Mouse Hindlimb Ischemia Research Articles

In-situ engineering of native extracellular matrix to improve vascularization and tissue regeneration at the ischemic injury site

Ischemic injury causes dynamic damage to the native extracellular matrix (ECM), which plays a key role in tissue homeostasis and regeneration by providing structural support, facilitating force transmission, and transducing key signals to cells. The main approach aimed at repairing injury to ischemic tissues is restoration of vascular function. Due to their potential to form capillary niches, endothelial cells (ECs) are of greatest interest for vascular regeneration. Integrin binding to ECM is crucial for cell anchorage to the surrounding matrix, spreading, migration, and further activation of intracellular signaling pathways. In this study, we proposed to establish an in-situ engineering strategy to remodel the ECM at the ischemic site to guide EC endogenous binding and establish effective EC/ECM interactions to promote revascularization. We designed and constructed a dual-function molecule (LXW7)2-SILY, which is comprised of two functional domains: the first one (LXW7) binds to integrin αvβ3 expressed on ECs, and the second one (SILY) binds to collagen. In vitro, we confirmed (LXW7)2-SILY improved EC adhesion and survival. After in situ injection, (LXW7)2-SILY showed stable retention at the injured area and promoted revascularization, blood perfusion, and tissue regeneration in a mouse hindlimb ischemia model.Graphical

Insulin-like growth factor-2 mRNA-binding protein 2 facilitates post-ischemic angiogenesis by increasing the stability of fibroblast growth factor 2 mRNA and its protein expression

BackgroundPost-ischemic angiogenesis is crucial for reestablishing blood flow in conditions such as peripheral artery disease (PAD). The role of insulin-like growth factor-2 mRNA-binding protein 2 (IGF2BP2) in post-transcriptional RNA metabolism and its involvement in post-ischemic angiogenesis remains unclear. MethodsUsing a human GEO database and a hind-limb ischemia (HLI) mouse model, the predominant isoform IGF2BP2 in ischemic gastrocnemius tissue was identified. Adeno-associated virus with the Tie1 promoter induced IGF2BP2 overexpression in the HLI model, evaluating the expression of vascular structural proteins (CD31 and α-SMA) and blood flow recovery after HLI. In vitro experiments with human umbilical vein endothelial cells (HUVECs) demonstrated that lentivirus-mediated IGF2BP2 overexpression upregulates cell proliferation, migration, and tube formation. GeneCards, RNAct databases, and subsequent reverse transcription quantitative polymerase chain reaction (RT-qPCR) predicted IGF2BP2 interactions with fibroblast growth factor 2 (FGF2) mRNA, and actinomycin D treatment, binding site predictions and CLIP-seq data further confirmed this interaction. Furthermore, western blotting, enzyme-linked immunosorbent assay, and RNA immunoprecipitation followed by RT-qPCR were performed to validate IGF2BP2's interaction with FGF2 mRNA and to assess its role in stabilizing FGF2 mRNA, as well as its impact on FGF2 protein expression. ResultsHLI reduced IGF2BP2 expression in the gastrocnemius tissue, which gradually increased during blood flow recovery. IGF2BP2 overexpression in HLI mice accelerated blood flow recovery and increased capillary and small artery densities. The overexpression of IGF2BP2 in HUVECs stimulated proliferation, migration, and tube formation by interacting with FGF2 mRNA to increase its stability. This interaction resulted in increased levels of FGF2 protein and secretion, ultimately promoting angiogenesis. ConclusionsIGF2BP2 contributes to blood flow restoration post-ischemia in vivo and promotes angiogenesis in HUVECs by enhancing FGF2 mRNA stability and FGF2 protein expression and secretion. These findings underscore IGF2BP2's therapeutic potential in ischemic conditions, such as PAD.

Abstract Tu023: The VEGF-A splice variants as a mechanism of impaired Inflammatory Angiogenesis in the context of advanced aging.

Background and Objectives: Aging and age-related diseases like peripheral artery disease (PAD) is associated with impairment of angiogenesis responses to injury. Critical ischemic limb and wound injury animal models have shown impact of monocytes/macrophages as a major source of angiogenic mediators leading to new arterial growth. Aging has also been associated with impairment of blood flow recovery and reduced VEGF-A expression in animals. However, recombinant VEGF-A administration or clinical trials involving VEGF-A have not fully overcome the foot perfusion and prevent limb/leg amputation. We sought to understand molecular mechanisms of reduced VEGF-A expression which remain incomplete in the context of advanced aging. Results: Firstly, in hindlimb ischemia mouse model, our data from liposomes containing-clodronate treated mice (12-weeks C57Bl6 with macrophage depletion model ) ( Fig. 1a ) demonstrate impairment of blood flow recovery compared to Control group. On day 3 post-surgery, VEGF-A and VEGF-A isoforms expression (VEGF-A 165 a and VEGF-A 165 b, respectively) were reduced in ischemic muscle. Fluorescence staining showed a reduction of macrophages (CD68 + ) was also associated with reduced endothelial cells (CD31 + ). Using a myeloid-specific and inducible deleted VEGF fl/fl mice, we then have shown a key role of early inflammatory macrophages stage as a major source of VEGF-A required for angiogenesis in young mice (Fig. 1b). Secondly, bone marrow-derived-macrophages (BMDMs) from C57Bl6 104-weeks mice also demonstrate reduced VEGF-A expression. Aged BMDMs demonstrate reduced VEGF-A 165 a while VEGF-A 165 b was highly increased. Polarized BMDMs from 12-weeks demonstrate increased VEGFR1 in “M2" macrophages while VEGFR2 was increased in “M1” macrophages. On the other hand, BMDMs from 104-weeks demonstrate reduced VEGFR2 expression while VEGFR1 was unaffected compared to young. Lastly, 104-weeks mice also demonstrate severe impairment of blood flow recovery ( Fig. 2 ) after surgery and reduced VEGF-A and VEGF-A 165 a in ischemic muscle tissue. VEGF-A 165 b was increased and both receptors, VEGF-R1/R2 levels ( Fig. 3 ) were also reduced. Fluorescence staining on day 3 post ligation demonstrates reduced endothelial cells recruitment in muscle tissue while macrophage (CD68+) number was similar. Conclusion: Our investigations will contribute to define mechanisms whereby vascular injury is associated with VEGF-A isoforms specific switch in the context of advanced aging.

IL-28A/IL-10Rβ axis promotes angiogenesis via eNOS/AKT signaling and AP-1/NF-κB/MMP-2 network by regulating HSP70-1 expression

IntroductionAngiogenesis plays a significant role in the development of tumor progression and inflammatory diseases. The role of IL-28A in angiogenesis and its precise regulatory mechanisms remain rarely elucidated. ObjectivesWe report the novel regulatory role of IL-28A in physiological angiogenesis. The study aimed to elucidate the regulatory mechanisms involved in IL-28A-mediated angiogenesis and identify key genes associated with IL-28A-induced angiogenic responses. MethodsTo know the effect of IL-28A on angiogenesis, HUVECs were applied to perform proliferation, migration, invasion, tube formation, immunoblot, and EMSA. Gene expression changes in HUVECs following IL-28A treatment were analyzed by NGS. The functional role of HSP70-1 and IL-10Rβ in IL-28A-induced angiogenic responses was evaluated using PCR and siRNA knockdown. Animal studies were conducted by aortic ring ex vivo assays, Matrigel plug in vivo assays, and immunochemistry using HSP70-1 knockout and transgenic mice models. The efficacy of IL-28A in angiogenesis was confirmed in a hind-limb ischemia model. ResultsAutocrine/paracrine actions in HUVECs regulated IL-28A protein expression. Exogenous IL-28A increased the proliferation of HUVECs via eNOS/AKT and ERK1/2 signaling. IL-28A treatment promoted migration, invasion, and capillary tube formation of HUVECs through induction of the AP-1/NF-κB/MMP-2 network, which was associated with eNOS/AKT and ERK1/2 signaling. The efficacy of IL-28A-induced angiogenic potential was confirmed by aortic ring and Matrigel plug assay. HSP70-1 was identified as an IL-28A-mediated angiogenic effector gene using bioinformatics. Knockdown of HSP70-1 abolished angiogenic responses and eNOS/AKT signaling in IL-28A-treated HUVECs. IL-28A-induced microvessel sprouting formation was testified in HSP70-1-deficient and HSP70-1 transgenic mice. Flow recovery in hind-limb ischemia mice was accelerated by IL-28A injection. Finally, ablation of the IL-10Rβ gene impeded the angiogenic responses and eNOS/AKT signaling stimulated by IL-28A in HUVECs. ConclusionHSP70-1 drives the progression of angiogenesis by the IL-28A/IL-10Rβ axis via eNOS/AKT signaling and the AP-1/NF-κB/MMP-2 network.

The Inhibition of γ-Aminobutyric Acid B1 Receptor Regulates Angiogenesis via the Hippo/YAP Signaling Pathway

Promoting the establishment of collateral circulation is essential for chronic lower extremity ischemia. However, no effective therapeutic drugs have yet been developed. Recent studies discovered that in the peripheral arteries, there are GABAB1 receptors expressed in endothelial cells and smooth muscle cells, these receptors may have some effects in regulating vascular functions, but the precise mechanism is not yet clear. This study explores the effect of GABAB1 receptor inhibition on angiogenesis and its regulatory mechanism. The expression of GABAB1 in HUVECs was knocked down using shRNA transfection, and effects in HUVECs' proliferation, migration, and tube formation ability were detected. Western blot and RT-PCR were used to verify the signal pathway. The murine hind limb ischemia model was used to verify the effect of CGP35348, an antagonist of GABAB1R, on the recovery of blood flow perfusion and angiogenesis in ischemic tissues. Cell proliferation, migration, and tube formation ability were improved after GABAB1 receptor knockdown in HUVECs. The phosphorylation of the HIPPO/YAP pathway decreased, while the effect of promoting angiogenesis increased. After treating the ischemic hindlimbs of mice with GABAB1 receptor antagonists, the blood flow perfusion recovered, and the angiogenesis increased. These findings demonstrate the effect of GABAB1 receptor inhibition on the HIPPO/YAP pathway in regulating angiogenesis, suggesting that inhibiting GABAB1 receptor levels might be a novel approach for chronic lower extremity ischemia diseases.

An Endocellulase-Triggered NO Targeted-Release Enzyme-Prodrug Therapy System and Its Application in Ischemia Injury.

Nitric oxide (NO) is a crucial gaseous signaling molecules in regulating cardiovascular, immune, and nervous systems. Controlled and targeted NO delivery is imperative for treating cancer, inflammation, and cardiovascular diseases. Despite various enzyme-prodrug therapy (EPT) systems facilitating controlled NO release, their clinical utility is hindered by nonspecific NO release and undesired metabolic consequence. In this study, a novel EPT system is presented utilizing a cellobioside-diazeniumdiolate (Cel2-NO) prodrug, activated by an endocellulase (Cel5A-h38) derived from the rumen uncultured bacterium of Hu sheep. This system demonstrates nearly complete orthogonality, wherein Cel2-NO prodrug maintains excellent stability under endogenous enzymes. Importantly, Cel5A-h38 efficiently processes the prodrug without recognizing endogenous glycosides. The targeted drug release capability of the system is vividly illustrated through an in vivo near-infrared imaging assay. The precise NO release by this EPT system exhibits significant therapeutic potential in a mouse hindlimb ischemia model, showcasing reductions in ischemic damage, ambulatory impairment, and modulation of inflammatory responses. Concurrently, the system enhances tissue repair and promotes function recovery efficacy. The novel EPT system holds broad applicability for the controlled and targeted delivery of essential drug molecules, providing a potent tool for treating cardiovascular diseases, tumors, and inflammation-related disorders.

Biomimetic nanocomposite cryogel with enhanced peptide binding promotes therapeutic angiogenesis and bone regeneration

The effective regeneration of large bone defects faces a significant hurdle, primarily due to inadequate vascularization. This study explores the potential of enhancing vascularization and bone regeneration by incorporating whitlockite nanoparticles (nWH; Ca18Mg2(HPO4)2(PO4)12) and WKYMVm (W) peptide into a gelatin-sulfated hyaluronic acid (WH10-W) cryogel. The developed cryogels showed an average pore size of 70 μm. Further, they were characterized for degradation rate, swelling ratio, mechanical and rheological properties. The WH10-W group exhibited sustained release of the W peptide, in contrast to the rapid release observed from gelatin-hyaluronic acid. In silico binding studies revealed that the binding of the W peptide was dependent on the sulfation degree in hyaluronic acid. The prepared cryogels were cytocompatible. The combinatorial group (WH10-W) demonstrated superior pro-angiogenic compared to cryogel with only nWH or W peptide, as seen from tube formation assay, scratch test and gene expression studies. In addition, WH10-W enhanced the osteogenic differentiation as seen from the osteogenic gene expression, ALP and alizarin red s staining. Finally, mouse hind limb ischemia model demonstrated enhanced angiogenic potential, while a mouse cranial defect study showed increased new bone formation in the WH10-W group compared to all other groups. These findings suggest a promising strategy for addressing large non-load bearing bone defects.

Novel cell therapy with ex vivo cultured peripheral blood mononuclear cells significantly impacts angiogenesis in the murine ischemic limb model

IntroductionAutologous mononuclear cells (MNCs) have been used in vascular regenerative therapy since the identification of endothelial progenitor cells (EPCs). However, the efficacy of autologous EPC therapy for diseases such as diabetes and connective tissue disorders is limited due to deficiencies in the number and function of EPCs. To address this, we developed a novel RE-01 cells that enriches pro-angiogenic cells from peripheral blood MNCs (PBMNCs). MethodsPBMNCs were collected from healthy volunteers following ethical guidelines. RE-01 cells were cultured in the presence of specific growth factors for 5 days without media change. Flow cytometry was used to analyze cell surface markers. Tube formation assays, EPC culture assays, and mRNA analysis were performed to evaluate angiogenic potential. The efficacy of RE-01 cells upon transplantation into ischemic hind limbs of mice was evaluated. ResultsRE-01 cells exhibited a significant increase in pro-angiogenic cells such as M2 macrophages and angiogenic T cells, in contrast to PBMNCs, while the number of inflammatory cells reduced. In vitro assays demonstrated the enhanced angiogenic abilities of RE-01 cells, supported by increased mRNA expression of angiogenesis-related cytokines. In vivo studies using mouse ischemic hind limb models have shown that blood flow and angiogenesis improved following RE-01 cell transplantation. Transplantations for 3 consecutive days significantly improved the number of pericyte-recruited vessels in the severely ischemic hind limbs of mice. ConclusionsRE-01 cells showed promising results in enhancing angiogenesis and arteriogenesis, possibly owing to the presence of M2 macrophages and angiogenic T cells. These cells also demonstrated anti-fibrotic effects. The efficacy of RE-01 cells has been confirmed in mouse models, suggesting their potential for treating ischemic vascular diseases. Clinical trials are planned to validate the safety and efficacy of RE-01 cell therapy in patients with connective tissue disease and unhealed ulcers. We hope that this new RE-01 cell therapy will prevent many patients from undergoing amputation.

Senescence induces miR-409 to down-regulate CCL5 and impairs angiogenesis in endothelial progenitor cells.

This study explores the impact of senescence on autocrine C-C motif chemokine ligand 5 (CCL5) in human endothelial progenitor cell (EPCs), addressing the poorly understood decline in number and function of EPCs during ageing. We examined the effects of replication-induced senescence on CCL5/CCL5 receptor (CCR5) signalling and angiogenic activity of EPCs invitro and invivo. We also explored microRNAs controlling CCL5 secretion in senescent EPCs, its impact on EPC angiogenic activity, and validated our findings in humans. CCL5 secretion and CCR5 levels in senescent EPCs were reduced, leading to attenuated angiogenic activity. CCL5 enhanced EPC proliferation via the CCR5/AKT/P70S6K axis and increased vascular endothelial growth factor (VEGF) secretion. Up-regulation of miR-409 in senescent EPCs resulted in decreased CCL5 secretion, inhibiting the angiogenic activity, though these negative effects were counteracted by the addition of CCL5 and VEGF. In a mouse hind limb ischemia model, CCL5 improved the angiogenic activity of senescent EPCs. Analysis involving 62 healthy donors revealed a negative association between CCL5 levels, age and Framingham Risk Score. These findings propose CCL5 as a potential biomarker for detection of EPC senescence and cardiovascular risk assessment, suggesting its therapeutic potential for age-related cardiovascular disorders.

UFM1 inhibits hypoxia-induced angiogenesis via promoting proteasome degradation of HIF-1α.

Angiogenesis is crucial for blood flow recovery and ischemic tissue repair of peripheral artery disease (PAD). Exploration of new mechanisms underlying angiogenesis will shed light on the treatment of PAD. Ubiquitin-fold modifier 1 (UFM1), a newly identified ubiquitin-like molecule, has been discovered to be involved in various pathophysiological processes. However, the role of UFM1 in the pathogenesis of PAD, especially in endothelial angiogenesis remains obscure, and we aimed to clarify this issue in this study. We initially found UFM1 was significantly upregulated in gastrocnemius muscles of PAD patients and hind limb ischemia mice. And UFM1 was mainly colocalized with endothelial cells in ischemic muscle tissues. Further, elevated expression of UFM1 was observed in hypoxic endothelial cells. Subsequent genetic inhibition of UFM1 dramatically enhanced migration, invasion, adhesion, and tube formation of endothelial cells under hypoxia. Mechanistically, UFM1 reduced the stability of hypoxia-inducible factor-1α (HIF-1α) and promoted the von Hippel-Lindau-mediated K48-linked ubiquitin-proteasome degradation of HIF-1α, which in turn decreased angiogenic factor VEGFA expression and suppressed VEGFA related signaling pathway. Consistently, overexpression of UFM1 inhibited the angiogenesis of endothelial cells under hypoxic conditions, whereas overexpression of HIF-1α reversed this effect. Collectively, our data reveal that UFM1 inhibits the angiogenesis of endothelial cells under hypoxia through promoting ubiquitin-proteasome degradation of HIF-1α, suggesting UFM1 might serve as a potential therapeutic target for PAD.

Abstract 2005: Interrogating The Cross-talk: Endothelial-Macrophage Interactions In Diabetic Vascular Dysfunction

Cardiovascular disease (CVD) occurs 15 years earlier in diabetics compared to those without, but the underlying mechanisms driving diabetes-accelerated CVDs (DACVDs) pathogenesis remains incompletely understood. Endothelial cells (ECs) and macrophages (MΦ) are key players in vascular wall and their crosstalk is crucial in DACVD. In diabetes, ECs activation enables monocytes recruitment, which transmigrate across the intima and differentiate into macrophages (MΦ). Beyond this established diapedesis model, EC-MΦ interplay is highly intricate and heterogenous. Here, we leveraged human mesenteric arteries of varied diabetic state and used single cell (sc)- and spatial transcriptome mapping to interrogate the functional crosstalk between MΦ subtypes and ECs in diabetes. We identified diabetes-induced EC-MΦ interactions and explored their consequences in vitro and in vivo, in peripheral artery disease (PAD), a prominent DACVD. Integrative scRNA-seq and spatial transcriptome (Visium) profiling identified a remarkable increase of MΦ subtype expressing triggering receptor expressed on myeloid cells (TREM2) with concomitant increased EC-derived TREM2 ligands in human diabetic vs non-diabetic vessels. Such induction of TREM2 MΦ was consistently observed in arteries from type I and II diabetes mouse models. Compared to the condition medium from MΦ cultured under normal glucose, that from MΦ cultured under high glucose conditions reduced EC migration and increased inflammatory markers, which were reversed by the medium from MΦ with TREM2-knockdown. We further evaluated the functional importance of EC-TREM2 interaction in vivo in a mouse hindlimb ischemia (HLI) model. In diabetic mice under HLI, a TREM2 neutralizing antibody promoted tissue recovery and perfusion. Finally, we showed that TREM2 was increased, especially in proximity to ECs, in ischemic sites, as compared to non-ischemic regions in limb muscles from human PAD patients.Taken together, our study presents a diabetic artery atlas and identifies EC-TREM2 interaction as a crucial event in DACVDs, such as PAD. Our findings provide novel insights into the EC-MΦ interplay in diabetes and vascular inflammation and how these cellular interactions may be targeted to ameliorate DACVD.

Abstract 1142: Effect Of Chronic E-cigarette Nicotine Exposure On A Mouse Model Of Hind-limb Ischemia

Background: The rise of e-cigarette use in the United States has been rapid, yet its impact on peripheral artery disease (PAD) remains largely unexplored. This study investigates the relationship between e-cigarette use and PAD using a mouse ischemic hindlimb model. Method: Mice aged 6-8 weeks were divided into four groups. Three groups inhaled e-cigarette vapor continuously for 14, 20, or 28 days prior, and for 28 days after hindlimb ischemia (HLI) surgery, using an InExpose system (Figure 1). A control group was exposed to room air (RA) before and after HLI. Laser-Doppler perfusion imaging tracked hindlimb blood flow, and functional deficits were assessed using the modified ischemia scale. Figure 1: Methodology Results: Blood perfusion in the ischemic hindlimb of the e-cigarette groups (EC-14, EC-20, EC-28) was significantly lower than the non-vaping group at 21 days post-surgery. In the EC-14 group, perfusion improved after 10 days of vaping cessation (Figure 2). Additionally, there was a reduction in platelet and leukocyte counts in the e-cigarette groups compared to RA, with no difference in red blood cells. Necrosis and claw damage were observed in EC-20 and EC-28 groups but not in non-vaping mice. Figure 2: Representative images of perfusion recovery measured by LDPI. Conclusion: Chronic e-cigarette nicotine exposure impairs blood flow recovery and causes necrosis in mice with hind limb ischemia, potentially due to perturbed angiogenesis and arteriogenesis. This study highlights the detrimental effects of e-cigarette nicotine on vascular health.

Endothelial ELABELA improves post-ischemic angiogenesis by upregulating VEGFR2 expression

BackgroundPost-ischemic angiogenesis is critical for perfusion recovery and tissue repair. ELABELA (ELA) plays an essential role in embryonic heart development and vasculogenesis. However, the mechanism of ELA on post-ischemic angiogenesis is poorly characterized. MethodsWe first assessed ELA expression after hind limb ischemia (HLI) in mice. We then established a HLI model in tamoxifen-inducible endothelial-ELA-specific knockout mice (ELAECKO) and assessed the rate of perfusion recovery, capillary density, and VEGFR2 pathway. Knockdown of ELA with lentivirus or siRNA and exogenous addition of ELA peptides were employed to analyze the effects of ELA on angiogenic capacity and VEGFR2 pathway in endothelial cells in vitro. The serum levels of ELA in healthy people and patients with type 2 diabetes mellitus (T2DM) and diabetic foot ulcer (DFU) were detected by a commercial ELISA kit. ResultsIn murine HLI models, ELA was significantly up-regulated in the ischemic hindlimb. Endothelial-specific deletion of ELA impaired perfusion recovery and angiogenesis. In physiologic conditions, no significant difference in VEGFR2 expression was found between ELAECKO mice and ELAWT mice. After ischemia, the expression of VEGFR2, p-VEGFR2, and p-AKT was significantly lower in ELAECKO mice than in ELAWT mice. In cellular experiments, the knockdown of ELA inhibited endothelial cell proliferation and tube formation, and the addition of ELA peptides promoted proliferation and tube formation. Mechanistically, ELA upregulated the expression of VEGFR2, p-VEGFR2, and p-AKT in endothelial cells under hypoxic conditions. In clinical investigations, DFU patients had significantly lower serum levels of ELA compared to T2DM patients. ConclusionOur results indicated that endothelial ELA is a positive regulator of post-ischemic angiogenesis via upregulating VEGFR2 expression. Targeting ELA may be a potential therapeutic option for peripheral arterial diseases.

Engineering M2-type macrophages with a metal polyphenol network for peripheral artery disease treatment

Functional cell treatment for critical limb ischemia is limited by cell viability loss and dysfunction resulting from a harmful ischemic microenvironment. Metal-polyphenol networks have emerged as novel cell delivery vehicles for protecting cells from the detrimental ischemic microenvironment and prolonging the survival rate of cells in the ischemic microenvironment. M2 macrophages are closely related to tissue repair, and they secrete anti-inflammatory factors that contribute to lesion repair. However, these cells are easily metabolized in the body with low efficiency. Herein, M2 macrophages were decorated with a metal‒polyphenol network that contains copper ions and epigallocatechin gallate (Cu-EGCG@M2) to increase cell survival and therapeutic potential. Cu-EGCG@M2 synergistically promoted angiogenesis through the inherent angiogenesis effect of M2 macrophages and copper ions. We found that Cu-EGCG@M2 increased in vitro viability and strengthened the in vivo therapeutic effect on the ischemic hindlimbs of mice, which promoted the recovery of blood and muscle regeneration, resulting in superior limb salvage. These therapeutic effects were ascribed to the increased survival rate and therapeutic period of M2 macrophages, as well as the ameliorated microenvironment at the ischemic site. Additionally, Cu-EGCG exhibited antioxidant, anti-inflammatory, and proangiogenic effects. Our findings provide a feasible option for cell-based treatment of CLI.

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.

Role of toll-like receptor 4 in skeletal muscle damage in chronic limb-threatening ischemia

ObjectiveToll-like receptors (TLRs) are key pattern recognition receptors in the innate immune system. In particular, the TLR4-mediated immune response has been implicated in ischemia-induced tissue injury. Mounting evidence supports a detrimental role of the innate immune system in the pathophysiology of skeletal muscle damage in patients with chronic limb-threatening ischemia (CLTI), in whom patient-oriented functional outcomes are poor. The overall aim of this study was to investigate the potential role of TLR4 in skeletal muscle dysfunction and damage in CLTI. MethodsThe role of TLR4 in ischemic muscle was investigated by (1) studying TLR4 expression and distribution in human gastrocnemius muscle biopsies, (2) evaluating the functional consequences of TLR4 inhibition in myotubes derived from human muscle biopsies, and (3) assessing the therapeutic potential of modulating TLR4 signaling in ischemic muscle in a mouse hindlimb ischemia model. ResultsTLR4 was found to be expressed in human muscle biopsies, with significant upregulation in samples from patients with CLTI. In vitro studies using cultured human myotubes demonstrated upregulation of TLR4 in ischemia, with activation of the downstream signaling pathway. Inhibition of TLR4 before ischemia was associated with reduced ischemia-induced apoptosis. Upregulation of TLR4 also occurred in ischemia in vivo and TLR4 inhibition was associated with decreased inflammatory cell infiltration and diminished apoptosis in the ischemic limb. ConclusionsTLR4 is upregulated and activated in ischemic skeletal muscle in patients with CLTI. Modulating TLR4 signaling in vitro and in vivo was associated with attenuation of ischemia-induced skeletal muscle damage. This strategy could be explored further for potential clinical application.

Adipose-Derived Mesenchymal Stem Cells Protect Endothelial Cells from Hypoxic Injury by Suppressing Terminal UPR In Vivo and In Vitro.

Adipose-derived stem cells (ASCs) have been used as a therapeutic intervention for peripheral artery disease (PAD) in clinical trials. To further explore the therapeutic mechanism of these mesenchymal multipotent stromal/stem cells in PAD, this study was designed to test the effect of xenogeneic ASCs extracted from human adipose tissue on hypoxic endothelial cells (ECs) and terminal unfolded protein response (UPR) in vitro and in an atherosclerosis-prone apolipoprotein E-deficient mice (ApoE-/- mice) hindlimb ischemia model in vivo. ASCs were added to Cobalt (II) chloride-treated ECs; then, metabolic activity, cell migration, and tube formation were evaluated. Fluorescence-based sensors were used to assess dynamic changes in Ca2+ levels in the cytosolic- and endoplasmic reticulum (ER) as well as changes in reactive oxygen species. Western blotting was used to observe the UPR pathway. To simulate an acute-on-chronic model of PAD, ApoE-/- mice were subjected to a double ligation of the femoral artery (DLFA). An assessment of functional recovery after DFLA was conducted, as well as histology of gastrocnemius. Hypoxia caused ER stress in ECs, but ASCs reduced it, thereby promoting cell survival. Treatment with ASCs ameliorated the effects of ischemia on muscle tissue in the ApoE-/- mice hindlimb ischemia model. Animals showed less muscle necrosis, less inflammation, and lower levels of muscle enzymes after ASC injection. In vitro and in vivo results revealed that all ER stress sensors (BIP, ATF6, CHOP, and XBP1) were activated. We also observed that the expression of these proteins was reduced in the ASCs treatment group. ASCs effectively alleviated endothelial dysfunction under hypoxic conditions by strengthening ATF6 and initiating a transcriptional program to restore ER homeostasis. In general, our data suggest that ASCs may be a meaningful treatment option for patients with PAD who do not have traditional revascularization options.

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.

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.

Synergistic Therapeutic Potential of Dual 3D Mesenchymal Stem Cell Therapy in an Ischemic Hind Limb Mouse Model.

Three-dimensional (3D) culture systems have been widely used to promote the viability and metabolic activity of mesenchymal stem cells (MSCs). The aim of this study was to explore the synergistic benefits of using dual 3D MSC culture systems to promote vascular regeneration and enhance therapeutic potential. We used various experimental assays, including dual 3D cultures of human adipose MSCs (hASCs), quantitative reverse transcription polymerase chain reaction (qRT-PCR), in vitro cell migration, Matrigel tube network formation, Matrigel plug assay, therapeutic assays using an ischemic hind limb mouse model, and immunohistochemical analysis. Our qRT-PCR results revealed that fibroblast growth factor 2 (FGF-2), granulocyte chemotactic protein-2 (GCP-2), and vascular endothelial growth factor-A (VEGF-A) were highly upregulated in conventional 3D-cultured hASCs (ASC-3D) than in two-dimensional (2D)-cultured hASCs. Hepatocyte growth factor (HGF), insulin-like growth factor-1 (IGF-1), and stromal-cell-derived factor-1 (SDF-1) showed higher expression levels in cytokine-cocktail-based, 3D-cultured hASCs (ASC-3Dc). A conditioned medium (CM) mixture of dual 3D ASCs (D-3D; ASC-3D + ASC-3Dc) resulted in higher migration and Matrigel tube formation than the CM of single 3D ASCs (S-3D; ASC-3D). Matrigel plugs containing D-3D contained more red blood cells than those containing S-3D. D-3D transplantation into ischemic mouse hind limbs prevented limb loss and augmented blood perfusion when compared to S-3D transplantation. Transplanted D-3D also revealed a high capillary density and angiogenic cytokine levels and transdifferentiated into endothelial-like cells in the hind limb muscle. These findings highlight the benefits of using the dual 3D culture system to optimize stem-cell-based therapeutic strategies, thereby advancing the therapeutic strategy for ischemic vascular disease and tissue regeneration.