Circulating endothelial (progenitor) cells reflect the state of the endothelium: vascular injury, repair and neovascularization

Beyond brain injury biomarkers: chemoattractants and circulating progenitor cells as biomarkers of endogenous rehabilitation effort in preterm neonates with encephalopathy

Introduction

Preclinical work and studies in adults have shown that endogenous regeneration efforts that involve mobilization of progenitor cells take place after brain injury. However, kinetics of endogenous circulating progenitor cells (CPCs) in preterm neonates is not well described, particularly their possible role regarding brain injury and regeneration. We aimed to assess the kinetics of CPCs in neonates with encephalopathy of prematurity in relation to brain injury biomarkers, chemoattractants and relevant antenatal and postanal clinical factors, in an effort to outline the related pathophysiology.

Materials and methods

47 preterm neonates (of 28-33 weeks GA) were enrolled: 31 newborns with no or minimal brain injury (grade I IVH) and 16 prematures with encephalopathy (grade III or IV IVH, PVL or infarct). Peripheral blood samples obtained on days 1, 3, 9, 18 and 45 after birth were analyzed using flow cytometry, focusing on EPCs (early and late Endothelial Progenitor Cells), HSCs (Hematopoietic Stem Cells) and VSELs (Very Small Embryonic-Like Stem Cells). At the same time-points serum levels of S100B, Neuron-specific Enolase (NSE), Erythropoietin (EPO), Insulin-like growth factor-1 (IGF-1) and SDF-1 were also measured. Neonates were assessed postnatally with brain MRI, and with Bayley III developmental test at 2 years of corrected age.

Results

Preterms with brain injury proved to have significant increase of S100B and NSE, followed by increase of EPO and enhanced mobilization mainly of HSCs, eEPCs and lEPCs. IGF-1 was rather decreased in this group of neonates. IGF-1 and most CPCs were intense decreased in cases of antenatal or postnatal inflammation. S100B and NSE correlated with neuroimaging and language scale in Bayley III test, providing good prognostic ability.

Conclusion

The observed pattern of CPCs' mobilization and its association with neurotrophic factors following preterm brain injury indicate the existence of an endogenous brain regeneration process. Kinetics of different biomarkers and associations with clinical factors contribute to the understanding of the related pathophysiology and might help to early discriminate neonates with adverse outcome. Timely appropriate enhancement of the endogenous regeneration effort, when it is suppressed and insufficient, using neurotrophic factors and exogenous progenitor cells might be a powerful therapeutic strategy in the future to restore brain damage and improve the neurodevelopmental outcome in premature infants with brain injury.

Emerging Roles of Extracellular Vesicle-Delivered Circular RNAs in Atherosclerosis

Atherosclerosis (AS) is universally defined as chronic vascular inflammation induced by dyslipidaemia, obesity, hypertension, diabetes and other risk factors. Extracellular vesicles as information transmitters regulate intracellular interactions and their important cargo circular RNAs are involved in the pathological process of AS. In this review, we summarize the current data to elucidate the emerging roles of extracellular vesicle-derived circular RNAs (EV-circRNAs) in AS and the mechanism by which EV-circRNAs affect the development of AS. Additionally, we discuss their vital role in the progression from risk factors to AS and highlight their great potential for use as diagnostic biomarkers of and novel therapeutic strategies for AS.

Effects and Mechanisms of Taohong Siwu Decoction on the Prevention and Treatment of Myocardial Injury

Taohong Siwu decoction (THSWD) is one of the classic prescriptions for promoting blood circulation and removing blood stasis. With the continuous in-depth excavation in basic and clinical research, it has been found that THSWD has made greater progress in the prevention and treatment of cardiovascular diseases. Mechanisms of the current studies have shown that it could prevent and treat the myocardial injury by inhibiting inflammatory reaction, antioxidant stress, inhibiting platelet aggregation, prolonging clotting time, anti-fibrosis, reducing blood lipids, anti-atherosclerosis, improving hemorheology and vascular pathological changes, regulating related signal pathways and other mechanisms to prevent and treat the myocardial injury, so as to protect cardiomyocytes and improve cardiac function. Many clinical studies have shown that THSWD is effective in the prevention and treatment of cardiovascular diseases related to myocardial injuries, such as coronary heart disease angina pectoris (CHD-AP), and myocardial infarction. In clinical practice, it is often used by adding and subtracting prescriptions, the combination of compound prescriptions and combinations of chemicals and so on. However, there are some limitations and uncertainties in both basic and clinical research of prescriptions. According to the current research, although the molecular biological mechanism of various active ingredients needs to be further clarified, and the composition and dose of the drug have not been standardized and quantified, this study still has exploration for scientific research and clinical practice. Therefore, this review mainly discusses the basic mechanisms and clinical applications of THSWD in the prevention and treatment of the myocardial injury caused by CHD-AP and myocardial infarction. The authors hope to provide valuable ideas and references for researchers and clinicians.

Aliskiren Improved the Endothelial Repair Capacity of Endothelial Progenitor Cells from Patients with Hypertension via the Tie2/PI3k/Akt/eNOS Signalling Pathway

Background

Studies show that aliskiren exerts favourable effects not only on endothelial progenitor cells (EPCs) but also on endothelial function. However, the mechanism of the favourable effect of aliskiren on EPCs from patients with hypertension is unclear and remains to be further studied.

Methods

The object of this study was to investigate and assess the in vitro function of EPCs pretreated with aliskiren. After treated with aliskiren, the human EPCs were transplanted into a nude mouse model of carotid artery injury, and the in vivo reendothelialization of injured artery was estimated by staining denuded areas with Evans blue dye via tail vein injection.

Results

We found that aliskiren increased the in vitro migration, proliferation, and adhesion of EPCs from patients with hypertension in a dose-dependent manner and improved the reendothelialization capability of these EPCs. Furthermore, aliskiren increased the phosphorylation of Tie2, Akt, and eNOS. After the blockade of the Tie2 signalling pathway, the favourable effects of aliskiren on the in vitro function and in vivo reendothelialization capability of EPCs were suppressed.

Conclusions

This study demonstrates that aliskiren can improve the in vitro function and in vivo reendothelialization capability of EPCs from patients with hypertension via the activation of the Tie2/PI3k/Akt/eNOS signalling pathway. These findings further indicate that aliskiren is an effective pharmacological treatment for cell-based repair in hypertension-related vascular injury.

Prognostic value of circulating endothelial cells in metastatic colorectal cancer

BACKGROUND

There is urgent need for improved staging in patients with metastatic colorectal cancer (mCRC). In this study, we evaluated the prognostic value of circulating endothelial cells (CEC) in comparison with circulating tumor cells (CTC) in patients with mCRC amenable for potentially curative surgery.

METHODS

A total of 140 patients were enrolled prospectively. CTC and CEC were measured with the CellSearch System (Veridex, NJ, USA). Cut-off values were determined using ROC analyses. Prognostic factors were identified by Cox proportional hazards models.

RESULTS

ROC analyses revealed ≥ 21 CEC as cut-off levels for detection, which was present in 68 (49%). CEC detection was associated with female gender (p = 0.03) only, whereas CTC detection was associated with presence of the primary tumor (p = 0.007), metastasis size (p < 0.001), bilobar liver metastases (p = 0.02), CEA (p < 0.001) and CA 19-9 levels (p < 0.001). On multivariate analysis only CEC detection (HR 1.81; p = 0.03) and preoperative CA19-9 levels (HR 2.28, p = 0.005) were revealed as independent predictors of poor survival.

CONCLUSIONS

CEC are of stronger prognostic value than CTC. Further studies are required to validate these results and to evaluate CEC as predictive biomarker for systemic therapy alone as well as in combination with other markers such as CA19-9.

Increased Endothelial Progenitor Cell Number in Early Stage of Endometrial Cancer

OBJECTIVES

It is generally believed that circulating endothelial cells (CECs) and endothelial progenitor cells (EPCs) reflect the state of the endothelium, its injury and/or repair possibilities. In different types of cancers, increased numbers of CECs and EPCs were found, suggesting their participation in cancer angiogenesis. The objective of this study was to determine whether, in the blood circulation of women with early endometrial cancer, CEC and EPC levels differ from those of healthy women of similar age.

METHODS

For CEC number evaluation, samples of peripheral blood cells of women with endometrial carcinoma and control subjects were labeled with anti-CD31 and anti-CD45 antibodies; for EPCs, with anti-VEGFR2 (vascular-endothelium growth factor receptor 2)/KDR and anti-CD34 antibodies. The CEC and EPC cells were then quantified by flow cytometry.

RESULTS

Endothelial progenitor cell numbers (CD34, VEGFR2/KDR) in the peripheral blood of women with endometrial carcinoma were significantly augmented as compared with those of control healthy women and CEC numbers (CD31, CD45) were similar in both groups. Cancer patients were divided according to the grading into G1 and G2 groups and according to the stage into International Federation of Gynecology and Obstetrics (FIGO) stage IA and FIGO IB groups. Statistically significant augmented EPC numbers were demonstrated only in G1 and FIGO IA patients.

CONCLUSIONS

These results strongly suggest new vessel formation from recruited endothelial precursors as being involved mainly at the early stages of tumor progression.

Circulating endothelial cells, circulating endothelial progenitor cells, and von Willebrand factor in pregnancies complicated by hypertensive disorders

PROBLEM

We tested the hypothesis that the number of both CECs and CEPCs as well as the vWf blood plasma concentration are altered in pregnant women with hypertensive disorders.

METHOD OF STUDY

Seventy-five pregnant women were enrolled in our study. We used multicolor flow cytometry for CEC and CEPC analysis and the commercial human VWF ELISA kit to measure vWf blood plasma concentration.

RESULTS

The highest number of CECs was found in the chronic hypertension group and the lowest number in the healthy pregnant control group. The highest number of CEPCs was found in the control group and the lowest number in the chronic hypertension group. The vWf blood plasma concentration was the highest in the pre-eclampsia group. The CEPC/CEC ratio reached its lowest value in the chronic hypertension group and its highest value in the control group.

CONCLUSION

The number of both CECs and CEPCs as well as the vWf blood plasma concentration depends on the type of hypertension complicating the pregnancy.

Mechanotransduction Effects on Endothelial Cell Proliferation via CD31 and VEGFR2: Implications for Immunomagnetic Separation

Immunomagnetic separation is used to isolate circulating endothelial cells (ECs) and endothelial progenitor cells (EPCs) for diagnostics and tissue engineering. However, potentially detrimental changes in cell properties have been observed post-separation. Here, the effect of mechanical force, which is naturally applied during immunomagnetic separation, on proliferation of human umbilical vein endothelial cells (HUVEC), kinase insert domain-positive receptor (KDR) cells, and peripheral blood mononuclear cells (PBMCs). Cells are exposed to CD31 or Vascular Endothelial Growth Factor Receptor-2 (VEGFR2) targeted MACSi beads at varying bead to cell ratios and compared to free antibody and unconjugated beads. A vertical magnetic gradient is applied to static 2D cultures, and a magnetic cell sorter is used to analyze cells in dynamic flow. No significant difference in EC proliferation is observed for controls or VEGFR2-targeting beads, whereas CD31-conjugated beads increase proliferation in a dose dependent manner in static 2-D cultures. This effect occurs in the absence of magnetic field, but is more pronounced with magnetic force. After flow sorting, similar increases in proliferation are seen for CD31 targeting beads. Thus, the effects of targeting antibody and magnetic force applied should be considered when designing immunomagnetic separation protocols for ECs.

The Role of Endothelial Progenitor Cells in Ischemic Cerebral and Heart Diseases

Ischemic heart and cerebral diseases are complex clinical syndromes. Endothelial dysfunction caused by dysfunctional endothelial progenitor cells (EPCs) is thought to play a major role in pathophysiology of both types of disease. Healthy EPCs may be able to replace the dysfunctional endothelium through endogenous repair mechanisms. EPC levels are changed in patients with ischemic cerebrovascular and cardiovascular disease and EPCs may play a role in the pathophysiology of these diseases. EPCs are also a marker for preventive and therapeutic interventions. Homing of EPCs to ischemic sites is a mechanism of ischemic tissue repair, and molecules such as stromal-derived factor-1 and integrin may play a role in EPC homing in ischemic disease. Potentiation of the function and numbers of EPCs as well as combining EPCs with other pharmaceutical agents may improve the condition of ischemia patients. However, the precise role of EPCs in ischemic heart and cerebral disease and their therapeutic potential still remain to be explored. Here, we discuss the identification, mobilization, and clinical implications of EPCs in ischemic diseases.

Systemic influences contribute to prolonged microvascular rarefaction after brain irradiation: a role for endothelial progenitor cells

Whole brain radiation therapy (WBRT) induces profound cerebral microvascular rarefaction throughout the hippocampus. Despite the vascular loss and localized cerebral hypoxia, angiogenesis fails to occur, which subsequently induces long-term deficits in learning and memory. The mechanisms underlying the absence of vessel recovery after WBRT are unknown. We tested the hypotheses that vascular recovery fails to occur under control conditions as a result of loss of angiogenic drive in the circulation, chronic tissue inflammation, and/or impaired endothelial cell production/recruitment. We also tested whether systemic hypoxia, which is known to promote vascular recovery, reverses these chronic changes in inflammation and endothelial cell production/recruitment. Ten-week-old C57BL/6 mice were subjected to a clinical series of fractionated WBRT: 4.5-Gy fractions 2 times/wk for 4 wk. Plasma from radiated mice increased in vitro endothelial cell proliferation and adhesion compared with plasma from control mice, indicating that WBRT did not suppress the proangiogenic drive. Analysis of cytokine levels within the hippocampus revealed that IL-10 and IL-12(p40) were significantly increased 1 mo after WBRT; however, systemic hypoxia did not reduce these inflammatory markers. Enumeration of endothelial progenitor cells (EPCs) in the bone marrow and circulation indicated that WBRT reduced EPC production, which was restored with systemic hypoxia. Furthermore, using a bone marrow transplantation model, we determined that bone marrow-derived endothelial-like cells home to the hippocampus after systemic hypoxia. Thus, the loss of production and homing of EPCs have an important role in the prolonged vascular rarefaction after WBRT.

Pregnancy-induced hypertension is accompanied by decreased number of circulating endothelial cells and circulating endothelial progenitor cells

Maternal endothelial dysfunction is one of the main features of pregnancy-induced hypertension (PIH). It is generally accepted that circulating endothelial cells (CECs) and endothelial progenitor cells (EPCs) reflect the state of the endothelium, its injury and/or repair possibilities. The objective of this study was to determine whether the CECs and EPCs numbers in the circulation of women with PIH reflect the presence of this pathology. Peripheral blood cells of PIH and normotensive pregnant women were labeled with specific monoclonal antibodies. For CECs evaluation, samples were labeled with anti-CD31 and anti-CD45 antibodies; for EPCs with anti-VEGFR2/KDR and anti-CD34 antibodies. Cells were quantified by flow cytometry. The levels of both CECs (CD31⁺, CD45⁻) and EPCs (CD34⁺, VEGFR2/KDR⁺) in the peripheral blood of women with PIH were significantly lower compared with those of control pregnant women with normal blood pressure level. Lowered accessibility of maternal CECs and EPCs may diminish general regenerative potential of the patient endothelia, contributing to PIH symptoms and to the risk of subsequent coronary and arterial disease.

Blood-CNS Barrier Impairment in ALS patients versus an animal model

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease with a complicated and poorly understood pathogenesis. Recently, alterations in the blood-Central Nervous System barrier (B-CNS-B) have been recognized as a key factor possibly aggravating motor neuron damage. The majority of findings on ALS microvascular pathology have been determined in mutant superoxide dismutase (SOD1) rodent models, identifying barrier damage during disease development which might similarly occur in familial ALS patients carrying the SOD1 mutation. However, our knowledge of B-CNS-B competence in sporadic ALS (SALS) has been limited. We recently showed structural and functional impairment in postmortem gray and white matter microvessels of medulla and spinal cord tissue from SALS patients, suggesting pervasive barrier damage. Although numerous signs of barrier impairment (endothelial cell degeneration, capillary leakage, perivascular edema, downregulation of tight junction proteins, and microhemorrhages) are indicated in both mutant SOD1 animal models of ALS and SALS patients, other pathogenic barrier alterations have as yet only been identified in SALS patients. Pericyte degeneration, perivascular collagen IV expansion, and white matter capillary abnormalities in SALS patients are significant barrier related pathologies yet to be noted in ALS SOD1 animal models. In the current review, these important differences in blood-CNS barrier damage between ALS patients and animal models, which may signify altered barrier transport mechanisms, are discussed. Understanding discrepancies in barrier condition between ALS patients and animal models may be crucial for developing effective therapies.

Whole brain radiation-induced vascular cognitive impairment: mechanisms and implications

Mild cognitive impairment is a well-documented consequence of whole brain radiation therapy (WBRT) that affects 40-50% of long-term brain tumor survivors. The exact mechanisms for the decline in cognitive function after WBRT remain elusive and no treatment or preventative measures are available for use in the clinic. Here, we review recent findings indicating how changes in the neurovascular unit may contribute to the impairments in learning and memory. In addition to affecting neuronal development, WBRT induces profound capillary rarefaction within the hippocampus - a region of the brain important for learning and memory. Therapeutic strategies such as hypoxia, which restore the capillary density, result in the rescue of cognitive function. In addition to decreasing vascular density, WBRT impairs vasculogenesis and/or angiogenesis, which may also contribute to radiation-induced cognitive decline. Further studies aimed at uncovering the specific mechanisms underlying these WBRT-induced changes in the cerebrovasculature are essential for developing therapies to mitigate the deleterious effects of WBRT on cognitive function.

Vascular endothelium as a novel source of stem cells for bioengineering

Endothelial plasticity, the ability of endothelial cells to alter their lineage commitment to generate other cell types, is involved in many developmental and pathological processes. It was recently shown that vascular endothelial cells are converted to a mesenchymal stem cell phenotype through a process known as endothelial-mesenchymal transition (EndMT). EndMT is characterized as a morphological and phenotypical transformation of endothelial cells that has been implicated in cardiac development, cancer, fibrosis and heterotopic ossification. Here we describe the molecular and cellular basis for EndMT-dependent generation of endothelial-derived stem cells and their potential for tissue engineering and regenerative medicine.

CXCL12/CXCR4 signaling and other recruitment and homing pathways in fracture repair

Cell recruitment, migration and homing to the fracture site are essential for the inflammatory process, neovascularization, chondrogenesis, osteogenesis and ultimately bone remodeling. Mesenchymal stem cells (MSCs) are required to navigate from local sources such as the periosteum and local bone marrow, and may also be recruited from the circulation and distant bone marrow. While the local recruitment process may involve matrix binding and degradation, systemic recruitment may utilize extravasation, a process used by leukocytes to exit the vasculature. CXCL12 (stromal cell-derived factor-1 (SDF-1)), a member of the CXC family of chemokines, is thought to have an important role in cell migration at the fracture site. However, there are many molecules upregulated in the hematoma and callus that have chemotactic potential not only for inflammatory cells but also for endothelial cells and MSCs. Surprisingly, there is little direct data to support their role in cell homing during bone healing. Current therapeutics for bone regeneration utilize local or systemic stem cell transplantation. More recently, a novel strategy that involves mobilization of large numbers of endogenous stem and progenitor cells from bone marrow into the circulation has been shown to have positive effects on bone healing. A more complete understanding of the molecular mechanisms underlying cell recruitment and homing subsequent to fracture will facilitate the fine-tuning of such strategies for bone.

Circulating endothelial cells and tumor blood volume as predictors in lung cancer

The current criteria for evaluating antiangiogenic efficacy is insufficient as tumor shrinkage occurs after blood perfusion decreases. Tumor blood volume (BV) in computed tomography perfusion imaging and circulating endothelial cells (CEC) might predict the status of angiogenesis. The present study aimed to validate their representation as feasible predictors in non-small-cell lung carcinoma (NSCLC). A total of 74 patients was categorized randomly into two arms undergoing regimens of vinorelbine and cisplatin (Navelbine and platinum [NP]) with rh-endostatin or single NP. The response rate, perfusion imaging indexes and activated CEC (aCEC) during treatment were recorded. Progression-free survival (PFS) was determined through follow up. Correlations among the above indicators, response and PFS were analyzed: aCEC increased significantly in cases of progressive disease after single NP chemotherapy (P = 0.024). Tumor BV decreased significantly in cases with a clinical benefit in the combined arm (P = 0.026), whereas inverse correlations existed between ∆aCEC (post-therapeutic value minus the pre-therapeutic value) and PFS (P = 0.005) and between ∆BV and PFS (P = 0.044); a positive correlation existed between ∆aCEC and ∆BV. Therefore, both aCEC and tumor BV can serve as predictors, and detection of both indicators can help evaluate the chemo-antiangiogenic efficacy in NSCLC more accurately.

Complement system activation and endothelial dysfunction in patients with age-related macular degeneration (AMD): possible relationship between AMD and atherosclerosis

Age-related macular degeneration (AMD) shares several pathological and epidemiological similarities with systemic atherosclerosis (AS). First, an association between AS and AMD is apparent from the analyses of the histological and biochemical structure of atherosclerotic plaques in the vascular walls and retinal drusen, the hallmark of AMD. Second, there is considerable evidence implicating endothelial dysfunction in the pathogenesis of both disorders, and cellular oxidative stress appears to be a common denominator underlying this process. Moreover, there are observations that the complement system (CS) triggering inflammatory response contributes to the onset and advancement of both diseases. The CS plays a role in the generation of drusen and neovascularization in AMD as well as in vascular endothelium activation, cell damage and ultimately atherosclerotic plaque formation in the course of systemic arteriosclerosis. It is widely recognized that both AMD and AS are not only related to local stimulation of the CS, but also result in its systemic activation. In addition, a specific Y402H polymorphism of the complement inhibitor factor H has been found to be associated with the incidence of both AMD and AS. Here, we propose a linking hypothesis between CS activation, endothelial dysfunction and the pathogenesis of two common and age-related pathological processes, AS and AMD. We also discuss the potential therapeutic value of pharmacological modulation of CS activation in these disorders.

Circulating endothelial cells as a marker of vascular dysfunction in patients with systemic lupus erythematosus by real-time polymerase chain reaction

CONTEXT

Systemic lupus erythematosus (SLE) is associated with an increased risk of atherosclerosis; endothelial dysfunction represents the first step in its pathogenesis.

OBJECTIVE

To assess endothelial dysfunction in SLE by circulating endothelial cells (CECs) and to characterize SLE-specific factors that contribute to its appearance.

DESIGN

Case-control study was conducted on 60 subjects, divided into 2 groups: group A (30 patients with SLE) and group B (30 healthy sex- and age-matched controls). Total cholesterol, triglycerides, antinuclear antibodies, anti-double-stranded DNA antibodies, and C3 were determined in all patients. Systemic lupus erythematosus activity was assessed using the SLE Disease Activity Index. Endothelial function was assessed by means of flow-mediated dilation of the brachial artery using B-mode ultrasonography and relative quantification of CD 146 mRNA by real-time polymerase chain reaction.

RESULTS

The group of SLE patients was formed of 20 females and 10 males, with a mean age of 31.16 ± 9.69 years. The values of SLE-specific tests and SLE Disease Activity Index were represented by anti-double-stranded DNA antibodies 160 ± 40.5, C3 68.91 ± 11.91 mg/dL, total cholesterol 188.66 ± 49.63 mg/dL, triglycerides 143.41 ± 46.26 mg/dL, and SLE Disease Activity Index 12.66 ± 3.70. Values for flow-mediated dilation were 8.85% ± 2.02% (group A) and 20.33% ± 6.19% (group B), P < .001, and CECs were 300 ± 40.5 μL⁻¹ blood (group A) and 10 ± 2.5 μL⁻¹ blood (group B). The statistical analysis showed a strong inverse correlation between CECs and SLE Disease Activity Index, a strong correlation between CECs and C3, a strong correlation between CECs and anti-double-stranded DNA antibodies, and a moderate inverse correlation between CECs and total cholesterol.

CONCLUSION

Endothelial dysfunction is present in SLE patients even in the absence of traditional cardiovascular risk factors due to disease activity.

Testosterone, endothelial health, and erectile function

Experimental and clinical studies have reported that testosterone has a critical role in the maintenance of homeostatic and morphologic corpus cavernosum components, essential for normal erectile physiology. Although the exact mechanisms mediated by testosterone in erectile function are still under investigation, recent research has suggested an important role in the regulation of endothelial cell (EC) biological functions. Besides stimulating the production of EC mediators, testosterone is also thought to promote the vasculogenic reendothelialization process, mediated by bone marrow-derived endothelial progenitor cells. Additionally, testosterone seems to modulate other erectile tissue components, including trabecular smooth muscle cells, nerve fibers, and tunica albuginea structure, all essential for the erectile process. This paper summarizes current data regarding testosterone-induced cellular and molecular mechanisms that regulate penile tissue components, focusing particularly on the role of testosterone in endothelial health and erectile function.

Gammaherpesvirus 68 infection of endothelial cells requires both host autophagy genes and viral oncogenes for optimal survival and persistence

Gammaherpesvirus-associated neoplasms include tumors of lymphocytes, epithelial cells, and endothelial cells (ECs). We previously showed that, unlike most cell types, ECs survive productive gammaherpesvirus 68 (γHV68) infection and achieve anchorage-independent growth, providing a cellular reservoir for viral persistence. Here, we demonstrated autophagy in infected ECs by analysis of LC3 localization and protein modification and that infected ECs progress through the autophagosome pathway by LC3 dual fluorescence and p62 analysis. We demonstrate that pharmacologic autophagy induction results in increased survival of infected ECs and, conversely, that autophagy inhibition results in death of infected EC survivors. Furthermore, we identified two viral oncogenes, v-cyclin and v-Bcl2, that are critical to EC survival and that modify EC proliferation and survival during infection-induced autophagy. We found that these viral oncogenes can also facilitate survival of substrate detachment in the absence of viral infection. Autophagy affords cells the opportunity to recover from stressful conditions, and consistent with this, the altered phenotype of surviving infected ECs was reversible. Finally, we demonstrated that knockdown of critical autophagy genes completely abrogated EC survival. This study reveals a viral mechanism which usurps the autophagic machinery to promote viral persistence within nonadherent ECs, with the potential for recovery of infected ECs at a distant site upon disruption of virus replication.

Novel Endothelial Biomarkers: Implications for Periodontal Disease and CVD

Endothelial cells are actively involved in various aspects of vascular biology and different stages of atherosclerosis. Endothelial function is increasingly used as an important outcome measure in cardiovascular research. Endothelial progenitor cells (EPCs) are closely linked to endothelial function, and their biomarkers have received much attention. EPCs may not only serve as a pool of progenitor cells and possess the capacity to repair the damaged vasculature, but also act as potent effectors in systemic inflammation, suggesting that EPCs may play a critical role in maintaining endothelial function and the progression of cardiovascular disease (CVD). Emerging evidence shows an association of periodontal infections (gingivitis and periodontitis) with endothelial dysfunction, while the relevant mechanisms remain unknown. Our recent finding of the association of periodontitis with EPCs warrants their utilization as additional biomarkers in future studies on periodontal medicine. This review starts with a brief account on the current understanding of the nature of periodontal infections and their link with systemic inflammation and endothelial dysfunction. The paper also provides an update on endothelial biology and function as well as the novel biomarkers of EPCs and concludes with clinical studies on periodontal diseases and CVD.

Mesenchymal Stem Cells

Stem cells have two features: the ability to differentiate along different lineages and the ability of self-renewal. Two major types of stem cells have been described, namely, embryonic stem cells and adult stem cells. Embryonic stem cells (ESC) are obtained from the inner cell mass of the blastocyst and are associated with tumorigenesis, and the use of human ESCs involves ethical and legal considerations. The use of adult mesenchymal stem cells is less problematic with regard to these issues. Mesenchymal stem cells (MSCs) are stromal cells that have the ability to self-renew and also exhibit multilineage differentiation. MSCs can be isolated from a variety of tissues, such as umbilical cord, endometrial polyps, menses blood, bone marrow, adipose tissue, etc. This is because the ease of harvest and quantity obtained make these sources most practical for experimental and possible clinical applications. Recently, MSCs have been found in new sources, such as menstrual blood and endometrium. There are likely more sources of MSCs waiting to be discovered, and MSCs may be a good candidate for future experimental or clinical applications. One of the major challenges is to elucidate the mechanisms of differentiation, mobilization, and homing of MSCs, which are highly complex. The multipotent properties of MSCs make them an attractive choice for possible development of clinical applications. Future studies should explore the role of MSCs in differentiation, transplantation, and immune response in various diseases.

Cerebral microvascular rarefaction induced by whole brain radiation is reversible by systemic hypoxia in mice

Whole brain radiation therapy (WBRT) leads to cognitive impairment in 40-50% of brain tumor survivors following treatment. Although the etiology of cognitive deficits post-WBRT remains unclear, vascular rarefaction appears to be an important component of these impairments. In this study, we assessed the effects of WBRT on the cerebrovasculature and the effects of systemic hypoxia as a potential mechanism to reverse the microvascular rarefaction. Transgenic mice expressing green fluorescent protein driven by the Acta2 (smooth muscle actin) promoter for blood vessel visualization were randomly assigned to control or radiated groups. Animals received a clinical series of 4.5 Gy WBRT two times weekly for 4 wk followed by 1 mo of recovery. Subsequently, mice were subjected to 11% (hypoxia) or 21% (normoxia) oxygen for 1 mo. Capillary density in subregions of the hippocampus revealed profound vascular rarefaction that persisted despite local tissue hypoxia. Nevertheless, systemic hypoxia was capable of completely restoring cerebrovascular density. Thus hippocampal microvascular rarefaction post-WBRT is not capable of stimulating angiogenesis and can be reversed by chronic systemic hypoxia. Our results indicate a potential shift in sensitivity to angiogenic stimuli and/or the existence of an independent pathway of regulating cerebral microvasculature.

The vascular microenvironment and systemic sclerosis

The role of the vascular microenvironment in the pathogenesis Systemic Sclerosis (SSc) is appreciated clinically as Raynaud's syndrome with capillary nail bed change. This manifestation of vasculopathy is used diagnostically in both limited and diffuse cutaneous subsets of SSc, and is thought to precede fibrosis. The degree of subsequent fibrosis may also be determined by the vascular microenvironment. This paper describes why the vascular microenvironment might determine the degree of end-organ damage that occurs in SSc, with a focus on vascular cell senescence, endothelial progenitor cells (EPC) including multipotential mesenchymal stem cells (MSC), pericytes, and angiogenic monocytes. An explanation of the role of EPC, pericytes, and angiogenic monocytes is important to an understanding of SSc pathogenesis. An evolving understanding of the vascular microenvironment in SSc may allow directed treatment.

Alterations of bone marrow-derived endothelial progenitor cells following acute pulmonary embolism in mice

Pulmonary embolism (PE) is a common, lethal, ischemic disease. PE-induced endothelium injury plays a critical role in the pathophysiological consequences of PE. Endothelial progenitor cells (EPCs) can be mobilized from the bone marrow to enter circulation and play important roles in repair of damaged endothelium. However, it is not yet known if EPC mobilization results from PE. The alterations of the quantity and function of bone marrow-derived EPCs were detected in acute pulmonary embolism (APE) events in mice, and the possible role of the endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) pathway in those alterations was explored. APE models were established by injection of autologous thrombi into the right jugular vein of C57BL/6 mice. Mice were divided into sham and experimental groups including one hour (1H), one day (1D) and two day (2D) groups after injection. The results showed that in the APE 1D group, the thrombi were easily found in the large or medium pulmonary vessel. And CD133+ or CD34+ cells in bone marrow increased significantly, while CD133+/vascular endothelial growth factor receptor 2+ EPCs decreased. After seven days in culture, the abilities of incorporation into a vascular network, adhesion to fibronectin, migration and proliferation of bone marrow-derived EPCs in the APE 1D group increased significantly. The mRNA and protein expression levels of eNOS in EPCs increased in the APE 1D group. Treatment of EPCs with NG-nitro-L-arginine methyl ester inhibited functional alterations induced by APE. The results suggested that APE events stimulate the mobilization of EPCs from bone marrow, and enhance their functions. The eNOS/NO pathway may be involved in this process.

Reduction of circulating endothelial cells in peripheral blood of ALS patients

Background

Amyotrophic Lateral Sclerosis (ALS) treatment is complicated by the various mechanisms underlying motor neuron degeneration. Recent studies showed that the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) are compromised in an animal model of ALS due to endothelial cell degeneration. A later study demonstrated a loss of endothelium integrity in the spinal cords of ALS patients. Since circulating endothelial cells (CECs) in the peripheral blood are associated with endothelium damage, being detached dysfunctional endothelial cells, we hypothesized that CEC levels may reflect endothelium condition in ALS patients.

Methodology/Principal Findings

CEC levels were estimated in whole blood smears from ALS patients with moderate stage (_MALS), severe stage (_SALS), and healthy controls by CD146 expression using immunocytochemistry. A significant reduction of CECs was detected in _MALS and _SALS patients.

Conclusions/Significance

CECs did not predict endothelium state in ALS patients; however, endothelial damage and/or impaired endothelium repair may occur in ALS leading to BBB/BSCB dysfunction. Reduced CECs in peripheral blood of ALS patients may indicate different mechanisms of endothelial damage and repair, rather than only detachment of dysfunctional endothelial cells. Although a potential mechanism of CEC reduction is discussed, establishing a reliable indicator of endothelial dysfunction/damage is important for evaluation of BBB/BSCB status in ALS patients during disease progression.

Transfection of HGF gene enhances endothelial progenitor cell (EPC) function and improves EPC transplant efficiency for balloon-induced arterial injury in hypercholesterolemic rats

Risk factors for coronary heart disease can reduce the number of endothelial progenitor cells (EPCs) and impair EPC function, thus hindering their utility in the treatment of cardiovascular diseases. In the present study, we began exploring the feasibility of genetic modification of EPCs with hepatocyte growth factor (HGF) to counter the effects of these risk factors and enhance the biological functions of EPCs. The effects of HGF transfection on proliferation, migration and angiogenesis of EPCs were investigated. Additionally, the role of ERK1/2 in this process was evaluated through the observation of ERK1/2 and ERK1/2 phosphorylation as well as by pharmacological analysis. Finally, we evaluated the effect of HGF-transfected EPCs (HGF-EPCs) on neointima formation after balloon-induced arterial injury in hypercholesterolemic rats. Our data showed that EPCs transfected with the HGF gene released high levels of soluble HGF protein, which were maintained for at least nine days. Transfection with HGF also enhanced the proliferative, migratory and angiogenic capabilities of EPCs, and promoted the activation of ERK1/2 without affecting its expression. ERK1/2 blockade by the chemical inhibitor PD98059 partially inhibited these effects. In hypercholesterolemic rats, HGF-EPCs homed to the site of vascular injury at a significantly higher rate than did EPCs without the exogenous HGF gene. Furthermore, systemically applied HGF-EPCs were more effective in decreasing neointima formation and increasing re-endothelialization. These data suggest that gene delivery combined with EPC transplant may be a practical and promising therapy for the prevention of neointimal formation after vascular injury.

Endothelial progenitor cell therapy in atherosclerosis: a double-edged sword?

Atherosclerosis, an inflammatory process that selectively affects arteries, is highly prevalent in human. Thrombo-occlusive complications of atherosclerosis, including stroke and myocardial infarction, are becoming major causes of morbidity and mortality in the industrialized world. Atherosclerosis develops in response to local endothelial injuries. Endothelial dysfunction and cell loss are prominent features in atherosclerosis. Restoring the endothelial lining to normal is critical for slowing or reversing the progression of atherosclerosis. Increasing data suggest that endothelial progenitor cells (EPCs) play a significant role in reendothelialization of the injured blood vessels. This review focuses on the effects of EPC mobilization and transfusion in the condition of atherosclerosis. The aim of the review is to provide an update on the progress in this research field, highlight the role of EPCs in atherosclerosis and discuss the possible mechanisms and potential risks of progenitor cell-based therapy in atherosclerosis.

Macrophage phenotype as a determinant of biologic scaffold remodeling

Macrophage phenotype can be characterized as proinflammatory (M1) or immunomodulatory and tissue remodeling (M2). The present study used a rat model to determine the macrophage phenotype at the site of implantation of two biologic scaffolds that were derived from porcine small intestinal submucosa (SIS) and that differed mainly according to their method of processing: the Restore device (SIS) and the CuffPatch device (carbodiimide crosslinked form of porcine-derived SIS (CDI-SIS)). An autologous tissue graft was used as a control implant. Immunohistologic methods were used to identify macrophage surface markers CD68 (pan macrophages), CD80 and CCR7 (M1 profile), and CD163 (M2 profile) during the remodeling process. All graft sites were characterized by the dense population of CD68+ mononuclear cells present during the first 4 weeks. The SIS device elicited a predominantly CD163+ response (M2 profile, p < 0.001) and showed constructive remodeling at 16 weeks. The CDI-SIS device showed a predominately CD80+ and CCR7+ response (M1 profile, p < 0.03), and at 16 weeks was characterized by chronic inflammation. The autologous tissue graft showed a predominately CD163+ response (M2) at 1 week, with a dual M1/M2 population (CD80+, CCR7+, and CD163+) by 2 and 4 weeks and moderately well organized connective tissue by 16 weeks. The processing methods used during the manufacturing of a biologic scaffold can have a profound influence upon the macrophage phenotype profile and downstream remodeling events. Routine histologic examination alone is inadequate to determine the phenotype of mononuclear cells that participate in the host response to the scaffold.

Genomic changes in regenerated porcine coronary arterial endothelial cells

OBJECTIVE

Genomic changes were defined in cultures of regenerated porcine coronary endothelial cells to explain the alterations that underlie their dysfunction.

METHODS AND RESULTS

Regeneration of the endothelium was triggered in vivo by endothelial balloon denudation. After 28 days, both left circumflex (native cells) and left anterior descending (regenerated cells) coronary arteries were dissected, their endothelial cells harvested, and primary cultures established. The basal cyclic GMP production was reduced in regenerated cells without significant reduction in the response to bradykinin and A23187. The mRNA expression levels in both native and regenerated cells were measured by microarray and RT-PCR. The comparison revealed genomic changes related to vasomotor control (cyclooxygenase-1, angiotensin II receptor), coagulation (F2 and TFPI), oxidative stress (Mn SOD, GPX3, and GSR), lipid metabolism (PLA2 and HPGD), and extracellular matrix (MMPs). A-FABP and MMP7 were induced by regeneration. RT-PCR revealed upregulation of A-FABP and downregulation of eNOS and TR. The differential gene expression profiles were confirmed at the protein level by Western blotting for eNOS, F2, Mn SOD, MMP7, and TR.

CONCLUSIONS

Cultures from regenerated coronary endothelial cells exhibit genomic changes explaining endothelial dysfunction and suggesting facilitation of coagulation, lipid peroxidation, and extracellular matrix remodeling.

Modelling the role of angiogenesis and vasculogenesis in solid tumour growth

Recent experimental evidence suggests that vasculogenesis may play an important role in tumour vascularisation. While angiogenesis involves the proliferation and migration of endothelial cells (ECs) in pre-existing vessels, vasculogenesis involves the mobilisation of bone-marrow-derived endothelial progenitor cells (EPCs) into the bloodstream. Once blood-borne, EPCs home in on the tumour site, where subsequently they may differentiate into ECs and form vascular structures. In this paper, we develop a mathematical model, formulated as a system of nonlinear ordinary differential equations (ODEs), which describes vascular tumour growth with both angiogenesis and vasculogenesis contributing to vessel formation. Submodels describing exclusively angiogenic and exclusively vasculogenic tumours are shown to exhibit similar growth dynamics. In each case, there are three possible scenarios: the tumour remains in an avascular steady state, the tumour evolves to a vascular equilibrium, or unbounded vascular growth occurs. Analysis of the full model reveals that these three behaviours persist when angiogenesis and vasculogenesis act simultaneously. However, when both vascularisation mechanisms are active, the tumour growth rate may increase, causing the tumour to evolve to a larger equilibrium size or to expand uncontrollably. Alternatively, the growth rate may be left unaffected, which occurs if either vascularisation process alone is able to keep pace with the demands of the growing tumour. To clarify further the effects of vasculogenesis, the full model is also used to compare possible treatment strategies, including chemotherapy and antiangiogenic therapies aimed at suppressing vascularisation. This investigation highlights how, dependent on model parameter values, targeting both ECs and EPCs may be necessary in order to effectively reduce tumour vasculature and inhibit tumour growth.

Stem Cell Therapy: A Hope for Dying Hearts

The restoration of functional myocardium following heart failure still remains a formidable challenge among researchers. Irreversible damage caused by myocardial infarction is followed by left ventricular remodeling. The current pharmacologic and interventional strategies fail to regenerate dead myocardium and are usually insufficient to meet the challenge caused by necrotic cardiac myocytes. There is growing evidence, suggesting that the heart has the ability to regenerate through the activation of resident cardiac stem cells or through the recruitment of a stem cell population from other tissues such as bone marrow. These new findings belie the earlier conception about the poor regenerating ability of myocardial tissue. Stem cell therapy is a promising new approach for myocardial repair. However, it has been limited by the paucity of cell sources for functional human cardiomyocytes. Moreover, cells isolated from different sources exhibit idiosyncratic characteristics including modes of isolation, ease of expansion in culture, proliferative ability, characteristic markers, etc., which are the basis for several technical manipulations to achieve successful engraftment. Clinical trials show some evidence for the successful integration of stem cells of extracardiac origin in adult human heart with an improved functional outcome. This may be attributed to the discrepancies in the methods of detection, study subject selection (early or late post transplantation), presence of inflammation, and false identification of infiltrating leukocytes. This review discusses these issues in a comprehensive manner so that their physiological significance in animal as well as in human studies can be better understood.

Endothelial progenitor cells: a promising therapeutic alternative for cardiovascular disease

The integrity and functional activity of the endothelial monolayer play a critical role in preventing atherosclerotic disease progression. Endothelial cell (EC) damage by atherosclerosis risk factors can result in EC apoptosis with loss of the integrity of the endothelium. Thus, approaches to repair the injured vessels with the goal of regenerating ECs have been tested in preclinical experimental models and in clinical studies. Indeed, endothelial progenitor cells (EPCs) originating from the bone marrow have been shown to incorporate into sites of neovascularization and home to sites of endothelial denudation. These cells may provide an endogenous repair mechanism to counteract ongoing risk factor-induced endothelial injury and to replace dysfunctional endothelium. Risk factors for coronary artery disease, such as age, smoking, hypertension, hyperlipidemia, and diabetes, however, reduce the number and functional activity of circulating EPCs, potentially restricting the therapeutic prospective of progenitor cells and limiting the regenerative capacity. Furthermore, the impairment of EPCs by risk factors may contribute to atherogenesis and atherosclerotic disease progression. The article reviews the role of EPCs in atherogenesis and in predicting cardiovascular outcomes, and highlights the potential challenges in developing therapeutic strategies aiming to interfere with the balance of injury and repair mechanisms.

Identification of functional endothelial progenitor cells suitable for the treatment of ischemic tissue using human umbilical cord blood

Umbilical cord blood (UCB) has been used as a potential source of various kinds of stem cells, including hematopoietic stem cells, mesenchymal stem cells, and endothelial progenitor cells (EPCs), for a variety of cell therapies. Recently, EPCs were introduced for restoring vascularization in ischemic tissues. An appropriate procedure for isolating EPCs from UCB is a key issue for improving therapeutic efficacy and eliminating the unexpected expansion of nonessential cells. Here we report a novel method for isolating EPCs from UCB by a combination of negative immunoselection and cell culture techniques. In addition, we divided EPCs into 2 subpopulations according to the aldehyde dehydrogenase (ALDH) activity. We found that EPCs with low ALDH activity (Alde-Low) possess a greater ability to proliferate and migrate compared to those with high ALDH activity (Alde-High). Moreover, hypoxia-inducible factor proteins are up-regulated and VEGF, CXCR4, and GLUT-1 mRNAs are increased in Alde-Low EPCs under hypoxic conditions, while the response was not significant in Alde-High EPCs. In fact, the introduction of Alde-Low EPCs significantly reduced tissue damage in ischemia in a mouse flap model. Thus, the introduction of Alde-Low EPCs may be a potential strategy for inducing rapid neovascularization and subsequent regeneration of ischemic tissues.

Nitroglycerin attenuates human endothelial progenitor cell differentiation, function, and survival

Endothelial progenitor cells (EPCs) participate in angiogenesis and the response to chronic ischemia. Risk factors and cardiovascular disease attenuate EPC number, function, and survival. Continuous therapy with nitroglycerin (glyceryl trinitrate; GTN) is associated with increased vascular oxidative stress, leading to nitrate tolerance and endothelial dysfunction. Thus, GTN therapy may also affect EPCs. The purpose of this study was to determine whether continuous exposure to GTN in vivo or during ex vivo expansion affects the circulating number and functional characteristics of human EPCs. To determine the effects of continuous in vivo GTN exposure, EPCs isolated from 28 healthy males before and after receiving 0.6 mg/h GTN (n=17) or no treatment (n=11) for 1 week were expanded for 6 days and compared. To determine the effects of continuous ex vivo GTN exposure, EPCs isolated before randomization were expanded for 6 days in medium supplemented with 100 nM, 300 nM, or 1 microM GTN. EPCs expanded without GTN served as controls (n=10). In vivo, GTN exposure significantly increased the percentage of circulating cells expressing the EPC marker CD34 and increased the susceptibility of expanded EPCs to apoptosis but had no impact on the phenotypic differentiation or migration of EPCs. Ex vivo, GTN exposure increased apoptosis while decreasing phenotypic differentiation, migration, and mitochondrial dehydrogenase activity of EPCs, compared with EPCs expanded in the absence of GTN. Taken together, these results suggest that continuous GTN therapy might impair EPC-mediated processes, an effect that could be detrimental in the setting of ischemic cardiovascular disease.

The bone marrow-derived endothelial progenitor cell response is impaired in delayed wound healing from ischemia

OBJECTIVE

Vasculogenesis relies on the recruitment of bone marrow-derived endothelial progenitor cells (BMD EPCs) and is stimulated by tissue-level ischemia. We hypothesized that the BMD EPC response is impaired in ischemic wounds and studied the relationship between BMD EPCs and wound healing.

METHODS

We used transgenic Tie-2/LacZ mice, which carry the beta-galactosidase (beta-gal) reporter gene under Tie-2 promoter control. Wild-type mice were lethally irradiated and reconstituted with Tie-2/LacZ bone marrow. Four weeks later, the mice underwent unilateral femoral artery ligation/excision and bilateral wounding of the hindlimbs. Ischemia was confirmed and monitored with laser Doppler imaging. A subset of mice received incisional vs excisional nonischemic bilateral hindlimb wounds, without femoral ligation. Excisional wound closure was measured by using daily digital imaging and software-assisted calculation of surface area.

RESULTS

Ischemia resulted in significantly delayed wound healing and differentially affected the number of BMD EPCs recruited to wound granulation tissue and muscle underlying the wounds. At 3 days postwounding, the granulation tissue of the wound base contained significantly fewer numbers of BMD EPCs in ischemic wounds compared with the nonischemic wounds (P < .05). In contrast, significantly more BMD EPCs were present in the muscle underlying the ischemic wounds at this same time point compared with the muscle under the nonischemic wounds (P < .05). In ischemic wounds, eventual wound closure significantly correlated with a delayed rise in BMD EPCs within the wound granulation tissue (Kendall's correlation, -.811, P = .0005) and was significantly associated with a gradual recovery of hindlimb perfusion (P < .0001). By 7 days postwounding, BMD EPCs were incorporated into the neovessels in the granulation tissue. At 14 days and 75 days, BMD EPCs were rarely observed within the wounds.

CONCLUSIONS

Granulation tissue of excisional ischemic wounds showed significantly less BMD EPCs 3 days postwounding, in association with significantly delayed wound closure. However, the number of BMD EPCs were increased in ischemic hindlimb skeletal muscle, consistent with the notion that ischemia is a powerful signal for vasculogenesis. To our knowledge, this is the first report identifying a deficit in BMD EPCs in the granulation tissue of ischemic skin wounds and reporting the key role for these cells in both ischemic and nonischemic wound healing.