN9-treated PACs expressed increased levels of activated form of VEGF receptor 2 (VEGFR2). In the rat model of OIR, intravitreal injection of secretome from siPTPN9-treated PACs significantly reduced retinal vaso-obliteration; this was associated with higher retinal levels of VEGF/SDF-1, and increased recruitment of PACs (CD34⁺ cells) to the retinal and choroidal vessels.

Conclusion

Our results suggest that hyperoxia alters the paracrine proangiogenic activity of BM-PACs by inducing PTPN9, which can contribute to impair post-ischemic revascularization in the context of OIR. Targeting PTPN9 restores PAC angiogenic properties, and provide a new target for vessel integrity in ischemic retinopathies.

TLR4 /NF-ĸB and JAK2/STAT3 signaling pathways: Cellular signaling pathways targeted by cell-conditioned medium therapy in protection against ischemic stroke

Human amniotic membrane-derived mesenchymal stem cell-conditioned medium (hAMSC-CM) has been known to improve neuronal survival following ischemic stroke. The present study was designed to examine whether protective effects of hAMSC-CM against stroke can be linked to reducing neuroinflamation by targeting TLR4 /NF-ĸB and Jak2/Stat3 signaling pathways. Immunohistochemistry of hippocampus and western blot assay were performed to evaluate the expression of TLR4 /NF-ĸB and Jak2/Stat3, respectively. Real-time PCR assay was applied to investigate the mRNA levels of Jak2/Stat3. Hematoxylin and eosin (H&E) staining was used to investigate tissue damage and morphological changes in the CA1 region of hippocampus. Increased brain edema was seen in middle cerebral artery occlusion (MCAO) rats compared to sham. Post-treatment with hAMSC-CM markedly reduced brain edema in comparison with MCAO group (P < 0.05). Compared to sham, significantly increased levels of TLR4 /NF-ĸB and Jak2/Stat3 were seen in MCAO rats. Intravenous injection of hAMSC-CM after reperfusion markedly reduced levels of TLR4 /NF-ĸB and Jak2/Stat3 in hippocampus region (P < 0.05). Tissue damage and neuronal cell increased in the CA1 region of hippocampus that reversed by post-treatment by hAMSC-CM. Interestingly, our finding showed that hAMSC-CM can be considered as good candidate to reduce injury following ischemic stroke by decreasing activity of TLR4 /NF-ĸB and Jak2/Stat3 signaling pathways.

The secretome of endothelial progenitor cells: a potential therapeutic strategy for ischemic stroke

Ischemic stroke continues to be a leading cause of mortality and morbidity in the world. Despite recent advances in the field of stroke medicine, thrombolysis with recombinant tissue plasminogen activator remains as the only pharmacological therapy for stroke patients. However, due to short therapeutic window (4.5 hours of stroke onset) and increased risk of hemorrhage beyond this point, each year globally less than 1% of stroke patients receive this therapy which necessitate the discovery of safe and efficacious therapeutics that can be used beyond the acute phase of stroke. Accumulating evidence indicates that endothelial progenitor cells (EPCs), equipped with an inherent capacity to migrate, proliferate and differentiate, may be one such therapeutics. However, the limited availability of EPCs in peripheral blood and early senescence of few isolated cells in culture conditions adversely affect their application as effective therapeutics. Given that much of the EPC-mediated reparative effects on neurovasculature is realized by a wide range of biologically active substances released by these cells, it is possible that EPC-secretome may serve as an important therapeutic after an ischemic stroke. In light of this assumption, this review paper firstly discusses the main constituents of EPC-secretome that may exert the beneficial effects of EPCs on neurovasculature, and then reviews the currently scant literature that focuses on its therapeutic capacity.

Endothelial progenitor cell transplantation alleviated ischemic brain injury via inhibiting C3/C3aR pathway in mice

Endothelial progenitor cell transplantation is a potential therapeutic approach in brain ischemia. However, whether the therapeutic effect of endothelial progenitor cells is via affecting complement activation is unknown. We established a mouse focal ischemia model (n = 111) and transplanted endothelial progenitor cells into the peri-infarct region immediately after brain ischemia. Neurological outcomes and brain infarct/atrophy volume were examined after ischemia. Expression of C3, C3aR and pro-inflammatory factors were further examined to explore the role of endothelial progenitor cells in ischemic brain. We found that endothelial progenitor cells improved neurological outcomes and reduced brain infarct/atrophy volume after 1 to 14 days of ischemia compared to the control (p < 0.05). C3 and C3aR expression in the brain was up-regulated at 1 day up to 14 days (p < 0.05). Endothelial progenitor cells reduced astrocyte-derived C3 (p < 0.05) and C3aR expression (p < 0.05) after ischemia. Endothelial progenitor cells also reduced inflammatory response after ischemia (p < 0.05). Endothelial progenitor cell transplantation reduced astrocyte-derived C3 expression in the brain after ischemic stroke, together with decreased C3aR and inflammatory response contributing to neurological function recovery. Our results indicate that modulating complement C3/C3aR pathway is a novel therapeutic target for the ischemic stroke.

Important Flavonoids and Their Role as a Therapeutic Agent

Flavonoids are phytochemical compounds present in many plants, fruits, vegetables, and leaves, with potential applications in medicinal chemistry. Flavonoids possess a number of medicinal benefits, including anticancer, antioxidant, anti-inflammatory, and antiviral properties. They also have neuroprotective and cardio-protective effects. These biological activities depend upon the type of flavonoid, its (possible) mode of action, and its bioavailability. These cost-effective medicinal components have significant biological activities, and their effectiveness has been proved for a variety of diseases. The most recent work is focused on their isolation, synthesis of their analogs, and their effects on human health using a variety of techniques and animal models. Thousands of flavonoids have been successfully isolated, and this number increases steadily. We have therefore made an effort to summarize the isolated flavonoids with useful activities in order to gain a better understanding of their effects on human health.

A Gutsy Move for Cell-Based Regenerative Medicine in Parkinson's Disease: Targeting the Gut Microbiome to Sequester Inflammation and Neurotoxicity

Pharmaceuticals and cell-based regenerative medicine for Parkinson’s disease (PD) offer palliative relief but do not arrest the disease progression. Cell therapy has emerged as an experimental treatment, but current cell sources such as human umbilical cord blood (hUCB) stem cells display only partial recapitulation of mature dopaminergic neuron phenotype and function. Nonetheless, stem cell grafts ameliorate PD-associated histological and behavioral deficits likely through stem cell graft-secreted therapeutic substances. We recently demonstrated the potential of hUCB-derived plasma in enhancing motor capabilities and gastrointestinal function, as well as preventing dopaminergic neuronal cell loss, in an 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine (MPTP) rodent model of PD. Recognizing the translational need to test in another PD model, we now examined here the effects of an intravenously transplanted combination of hUCB and plasma into the 6-hydroxydopamine (6-OHDA) lesioned adult rats. Animals received three separate doses of 4 × 10⁶ hUCB cells with plasma beginning at 7 days after stereotaxic 6-OHDA lesion, then behaviorally and immunohistochemically evaluated over 56 days post-lesion. Whereas vehicle-treated lesioned animals exhibited the typical 6-OHDA neurobehavioral symptoms, hUCB and plasma-treated lesioned animals showed significant attenuation of motor function, gut motility, and nigral dopaminergic neuronal survival, combined with diminished pro-inflammatory microbiomes not only in the nigra, but also in the gut. Altogether these data support a regenerative medicine approach for PD by sequestering inflammation and neurotoxicity through correction of gut dysbiosis.

ATP-Nlrp3 Inflammasome-Complement Cascade Axis in Sterile Brain Inflammation in Psychiatric Patients and its Impact on Stem Cell Trafficking

Recent evidence indicates that the occurrence of psychiatric disorders in patients is linked to a local “sterile” inflammation of brain or due to a systemic inflammation process that affects the central nervous system. This is supported by the observation that in peripheral blood of psychotic patients are detectable several mediators and markers of inflammation as well as clinical data on correlations between systemic chronic inflammatory processes and psychiatric disorders. This may explain why some reported anti-inflammatory treatment strategies have beneficial effects on ameliorating psychotic events. In this review we will present a concept that aberrant purinergic signaling and increases in extracellular level of adenosine triphosphate (ATP) in the brain parenchyma may lead to activation of Nlrp3 inflammasome in microglia cells and as a consequence microglia released danger associated molecular pattern (DAMP) proteins activate complement cascade (ComC) in mannan binding lectin (MBL) – dependent manner. Activation of ATP-Nlrp3 inflammasome-ComC axis may also orchestrate trafficking of stem cells released from bone marrow into peripheral blood observed in psychotic patients. Based on this, the ATP-Nlrp3 inflammasome-ComC axis may become a target for new therapeutic approaches, which justifies the development and clinical application of efficient anti-inflammatory treatment strategies targeting this axis in psychiatry.

Stem Cells as Drug-like Biologics for Mitochondrial Repair in Stroke

Stroke is a devastating condition characterized by widespread cell death after disruption of blood flow to the brain. The poor regenerative capacity of neural cells limits substantial recovery and prolongs disruptive sequelae. Current therapeutic options are limited and do not adequately address the underlying mitochondrial dysfunction caused by the stroke. These same mitochondrial impairments that result from acute cerebral ischemia are also present in retinal ischemia. In both cases, sufficient mitochondrial activity is necessary for cell survival, and while astrocytes are able to transfer mitochondria to damaged tissues to rescue them, they do not have the capacity to completely repair damaged tissues. Therefore, it is essential to investigate this mitochondrial transfer pathway as a target of future therapeutic strategies. In this review, we examine the current literature pertinent to mitochondrial repair in stroke, with an emphasis on stem cells as a source of healthy mitochondria. Stem cells are a compelling cell type to study in this context, as their ability to mitigate stroke-induced damage through non-mitochondrial mechanisms is well established. Thus, we will focus on the latest preclinical research relevant to mitochondria-based mechanisms in the treatment of cerebral and retinal ischemia and consider which stem cells are ideally suited for this purpose.

Mesenchymal stem cells injected into carotid artery to target focal brain injury home to perivascular space

Rationale: The groundbreaking discovery of mesenchymal stem cells (MSCs) with their multifaceted benefits led to their widespread application in experimental medicine, including neurology. Efficient delivery of MSCs to damaged regions of the central nervous system may be a critical factor in determining outcome. Integrin VLA-4 (α4β1) coded by ITGA4 and ITGB1 genes is an adhesion molecule expressed by leukocytes, which is responsible for initiation of their diapedesis through cell docking to the inflamed vessel wall expressing VCAM1 receptor. This function of VLA-4 has been recapitulated in neural stem cells and glial progenitors. Thus, it was prudent to investigate this tool as a vehicle driving extravasation of MSCs. Since MSCs naturally express ITGB1 subunit, we decided to supplement them with ITGA4 only. The purpose of our current study is to investigate the eventual fate of IA delivered ITGA4 engineered and naive MSCs.

Methods: mRNA-ITGA4 transfected and naive MSCs were injected to right internal carotid artery of rats with focal brain injury. Through next three days MSC presence in animals' brain was navigated by magnetic resonance imaging. Transplanted cell location relative to the brain blood vessels and host immunological reaction were analyzed post-mortem by immunohistochemistry. The chemotaxis of modified and naive MSCs was additionally examined in in vitro transwell migration assay.

Results: Both naïve and ITGA4-overexpressing cells remained inside the vascular lumen over the first two days after IA infusion. On the third day, 39% of mRNA-ITGA4 modified and 51% naïve MSCs homed to perivascular space in the injury region (p=NS). The gradual decrease of both naive and mRNA-ITGA4 transfected hBM-MSCs in the rat brain was observed. mRNA-ITGA4 transfected MSCs appeared to be more vulnerable to phagocytosis than naïve cells. Moreover, in vitro study revealed that homogenate from the injured brain repels migration of MSCs, corroborating the incomplete extravasation observed in vivo.

Conclusions: In summary, IA transplanted MSCs are capable of homing to the perivascular space, an integral part of neurovascular unit, which might contribute to the replacement of injured pericytes, a critical element facilitating restoration of CNS function. The mRNA-ITGA4 transfection improves cell docking to vessel but this net benefit vanishes over the next two days due to fast clearance from cerebral vessels of the majority of transplanted cells, regardless of their engineering status. The drawbacks of mRNA-ITGA4 transfection become apparent on day 3 post transplantation due to the lower survival and higher vulnerability to host immune attack.

Spleen participation in partial MHC class II construct neuroprotection in stroke

Pathological progression of stroke in the peripheral and central nervous systems (PNS and CNS) is characterized by multiple converging signalling pathways that exacerbate neuroinflammation-mediated secondary cell death. This creates a need for a novel type of immunotherapy capable of simultaneously lowering the synergistic inflammatory responses in the PNS and CNS, specifically the spleen and brain. Previously, we demonstrated that partial major histocompatibility complex (MHC) class II constructs can be administered subcutaneously to promote histological and behavioural effects that alleviate common symptoms found in a murine model of transient stroke. This MHC class II manipulates T cell cytokine expression in both PNS and CNS, resulting in dampened inflammation. In our long-standing efforts towards translational research, we recently demonstrated that a potent next generation mouse-based partial MHC class II construct named DRmQ (DRa1_L50Q -mMOG-35-55) similarly induces neuroprotection in stroke rats, replicating the therapeutic effects of the human homolog as DRhQ (DRa1_L50Q -human (h)MOG-35-55) in stroke mice. Our preclinical studies showed that DRmQ reduces motor deficits, infarct volume and peri-infarct cell loss by targeting inflammation in this second species. Moreover, we provided mechanistic support in both animal studies that partial MHC class II constructs effectively modulate the spleen, an organ which plays a critical role in modulating secondary cell death. Together, these preclinical studies satisfy testing the constructs in two stroke models, which is a major criterion of the Stroke Therapy Academic Industry Roundtable (STAIR) criteria and a key step in effectively translating this drug to the clinic. Additional translational studies, including dose-response and larger animal models may be warranted to bring MHC class II constructs closer to the clinic.

Harnessing the anti-inflammatory properties of stem cells for transplant therapy in hemorrhagic stroke

Hemorrhagic stroke is a global health crisis plagued by neuroinflammation in the acute and chronic phases. Neuroinflammation approximates secondary cell death, which in turn robustly contributes to stroke pathology. Both the physiological and behavioral symptoms of stroke correlate with various inflammatory responses in animal and human studies. That slowing the secondary cell death mediated by this inflammation may attenuate stroke pathology presents a novel treatment strategy. To this end, experimental therapies employing stem cell transplants support their potential for neuroprotection and neuroregeneration after hemorrhagic stroke. In this review, we evaluate experiments using different types of stem cell transplants as treatments for stroke-induced neuroinflammation. We also update this emerging area by examining recent preclinical and clinical trials that have deployed these therapies. While further investigations are warranted to solidify their therapeutic profile, the reviewed studies largely posit stem cells as safe and potent biologics for stroke, specifically owing to their mode of action for sequestering neuroinflammation and promoting neuroregenerative processes.

The brain and eye: Treating cerebral and retinal ischemia through mitochondrial transfer

Stroke remains a devastating disease with limited treatment options, despite our growing understanding of its pathology. While ischemic stroke is traditionally characterized by a blockage of blood flow to the brain, this may coincide with reduced blood circulation to the eye, resulting in retinal ischemia, which may in turn lead to visual impairment. Although effective treatment options for retinal ischemia are similarly scarce, new evidence suggests that deleterious changes to mitochondrial structure and function play a major role in both cerebral and retinal ischemia pathologies. Prior studies establish that astrocytes transfer healthy mitochondria to ischemic neurons following stroke; however, this alone is not enough to significantly mitigate the damage caused by primary and secondary cell death. Thus, stem cell-based regenerative medicine targeting amelioration of ischemia-induced mitochondrial dysfunction via the transfer of functional mitochondria to injured neural cells represents a promising approach to improve stroke outcomes for both cerebral and retinal ischemia. In this review, we evaluate recent laboratory evidence supporting the remedial capabilities of mitochondrial transfer as an innovative stroke treatment. In particular, we examine exogenous stem cell transplants in their potential role as suppliers of healthy mitochondria to neurons, brain endothelial cells, and retinal cells.

Impact statement

Stroke constitutes a global health crisis, yet potent, applicable therapeutic options remain effectively inaccessible for many patients. To this end, stem cell transplants stand as a promising stroke treatment and as an emerging subject of research for cell-based regenerative medicine. This is the first review to synthesize the implications of stem cell-derived mitochondrial transfer in both the brain and the eye. As such, this report carries fresh insight into the commonalities between the two stroke-affected organs. We present the findings of this developing area of research inquiry with the hope that our evaluation may advance the use of stem cell transplants as viable therapeutic alternatives for ischemic stroke and related disorders characterized by mitochondrial dysfunction. Such lab-to-clinic translational advancement has the potential to save and improve the ever increasing millions of lives affected by stroke.

Cerebral circulation improves with indirect bypass surgery combined with gene therapy

Angiogenesis involves new blood vessels sprouting from preexisting blood vessels. This process may serve to improve brain circulation. Moyamoya disease (MMD) is a cerebrovascular disorder causing intracranial stenosis which significantly reduces the blood supply to the brain. Mainly stroke is the first symptom of the disorder, so treatments that reduce the risk of stroke are used for patients with MMD. To prevent stroke for those with chronic cerebral hypoperfusion, more blood needs to flow to the brain, which was thought to be achieved by enhancing angiogenesis. Indirect bypass surgery, such as encephalo-myo-synangiosis (EMS), is used for revascularization. However, EMS alone sometimes cannot provide enough circulation to avoid ischemic strokes. The current study examined if EMS combined with high-mobility group box-1 (HMGB1) and vascular endothelial growth factor (VEGF) enhanced angiogenesis and increased cerebral circulation. The results indicated that HMGB1 administered with EMS increased angiogenesis through a VEGF-dependent mechanism. In addition, exercising and stem cell transplantation possess possible means to increase angiogenesis. Overall, EMS with gene therapy, maintaining fitness, and stem cell utilization may prevent or help one recover from stroke by enhancing brain angiogenesis. Thus, these treatments may be applicable for patients with MMD. This paper is a review article. Referred literature in this paper has been listed in the references section. The datasets supporting the conclusions of this article are available online by searching various databases, including PubMed.

A brief physical activity protects against ischemic stroke

With restricted therapeutic opportunities, stroke remains a relevant, critical disease necessitating study. Due to the unique aspect of ischemic strokes, finding approaches to maintain the vigor of the cerebral vasculature, such as increased angiogenesis, may protect against stroke. Ischemic strokes are caused by disruptions in blood movement in the brain, resulting in a torrent of harmful cerebrovasculature modifications. In an investigation by Pianta et al., Sprague-Dawley rats have been separated into those that undergo exercise prior to middle cerebral artery occlusion (MCAO) and those that were not exposed to physical activity preceding MCAO. The outcomes and results of the current study gave new insights into the capacity of exercise to help prevent ischemic strokes or mitigate poststroke effects. The data collected from the study suggested that rats that went through a short bout of exercise before MCAO presented superior motor performance, more active cells in the peri-infarct region, and reduced infarct sizes. When compared to the control group, the rats that went through exercise also had heightened angiogenesis and improved neuroprotection. Thus, a brief bout of physical activity preceding a stroke may provide neuroprotection by enhancing the strength of the cerebrovasculature in the brain. This notion that even an instant of physical exercise before a stroke is induced can help dampen the effects of ischemic stroke, which could lead to future techniques in preventing the ischemic stroke so that it never happens at all.

Influence of Inflammatory Disease on the Pathophysiology of Moyamoya Disease and Quasi-moyamoya Disease

Moyamoya disease is a unique cerebrovascular disease that is characterized by progressive bilateral stenotic alteration at the terminal portion of the internal carotid arteries. These changes induce the formation of an abnormal vascular network composed of collateral pathways known as moyamoya vessels. In quasi-moyamoya disease, a similar stenotic vascular abnormality is associated with an underlying disease, which is sometimes an inflammatory disease. Recent advances in moyamoya disease research implicate genetic background and immunological mediators, and postulate an association with inflammatory disease as a cause of, or progressive factor in, quasi-moyamoya disease. Although this disease has well-defined clinical and radiological characteristics, the role of inflammation has not been rigorously explored. Herein, we focused on reviewing two main themes: (1) molecular biology of inflammation in moyamoya disease, and (2) clinical significance of inflammation in quasi-moyamoya disease. We have summarized the findings of the former theme according to the following topics: (1) inflammatory biomarkers, (2) genetic background of inflammatory response, (3) endothelial progenitor cells, and (4) noncoding ribonucleic acids. Under the latter theme, we summarized the findings according to the following topics: (1) influence of inflammatory disease, (2) vascular remodeling, and (3) mechanisms gleaned from clinical cases. This review includes articles published up to February 2019 and provides novel insights for the treatment of the moyamoya disease and quasi-moyamoya disease.