Hind Limbs Of Diabetic Mice Research Articles

Delivery of Therapeutic miRNA via Plasma-Polymerised Nanoparticles Rescues Diabetes-Impaired Endothelial Function.

MicroRNAs (miRNAs) are increasingly recognised as key regulators of the development and progression of many diseases due to their ability to modulate gene expression post-translationally. While this makes them an attractive therapeutic target, clinical application of miRNA therapy remains at an early stage and in part is limited by the lack of effective delivery modalities. Here, we determined the feasibility of delivering miRNA using a new class of plasma-polymerised nanoparticles (PPNs), which we have recently isolated and characterised. We showed that PPN-miRNAs have no significant effect on endothelial cell viability in vitro in either normal media or in the presence of high-glucose conditions. Delivery of a miRNA inhibitor targeting miR-503 suppressed glucose-induced miR-503 upregulation and restored the downstream mRNA expression of CCNE1 and CDC25a in endothelial cells. Subsequently, PPN delivery of miR-503 inhibitors enhanced endothelial angiogenesis, including tubulogenesis and migration, in culture conditions that mimic diabetic ischemia. An intramuscular injection of a PPN-miR-503 inhibitor promoted blood-perfusion recovery in the hindlimb of diabetic mice following surgically induced ischemia, linked with an increase in new blood vessel formation. Together, this study demonstrates the effective use of PPN to deliver therapeutic miRNAs in the context of diabetes.

SGLT2 inhibitor empagliflozin promotes revascularization in diabetic mouse hindlimb ischemia by inhibiting ferroptosis.

Gliflozins are known as SGLT2 inhibitors, which are used to treat diabetic patients by inhibiting glucose reabsorption in kidney proximal tubules. Recent studies show that gliflozins may exert other effects independent of SGLT2 pathways. In this study we investigated their effects on skeletal muscle cell viability and paracrine function, which were crucial for promoting revascularization in diabetic hindlimb ischemia (HLI). We showed that treatment with empagliflozin (0.1-40 μM) dose-dependently increased high glucose (25 mM)-impaired viability of skeletal muscle C2C12 cells. Canagliflozin, dapagliflozin, ertugliflozin, ipragliflozin and tofogliflozin exerted similar protective effects on skeletal muscle cells cultured under the hyperglycemic condition. Transcriptomic analysis revealed an enrichment of pathways related to ferroptosis in empagliflozin-treated C2C12 cells. We further demonstrated that empagliflozin and other gliflozins (10 μM) restored GPX4 expression in high glucose-treated C2C12 cells, thereby suppressing ferroptosis and promoting cell viability. Empagliflozin (10 μM) also markedly enhanced the proliferation and migration of blood vessel-forming cells by promoting paracrine function of skeletal muscle C2C12 cells. In diabetic HLI mice, injection of empagliflozin into the gastrocnemius muscle of the left hindlimb (10 mg/kg, every 3 days for 21 days) significantly enhanced revascularization and blood perfusion recovery. Collectively, these results reveal a novel effect of empagliflozin, a clinical hypoglycemic gliflozin drug, in inhibiting ferroptosis and enhancing skeletal muscle cell survival and paracrine function under hyperglycemic condition via restoring the expression of GPX4. This study highlights the potential of intramuscular injection of empagliflozin for treating diabetic HLI.

LncRNA SNHG15 relieves hyperglycemia-induced endothelial dysfunction via increased ubiquitination of thioredoxin-interacting protein

Numerous studies have revealed that hyperglycemia is a pivotal driver of diabetic vascular complications. However, the mechanisms of hyperglycemia-induced endothelial dysfunction in diabetes remain incompletely understood. This study aims to expound on the underlying mechanism of the endothelial dysfunction induced by hyperglycemia from the perspective of long non-coding RNAs (lncRNA). In this study, a downregulation of SNHG15 was observed in the ischemic hind limb of diabetic mice and high glucose (HG)-treated HUVECs. Functionally, the overexpression of SNHG15 promoted cell proliferation, migration, and tube formation, and suppressed cell apoptosis in HG-treated HUVECs. Mechanistically, SNHG15 reduced thioredoxin-interacting protein (TXNIP) expression by enhancing ITCH-mediated ubiquitination of TXNIP. TXNIP overexpression abrogated the protective effect of lncRNA SNHG15 overexpression on HG-induced endothelial dysfunction. The following experiment further confirmed that SNHG15 overexpression promoted angiogenesis of the ischemic hind limb in diabetic mice. In conclusion, SNHG15 is a novel protector for hyperglycemia-induced endothelial dysfunction via decreasing TXNIP expression.Hyperglycemia is a pivotal driver of vascular complications in diabetes. The present study shows that the long non-coding RNA SNHG15 is downregulated under hyperglycemic conditions. Its overexpression improves hyperglycemia-impaired endothelial dysfunction via reduced expression TXNIP, a thioredoxin-interacting protein. As a novel regulator of endothelial function in diabetes, SNHG15 is a potential therapeutic target for diabetic endothelial dysfunction.

WITHDRAWN: LncRNA SNHG15 relieves hyperglycemia-induced endothelial dysfunction via increasing ubiquitination of thioredoxin-interacting protein

Numerous evidence indicates that hyperglycemia is a pivotal driver of the vascular complications of diabetes. However, the mechanisms of hyperglycemia-induced endothelial dysfunction in diabetes remain incompletely understood. This study aims to expound on the underlying mechanism of the endothelial dysfunction induced by hyperglycemia from the perspective of long non-coding RNAs (lncRNA). Cell proliferation, migration, apoptosis, and tube formation were measured by cell counting kit-8 assay, transwell assay, flow cytometry, and tube formation assay, respectively. RNA pull-down and RNA-binding protein immunoprecipitation were used to detect the interaction between lncRNA SNHG15 and thioredoxin-interacting protein (TXNIP). Co-immunoprecipitation was used to detect the ubiquitination level of TXNIP and the interaction between TXNIP and E3 ubiquitin ligase ITCH. A downregulation of SNHG15 was observed in the ischemic hind limb of diabetic mice and high glucose (HG)-treated HUVECs. Functionally, the overexpression of SNHG15 promoted cell proliferation, migration, and tube formation, and suppressed cell apoptosis in HG-treated HUVECs. Mechanically, SNHG15 reduced TXNIP expression by enhancing ITCH-mediated ubiquitination of TXNIP. TXNIP overexpression abrogated the protective effect of LncRNA SNHG15 overexpression on HG-induced endothelial dysfunction. The following experiment further confirmed that SNHG15 overexpression promoted angiogenesis of the ischemic hind limb in diabetic mice. SNHG15 is a novel protector for hyperglycemia-induced endothelial dysfunction via decreasing TXNIP expression.

Abstract 249: Plasma Exosomes Impair Angiogenesis in Ischemic Hind Limb of Diabetic Mice- Role of Histone Methylation

Background: Critical limb ischemia (CLI) is one of most prevenient cardiovascular disease in diabetic patients. Recent evidence suggests that altered cargo and function of plasma exosomes (plasma-Exo) may play an important role in diabetes-induced cardiovascular complications. Here, we tested the hypotheses that inhibition of exosome biosynthesis/release improves ischemic hind limb (IHL) repair in db/db mice. Methods: Plasma-Exo from db/+ and db/db mice were isolated by density-gradient ultracentrifugation. Unilateral IHL in mice was conducted by ligation of left femoral artery. Blood perfusion in IHL was measured by Laser Doppler Imager. Results: Diabetic plasma-Exo impaired tube formation/migration of human microvascular endothelial cells (HMVECs) and blood perfusion in IHL of C57BL/6J mice. Exosome inhibitor GW4869 improved blood flow, capillary density, cell survival, and rescued necrosis of toe/toenail and fibrosis in IHL muscle of db/db mice. Mechanistically, diabetic plasma-Exo decreased secretion of pro-angiogenic factor Ang I&II, artemin, FGF2 and IGFBP1&2, and increased repressive transcriptional mark H3K27me3 and its methylase enhancer of zest homolog-2 (EZH2) in HMVECs. EZH2 inhibitor GSK343 rescued diabetic plasma-Exo-impaired tube formation and secretion of FGF2/artemin from HMVECs. Moreover, GW4869 reduced EZH2 and H3K27me3 protein expression in lung microvascular ECs of IHL db/db mice. Finally, diabetic plasma-Exo increased H3K27me3 level at promoter of artemin and FGF2. Conclusions: Diabetic plasma-Exo impair angiogenesis and IHL injury repair. Diabetic plasma-Exo impair reparative property of ECs via, at least in part, enhancement of EZH2/H3K27me3/artemin and FGF2 cascade. Inhibition of plasma-Exo biosynthesis/secretion improve IHL repair in db/db mice. Plasma-Exo may be a novel target for prevention/treatment of CLI in diabetic patients.

Circ-ADAM9 targeting PTEN and ATG7 promotes autophagy and apoptosis of diabetic endothelial progenitor cells by sponging mir-20a-5p

Dysfunction of endothelial progenitor cells (EPCs) is a key factor in vascular complications of diabetes mellitus. Although the roles of microRNAs and circular RNAs in regulating cell functions have been thoroughly studied, their role in regulating autophagy and apoptosis of EPCs remains to be elucidated. This study investigated the roles of mir-20a-5p and its predicted target circ-ADAM9 in EPCs treated with high glucose (30 mM) and in a diabetic mouse hind limb ischemia model. It is found that Mir-20a-5p inhibited autophagy and apoptosis of EPCs induced by high-concentration glucose. Further, mir-20a-5p could inhibit the expression of PTEN and ATG7 in EPCs, and promote the phosphorylation of AKT and mTOR proteins under high-glucose condition. Investigation of the underlying mechanism revealed that circ-ADAM9, as a miRNA sponges of mir-20a-5p, promoted autophagy and apoptosis of EPCs induced by high-concentration glucose. Circ-ADAM9 upregulated PTEN and ATG7 in interaction with mir-20a-5p, and inhibited the phosphorylation of AKT and mTOR to aggravate autophagy and apoptosis of EPCs under high glucose. In addition, silencing of circ-ADAM9 increased microvessel formation in the hind limbs of diabetic mice. Our findings disclose a novel autophagy/apoptosis-regulatory pathway that is composed of mir-20a-5p, circ-ADAM9, PTEN, and ATG7. Circ-ADAM9 is a potential novel target for regulating the function of diabetic EPCs and angiogenesis.

Hypoxia promotes differentiation of adipose-derived stem cells into endothelial cells through demethylation of ephrinB2

BackgroundDelivery of endothelial cells into the ischemic tissue is emerging as an alternative approach in revascularization of injured tissues by means of angiogenesis to restore organ function. Adipose-derived stem cells (ASCs) are a readily accessible source of the mesenchymal stem cell with rapid expansion and multidifferentiation potential. The view has emerged that endothelial cells (ECs) differentiated from ASCs is a step forward for adult vascular repair in regenerative medicine and construction of the blood vessel by tissue engineering approach.MethodsIn this study, differentiation of human ASCs (hASCs) into vascular EC lineage was induced by combined treatment of vascular endothelial growth factor (VEGF) and bone morphogenetic protein-4 (BMP4) under hypoxia condition. The expression of CD31, VEGF-R2, and VE-cadherin was determined by immunofluorescent staining, real-time PCR, and western blot analysis. These differentiated cells acquired functional characteristics of mature ECs as determined by their tube formation ability, DiI-ac-LDL uptake, and nitric oxide secretion in vitro. The methylation status in the proximal promoter CpGs was determined by bisulfite sequencing.ResultshASCs expressed endothelial cell markers including CD31, VEGF-R2, and VE-cadherin by combined treatment of VEGF and BMP4 under hypoxia condition. These differentiated cells exhibited the angiogenesis potential in vitro, and injection of these differentiated cells enhanced angiogenesis in the ischemic hindlimb of diabetic mice. Furthermore, it was found that hypoxia increased significantly EphrinB2 expression EC differentiation, which is greatly downregulated with EphrinB2 blockage. The methylation status in the proximal promoter CpG results showed that methylation of EphrinB2 promoter decreased in hASCs with exposure to hypoxia.ConclusionOur data demonstrate that hASCs can be efficiently induced to differentiate into vascular EC lineages which are mediated by demethylation of ephrinB2 under hypoxia condition.

Curcumin induces therapeutic angiogenesis in a diabetic mouse hindlimb ischemia model via modulating the function of endothelial progenitor cells

BackgroundNeovascularization is impaired in diabetes mellitus, which leads to the development of peripheral arterial disease and is mainly attributed to the dysfunction of endothelial progenitor cells (EPCs). Previous studies proved the promotional effect of curcumin on neovascularization in wound healing of diabetes. Thus, we hypothesize that curcumin could promote neovascularization at sites of hindlimb ischemia in diabetes and might take effect via modulating the function of EPCs.MethodsStreptozotocin-induced type 1 diabetic mice and nondiabetic mice both received unilateral hindlimb ischemic surgery. Curcumin was then administrated to the mice by lavage for 14 days consecutively. Laser Doppler perfusion imaging was conducted to demonstrate the blood flow reperfusion. Capillary density was measured in the ischemic gastrocnemius muscle. In addition, angiogenesis, migration, proliferation abilities, and senescence were determined in EPCs isolated from diabetic and nondiabetic mice. Quantitative PCR was then used to determine the mRNA expression of vascular endothelial growth factor (VEGF) and angiopoetin-1 (Ang-1) in EPCs.ResultsCurcumin application to type 1 diabetic mice significantly improved blood reperfusion and increased the capillary density in ischemic hindlimbs. The in-vitro study also revealed that the angiogenesis, migration, and proliferation abilities of EPCs and the number of senescent EPCs were reversed by curcumin application. Quantitative PCR confirmed the overexpression of VEGF-A and Ang-1 in EPCs after curcumin treatment.ConclusionCurcumin could enhance neovascularization via promoting the function of EPCs in a diabetic mouse hindlimb ischemia model.

Restoration of Hydrogen Sulfide Production in Diabetic Mice Improves Reparative Function of Bone Marrow Cells.

Bone marrow cell (BMC)-based treatment for critical limb ischemia in diabetic patients yielded a modest therapeutic effect resulting from cell dysfunction. Therefore, approaches that improve diabetic stem/progenitor cell functions may provide therapeutic benefits. Here, we tested the hypothesis that restoration of hydrogen sulfide (H2S) production in diabetic BMCs improves their reparative capacities. Mouse BMCs were isolated by density-gradient centrifugation. Unilateral hind limb ischemia was conducted in 12- to 14-week-old db/+ and db/db mice by ligation of the left femoral artery. The H2S level was measured by either gas chromatography or staining with florescent dye sulfidefluor 7 AM. Both H2S production and cystathionine γ-lyase (CSE), an H2S enzyme, levels were significantly decreased in BMCs from diabetic db/db mice. Administration of H2S donor diallyl trisulfide (DATS) or overexpression of CSE restored H2S production and enhanced cell survival and migratory capacity in high glucose (HG)-treated BMCs. Immediately after hind limb ischemia surgery, the db/+ and db/db mice were administered DATS orally and/or given a local intramuscular injection of green fluorescent protein-labeled BMCs or red fluorescent protein-CSE-overexpressing BMCs (CSE-BMCs). Mice with hind limb ischemia were divided into 6 groups: db/+, db/db, db/db+BMCs, db/db+DATS, db/db+DATS+BMCs, and db/db+CSE-BMCs. DATS and CSE overexpression greatly enhanced diabetic BMC retention in ischemic hind limbs followed by improved blood perfusion, capillary/arteriole density, skeletal muscle architecture, and cell survival and decreased perivascular CD68+ cell infiltration in the ischemic hind limbs of diabetic mice. It is interesting to note that DATS or CSE overexpression rescued high glucose-impaired migration, tube formation, and survival of BMCs or mature human cardiac microvascular endothelial cells. Moreover, DATS restored nitric oxide production and decreased endothelial nitric oxide synthase phosphorylation at threonine 495 levels in human cardiac microvascular endothelial cells and improved BMC angiogenic activity under high glucose condition. Last, silencing CSE by siRNA significantly increased endothelial nitric oxide synthase phosphorylation at threonine 495 levels in human cardiac microvascular endothelial cells. Decreased CSE-mediated H2S bioavailability is an underlying source of BMC dysfunction in diabetes mellitus. Our data indicate that H2S and overexpression of CSE in diabetic BMCs may rescue their dysfunction and open novel avenues for cell-based therapeutics of critical limb ischemia in diabetic patients.

Anti-vascular endothelial growth factor treatment induces blood flow recovery through vascular remodeling in high-fat diet induced diabetic mice

Diabetes mellitus (DM) leads to the development of microvascular diseases and is associated with impaired angiogenesis. The presence of vascular endothelial growth factor (VEGF) can block PDGF-BB dependent regulation of neovascularization and vessel normalization. We tested the hypothesis that the inhibition of VEGF improves blood flow in a mouse hindlimb ischemia model produced by femoral artery ligation. In this study, we examined the effect of bevacizumab, a humanized monoclonal antibody against VEGF-A, on blood perfusion and angiogenesis after hindlimb ischemia. We showed that bevacizumab induces functional blood flow in high fat chow (HFC)-fed diabetic mice. Treatment with bevacizumab increased the expression of platelet derived growth factor-BB (PDGF-BB) in ischemic muscle, and led to vascular normalization. It also blocked vascular leakage by improving the recruitment of pericytes associated with nascent blood vessels, but it did not affect capillary formation. Furthermore, treatment with an anti-PDGF drug significantly inhibited blood flow perfusion in diabetic mice treated with bevacizumab. These results indicate that bevacizumab improves blood flow recovery through the induction of PDGF-BB in a diabetic mouse hindlimb ischemia model, and that vessel normalization may represent a useful strategy for the prevention and treatment of diabetic peripheral arterial disease.

Sonic hedgehog improves ischemia-induced neovascularization by enhancing endothelial progenitor cell function in type 1 diabetes

The Sonic hedgehog (Shh) pathway is downregulated in type 1 diabetes, and it has been reported that augmentation of this pathway may alleviate diabetic complications. However, the cellular mechanisms underlying these protective effects are poorly understood. Recent studies indicate that impaired function of endothelial progenitor cells (EPCs) may contribute to cardiovascular problems in diabetes. We hypothesized that impaired Shh signaling contribute to endothelial progenitor cell dysfunction and that activating the Shh signaling pathway may rescue EPC function and promote diabetic neovascularization. Adult male C57/B6 mice and streptozotocin (STZ)-induced type 1 diabetic mice were used. Gli1 and Ptc1 protein levels were reduced in EPCs from diabetic mice, indicating inhibition of the Shh signaling pathway. EPC migration, tube formation ability, and mobilization were impaired in diabetic mice compared with non-diabetic controls (p < 0.05 vs control), and all were improved by in vivo administration of the Shh pathway receptor agonist SAG (p < 0.05 vs diabetes). SAG significantly increased capillary density and blood perfusion in the ischemic hindlimbs of diabetic mice (p < 0.05 vs diabetes). The AKT activity was lower in EPCs from diabetic mice than those from non-diabetic controls (p < 0.05 vs control). This decreased AKT activity led to an increased GSK-3β activity and degradation of the Shh pathway transcription factor Gli1/Gli2. SAG significantly increased the activity of AKT in EPCs. Our data clearly demonstrate that an impaired Shh pathway mediated by the AKT/GSK-3β pathway can contribute to EPC dysfunction in diabetes and thus activating the Shh signaling pathway can restore both the number and function of EPCs and increase neovascularization in type 1 diabetic mice.

Tumor necrosis factor inhibition increases the revascularization of ischemic hind-limbs in diabetic mice.

Tumor necrosis factor (TNF) is first identified as a mediator of lethal endotoxin poisoning. The anti-TNF therapy in the treatment of rheumatoid arthritis is based on the recognition of the role of TNF as the master regulator. Type II diabetes is characterized with altered stem cells and reduced vasculogenesis. Therefore, we aimed to determine if TNF inhibitor would improve vasculogenesis in ischemic hind-limbs of diabetic mice. Fifty male type 2 diabetic and their control (8-10weeks old mice) were used, and ischemia was induced in the hind-limbs of all mice for 28days. Vessel density was assessed by high-definition microangiography at the end of the treatment period. After 4weeks, vessel density displayed no difference between the ischemic and the non-ischemic legs in control mice. However, in diabetic mice, the ischemic hind-limb vessel density was significantly decreased. Interestingly, diabetic mice displayed a significant improved vasculogenesis when treated with TNF inhibitor. Moreover, this data was confirmed by capillary density determined by immunostaining. TNF inhibitors are able to improve the formation of microvessels in response to ischemia in type 2 diabetes.

Myoblast-conditioned media improve regeneration and revascularization of ischemic muscles in diabetic mice.

IntroductionDiabetes is associated with reduced expression of heme oxygenase-1 (HO-1), a heme-degrading enzyme with cytoprotective and proangiogenic properties. In myoblasts and muscle satellite cells HO-1 improves survival, proliferation and production of proangiogenic growth factors. Induction of HO-1 in injured tissues facilitates neovascularization, the process impaired in diabetes. We aimed to examine whether conditioned media from the HO-1 overexpressing myoblast cell line can improve a blood-flow recovery in ischemic muscles of diabetic mice.MethodsAnalysis of myogenic markers was performed at the mRNA level in primary muscle satellite cells, isolated by a pre-plate technique from diabetic db/db and normoglycemic wild-type mice, and then cultured under growth or differentiation conditions. Hind limb ischemia was performed by femoral artery ligation in db/db mice and blood recovery was monitored by laser Doppler measurements. Mice were treated with a single intramuscular injection of conditioned media harvested from wild-type C2C12 myoblast cell line, C2C12 cells stably transduced with HO-1 cDNA, or with unconditioned media.ResultsExpression of HO-1 was lower in muscle satellite cells isolated from muscles of diabetic db/db mice when compared to their wild-type counterparts, what was accompanied by increased levels of Myf5 or CXCR4, and decreased Mef2 or Pax7. Such cells also displayed diminished differentiation potential when cultured in vitro, as shown by less effective formation of myotubes and reduced expression of myogenic markers (myogenic differentiation antigen - myoD, myogenin and myosin). Blood flow recovery after induction of severe hind limb ischemia was delayed in db/db mice compared to that in normoglycemic individuals. To improve muscle regeneration after ischemia, conditioned media collected from differentiating C2C12 cells (control and HO-1 overexpressing) were injected into hind limbs of diabetic mice. Analysis of blood flow revealed that media from HO-1 overexpressing cells accelerated blood-flow recovery, while immunohistochemical staining assessment of vessel density in injected muscle confirmed increased angiogenesis. The effect might be mediated by stromal-cell derived factor-1α proangiogenic factor, as its secretion is elevated in HO-1 overexpressing cells.ConclusionsIn conclusion, paracrine stimulation of angiogenesis in ischemic skeletal muscle using conditioned media may be a safe approach exploiting protective and proangiogenic properties of HO-1 in diabetes.

ROS-responsive microspheres for on demand antioxidant therapy in a model of diabetic peripheral arterial disease

A new microparticle-based delivery system was synthesized from reactive oxygen species (ROS)-responsive poly(propylene sulfide) (PPS) and tested for “on demand” antioxidant therapy. PPS is hydrophobic but undergoes a phase change to become hydrophilic upon oxidation and thus provides a useful platform for ROS-demanded drug release. This platform was tested for delivery of the promising anti-inflammatory and antioxidant therapeutic molecule curcumin, which is currently limited in use in its free form due to poor pharmacokinetic properties. PPS microspheres efficiently encapsulated curcumin through oil-in-water emulsion and provided sustained, on demand release that was modulated in vitro by hydrogen peroxide concentration. The cytocompatible, curcumin-loaded microspheres preferentially targeted and scavenged intracellular ROS in activated macrophages, reduced in vitro cell death in the presence of cytotoxic levels of ROS, and decreased tissue-level ROS in vivo in the diabetic mouse hind limb ischemia model of peripheral arterial disease. Interestingly, due to the ROS scavenging behavior of PPS, the blank microparticles also showed inherent therapeutic properties that were synergistic with the effects of curcumin in these assays. Functionally, local delivery of curcumin-PPS microspheres accelerated recovery from hind limb ischemia in diabetic mice, as demonstrated using non-invasive imaging techniques. This work demonstrates the potential for PPS microspheres as a generalizable vehicle for ROS-demanded drug release and establishes the utility of this platform for improving local curcumin bioavailability for treatment of chronic inflammatory diseases.

Suppression of Receptor for Advanced Glycation End Products Improves Angiogenic Responses to Ischemia in Diabetic Mouse Hindlimb Ischemia Model

Background. The role of the receptor for advanced glycation end products (RAGE) for the impaired angiogenic response in diabetic patients is not well known. We investigated the impact of RAGE suppression by soluble RAGE (sRAGE) on the angiogenic response in a diabetic hindlimb ischemia mouse model. Materials and Methods. Hindlimb ischemia model was prepared by ligation of femoral artery in diabetic and nondiabetic mice. Ischemia-induced angiogenic response was evaluated by laser-Doppler perfusion imaging, muscle capillary density, and protein expression of vascular endothelial growth factor (VEGF) and high-mobility group box (HMGB)-1. Results. Diabetic mice showed attenuated recovery of ischemic limb perfusion on laser-Doppler perfusion imaging compared with nondiabetic mice. The treatment with sRAGE significantly improved blood flow in the ischemic limbs of diabetic mice. The expression levels of VEGF and HMGB-1 in the limb muscle tissues of diabetic mice were lower than in those of nondiabetic mice. The treatment with sRAGE significantly increased the VEGF and HMGB-1 protein expression in the ischemic limb muscle tissues in the diabetic mice. Conclusion. The suppression of RAGE by sRAGE administration improved angiogenic response to ischemia in diabetic mice and was associated with increased HMGB-1 and VEGF levels in muscle tissues.

Endothelial Progenitor Cells Derived from Wharton's Jelly of the Umbilical Cord Reduces Ischemia-Induced Hind Limb Injury in Diabetic Mice by Inducing HIF-1α/IL-8 Expression

Peripheral arterial diseases, the major complication of diabetes, can result in lower limb amputation. Since endothelial progenitor cells (EPCs) are involved in neovascularization, the aim of this study was to examine whether EPCs isolated from Wharton's jelly (WJ-EPCs) of the umbilical cord, a rich source of mesenchymal stem cells, could reduce ischemia-induced hind limb injury in diabetic mice. We evaluated the effects of WJ-EPC transplantation on hind limb injury caused by femoral artery ligation in mice with streptozotocin (STZ)-induced diabetes. We found that the ischemic hind limb in mice with STZ-induced diabetes showed decreased blood flow and capillary density and increased cell apoptosis and that these effects were significantly inhibited by an injection of WJ-EPCs. In addition, hypoxia-inducible factor-1α (HIF-1α) and interleukin-8 (IL-8) were highly expressed in transplanted WJ-EPCs in the ischemic skeletal tissues and were present at high levels in hypoxia-treated cultured WJ-EPCs. Moreover, incubation of the NOR skeletal muscle cell line under hypoxic conditions in conditioned medium from EPCs cultured for 16 h under hypoxic conditions resulted in decreased expression of pro-apoptotic proteins and increased expression of anti-apoptotic proteins. The inhibition of HIF-1α or IL-8 expression by EPCs using HIF-1α siRNA or IL-8 siRNA, respectively, prevented this change in expression of apoptotic-related proteins. Wharton's jelly in the umbilical cord is a valuable source of EPCs, and transplantation of these EPCs represents an innovative therapeutic strategy for treating diabetic ischemic tissues. The HIF-1α/IL-8 signaling pathway plays a critical role in the protective effects of EPCs in the ischemic hind limb of diabetic mice.

Beneficial effects of ginsenoside-Rg1 on ischemia-induced angiogenesis in diabetic mice

Neovascularization and the formation of collateral vessels are often impaired in diabetes mellitus (DM) population compared with non-diabetics. Alterations in vascular endothelial growth factor (VEGF) signaling and endothelial nitric oxide synthase (eNOS) dysfunction have been confirmed to play a crucial role in impaired neovascularization in diabetic mice. Accumulating data have suggested that Rg1, a main component of Panax ginseng, has the ability to promote tubulogenesis of human umbilical vein endothelial cells (HUVECs) in vitro, and that the mechanism involves increased expression level of VEGF as well as increased eNOS activation. Thus, we speculated that Rg1 might also have therapeutic effects on the impairment of neovascularization in diabetic individuals. The aim of the present study was to investigate whether Rg1 could improve angiogenesis in ischemic hindlimb of diabetic mice in vivo. Our data demonstrated that Rg1 treatment resulted in improved angiogenesis in the diabetic ischemic hindlimb, and the potential mechanism might involve increased eNOS activation, upregulated VEGF expression, and inhibited apoptosis. Our results suggest that Rg1 may be used as a novel and useful adjunctive drug for the therapy of peripheral arterial disease in DM.

Therapeutic Potential of High Mobility Group Box-1 in Ischemic Injury and Tissue Regeneration

High-mobility group box-1 (HMGB1) is a nuclear protein that acts as a cytokine when released into the extracellular milieu by necrotic and inflammatory cells, and is involved in inflammatory responses and tissue repair. This protein is released passively during cellular necrosis by almost all cells that have a nucleus, but is also actively secreted by immune cells such as macrophages and monocytes. This cytokine plays a key role in mediating the local and systemic responses to several stimuli and might have therapeutic relevance. Indeed, vessel-associated stem cells, injected into the general circulation of dystrophic mice, migrate to sites of tissue damage in response to the HMGB1 signal, by a nuclear factor-κB dependent mechanism. Moreover, endogenous HMGB1 enhances angiogenesis and restores cardiac function in a murine model of myocardial infarction, and the exogenous administration of HMGB1 after myocardial infarction leads to the recovery of left ventricular function through the regeneration of cardiomyocytes. Finally, recent findings show that endogenous HMGB1 is crucial for ischemia-induced angiogenesis in diabetic mice and that HMGB1 protein administration enhances collateral blood flow in the ischemic hind limbs of diabetic mice through a VEGF-dependent manner. The mechanisms of action of this protein are complex and are not well known or defined. The objective of this review is to evaluate the data regarding the tissue regeneration effects of HMGB1, with the aim of providing practical considerations about this topic for the management of subjects affected by ischemic and degenerative diseases.

Label-free 3D optical microangiography imaging of functional vasa nervorum and peripheral microvascular tree in the hind limb of diabetic mice.

Diabetic neuropathy (DN) is, at least in part, associated with the functional attenuation of vasa nervorum, the microvascular structure of peripheral nerves. Microvascular imaging options for vasa nervorum still remain limited. In this work, Optical micro-angiography (OMAG), a volumetric, label-free imaging technique is utilized for characterizing, with high resolution, blood perfusion of peripheral nerve in diabetic mice. We demonstrate that OMAG is able to visualize the structure of microvasculature and to quantify the changes of dynamic blood flow and vessel diameters during administration of vessel stimulator in both diabetic and normal mice. The results indicate the potential of OMAG to assess the blood supply of nerve involved in the pathology and treatment of DN.

Modulating Notch signaling to enhance neovascularization and reperfusion in diabetic mice

Diabetes can diminish the responsiveness to angiogenic factors (e.g., VEGF) important for wound healing and the treatment of ischemic diseases, and this study investigated the hypothesis that this effect can be reversed by altering Notch signaling. Aortic endothelial cells (ECs) isolated from diabetic mice demonstrated reduced sprouting capability in vitro, but adding a Notch inhibitor (DAPT) led to cell-density and VEGF-dose dependent enhancement of proliferation, migration and sprouting, in both 2-D and 3-D cultures, as compared to VEGF alone. The in vivo effects of VEGF and DAPT were tested in the ischemic hind limbs of diabetic mice. Combining VEGF and DAPT delivery resulted in increased blood vessel density (∼150%) and improved tissue perfusion (∼160%), as compared to VEGF alone. To examine if DAPT would interfere with vessel maturation, DAPT was also delivered with a combination of VEGF and platelet derived growth factor (PDGF). DAPT and PDGF did not interfere with the effects of the other, and highly functional and mature networks of vessels could be formed with appropriate delivery. In summary, modulating Notch signaling enhances neovascularization and perfusion recovery in diabetic mice suffering from ischemia, suggesting this approach could have utility for human diabetics.