We have previously shown that diabetes causes dysfunctional cerebral neovascularization that increases the risk for cerebrovascular disorders such as stroke and cognitive impairment. Pericytes (PC) play a pivotal role in the angiogenic process through interaction with endothelial cells (EC). Yet, the role of PCs in dysfunctional cerebral neovascularization in diabetes is unclear. In the present study, we tested the hypothesis that the increased proangiogenic EphrinB2 signaling in PCs contributes to the dysfunctional cerebral neovascularization in diabetes.
Methods: Type-II diabetes was induced in Wistar rats. Conditional reduction of EphrinB2 expression in rat brain PCs was achieved using stereotactic injection of AAV-virus with NG2-promoter that expresses EphrinB2 shRNA. Neovascularization was assessed using fluorescent space filling model. Novel object recognition (NOR) test was used to assess cognitive functions. Human brain microvascular PCs were grown in glucose 25 mM/palmitate 200 uM (HG/Pal) to mimic diabetic conditions. PC/EC co-culture was used to assess PC/EC interaction and angiogenic functions (scratch migration and tube formation).
Results: Diabetes increased expression of EphrinB2 in the cerebrovasculature (2.2-Fold*) and pericytes (1.4 fold*). Diabetes significantly increased cerebral vascularization (Vascular density 3.1 fold*, tortuosity 1.07 fold* and branching density 1.5 fold*) in Wistar rats that were accompanied by deterioration of cognitive function (40% reduction*). Inhibition of EphrinB2 expression in PC significantly restored cerebral vascularization indices back to normal and improved rat cognitive functions with higher D-2 scores in NOR compared to diabetic rats*. HG/Pal increased PC/EC angiogenic properties in coculture (2-fold*). Silencing Ephrin-B2 in HBMVP significantly reduced PC migration (35 %*) and PC/EC co-culture angiogenic properties. (*p<0.05).
Conclusion: Our findings emphasize the crucial role that PC plays in the pathological neovascularization in diabetes. EphrinB2 signaling is a promising therapeutic target to improve cerebrovascular integrity in diabetes. Yet, the molecular mechanism of the EphrinB2 signaling in PC/EC interaction is to be uncovered.