A Protocol for Characterizing the Impact of Collateral Flow after Distal Middle Cerebral Artery Occlusion

Abstract

I. SUMMARYIn humans and in animal models of stroke, collateral blood flow between territories of the major pial arteries has a profound impact on cortical infarct size. However, there is a gap in our understanding of the genetic determinants of collateral formation and flow, as well as the signaling pathways and neurovascular interactions regulating this flow. Previous studies have demonstrated that collateral flow between branches of the anterior cerebral artery (ACA) and the middle cerebral artery (MCA) can protect mouse cortex from infarction after middle cerebral artery occlusion. Because the number and diameter of collaterals varies among mouse strains and after transgenic manipulations, a combination of methods is required to control for these variations. Here, we report an inexpensive approach to characterizing the cerebrovascular anatomy, and in vivo monitoring of cerebral blood flow as well. Further, we introduce a new, minimally invasive method for the occlusion of distal MCA branches. These methods will permit a new generation of studies on the mechanisms regulating collateral remodeling and cortical blood flow after stroke. II.

Temporal remodeling of pial collaterals and functional deficits in a murine model of ischemic stroke

“…Our method provides detailed morphological and histological changes occurring in the pial collateral network, after surgically inducing stroke in the brain, and selectively labeling the arterial vasculature using a vessel painting technique. Using a combination of methods, our findings illustrate the stepwise changes in collateral growth following (Defazio et al, 2011; Okyere et al, 2016) and quantify changes occurring in individual dorsal pial collateral vessels including cell proliferation, smooth muscle cell reorganization and recruitment of Cx3cr1GFP-expressing peripheral-derived immune cells (Defazio et al, 2011; Okyere et al, 2016). We also describe the longitudinal relationship between these structural alterations and cerebral blood flow as well as behavioral deficiencies in the pMCAO model.…”

“…Vessel painting on adult CD1 mice was performed as previously described (Defazio et al, 2011; Okyere et al, 2016). Briefly, mice were injected with heparin (2000 units/kg), and sodium nitroprus-side (SNP, 0.75 mg/kg) five minutes prior to euthanization, using an overdose of isoflurane.…”

“…In vivo imaging techniques, such as optical coherence tomography, two-photon microscopy and laser speckle imaging have been used to observe collateral reperfusion and remodeling in pathological states (Schaffer et al, 2006; Defazio et al, 2011; Defazio et al, 2012; Li et al, 2016). Such methods are particularly useful for non-invasive, longitudinal assessment of collateral function with high resolution.…”

Brief update on hemodynamic responses in animal models of neonatal stroke and hypoxia–ischemia

“…LSC and laser Doppler reflect red blood-cell velocity within microvessels as a measure of tissue perfusion in the brain surface. A protocol for characterizing the impact of collateral flow after distal permanent MCA occlusion in the adult mouse has been reported and demonstrated high and low collateral density in C57BL/6J and BALB/c mouse, respectively (Defazio et al, 2011). They also showed that collateral flow magnitude determines infarct volume and that a single collateral vessel may be sufficient to rescue the territory of a distal MCA branch (Defazio et al, 2011).…”

“…A protocol for characterizing the impact of collateral flow after distal permanent MCA occlusion in the adult mouse has been reported and demonstrated high and low collateral density in C57BL/6J and BALB/c mouse, respectively (Defazio et al, 2011). They also showed that collateral flow magnitude determines infarct volume and that a single collateral vessel may be sufficient to rescue the territory of a distal MCA branch (Defazio et al, 2011). The relative good reproducibility in infarct volume reported in the MCAo model in P12 CB-17 mouse reinforces previous data suggesting that the CB-17 strain exhibits little variation in the cerebral vascular structure (Taguchi et al, 2010).…”