Tatsuya Aonuma

Nerve growth factor stimulates regeneration of perivascular nerve, and induces the maturation of microvessels around the injured artery.

An immature vasa vasorum in the adventitia of arteries has been implicated in induction of the formation of unstable atherosclerotic plaques. Normalization/maturation of the vasa vasorum may be an attractive therapeutic approach for arteriosclerotic diseases. Nerve growth factor (NGF) is a pleotropic molecule with angiogenic activity in addition to neural growth effects. However, whether NGF affects the formation of microvessels in addition to innervation during pathological angiogenesis is unclear. In the present study, we show a new role for NGF in neovessels around injured arterial walls using a novel in vivo angiogenesis assay. The vasa vasorum around arterial walls was induced to grow using wire-mediated mouse femoral arterial injury. When collagen-coated tube (CCT) was placed beside the injured artery for 7-14 days, microvessels grew two-dimensionally in a thin layer on the CCT (CCT-membrane) in accordance with the development of the vasa vasorum. The perivascular nerve was found at not only arterioles but also capillaries in the CCT-membrane. Biodegradable hydrogels containing VEGF and NGF were applied around the injured artery/CCT. VEGF significantly increased the total length and instability of microvessels within the CCT-membrane. In contrast, NGF induced regeneration of the peripheral nerve around the microvessels and induced the maturation and stabilization of microvessels. In an ex vivo nerve-free angiogenesis assay, although NGF potentially stimulated vascular sprouting from aorta tissues, no effects of NGF on vascular maturation were observed. These data demonstrated that NGF had potent angiogenic effects on the microvessels around the injured artery, and especially induced the maturation/stabilization of microvessels in accordance with the regeneration of perivascular nerves.

Immortalized multipotent pericytes derived from the vasa vasorum in the injured vasculature. A cellular tool for studies of vascular remodeling and regeneration.

Adventitial microvessels, vasa vasorum in the vessel walls, have an active role in the vascular remodeling, although its mechanisms are still unclear. It has been reported that microvascular pericytes (PCs) possess mesenchymal plasticity. Therefore, microvessels would serve as a systemic reservoir of stem cells and contribute to the tissues remodeling. However, most aspects of the biology of multipotent PCs (mPCs), in particular of pathological microvessels are still obscure because of the lack of appropriate methods to detect and isolate these cells. In order to examine the characteristics of mPCs, we established immortalized cells residing in adventitial capillary growing at the injured vascular walls. We recently developed in vivo angiogenesis to observe adventitial microvessels using collagen-coated tube (CCT), which also can be used as an adventitial microvessel-rich tissue. By using the CCT, CD146- or NG2-positive cells were isolated from the adventitial microvessels in the injured arteries of mice harboring a temperature-sensitive SV40 T-antigen gene. Several capillary-derived endothelial cells (cECs) and PCs (cPCs) cell lines were established. cECs and cPCs maintain a number of key endothelial and PC features. Co-incubation of cPCs with cECs formed capillary-like structure in Matrigel. Three out of six cPC lines, termed capillary mPCs demonstrated both mesenchymal stem cell- and neuronal stem cell-like phenotypes, differentiating effectively into adipocytes, osteoblasts, as well as schwann cells. mPCs differentiated to ECs and PCs, and formed capillary-like structure on their own. Transplanted DsRed-expressing mPCs were resident in the capillary and muscle fibers and promoted angiogenesis and myogenesis in damaged skeletal muscle. Adventitial mPCs possess transdifferentiation potential with unique phenotypes, including the reconstitution of capillary-like structures. Their phenotype would contribute to the pathological angiogenesis associated with vascular remodeling. These cell lines also provide a reproducible cellular tool for high-throughput studies on angiogenesis, vascular remodeling, and regeneration as well.

Ninjurin1 Is a Novel Factor to Regulate Angiogenesis Through the Function of Pericytes

BACKGROUND Capillary pericytes (cPCs), the mural cells of microvessels, play an important role in the formation and maintenance of microvessels; however, little is known about the mechanisms of how cPCs regulate angiogenesis. To identify factors that modulate cPC function, genes whose levels were altered in cPCs during neovessel formation were identified through a microarray screen. METHODS AND RESULTS Ninjurin1 (nerve injury-induced protein, Ninj1) was selected as a candidate factor for angiogenesis regulation. Ninj1 was expressed in capillary cells including endothelial cells (cECs) and was expressed at a higher level in cPCs. Hypoxia induced the gene expression of Ninj1 in addition of vascular endothelial growth factor (VEGF) in cPCs. When cPCs were co-incubated with a thoracic aorta in a three-dimensional Matrigel system, the length of the EC-tubes sprouting from the aorta was increased. Small interfering RNA-mediated downregulation of Ninj1 in cPCs enhanced these cPCs-mediated angiogenic effects, whereas overexpression of Ninj1 attenuated their effects. The production of angiogenic growth factors, such as VEGF and angiopoietin 1, by cPCs was enhanced by the downregulation of Ninj1, and reduced by the overexpression of Ninj1. CONCLUSIONS Ninj1 is a novel regulator for the angiogenic effect of PCs. Specifically, Ninj1 negatively regulates the formation of neovessels, that is, the EC-tube, by reducing the trophic effects of cPCs.

Apoptosis‐Resistant Cardiac Progenitor Cells Modified With Apurinic/Apyrimidinic Endonuclease/Redox Factor 1 Gene Overexpression Regulate Cardiac Repair After Myocardial Infarction

Overcoming the insufficient survival of cell grafts is an essential objective in cell‐based therapy. Apurinic/apyrimidinic endonuclease/redox factor 1 (APE1) promotes cell survival and may enhance the therapeutic effect of engrafted cells. The aim of this study is to determine whether APE1 overexpression in cardiac progenitor cells (CPCs) could ameliorate the efficiency of cell‐based therapy. CPCs isolated from 8‐ to 10‐week‐old C57BL/6 mouse hearts were infected with retrovirus harboring APE1‐DsRed (APE1‐CPC) or a DsRed control (control‐CPC). Oxidative stress‐induced apoptosis was then assessed in APE1‐CPCs, control‐CPCs, and neonatal rat ventricular myocytes (NRVMs) cocultured with these CPCs. This analysis revealed that APE1 overexpression inhibited CPC apoptosis with activation of transforming growth factor β‐activated kinase 1 (TAK1) and nuclear factor (NF)‐κB. In the coculture model, NRVM apoptosis was inhibited to a greater extent in the presence of APE1‐CPCs compared with control‐CPCs. Moreover, the number of surviving DsRed‐positive CPC grafts was significantly higher 7 days after the transplant of APE1‐CPCs into a mouse myocardial infarction model, and the left ventricular ejection fraction showed greater improvement with attenuation of fibrosis 28 days after the transplant of APE1‐CPCs compared with control‐CPCs. Additionally, fewer inflammatory macrophages and a higher percentage of cardiac α‐sarcomeric actinin‐positive CPC‐grafts were observed in mice injected with APE1‐CPCs compared with control‐CPCs after 7 days. In conclusion, antiapoptotic APE1‐CPC graft, which increased TAK1‐NF‐κB pathway activation, survived effectively in the ischemic heart, restored cardiac function, and reduced cardiac inflammation and fibrosis. APE1 overexpression in CPCs may serve as a novel strategy to improve cardiac cell therapy.

Apurinic/apyrimidinic endonucelase 1 maintains adhesion of endothelial progenitor cells and reduces neointima formation

Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional protein that processes DNA-repair function and controls cellular response to oxidative stress. Endothelial progenitor cells (EPCs) are recruited to oxidative stress-rich injured vascular walls and positively contribute to vascular repair and endothelialization. We hypothesized that APE1 functions for EPCs-mediated inhibition of neointima formation in injured vasculature. EPCs isolated from bone marrow cells of C57BL6 mice (12-16 wk old) were able to survive in the presence of hydrogen peroxide (H2O2; up to 1,000 μM) due to the highly expressed reactive oxygen species (ROS) scavengers. However, adhesion capacity of EPCs was significantly inhibited by H2O2 (100 μM) even though an intracellular ROS was retained at small level. An APE1-selective inhibitor or RNA interference-mediated knockdown of endogenous APE1 in EPCs aggravated the H2O2-mediated inhibition of EPCs-adhesion. In contrast, when APE1 was overexpressed in EPCs using an adenovirus harboring the APE1 gene (APE-EPCs), adhesion was significantly improved during oxidative stress. To examine in vivo effects of APE1 in EPCs, APE-EPCs were transplanted via the tail vein after wire-mediated injury of the mouse femoral artery. The number of adherent EPCs at injured vascular walls and the vascular repair effect of EPCs were enhanced in APE-EPCs compared with control EPCs. Among the cellular functions of EPCs, adhesion is especially sensitive to oxidative stress. APE1 enhances in vivo vascular repair effects of EPCs in part through the maintenance of adhesion properties of EPCs. APE1 may be a novel and useful target gene for effective cellular transplantation therapy.

[PS 01-25] NINJURIN1 IS A NOVEL FACTOR TO MEDIATE VESSEL MATURATION THROUGH ENDOTHELIAL-PERICYTES INTERACTIONS

Objective : It is known that abnormality of adventitial microvessel (vasa vasorum) is involved in vascular remodeling and progression of atherosclerosis. Although the normalization/maturation of micorvessels is attractive approach for anti-atherosclerosis, the knowledge about the mechanisms for microvascular normalization is limited. Interaction of vascular endothelial cells (ECs) and pericytes (PCs) is crucial to vascular maturation. Recently, we have reported that Ninjrin1(Ninj1) in PCs inhibit ECs growth. However, the role of Ninj1 in patho-physiological angiogenesis is still unclear . Accordingly, we examined the effects of Ninj1on the formation of neovessels using mouse hind limb ischemia (HLI) model. Design and Method: Capillary ECs and PCs were prepared from adventitia of mouse femoral artery . Cell cluster or 3D-gel assay was performed by mixture of ECs and PCs in non-adherent or Matri-gel-coated wells. Knock down of Ninj1 in cells or tissues were induced by transfection of Ninj1-SiRNA or biodegradable microspheres releasing Ninj1-siRNA. Blood flow recovery and formation of microvessels in limbs were measured by Doppler flow meter and staining with anti-CD31 or lectin-FITC. Results: Ninj1 was expressed in microvessels, both dominantly PCs and ECs. Cell cluster assay demonstrated that down-regulation of Ninj1 in PCs or ECs reduced the PC-EC interaction. When ECs were co-incubated with PCs in 3D-gel, they made matured mirovessel structure, i.e. EC-tube wrapped with PCs. Down-regulation of Ninj1 in PCs or ECs reduced inhibited the formation of this matured vessel structure. Ninj1 was expressed in microvessels within skeletal muscle tissues, and their expression was enhanced after HLI operation. When the expression of Ninj1 was inhibited by intra-muscular injection of Ninj1-siRNA leads the formation of lectin/CD31-positive functional matured microvessels and the blood flow recovery was decreased. Conclusions: Ninj1 is important for the association between PCs and ECs to form functional matured vessels. This finding would provide insights into the therapy for atherosclerosis in addition to ischemic diseases.

Adult Accessory Mitral Valve with Septal Hypertrophy

A 28-year-old man visited our hospital due to atrial fibrillation, which spontaneously returned to normal sinus rhythm. Routine two-dimensional transthoracic echocardiography revealed marked septal hypertrophy and mitral valve anomaly, which caused left ventricular outflow tract (LVOT) stenosis, but could not clarify these anomalies in detail. Conversely, three-dimensional transesophageal echocardiography (3D-TEE) clearly showed the anomaly structure, which folded into the diastole and existed on the lateral portion of the acute myeloid leukemia (AML) (Picture A). These anomaly structures expanded during systole and the diameter at the bottom of the structures measured 22×21 mm. Bulging of part of the AML created a cavity without connection to the left atrium and overhung into the hypertrophic septum (Picture B). According to these pathognomonic findings of 3D-TEE, we finally diagnosed this anomaly as an isolated accessory mitral valve (AMV) with septal hypertrophy. An adult case of AMV with septal hypertrophy is very rare and surgical management of AMV patients remains controversial (1). In our case, the observed septum hypertrophy might be associated with a genetic cardiac inconsistency, such as hypertrophic cardiomyopathy (2). 3D-TEE clearly identifies AMV and can precisely assess AMV patients with complex anomalies.

Association between Microalbuminuria Predicting In-Stent Restenosis after Myocardial Infarction and Cellular Senescence of Endothelial Progenitor Cells

Objective Relationship between microalbuminuria and worse outcome of coronary artery disease patients is discussed, but its underlying pathophysiological mechanism remains unclear. We investigated the role of microalbuminuria to the function of endothelial progenitor cells (EPCs), that might affect to outcome of acute myocardial infarction (AMI) patients. Methods Forty-five AMI patients were divided into two groups according to their urinary albumin excretion: normal (n = 24) and microalbuminuria (>30 mg/day, n = 21). At day-2 and day-7 after AMI onset, circulating-EPCs (CD34+Flk1+) were quantified by flow cytometry. The number of lectin-acLDL-positive cultured-EPCs immobilized on fibronectin was determined. To assess the cellular senescence of cultured-EPCs, the expression level of sirtuin-1 mRNA and the number of SA-β-gal positive cell were evaluated. Angiographic late in-stent loss after percutaneous coronary intervention (PCI) was evaluated at a six-month follow-up. Results No significant differences in coronary risk and the extent of myocardial damage were observed between the two groups. Late in-stent loss at the six-month follow-up was significantly higher in the microalbuminuria group (normal : microalbuminuria = 0.76±0.34 : 1.18±0.57 mm, p=0.021). The number of circulating-EPCs was significantly increased in microalbuminuria group at day-7, however, improved adhesion of EPCs was observed in normal group but not in microalbuminuria group from baseline to day-7 (+3.1±8.3 : -1.3±4.4 %: p<0.05). On the other hand, in microalbuminuria group at day-7, the level of sirtuin-1 mRNA expression of cultured-EPCs was significantly decreased (7.1±8.9 : 2.5±3.7 fold, p<0.05), which was based on the negative correlation between the level of sirtuin-1 mRNA expression and the extent of microalbuminuria. The ratio of SA-β-gal-positive cells in microalbuminuria group was increased compared to that of normal group. Conclusions Microalbuminuria in AMI patients is closely associated with functional disorder of EPCs via cellular senescence, that predicts the aggravation of coronary remodeling after PCI.