Age-dependent impairment of reendothelialization after arterial injury: role of vascular endothelial growth factor

Microsurgical clipping versus endovascular therapy for treating patients with middle cerebral artery aneurysms presenting with neurological ischemic symptoms

Studies comparing different treatment methods in patients with middle cerebral artery (MCA) aneurysms in different subgroups of onset symptoms are lacking. It is necessary to explore the safety and efficacy of open surgical treatment and endovascular therapy in patients with MCA aneurysms in a specific population. This study aimed to compare microsurgical clipping versus endovascular therapy regarding complication rates and outcomes in patients with MCA aneurysms presenting with neurological ischemic symptoms. This was a retrospective cohort study in which 9656 patients with intracranial aneurysms were screened between January 2014 and July 2022. Further, 130 eligible patients were enrolled. The primary outcome was the incidence of serious adverse events (SAEs) within 30 days of treatment, whereas secondary outcomes included postprocedural target vessel-related stroke, disabling stroke or death, mortality, and aneurysm occlusion rate. Among the 130 included patients, 45 were treated with endovascular therapy and 85 with microsurgical clipping. The primary outcome of the incidence of SAEs within 30 days of treatment was significantly higher in the clipping group [clipping: 23.5%(20/85) vs endovascular: 8.9%(4/45), adjusted OR:4.05, 95% CI:1.20-13.70; P = 0.024]. The incidence of any neurological complications related to the treatment was significantly higher in the clipping group [clipping:32.9%(28/85) vs endovascular:15.6%(7/45); adjusted OR:3.49, 95%CI:1.18-10.26; P = 0.023]. Postprocedural target vessel-related stroke, disabling stroke or death, mortality rate, and complete occlusion rate did not differ significantly between the two groups. Endovascular therapy seemed to be safer in treating patients with MCA aneurysms presenting with neurological ischemic symptoms compared with microsurgical clipping, with a significantly lower incidence of SAEs within 30 days of treatment and any neurological complications related to the treatment during follow-up.

Treatment Outcomes of 94 Cases of Pipeline Embolization Device in a Single Center: Predictive Factors of Incomplete Aneurysm Occlusion

Objective

This study aimed to report the outcome of an endovascular treatment with a pipeline embolization device (PED) at a single center. We also examined the predictive factors for an incomplete occlusion after the PED placement.

Methods

The subjects were 94 patients with 109 aneurysms who underwent the PED placement at our single center from June 2015 to September 2022. As treatment outcomes, we investigated the PED placement success rate, perioperative morbidity and mortality, postoperative cranial nerve improvement rate, and the classification of angiographic result at 6 months after the PED placement. Furthermore, the predictors of an incomplete occlusion were investigated in detail.

Results

One hundred nine aneurysms locations were: C1 (9), C2 (30), C3 (15), C4 (53), and C5 (2) in the internal carotid artery segments. Perioperative morbidity, including the asymptomatic ones, occurred in 10 cases (10.6%). Among these 10 cases, the modified Rankin Scale (mRS) improved to preoperative mRS after 90 days in 9 cases except 1 case. On the other hand, no perioperative mortality was observed. The postoperative cranial nerve improvement rate was 84.4%, and 61.7% of patients had a complete occlusion in the follow-up angiography, 6 months after the PED placement. Predictive factors for an incomplete occlusion after the PED placement were the elderly aged 70 years or older (P-value = 0.0214), the elderly aged 75 years or older (P-value = 0.0009), and the use of anticoagulants (P-value = 0.0388) in an univariate analysis. Further, the multivariate analysis revealed that the elderly aged 75 years or older was a predictive factor of an incomplete occlusion in this study.

Conclusion

We summarized the outcomes of the PED treatment at our single center. In this study, the elderly aged 75 years or older was a predictive factor of an incomplete occlusion after the PED placement.

Testosterone replacement relieves ligature-induced periodontitis by mitigating inflammation, increasing pro-resolving markers and promoting angiogenesis in rats: A preclinical study

OBJECTIVES

This study aimed to evaluate the inflammatory profile as well as the resolution of inflammation in a ligature-induced periodontal inflammation in rats with depletion and/or supraphysiological testosterone replacement.

DESIGN

Sixty male rats (Holtzman) were used in the present study. Study groups were created as following: (1) Sham (no testicle removal); (2) Orchiectomy (OCX), 3) OCX + Testosterone (OCX + T); (4) Sham + Ligature (SH + L); (5) OCX+L; and 6) OCX + T + L. The surgeries were performed on day 1, and testosterone was administered weekly since day 1. On day 15, a cotton ligature was placed around the lower first molars and maintained for 15 days. Morphological changes in periodontal tissues were determined by histopathological analysis. Immunohistochemistry (factor VIII) and immunoenzymatic assay were performed to evaluate angiogenesis process and (pro- and anti-) inflammatory markers, respectively.

RESULTS

Ligature promoted a marked inflammatory gingival infiltrate and bone loss (P < 0.05). Supraphysiological testosterone treatment increased the percentage of blood vessels, extracellular matrix and fibroblasts in the presence and absence of periodontal inflammation (P < 0.05). A high dose of testosterone increased factor VIII+ blood vessels and IL-10 expression in inflamed gingival tissue, while PGE₂, LXA₄ and MPO were reduced as a result of supraphysiological testosterone administration (P < 0.05).

CONCLUSIONS

These results, in our experimental model, suggest that supraphysiological testosterone treatment stimulated gingival tissue repair during ligature-induced periodontitis, and it seems to be related to an anti-inflammatory and pro-resolutive mechanism resulting by the modulatory effect on PGE₂ and IL-10 related to an enhanced angiogenesis.

Tie2-Cre-Induced Inactivation of Non-Nuclear Estrogen Receptor-α Signaling Abrogates Estrogen Protection Against Vascular Injury

Using the Cre-loxP system, we generated the first mouse model in which estrogen receptor-α non-nuclear signaling was inactivated in endothelial cells. Estrogen protection against mechanical vascular injury was impaired in this model. This result indicates the pivotal role of endothelial estrogen receptor-α non-nuclear signaling in the vasculoprotective effects of estrogen.

Estrogen Receptor and Vascular Aging

Cardiovascular diseases remain an age-related pathology in both men and women. These pathologies are 3-fold more frequent in men than in women before menopause, although this difference progressively decreases after menopause. The vasculoprotective role of estrogens are well established before menopause, but the consequences of their abrupt decline on the cardiovascular risk at menopause remain debated. In this review, we will attempt to summarize the main clinical and experimental studies reporting the protective effects of estrogens against cardiovascular diseases, with a particular focus on atherosclerosis, and the impact of aging and estrogen deprivation on their endothelial actions. The arterial actions of estrogens, but also part of that of androgens through their aromatization into estrogens, are mediated by the estrogen receptor (ER)α and ERβ. ERs belong to the nuclear receptor family and act by transcriptional regulation in the nucleus, but also exert non-genomic/extranuclear actions. Beside the decline of estrogens at menopause, abnormalities in the expression and/or function of ERs in the tissues, and particularly in arteries, could contribute to the failure of classic estrogens to protect arteries during aging. Finally, we will discuss how recent insights in the mechanisms of action of ERα could contribute to optimize the hormonal treatment of the menopause.

Flow Diversion vs. Stent-Assisted Coiling in the Treatment of Intradural Large Vertebrobasilar Artery Aneurysms

Objective

To compare the safety, angiographic, and long-term clinical outcomes of intradural large vertebrobasilar artery (VBA) aneurysms following flow diversion (FD) or conventional stent-assisted coiling (SAC).

Methods

We performed a retrospective study of 66 consecutive patients with intradural large VBA aneurysms between 2014 and 2021 who underwent FD or SAC. Patients' characteristics, postprocedural complications, and clinical and angiographic outcome details were reviewed.

Results

A total of 66 intradural large VBA aneurysms were included, including 42 (63.6%), which were treated with SAC (SAC group) and 24 (36.4%), which were treated with FD (FD group). Clinical follow-up was obtained at the median of 24.0 [interquartile range (IQR) 12.0–45.0] months, with 34 (81.0%) patients achieved the modified Rankin Scale (mRS) ≤ 2 in the SAC group and 21 (87.5%) patients in the FD group. Thirteen (19.7%) patients experienced neurological complications, of which 9 (13.6%) patients first occurred during the periprocedural phase and 4 (6.1%) patients first occurred during follow-up. The overall complication rate and periprocedural complication rate were both higher in the SAC group, but did not reach statistical significance (23.8 vs. 12.5%, P = 0.430; 16.7 vs. 8.3%, P = 0.564). The mortality rates were similar between the groups (11.9 vs. 12.5%). Angiographic follow-up was available for 46 patients at the median of 7 (IQR 6–14) months, with a numerically higher complete occlusion rate in the SAC group (82.1 vs. 55.6%, P = 0.051) and similar adequate aneurysm occlusion rates between the groups (85.7 vs. 83.3%, P = 1.000). In the multivariate analysis, ischemic onset (P = 0.019), unilateral vertebral artery sacrifice (P = 0.008), and older age (≥60 years) (P = 0.031) were significantly associated with complications.

Conclusion

There was a trend toward lower complication rate and lower complete occlusion rate for intradural large VBA aneurysms following FD as compared to SAC. FD and SAC have comparable mortality rates and favorable outcomes. Ischemic onset, unilateral vertebral artery sacrifice, and older age could increase the risk of complications.

Increasing Vascular Response to Injury Improves Tendon Early Healing Outcome in Aged Rats

Tendon injuries positively correlate with patient age, as aging has significant effects on tendon homeostatic maintenance and healing potential after injury. Vascularity is also influenced by age, with both clinical and animal studies demonstrating reduced blood flow in aged tissues. However, it is unknown how aging effects vascularity following tendon injury, and if this vascular response can be modulated through the delivery of angiogenic factors. Therefore, the objective of this study is to evaluate the vascular response following Achilles tendon injury in adult and aged rats, and to define the alterations to tendon healing in an aged model following injection of angiogenic factors. It was determined that aged rat Achilles tendons have a reduced angiogenesis following injury. Further, the delivery of vascular endothelial growth factor, VEGF, caused an increase in vascular response to tendon injury and improved mechanical outcome in this aged population. This work suggests that reduced angiogenic potential with aging may be contributing to impaired tendon healing response and that the delivery of angiogenic factors can rescue this impaired response. This study was also the first to relate changes in vascular response in an aged model using in vivo measures of blood perfusion to alterations in healing properties.

Treadmill Exercise Training Ameliorates Functional and Structural Age-Associated Kidney Changes in Male Albino Rats

Aging is a biological process that impacts multiple organs. Unfortunately, kidney aging affects the quality of life with high mortality rate. So, searching for innovative nonpharmacological modality improving age-associated kidney deterioration is important. This study aimed to throw more light on the beneficial effect of treadmill exercise on the aged kidney. Thirty male albino rats were divided into three groups: young (3-4 months old), sedentary aged (23-24 months old), and exercised aged (23-24 months old, practiced moderate-intensity treadmill exercise 5 days/week for 8 weeks). The results showed marked structural alterations in the aged kidney with concomitant impairment of kidney functions and increase in arterial blood pressure with no significant difference in kidney weight. Also, it revealed that treadmill exercise alleviated theses effects in exercised aged group with reduction of urea and cystatin C. Exercise training significantly decreased glomerulosclerosis index, tubular injury score, and % area of collagen deposition. Treadmill exercise exerted its beneficial role via a significant reduction of C-reactive protein and malondialdehyde and increase in total antioxidant capacity. In addition, exercise training significantly decreased desmin immunoreaction and increased aquaporin-3, vascular endothelial growth factor, and beclin-1 in the aged kidney. This study clarified that treadmill exercise exerted its effects via antioxidant and anti-inflammatory mechanisms, podocyte protection, improving aquaporin-3 and vascular endothelial growth factor expression, and inducing autophagy in the aged kidney. This work provided a new insight into the promising role of aerobic exercise to ameliorate age-associated kidney damage.

A historical view of estrogen effect on arterial endothelial healing: From animal models to medical implication

Endothelial barrier integrity is required for maintaining vascular homeostasis and fluid balance between the circulation and surrounding tissues. In contrast, abnormalities of endothelial cell function and loss of the integrity of the endothelial monolayer constitute a key step in the onset of atherosclerosis. Endothelial erosion is directly responsible for thrombus formation and cardiovascular events in about one-third of the cases of acute coronary syndromes. Thus, after endothelial injury, the vascular repair process is crucial to restore endothelial junctions and rehabilitate a semipermeable barrier, preventing the development of vascular diseases. Endothelial healing can be modulated by several factors. In particular, 17β-estradiol (E2), the main estrogen, improves endothelial healing, reduces neointimal accumulation of smooth muscle cells and atherosclerosis in several animal models. The aim of this review is to highlight how various experimental models enabled the progress in the cellular and molecular mechanisms underlying the accelerative E2 effect on arterial endothelial healing through the estrogen receptor (ER) α, the main receptor mediating the physiological effects of estrogens. We first summarize the different experimental procedures used to reproduce vascular injury. We then provide an overview of how the combination of transgenic mouse models impacting ERα signalling with pharmacological tools demonstrated the pivotal role of non-genomic actions of ERα in E2-induced endothelial repair. Finally, we describe recent advances in the action of selective estrogen receptor modulators (SERMs) on this beneficial vascular effect, which surprisingly involves different cell types and activates different ERα subfunctions compared to E2.

Endothelial Progenitor Cells in Moyamoya Disease: Current Situation and Controversial Issues

Due to the lack of animal models and difficulty in obtaining specimens, the study of pathogenesis of moyamoya disease (MMD) almost stagnated. In recent years, endothelial progenitor cells (EPCs) have attracted more and more attention in vascular diseases due to their important role in neovascularization. With the aid of paradigms and methods in cardiovascular diseases research, people began to explore the role of EPCs in the processing of MMD. In the past decade, studies have shown that abnormalities in cell amounts and functions of EPCs were closely related to the vascular pathological changes in MMD. However, the lack of consistent criteria, such as isolation, cultivation, and identification standards, is also blocking the way forward. The goal of this review is to provide an overview of the current situation and controversial issues relevant to studies about EPCs in the pathogenesis and etiology of MMD.

Elevated Levels of the Endothelial Molecules ICAM-1, VEGF-A, and VEGFR2 in Microscopic Asymptomatic Malaria

Background

In malaria, clinical disease has been associated with increased levels of endothelial activation due to the sequestration of infected erythrocytes. However, the levels and impact of endothelial activation and pro-angiogenic molecules such as vascular endothelial growth factor (VEGF)–A and its receptor vascular endothelial growth factor receptor 2 (VEGFR2) in asymptomatic malaria have not been well characterized.

Methods

Blood samples were obtained from community children for malaria diagnosis using microscopy and polymerase chain reaction. A multiplex immunoassay was used to determine the levels of intracellular adhesion molecule (ICAM)–1, vascular endothelial growth factor (VEGF)–A, and VEGFR2 in the plasma of children with microscopic or submicroscopic asymptomatic parasitemia and compared with levels in uninfected controls.

Results

Levels of ICAM-1, VEGF-A, and VEGFR2 were significantly increased in children with microscopic asymptomatic parasitemia compared with uninfected controls. Also, levels of VEGF-A were found to be inversely associated with age. Additionally, a receiver operating characteristic analysis revealed that plasma levels of ICAM-1 (area under the curve [AUC], 0.72) showed a moderate potential in discriminating between children with microscopic malaria from uninfected controls when compared with VEGF-A (AUC, 0.67) and VEGFR2 (AUC, 0.69).

Conclusions

These data imply that endothelial activation and pro-angiogenic growth factors could be one of the early host responders during microscopic asymptomatic malaria and may play a significant role in disease pathogenesis.

Impact of age on cerebral aneurysm occlusion after flow diversion

The purpose of this study was to evaluate safety and efficacy of the pipeline embolization device (PED) in different patient age groups with unruptured intracranial aneurysms (UIA). All patients with UIA treated with the PED between 2011 and 2017 were included. Based on their age, patients were trichotomized to: young (≤45 years), middle-aged (46 to <65 years) and older (≥65 years) groups. Patient's vascular risk factors, presenting symptoms and mRS on admission were collected. Follow-up imaging was evaluated for presence/absence of aneurysm occlusion. Clinical outcome at discharge, 3-9 months and 12-18 months was also documented when available. A total of 260 patients harboring 307 aneurysms (young = 57, middle-age = 144 and older age group = 64). Most aneurysms were located in the anterior circulation (94.8%). Overall morbidity and mortality was 2.3% each (6/260). At 3-9 months near complete to complete aneurysm occlusion was 82.5% (47/57) in the young age group, 82.6% (100/121) in the middle age, and 70.2% (40/57) in the older age group. At 12-18-month, near complete to complete occlusion was 100% in the young age group (32/32), 91.4% (64/70) in the middle age, and 78.4% (29/37) in the older age group. After adjustment for potential confounders, older age patients less frequently achieved near complete to complete occlusion by 3 years than younger subjects (p = 0.009, HR 1.34 95%, CI 1.08-1.66). Our results indicate feasibility and safety of PED across different age groups. Further study is required to determine age-related factors relating to aneurysm occlusion after PED to improve outcome and patient counseling.

Adult venous endothelium is a niche for highly proliferative and vasculogenic endothelial colony-forming cells

OBJECTIVE

Postnatal resident endothelium of blood vessels has been proposed to represent terminally differentiated tissue that does not replicate. We previously isolated endothelial colony-forming cells (ECFCs) from human umbilical cord blood (CB) and term placenta by using colony-forming assays and immunocytochemistry. We showed that ECFCs are highly proliferative and form functioning vessels in vivo, the defining characteristics of a true endothelial progenitor cell. This exploratory investigation was conducted to determine whether the endothelium of healthy adult blood vessels contained resident ECFCs.

METHODS

The endothelium of great saphenous vein (GSV) obtained from vein stripping procedures was collected with mechanical scraping, and ECFCs were isolated according to established protocols.

RESULTS

GSV ECFCs incorporated acetylated low-density lipoprotein, formed tubules in Matrigel (BD Biosciences, San Jose, Calif) at 24 hours, and expressed endothelial antigens cluster of differentiation (CD) 144, CD31, CD105, and kinase insert domain receptor but not hematopoietic antigen CD45. Using cumulative population doublings and single-cell assays, we demonstrated that GSV ECFCs exhibited comparable proliferative capacities compared with CB ECFCs, including similar numbers of highly proliferative cells. When injected in collagen/fibronectin gels implanted in nonobese diabetic/severe combined immune deficiency mice, GSV ECFCs formed blood vessels with circulating murine red blood cells, demonstrating their vasculogenic potential.

CONCLUSIONS

The ECFCs of the GSV contain a hierarchy of progenitor cells with a comparable number of highly proliferative clones as ECFCs of CB. The results of this investigation demonstrate that the adult endothelium contains resident progenitor cells that may have a critical role in vascular homeostasis and repair and could potentially be used as a source of autologous cells for cell therapies focusing on vasculogenesis.

Magnetic nanosphere-guided site-specific delivery of vascular endothelial growth factor gene attenuates restenosis in rabbit balloon-injured artery

OBJECTIVE

New and efficient strategies to protect endothelium or to enhance endothelial regrowth are important for treatment of restenosis after percutaneous transluminal angioplasty. Magnetic DNA microspheres are used to accelerate vascular endothelial growth factor (VEGF) re-endothelialization and to attenuate intimal hyperplasia in balloon-injured artery. This study aimed to assess DNA-gelatin magnetic nanospheres containing VEGF expression plasmids in vascular restenosis attenuation.

METHODS

Ninety-six rabbits underwent balloon injury and were randomly divided for gene transfer with naked VEGF plasmids (NAK group), magnetic VEGF microspheres (MIC group), and LacZ (CON group: naked LacZ plasmid and LacZ nanosphere subgroups). Serum and tissue VEGF levels were measured. Also, the ratios of intima area to media area were determined to assess neointima formation.

RESULTS

Microsphere gene delivery through the artery by a magnet resulted in VEGF overexpression in transfected arterial segments. Tissue VEGF integral optical densities were significantly increased in MIC rabbits compared with NAK animals. Serum VEGF was below detection in all animals. X-Gal staining showed higher transfection efficiency in the CON group. The impact of neointimal thickening was evaluated by light microscopy as the ratio of intima area to media area in cross sections. Significant differences in the ratio of intima area to media area were obtained between the NAK group (0.12 ± 0.02, 0.41 ± 0.03, 0.61 ± 0.05, and 0.72 ± 0.04 at 1, 2, 3, and 4 weeks, respectively) and the MIC group (0.06 ± 0.03, 0.20 ± 0.05, 0.25 ± 0.04, and 0.26 ± 0.03 at 1, 2, 3, and 4 weeks, respectively) at 2, 3, and 4 weeks (P < .05).

CONCLUSIONS

Intra-arterial VEGF gene delivery by magnetic microspheres significantly increased DNA stability, transfection efficiency, and targeting specificity, resulting in exogenous VEGF overexpression and attenuated intimal hyperplasia in balloon-injured artery.

Aging impairs VEGF-mediated, androgen-dependent regulation of angiogenesis

There is a progressive impairment of vascular repair mechanisms with advancing age concomitant with a steady decline in circulating androgen levels in men. Emerging evidence indicates androgens regulate angiogenesis; however, little research has focused on the impact of age upon androgen-mediated regulation of angiogenic mechanisms. Human dermal fibroblasts from young (<30 years) and older (>65 years) men were incubated with DHT, with or without androgen receptor antagonist hydroxyflutamide, or phosphoinositide 3-kinase inhibitor. Fibroblast-conditioned medium was used to stimulate angiogenic functions in human umbilical vein endothelial cells. Nuclear fractionation and fluorescence microscopy were used to study androgen receptor (AR) distribution. Conditioned medium from fibroblasts of young men, but not old men, treated with DHT produced a 3-fold increase in human umbilical vein endothelial cell tubulogenesis and 2-fold increase in migration via increased vascular endothelial growth factor (VEGF) expression and secretion, predominantly of VEGF145. DHT-induced VEGF secretion from fibroblasts of young men was AR-dependent and increased AKT phosphorylation, which was abrogated by phosphoinositide 3-kinase inhibition. By contrast, fibroblasts from older men were unresponsive to DHT and lacked androgen-mediated enhancement in VEGF production. These findings were associated with reduced AR nuclear translocation in old fibroblasts. The failure of DHT-induced paracrine stimulation of angiogenesis in fibroblasts from older men is likely due to defective nuclear translocation of AR. This first demonstration of androgen resistance (or insensitivity) acquired by human fibroblasts with aging suggests that pharmacological testosterone therapy for old men may be less effective in enhancing angiogenesis and facilitating tissue regeneration mechanisms reliant on paracrine release of VEGF.

The rejuvenation of aged stem cells for cardiac repair

Rejuvenation is one of the greatest challenges of modern science. Aging affects every tissue and organ in the body, leading to a deterioration of normal function and inhibition of repair mechanisms. Cell therapy has received much attention for its potential to regenerate organs, but in the context of cardiac repair, the initial clinical trials in aged patients did not replicate the dramatic benefits recorded in preclinical studies with young animals. The benefits of autologous cell therapy are reduced in the elderly, the largest target group for regenerative medicine. Adult stem cell functionality decreases with age which impairs tissue regeneration. In this review we discuss the age-related changes in stem cell function, with particular attention to stem cell therapy in heart disease. We also focus on possible mechanisms of adult stem cell aging and targets for rejuvenation strategies to reverse the aging process. We provide useful insights on how to apply this knowledge to advance cellular therapies for heart disease.

Analysis of CD45- [CD34+/KDR+] endothelial progenitor cells as juvenile protective factors in a rat model of ischemic-hemorrhagic stroke

Background

Identification of juvenile protective factors (JPFs) which are altered with age and contribute to adult-onset diseases could identify novel pathways for reversing the effects of age, an accepted non-modifiable risk factor to adult-onset diseases. Since endothelial progenitor cells (EPCs) have been observed to be altered in stroke, hypertension and hypercholesterolemia, said EPCs are candidate JPFs for adult-onset stroke. A priori, if EPC aging plays a ‘master-switch JPF-role’ in stroke pathogenesis, juvenile EPC therapy alone should delay stroke-onset. Using a hypertensive, transgenic-hyperlipidemic rat model of spontaneous ischemic-hemorrhagic stroke, spTg25, we tested the hypothesis that freshly isolated juvenile EPCs are JPFs that can attenuate stroke progression and delay stroke onset.

Methodology/Principal Findings

FACS analysis revealed that cd45- [cd34+/kdr+] EPCs decrease with progression to stroke in spTg25 rats, exhibit differential expression of the dual endodthelin-1/VEGFsp receptor (DEspR) and undergo differential DEspR-subtype specific changes in number and in vitro angiogenic tube-incorporation. In vivo EPC infusion of male, juvenile non-expanded cd45-[cd34+/kdr+] EPCs into female stroke-prone rats prior to stroke attenuated progression and delayed stroke onset (P<0.003). Detection of Y-chromosome DNA in brain microvessels of EPC-treated female spTg25 rats indicates integration of male EPCs into female rat brain microvessels. Gradient-echo MRI showed delay of ischemic-hemorrhagic lesions in EPC-treated rats. Real-time RT-PCR pathway-specific array-analysis revealed age-associated gene expression changes in cd45-[cd34+/kdr]EPC subtypes, which were accelerated in stroke-prone rats. Pro-angiogenic genes implicated in intimal hyperplasia were increased in stroke-prone rat EPCs (P<0.0001), suggesting a maladaptive endothelial repair system which acts like a double-edged sword repairing while predisposing to age-associated intimal hyperplasia.

Conclusions/Significance

Altogether, the data demonstrate that cd45-[cd34/kdr+]EPCs are juvenile protective factors for ischemic hemorrhagic stroke as modeled in the spTg25-rat model. The ability to delay stroke onset emphasizes the importance of EPC-mediated roles in vascular health for ischemic-hemorrhagic stroke, a high unmet need.

Vitreous mediators in retinal hypoxic diseases

The causes of retinal hypoxia are many and varied. Under hypoxic conditions, a variety of soluble factors are secreted into the vitreous cavity including growth factors, cytokines, and chemokines. Cytokines, which usually serve as signals between neighboring cells, are involved in essentially every important biological process, including cell proliferation, inflammation, immunity, migration, fibrosis, tissue repair, and angiogenesis. Cytokines and chemokines are multifunctional mediators that can direct the recruitment of leukocytes to sites of inflammation, promote the process, enhance immune responses, and promote stem cell survival, development, and homeostasis. The modern particle-based flow cytometric analysis is more direct, stable and sensitive than the colorimetric readout of the conventional ELISA but, similar to ELISA, is influenced by vitreous hemorrhage, disruption of the blood-retina barrier, and high serum levels of a specific protein. Finding patterns in the expression of inflammatory cytokines specific to a particular disease can substantially contribute to the understanding of its basic mechanism and to the development of a targeted therapy.

Low intensity laser therapy accelerates muscle regeneration in aged rats

BACKGROUND

Elderly people suffer from skeletal muscle disorders that undermine their daily activity and quality of life; some of these problems can be listed as but not limited to: sarcopenia, changes in central and peripheral nervous system, blood hypoperfusion, regenerative changes contributing to atrophy, and muscle weakness. Determination, proliferation and differentiation of satellite cells in the regenerative process are regulated by specific transcription factors, known as myogenic regulatory factors (MRFs). In the elderly, the activation of MRFs is inefficient which hampers the regenerative process. Recent studies found that low intensity laser therapy (LILT) has a stimulatory effect in the muscle regeneration process. However, the effects of this therapy when associated with aging are still unknown.

OBJECTIVE

This study aimed to evaluate the effects of LILT (λ=830 nm) on the tibialis anterior (TA) muscle of aged rats.

SUBJECTS AND METHODS

The total of 56 male Wistar rats formed two population sets: old and young, with 28 animals in each set. Each of these sets were randomly divided into four groups of young rats (3 months of age) with n=7 per group and four groups of aged rats (10 months of age) with n=7 per group. These groups were submitted to cryoinjury + laser irradiation, cryoinjury only, laser irradiation only and the control group (no cryoinjury/no laser irradiation). The laser treatment was performed for 5 consecutive days. The first laser application was done 24 h after the injury (on day 2) and on the seventh day, the TA muscle was dissected and removed under anesthesia. After this the animals were euthanized. Histological analyses with toluidine blue as well as hematoxylin-eosin staining (for counting the blood capillaries) were performed for the lesion areas. In addition, MyoD and VEGF mRNA was assessed by quantitative polymerase chain reaction.

RESULTS

The results showed significant elevation (p<0.05) in MyoD and VEGF genes expression levels. Moreover, capillary blood count was more prominent in elderly rats in laser irradiated groups when compared to young animals.

CONCLUSION

In conclusion, LILT increased the maturation of satellite cells into myoblasts and myotubes, enhancing the regenerative process of aged rats irradiated with laser.

Combined age- and trauma-related proteomic changes in rat neocortex: a basis for brain vulnerability

This proteomic study investigates the widely observed clinical phenomenon, that after comparable brain injuries, geriatric patients fare worse and recover less cognitive and neurologic function than younger victims. Utilizing a rat traumatic brain injury model, sham surgery or a neocortical contusion was induced in 3 age groups. Geriatric (21 months) rats performed worse on behavioral measures than young adults (12-16 weeks) and juveniles (5-6 weeks). Motor coordination and certain cognitive deficits showed age-dependence both before and after injury. Brain proteins were analyzed using silver-stained two-dimensional electrophoresis gels. Spot volume changes (>2-fold change, p<0.01) were identified between age and injury groups using computer-assisted densitometry. Sequences were determined by mass spectrometry of tryptic peptides. The 19 spots identified represented 13 different genes that fell into 4 general age- and injury-dependent expression patterns. Fifteen isoforms changed differentially with respect to both age and injury (p<0.05). Further investigations into the nature and function of these isoforms may yield insights into the vulnerability of older patients and resilience of younger patients in recovery after brain injuries.

Age-related Notch-4 quiescence is associated with altered wall remodeling during vein graft adaptation

BACKGROUND

The link of aging to specific mechanisms of vascular biology is not well understood. We have previously shown that aging is associated with increased vein graft wall thickness and that this process involves the VEGF-Delta/Notch-ephrin/Eph cascade. Therefore, we examined whether Dll-4 or Notch-4 are differentially expressed, according to age, during vein graft adaptation.

MATERIALS AND METHODS

Vein grafts were performed in 6-mo and 24-mo Fischer 344 rats. Gene expression was analyzed by quantitative real-time PCR, and the distribution of Dll-4 and Notch-4 was observed by immunofluorescence.

RESULTS

The expression of Dll-4 and Notch-4 was reduced in vein grafts performed in aged rats compared with the expression in young adult rats. Both Dll-4 and Notch-4 were distributed in vein graft endothelium as well as the outer adventitia, with reduced amounts in the outer adventitia of aged vein grafts. Aged veins had reduced eNOS membrane targeting and colocalization with caveolin-1 as well as reduced eNOS protein expression in comparison to young adult veins. In an exchange model between young and aged animals, heterogeneous vein grafts (Yo(Ag) and Ag(Yo)) showed significantly thicker neointima compared with young (Yo(Yo)) controls, and had Notch-4-positive cells, but not Dll-4-positive cells, diminished in the adventitia. Vein grafts that were air-denuded of endothelium did not show any adaptation to the arterial environment and also lacked both Dll-4 and Notch-4 expression at 3 wk.

CONCLUSIONS

During vein graft adaptation to the arterial environment, both Dll-4 and Notch-4 expression are down-regulated in an aged, but not a young, background. Loss of Notch-4 is associated with loss of attenuation of neointima. The delta-Notch signaling pathway may be active during vein graft adaptation.

Angiogenic properties of aged adipose derived mesenchymal stem cells after hypoxic conditioning

Background

Mesenchymal stem cells derived from adipose tissue (ADSC) are multipotent stem cells, originated from the vascular-stromal compartment of fat tissue. ADSC are used as an alternative cell source for many different cell therapies, however in ischemic cardiovascular diseases the therapeutic benefit was modest. One of the reasons could be the use of autologous aged ADSC, which recently were found to have impaired functions. We therefore analysed the effects of age on age markers and angiogenic properties of ADSC. Hypoxic conditioning was investigated as a form of angiogenic stimulation.

Methods

ADSC were harvested from young (1-3 month), adult (12 month) and aged (18-24 month) mice and cultured under normoxic (20%) and hypoxic (1%) conditions for 48 h. Differences in proliferation, apoptosis and telomere length were assessed in addition to angiogenic properties of ADSC.

Results

Proliferation potential and telomere length were decreased in aged ADSC compared to young ADSC. Frequency of apoptotic cells was higher in aged ADSC. Gene expression of pro-angiogenic factors including vascular endothelial growth factor (VEGF), placental growth factor (PlGF) and hepatic growth factor (HGF) were down-regulated with age, which could be restored by hypoxia. Transforming growth factor (TGF-β) increased in the old ADSC but was reduced by hypoxia.

Expression of anti-angiogenic factors including thrombospondin-1 (TBS1) and plasminogen activator inhibitor-1 (PAI-1) did increase in old ADSC, but could be reduced by hypoxic stimulation. Endostatin (ENDS) was the highest in aged ADSC and was also down-regulated by hypoxia. We noted higher gene expression of proteases system factors like urokinase-type plasminogen activator receptor (uPAR), matrix metalloproteinases (MMP2 and MMP9) and PAI-1 in aged ADSC compared to young ADSC, but they decreased in old ADSC. Tube formation on matrigel was higher in the presence of conditioned medium from young ADSC in comparison to aged ADSC.

Conclusions

ADSC isolated from older animals show changes, including impaired proliferation and angiogenic stimulation. Angiogenic gene expression can be partially be improved by hypoxic preconditioning, however the effect is age-dependent. This supports the hypothesis that autologous ADSC from aged subjects might have an impaired therapeutic potential.

Preventing negative effects of smoking on microarterial anastomosis

Although microsurgery has rapid expanded, problems related to microarterial anastomosis continue. Cigarette smoking is one of the major risks for anastomosis by increasing platelet adhesion, and its effects on endothelial cells. Aim of this article is to study the negative effects of cigarettes on microarterial anastomosis line, and to investigate the protective effects of recombinant human erythropoietin (rHuEPO).Ninety-six Sprague-Dawley male rats were divided into 3 groups: group 1 was the control. Rats in groups 2 and 3 were exposed to cigarette smoke starting 21 days prior to surgery for 3 times a day. In group 3, additional 150 IU/kg rHuEPO was given via subcutaneously every 48 hours after microvascular anastomosis, femoral arterial samples, and blood samples were taken for assessment at 1st, 3rd, 5th, and 7th day. Intimae/media ratios were calculated for morphologic analyses.On morphologic analysis of femoral arteries there were statistically significant differences for all 3 groups at 1st, 3rd, 5th, and 7th days (P < 0, 05). The group that made differences was group 2, according to one-way analysis of variance within 3 groups in all days.Smoking decreases endothelial cells healing and causes more thromboses. rHuEPO can prevent these negative effects of smoking.

Aging impairs the angiogenic response to ischemic injury and the activity of implanted cells: combined consequences for cell therapy in older recipients

OBJECTIVE

Cell therapy has received much attention for its potential to regenerate ischemic organs, but initial clinical trials in aged patients did not replicate the dramatic benefits recorded in preclinical studies with young animals. This study was designed to improve our understanding of age-related changes in the response to ischemic injury and the regenerative capacity of implanted cells in the context of cell therapy for older recipients.

METHODS AND RESULTS

Restoration of regional perfusion after hind limb femoral artery ligation was impaired (P < .05) in old (vs young) rats, reflecting approximately 50% reductions in circulating endothelial progenitor cells and the release of vascular endothelial growth factor/basic fibroblast growth factor. Bone marrow stromal cells from young or old donors implanted into the ischemic hind limbs of young or old rats restored regional perfusion. Specifically, we documented significantly greater (P < .05) angiogenic potential in young (vs old) donor cells when recipient age was controlled and greater (P < .05) regenerative responses in young (vs old) recipients when donor cell age was controlled. Contributing to these differences were significantly greater survival in young (vs old) donor cells (in vitro and after implantation) and about 2-fold more production of vascular endothelial growth factor/basic fibroblast growth factor and mobilization of endogenous endothelial progenitor cells in young (vs old) rats in response to ischemia.

CONCLUSIONS

The outcome of cell therapy in older recipients is determined by a combination of age effects on the donor cells and on the recipients' endogenous responses. Donor cell age and recipient age are equally important contributors to the outcome of cell therapy; thus, novel biointerventions will need to target both components of the process.

Vein wall remodeling after deep vein thrombosis: differential effects of low molecular weight heparin and doxycycline

BACKGROUND

Venous thrombus resolution sets up an early intense inflammatory reaction, from which vein wall damage results. Tissue response to injury includes matrix metalloproteinase (MMP) activation and extracellular matrix protein turnover. This study sought to determine the effect of exogenous MMP inhibition and its potential attenuation of early vein wall injury.

METHODS

Rats received treatment beginning 24 hr after a stasis venous thrombosis by near occlusive ligation and until harvest at day 7. Three groups were evaluated: (1) vehicle saline controls (NaCl), (2) low molecular weight heparin (LMWH; Lovenox, 3 mg/kg daily SQ), and (3) doxycycline (DOXY, 30 mg/kg daily PO). Thrombus size (mg/mm), levels of tumor necrosis factor alpha (TNF alpha) and D-dimer by colorimetric assay, and monocytes counts by immunohistochemistry were assessed. Vein wall assessment included stiffness by tensiometry, interleukin 1beta (IL-1 beta protein levels by enzyme-linked immunosorbent assay, MMP2 and -9 by zymography, and histological analysis of intimal thickness (IT). Comparisons were by t-test to control. p < 0.05 was considered significant.

RESULTS

Thrombus sizes were similar at days 2 and 7 for all three groups, while thrombus TNFalpha was increased in 2-day LMWH- and DOXY-treated groups (NaCl = 1.0 +/- 0.8, LWMH = 9 +/- 3, DOXY = 27 +/- 5 pg/mg protein, n = 6-8, p < 0.05) and at 7 days in the DOXY group (NaCl = 3.0 +/- 2.5, DOXY = 23 +/- 4.2 pg/mg protein, n = 5, p < 0.05). Vein wall stiffness at 7 days was less with LMWH treatment, but not with DOXY, compared to controls (NaCl = 0.33 +/- 0.05, LMWH = 0.17 +/- 0.03, DOXY = 0.43 +/- 0.09 N/mm, n = 5-7, p < 0.05). Vessel-wall IL-1 beta was reduced only in the DOXY group at 7 days (NaCl = 26 +/- 3, LMWH = 38 +/- 17, DOXY = 6 +/- 3 pg/mg protein, n = 4-6, p < 0.05), as was the IT score versus controls (NaCl = 2.2 +/- 0.6, LMWH =1.7 +/- 0.3, DOXY = 0.8 +/- 0.20, n = 4-6, p < 0.05). Zymographic MMP9 activity was significantly reduced at 2 days in the LMWH and DOXY groups (NaCl = 85 +/- 24, LMWH = 23 +/- 7( *), DOXY = 13 +/- 5 U/mg protein, n = 6-8, p < 0.05). MMP2 zymographic activity, thrombus monocyte cell counts, and D-dimer activity were not significantly different across groups.

CONCLUSION

Treatment with LMWH or DOXY did not alter the size of deep vein thrombosis, mildly altered thrombus composition, and differentially affected vein wall injury, despite similar reductions in early MMP9 activity. Whether exogenous MMP inhibition affects long-term vein wall fibrosis will require further study.

Role of non-neuronal nicotinic acetylcholine receptors in angiogenesis

Angiogenesis is a critical physiological process for cell survival and development. Endothelial cells, necessary for the course of angiogenesis, express several non-neuronal nicotinic acetylcholine receptors (AChRs). The most important functional non-neuronal AChRs are homomeric alpha7 AChRs and several heteromeric AChRs formed by a combination of alpha3, alpha5, beta2, and beta4 subunits, including alpha3beta4-containing AChRs. In endothelial cells, alpha7 AChR stimulation indirectly triggers the activation of the integrin alphavbeta3 receptor and an intracellular MAP kinase (ERK) pathway that mediates angiogenesis. Non-selective cholinergic agonists such as nicotine have been shown to induce angiogenesis, enhancing tumor progression. Moreover, alpha7 AChR selective antagonists such as alpha-bungarotoxin and methyllycaconitine as well as the non-specific antagonist mecamylamine have been shown to inhibit endothelial cell proliferation and ultimately blood vessel formation. Exploitation of such pharmacologic properties can lead to the discovery of new specific cholinergic antagonists as anti-cancer therapies. Conversely, the pro-angiogenic effect elicited by specific agonists can be used to treat diseases that respond to revascularization such as diabetic ischemia and atherosclerosis, as well as to accelerate wound healing. In this mini-review we discuss the pharmacological evidence supporting the importance of non-neuronal AChRs in angiogenesis. We also explore potential intracellular mechanisms by which alpha7 AChR activation mediates this vital cellular process.

Vein wall re-endothelialization after deep vein thrombosis is improved with low-molecular-weight heparin

OBJECTIVE

Vein wall endothelial turnover after stasis deep vein thrombosis (DVT) has not been well characterized. The purpose of this study was to quantify re-endothelialization after DVT and determine if low-molecular-weight heparin (LMWH) therapy affects this process.

METHODS

Stasis DVT was generated in the rat by inferior vena cava ligation, with harvest at 1, 4, and 14 days. Immunohistologic quantification of vascular smooth muscle cells and luminal endothelialization was estimated by positive staining for alpha-smooth muscle actin and von Willebrand factor, respectively. In separate experiments, rats were treated either before or after DVT with subcutaneous LMWH (3 mg/kg daily) until harvesting at 4 and 14 days. The inferior vena cava was processed for histologic analysis or was processed for organ culture after the thrombus was gently removed. The vein wall was stimulated in vitro with interleukin-1beta (1 ng/mL), and the supernatant was processed at 48 hours for nitric oxide. Cells were processed by real-time polymerase chain reaction for endothelial nitric oxide synthase, inducible nitric oxide synthase, cyclooxygenase-1 and -2, and thrombomodulin at 4 and 14 days, and collagen I and III at 14 days. Comparisons were done with analysis of variance or t test. A P < .05 was significant.

RESULTS

Thrombus size peaked at 4 days, whereas luminal re-endothelialization increased over time (1 day, 11% +/- 2%; 4 days, 23% +/- 4%; 14 days, 64% +/- 7% (+) von Willebrand factor staining; P < .01, n = 3 to 4, compared with non-DVT control). Similarly, vascular smooth muscle cell staining was lowest at day 1 and gradually returned to baseline by 14 days. Both before and after DVT, LMWH significantly increased luminal re-endothelialization, without a difference in thrombus size at 4 days, but no significant difference was noted at 14 days despite smaller thrombi with LMWH treatment. Pretreatment with LMWH was associated with increased vascular smooth muscle cell area and recovery of certain inducible endothelial specific genes. No significant difference in nitric oxide levels in the supernatant was found at 4 days. At 14 days, type III collagen was significantly elevated with LMWH treatment.

CONCLUSIONS

Venous re-endothelialization occurs progressively as the DVT resolves and can be accelerated with LMWH treatment, although this effect appears limited to the early time frame. These findings may have clinical relevance for LMWH timing and treatment compared with mechanical forms of therapy.

CLINICAL RELEVANCE

How the vein wall endothelium responds after deep vein thrombosis (DVT) has not been well documented owing to limited human specimens. This report shows that low-molecular-weight heparin accelerates or protects the endothelium and preserves medial smooth muscle cell integrity after DVT, but that this effect is limited to a relatively early time period. Although most DVT prophylaxis is pharmacologic (a heparin agent), use of nonpharmacologic measures is also common. The use of heparin prophylaxis, compared with after DVT treatment, and the acceleration of post-DVT re-endothelialization require clinical correlation.

Endothelial progenitor cells, late stent thrombosis and delayed re-endothelialisation

A decade ago, the description of a primitive novel cell type capable of differentiating into cells expressing a mature endothelial cell -phenotype and their capacity to incorporate into regions of active angiogenesis, witnessed the emergence of endothelial progenitor cell (EPC) biology1. The development and maturation of this new concept in vascular biology has resulted in numerous studies describing the role of EPCs in a myriad of disease states where abnormalities of the vasculature have been implicated. Thus, from pre-eclampsia to pulmonary hypertension, erythropoietin administration to erectile dysfunction and cancer to coronary disease the discovery of EPCs has added greatly to the understanding of basic pathophysiology. However, it is in the study of coronary artery -disease where this paradigm shift has had greatest impact, not only regarding basic disease mechanisms, but in the rapid translation of these findings into a clinical context. The purpose of this review is to outline the current understanding of the EPC phenotypes and their relationship with risk factors for coronary disease. In addition, the potential problems of EPC dysfunction and its impact on percutaneous intervention will be appraised together with both pharmacological and stent based strategies to augment EPC -number and function.

Bone marrow-derived cells: the influence of aging and cellular senescence

During the course of an entire lifespan, tissue repair and regeneration is made possible by the presence of adult stem cells. Stem cell expansion, maintenance, and differentiation must be tightly controlled to assure longevity. Hematopoietic stem cells (HSC) are greatly solicited given the daily high blood cell turnover. Moreover, several bone marrow-derived cells including HSC, mesenchymal stromal cells (MSC), and endothelial progenitor cells (EPC) also significantly contribute to peripheral tissue repair and regeneration, including tumor formation. Therefore, factors influencing bone marrow-derived cell proliferation and functions are likely to have a broad impact. Aging has been identified as one of these factors. One hypothesis is that aging directly affects stem cells as a consequence of exhaustive proliferation. Alternatively, it is also possible that aging indirectly affects stem cells by acting on their microenvironment. Cellular senescence is believed to have evolved as a tumor suppressor mechanism capable of arresting growth to reduce risk of malignancy. In opposition to apoptosis, senescent cells accumulate in tissues. Recent evidence suggests their accumulation contributes to the phenotype of aging. Senescence can be activated by both telomere-dependent and telomere-independent pathways. Genetic alteration, genome-wide DNA damage, and oxidative stress are inducers of senescence and have recently been identified as occurring in bone marrow-derived cells. Below is a review of the link between cellular senescence, aging, and bone marrow-derived cells, and the possible consequences aging may have on bone marrow trans plantation procedures and emerging marrow-derived cell-based therapies.

Principles and therapeutic implications of angiogenesis, vasculogenesis and arteriogenesis

The vasculature is the first organ to arise during development. Blood vessels run through virtually every organ in the body (except the avascular cornea and the cartilage), assuring metabolic homeostasis by supplying oxygen and nutrients and removing waste products. Not surprisingly therefore, vessels are critical for organ growth in the embryo and for repair of wounded tissue in the adult. Notably, however, an imbalance in angiogenesis (the growth of blood vessels) contributes to the pathogenesis of numerous malignant, inflammatory, ischaemic, infectious and immune disorders. During the last two decades, an explosive interest in angiogenesis research has generated the necessary insights to develop the first clinically approved anti-angiogenic agents for cancer and blindness. This novel treatment is likely to change the face of medicine in the next decade, as over 500 million people worldwide are estimated to benefit from pro- or anti-angiogenesis treatment. In this following chapter, we discuss general key angiogenic mechanisms in health and disease, and highlight recent developments and perspectives of anti-angiogenic therapeutic strategies.

Endothelial cell senescence

The wear and tear processes that are thought to contribute to human ageing may play an important role in the development of vascular diseases. One such process is cellular senescence. In endothelial cells the senescent phenotype can be induced by a number of factors, including telomere damage, oxidative stress and sustained mitogenic stimulation. Several lines of evidence indicate that endothelial cell senescence maybe relevant to vascular disease. In this chapter we examine the causes, mechanisms and regulation of endothelial cell senescence as they emerge from studies in cell culture. We also describe the senescent phenotype and discuss its pathophysiological implications. We review the evidence for the occurrence of endothelial cell senescence in vivo and examine findings in animal models of ageing and human genetic disorders that argue for and against a role of endothelial cell senescence in age-related vascular pathology. Finally, we address the particular case of endothelial progenitor cell senescence and discuss the relevance of this phenomenon for angiogenesis and vascular repair.

Cigarette smoke exposure impairs VEGF-induced endothelial cell migration: role of NO and reactive oxygen species

Endothelial dysfunction is one of the earliest pathological effects of cigarette smoking. Vascular endothelial growth factor (VEGF) has been shown to be an important regulator of endothelial healing and growth. Accordingly, we tested the hypothesis that cigarette smoke exposure impairs VEGF actions in endothelial cells. In human umbilical vein endothelial cells (HUVECs), cigarette smoke extracts (CSE) inhibited VEGF-induced tube formation in the matrigel assay. CSE did not affect HUVECs proliferation, but significantly reduced cellular migration in response to VEGF. This impaired migratory activity was associated with a reduced expression of alpha(v)beta(3), alpha(v)beta(5), alpha(5)beta(1) and alpha(2)beta(1) integrins. The Akt/eNOS/NO pathway has been shown to be important for VEGF-induced endothelial cell migration. We found that CSE inhibited Akt/eNOS phosphorylation and NO release in VEGF-stimulated HUVECs. This was associated with an increased generation of reactive oxygen species (ROS). Importantly, in HUVECs exposed to CSE, treatment with antioxidants (NAC, vitamin C) reduced ROS formation and rescued VEGF-induced NO release, cellular migration and tube formation. Moreover, treatment with NO donors (SNAP, SNP) or a cGMP analog (8-Br-cGMP) rescued integrin expression, cellular migration and tube formation in endothelial cells exposed to CSE. (1) Cigarette smoke exposure impairs VEGF-induced endothelial cell migration and tube formation. (2) The mechanism involves increased generation of ROS, decreased expression of surface integrins together with a blockade of the Akt/eNOS/NO pathway. (3) These findings could contribute to explain the negative effect of cigarette smoking on endothelial function and vessel growth.

Peripheral blood as a source of stem cells for regenerative medicine

Converging evidence indicates that peripheral blood (PB) contains stem cells (SCs) with multidifferentiation potential, thus representing a potential source for regenerative medicine in several human disorders, as has also been confirmed by promising results obtained in several preliminary clinical trials. In addition to the classic haematopoietic SCs, PB also harbours endothelial progenitor cells, mesenchymal SCs, tissue-committed SCs and monocyte-like SCs. In spite of a series of different names and/or definitions, a large overlap seems to exist among surface markers, functions and origin of these different SC types. This review analyses the different subsets of SCs described in PB, the different hypotheses suggested to explain their origin, and the possible mechanisms that provide the basis for their biological potential.

No Age-Related Change in Circulating Endothelial Progenitor Cells in Healthy Subjects

Endothelial progenitor cells were isolated from peripheral blood obtained from 32 healthy volunteers without cardiovascular risk factors who ranged in age from 20 to 61 years (mean [+/- SD] age, 34.1 +/- 9.6 years). The fractions of CD34(+) endothelial progenitor cells expressing kinase insert domain receptor-1, CD62E, or CD31 were analyzed with flow cytometry. Correlation analysis demonstrated that there was no significant correlation between subject age and the fraction of circulating CD34(+) mononuclear cells expressing kinase insert domain receptor-1 (P = 0.324; r = -0.180). Similarly, there was no significant correlation between subject age and the fraction of circulating CD34(+) mononuclear cells expressing CD62E (P = 0.496; r = -0.125) or the fraction of circulating CD34(+) mononuclear cells expressing CD31 (P = 0.245; r = -0.212). In conclusion, the experimental results showed that there was no age-related change in the basal level of circulating endothelial progenitor cells in healthy subjects without cardiovascular risk factors.

Therapeutic potential of endothelial progenitor cells in cardiovascular diseases

Endothelial dysfunction and cell loss are prominent features in cardiovascular disease. Endothelial progenitor cells (EPCs) originating from the bone marrow play a significant role in neovascularization of ischemic tissues and in re-endothelialization of injured blood vessels. Several studies have shown the therapeutic potential of EPC transplantation in rescue of tissue ischemia and in repair of blood vessels and bioengineering of prosthetic grafts. Recent small-scale trials have provided preliminary evidence of feasibility, safety, and efficacy in patients with myocardial and critical limb ischemia. However, several studies have shown that age and cardiovascular disease risk factors reduce the availability of circulating EPCs (CEPCs) and impair their function to varying degrees. In addition, the relative scarcity of CEPCs limits the ability to expand these cells in sufficient numbers for some therapeutic applications. Priority must be given to the development of strategies to enhance the number and improve the function of CEPCs. Furthermore, alternative sources of EPC such as chord blood need to be explored. Strategies for improvement of cell adhesion, survival, and prevention of cell senescence are also essential to ensure therapeutic viability. Genetic engineering of EPCs may be a useful approach to developing these cells into efficient therapeutic tools. In the clinical arena there is pressing need to standardize the protocols for isolation, culture, and therapeutic application of EPC. Large-scale multi-center randomized trials are required to evaluate the long-term safety and efficacy of EPC therapy. Despite these hurdles, the outlook for EPC-based therapy for cardiovascular disease is promising.

Intraluminal Application of Vascular Endothelial Growth Factor Enhances Healing of Microvascular Anastomosis in a Rat Model

BACKGROUND

Early reconstitution after injury to the endothelium is an important feature for reducing a number of vessel wall pathologies. We investigated the effect of vascular endothelial growth factor (VEGF) and its impact on the vascular remodeling process and reendothelialization after microsurgery.

METHODS AND RESULTS

Microvascular anastomosis was performed in the rat femoral artery. One group was treated with intraluminal administration of VEGF and the other with vehicle. We investigated morphological, ultrastructural and immunohistochemical changes of the vascular wall and the reendothelialization process. After 10 days, reendothelialization was significantly faster in VEGF-treated rats. Transmission electron microscopy revealed a complete healing in contrast to vehicle-treated vessels. Moreover, extracellular matrix proteins, such as fibronectin, collagen types I, III and IV, were significantly increased. Furthermore, VEGF treatment significantly induced VEGF receptor 2, flk-1, osteopontin and TGF-beta(1) proteins.

CONCLUSIONS

Our data clearly document for the first time that intraluminal treatment with VEGF is beneficial to the healing process in vascular microsurgery. Osteopontin and TGF-beta(1), both induced by VEGF, may play an important role in the vascular remodeling process. Our results provide clear evidence that VEGF application may represent a useful strategy in accelerating reendothelialization and improving vascular healing after microsurgery.

Unresolved questions, changing definitions, and novel paradigms for defining endothelial progenitor cells

The field of vascular biology has been stimulated by the concept that circulating endothelial progenitor cells (EPCs) may play a role in neoangiogenesis (postnatal vasculogenesis). One problem for the field has been the difficulty in accurately defining an EPC. Likewise, circulating endothelial cells (CECs) are not well defined. The lack of a detailed understanding of the proliferative potential of EPCs and CECs has contributed to the controversy in identifying these cells and understanding their biology in vitro or in vivo. A novel paradigm using proliferative potential as one defining aspect of EPC biology suggests that a hierarchy of EPCs exists in human blood and blood vessels. The potential implications of this view in relation to current EPC definitions are discussed.

Impaired progenitor cell activity in age-related endothelial dysfunction

OBJECTIVES

We investigated whether human age-related endothelial dysfunction is accompanied by quantitative and qualitative alterations of the endothelial progenitor cell (EPC) pool.

BACKGROUND

Circulating progenitor cells with an endothelial phenotype contribute to the regeneration and repair of the vessel wall. An association between the loss of endothelial integrity and EPC modification may provide a background to study the mechanistic nature of such age-related vascular changes.

METHODS

In 20 old and young healthy individuals (61 +/- 2 years and 25 +/- 1 year, respectively) without major cardiovascular risk factors, endothelial function, defined by flow-mediated dilation of the brachial artery via ultrasound, as well as the number and function of EPCs isolated from peripheral blood, were determined.

RESULTS

Older subjects had significantly impaired endothelium-dependent dilation of brachial artery (flow-mediated dilation [FMD] 5.2 +/- 0.5% vs. 7.1 +/- 0.6%; p < 0.05). Endothelium-independent dilation after glycerol trinitrate (GTN) was not different, but the FMD/GTN ratio was significantly lower in old subjects (49 +/- 4% vs. 37 +/- 3%; p < 0.05), suggesting endothelial dysfunction. There were no differences in the numbers of circulating EPCs, defined as CD34/KDR or CD133/KDR double-positive cells in peripheral blood. In contrast, lower survival (39 +/- 6 cells/mm(2) vs. 65 +/- 11 cells/mm(2); p < 0.05), migration (80 +/- 12 vs. 157 +/- 16 cells/mm(2); p < 0.01), and proliferation (0.20 +/- 0.04 cpm vs. 0.44 +/- 0.07 cpm; p < 0.05) implicate functional impairment of EPCs from old subjects. The FMD correlated univariately with EPC migration (r = 0.52, p < 0.05) and EPC proliferation (r = 0.49, p < 0.05). Multivariate analysis showed that both functional features represent independent predictors of endothelial function.

CONCLUSIONS

Maintenance of vascular homeostasis by EPCs may be attenuated with age based on functional deficits rather than depletion of CD34/KDR or CD133/KDR cells.

Age-dependent VEGF expression and intraneural neovascularization during regeneration of peripheral nerves

The physiologic ability of peripheral nerves to regenerate after injury is impaired with aging. However, the mechanisms responsible for this phenomenon are still incompletely characterized. In this study, we investigated whether aging influences the intraneural angiogenic response that occurs after injury and during regeneration of peripheral nerves. We performed a crush injury of the sciatic nerve in old and senescence accelerated mice and found that the peripheral nerves of these animals are unable to locally upregulate vascular endothelial growth factor (VEGF), a prototypical angiogenic cytokine, after injury and have substantial deficits in mounting an appropriate intraneural angiogenic response during nerve regeneration. Our findings provide new evidence of possible interdependent relationships between aging, VEGF, angiogenesis, and nerve regeneration and suggest that vascular abnormalities might play a role in aging-associated neurological dysfunction, with potentially important fundamental and clinical implications.

Do changes in the mechanical properties of articular cartilage promote catabolic destruction of cartilage and osteoarthritis?

Osteoarthritis (OA) is a joint disease characterized by cartilage degeneration, a thickening of subchondral bone, and formation of marginal osteophytes. Previous mechanical characterization of cartilage in our laboratory suggests that energy storage and dissipation is reduced in osteoarthritis as the extent of fibrillation and fissure formation increases. It is not clear whether the loss of energy storage and dissipation characteristics is a result of biochemical and/or biophysical changes that occur to hyaline cartilage in joints. The purpose of this study is to present data, on the strain rate dependence of the elastic and viscous behaviors of cartilage, in order to further characterize changes that occur in the mechanical properties that are associated with OA. We have previously hypothesized that the changes seen in the mechanical properties of cartilage may be due to altered mechanochemical transduction by chondrocytes. Results of incremental tensile stress-strain tests at strain rates between 100%/min and 10,000%/min conducted on OA cartilage indicate that the slope of the elastic stress-strain curve increases with increasing strain rate, unlike the reported behavior of skin and self-assembled collagen fibers. It is suggested that the strain-rate dependence of the elastic stress-strain curve is due to the presence of large quantities of proteoglycans (PGs), which protect articular cartilage by increasing the apparent stiffness. The increased apparent stiffness of articular cartilage at high strain rates may limit the stresses borne and prolong the onset of OA. It is further hypothesized that increased compressive loading of chondrocytes in the intermediate zone of articular cartilage occurs as a result of normal wear to the superficial zone or from excessive impact loading. Once the superficial zone of articular cartilage is worn away, the tension is decreased throughout all cartilage zones leading to increased chondrocyte compressive loading and up-regulation of mechanochemical transduction processes that elaborate catabolic enzymes.

Vascular Endothelial Growth Factor Regulates Reendothelialization and Neointima Formation in a Mouse Model of Arterial Injury

Background— The rate of reendothelialization is critical in neointima formation after arterial injury. Vascular endothelial growth factor (VEGF), a potent endothelial mitogen, has been advocated for accelerating endothelial repair and preventing intimal hyperplasia after percutaneous coronary interventions. However, the precise mechanism of action of VEGF treatment and the physiologic role of endogenous VEGF after arterial injury are not well described. To better understand the role of VEGF in arterial repair, we overexpressed both VEGF and a soluble, chimeric VEGF receptor (VEGF-trap), which binds free VEGF with high affinity, in a mouse model of arterial injury.

Methods and Results— Four groups of C57BL/6 mice underwent denuding endothelial injury 1 day after systemic injection of recombinant adenovirus expressing (1) VEGF, (2) VEGF-trap, (3) VEGF plus VEGF-trap, or (4) control adenovirus. Circulating levels of adenovirus-encoded proteins were significantly elevated after gene transfer. VEGF overexpression accelerated reendothelialization and increased luminal endothelial cell proliferation 2 weeks after arterial injury ( P <0.05), resulting in decreased neointima formation at 4 weeks compared with control ( P <0.01). Cotreatment with VEGF-trap completely sequestered free VEGF and abrogated the beneficial effect of VEGF overexpression. Interestingly, sequestration of endogenous VEGF by VEGF-trap overexpression alone also led to delayed reendothelialization at 2 weeks ( P <0.01) and increased neointima formation at 4 weeks ( P <0.01).

Conclusions— VEGF overexpression accelerated endothelial repair and inhibited neointima formation after arterial injury. Conversely, sequestration of exogenous and/or endogenous VEGF by VEGF-trap delayed reendothelialization and significantly increased neointima size. This demonstrates the therapeutic potential of VEGF but also emphasizes the important physiologic role of endogenous VEGF in vascular repair.

Vascular repair by circulating endothelial progenitor cells: the missing link in atherosclerosis?

The integrity and functional activity of the endothelial monolayer play a crucial role in the prevention of atherosclerosis. Increasing evidence suggests that risk factors for coronary artery disease increase endothelial cell apoptosis and lead to a disturbance in the endothelial monolayer. Recent insights suggest that the injured endothelial monolayer is regenerated by circulating bone marrow derived endothelial progenitor cells, which accelerates reendothelialization and limits atherosclerotic lesion formation. However, risk factors for coronary artery disease such as age and diabetes reduce the number and functional activity of these circulating endothelial progenitor cells, thus limiting the regenerative capacity. The impairment of stem/progenitor cells by risk factors may contribute to atherogenesis and atherosclerotic disease progression. We discuss this novel concept of endothelial regeneration and highlight possible novel strategies to interfere with the balance of injury and repair mechanisms.

Age-dependent modifications of expression level of VEGF and its receptors in the inner ear

The mechanisms responsible for age-associated hearing loss are still incompletely characterized. In this study, we used a murine model of age-dependent hearing loss and evaluated whether this condition is associated with vascular modifications of the structures of the inner ear. We used old C57BL/6J mice that are affected by rapid and severe age-related hearing loss, and analyzed the expression pattern of vascular endothelial growth factor (VEGF), a prototypical angiogenic cytokine, and its receptors Flt-1 and Flk-1 in the inner ear. We report for the first time morphological and quantitative data about the expression of these crucial angiogenic molecules in the murine cochlea. We also show that in this animal model, cochlear VEGF expression is significantly reduced as a function of age. Our findings provide new evidence of possible interdependent relationships between aging, VEGF, and presbycusis, suggesting that vascular abnormalities might play a role in aging-associated hearing loss, with potentially important fundamental and clinical implications.

Effects of statins on endothelium and their contribution to neovascularization by mobilization of endothelial progenitor cells

Statins are potent drugs with a variety of cardiovascular protective effects which appear to occur independent of cholesterol reduction. The vasculoprotective effects of statins might be due to their direct effect on endothelial cells leading to improved nitric oxide (NO) bioavailability. Mechanistically, statins induce endothelial nitric oxide synthesis (eNOS) mRNA stability in endothelial cells and promote eNOS activity through a PI3K/Akt dependent pathway. Novel targets of statins are pro-angiogenic actions including the mobilization and differentiation of bone marrow derived endothelial progenitor cells, which accelerate angiogenesis or re-endothelialization. The functional improvement and increased homing capacity of endothelial progenitor cells induced by statin treatment might reverse impaired functional regeneration capacities seen in patients with risk factors for coronary artery disease or documented active coronary artery disease.

IQGAP1, a novel vascular endothelial growth factor receptor binding protein, is involved in reactive oxygen species--dependent endothelial migration and proliferation

Endothelial cell (EC) proliferation and migration are important for reendothelialization and angiogenesis. We have demonstrated that reactive oxygen species (ROS) derived from the small GTPase Rac1-dependent NAD(P)H oxidase are involved in vascular endothelial growth factor (VEGF)-mediated endothelial responses mainly through the VEGF type2 receptor (VEGFR2). Little is known about the underlying molecular mechanisms. IQGAP1 is a scaffolding protein that controls cellular motility and morphogenesis by interacting directly with cytoskeletal, cell adhesion, and small G proteins, including Rac1. In this study, we show that IQGAP1 is robustly expressed in ECs and binds to the VEGFR2. A pulldown assay using purified proteins demonstrates that IQGAP1 directly interacts with active VEGFR2. In cultured ECs, VEGF stimulation rapidly promotes recruitment of Rac1 to IQGAP1, which inducibly binds to VEGFR2 and which, in turn, is associated with tyrosine phosphorylation of IQGAP1. Endogenous IQGAP1 knockdown by siRNA shows that IQGAP1 is involved in VEGF-stimulated ROS production, Akt phosphorylation, endothelial migration, and proliferation. Wound assays reveal that IQGAP1 and phosphorylated VEGFR2 accumulate and colocalize at the leading edge in actively migrating ECs. Moreover, we found that IQGAP1 expression is dramatically increased in the VEGFR2-positive regenerating EC layer in balloon-injured rat carotid artery. These results suggest that IQGAP1 functions as a VEGFR2-associated scaffold protein to organize ROS-dependent VEGF signaling, thereby promoting EC migration and proliferation, which may contribute to repair and maintenance of the functional integrity of established blood vessels.