Blood Flow Recovery Research Articles

Platelet Membrane Nanocarriers Cascade Targeting Delivery System to Improve Myocardial Remodeling Post Myocardial Ischemia-Reperfusion Injury.

Although treatments for myocardial infarction have advanced significantly, the global mortality due to ischemia and subsequent reperfusion injury remains high. Here, a platelet (PLT) membrane nanocarrier (PL720) that encapsulates L-arginine and FTY720 to facilitate the cascade-targeted delivery of these substances to the myocardial injury site and enable the controlled release of L-arginine and FTY720 is developed. Such an innovative approach shows enhanced cardioprotection through multiple target strategies involved in ischemia-reperfusion injury and late reperfusion inflammation. During the ischemia-reperfusion phase, PL720 targets and accumulates in damaged coronary arteries. PL720 rapidly releases L-arginine, stimulating endothelial cells to produce NO, thereby dilating blood vessels and promoting blood flow recovery, while FTY720's sustained release exerts anti-apoptotic effects. During the late reperfusion inflammatory phase, PL720 is captured by circulating inflammatory monocytes and transported into a deeper ischemic myocardial lesion. PL720 promotes macrophage polarization and accelerates the inflammatory repair. Furthermore, the issue of bradycardia associated with the clinical use of FTY720 is innovatively relieved. Therefore, PL720 is a vascular injury and inflammation dual targeting strategy, exhibiting significant potential for multi-targeted therapy and clinical translation for cardiac injury.

A phase 2 trial investigating the efficacy and safety of the mPGES-1 inhibitor vipoglanstat in systemic sclerosis-related Raynaud's.

Our objective was to test the hypothesis, in a double-blind, placebo-controlled study that vipoglanstat, an inhibitor of microsomal prostaglandin E synthase-1 (mPGES-1) which decreases prostaglandin E2 (PGE2) and increases prostacyclin biosynthesis, improves RP. Patients with systemic sclerosis (SSc) and ≥7 RP attacks during the last screening week prior to a baseline visit were randomised to four weeks treatment with vipoglanstat 120 mg or placebo. A daily electronic diary captured RP attacks (duration and pain) and Raynaud's Condition Score, with change in RP attacks/week as primary end point. Cold challenge assessments were performed at baseline and end of treatment. Exploratory endpoints included patients' and physicians' global impression of change, Assessment of Scleroderma-associated Raynaud's Phenomenon questionnaire, mPGES-1 activity, and urinary excretion of arachidonic acid metabolites. Sixty-nine subjects received vipoglanstat (n = 33) or placebo (n = 36). Mean weekly number of RP attacks (baseline; vipoglanstat 14.4[SD 6.7], placebo 18.2[12.6]) decreased by 3.4[95% CI -5.8;-1.0] and 4.2[-6.5;-2.0] attacks per week (p= 0.628) respectively. All patient reported outcomes improved, with no difference between the groups. Mean change in recovery of peripheral blood flow after cold challenge did not differ between the study groups. Vipoglanstat fully inhibited mPGES-1, resulting in 57% reduction of PGE2 and 50% increase of prostacyclin metabolites in urine. Vipoglanstat was safe and well tolerated. Although vipoglanstat was safe, and well tolerated in a dose achieving full inhibition of mPGES-1, it was ineffective in SSc-related RP. Further development and evaluation of vipoglanstat will therefore be in other diseases where mPGES-1 plays a pathogenetic role.

P047 Deconditioning in quiescent Crohn’s Disease patients with heightened fatigue perception

Abstract Background Heightened fatigue perception and premature exercise fatigue are common in inflammatory bowel disease (IBD). Physical deconditioning is greater in patients with increased fatigue perception relative to patients with a lower perception of fatigue, implicating deconditioning as an aetiological factor. This study used physiology and multiparametric Magnetic Resonance Imaging and Spectroscopy (MRI/MRS) during exercise to comprehensively phenotype quiescent IBD fatigue. Methods Participant body mass and regional body composition was assessed by DEXA, and tknee extensor strength and fatiguability using isokinetic dynamometry (Cybex, USA). A supine CPET was performed using an MR-compatible Ergometer (Cardiostepper, Ergospect) to standardize relative exercise intensity for in-bore 1H MRI measures. 1H MRI data were collected on a Philips 3T Ingenia wide bore scanner using a Philips Head/Neck coil and in-built posterior coil. Across rest, steady-state exercise (50% VO2 peak) and recovery, Phase Contrast-MRI was used to compute cardiac output and cerebral blood flow (CBF), and T2 Relaxation under spin tagging (TRUST-MRI) to measure brain oxygen extraction fraction (OEF). 31P MRS data was collected on a 3T Philips Achieva using a 14cm 31P coil over the medial gastrocnemius. Ischaemic plantar flexion exercise was performed at 50% maximum voluntary contraction (MVC) using an MR-compatible ergometer (Trispect, Ergospect) during non-localized pulse-acquire 31P-MRS. 31P spectra were analysed using the AMARES function in jMRUI Beta 6.0. In vivo muscle mitochondrial flux during post-exercise PCr recovery (VPCr = kPCr * ΔPCr) where ΔPCr is PCrendrecovery –PCrendex) was quantified after reinstating limb blood flow and fitting PCr recovery to a mono-exponential function in GraphPad prism (PCr(t) = PCrinitial+(PCrend – PCrinitial)(1-exp(-k.t) where t is time from start of non-ischaemic recovery). Results 16 quiescent CD patients and 12 age and BMI matched HV’s completed the study. General fatigue score was greater in CD relative to HV (P = 0.001, Table 1). Body composition, isometric strength, fatigue development were not different between groups (Table 1). CBF response to steady-state exercise was less in CD (P = 0.003) alongside the maintenance of cardiac output and brain OEF in HV (Figure 1). VPCr following ischemic plantar flexion exercise was less in CD than HV (P = 0.02, Figure 1) (Figure 1). Conclusion Greater fatigue perception in CD was accompanied by lower CBF on exercise and blunted post-exercise PCr resynthesis, but no differences in body composition, strength and fatiguability relative to HV. These finding point to greater deconditioning in CD, corroborated by their lower daily step count relative to HV.

Buyang Huanwu Decoction promotes arteriogenesis after hindlimb ischemia in mice by activating PDGF signaling pathway

This study aims to investigate the effect of Buyang Huanwu Decoction on blood flow recovery and arteriogenesis after hindlimb ischemia in mice via the platelet-derived growth factor(PDGF) signaling pathway. Forty C57BL/6 mice were randomized into model(clean water, 10 mL·kg~(-1)·d~(-1)), beraprost sodium(positive control, 18 μg·kg~(-1)·d~(-1)), and low-, medium-, and high-dose(10, 20, and 40 g·kg~(-1)·d~(-1), respectively) Buyang Huanwu Decoction groups(n=8). The hindlimb ischemia model was established by femoral artery ligation. The mice were administrated with corresponding agents by gavage daily for 14 days after ligation. For laser Doppler perfusion imaging, the mice were anesthetized and measured under a Periscan PSI imager. The density of capillary and arterio-le in the ischemic gastrocnemius was measured using immunofluorescence staining of the frozen tissue sections. Western blot was employed to determine the expression of PDGF subunit B(PDGFB), phosphorylated mitogen extracellular kinase(p-MEK), MEK, phosphorylated extracellular signal-regulated kinase(p-ERK), and ERK. Real-time PCR was employed to determine the mRNA level of PDGFB. The Buyang Huanwu Decoction-containing serum was used to treat the vascular smooth muscle cells(VSMCs) in hypoxia at doses of 10% and 20%. The proliferation and migration of VSMCs was assessed in vitro. The results showed that compared with the model group, beraprost sodium and Buyang Huanwu Decoction enhanced the blood flow recovery, increased the capillary and arteriole density, and up-regulated the protein levels of PDGFB, p-MEK, p-ERK, and mRNA levels of PDGFB, with the medium-dose Buyang Huanwu Decoction demonstrating the most significant effect. The 10% Buyang Huanwu Decoction-containing serum enhanced the proliferation and migration of VSMCs. Our findings demonstrate that Buyang Huanwu Decoction up-regulates PDGFB transcription and activates PDGF signaling pathway to promote arteriogenesis and blood flow recovery in ischemic gastrocnemius.

Hypercholesterolemia impairs collateral artery enlargement by ten-eleven translocation 1-dependent hematopoietic stem cell autonomous mechanism in a murine model of limb ischemia

ObjectiveThe extent of collateral artery enlargement determines the risk of limb loss due to peripheral arterial disease. Hypercholesterolemia impairs collateral artery enlargement, but the underlying mechanism remains poorly characterized. This study tests the hypothesis that hypercholesterolemia impairs collateral artery enlargement through a ten-eleven translocation 1 (Tet1)-dependent hematopoietic stem cell (HSC)-autonomous mechanism that increases their differentiation into proinflammatory Ly6Chi monocytes and restricts their conversion into proangiogenic Ly6Clow monocytes. MethodsTo test our hypothesis, we induced limb ischemia and generated chimeric mouse models by transplanting HSCs from either wild-type (WT) mice or hypercholesterolemic mice into lethally irradiated WT recipient mice. ResultsWe found that the lethally irradiated WT recipient mice reconstituted with HSCs from hypercholesterolemic mice displayed lower blood flow recovery and collateral artery enlargement that was nearly identical to that observed in hypercholesterolemic mice, despite the absence of hypercholesterolemia and consistent with an HSC-autonomous mechanism. We showed that hypercholesterolemia impairs collateral artery enlargement by a Tet1-dependent mechanism that increases HSC differentiation toward proinflammatory Ly6Chi monocytes and restricts the conversion of Ly6Chi monocytes into proangiogenic Ly6Clow monocytes. Moreover, Tet1 epigenetically reprograms monocyte gene expression within the HSCs. Restoration of Tet1 expression in HSCs of hypercholesterolemic mice restores WT collateral artery enlargement and blood flow recovery after induction of hindlimb ischemia. ConclusionsThese results show that hypercholesterolemia impairs collateral artery enlargement by a novel Tet1-dependent HSC-autonomous mechanism that epigenetically reprograms monocyte gene expression within the HSCs.

Function and mechanism of the human SOD2 gene in mice cerebral ischemia/ reperfusion injury.

To investigate the neuroprotective effects of the SOD2 gene in cerebral ischemia reperfusion injury function and the underlying mechanisms in a mice model of middle cerebral artery ischemia reperfusion. SOD2 transgenic mice were engineered using transcription activator-like effector nucleases, and the genotype was identified using PCR after every three generations. Transgenic and C57BL/6J wild type mice were simultaneously subjected to the middle cerebral artery occlusion model. SOD2 expression in the brain, heart, kidney, and skeletal muscle of transgenic mice was significantly higher than that in the wild type. Following ischemia reperfusion, the infarct volume of wild type mice decreased after treatment with fenofibrate compared to the CMC group. Infarction volume in SOD2 transgenic mice after CMC and fenofibrate treatment was significantly reduced. The recovery of cerebral blood flow in wild type mice treated with fenofibrate was significantly enhanced compared with that in the CMC group. The expression of SOD2 in transgenic mice was significantly higher than that in wild type mice, the neuroprotective role of fenofibrate depends on an increase in SOD2 expression.

P407 hydrogel loaded with nitric oxide microbubbles promotes angiogenesis and functional improvement in testicular transplantation.

Prepubertal male patients with cancer have decreased fertility after treatment, but there are currently no suitable means for fertility rescue. Testicular transplantation seems to be a promising treatment. The short-term insufficiency of blood supply after transplantation is the key problem that needs to be solved. In this research, nitric oxide (NO), a gas and small molecule transmitter with the effect of promoting angiogenesis, acted at the site of testicular transplantation. Herein, poloxamer-407 (P407) and lipid microbubble materials served as transport carriers for NO and helped NO to function at the transplant site. P407 hydrogel loaded with NO microbubbles (PNO) slowly released NO in vitro. The three-dimensional space of the hydrogel provided a stable environment for NO microbubbles, which is conducive to the continuous release of NO. In this study, 25% PNO (w/v) was selected, and the gelling temperature was 19.47 °C. The gelling efficiency was relatively high at body temperature. Rheological experiments showed that PNO, at this concentration, had stable mechanical properties. The results from in vivo experiments demonstrated that testicular grafts in the PNO group exhibited a notably accelerated blood flow recovery compared to the other groups. Additionally, the PNO group displayed a significant improvement in reproductive function recovery. In conclusion, PNO exhibited slow release of NO, and a small amount of NO promoted angiogenesis in testicular grafts and restored reproductive function.

Single-cell transcriptomics identifies adipose tissue CD271+ progenitors for enhanced angiogenesis in limb ischemia

Therapeutic angiogenesis using mesenchymal stem/stromal cell grafts have shown modest and controversial effects in preventing amputation for patients with critical limb ischemia. Through single-cell transcriptomic analysis of human tissues, we identify CD271+ progenitors specifically from subcutaneous adipose tissue (AT) as having the most prominent pro-angiogenic gene profile distinct from other stem cell populations. AT-CD271+ progenitors demonstrate robust invivo angiogenic capacity over conventional adipose stromal cell grafts, characterized by long-term engraftment, augmented tissue regeneration, and significant recovery of blood flow in a xenograft model of limb ischemia. Mechanistically, the angiogenic capacity of CD271+ progenitors is dependent on functional CD271 and mTOR signaling. Notably, the number and angiogenic capacity of CD271+ progenitors are strikingly reduced in insulin-resistant donors. Our study highlights the identification of AT-CD271+ progenitors with invivo superior efficacy for limb ischemia. Furthermore, we showcase comprehensive single-cell transcriptomics strategies for identification of suitable grafts for cell therapy.

Astragaloside IV promotes cerebral angiogenesis and neurological recovery after focal ischemic stroke in mice via activating PI3K/Akt/mTOR signaling pathway

Our previous work has shown that activating PI3K/Akt/mTOR signaling pathway is involved in angiogenesis after ischemic stroke, and recent studies have revealed that astragaloside IV (AS-IV) exerts beneficial effects on cerebral protection after ischemic stroke. However, it is unclear whether the beneficial effects of AS-IV against ischemic stroke is related to angiogenesis and PI3K/Akt/mTOR signaling pathway. The aim of this study was to investigate the effects of AS-IV on angiogenesis and long-term neurological recovery after focal ischemic stroke as well as the underlying mechanisms. After mice model of distal middle cerebral artery occlusion (dMCAO), AS-IV was administered with low dose (10 mg/kg), medium dose (20 mg/kg) or high dose (40 mg/kg) once daily for 14 days. We report herein that AS-IV (20 mg/kg) significantly ameliorated long-term neurological recovery and attenuated histological damage, while promoting cerebral blood flow recovery in ischemic mice. Moreover, AS-IV administration enhanced microvessel density as well as astrocyte and pericyte coverage around microvessels in the peri-infarct cortex. In vitro, AS-IV promoted endothelial cells (ECs) proliferation and tube formation after oxygen-glucose deprivation (OGD), which was partially inhibited by the specific PI3K inhibitor LY294002. Finally, AS-IV increased the expression of vascular endothelial growth factor (VEGF) through activating the PI3K/AKT/mTOR signaling pathway in the process of promoting angiogenesis. These results suggested that AS-IV may promote angiogenesis after ischemic stroke through increasing the expression of VEGF via PI3K/Akt/mTOR pathway, which unveils novel therapeutic effects of AS-IV and suggests promising application of AS-IV in ischemic stroke.

Histidine Triad Nucleotide-Binding Protein 1 Improves Critical Limb Ischemia by Regulating Mitochondrial Homeostasis

Critical limb ischemia (CLI) is a common complication of diabetes mellitus that typically occurs in the later stages of the disease. Vascularization is indeed an important physiological process involving the formation of new blood vessels from existing ones. It occurs in response to various normal and pathophysiological conditions, and one of its critical roles is to compensate for inadequate oxygen supply, which is often seen in situations like chronic limb ischemia (CLI). Histidine triad nucleotide-binding protein 1 (Hint1) is a member of the Hint family that has been shown to attenuate cardiac hypertrophy, but its role in vascularization still needs to be clarified. In this study, we investigated the role of Hint1 in CLI. We found that Hint1 is significantly reduced in the muscle tissue of STZ-induced diabetic mice and high-glucose (HG)-treated endothelial cells (ECs). Hint1 deletion impaired blood flow recovery and vascularization, whereas Hint1 overexpression promoted these processes. In addition, our in vitro study showed that Hint1 deficiency aggravated mitochondrial dysfunction in ECs, as evidenced by impaired mitochondrial respiration, decreased mitochondrial membrane potential, and increased reactive oxygen species. Our findings suggest that Hint1 deficiency impairs blood perfusion by damaging mitochondrial function and that Hint1 may represent a potential therapeutic target for treating CLI.

Histone Mono-methylation by SETD7 Orchestrates Angiogenic Response in Diabetic Limb Ischemia

Abstract Background Peripheral artery disease (PAD) is highly prevalent in patients with diabetes (DM) and associates with a high rate of limb amputation and poor prognosis. Surgical and catheter-based revascularization have failed to improve outcome in DM patients with PAD. Hence, a need exists to develop new treatment strategies able to promote blood vessel growth in this setting. Mono-methylation of histone 3 at lysine 4 (H3K4me1) - a specific epigenetic signature induced by the histone methyltransferase SETD7 - favours an open chromatin thus enabling gene transcription. Purpose: To investigate whether SETD7-dependent epigenetic changes modulate angiogenic response in diabetes. Methodology: Primary human aortic endothelial cells (HAECs) were exposed to normal glucose (NG, 5 mM) or high glucose (HG, 25 mM) concentrations for 48 hours. Unbiased gene expression profiling was performed by RNA sequencing (RNA-seq) followed by Ingenuity Pathway Analysis (IPA). In vitro assays, namely cell migration and tube formation were employed to study angiogenic properties in HAECs. SETD7 and H3K4me1 levels were investigated by Western blot and Chromatin immunoprecipitation (ChIP). Pharmacological blockade of SETD7 was achieved by using the highly selective inhibitor (R)-PFI-2. Mice with streptozotocin-induced diabetes were orally treated with (R)-PFI-2 or vehicle and underwent hindlimb ischemia by femoral artery ligation for 14 days. Blood flow recovery was analysed at 30 minutes, 7 and 14 days by laser Doppler imaging. Our experimental findings were also translated in gastrocnemius muscle samples from patients with and without diabetes. Results RNA-seq in HG-treated HAECs revealed a profound upregulation of the methyltransferase SETD7, an enzyme involved in mono-methylation of lysine 4 at histone 3 (H3K4me1). SETD7 upregulation in HG-treated HAECs was associated with increased H3K4me1 levels as well as with impaired endothelial cell migration and tube formation. Both SETD7 gene silencing and pharmacological inhibition by (R)PFI-2 rescued hyperglycemia-induced impairment of HAECs migration and tube formation, while SETD7 overexpression blunted the angiogenic response. RNA-seq and ChIP assays showed that SETD7-dependent H3K4me1 regulates the transcription of the angiogenesis inhibitor semaphorin-3G (SEMA-3G, (Figure 1). Moreover, SEMA-3G overexpression blunted migration and tube formation in SETD7-depleted HAECs. In diabetic mice with hindlimb ischemia, treatment with (R)-PFI-2 improved limb vascularization and perfusion as compared to vehicle (Figure 2). Finally, SETD7/SEMA3G axis was upregulated in muscle specimens from T2D patients as compared to controls (Figure 2) Conclusion: Targeting SETD7 represents a novel epigenetic-based therapy to boost neovascularization in diabetic patients with PAD.

Abstract 18998: Deletion of the Duffy Antigen Receptor for Chemokines Impairs Blood Flow Recovery in the Mouse Hindlimb Ischemia Model: Role of CCL11

Introduction: Peripheral Artery Disease (PAD) is characterized by obstruction of the arteries in the lower extremities. Impaired angiogenesis plays a major role in the progression of PAD. Pro-angiogenic and anti-angiogenic chemokines are modulated by binding to the Duffy antigen receptor for chemokines (DARC), a non-signaling receptor expressed primarily on erythrocytes. Incidence and severity of PAD is greater in Blacks, ~70% of whom do not express DARC on their erythrocytes due to a common gene variant. Here, we tested the hypothesis that hematopoietic-specific deletion of DARC impairs blood flow recovery in mouse hindlimb ischemia model. Methods: Twelve week old female DARC Flox/Vav1-Cre+ (DARC HKO ) and littermate Vav1-Cre- (wild type, WT) mice underwent unilateral femoral artery ligation and excision. Ischemic muscle tissue and plasma were analyzed at early ischemic phase (day three post ligation) and late ischemic phase (day fourteen post ligation). Blood flow recovery was measured weekly via laser Doppler imaging. Results: DARC HKO mice had poor blood flow recovery compared to WT mice (p<0.05), along with reduced capillary formation and increased inflammation, necrosis and fibrosis in the ischemic gastrocnemius muscles. Amongst the various DARC-bound chemokines assayed, levels of CCL11 (a pro-angiogenic strong DARC-bound chemokine) were significantly reduced in the plasma of DARC HKO mice, both at early and late ischemic phases (p<0.01). CCL11 levels strongly correlated with capillary formation in ischemic hindlimb. CCL11 levels in ischemic muscle tissue were significantly reduced in the DARC HKO mice in the early, but not late, ischemic phase. Conclusions: Loss of DARC on hematopoietic cells has a negative impact on the recovery of perfusion and angiogenesis in the murine hindlimb ischemia model, possibly due to reduced levels of CCL11 consequent to DARC deletion. These findings may be relevant to ethnic differences in susceptibility to PAD and suggest that therapies directed towards increasing CCL11 may be beneficial in Blacks with PAD.

Abstract 12253: Occludin as a Key Mediator in Adiponectin-Mediated Diabetic Vascular Protection

Background: APN exerts its vascular protective effects through APPL1. However, the downstream target genes that mediate the protective effects of this signaling axis on diabetic vascular endothelium remain unclear. Methods and Results: APPL1knock-out mice were fed normal or high-fat-diet (HFD) for 10 weeks. 8 weeks after HFD, mice were randomized to receive vehicle or APN treatment for another two weeks. Aortic vessels were prepared for transcriptome analysis. Bioinformatics analysis indicates that the Tight Junction (TJ) pathway exhibited the most prominent changes. Using a global signaling transduction network showed that TJ-related genes had the highest degree values. Among these genes, PCR results indicated that Occludin was the sole gene inhibited in endothelial cells treated by HG/HL and promoted by APN treatment in an APPL1-dependent manner. The protein level of Occludin was reduced in diabetic condition, and APN treatment upregulated the expression of Occludin in APPL1-mediated manner in vivo and vitro. Endothelial specific OCLN knockdown blunted APN-mediated blood flow recovery after femoral artery ligation in vivo , and abolished APN’s effects upon HG/HL-induced permeability, and apoptosis in vitro . Mechanically, transcription factor expression and activity assay kits, and mass spectrometry techniques were employed to identify transcription factors involved in mediating the APN/APPL1 signaling axis. Through a comprehensive analysis, we discovered MYB, HDAC1, and FOXO1 play a role in the regulation of Occludin. This finding was validated by CHIP-QPCR. Western blot analysis revealed that the APN-induced increase in Occludin protein level was abolished after knockdown of MYB and FOXO1. However, knockdown of HDAC1 in endothelial cells did not alter the expression of Occludin mediated by APN. Finally, CHIP-qPCR showed that both MYB and FOXO1 participate in the enrichment of Occludin promoters mediated by APN. Conclusion: Our findings firstly indicate that the APN/APPL1 signaling axis promotes the expression of Occludin through MYB and FOXO1, ultimately exerting a protective effect on vascular endothelium.

FNIP1 abrogation promotes functional revascularization of ischemic skeletal muscle by driving macrophage recruitment

Ischaemia of the heart and limbs attributable to compromised blood supply is a major cause of mortality and morbidity. The mechanisms of functional angiogenesis remain poorly understood, however. Here we show that FNIP1 plays a critical role in controlling skeletal muscle functional angiogenesis, a process pivotal for muscle revascularization during ischemia. Muscle FNIP1 expression is down-regulated by exercise. Genetic overexpression of FNIP1 in myofiber causes limited angiogenesis in mice, whereas its myofiber-specific ablation markedly promotes the formation of functional blood vessels. Interestingly, the increased muscle angiogenesis is independent of AMPK but due to enhanced macrophage recruitment in FNIP1-depleted muscles. Mechanistically, myofiber FNIP1 deficiency induces PGC-1α to activate chemokine gene transcription, thereby driving macrophage recruitment and muscle angiogenesis program. Furthermore, in a mouse hindlimb ischemia model of peripheral artery disease, the loss of myofiber FNIP1 significantly improved the recovery of blood flow. Thus, these results reveal a pivotal role of FNIP1 as a negative regulator of functional angiogenesis in muscle, offering insight into potential therapeutic strategies for ischemic diseases.

Adipose Derived Stromal Vascular Fraction and Mesenchymal Stem Cells Improve Angiogenesis in a Rat Hindlimb Ischaemia Model

This study aimed to investigate the effect of human adipose tissue derived stromal vascular fraction (AD-SVF) and mesenchymal stem cells (AD-MSCs) on blood flow recovery and neovascularisation in a rat hindlimb ischaemia model. SVF was isolated using an automated centrifugal system, and AD-MSCs were obtained from adherent cultures of SVF cells. Rats were divided into four groups of six rats each: non-ischaemia (Group 1); saline treated ischaemia (Group 2); SVF treated ischaemia (Group 3); and AD-MSC treated ischaemia (Group 4). Unilateral hindlimb ischaemia was induced in Sprague-Dawley rats via femoral artery ligation. Saline, SVF, or AD-MSCs were injected intramuscularly into the adductor muscle intra-operatively. Cell viability was calculated as the percentage of live cells relative to total cell number. Blood flow improvement, muscle fibre injury, and angiogenic properties were validated using thermal imaging and histological assessment. The viabilities of SVF and AD-MSCs were 83.3% and 96.7%, respectively. Group 1 exhibited no significant temperature difference between hindlimbs, indicating a lack of blood flow changes. The temperature gradient gradually decreased in SVF and AD-MSC treated rats compared with saline treated rats. In addition, only normal muscle fibres with peripherally located nuclei were observed in Group 1. Groups 3 and 4 exhibited significantly fewer centrally located nuclei, indicating less muscle damage compared with Group 2. Regarding angiogenic properties, CD31 staining of endothelial cells showed similar patterns among all groups, whereas expression of vascular endothelial growth factor, as a crucial angiogenesis factor, was enhanced in the SVF and AD-MSC treated groups. SVF and AD-MSCs improved blood flow and neovascularisation in a rat hindlimb ischaemia model, suggesting their potential ability to promote angiogenesis. Further extensive research is warranted to explore their potential applications in the treatment of severe lower extremity arterial disease.

Endothelial deletion of EPH receptor A4 alters single-cell profile and Tie2/Akap12 signaling to preserve blood–brain barrier integrity

Neurobiological consequences of traumatic brain injury (TBI) result from a complex interplay of secondary injury responses and sequela that mediates chronic disability. Endothelial cells are important regulators of the cerebrovascular response to TBI. Our work demonstrates that genetic deletion of endothelial cell (EC)-specific EPH receptor A4 (EphA4) using conditional EphA4f/f/Tie2-Cre and EphA4f/f/VE-Cadherin-CreERT2 knockout (KO) mice promotes blood-brain barrier (BBB) integrity and tissue protection, which correlates with improved motor function and cerebral blood flow recovery following controlled cortical impact (CCI) injury. scRNAseq of capillary-derived KO ECs showed increased differential gene expression of BBB-related junctional and actin cytoskeletal regulators, namely, A-kinase anchor protein 12, Akap12, whose presence at Tie2 clustering domains is enhanced in KO microvessels. Transcript and protein analysis of CCI-injured whole cortical tissue or cortical-derived ECs suggests that EphA4 limits the expression of Cldn5, Akt, and Akap12 and promotes Ang2. Blocking Tie2 using sTie2-Fc attenuated protection and reversed Akap12 mRNA and protein levels cortical-derived ECs. Direct stimulation of Tie2 using Vasculotide, angiopoietin-1 memetic peptide, phenocopied the neuroprotection. Finally, we report a noteworthy rise in soluble Ang2 in the sera of individuals with acute TBI, highlighting its promising role as a vascular biomarker for early detection of BBB disruption. These findings describe a contribution of the axon guidance molecule, EphA4, in mediating TBI microvascular dysfunction through negative regulation of Tie2/Akap12 signaling.

Impaired post-stroke collateral circulation in sickle cell anemia mice.

Patients with sickle cell anemia (SCA) have a high incidence of ischemic stroke, but are usually excluded from thrombolytic therapy due to concerns for cerebral hemorrhage. Maladaptation to cerebral ischemia may also contribute to the stroke propensity in SCA. Here we compared post-stroke cortical collateral circulation in transgenic sickle (SS) mice, bone marrow grafting-derived SS-chimera, and wildtype (AA) controls, because collateral circulation is a critical factor for cell survival within the ischemic penumbra. Further, it has been shown that SS mice develop poorer neo-collateral perfusion after limb ischemia. We used the middle cerebral artery (MCA)-targeted photothrombosis model in this study, since it is better tolerated by SS mice and creates a clear infarct core versus peri-infarct area. Compared to AA mice, SS mice showed enlarged infarction and lesser endothelial proliferation after photothrombosis. SS-chimera showed anemia, hypoxia-induced erythrocyte sickling, and attenuated recovery of blood flow in the ipsilateral cortex after photothrombosis. In AA chimera, cerebral blood flow in the border area between MCA and the anterior cerebral artery (ACA) and posterior cerebral artery (PCA) trees improved from 44% of contralateral level after stroke to 78% at 7 d recovery. In contrast, blood flow in the MCA-ACA and MCA-PCA border areas only increased from 35 to 43% at 7 d post-stroke in SS chimera. These findings suggest deficits of post-stroke collateral circulation in SCA. Better understanding of the underpinnings may suggest novel stroke therapies for SCA patients.

Differential relationship between decreased muscle oxygenation and blood pressure recovery during supraventricular and ventricular tachycardia

Vasoconstriction during tachyarrhythmia contributes to maintenance of arterial pressure (AP) by decreasing peripheral blood flow. This cross-sectional observational study aimed to ascertain whether the relationship between peripheral blood flow and AP recovery occurs during both paroxysmal supraventricular (PSVT, n = 19) and ventricular tachycardias (VT, n = 17). Peripheral blood flow was evaluated using forearm tissue oxygen index (TOI), and mean AP (MAP) was measured using a catheter inserted in the brachial or femoral artery during an electrophysiological study. PSVT and VT rapidly decreased MAP with a comparable heart rate (P = 0.194). MAP recovered to the baseline level at 40 s from PSVT onset, but not VT. The forearm TOI decreased during both tachyarrhythmias (P ≤ 0.029). The TOI response was correlated with MAPrecovery (i.e., MAP recovery from the initial rapid decrease) at 20–60 s from PSVT onset (r = -– 0.652 to – 0.814, P ≤ 0.0298); however, this association was not observed during VT. These findings persisted even after excluding patients who had taken vasoactive drugs. Thus, restricting peripheral blood flow was associated with MAP recovery during PSVT, but not VT. This indicates that AP recovery depends on the type of tachyarrhythmia: different cardiac output and/or vasoconstriction ability during tachyarrhythmia.

Selective ROCK Inhibitor Enhances Blood Flow Recovery after Hindlimb Ischemia.

The impairment in microvascular network formation could delay the restoration of blood flow after acute limb ischemia. A high-content screen of a GSK-published kinase inhibitor library identified a set of ROCK inhibitor hits enhancing endothelial network formation. Subsequent kinase activity profiling against a panel of 224 protein kinases showed that two indazole-based ROCK inhibitor hits exhibited high selectivity for ROCK1 and ROCK2 isoforms compared to other ROCK inhibitors. One of the chemical entities, GSK429286, was selected for follow-up studies. We found that GSK429286 was ten times more potent in enhancing endothelial tube formation than Fasudil, a classic ROCK inhibitor. ROCK1 inhibition by RNAi phenocopied the angiogenic phenotype of the GSK429286 compound. Using an organotypic angiogenesis co-culture assay, we showed that GSK429286 formed a dense vascular network with thicker endothelial tubes. Next, mice received either vehicle or GSK429286 (10 mg/kg i.p.) for seven days after hindlimb ischemia induction. As assessed by laser speckle contrast imaging, GSK429286 potentiated blood flow recovery after ischemia induction. At the histological level, we found that GSK429286 significantly increased the size of new microvessels in the regenerating areas of ischemic muscles compared with vehicle-treated ones. Our findings reveal that selective ROCK inhibitors have in vitro pro-angiogenic properties and therapeutic potential to restore blood flow in limb ischemia.

Dapagliflozin promotes angiogenesis in hindlimb ischemia mice by inducing M2 macrophage polarization.

Critical limb ischemia (CLI) is associated with a higher risk of limb amputation and cardiovascular death. Dapagliflozin has shown great potential in the treatment of cardiovascular disease. However, the effects of dapagliflozin on CLI and the underlying mechanisms have not been fully elucidated. We evaluated the effect of dapagliflozin on recovery from limb ischemia using a mouse model of hindlimb ischemia. The flow of perfusion was evaluated using a laser Doppler system. Tissue response was assessed by analyzing capillary density, arterial density, and the degree of fibrosis in the gastrocnemius muscle. Immunofluorescence and Western blot were used to detect the expression of macrophage polarization markers and inflammatory factors. Our findings demonstrate the significant impact of dapagliflozin on the acceleration of blood flow recovery in a hindlimb ischemia mouse model, concomitant with a notable reduction in limb necrosis. Histological analysis revealed that dapagliflozin administration augmented the expression of key angiogenic markers, specifically CD31 and α-SMA, while concurrently mitigating muscle fibrosis. Furthermore, our investigation unveiled dapagliflozin's ability to induce a phenotypic shift of macrophages from M1 to M2, thereby diminishing the expression of inflammatory factors, including IL-1β, IL-6, and TNF-α. These effects were partially mediated through modulation of the NF-κB signaling pathway. Lastly, we observed that endothelial cell proliferation, migration, and tube-forming function are enhanced in vitro by utilizing a macrophage-conditioned medium derived from dapagliflozin treatment. Taken together, our study provides evidence that dapagliflozin holds potential as an efficacious therapeutic intervention in managing CLI by stimulating angiogenesis, thereby offering a novel option for clinical CLI treatment.