Early exercise improves cerebral blood flow through increased angiogenesis in experimental stroke rat model

Abstract

Background: Early exercise after stroke promoted angiogenesis and increased microvessles density. However, whether these newly formatted vessels indeed give rise to functional vascular and improve the cerebral blood flow (CBF) in impaired brain region is still unclear. The present study aimed to determine the effect of early exercise on angiogenesis and CBF in ischemic region.

Methods: Adult male Sprague Dawley rats were subjected to 90 min middle cerebral artery occlusion(MCAO)and randomly divided into early exercise and non-exercised control group 24 h later. Two weeks later, CBF in ischemic region was determined by laser speckle flowmetry(LSF). Meantime, micro vessels density, the expression of tie-2, total Akt and phosphorylated Akt (p-Akt), and infarct volume were detected with immunohistochemistry, 2,3,5 triphenyltetrazolium chloride (TTC) staining and western blotting respectively. The function was evaluated by seven point's method.

Results: Our results showed that CBF, vessel density and expression of Tie-2, p-Akt in ischemic region were higher in early exercise group compared with those in non-exercise group. Consistent with these results, rats in early exercise group had a significantly reduced infarct volume and better functional outcomes than those in non-exercise group.

Conclusions: Our results indicated that early exercise after MCAO improved the CBF in ischemic region, reduced infarct volume and promoted the functional outcomes, the underlying mechanism was correlated with angiogenesis in the ischemic cortex.

Figure 1

Schematic illustration of the experimental design. * represented the test points for laser speckle flowmetry (LSF). ** represented the test points for infarct volume, immunohistological staining (IH) and western blotting (WB). ^# represented the test points for neurological score (NS).

Figure 2

MCAO induced a markedly ischemia in impaired cortex. Above row there were the representative images of before and during MCAO, the bar graph showed the relative CBF (% of baseline).

Figure 3

Early exercise improved the CBF in ischemic cortex. A, Representative CBF pseudocolor images in ischemia cortex before, during and 14 days post MCAO. B, Quantification of the relative CBF in ROI (% of baseline for each animal). n = 6 for each group. *p<0.05, versus the no-exercise group; #, p<0.05, versus the sham group. Color bar represents the capacity of CBF. Abbreviations: ROI, region of interesting.

Figure 4

Early exercise promoted angiogenesis in ischemic cortex. In the early exercise group, intensive blood vessels (CD31⁺endothelial cells) were found in perilesional zone (C). In contrast, in non-exercised group (B), the density of micro vessels was much lower than the early exercise (C) and sham groups (A). The red dotted line indicated the infarct zone in upper left corner. (D) Quantification of the CD31⁺ cells showed that there was a significantly greater micro vessels density in the early exercise group. n = 6 for each group. *p<0.05, versus the no-exercise group; #, p<0.05, versus the sham group.

Figure 5

Early exercise increased expression of Tie-2 and p-AKT.A. Representative images of Western Blotting for Tie-2, p-AKT and GAPDH. B and C, Quantification of the optical density for Tie-2 and p-AKT, normalized to GAPDH. There was a significantly increased expression of Tie-2 and p-AKT in early exercise group. n = 6 for each group. *p<0.05, versus the no-exercise group; #, p<0.05, versus the sham group.

Figure 6

Early exercise reduced infarct volume induced by MCAO. A, Representative images of TTC stained section. B, Quantitation of the infarct volume showed that early exercise significantly reduced infarct volume after MCAO compared to non-exercise rats. n = 6 for each group. *p<0.05, versus the no-exercise group; #, p<0.05, versus the sham group.

Figure 7

Early exercise improved neurobehavioral recovery. MCAO caused a markedly neurological deficit, and early exercise reduced the neurological score at 7 day and 14 day after MCAO compared to non-exercise group. In contrast, rats in sham group performed no neurological deficit. n = 12 for each group. *p<0.05, versus the no-exercise group.