Endothelial progenitor cells--potential new avenues to improve neoangiogenesis and reendothelialization

Cellular and Noncellular Approaches for Repairing the Damaged Blood-CNS-Barrier in Amyotrophic Lateral Sclerosis

Numerous reports have demonstrated the breakdown of the blood-CNS barrier (B-CNS-B) in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease. Re-establishing barrier integrity in the CNS is critical to prevent further motor neuron degeneration from harmful components in systemic circulation. Potential therapeutic strategies for repairing the B-CNS-B may be achieved by the replacement of damaged endothelial cells (ECs) via stem cell administration or enhancement of endogenous EC survival through the delivery of bioactive particles secreted by stem cells. These cellular and noncellular approaches are thoroughly discussed in the present review. Specific attention is given to certain stem cell types for EC replacement. Also, various nanoparticles secreted by stem cells as well as other biomolecules are elucidated as promising agents for endogenous EC repair. Although the noted in vitro and in vivo studies show the feasibility of the proposed therapeutic approaches to the repair of the B-CNS-B in ALS, further investigation is needed prior to clinical transition.

Upregulation of Anti-Angiogenic miR-106b-3p Correlates Negatively with IGF-1 and Vascular Health Parameters in a Model of Subclinical Cardiovascular Disease: Study with Metformin Therapy

Well-controlled type 1 diabetes mellitus (T1DM) is regarded as a model of subclinical cardiovascular disease (CVD), characterized by inflammation and adverse vascular health. However, the underlying mechanisms are not fully understood. We investigated insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) levels, their correlation to miR-106b-3p expression in a subclinical CVD model, and the cardioprotective effect of metformin. A total of 20 controls and 29 well-controlled T1DM subjects were studied. Plasma IGF-1, IGFBP-3 levels, and miR-106b-3p expression in colony-forming unit-Hills were analyzed and compared with vascular markers. miR-106b-3p was upregulated in T1DM (p < 0.05) and negatively correlated with pro-angiogenic markers CD34+/100-lymphocytes (p < 0.05) and IGF-1 (p < 0.05). IGF-1 was downregulated in T1DM (p < 0.01), which was associated with increased inflammatory markers TNF-α, CRP, and IL-10 and reduced CD34+/100-lymphocytes. IGFBP-3 had no significant results. Metformin had no effect on IGF-1 but significantly reduced miR-106b-3p (p < 0.0001). An Ingenuity Pathway analysis predicted miR-106b-3p to inhibit PDGFA, PIK3CG, GDNF, and ADAMTS13, which activated CVD. Metformin was predicted to be cardioprotective by inhibiting miR-106b-3p. In conclusion: Subclinical CVD is characterized by a cardio-adverse profile of low IGF-1 and upregulated miR-106b-3p. We demonstrated that the cardioprotective effect of metformin may be via downregulation of upregulated miR-106b-3p and its effect on downstream targets.

Elucidation of endothelial progenitor cell dysfunction in diabetes by RNA sequencing and constructing lncRNA-miRNA-mRNA competing endogenous RNA network

With the rapid increase in the incidence of diabetes, non-healing diabetic wounds have posed a huge challenge to public health. Endothelial progenitor cell (EPC) has been widely reported to promote wound repairing, while its number and function were suppressed in diabetes. However, the specific mechanisms and competing endogenous RNA (ceRNA) network of EPCs in diabetes remain largely unknown. Thus, the transcriptome analyses were carried in the present study to clarify the mechanism underlying EPCs dysfunction in diabetes. EPCs were successfully isolated from rats. Compared to the control, diabetic rat-derived EPCs displayed impaired proliferation, migration, and tube formation ability. The differentially expressed (DE) RNAs were successfully identified by RNA sequencing in the control and diabetic groups. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that DE mRNAs were significantly enriched in terms and pathways involved in the functions of EPCs and wound healing. Protein-protein interaction networks revealed critical DE mRNAs in the above groups. Moreover, the whole lncRNA-miRNA-mRNA ceRNA network was constructed, in which 9 lncRNAs, 9 mRNAs, and 5 miRNAs were further validated by quantitative real-time polymerase chain reaction. Rno-miR-10b-5p and Tgfb2 were identified as key regulators of EPCs dysfunction in diabetes. The present research provided novel insight into the underlying mechanism of EPCs dysfunction in diabetes and prompted potential targets to restore the impaired functions, thus accelerating diabetic wound healing. KEY MESSAGES: • Compared to the control, diabetic rat-derived EPCs displayed impaired proliferation, migration, and tube formation ability. • The DE RNAs were successfully identified by RNA sequencing in the control and diabetic groups and analyzed by DE, GO, and KEGG analysis. • PPI and lncRNA-miRNA-mRNA ceRNA networks were constructed. • 9 lncRNAs, 9 mRNAs, and 5 miRNAs were further validated by qRT-PCR. • Rno-miR-10b-5p and Tgfb2 were identified as key regulators of EPCs dysfunction in diabetes.

Regulation of endothelial progenitor cell functions during hyperglycemia: new therapeutic targets in diabetic wound healing

Diabetes is primarily characterized by hyperglycemia, and its high incidence is often very costly to patients, their families, and national economies. Unsurprisingly, the number and function of endothelial progenitor cells (EPCs) decrease in patients resulting in diabetic wound non-healing. As precursors of endothelial cells (ECs), these cells were discovered in 1997 and found to play an essential role in wound healing. Their function, number, and role in wound healing has been widely investigated. Hitherto, a lot of complex molecular mechanisms have been discovered. In this review, we summarize the mechanisms of how hyperglycemia affects the function and number of EPCs and how the affected cells impact wound healing. We aim to provide a complete summary of the relationship between diabetic hyperglycosemia, EPCs, and wound healing, as well as a better comprehensive platform for subsequent related research.

Upregulating CXCR7 accelerates endothelial progenitor cell-mediated endothelial repair by activating Akt/Keap-1/Nrf2 signaling in diabetes mellitus

Background

Endothelial progenitor cell (EPC) dysfunction contributes to vascular disease in diabetes mellitus. However, the molecular mechanism underlying EPC dysfunction and its contribution to delayed reendothelialization in diabetes mellitus remain unclear. Our study aimed to illustrate the potential molecular mechanism underlying diabetic EPC dysfunction in vivo and in vitro. Furthermore, we assessed the effect of EPC transplantation on endothelial regeneration in diabetic rats.

Methods

Late outgrowth EPCs were isolated from the bone marrow of rats for in vivo and in vitro studies. In vitro functional assays and Western blotting were conducted to reveal the association between C-X-C chemokine receptor type 7 (CXCR7) expression and diabetic EPC dysfunction. To confirm the association between cellular CXCR7 levels and EPC function, CXCR7 expression in EPCs was upregulated and downregulated via lentiviral transduction and RNA interference, respectively. Western blotting was used to reveal the potential molecular mechanism by which the Stromal-Derived Factor-1 (SDF-1)/CXCR7 axis regulates EPC function. To elucidate the role of the SDF-1/CXCR7 axis in EPC-mediated endothelial regeneration, a carotid artery injury model was established in diabetic rats. After the model was established, saline-treated, diabetic, normal, or CXCR7-primed EPCs were injected via the tail vein.

Results

Diabetic EPC dysfunction was associated with decreased CXCR7 expression. Furthermore, EPC dysfunction was mimicked by knockdown of CXCR7 in normal EPCs. However, upregulating CXCR7 expression reversed the dysfunction of diabetic EPCs. The SDF-1/CXCR7 axis positively regulated EPC function by activating the AKT-associated Kelch-like ECH-associated protein 1 (keap-1)/nuclear factor erythroid 2-related factor 2 (Nrf2) axis, which was reversed by blockade of AKT and Nrf2. Transplantation of CXCR7-EPCs accelerated endothelial repair and attenuated neointimal hyperplasia in diabetes mellitus more significantly than transplantation of diabetic or normal EPCs. However, the therapeutic effect of CXCR7-EPC transplantation on endothelial regeneration was reversed by knockdown of Nrf2 expression.

Conclusions

Dysfunction of diabetic EPCs is associated with decreased CXCR7 expression. Furthermore, the SDF-1/CXCR7 axis positively regulates EPC function by activating the AKT/keap-1/Nrf2 axis. CXCR7-primed EPCs might be useful for endothelial regeneration in diabetes-associated vascular disease.

Calcitonin Gene-Related Peptide Enhances Distraction Osteogenesis by Increasing Angiogenesis

Distraction osteogenesis (DO) is a well-established surgical technique for treating bone defect and limb lengthening. The major drawback of DO is the long treatment period as the external fixator has to be kept in place until consolidation is completed. Calcitonin gene-related peptide (CGRP) has been reported to promote angiogenesis by affecting endothelial progenitor cells (EPCs) in limb ischemia and wound healing. Thus, the goal of this study was to evaluate the angiogenic effect of exogenous CGRP on bone regeneration in a rat DO model. Exogenous CGRP was directly injected into the bone defect after each cycle of distraction in vivo. Microcomputed tomography, biomechanical test, and histological analysis were performed to assess the new bone formation. Angiography and immunofluorescence were performed to assess the formation of blood vessels. CD31⁺CD144⁺ EPCs in the bone defect were quantified with flow cytometry. In in vitro study, bone marrow stem cells (BMSCs) were used to investigate the effect of CGRP on EPCs production during endothelial differentiation. Our results showed that CGRP significantly promoted bone regeneration and vessel formation after consolidation. CGRP significantly increased the fraction of CD31⁺CD144⁺EPCs and the capillary density in the bone defect at the end of distraction phase. CGRP increased EPC population in the endothelial differentiation of BMSCs in vitro by activating PI3K/AKT signaling pathway. Furthermore, differentiated EPCs rapidly assembled into tube-like structures and promoted osteogenic differentiation of BMSCs. In conclusion, CGRP increased EPC population and promoted blood vessel formation and bone regeneration at the defect region in a DO model. Impact statement Distraction osteogenesis (DO) is a well-established surgical technique for limb lengthening and bone defect. The disadvantage of this technique is that external fixator is needed to be kept in place for about 12 months. This may result in increased risk of infection, financial burden, and negative psychological impacts. In this study, we have injected calcitonin gene-related peptide (CGRP) into the defect region after distraction and found that CGRP enhanced vessel formation and bone regeneration in a rat DO model. This suggests that a controlled delivery system for CGRP could be developed and applied clinically for accelerating bone regeneration in patients with DO.

MicroRNA-126 protects against vascular injury by promoting homing and maintaining stemness of late outgrowth endothelial progenitor cells

BACKGROUND

Endothelial progenitor cells (EPCs) contribute to reendothelialization and neovascularization and protect against vascular injury and ischemia of various organs. We have previously shown downregulation of microRNA (miR)-126 in EPCs from diabetic patients, which contributes to dysfunction of EPCs including impaired migratory ability. The aims of the present study were to examine (1) in vitro the effects of miR-126 on the homing and stemness of late outgrowth EPCs (LOCs), along with relevant signaling pathways, and (2) in vivo the effects of modulating LOCs by manipulating miR-126 expression on LOC homing and reendothelialization of injured arteries in GK rats (a non-obese diabetes model).

METHODS

Rat bone marrow-derived LOCs were transfected with miR-126 inhibitor or lentiviral vectors expressing miR-126. LOC migration was determined by transwell migration assay. CXCR4 expression was measured by real-time PCR, Western blotting, and confocal microscopy while related signaling pathway proteins were measured by Western Blotting. Stemness gene expression, and gene and protein expression and promoter activity of KLF-8 were also measured. LOCs transfected with lenti-miR-126 or miR-126 inhibitor were injected into GK rats with carotid artery injury, and then vascular reendothelialization and the extent of intimal hyperplasia were examined.

RESULTS

Lenti-miR-126 increased while miR-126 inhibitor decreased LOC migration and CXCR4 expression on LOCs. miR-126 positively regulated p-ERK, VEGF, p-Akt, and eNOS protein expression, and inhibitors of these proteins blocked miR-126-induced CXCR4 expression and also reduced LOC migration. Overexpression of miR-126 promoted while inhibition of miR-126 suppressed stemness gene expression in LOCs. miR-126 also inhibited gene and protein expression and promoter activity of KLF-8 while shRNA-mediated knockdown of KLF-8 increased stemness gene expression. Upregulation of stemness gene expression by miR-126 overexpression was completely abrogated by co-transfection of lenti-KLF-8 and lenti-miR-126 into LOCs. In GK rats, transplantation of LOCs overexpressing miR-126 enhanced LOC homing and reendothelialization and decreased intimal hyperplasia of injured arteries.

CONCLUSION

Our results indicate that miR-126 protects against vascular injury by promoting CXCR4 expression and LOC homing via ERK/VEGF and Akt/eNOS signaling pathways and maintaining stemness via targeting KLF-8.

Effect of negative-pressure wound therapy on the circulating number of peripheral endothelial progenitor cells in diabetic patients with mild to moderate degrees of ischaemic foot ulcer

Objective

To investigate the effect of negative-pressure wound therapy (NPWT) on the circulating number of endothelial progenitor cells (EPCs) in diabetic patients with mild to moderate degrees of ischemic foot ulcer.

Methods

We selected 84 diabetic patients who had a foot ulcer with a duration of at least four weeks and who had an ankle-brachial index of 0.5–0.9. Patients were assigned to one two groups according to 2:1 randomization: NPWT group ( n = 56) and non-NPWT (patients who did not receive NPWT) group ( n = 28). The control group (NC group) was composed of 18 patients who had normal glucose tolerance and lower extremity ulcer without arteriovenous disease. NPWT was performed on the ulcer after debridement for one week for patients in both the NPWT group and the NC group, and the patients in the non-NPWT group received conventional treatment process. The circulating number of EPCs was measured before and after various treatments, and the factors influencing their changes were analysed.

Results

After NPWT, the circulating number of EPCs significantly increased in both the NPWT group and the NC group ((85.3 ± 18.1) vs. (34.1 ± 12.5)/106 cells; (119.9 ± 14.4) vs. (66.1 ± 10.6)/106 cells, both P < 0.05). In contrast, the circulating number of EPCs had no significant change in the non-NPWT group ((45.2 ± 19.4) vs. (34.7 ± 16.8)/106 cells, P > 0.05). In addition, the circulating levels of vascular endothelial growth factor (VEGF) and the protein expressions of VEGF and stromal cell-derived factor-1α (SDF-1α) in the granulation tissue significantly increased after NPWT in both the NPWT and the NC group, but there was no significant change in the non-NPWT group. Compared with the non-NPWT group, the changes in VEGF and SDF-1α levels in the sera and granulation tissue were all significantly higher in both the NPWT and NC groups ( P < 0.05, P < 0.01, respectively). There was no significant difference in changes in the circulating number of EPCs in the peripheral blood and levels of VEGF and SDF-1α in the sera and granulation tissue between the NPWT and NC groups. Correlation analysis showed that the change in the circulating number of EPCs was correlated with the changes of VEGF and SDF-1α levels in the sera and granulation of the NPWT and NC groups ( P < 0.05).

Conclusion

NPWT may increase the circulating number of EPCs in diabetic patients with mild to moderate ischaemic foot ulcer as in non-diabetic controls, which may be attributed to the upregulation of systemic and local VEGF and SDF-1α levels.

Construction of a small-caliber tissue-engineered blood vessel using icariin-loaded β-cyclodextrin sulfate for in situ anticoagulation and endothelialization

The rapid endothelialization of tissue-engineered blood vessels (TEBVs) can effectively prevent thrombosis and inhibit intimal hyperplasia. The traditional Chinese medicine ingredient icariin is highly promising for the treatment of cardiovascular diseases. β-cyclodextrin sulfate is a type of hollow molecule that has good biocompatibility and anticoagulation properties and exhibits a sustained release of icariin. We studied whether icariin-loaded β-cyclodextrin sulfate can promote the endothelialization of TEBVs. The experimental results showed that icariin could significantly promote the proliferation and migration of endothelial progenitor cells; at the same time, icariin could promote the migration of rat vascular endothelial cells (RAVECs). Subsequently, we used an electrostatic force to modify the surface of the TEBVs with icariin-loaded β-cyclodextrin sulfate, and these vessels were implanted into the rat common carotid artery. After 3 months, micro-CT results showed that the TEBVs modified using icariin-loaded β-cyclodextrin sulfate had a greater patency rate. Scanning electron microscopy (SEM) and CD31 immunofluorescence results showed a better degree of endothelialization. Taken together, icariin-loaded β-cyclodextrin sulfate can achieve anticoagulation and rapid endothelialization of TEBVs to ensure their long-term patency.

Endothelial and Astrocytic Support by Human Bone Marrow Stem Cell Grafts into Symptomatic ALS Mice towards Blood-Spinal Cord Barrier Repair

Vascular pathology, including blood-CNS barrier (B-CNS-B) damage via endothelial cell (EC) degeneration, is a recently recognized hallmark of Amyotrophic Lateral Sclerosis (ALS) pathogenesis. B-CNS-B repair may be a new therapeutic approach for ALS. This study aimed to determine effects of transplanted unmodified human bone marrow CD34+ (hBM34+) cells into symptomatic G93A mice towards blood-spinal cord barrier (BSCB) repair. Thirteen weeks old G93A mice intravenously received one of three different doses of hBM34+ cells. Cell-treated, media-treated, and control mice were euthanized at 17 weeks of age. Immunohistochemical (anti-human vWF, CD45, GFAP, and Iba-1) and motor neuron histological analyses were performed in cervical and lumbar spinal cords. EB levels in spinal cord parenchyma determined capillary permeability. Transplanted hBM34+ cells improved behavioral disease outcomes and enhanced motor neuron survival, mainly in high-cell-dose mice. Transplanted cells differentiated into ECs and engrafted within numerous capillaries. Reduced astrogliosis, microgliosis, and enhanced perivascular end-feet astrocytes were also determined in spinal cords, mostly in high-cell-dose mice. These mice also showed significantly decreased parenchymal EB levels. EC differentiation, capillary engraftment, reduced capillary permeability, and re-established perivascular end-feet astrocytes in symptomatic ALS mice may represent BSCB repair processes, supporting hBM34+ cell transplantation as a future therapeutic strategy for ALS patients.

Transplantation of EPCs overexpressing PDGFR-β promotes vascular repair in the early phase after vascular injury

BACKGROUND

Endothelial progenitor cells (EPCs) play important roles in the regeneration of the vascular endothelial cells (ECs). Platelet-derived growth factor receptor (PDGFR)-β is known to contribute to proliferation, migration, and angiogenesis of EPCs, this study aims to investigate effects of transplantation of EPCs overexpressing PDGFR-β on vascular regeneration.

METHODS

We transplanted genetically modified EPCs overexpressing PDGFR-β into a mouse model with carotid artery injury. After 3 days of EPCs transplantation, the enhanced green fluorescent protein (EGFP)-expressing cells were found at the injury site and the lining of the lumen by laser scanning confocal microscope (LSCM). At 4, 7, and 14 days of the carotid artery injury, reendothelialization was evaluated by Evans Blue staining. Neointima formation was evaluated at day 14 with hematoxylin and eosin (HE) staining by calculating the neointimal area, medial area, and neointimal/media (NI/M) ratio. Intimal cell apoptosis was evaluated using TUNEL assay. Then we tested whether PDGF-BB-induced VSMC migration and PDGF-BB's function in reducing VSMC apoptosis can be attenuated by EPCs overexpressing PDGFR-β in a transwell co-culture system.

RESULTS

Our results showed that EPCs overexpressing PDGFR-β accelerates reendothelialization and mitigates neointimal formation at 14 days after injury. Moreover, we found that there is great possibility that EPCs overexpressing PDGFR-β enhanc VSMC apoptosis and suppress VSMC migration by competitive consumption of PDGF-BB in the early phase after carotid artery injury in mice.

CONCLUSIONS

We report the first in vivo and in vitro evidence that transplantation of genetically modified EPC can have a combined effect of both amplifying the reendothelialization capacity of EPCs and inhibiting neointima formation so as to facilitate better inhibition of adverse remodeling after vascular injury.

Aspirin Inhibits Degenerative Changes of Aneurysmal Wall in a Rat Model

Aneurysmal subarachnoid hemorrhage still has a high mortality and morbidity despite notable advances in surgical approaches to cerebral aneurysm (CA). We examined the role of aspirin in vascular inflammation and degeneration. CA was induced in male Sprague-Dawley rats by ligating left common carotid artery and bilateral posterior renal arteries with or without aspirin treatment. The right anterior cerebral artery/olfactory artery (ACA/OA) bifurcations were stripped and assessed morphologically after Verhoeff's Van Gieson staining. Blood sample was obtained to examine circulating CD34(+) CD133(+) endothelial progenitor cells (EPCs), platelet aggregation and platelet counts. Macrophages infiltration in aneurysmal wall was evaluated by immunohistochemistry. Expression of matrix metalloproteinase-2 and 9 (MMP-2 and 9), nuclear factor kappa B (NF-κB), macrophage chemoattractant protein-1 (MCP-1) and vascular cell adhesion molecule-1 (VCAM-1) was examined by RT-PCR. 2 months after CA induction, surgically treated rats manifested aneurysmal degeneration in ACA/OA bifurcations. Aspirin-treated rats exhibited a significant decrease in degradation of internal elastic lamina (IEL), medial layer thinning, CA size and macrophages infiltration with reduced expression of MMP-2 and 9 compared with rats in the CA group. RT-PCR demonstrated that the upregulation of NF-κB, MCP-1 and VCAM-1 after CA induction was reversed by aspirin treatment. Aspirin treatment following CA induction increased circulating EPCs to near control levels and reduced platelet aggregation without changing platelet counts. The evidence suggested that aspirin significantly reduced degeneration of aneurysm walls by inhibiting macrophages-mediated chronic inflammation and mobilizing EPCs.

Intravenous transfusion of endothelial colony-forming cells attenuates vascular degeneration after cerebral aneurysm induction

Cerebral aneurysm (CA) rupture is a major cause of subarachnoid hemorrhage with high morbidity and mortality. Using an animal model, we examined the potential of endothelial colony-forming cells (ECFCs) transfusion on vascular degeneration after CA induction and underlying mechanisms. CA was induced in the right anterior cerebral artery-olfactory artery (ACA/OA) bifurcations in Sprague-Dawley rats with or without ECFCs transfusion. The degeneration of internal elastic lamina (IEL), media thickness and CA size were evaluated. Expression of matrix metalloproteinase-2 and 9 (MMP-2 and 9), tissue inhibitor of metalloproteinase-1 (TIMP-1), macrophage chemoattractant protein-1 (MCP-1), vascular cell adhesion molecule-1 (VCAM-1), nuclear factor κB (NF-κB), endothelial nitric oxide synthase (eNOS), B-cell leukemia/lymphoma-2 (Bcl-2), and inducible nitric oxide synthase (iNOS) were analyzed by quantitative real-time polymerase chain reaction. The macrophages infiltration and apoptosis of smooth muscle cells (SMCs) were examined immunohistologically. Rats in CA+ECFCs transfusion group showed a notable reduction in IEL degeneration, media thinning and CA size compared with those in CA+saline group. ECFCs transfusion inhibited the MMP-driven wall destruction by downregulating MMP-2, MMP-9 expression and upregulating TIMP-1. ECFCs transfusion dramatically decreased VCAM-1 and NF-κB expression, increased eNOS expression and caused no change in MCP-1 expression, which was accompanied by reduced macrophages infiltration. Moreover, ECFCs transfusion reversed downregulation of Bcl-2 expression and upregulation of iNOS expression, and decreased SMCs apoptosis. Collectively, these findings suggest that ECFCs transfusion confers protection against degeneration of aneurysmal wall by inhibiting inflammatory cascades and SMCs apoptosis.