Remote ischemic perconditioning is effective after embolic stroke in ovariectomized female mice

Abstract

Remote ischemic conditioning is neuroprotective in young male rodents after experimental stroke. However, it has never been tested in females whom remain at higher risk of stroke injury after menopause. We tested remote ischemic perconditioning therapy (RIPerC) at 2 h after embolic stroke in ovariectomized (OVX) female mice with and without intravenous tissue plasminogen activator (IV-tPA) treatment. We assessed cerebral blood flow (CBF), neurobehavioral outcomes, infarction, hemorrhage, edema, and survival. RIPerC therapy with and without IV-tPA improved the CBF and neurobehavioral outcomes and reduced the infarction, hemorrhage, and edema significantly. Late IV-tPA alone at 4 h post-stroke neither improved the neurobehavior nor reduced the infarction but aggravated hemorrhage and mortality in OVX mice. RIPerC therapy prevented the increased mortality during late IV-tPA. Our study demonstrates for the first time that RIPerC therapy is effective in OVX females.

Fig. 1

a CBF in the different groups measured by laser Doppler flowmeter (PeriFlux 5001) 0 and 6 h post-stroke. The LDF signal was recorded in the MCA territory of the ipsilateral hemisphere semi-continuously before (pre-ischemia) and after stroke. The absolute CBF value was obtained as an average of the values recorded over a period of 10 min at the required time points. The final data was calculated and presented as the percent of the pre-ischemic CBF value. Comparisons between the groups were done ‘within the time point’. All the data were expressed as mean ± SD (n = 6). Pairs of means with different letters are significantly different, p < 0.05. b Representative images of the cerebral perfusion in different groups as detected by laser Doppler perfusion imager (PeriScan PIM3 scanner 6 h post-stroke and 4 h after RIPerC therapy with and without IV-tPA. The values shown in the panels are as compared with their contralateral hemispheres

Fig. 2

Neurobehavioral and infarction assessments in surviving animals. a Sensorimotor function assessed by adhesive tape removal test at 18–20 h post-stroke and b neurological deficit score (NDS) as assessed on modified Bederson scale at 24 h post-stroke and before sacrifice. All the data were expressed as mean ± SD. c Representative TTC-stained coronal sections and d means of the corrected infarct volumes calculated as the percent of their corresponding contralateral sides. Data were expressed as mean ± SD (n = as denoted by the number of circles in A and B). Pairs of means with different letters are significantly different, p < 0.05

Fig. 3

a Representative coronal sections from each group showing hemorrhagic transformations and quantitation of Hb-content by spectrophotometry in the brain samples using Drabkin's reagent, and b estimation of edema volume by wet–dry method, at 24 h post-stroke. Data were expressed as mean ± SD (n = 6). Pairs of means with different letters are significantly different, p < 0.05