Induction of angiogenesis related genes in the contralateral cortex with a rat three-vessel occlusion model

The bFGF/FGFR, VEGF/VEGFR and Angiopoietin/Tie receptor system are crucial for angiogenesis and vascular remodeling. With a rat focal cerebral ischemia model, we previously reported dramatic changes in the vascular density and angiogenesis related genes in the ipsilateral cortex after 60 minutes severe ischemia. While only a small increase in the capillary density was noted in the contralateral cortex with very mild ischemia. In the present study we further reported that only Tie-1 and VEGFR-2 mRNA were significantly changed in the contralateral cortex with a p value of 0.0001 and 0.0168, respectively, and the degree of changes were very small. Interestingly, in contrast to a huge increase in the ipsilateral cortex, Tie-1 mRNA was slowly decreased after the onset of ischemia and stayed below the basal level throughout the remaining periods studied. The mechanism and significance for this decrease is not presently clear. In contrast to the ipsilateral cortex, the Angpo-1/Angpo-2 mRNA ratio was also slightly dropped below the basal level in the contralateral side in most of the ischemia-reperfusion periods studied, which is in line with the notion that small decrease in Angpo-1/Angpo-2 mRNA ratio implied small vascular remodeling activity. It is very likely that increase in this Angpo-1/Angpo-2 ratio is crucial for remodeling into large vessels and increase in Tie-1 may be crucial for capillary density increasing. Nevertheless, the detailed mechanisms and significance of differential expression of these genes and relationship to vascular remodeling remain to be characterized.