Study On Beneficial Effects Of Osteoglycin Deletion In Ischemia Induced Angiogenesis

Rationale–Osteoglycin(OGN)has been noted for implications in cardiovascular diseases in recent studies,particularly its correlation with left ventricular hypertrophy.However,the relationship between OGN and angiogenesis remains unknown.Objective–To investigate the effect of OGN on ischemia-induced angiogenesis and address the underlying mechanisms.Methods and Results–We observed OGN down-regulation in intermuscular endothelial cells of angiogenic tissues in patients with peripheral artery disease and mice ischemia model.OGN knockout(KO)mice were used in subsequent study.Both OGN KO mice and wild type(WT)mice received femoral artery.Histological assement and immuno cell stain did not differ from KO mice and WT ones.However,perfusion recovery rate after femoral artery ligation,assessed by Laser Doppler Imaging,was higher in OGN KO mice than in WT mice Capillary density was also higher in OGN KO mice in the gastrocnemicus muscle of the ischemia limb.Moreover,aortic rings isolated from OGN KO mice had stronger sprouting than those from WT ones.Tube formation was increased in human umbilical vein endothelial cells(HUVECs)with OGN knockdown,compared to the negative control(NC).Proliferation and migration were also enhanced in HUVECs with OGN knockdown.Further study revealed that OGN depletion significantly promoted the activation of vascular endothelial growth factor receptor 2(VEGFR2)and its downstream signaling pathways without affecting the protein level of vascular endothelial growth factor(VEGF)or VEGFR2.Co-immunoprecipitation assay revealed that OGN associated VEGFR2 and negatively modulated the interaction between VEGF and VEGFR2.In addition,elevated reactive oxygen species produced in HUVECs transfected OGN si RNA was observed.Real time polymerase chain reaction showed increased NAPDH oxidase(NOXs),especially NOX1 and NOX4,in HUVECs when OGN was suppressed.Immunohistochemistry confirmed this result in vivo,showing that NOX1 and NOX4 protein levels in OGN KO mice after ischemia were higher than those of WT ones.Furthermore,treatement of pan inhibitor of NOX,apocynin,reduced the agument of tube formation in OGN knockdown cells.Conclusions–OGN is an important negative regulator of VEGF-VEGFR2 signaling,EC proliferation and migration,and ischemia-induced angiogenesis.Its effects on oxidative stress may also contribute to enhanced angiogenesis.