The diabetic state increases the activity but not the number of peritoneal macrophages in the GK rat promoting the tube formation of cultured endothelial cells in rat aorta

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

Action of N(epsilon)-(carboxymethyl)lysine-human serum albumin (CML-HSA) on neovascularization was investigated in cultured rat choroidal explant. Choroidal explants of normal male Wistar rats were cultured in fibrin gel with Dulbecco's modified Eagle medium containing fetal bovine serum in the presence or absence of CML-HSA. Migrated cells were budded from 2nd day in culture and developed from cultured choroidal explants in a time-dependent manner. Budded and developed cells from the choroidal explant had a feature of fibroblasts, which had attenuated long cytoplasmic processes, long ellipsoid nuclei and numerous membrane-bound polymorphic vesicles. Immunostaining of the attenuated cells in fibrin bed with CD34 (a marker protein of vascular endothelial cells and endothelial progenitor cells) failed to disclose positive result. However the cells which were isolated from fibrin bed by collagenase were specifically stained with anti-CD34 antibody. The isolated cells did not form tube-like structures on collagen gel by 3 weeks in culture. CML-HSA significantly increased the number of total isolated cells and CD34(+) cells as well as the number of vessel-like structures. These results indicate that CML-HSA overproduced immature blood vessels from cultured choroidal explants in fibrin gel, which consisted of CD34(+) cells. The CML-HSA-induced formation of immature blood vessel may be implicated in various choroidal diseases such as age-related macular degeneration.

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.

A quantitative assay for angiogenesis of cultured choroidal tissues in streptozotocin-diabetic Wistar and spontaneously diabetic GK rats

Angiogenesis of cultured choroids was quantitatively assayed in spontaneously diabetic GK and a bolus-treated streptozotocin (STZ)-diabetic Wistar rats. The number and total length of microvessels budded from cultured choroidal explants were measured to use as angiogenic indices. Both indices in 10-week-old Wistar rats were increased in parallel by 5% fetal bovine serum (FBS) from days 2 to 7 in culture. These indices in STZ-rats (10 weeks of age) were increased by 5% FBS to a greater extent than those in age-matched normal rats. These enhanced actions of FBS were concentration-dependent. The explants of 16-week-old GK rats also increased these indices to a greater extent than those of age-matched Wistar rats. Aging to 18 weeks of age also increased choroidal angiogenesis in the normal rats. In conclusion, the assay model of choroidal angiogenesis was established by determining the number and length of microvessels in cultured choroidal explants. The diabetic states of STZ-Wistar and GK rats enhanced FBS-induced choroidal angiogenesis. This assay model is useful for determining angiogenic activity of growth factors and effective drugs in diabetic choroidopathy and retinopathy.

Glycated serum stimulation of macrophages in GK- and streptozotocin-rats for the proliferation of primary cultured smooth muscle cells of the aorta

The purpose of this study was to investigate the actions of intraperitoneal macrophages and aortic endothelial cells (EC) as the cause of proliferation of primary cultured smooth muscle cells (SMC) of the aorta in non-insulin-dependent diabetes mellitus (NIDDM) models, including spontaneously diabetic GK and streptozotocin-diabetic Wistar rats. Conditioned medium derived from macrophages of GK rats increased proliferation of SMC in Wistar rats to a greater extent when compared to normal Wistar rats in conditioned medium. Serum of both GK rats and of Wistar rats which was previously exposed to 16.7 and 25 mM glucose (glycated serum) activated normal macrophages, enhancing SMC proliferation. However, glycated serum and high concentrations of glucose did not affect directly the proliferation of SMC. Conditioned medium from EC of streptozotocin-Wistar rats enhanced SMC proliferation. The enhancing activity of EC in diabetic rats was mimicked by conditioned medium from glycated EC but not from EC treated with the diabetic rat serum nor glycated bovine serum albumin. Cholesterol (39 microg/ml) potentiated the action of glycated serum on macrophages, but neither the action of normal macrophages nor the direct action of SMC was affected. Both the actions of glycated serum and cholesterol were inhibited by a polyclonal platelet-derived growth factor-BB antibody. However, low density lipoprotein (LDL), acetylated LDL and oxidized LDL (25 microg/ml) did not potentiate the action of glycated serum. These results demonstrate that glycated serum in the NIDDM model predominantly activated macrophages, resulting in proliferation of SMC by the release of platelet-derived growth factor-BB. Cholesterol potentiated the actions of glycated serum on macrophages.

Diabetic state-modified macrophages in GK rat release platelet-derived growth factor-BB for tube formation of endothelial cells in rat aorta

Cultured peritoneal macrophages (M phi) of GK rats, a non insulin-dependent diabetes mellitus model established from normal Wistar rats, increased the tube formation of aortic endothelial cells (EC). A polyclonal anti-platelet-derived growth factor (PDGF)-BB (0.21-3.3 micrograms/ml) inhibited (by 66.5 +/- 6.6%) the tube-forming activity of conditioned medium (CM) from M phi in diabetic GK rats, but not that in age-matched normal Wistar rats. A polyclonal anti-interleukin (IL)-1 alpha (0.16-0.33%) also inhibited (by 37.7 +/- 5.8%) the activity of diabetic M phi-CM, and its inhibitory effect was smaller than that of anti-PDGF-BB. A monoclonal anti-basic fibroblast growth factor (bFGF) (0.6-60 ng/ml) inhibited the activities of CM from both M phi, respectively. The tube-forming activity of the normal M phi-CM was increased by the serum isolated from the diabetic GK rat more than by that from the age-matched normal Wistar rat. The activity of normal M phi-CM was also increased by 16.7-50 mM glucose-exposed serum. These tube-forming activities of the CM of M phi stimulated by diabetic serum and by the high concentration of glucose-treated serum were completely inhibited by anti-PDGF-BB. In conclusion, PDGF-BB was selectively released from the diabetic state-modified M phi in the GK rat to increase tube formation, suggesting a key role in the cause of angiogenesis. The diabetic state-induced activation may depend on advanced glycosylation endproducts produced in the serum in the diabetic rat.