Netrin-1 Hyperexpression in Mouse Brain Promotes Angiogenesis and Long-Term Neurological Recovery After Transient Focal Ischemia

Abstract

Background and Purpose-Netrin-1 (NT-1) stimulates endothelial cell proliferation and migration in vitro and promotes focal neovascularization in the adult brain in vivo. This in vivo study in mice investigated the effect of NT-1 hyperexpression on focal angiogenesis and long-term functional outcome after transient middle cerebral artery occlusion (tMCAO). Methods-Adeno-associated viral vectors carrying either the NT-1 gene (AAV-NT-1) or GFP (AAV-GFP) were generated and injected into the brains of separate groups of 93 mice. Seven days later, tMCAO followed by 7-28 days of reperfusion were carried out. Histological outcomes and behavioral deficits were quantified 7-28 days after tMCAO. Small cerebral vessel network and angiogenesis were assessed 28 days after tMCAO, using synchrotron radiation microangiography and immunohistochemistry. Results-Western blot and immunohistochemistry showed that on the day of tMCAO, NT-1 hyperexpression had been achieved in both normal and ischemic hemispheres. Immunofluorescence imaging showed that NT-1 expression was primarily in neurons and astrocytes. Ischemia-induced infarction in the NT-1 hyperexpression group was attenuated in comparison to saline or AAV-GFP-treated groups (PϽ0.01). Similarly, neurological deficits were greatly improved in AAV-NT-1-treated mice compared with mice in saline or AAV-GFP-treated groups (PϽ0.05). In addition, angiogenesis was increased in AAV-NT-1-treated mice compared with the other 2 groups (PϽ0.05). In vivo synchrotron radiation microangiography 28 days after tMCAO revealed more branches in AAV-NT-1-treated mice than in other groups. Conclusions-AAV-NT-1 induced NT-1 hyperexpression before tMCAO reduced infarct size, enhanced neovascularization, and improved long-term functional recovery. (Stroke. 2012;43:838-843.)

The axon–glia unit in white matter stroke: Mechanisms of damage and recovery

“…The mechanism underlying the effect of Netrin-1 on OPC and oligodendrocytes involves signaling through the receptor Dcc, expressed by both cell types, and downstream inhibition of RhoA (Rajasekharan et al, 2009). Under pathological conditions, Netrin-1 inhibits inflammation and apoptosis, as well as promotes repair after ischemic stroke by increasing angiogenesis (Lu et al, 2012; Rosenberger et al, 2009; Sun et al, 2011). Overexpression of Netrin-1 increases proliferation and differentiation of OPC into mature oligodendrocytes, and promotes white matter remyelination and neurobehavioral outcomes after focal cerebral ischemia in mice (He et al, 2013).…”

Axon guidance factor netrin-1 and its receptors regulate angiogenesis after cerebral ischemia

“…Lu et al [74] found that netrin-1 overexpression contributes to functional recovery by diminishing the infarct size and promoting angiogenesis after mouse tMCAO.…”

Netrin-1 Overexpression Promotes White Matter Repairing and Remodeling after Focal Cerebral Ischemia in Mice

“…Transient middle cerebral artery occlusion was performed as previously described. 15 Briefly, a 6-0 silicone-coated suture (Covidien, Mansfield, MA, USA) was inserted from the left external carotid artery into the internal carotid artery to occlude the origin of the middle cerebral artery. Successful occlusion was demonstrated by the decrease of surface cerebral blood flow to 10% of baseline cerebral blood flow using a Laser Doppler flowmetry (Moor LAB, Devon, UK).…”

“…It inhibits inflammation and apoptosis and promotes repairing after ischemic stroke by increasing angiogenesis. [12][13][14][15] However, the effect of NT-1 on white matter repairing after ischemic brain injury has not been explored yet. In the present study, we aim to investigate whether NT-1 overexpression could improve white matter repairing and remodeling after ischemic stroke, and if so, the possible role of NT-1 will be further studied.…”