Laser speckle contrast imaging for blood flow monitoring in predicting outcomes after cerebral ischemia-reperfusion injury in mice

Abstract

Background: In the treatment of ischemic cerebral stroke (ICS), most conventional treatments, including carotid endarterectomy and carotid artery stenting, may cause cerebral ischemia-reperfusion injury (CIRI). For treated ICS patients, changes in cerebral blood flow are directly related to brain function. At present, computed tomography perfusion, dynamic susceptibility contrast-enhanced perfusion weighted imaging and magnetic resonance arterial spin labeling perfusion imaging are used to monitor cerebral blood flow, but they still have some limitations. Our study aimed to monitor the changes in cerebral cortical blood flow by laser speckle contrast imaging (LSCI) in CIRI model mice and to propose a new method for predicting outcomes after CIRI. C57BL/6 N mice were used to establish a mouse CIRI model based on a modified thread-occlusion method and divided into a good outcome group and a poor outcome group according to survival within 7 days. The cerebral cortical blood flow of the area supplied by the left middle cerebral artery was monitored by LSCI at baseline (before modeling), 1 h after ischemia, immediately after reperfusion and 24 h after reperfusion. Then, the brains of the mice were removed immediately and stained with hematoxylin and eosin to observe the pathological changes in brain neurons.

Results: The cerebral cortical blood flow in the poor outcome group was obviously reduced compared with that less in the good outcome group at 24 h after reperfusion (180.8 ± 20.9 vs. 113.9 ± 6.4, p = 0.001), and at 24 h after reperfusion, the cerebral cortical blood flow was negatively correlated with the severity of brain tissue injury (p = - 0.710, p = 0.010).

Conclusions: LSCI can monitor the changes in cerebral cortical blood flow during CIRI in mice and could be used as a feasible method for predicting outcomes after CIRI in mice.

Keywords: Brain tissue injury; Cerebral blood flow; Cerebral ischemia-reperfusion injury; Laser speckle contrast imaging; Outcome prediction.

Fig. 1

Representative LSCI imaging of cerebral cortical blood flow monitoring at different time points in the (a) sham group, (b) good outcome group and (c) poor outcome group. The blood flow in the area supplied by the left MCA in the good outcome group was greater than that in the poor outcome group at 24 h after reperfusion. LSCI laser speckle contrast imaging, MCA middle cerebral artery

Fig. 2

HE staining of brain tissues. a Normal tissue: intact nuclei of brain neurons with clear cell membrane; b mild injury: cell swelling with disordered arrangement and interstitial edema; c severe injury: a large number of necrotic cells and severe damage to the tissue structure. Green boxes indicated the damaged areas, and red arrows indicated swollen and necrotic cells. HE Hematoxylin and eosin. (Magnifcation: 400x; measured resolution at acquisition: 96 dpi; enhanced resolution for publication by Adobe Photoshop CS6 version 13.0: 300 dpi)

Fig. 3

Relationships between cerebral cortical blood flow monitored by LSCI and the degree of brain tissue injury. The lower the cerebral blood flow value was, the more severe the degree of brain tissue injury was. LSCI laser speckle contrast imaging