Enriched environment induces angiogenesis and improves neural function outcomes in rat stroke model

Abstract

Increasing evidence shows that exposure to an enriched environment (EE) after cerebral ischemia/reperfusion injury has neuroprotective benefits in animal models, including enhancing functional recovery after ischemic stroke. However, the mechanism underlying this effect remains unclear. To clarify this critical issue, the current study investigated the effects of EE on the improvement of damaged neural function and the induction of angiogenesis. Adult rats were subjected to ischemia induced by middle cerebral artery occlusion followed by reperfusion. Neurological status scores were used to evaluate neural function on postoperative days 2, 7, and 14. A beam-walking task was used to test the recovery of motor behavior on postoperative days 2, 5, 10, and 15. We also used a Morris water maze task to examine whether EE protected learning and memory performance. The specific marker of angiogenesis of CD31 was examined by western blot. Angiogenesis around the peri-infarction region was assayed by laser scanning confocal microscopy (LSCM) after 14 days of EE exposure starting 24h after ischemia. Neurological status scores of animals in the EE group were significantly higher than those in the standard housing condition (SC) control group from the seventh day after ischemic. EE accelerated the recovery of motor coordination and integration and also improved learning and memory performance after cerebral ischemia. Furthermore, EE increased CD31 levels and promoted angiogenesis of cortex in the peri-infarction region compared to the SC group. Neural function outcomes are positively correlated with post-ischemia angiogenesis. These findings suggest that EE plays an important role in the recovery of damaged neural function via regulation of angiogenesis after ischemia.

Keywords: Angiogenesis; CD31; Enriched environment; Ischemia; Neural function; Neuroprotection.