Origins and functional differences of blood endothelial cells

The interests in blood endothelial cells arise from their therapeutic potential in vascular repair and regeneration. Our understanding of blood endothelial cells that exist in the circulation has been evolving significantly from the original concept of endothelial progenitor cells. Many studies have uncovered heterogeneities of blood endothelial subtypes where some cells express both endothelial and hematopoietic antigens, and others possess either mature or immature endothelial markers. Due to the lack of definitive cell marker identities, there have been momentums in the field to adopt a technical-oriented labeling system based on the cells' involvement in postnatal neovascularization and cell culture derivatives. Our review streamlines nomenclatures for blood endothelial subtypes and standardizes understanding of their functional differences. Broadly, we will discuss about myeloid angiogenic cells (MACs), endothelial colony-forming cells (ECFCs), blood outgrowth endothelial cells (BOECs) and circulating endothelial cells (CECs). The strategic location of blood endothelial cells confers them essential roles in supporting physiological processes. MACs exert angiogenic effects through paracrine mechanisms, while ECFCs are recruited to sites of vascular injury to participate directly in new vessel formation. BOECs are an in vitro derivative of ECFCs. CECs are shed into the bloodstream from damaged vessels, hence reflective of endothelial dysfunction. With clarity on the functional attributes of blood endothelial subtypes, we present recent advances in their applications in disease modelling, along with serving as biomarkers of vascular tissue homeostasis.

Endothelial progenitor cells in the host defense response

Extensive injury of endothelial cells in blood vasculature, especially in the microcirculatory system, frequently occurs in hosts suffering from sepsis and the accompanied systemic inflammation. Pathological factors, including toxic components derived from invading microbes, oxidative stress associated with tissue ischemia/reperfusion, and vessel active mediators generated during the inflammatory response, are known to play important roles in mediating endothelial injury. Collapse of microcirculation and tissue edema developed from the failure of endothelial barrier function in vital organ systems, including the lung, brain, and kidney, are detrimental, which often predict fatal outcomes. The host body possesses a substantial capacity for maintaining vascular homeostasis and repairing endothelial damage. Bone marrow and vascular wall niches house endothelial progenitor cells (EPCs). In response to septic challenges, EPCs in their niche environment are rapidly activated for proliferation and angiogenic differentiation. In the meantime, release of EPCs from their niches into the blood stream and homing of these vascular precursors to tissue sites of injury are markedly increased. The recruited EPCs actively participate in host defense against endothelial injury and repair of damage in blood vasculature via direct differentiation into endothelial cells for re-endothelialization as well as production of vessel active mediators to exert paracrine and autocrine effects on angiogenesis/vasculogenesis. In recent years, investigations on significance of EPCs in host defense and molecular signaling mechanisms underlying regulation of the EPC response have achieved substantial progress, which promotes exploration of vascular precursor cell-based approaches for effective prevention and treatment of sepsis-induced vascular injury as well as vital organ system failure.

AGEs/RAGE Promote Osteogenic Differentiation in Rat Bone Marrow-Derived Endothelial Progenitor Cells via MAPK Signaling

Systemic vascular impairment is the most common complication of diabetes. Advanced glycation end products (AGEs) can exacerbate diabetes-related vascular damage by affecting the intima and media through a variety of mechanisms. In the study, we demonstrated that AGEs and their membrane receptor RAGE could induce the differentiation of EPCs into osteoblasts under certain circumstances, thereby promoting accelerated atherosclerosis. Differentiation into osteoblasts was confirmed by positive staining for DiI-acetylated fluorescently labeled low-density lipoprotein and FITC-conjugated Ulex europaeus agglutinin. During differentiation, expression of receptor for AGE (RAGE) was significantly upregulated. This upregulation was attenuated by transfection with RAGE-targeting small interfering (si)RNA. siRNA-mediated knockdown of RAGE expression significantly inhibited the upregulation of AGE-induced calcification-related proteins, such as runt-related transcription factor 2 (RUNX2) and osteoprotegerin (OPG). Additional experiments showed that AGE induction of EPCs significantly induced ERK, p38MAPK, and JNK activation. The AGE-induced upregulation of osteoblast proteins (RUNX2 and OPG) was suppressed by treatment with a p38MAPK inhibitor (SB203580) or JNK inhibitor (SP600125), but not by treatment with an ERK inhibitor (PD98059), which indicated that AGE-induced osteoblast differentiation from EPCs may be mediated by p38MAPK and JNK signaling, but not by ERK signaling. These data suggested that AGEs may bind to RAGE on the EPC membrane to trigger differentiation into osteoblasts. The underlying mechanism appears to involve the p38MAPK and JNK1/2 pathways, but not the ERK1/2 pathway.

Long noncoding RNA p21 enhances autophagy to alleviate endothelial progenitor cells damage and promote endothelial repair in hypertension through SESN2/AMPK/TSC2 pathway

Vascular damage of hypertension has been the focus of hypertension treatment, and endothelial progenitor cells (EPCs) play an important role in the repair of vascular endothelial damage. Functional damage and decreased number of EPCs are observed in the peripheral circulation of hypertensive patients, but its mechanism is not yet elucidated. Here, we show that the number of EPCs in hypertensive patients is significantly lower than that of normal population, and the cell function decreases with a higher proportion of EPCs at later stages. A decrease in autophagy is responsible for the senescence and damage of EPCs induced by AngII. Moreover, lncRNA-p21 plays a critical regulator role in EPCs' senescence and dysfunction. Furthermore, lncRNA-p21 activates SESN2/AMPK/TSC2 pathway by promoting the transcriptional activity of p53 and enhances autophagy to protect against AngII-induced EPC damage. The data provide evidence that a reversal of decreased autophagy serves as the protective mechanism of EPC injury in hypertensive patients, and lncRNA-p21 is a new therapeutic target for vascular endothelial repair in hypertension.

Proteomic Signature of Dysfunctional Circulating Endothelial Colony-Forming Cells of Young Adults

Background A subpopulation of endothelial progenitor cells called endothelial colony-forming cells (ECFCs) may offer a platform for cellular assessment in clinical studies because of their remarkable angiogenic and expansion potentials in vitro. Despite endothelial cell function being influenced by cardiovascular risk factors, no studies have yet provided a comprehensive proteomic profile to distinguish functional (ie, more angiogenic and expansive cells) versus dysfunctional circulating ECFCs of young adults. The aim of this study was to provide a detailed proteomic comparison between functional and dysfunctional ECFCs. Methods and Results Peripheral blood ECFCs were isolated from 11 subjects (45% men, aged 27±5 years) using Ficoll density gradient centrifugation. ECFCs expressed endothelial and progenitor surface markers and displayed cobblestone-patterned morphology with clonal and angiogenic capacities in vitro. ECFCs were deemed dysfunctional if <1 closed tube formed during the in vitro tube formation assay and proliferation rate was <20%. Hierarchical functional clustering revealed distinct ECFC proteomic signatures between functional and dysfunctional ECFCs with changes in cellular mechanisms involved in exocytosis, vesicle transport, extracellular matrix organization, cell metabolism, and apoptosis. Targeted antiangiogenic proteins in dysfunctional ECFCs included SPARC (secreted protein acidic and rich in cysteine), CD36 (cluster of differentiation 36), LUM (lumican), and PTX3 (pentraxin-related protein PYX3). Conclusions Circulating ECFCs with impaired angiogenesis and expansion capacities have a distinct proteomic profile and significant phenotype changes compared with highly angiogenic endothelial cells. Impaired angiogenesis in dysfunctional ECFCs may underlie the link between endothelial dysfunction and cardiovascular disease risks in young adults.

Self-assembly of differentiated progenitor cells facilitates spheroid human skin organoid formation and planar skin regeneration

Self-assembly of solid organs from single cells would greatly expand applicability of regenerative medicine. Stem/progenitor cells can self-organize into micro-sized organ units, termed organoids, partially modelling tissue function and regeneration. Here we demonstrated 3D self-assembly of adult and induced pluripotent stem cell (iPSC)-derived fibroblasts, keratinocytes and endothelial progenitors into both, planar human skin in vivo and a novel type of spheroid-shaped skin organoids in vitro, under the aegis of human platelet lysate. Methods: Primary endothelial colony forming cells (ECFCs), skin fibroblasts (FBs) and keratinocytes (KCs) were isolated from human tissues and polyclonally propagated under 2D xeno-free conditions. Human tissue-derived iPSCs were differentiated into endothelial cells (hiPSC-ECs), fibroblasts (hiPSC-FBs) and keratinocytes (hiPSC-KCs) according to efficiency-optimized protocols. Cell identity and purity were confirmed by flow cytometry and clonogenicity indicated their stem/progenitor potential. Triple cell type floating spheroids formation was promoted by human platelet-derived growth factors containing culture conditions, using nanoparticle cell labelling for monitoring the organization process. Planar human skin regeneration was assessed in full-thickness wounds of immune-deficient mice upon transplantation of hiPSC-derived single cell suspensions. Results: Organoids displayed a distinct architecture with surface-anchored keratinocytes surrounding a stromal core, and specific signaling patterns in response to inflammatory stimuli. FGF-7 mRNA transfection was required to accelerate keratinocyte long-term fitness. Stratified human skin also self-assembled within two weeks after either adult- or iPSC-derived skin cell-suspension liquid-transplantation, healing deep wounds of mice. Transplant vascularization significantly accelerated in the presence of co-transplanted endothelial progenitors. Mechanistically, extracellular vesicles mediated the multifactorial platelet-derived trophic effects. No tumorigenesis occurred upon xenografting. Conclusion: This illustrates the superordinate progenitor self-organization principle and permits novel rapid 3D skin-related pharmaceutical high-content testing opportunities with floating spheroid skin organoids. Multi-cell transplant self-organization facilitates development of iPSC-based organ regeneration strategies using cell suspension transplantation supported by human platelet factors.

Endothelial progenitor/stem cells in engineered vessels for vascular transplantation

BACKGROUND

Dysfunction of blood vessel leads to aneurysms, myocardial infarction and other thrombosis conditions. Current treatment strategies are transplantation of blood vessels from one part of the body to other dysfunction area, or allogenic, synthetic. Due to shortage of the donor, painful dissection, and lack of efficacy in synthetic, there is a need for alternative to native blood vessels for transplantation.

METHODS

Human umbilical-cord tissue obtained from the hospital with the informed consent. Umbilical-cord blood vessels were isolated for decellularization and to establish endothelial cell culture. Cultured cells were characterized by immunophenotype, gene expression and in vitro angiogenesis assay. Decellularized blood vessels were recellularized with the endothelial progenitors and Wharton jelly, CL MSCs (1:1), which was characterized by MTT, biomechanical testing, DNA content, SEM and histologically. Bioengineered vessels were transplanted into the animal models to evaluate their effect.

RESULTS

Cultured cells express CD31 and CD14 determining endothelial progenitor cells (EPCs). EPCs expresses various factors such as angiopoitin1, VWF, RANTES, VEGF, BDNF, FGF1, FGF2, HGF, IGF, GDNF, NGF, PLGF, NT3, but fail to express NT4, EGF, and CNTF. Pro and anti-inflammatory cytokine expressions were noticed. Functionally, these EPCs elicit in vitro tube formation. Negligible DNA content and intact ECM confirms the efficient decellularization of tissue. The increased MTT activity in recellularized tissue determines proliferating cells and biocompatibility of the scaffolds. Moreover, significant (P < 0.05) increase in maximum force and tensile of recellularized biomaterial as compared to the decellularized scaffolds. Integration of graft with host tissue, suggesting biocompatible therapeutic biomaterial with cells.

CONCLUSION

EPCs with stem cells in engineered blood vessels could be therapeutically applicable in vascular surgery.

Molecular Analysis of Fetal and Adult Primary Human Liver Sinusoidal Endothelial Cells: A Comparison to Other Endothelial Cells

In humans, Factor VIII (F8) deficiency leads to hemophilia A and F8 is largely synthesized and secreted by the liver sinusoidal endothelial cells (LSECs). However, the specificity and characteristics of these cells in comparison to other endothelial cells is not well known. In this study, we performed genome wide expression and CpG methylation profiling of fetal and adult human primary LSECs together with other fetal primary endothelial cells from lung (micro-vascular and arterial), and heart (micro-vascular). Our results reveal expression and methylation markers distinguishing LSECs at both fetal and adult stages. Differential gene expression of fetal LSECs in comparison to other fetal endothelial cells pointed to several differentially regulated pathways and biofunctions in fetal LSECs. We used targeted bisulfite resequencing to confirm selected top differentially methylated regions. We further designed an assay where we used the selected methylation markers to test the degree of similarity of in-house iPS generated vascular endothelial cells to primary LSECs; a higher similarity was found to fetal than to adult LSECs. In this study, we provide a detailed molecular profile of LSECs and a guide to testing the effectiveness of production of in vitro differentiated LSECs.

The State of Art of Regenerative Therapy in Cardiovascular Ischemic Disease: Biology, Signaling Pathways, and Epigenetics of Endothelial Progenitor Cells

Ischemic heart disease is currently a major cause of mortality and morbidity worldwide. Nevertheless, the actual therapeutic scenario does not target myocardial cell regeneration and consequently, the progression toward the late stage of chronic heart failure is common. Endothelial progenitor cells (EPCs) are bone marrow-derived stem cells that contribute to the homeostasis of the endothelial wall in acute and chronic ischemic disease. Calcium modulation and other molecular pathways (NOTCH, VEGFR, and CXCR4) contribute to EPC proliferation and differentiation. The present review provides a summary of EPC biology with a particular focus on the regulatory pathways of EPCs and describes promising applications for cardiovascular cell therapy.

OPN binds alpha V integrin to promote endothelial progenitor cell incorporation into vasculature

Angiogenesis is fundamental to the expansion of the placental vasculature during pregnancy. Integrins are associated with vascular formation; and osteopontin is a candidate ligand for integrins to promote angiogenesis. Endothelial progenitor cells (EPCs) are released from bone marrow into the blood and incorporate into newly vascularized tissue where they differentiate into mature endothelium. Results of studies in women suggest that EPCs may play an important role in maintaining placental vascular integrity during pregnancy, although little is known about how EPCs are recruited to these tissues. Our goal was to determine the αv integrin mediated effects of osteopontin on EPC adhesion and incorporation into angiogenic vascular networks. EPCs were isolated from 6 h old piglets. RT-PCR revealed that EPCs initially had a monocyte-like phenotype in culture that became more endothelial-like with cell passage. Immunofluorescence microscopy confirmed that the EPCs express platelet endothelial cell adhesion molecule, vascular endothelial cadherin, and von Willebrand factor. When EPCs were cultured on OPN-coated slides, the αv integrin subunit was observed in focal adhesions at the basal surface of EPCs. Silencing of αv integrin reduced EPC binding to OPN and focal adhesion assembly. In vitro siRNA knockdown in EPCs,demonstrated that OPN stimulates EPC incorporation into human umbilical vein endothelial cell (HUVEC) networks via αv-containing integrins. Finally, in situ hybridization and immunohistochemistry localized osteopontin near placental blood vessels. In summary, OPN binds the αv integrin subunit on EPCs to support EPC adhesion and increase EPC incorporation into angiogenic vascular networks.

Postnatal Alveologenesis Depends on FOXF1 Signaling in c-KIT+ Endothelial Progenitor Cells

Rationale: Disruption of alveologenesis is associated with severe pediatric lung disorders, including bronchopulmonary dysplasia (BPD). Although c-KIT+ endothelial cell (EC) progenitors are abundant in embryonic and neonatal lungs, their role in alveolar septation and the therapeutic potential of these cells remain unknown.Objectives: To determine whether c-KIT+ EC progenitors stimulate alveologenesis in the neonatal lung.Methods: We used single-cell RNA sequencing of neonatal human and mouse lung tissues, immunostaining, and FACS analysis to identify transcriptional and signaling networks shared by human and mouse pulmonary c-KIT+ EC progenitors. A mouse model of perinatal hyperoxia-induced lung injury was used to identify molecular mechanisms that are critical for the survival, proliferation, and engraftment of c-KIT+ EC progenitors in the neonatal lung.Measurements and Main Results: Pulmonary c-KIT+ EC progenitors expressing PECAM-1, CD34, VE-Cadherin, FLK1, and TIE2 lacked mature arterial, venal, and lymphatic cell-surface markers. The transcriptomic signature of c-KIT+ ECs was conserved in mouse and human lungs and enriched in FOXF1-regulated transcriptional targets. Expression of FOXF1 and c-KIT was decreased in the lungs of infants with BPD. In the mouse, neonatal hyperoxia decreased the number of c-KIT+ EC progenitors. Haploinsufficiency or endothelial-specific deletion of Foxf1 in mice increased apoptosis and decreased proliferation of c-KIT+ ECs. Inactivation of either Foxf1 or c-Kit caused alveolar simplification. Adoptive transfer of c-KIT+ ECs into the neonatal circulation increased lung angiogenesis and prevented alveolar simplification in neonatal mice exposed to hyperoxia.Conclusions: Cell therapy involving c-KIT+ EC progenitors can be beneficial for the treatment of BPD.

Reduced NRF2 expression suppresses endothelial progenitor cell function and induces senescence during aging

Aging is associated with an increased risk of cardiovascular disease. Numerical and functional declines in endothelial progenitor cells (EPCs) limit their capacity for endothelial repair and promote the development of cardiovascular disease. We explored the effects of nuclear factor (erythroid-derived 2)-like 2 (NRF2) on EPC activity during aging. Both in vitro and in vivo, the biological functioning of EPCs decreased with aging. The expression of NRF2 and its target genes (Ho-1, Nqo-1 and Trx) also declined with aging, while Nod-like receptor protein 3 (NLRP3) expression increased. Aging was associated with oxidative stress, as evidenced by increased reactive oxygen species and malondialdehyde levels and reduced superoxide dismutase activity. Nrf2 silencing impaired the functioning of EPCs and induced oxidative stress in EPCs from young mice. On the other hand, NRF2 activation in EPCs from aged mice protected these cells against oxidative stress, ameliorated their biological dysfunction and downregulated the NLRP3 inflammasome. These findings suggest NRF2 can prevent the functional damage of EPCs and downregulate the NLRP3 inflammasome through NF-κB signaling.

Danhong injection mobilizes endothelial progenitor cells to repair vascular endothelium injury via upregulating the expression of Akt, eNOS and MMP-9

BACKGROUD

Endothelial progenitor cells (EPCs) have been characterized as one of the key effectors of endothelial healing. The effect of Danhong injection (DHI), the most widely prescribed Chinese medicine for coronary heart disease (CHD), on EPCs mobilization remains unclear.

PURPOSE

We aimed to assess the effect of DHI on EPCs mobilization to repair percutaneous coronary intervention (PCI) induced vascular injury, and to investigate the characteristics and potential mechanism of DHI on EPCs mobilization.

METHOD

Forty-two patients with CHD underwent PCI and received stent implantation were enrolled in a Phase II clinical trials. All patients received routine western medical treatment after PCI, patients of DHI group received DHI in addition. The levels of CECs, cytokines (vWF, IL-6, CRP) and EPCs were analyzed at baseline, post-PCI and after treatment. To investigate the characteristics of DHI on EPCs mobilization, 12 healthy volunteers received intravenous infusion of DHI once and the other 12 received for 7 days. EPCs enumeration were done at a series of time points. At last we tested the effect of DHI and three chemical constituents of DHI (danshensu; lithospermic acid, LA; salvianolic acid D, SaD) on EPCs level and expression of Akt, eNOS and MMP-9 in bone marrow cells of myocardial infarction (MI) mice.

RESULTS

In the DHI group the angina symptoms were improved, the levels of cytokines and CECs were reduced; while EPCs population was increased after treatment. In the phase I clinical trials, EPCs counts reached a plateau phase in 9 h and maintained for more than 10 h after a single dose. After continuous administration, EPCs levels plateaued on the 3rd or 4th day, and maintain till 1 day after the withdrawal, then its levels gradually declined. DHI treatment induced a timely dependent mobilization of EPCs. DHI promoted EPCs mobilization via upregulating the expression of Akt, eNOS and MMP-9 in BM. LA and SaD have played a valuable role in EPCs mobilization.

CONCLUSION

These initial results demonstrated that DHI is effective in alleviating endothelial injury and promoting endothelial repair through enhancing EPCs mobilization and revealed the effect feature and possible mechanisms of DHI in mobilizing EPCs.

Hyperinsulinemia impairs functions of circulating endothelial progenitor cells

AIMS

Circulating endothelial progenitor cells (EPCs) play a key role in maintaining endothelial function. Dysfunction of EPCs is associated with the cardiovascular complication of diabetes. The purpose of this study is to investigate the direct effects of hyperinsulinemia on EPCs and the underlying mechanisms.

METHODS

EPCs isolated from healthy adults were cultured with various concentrations of insulin (control group, without insulin; physiological insulin group, 10 nM insulin and hyperinsulinemia group, 100 nM insulin) with or without phosphatidylinositol-3-kinase (PI3-K) inhibitor (LY294002, 5 µM), endothelial nitric oxide synthase (eNOS) inhibitor (L-NG-nitro-arginine methyl ester (L-NAME), 100 µM), sodium nitroprusside (SNP, 25 µM), p38 mitogen-activated protein kinase(MAPK) inhibitor (SB203580, 5 µM) or extracellular signal-regulated kinases (ERK) 1/2 inhibitor (PD98059, 10 µM). Proliferation, tube formation, and apoptosis of EPCs were determined. Expressions of eNOS, PI3-K, protein kinase B (Akt), p38 MAPK, and ERK 1/2 were assessed.

RESULTS

Hyperinsulinemia caused a significant decrease in proliferation and tube formation abilities than control group. Hyperinsulinemia increased apoptosis rate of EPCs than control group. Furthermore, hyperinsulinemia downregulated phosphorylation of eNOS, PI3-K and Akt, and upregulated phosphorylation of p38 MAPK and ERK. SNP could restore impaired tube formation induced by hyperinsulinemia. P38 MAPK inhibitor but not ERK inhibitor could decrease apoptosis induced by hyperinsulinemia.

CONCLUSION

Hyperinsulinemia impaired EPCs' tube formation ability by downregulation of PI-3K/Akt/eNOS pathway. Hyperinsulinemia induced apoptosis of EPCs via upregulation of p38 MAPK.

Bone-marrow-derived endothelial progenitor cells contribute to vasculogenesis of pregnant mouse uterus†

Angiogenesis is essential for cyclic endometrial growth, implantation, and pregnancy maintenance. Vasculogenesis, the formation of new blood vessels by bone marrow (BM)-derived endothelial progenitor cells (EPCs), has been shown to contribute to endometrial vasculature. However, it is unknown whether vasculogenesis occurs in neovascularization of the decidua during pregnancy. To investigate the contribution of BM-derived EPCs to vascularization of the pregnant uterus, we induced non-gonadotoxic submyeloablation by 5-fluorouracil administration to wild-type FVB/N female mice recipients followed by BM transplantation from transgenic mice expressing green fluorescent protein (GFP) under regulation of Tie2 endothelial-specific promoter. Following 1 month, Tie2-GFP BM-transplanted mice were bred and sacrificed at various gestational days (ED6.5, ED10.5, ED13.5, ED18.5, and postpartum). Bone-marrow-transplanted non-pregnant and saline-injected pregnant mice served as controls (n = 5-6/group). Implantation sites were analyzed by flow cytometry, immunohistochemistry, and immunofluorescence. While no GFP-positive EPCs were found in non-pregnant or early pregnant uteri of BM-transplanted mice, GFP-positive EPCs were first detected in pregnant uterus on ED10.5 (0.12%) and increased as the pregnancy progressed (1.14% on ED13.5), peaking on ED18.5 (1.42%) followed by decrease in the postpartum (0.9%). The percentage of endothelial cells that were BM-derived out of the total endothelial cell population in the implantation sites (GFP+CD31+/CD31+) were 9.3%, 15.8%, and 6.1% on ED13.5, ED18.5, and postpartum, respectively. Immunohistochemistry demonstrated that EPCs incorporated into decidual vasculature, and immunofluorescence showed that GFP-positive EPCs colocalized with CD31 in vascular endothelium of uterine implantation sites, confirming their endothelial lineage. Our findings indicate that BM-derived EPCs contribute to vasculogenesis of the pregnant mouse decidua.

Post-MI treatment with G-CSF and EPO-liposome with SLX repairs infarcted myocardium through EPCs mobilization and activation of prosurvival signals in rabbits

We investigated whether combination therapy of G-CSF and erythropoietin (EPO)-liposome with Siaryl Lewis X (SLX) is more cardioprotective than G-CSF or EPO-liposome with SLX alone. For the purpose of generating myocardial infarction (MI), rabbits underwent 30 minutes of coronary occlusion and 14 days of reperfusion. We administered saline (control group, i.v.,), G-CSF (G group, 10 μg/kg/day × 5 days, i.c., starting at 24 hours after reperfusion), EPO-liposome with SLX (LE group, i.v., 2500 IU/kg EPO containing liposome with SLX, immediately after reperfusion), and G-CSF + EPO-liposome with SLX (LE + G group) to the rabbits. The MI size was the smallest in the LE+G group (14.7 ± 0.8%), and smaller in the G group (22.4 ± 1.5%) and LE group (18.5 ± 1.1%) than in the control group (27.8 ± 1.5%). Compared with the control group, the cardiac function and remodeling of the G, LE, and LE + G groups were improved, and LE + G group tended to show the best improvement. The number of CD31-positive microvessels was the greatest in the LE + G group, greater in the G and LE groups than in the control group. Higher expressions of phosphorylated (p)-Akt and p-ERK were observed in the ischemic area of the LE and LE + G groups. The number of CD34+/CXCR4+ cells was significantly higher in the G and LE + G groups. The cardiac SDF-1 was more expressed in the G and LE + G groups. In conclusion, Post-MI combination therapy with G-CSF and EPO-liposome with SLX is more cardioprotective than G-CSF or EPO-liposome with SLX alone through EPCs mobilization, neovascularization, and activation of prosurvival signals.

Regeneration-associated cell transplantation contributes to tissue recovery in mice with acute ischemic stroke

Various cell-based therapeutic strategies have been investigated for vascular and tissue regeneration after ischemic stroke. We have developed a novel cell population, called regeneration-associated cells (RACs), by quality- and quantity-controlled culture of unfractionated mononuclear cells. RACs were trans-arterially injected into 10-week-old syngeneic male mice at 1, 3, 5 or 7 days after permanent middle cerebral artery occlusion (MCAO) to determine the optimal timing for administration in terms of outcome at day 21. Next, we examined the effects of RACs injection at day 1 after MCAO on neurological deficits, infarct volume, and mediators of vascular regeneration and anti-inflammation at days 7 and 21. Infarct volume at day 21 was significantly reduced by transplantation of RACs at day 1 or 3. RACs injected at day 1 reduced the infarct volume at day 7 and 21. Angiogenesis and anti-inflammatory mediators, VEGF and IL-10, were increased at day 7, and VEGF was still upregulated at day 21. We also observed significantly enhanced ink perfusion in vivo, tube formation in vitro, and definitive endothelial progenitor cell colonies in colony assay. These results suggest that RAC transplantation in MCAO models promoted significant recovery of neural tissues through intensified anti-inflammatory and angiogenic effects.

Cellular biology of fracture healing

The biology of bone healing is a rapidly developing science. Advances in transgenic and gene-targeted mice have enabled tissue and cell-specific investigations of skeletal regeneration. As an example, only recently has it been recognized that chondrocytes convert to osteoblasts during healing bone, and only several years prior, seminal publications reported definitively that the primary tissues contributing bone forming cells during regeneration were the periosteum and endosteum. While genetically modified animals offer incredible insights into the temporal and spatial importance of various gene products, the complexity and rapidity of healing-coupled with the heterogeneity of animal models-renders studies of regenerative biology challenging. Herein, cells that play a key role in bone healing will be reviewed and extracellular mediators regulating their behavior discussed. We will focus on recent studies that explore novel roles of inflammation in bone healing, and the origins and fates of various cells in the fracture environment. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Mitochondrial dysfunctions, endothelial progenitor cells and diabetic retinopathy

AIM

Diabetic retinopathy (DR) is the leading cause of vision loss in the working age population. Endothelial progenitor cells (EPC) play a vital role in vascular damage repair. This article will review recent progress regarding mitochondrial and EPC dysfunction associated with DR.

RESULTS

EPCs represent a limited population of adult stem cells possessing vasculogenic potential postnatally; their number and function are changed in DR. Among all the function changes, mitochondrial dysfunction plays an important role in the dysregulation of EPCs, as mitochondria regulate energy balance, and cell fate determination.

CONCLUSIONS

Although the mechanism for the role of mitochondria dysregulation in EPC function remains elusive, mitochondria of EPCs represent a promising target for the treatment of the vasculopathy presented within DR.

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.

Inhibition of endothelial progenitor cells may explain the high cardiovascular event rate in patients with rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) patients may suffer cardiovascular (CV) events much more than the general population, and CV disease is the leading cause of death in patients with RA. Our hypothesis was that impaired function of endothelial progenitor cells may contribute to endothelial dysfunction and the clinical CV events of patients with RA.

METHODS

About 27 RA patients (9 males and 18 females) with an active disease and 13 healthy subjects who served as the control group (nine males and four females) were enrolled to this prospective study. The ability to grow in culture colony-forming units of endothelial progenitor cells (CFU-EPCs) was measured, as well as their endothelial function using high-resolution ultrasonography of the brachial artery, and levels of C reactive protein (CRP) in the serum. For statistical analysis, we used the Student's t-test.

RESULTS

As a group, patients with RA were older (P < 0.0001), had severe endothelial dysfunction (P<0.0001), with impaired ability to grow CFU-EPCs (P<0.0001), and a higher inflammatory state (P = 0001). No difference was observed in BMI. All RA patients had an active disease (DAS28 3.9 ± 0.9) for 9.2 ± 6.5 years. The same differences were observed in both genders.

CONCLUSIONS

Patients with RA had an impaired ability to grow EPCs and severe endothelial dysfunction. Inability to grow colonies of EPCs reflects the impaired regenerative capacity of patients with RA and may explain the endothelial dysfunction and the high CV event rate among patients with RA.

Endothelial Progenitor Cells and Kidney Diseases

Endothelial progenitor cells (EPC) are bone marrow derived or tissue-resident cells that play major roles in the maintenance of vascular integrity and repair of endothelial damage. Although EPCs may be capable of directly engrafting and regenerating the endothelium, the most important effects of EPCs seem to be depended on paracrine effects. In recent studies, specific microvesicles and mRNAs have been found to mediate the pro-angiogenic and regenerative effects of EPCs on endothelium. EPC counts have important prognostic implications in cardiovascular diseases (CVD). Uremia and inflammation are associated with lower EPC counts which probably contribute to increased CVD risks in patients with chronic kidney disease. Beneficial effects of the EPC therapies have been shown in studies performed on different models of CVD and kidney diseases such as acute and chronic kidney diseases and glomerulonephritis. However, lack of a clear definition and specific marker of EPCs is the most important problem causing difficulties in interpretation of the results of the studies investigating EPCs.

Imbalance between endothelial damage and repair capacity in chronic obstructive pulmonary disease

Background

Circulating endothelial microparticles (EMPs) and progenitor cells (PCs) are biological markers of endothelial function and endogenous repair capacity. The study was aimed to investigate whether COPD patients have an imbalance between EMPs to PCs compared to controls and to evaluate the effect of cigarette smoke on these circulating markers.

Methods

Circulating EMPs and PCs were determined by flow cytometry in 27 nonsmokers, 20 smokers and 61 COPD patients with moderate to severe airflow obstruction. We compared total EMPs (CD31⁺CD42b^-), apoptotic if they co-expressed Annexin-V⁺ or activated if they co-expressed CD62E⁺, circulating PCs (CD34⁺CD133⁺CD45⁺) and the EMPs/PCs ratio between groups.

Results

COPD patients presented increased levels of total and apoptotic circulating EMPs, and an increased EMPs/PCs ratio, compared with nonsmokers. Women had less circulating PCs than men through all groups and those with COPD showed lower levels of PCs than both control groups. In smokers, circulating EMPs and PCs did not differ from nonsmokers, being the EMPs/PCs ratio in an intermediate position between COPD and nonsmokers.

Conclusions

We conclude that COPD patients present an imbalance between endothelial damage and repair capacity that might explain the frequent concurrence of cardiovascular disorders. Factors related to the disease itself and gender, rather than cigarette smoking, may account for this imbalance.

Effects of Hypoglycemia on Circulating Stem and Progenitor Cells in Diabetic Patients

CONTEXT

Iatrogenic hypoglycemia is the most common acute diabetic complication, and it significantly increases morbidity. In people with diabetes, reduction in the levels of circulating stem and progenitor cells predicts adverse outcomes.

OBJECTIVE

To evaluate whether hypoglycemia in diabetes affects circulating stem cells and endothelial progenitor cells (EPCs).

DESIGN

We performed an experimental hypoglycemia study (Study 1) and a case-control study (Study 2).

SETTING

Tertiary referral inpatient clinic.

PATIENTS AND OTHER PARTICIPANTS

Type 1 diabetic patients (Study 1, n = 19); diabetic patients hospitalized for severe iatrogenic hypoglycemia, matched inpatient and outpatient controls (Study 2, n = 22/group).

INTERVENTIONS

Type 1 diabetic patients underwent two in-hospital sessions of glucose monitoring during a breakfast meal with or without induction of hypoglycemia in random order. In Study 2, patients hospitalized for hypoglycemia and matched controls were compared.

MAIN OUTCOME MEASURE

Circulating stem cells and EPCs were measured by flow cytometry based on the expression of CD34 and kinase insert domain receptor (KDR).

RESULTS

In Study 1, the physiologic decline of CD34+KDR+ EPCs from 8 am to 2 pm was abolished by insulin-induced hypoglycemia in type 1 diabetic patients. In Study 2, diabetic patients hospitalized for severe iatrogenic hypoglycemia had significantly lower levels of CD34+ stem cells and CD34+KDR+ EPCs compared with diabetic inpatients or outpatient controls.

CONCLUSIONS

In diabetic patients, a single mild hypoglycemic episode can compromise the physiologic EPC fluctuation, whereas severe hypoglycemia is associated with a marked reduction in stem cells and EPCs. These data provide a possible link between hypoglycemia and adverse outcomes of diabetes.

Correlation between NADPH oxidase-mediated oxidative stress and dysfunction of endothelial progenitor cell in hyperlipidemic patients

BACKGROUND/AIMS

NADPH (nicotinamide adenine dinucleotide phosphate) oxidase (NOX)-mediated oxidative stress plays a key role in promotion of oxidative injury in the cardiovascular system. The aim of this study is to evaluate the status of NOX in endothelial progenitor cells (EPCs) of hyperlipidemic patients and to assess the correlation between NOX activity and the functions EPCs.

METHODS

A total of 30 hyperlipidemic patients were enrolled for this study and 30 age-matched volunteers with normal level of plasma lipids served as controls. After the circulating EPCs were isolated, the EPC functions (migration, adhesion and tube formation) were evaluated and the status of NOX (expression and activity) was examined.

RESULTS

Compared to the controls, hyperlipidemic patients showed an increase in plasma lipids and a reduction in EPC functions including the attenuated abilities in adhesion, migration and tube formation, concomitant with an increase in NOX expression (NOX2 and NOX4), NOX activity, and reactive oxygen species production. The data analysis showed negative correlations between NOX activity and EPC functions.

CONCLUSIONS

There is a positive correlation between the NOX-mediated oxidative stress and the dysfunctions of circulating EPCs in hyperlipidemic patients, and suppression of NOX might offer a novel strategy to improve EPCs functions in hyperlipidemia.

Methylglyoxal induced advanced glycation end products (AGE)/receptor for AGE (RAGE)-mediated angiogenic impairment in bone marrow-derived endothelial progenitor cells

Endothelial cells (ECs) maintain the structure and function of blood vessels and are readily exposed to exogenous and endogenous toxic substances in the circulatory system. Bone marrow-derived endothelial progenitor cells (EPCs) circulate in the blood and differentiate to EC, which are known to participate in angiogenesis and regeneration of injured vessels. Dysfunction in EPC contributes to cardiovascular complications in patients with diabetes, but the precise molecular mechanisms underlying diabetic EPC abnormalities are not completely understood. The aim of this study was to investigate the mechanisms underlying diabetic EPC dysfunction using methylglyoxal (MG), an endogenous toxic diabetic metabolite. Data demonstrated that MG decreased cell viability and protein expression of vascular endothelial growth factor receptor (VEGFR)-2 associated with functional impairment of tube formation in EPC. The generation of advanced glycation end (AGE) products was increased in EPC following exposure to MG. Blockage of receptor for AGE (RAGE) by FPS-ZM1, a specific antagonist for RAGE, significantly reversed the decrease of VEGFR-2 protein expression and angiogenic dysfunction in MG-incubated EPC. Taken together, data demonstrated that MG induced angiogenic impairment in EPC via alterations in the AGE/RAGE-VEGFR-2 pathway which may be utilized in the development of potential therapeutic and preventive targets for diabetic vascular complications.

Transplantation of in vitro cultured endothelial progenitor cells repairs the blood-brain barrier and improves cognitive function of APP/PS1 transgenic AD mice

To date, the pathogenesis of Alzheimer's disease (AD) remains unclear. It is well-known that excessive deposition of Aβ in the brain is a crucial part of the pathogenesis of AD. In recent years, the AD neurovascular unit hypothesis has attracted much attention. Impairment of the blood-brain barrier (BBB) leads to abnormal amyloid-β (Aβ) transport, and chronic cerebral hypoperfusion causes Aβ deposition throughout the onset and progression of AD. Endothelial progenitor cells (EPCs) are the universal cells for repairing blood vessels. Our previous studies have shown that a reduced number of EPCs in the peripheral blood results in cerebral vascular repair disorder, cerebral hypoperfusion and neurodegeneration, which might be related to the cognitive dysfunction of AD patients. This study was designed to confirm whether EPCs transplantation could repair the blood-brain barrier, stimulate angiogenesis and reduce Aβ deposition in AD. The expression of ZO-1, Occludin and Claudin-5 was up-regulated in APP/PS1 transgenic mice after hippocampal transplantation of EPCs. Consistent with previous studies, EPC transplants also increased the microvessel density. We observed that Aβ senile plaque deposition was decreased and hippocampal cell apoptosis was reduced after EPCs transplantation. The Morris water maze test showed that spatial learning and memory functions were significantly improved in mice transplanted with EPCs. Consequently, EPCs could up-regulate the expression of tight junction proteins, repair BBB tight junction function, stimulate angiogenesis, promote Aβ clearance, and decrease neuronal loss, ultimately improve cognitive function. Taken together, these data demonstrate EPCs may play an important role in the therapeutic implications for vascular dysfunction in AD.

The effects of physical therapy with neuromuscular electrical stimulation in patients with septic shock: Study protocol for a randomized cross-over design

INTRODUCTION

Septic shock is a potentially fatal organ dysfunction caused by an imbalance of the host response to infection. The changes in microcirculation during sepsis can be explained by the alterations in the endothelial barrier function. Endothelial progenitor cells (EPCs) are a potential recovery index of endothelial function and it an increase in response to neuromuscular electrical stimulation (NMES) was demonstrated. Therefore, the objective of this study is to investigate the effects of NMES in patients with septic shock.

METHODS AND ANALYSIS

It is a study protocol for a randomized cross-over design in an intensive care unit of a tertiary University hospital. Thirty-one patients aged 18 to 65 years. The study will be divided in 2 phases: the phase one will be held in the first 72 hours of septic shock and the phase two after 3 days of first assessment. Patients will be randomly selected to the intervention protocol (decubitus position with the limbs raised and NMES) and control protocol (decubitus position with the limbs raised without NMES). After this procedure, the patients will be allocated in group 1 (intervention and control protocol) or group 2 (control and intervention protocol) with a wash-out period of 4 to 6 hours between them. The main outcome is mobilization of EPCs. The secondary outcome is metabolic and hemodynamic data. A linear mixed model will be used for analysis of dependent variables and estimated values of the mean of the differences of each effect.

Aging process, adherence to Mediterranean diet and nutritional status in a large cohort of nonagenarians: Effects on endothelial progenitor cells

BACKGROUND AND AIM

Adherence to the Mediterranean Diet (MD) has been associated with a longer and better life. The aim of this study was to examine the effects of adherence to the MD, and of nutritional habits on endothelial progenitor (EPCs) and circulating progenitor (CPCs) cells in a cohort of nonagenarians enrolled within the Mugello Study, an epidemiological study aimed at investigating both clinically relevant geriatric items and various health issues, including those related to nutritional status.

METHODS AND RESULTS

Four hundred twenty-one nonagenarians (306 F, 115 M, mean age: 93.1 ± 3.2 years) were evaluated. Adherence to MD was assessed through the Mediterranean Diet Score. Elderly subjects who were in the fourth quartile of the Mediterranean diet score showed significantly higher EPCs than subjects grouped into the other three quartiles. After adjustment for confounders, elderly subjects who were in the highest quartile of adherence to the MD score reported to have EPCs' levels significantly higher than those who reported lower values of adherence to the MD. Furthermore, by analyzing different food categories, it was reported that daily consumption of olive oil and a higher consumption of fruit and vegetables showed higher CPCs CD34⁺ and EPCs CD34⁺/KDR⁺ than subjects with not daily or lower consumption.

CONCLUSION

Our results support the hypothesis that the adherence to MD, as well as a daily consumption of olive oil and fruit and vegetables, characteristics of MD, may protect against the development of endothelial dysfunction through increasing EPCs and CPCs in older age.

In vitro model of vasculo-angiogenesis: demonstration that bone marrow derived endothelial progenitor cells form new hybrid capillary blood vessels jointly with gastric endothelial cells

Regeneration of blood vessels (neovascularization) is critical for tissue injury healing. The contribution of bone marrow-derived endothelial progenitor cells (BMD-EPCs) to neovascularization during tissue injury healing is not fully elucidated and it is not clear whether BMD-EPCs can form new capillary blood vessels independently or jointly with fully differentiated endothelial cells (ECs). The aim of this study was to establish an in vitro model of vasculogenesis/angiogenesis by co-culture of BMD-EPCs and gastric endothelial cells (GECs) on Matrigel, examine direct interactions of these cells; and, identify the mechanisms involved. We isolated BMD-EPCs and GECs from bone marrow and stomach of rats, respectively. In these cells, we examined the expression of CD34, CD133, CD31, VEGF-R2, stromal derived factor 1 (SDF-1) and CXCR4, and, their ability to form capillary-like tubes when cultured separately or when co-cultured (1:5 ratio) on growth factor-reduced Matrigel. Fluorescence-labeled BMD-EPCs seeded alone on Matrigel formed capillary-like tubes reflecting in vitro vasculogenesis, and when co-cultured with GECs on Matrigel, formed 'hybrid' tubes containing BMD-EPCs nested between GECs thus reflecting in vitro angio-vasculogenesis. These 'hybrid' tubes were 1.5-fold wider (P < 0.001) and had more extensive (5.1-fold increase) loops (P < 0.01) at the junctions of BMD-EPCs and GECs versus tubes formed by GECs alone. GECs expressed SDF-1 that likely mediated homing of BMD-EPCs (which expressed the SDF-1 receptor, CXCR4) and their incorporation during neovascularization. BMD-EPCs can independently form capillary-like tubes on Matrigel, and when co-cultured with fully differentiated ECs on Matrigel, form capillary-like 'hybrid' tubes comprised of both cell types. Both BMD-EPCs and GECs express SDF-1 and CXCR4, which indicate direct paracrine interactions between these cells during neovascularization.

Endothelial progenitor cell subsets and preeclampsia: Findings and controversies

Vascular remodeling is an essential component of gestation. Endothelial progenitor cells (EPCs) play an important role in the regulation of vascular homeostasis. The results of studies measuring the number of EPCs in normal pregnancies and in preeclampsia have been highly controversial or even contradictory because of some variations in technical issues and different methodologies enumerating three distinct subsets of EPCs: circulating angiogenic cells (CAC), colony forming unit endothelial cells (CFU-ECs), and endothelial colony-forming cells (ECFCs). In general, most studies have shown an increase in the number of CACs in the maternal circulation with a progression in the gestational age in normal pregnancies, while functional capacities measured by CFU-ECs and ECFCs remain intact. In the case of preeclampsia, mobilization of CACs and ECFCs occurs in the peripheral blood of pregnant women, but the functional capacities shown by culture of the derived colony-forming assays (CFU-EC and ECFC assays) are altered. Furthermore, the number of all EPC subsets will be reduced in umbilical cord blood in the case of preeclampsia. As EPCs play an important role in the homeostasis of vascular networks, the difference in their frequency and functionality in normal pregnancies and those with preeclampsia can be expected. In this review, there was an attempt to provide a justification for these controversies.

Evaluation of the effect of sildenafil on the microvascular blood flow in patients with systemic sclerosis: a randomised, double-blind, placebo-controlled study

OBJECTIVES

To evaluate the effect of sildenafil as add-on therapy on the microvascular blood flow in patients with Raynaud's phenomenon (RP) secondary to systemic sclerosis (SSc).

METHODS

In this double-blind, placebo-controlled study, 41 patients with RP secondary to SSc were randomly assigned to receive oral sildenafil 100 mg/day (21 patients, mean age 47.2 years) or placebo (20 patients, mean age 41.6 years) for 8 weeks. Patients were evaluated at baseline, 8 weeks after treatment, and 2 weeks after the end of the treatment. The primary outcome measures were the mean changes in finger blood flow (FBF) measured using laser Doppler imaging before and after cold stimulus at 8 weeks of treatment. Secondary endpoints included frequency and duration of RP attacks, Visual Analog Scale (VAS) score for RP severity, Raynaud's condition score, and serum levels of VEGF and endothelial progenitor cells (EPCs).

RESULTS

After 8 weeks of treatment, the sildenafil group presented a significantly higher mean percentage change from baseline in FBF before cold stimulus (p=0.026), and in FBF after cold stimulus (p=0.028) compared with the placebo group. There was a significant improvement in the duration of RP and in the percentage change from baseline to week 8 in the RP VAS score in sildenafil compared with placebo. There were no changes in EPCs and VEGF levels after treatment in either group.

CONCLUSIONS

Sildenafil improved digital blood flow and RP symptoms in SSc patients after 8 weeks of treatment, and might be a good therapeutic option for secondary RP.

Formation of new blood vessels during gastric ulcer healing. Role of bone marrow derived endothelial progenitor cells

Regeneration of blood vessels (neovascularization) is critical for gastric ulcer (GU) healing. The contributions of bone marrow-derived endothelial progenitor cells (BMD-EPCs) to neovascularization during GU healing are not fully elucidated. Our specific aims were to determine whether in GU, BMD-EPCs are incorporated into blood vessels of GU granulation tissue jointly with ECs, thus forming hybrid vessels; or, form separate vessels consisting of only BMD-EPCs. GUs were induced in rats by serosal application of acetic acid. Vascular cast studies were performed at 7, 21 and 60 days after GU induction and tissue specimens were immunostained for CD34, CD133, VEGFR2, and SDF-1 at 14 days. Human relevance was determined using archival human GU specimens. In rat GU granulation tissue BMD-EPCs constituted 28 ± 3% of all cells lining newly formed blood vessels, and were nested between fully differentiated ECs. In rat GU granulation tissue, expression of stromal derived factor-1 (SDF-1) - the major chemoattractant for BMD-EPCs was strongly upregulated. In human GU specimens, BMD-EPCs were also present in granulation tissue constituting 34 ± 3% of all cells lining blood vessels and jointly formed hybrid vessels with differentiated ECs. Our study uncovered that BMD-EPCs incorporate into newly formed blood vessels in GU granulation tissue; and, together with ECs of pre-existing vessels, contribute to and support neovascularization through vasculogenesis. This study is the first demonstration that vasculogenesis occurs during GU healing in both humans and in rats.

Endothelial progenitor cells dysfunction and impaired tissue reparation: The missed link in diabetes mellitus development

Diabetes mellitus (DM) is considered a leading cause of premature cardiovascular (CV) mortality and morbidity in general population and in individuals with known CV disease. Recent animal and clinical studies have shown that reduced number and weak function of endothelial progenitor cells (EPCs) may not only indicate to higher CV risk, but contribute to the impaired heart and vessels reparation in patients with DM. Moreover, EPCs having a protective impact on the vasculature may mediate the functioning of other organs and systems. Therefore, EPCs dysfunction is probably promising target for DM treatment strategy, while the role of restoring of EPCs number and functionality in CV risk diminish and reduce of DM-related complications is not fully clear. The aim of the review is summary of knowledge regarding EPCs dysfunction in DM patients.

Shear stress-mediated upregulation of GTP cyclohydrolase/tetrahydrobiopterin pathway ameliorates hypertension-related decline in reendothelialization capacity of endothelial progenitor cells

OBJECTIVES

Guanosine triphosphate cyclohydrolase/tetrahydrobiopterin (GTPCH)/(BH4) pathway has been proved to regulate the function of endothelial progenitor cells (EPCs) in deoxycorticosterone acetate-salt hypertensive mice, indicating that GTPCH/BH4 pathway may be an important repair target for hypertension-related endothelial injury. Shear stress is an important nonpharmacologic strategy to modulate the function of EPCs. Here, we investigated the effects of laminar shear stress on the GTPCH/BH4 pathway and endothelial repair capacity of circulating EPCs in hypertension.

METHOD

Laminar shear stress was loaded on the human EPCs from hypertensive patients and normotensive patients. The in-vitro function, in-vivo reendothelialization capacity and GTPCH/BH4 pathway of human EPCs were evaluated.

RESULTS

Both in-vitro function and reendothelialization capacity of EPCs were lower in hypertensive patients than that in normotensive patients. The GTPCH/BH4 pathway of EPCs was downregulated in hypertensive patients. Shear stress increased in-vitro function and reendothelialization capacity of EPCs from hypertensive patients and normotensive patients. Furthermore, shear stress upregulated the expression of GTPCH I and levels of BH4, nitric oxide, and cGMP of EPCs, and reduced thrombospondin-1 expression. With treatment of GTPCH knockdown or nitroarginine methyl ester inhibition, shear stress-induced increased levels of BH4, nitric oxide and cGMP of EPCs was suppressed. When GTPCH/BH4 pathway of EPCs was blocked, the effects of shear stress on in-vitro function and reendothelialization capacity of EPCs were inhibited.

CONCLUSION

The study demonstrates for the first time that shear stress-induced upregulation of the GTPCH/BH4 pathway ameliorates hypertension-related decline in endothelial repair capacity of EPCs. These findings provide novel nonpharmacologic therapeutic approach for hypertension-related endothelial repair.

Endothelial progenitor cells from human fetal aorta cure diabetic foot in a rat model

OBJECTIVE

Recent evidence has suggested that circulating endothelial progenitor cells (EPCs) can repair the arterial endothelium during vascular injury. However, a reliable source of human EPCs is needed for therapeutic applications. In this study, we isolated human fetal aorta (HFA)-derived EPCs and analyzed the capacity of EPCs to differentiate into endothelial cells. In addition, because microvascular dysfunction is considered to be the major cause of diabetic foot (DF), we investigated whether transplantation of HFA-derived EPCs could treat DF in a rat model.

METHODS

EPCs were isolated from clinically aborted fetal aorta. RT-PCR, fluorescence-activated cell sorting, immunofluorescence, and an enzyme-linked immunosorbent assay were used to examine the expressions of CD133, CD34, CD31, Vascular Endothelial Growth Factor Receptor 2 (VEGFR2), von Willebrand Factor (vWF), and Endothelial Leukocyte Adhesion Molecule-1 (ELAM-1). Morphology and Dil-uptake were used to assess function of the EPCs. We then established a DF model by injecting microcarriers into the hind-limb arteries of Goto-Kakizaki rats and then transplanting the cultured EPCs into the ischemic hind limbs. Thermal infrared imaging, oxygen saturation apparatus, and laser Doppler perfusion imaging were used to monitor the progression of the disease. Immunohistochemistry was performed to examine the microvascular tissue formed by HFA-derived EPCs.

RESULTS

We found that CD133, CD34, and VEGFR2 were expressed by HFA-derived EPCs. After VEGF induction, CD133 expression was significantly decreased, but expression levels of vWF and ELAM-1 were markedly increased. Furthermore, tube formation and Dil-uptake were improved after VEGF induction. These observations suggest that EPCs could differentiate into endothelial cells. In the DF model, temperature, blood flow, and oxygen saturation were reduced but recovered to a nearly normal level following injection of the EPCs in the hind limb. Ischemic symptoms also improved. Injected EPCs were preferentially and durably engrafted into the blood vessels. In addition, anti-human CD31+-AMA+-vWF+ microvasculars were detected after transplantation of EPCs.

CONCLUSION

Early fetal aorta-derived EPCs possess strong self-renewal ability and can differentiate into endothelial cells. We demonstrated for the first time that transplanting HFA-derived EPCs could ameliorate DF prognosis in a rat model. These findings suggest that the transplantation of HFA-derived EPCs could serve as an innovative therapeutic strategy for managing DF.

Circulating Progenitor Cells Affect Thrombosis of Dialysis Arteriovenous Fistulas

BACKGROUND

Arteriovenous fistula (AVF) thrombosis is a relevant cause of morbidity in hemodialysis (HD) patients. The number of circulating endothelial progenitor cells (EPCs) has been identified as a surrogate marker for vascular repair and health. Deficiency of EPCs has been demonstrated in dialysis patients to be associated with vascular events. Nonetheless, their role in thrombosis of AVFs remains unknown.

METHODS

From January 2010 to May 2013, 147 HD patients with dysfunctional AVFs were enrolled. Surface makers including CD34, KDR and CD133 were used in combination to determine the number of circulating EPCs. All participants were prospectively followed at 6-month interval until December 2015. The primary outcome was thrombosis of dialysis AVFs.

RESULTS

The median follow-up was 47 months, within which 42 patients experienced at least one episode of AVF thrombosis. Patients with AVF thrombosis had lower CD34+KDR+ cell counts compared with patients without thrombosis (median 5 vs. 13 per 150,000 mononuclear cells, p < 0.001). Kaplan-Meier analysis demonstrated an inverse relationship between CD34+KDR+ cell count tertiles and thrombosis-free patency (59, 69 and 86% for low, middle and high tertiles; p = 0.02). Using Cox regression analysis, AVF thrombosis was predicted by baseline CD34+KDR+ cell counts (hazards ratio (HR) 0.963, 95% CI 0.928-1.000, p = 0.05) and tertiles (high vs. low, HR 3.266, 95% CI 1.380-7.728, p < 0.01). In multivariate analysis, only CD34+KDR+ cell tertiles, C-reactive protein and lesion length remained independent predictors for thrombosis.

CONCLUSION

Our study demonstrated an independently reverse association between circulating EPCs and thrombosis of dialysis AVFs. Further studies are warranted to ascertain whether EPCs serve as a marker or a therapeutic target for AVF thrombosis.

Early Endothelial Progenitor Cells (eEPCs) in systemic sclerosis (SSc) - dynamics of cellular regeneration and mesenchymal transdifferentiation

BACKGROUND

Patients with systemic sclerosis (SSc) are endagered by tissue fibrosis and by microvasculopathy, with the latter caused by endothelial cell expansion/proliferation. SSc-associated fibrosis potentially results from mesenchymal transdifferentiation of endothelial cells. Early Endothelial Progenitor Cells (eEPCs) act proangiogenic under diverse conditions. Aim of the study was to analyze eEPC regeneration and mesenchymal transdifferentiation in patients with limited and diffuse SSs (lSSc and dSSc).

METHODS

Patients with both, lSSc and dSSc were included into the study. The following parameters were evaluated: eEPC numbers and regeneration, concentrations of vasomodulatory mediators, mesenchymal properties of blood-derived eEPC. Serum samples of healthy subjects and SS patients were used for stimulation of cultured human eEPC, subsequently followed by analysis of mesenchymal cell characteristics and mobility.

RESULTS

Twenty-nine patients were included into the study. Regenerative activity of blood-derived eEPCs did not differ between Controls and patients. Circulating eEPC were significantly lower in all patients with SSc, and in limited and diffuse SSc (lSSc/dSSc). Serum concentrations of promesenchymal TGF-b was elevated in all patients with SSc. Cultured mononuclear cells from SS patients displayed higher abundances of CD31 and of CD31 and aSMA combined. Finally, serum from SSc patients inhibited migration of cultured eEPCs and the cells showed lower sensitivity towards the endothelin antagonist Bosentan.

CONCLUSIONS

The eEPC system, which represents an essential element of the endogenous vascular repair machinery is affected in SSc. The increased appearance of mesenchymal properties in eEPC may indicate that alterations of the cells potentially contribute to the accumulation of connective tissue and to vascular malfunction.

Regulatory roles of interferon-inducible protein 204 on differentiation and vasculogenic activity of endothelial progenitor cells

BACKGROUND

Endothelial progenitor cells (EPCs) have shown great potential in angiogenesis either by their differentiation into endothelial cells or by secretion of angiogenic factors. Interferon-inducible protein 204 (Ifi204) has been reported to participate in the regulation of cell growth and differentiation. However, its role in differentiation of EPCs remains unknown. We proposed that Ifi204 could modulate the differentiation and regenerative abilities of EPCs.

METHODS

Ifi204-expressing lentivirus and Ifi204 siRNA were introduced into EPCs to overexpress and suppress the expression of Ifi204. Using fluorescence-activated cell sorting, immunocytochemistry, and quantitative PCR, endothelial markers including CD31, VE-cadherin, and vWF were detected in the modified EPCs. An in-vitro incorporation assay and a colony-forming assay were also performed.

RESULTS

Evidence showed that Ifi204 inhibition decreased the endothelial differentiation and vasculogenic activities of EPCs in vitro. In mice with hindlimb ischemia, downregulation of Ifi204 in EPCs, which was tracked by our newly synthesized nanofluorogen, impaired neovascularization, with a corresponding reduction in hindlimb blood reperfusion by postoperative day 14.

CONCLUSIONS

Ifi204 is required for EPC differentiation and neovascularization in vitro and in vivo. The regulatory roles of Ifi204 in EPC differentiation may benefit the clinical therapy of ischemic vascular diseases.

Endothelial Progenitor Cells Combined with Cytosine Deaminase-Endostatin for Suppression of Liver Carcinoma

Transplantation of gene transfected endothelial progenitor cells (EPCs) provides a novel method for treatment of human tumors. To study treatment of hepatocellular carcinoma using cytosine deaminase (CD)- and endostatin (ES)-transfected endothelial progenitor cells (EPCs), mouse bone marrow-derived EPCs were cultured and transfected with Lenti6.3-CD-EGFP and Lenti6.3-ES-Monomer-DsRed labeled with superparamagnetic iron oxide (SPIO) nanoparticles. DiD (lipophilic fluorescent dye)-labeled EPCs were injected into normal mice and mice with liver carcinoma. The EPCs loaded with CD-ES were infused into the mice through caudal veins and tumor volumes were measured. The tumor volumes in the EPC + SPIO + CD/5-Fc + ES group were found to be smaller as a result and grew more slowly than those from the EPC + SPIO + LV (lentivirus, empty vector control) group. Survival times were also measured after infusion of the cells into the mice. The median survival time was found to be longer in the EPC + SPIO + CD/5-Fc + ES group than in the others. In conclusion, the EPCs transfected with CD-ES suppressed the liver carcinoma cells in vitro, migrated primarily to the carcinoma, inhibited tumor growth, and also extended the median survival time for the mice with liver carcinoma.

Endothelial progenitor cells participation in cardiovascular and kidney diseases: a systematic review

Endothelial progenitor cells (EPCs) represent a small population of blood cells (5-40 cells/mm(3)), with an ability to differentiate into endothelial cells that form the lining of the blood vessels and contribute to postnatal angiogenesis. Abundant evidence shows that recruitment of EPCs from the bone marrow, the monocyte/macrophage lineage and the organs facilitate the endothelial regeneration and repair. Changes in the number of EPCs were observed in both, chronic kidney and cardiovascular diseases. Thus, these cells were tested for usage in diagnosis and therapy. In this paper, we review the current knowledge on the EPC biology and contribution of these cells to the kidney and cardiovascular diseases.

Biphasic response in number of stem cells and endothelial progenitor cells after left ventricular assist device implantation: A 6month follow-up

BACKGROUND

Continuous blood flow could have deleterious effects on endothelium and vascular health. This could have serious consequences in patients with heart failure treated with continuous flow left ventricular assist devices (LVAD). Therefore, we studied effect of LVAD on three circulating vascular biomarkers: stem cells (SC), endothelial progenitor cells (EPC) and microparticles (MP).

METHODS

In 23 patients (5 women) with end-stage heart failure, SC, EPC and MP were measured before, and 3 and 6months after implantation of LVAD (HeartMate II). SC were defined using determination of surface antigen expression as mononuclear CD34+/CD45low+ cells and EPC as mononuclear CD34+/CD45low+/KDR+ cells. MP concentrations were determined by ELISA method.

RESULTS

Three months after LVAD implantation numbers of SC and EPC significantly decreased (p=0.01 and p=0.001, respectively). On the contrary, between 3rd and 6th month after implantation they significantly increased (p=0.006 and p=0.003, respectively).MP did not change significantly during the study despite exerting similar trend as SC and EPC.

CONCLUSIONS

Observed biphasic changes of SC and EPC might reflect two processes. First, shortly after LVAD implantation, improved tissue perfusion could lead to decrease in ischemic stimuli and ensuing decrease of SC and EPC. Second, continuous flow between 3rd and 6th month produced by LVAD could lead to increase of SC and EPC through activation of endothelium. This explanation could be supported also by similar trend in the changes of concentrations of MP.

The association of endothelial progenitor cell markers with arteriovenous fistula maturation in hemodialysis patients

AIMS

Arteriovenous fistula (AVF) failure is one of the most important clinical problems in end-stage renal disease. Endothelial progenitor cells (EPCs) have a role on vascular angiogenesis and endothelialization. We aimed to investigate the association markers of EPCs on AVF maturation by measuring the surface expressions of CD34, CD309 and CD133 on the monocytes.

METHODS

This prospective observational study was conducted in 54 voluntary patients with end-stage renal disease who were admitted for their first renal replacement therapy and were available for AVF creation. Venography was performed in all patients before AVF creation. Six patients were excluded due to inadequate veins after venographic imaging, and also seven patients were excluded due to postoperative thrombosis. The blood samples were analyzed a day before the fistula operation, and the expressions of CD34, CD133 and CD309 on the surface of monocytes were measured.

RESULTS

Patients were divided into two groups after the evaluation of AVF maturation, as the mature group and the failure group. The CD309 expression level on the monocytes was 338.00 (35.00-479.00) in the mature group; however, it was 36.00 (5.50-237.00) (p 0.031) in the failure group. Multiple logistic regression analyses showed that both BMI and the mean fluorescence intensity level of CD309 expression on monocytes independently predicted AVF maturation.

CONCLUSIONS

The presence of DM and increased BMI negatively correlated with AVF maturation. High intensity of CD309 expression on monocytes was observed in patients with successful AVF maturation.

Evaluation of in vitro and in vivo biocompatibility of a myo-inositol hexakisphosphate gelated polyaniline hydrogel in a rat model

Recent advances in understanding the interaction between electricity and cells/biomolecules have generated great interest in developing biocompatible electrically conductive materials. In this study, we investigated the biocompatibility of a myo-inositol hexakisphosphate gelated polyaniline hydrogel using in vitro and in vivo experiments in a rat model. The polyaniline hydrogel was used to coat a polycaprolactone scaffold and was cultured with rat endothelial progenitor cells differentiated from rat adipose-derived stem cells. Compared with the control sample on a pristine polycaprolactone scaffold, the treated polyaniline hydrogel had the same non-poisonous/cytotoxicity grade, enhanced cell adhesion, and a higher cell proliferation/growth rate. In implant studies, the polyaniline hydrogel sample induced milder inflammatory responses than did the control at the same time points. Combining the advantages of a biocompatible hydrogel and an organic conductor, the inositol phosphate-gelated polyaniline hydrogel could be used in bioelectronics applications such as biosensors, neural probes, cell stimulators, medical electrodes, tissue engineering, and electro-controlled drug delivery.

Concise Review: Endothelial Progenitor Cells in Regenerative Medicine: Applications and Challenges

Endothelial progenitor cells (EPCs) are currently being studied as candidate cell sources for revascularization strategies. Significant advances have been made in understanding the biology of EPCs, and preclinical studies have demonstrated the vasculogenic, angiogenic, and beneficial paracrine effects of transplanted EPCs in the treatment of ischemic diseases. Despite these promising results, widespread clinical acceptance of EPCs for clinical therapies remains hampered by several challenges. The present study provides a concise summary of the different EPC populations being studied for ischemic therapies and their known roles in the healing of ischemic tissues. The challenges and issues surrounding the use of EPCs and the current strategies being developed to improve the harvest efficiency and functionality of EPCs for application in regenerative medicine are discussed.

SIGNIFICANCE

Endothelial progenitor cells (EPCs) have immense clinical value for cardiovascular therapies. The present study provides a concise description of the EPC subpopulations being evaluated for clinical applications. The current major lines of investigation involving preclinical and clinical evaluations of EPCs are discussed, and significant gaps limiting the translation of EPCs are highlighted. The present report could be useful for clinicians and clinical researchers with interests in ischemic therapy and for basic scientists working in the related fields of tissue engineering and regenerative medicine.

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.

Abnormal phosphorylation of Tie2/Akt/eNOS signaling pathway and decreased number or function of circulating endothelial progenitor cells in prehypertensive premenopausal women with diabetes mellitus

BACKGROUNDS

The number and activity of circulating endothelial progenitor cells (EPCs) in prehypertension is preserved in premenopausal women. However, whether this favorable effect still exists in prehypertensive premenopausal women with diabetes is not clear.

METHODS

This study compared the number and functional activity of circulating EPCs in normotensive or prehypertensive premenopausal women without diabetes mellitus and normotensive or prehypertensive premenopausal women with diabetes mellitus, evaluated the vascular endothelial function in each groups, and investigated the possible underlying mechanism.

RESULTS

We found that compared with normotensive premenopausal women, the number and function of circulating EPCs, as well as endothelial function evaluated by flow-mediated dilatation (FMD) in prehypertensive premenopausal women were preserved. In parallel, the Tie2/Akt/eNOS signaling pathway and the plasma NO level or NO secretion of circulating EPCs in prehypertensive premenopausal women was also retained. However, in presence of normotension or prehypertension with diabetes mellitus, the number or function of circulating EPCs and FMD in premenopausal women decreased. Similarly, the phosphorylation of Tie2/Akt/eNOS signaling pathway and the plasma NO level or NO secretion of circulating EPCs was reduced in prehypertension premenopausal with diabetes mellitus.

CONCLUSION

The present findings firstly demonstrate that the unfavorable effects of diabetes mellitus on number and activity of circulating EPCs in prehypertension premenopausal women, which is at least partially related to the abnormal phosphorylation of Tie2/Akt/eNOS signaling pathway and subsequently reduced nitric oxide bioavailability. The Tie2/Akt/eNOS signaling pathway may be a potential target of vascular protection in prehypertensive premenopausal women with diabetes mellitus.

Significance and therapeutic implications of endothelial progenitor cells in angiogenic-mediated tumour metastasis

Cancer conveys profound social and economic consequences throughout the world. Metastasis is responsible for approximately 90% of cancer-associated mortality and, when it occurs, cancer becomes almost incurable. During metastatic dissemination, cancer cells pass through a series of complex steps including the establishment of tumour-associated angiogenesis. The human endothelial progenitor cells (hEPCs) are a cell population derived from the bone marrow which are required for endothelial tubulogenesis and neovascularization. They also express abundant inflammatory cytokines and paracrine angiogenic factors. Clinically hEPCs are highly correlated with relapse, disease progression, metastasis and treatment response in malignancies such as breast cancer, ovarian cancer and non-small-cell lung carcinoma. It has become evident that the hEPCs are involved in the angiogenesis-required progression and metastasis of tumours. However, it is not clear in what way the signalling pathways, controlling the normal cellular function of human BM-derived EPCs, are hijacked by aggressive tumour cells to facilitate tumour metastasis. In addition, the actual roles of hEPCs in tumour angiogenesis-mediated metastasis are not well characterised. In this paper we reviewed the clinical relevance of the hEPCs with cancer diagnosis, progression and prognosis. We further summarised the effects of tumour microenvironment on the hEPCs and underlying mechanisms. We also hypothesized the roles of altered hEPCs in tumour angiogenesis and metastasis. We hope this review may enhance our understanding of the interaction between hEPCs and tumour cells thus aiding the development of cellular-targeted anti-tumour therapies.