N(epsilon)-(carboxymethyl)lysine proliferated CD34(+) cells from rat choroidal explant in culture

[Pharmacological Mechanisms of Boiogito and Bofutsushosan in Diabetes and Obesity Models]

　The antihyperglycemic activities of extracts of boiogito (BOT) and bofutsushosan (BTS) were investigated in streptozotocin-induced (STZ)-diabetic mice. BOT extract containing Stephania tetrandra S. MOORE root (stephania), has more potent antihyperglycemic activity than BOT extract containing sinomenium stem (sinomenium). Extracts of stephania and astragalus root (astragalus) exert combined effects in the antihyperglycemic and insulinotropic activities of BOT extract. Fangchinoline, but not tetrandrine, in stephania plays a role in its activity. Formononetin in astragalus potentiates the actions of fangchinoline. Tetrandrine has antiangiogenic effects on choroidal vessels in STZ-diabetic rats, which are associated with the inhibition of tumor necrosis factor (TNF)-α-induced nuclear factor (NF)-κB activation. BTS extract has shown antihyperglycemic and insulinotropic activities whereas gardenia fruit (gardenia) extract in BTS has antihyperglycemic, but not insulinotropic, activity in the diabetic mice. Gardenia extract decreased the HOMA-IR level and increased insulin-stimulated 2-deoxyglucose (2-DG) uptake to skeletal muscle. The effects of gardenia extract on 2-DG uptake were associated with the upregulation of glucose transporter type 4 and Akt phosphorylation. Gardenia extract was also shown to have antihyperglycemic and insulinotropic actions in high-fat diet (HFD)-fed and STZ-diabetic mice. In addition, gardenia extract decreased the production of TNF-α and leptin, and increased the production of adiponectin in the visceral adipose tissues. In the early administration period, BTS extract increased mRNA expression levels of leptin, adiponectin, and UCP1 in brown adipose tissues in HFD-fed obese mice. With a longer duration of administration, BTS extract improved insulin resistance and subsequently reduced serum leptin and triglyceride levels in parallel with visceral adipose tissue volume and size.

Injury-Mediated Vascular Regeneration Requires Endothelial ER71/ETV2

OBJECTIVE

Comprehensive understanding of the mechanisms regulating angiogenesis might provide new strategies for angiogenic therapies for treating diverse physiological and pathological ischemic conditions. The E-twenty six (ETS) factor Ets variant 2 (ETV2; aka Ets-related protein 71) is essential for the formation of hematopoietic and vascular systems. Despite its indispensable function in vessel development, ETV2 role in adult angiogenesis has not yet been addressed. We have therefore investigated the role of ETV2 in vascular regeneration.

APPROACH AND RESULTS

We used endothelial Etv2 conditional knockout mice and ischemic injury models to assess the role of ETV2 in vascular regeneration. Although Etv2 expression was not detectable under steady-state conditions, its expression was readily observed in endothelial cells after injury. Mice lacking endothelial Etv2 displayed impaired neovascularization in response to eye injury, wounding, or hindlimb ischemic injury. Lentiviral Etv2 expression in ischemic hindlimbs led to improved recovery of blood perfusion with enhanced vessel formation. After injury, fetal liver kinase 1 (Flk1), aka VEGFR2, expression and neovascularization were significantly upregulated by Etv2, whereas Flk1 expression and vascular endothelial growth factor response were significantly blunted in Etv2-deficient endothelial cells. Conversely, enforced Etv2 expression enhanced vascular endothelial growth factor-mediated endothelial sprouting from embryoid bodies. Lentiviral Flk1 expression rescued angiogenesis defects in endothelial Etv2 conditional knockout mice after hindlimb ischemic injury. Furthermore, Etv2(+/-); Flk1(+/-) double heterozygous mice displayed a more severe hindlimb ischemic injury response compared with Etv2(+/-) or Flk1(+/-) heterozygous mice, revealing an epistatic interaction between ETV2 and FLK1 in vascular regeneration.

CONCLUSIONS

Our study demonstrates a novel obligatory role for the ETV2 in postnatal vascular repair and regeneration.

Choroid sprouting assay: an ex vivo model of microvascular angiogenesis

Angiogenesis of the microvasculature is central to the etiology of many diseases including proliferative retinopathy, age-related macular degeneration and cancer. A mouse model of microvascular angiogenesis would be very valuable and enable access to a wide range of genetically manipulated tissues that closely approximate small blood vessel growth in vivo. Vascular endothelial cells cultured in vitro are widely used, however, isolating pure vascular murine endothelial cells is technically challenging. A microvascular mouse explant model that is robust, quantitative and can be reproduced without difficulty would overcome these limitations. Here we characterized and optimized for reproducibility an organotypic microvascular angiogenesis mouse and rat model from the choroid, a microvascular bed in the posterior of eye. The choroidal tissues from C57BL/6J and 129S6/SvEvTac mice and Sprague Dawley rats were isolated and incubated in Matrigel. Vascular sprouting was comparable between choroid samples obtained from different animals of the same genetic background. The sprouting area, normalized to controls, was highly reproducible between independent experiments. We developed a semi-automated macro in ImageJ software to allow for more efficient quantification of sprouting area. Isolated choroid explants responded to manipulation of the external environment while maintaining the local interactions of endothelial cells with neighboring cells, including pericytes and macrophages as evidenced by immunohistochemistry and fluorescence-activated cell sorting (FACS) analysis. This reproducible ex vivo angiogenesis assay can be used to evaluate angiogenic potential of pharmacologic compounds on microvessels and can take advantage of genetically manipulated mouse tissue for microvascular disease research.

Overproduction of N(epsilon)-(carboxymethyl)lysine-induced neovascularization in cultured choroidal explant of aged rat

N(epsilon)-(carboxymethyl)lysine (CML) adduct, a major structure of advanced glycation end product, facilitated production of immature microvessels from choroidal explant cultured in fibrin gel. The present study was investigated an action of endogenous CML adduct on neovascularization of cultured choroidal explants of aged Wistar rats with 9 months of age. The number of microvessels budded from explants was counted under optical microscope and used as an index of in vitro neovascularization. Aged choroidal explants increased the neovascularization in an age-dependent manner. Anti-CML antibody decreased age-facilitated neovascularization as well as CML-human serum albumin (HSA)-facilitated neovascularization. Both the aged explant and CML-HSA-treated explant significantly released vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF) alpha and platelet-derived growth factor (PDGF)-B during the culture period. The release of TNF alpha and PDGF-B was earlier than that of VEGF from the aged explants. The antibodies against these factors decreased the CML-facilitated and age-facilitated neovascularization in the choroidal explants. The inhibitory capacity of anti-TNF alpha antibody was greater than those of anti-VEGF and anti-PDGF-B antibodies. In conclusion, endogenous CML adduct overproduced the neovascularization of the aged choroidal explant. The CML adduct releases TNF alpha which might induce the production and release of VEGF for the abnormal choroidal neovascularization in the patients of age-related macular degeneration.

Inhibitory effect of nifedipine on tumor necrosis factor alpha-induced neovascularization in cultured choroidal explants of streptozotocin-diabetic rat

We have previously reported that the Nepsilon (carboxymethyl)lysine (CML) adduct, a major structure of an advanced glycation end product, facilitates proliferation of CD34+ endothelial progenitor cells budded from cultured choroidal explants and produces immature vessel-like structures in fibrin gel. The CML adduct is accumulated and facilitates immature neovascularization in cultured choroidal explants of streptozotocin (STZ)-induced diabetic rat. The CML-enhanced neovascularization activity is associated with the actions of tumor necrosis factor (TNF) alpha, vascular endothelial growth factor and platelet-derived growth factor released from the choroidal explant (Kobayashi et al., Biol. Pharm. Bull., 27, 1382-1387 (2004); 27, 1565-1571 (2004)). The present study was investigated an inhibitory effect of a dihydropyridine calcium antagonist nifedipine on TNF alpha-induced choroidal neovascularization in the STZ-diabetic rat. TNF alpha (1-100 ng/ml) increased neovascularization of cultured choroidal explants in the age-matched normal rat but did not increase it in the diabetic rat. Anti-TNF alpha antibody (1 : 1000) decreased the neovascularization in the diabetic rat but not in the normal rat. Nifedipine (1 microM) inhibited TNF alpha-induced neovascularization of the normal choroidal explant in a non-competitive manner. Nifedipine (1 microM) also inhibited the diabetic state-induced neovascularization and its inhibitory action was reversed by TNF alpha (1-10 ng/ml). In conclusion, STZ-diabetic state facilitated choroidal neovascularization through the release of TNF alpha. Nifedipine inhibited the action of TNF alpha probably by blocking voltage-dependent Ca2+ channels in the endothelial progenitor cells of the diabetic choroid.

Overproduction of N.EPSILON.-(Carboxymethyl)lysine-Induced Neovascularization in Cultured Choroidal Explant of Streptozotocin-Diabetic Rat

Action of N(epsilon)-(carboxymethyl)lysine (CML) adduct, an advanced glycation end product, was investigated on neovascularization of cultured choroidal explants in streptozotocin (STZ)-diabetic rat. The choroidal explants of early (4 weeks after an injection of 60 mg/kg STZ) and advanced (8 months after the STZ injection) diabetic rats, and age-matched normal rats were cultured in fibrin gel with Dulbecco's modified Eagle medium containing fetal bovine serum. The number of budded microvessel-like structures was counted and used as an index of in vitro neovascularization. Choroidal explants in the early diabetic stage released vascular endothelial growth factor (VEGF) and tended to increase tumor necrosis factor (TNF) alpha and platelet-derived growth factor (PDGF)-B, and concomitantly facilitated growth of sprout and buds, compared to the normal control. When choroidal explants were stimulated with CML-human serum albumin (HSA), its releasing effect was in the order VEGF>TNFalpha>PDGF-B. CML-HSA and CML-bovine serum albumin augmented the neovascularization in the cultured diabetic explant and their actions did not virtually differ. A monoclonal anti-CML antibody (6D12) inhibited the neovascularization in the advanced diabetes greater than that in the early diabetes. Inhibitory actions of anti-VEGF and anti-TNFalpha antibodies on the neovascularization were similar to that of the anti-CML antibody in the diabetes. In conclusion, CML adducts were accumulated and over-produced the actions of VEGF, TNFalpha and PDGF-B in the choroidal explant during diabetes in an age-dependent manner. TNFalpha and VEGF are likely to play a predominant role for the CML-induced choroidal neovascularization.