Translate this page to:
Choose Language…
In JoVE (1)
Other Publications (21)
- Stroke; a Journal of Cerebral Circulation
- Annals of Neurology
- Frontiers in Bioscience : a Journal and Virtual Library
- Stroke; a Journal of Cerebral Circulation
- Neurosurgery
- Neurochemistry International
- Journal of Cerebral Blood Flow and Metabolism : Official Journal of the International Society of Cerebral Blood Flow and Metabolism
- Neurochemistry International
- Journal of Cerebral Blood Flow and Metabolism : Official Journal of the International Society of Cerebral Blood Flow and Metabolism
- Brain Research
- Journal of Cerebral Blood Flow and Metabolism : Official Journal of the International Society of Cerebral Blood Flow and Metabolism
- Journal of Cerebral Blood Flow and Metabolism : Official Journal of the International Society of Cerebral Blood Flow and Metabolism
- Stroke; a Journal of Cerebral Circulation
- The American Journal of Pathology
- Cell Stem Cell
- Annals of Neurology
- Translational Stroke Research
- Annals of Neurology
- Neurobiology of Disease
- Journal of Cerebral Blood Flow and Metabolism : Official Journal of the International Society of Cerebral Blood Flow and Metabolism
- Translational Stroke Research
Articles by Fanxia Shen in JoVE
JoVE Neuroscience
Cerebrovascular Casting of the Adult Mouse for 3D Imaging and Morphological Analysis
1Center for Cerebrovascular Research, Department of Anesthesia and Perioperative Care, University of California, San Francisco, 2Department of Neurological Surgery, University of California, San Francisco, 3Department of Neurology, University of California, San Francisco
In this article, we present a simple, practical technique for cerebrovascular casting that is easy to perform and can be utilized to image the vascular tree of the adult mouse brain.
Other articles by Fanxia Shen on PubMed
Angiopoietin-2 Facilitates Vascular Endothelial Growth Factor-induced Angiogenesis in the Mature Mouse Brain
A better understanding of angiogenic factors and their effects on cerebral angiogenesis is necessary for the development of effective therapeutic strategies for ischemic brain injury. Vascular endothelial growth factor (VEGF) has been shown to induce angiogenesis in the adult mouse brain. However, the function of angiopoietin-2 (Ang-2) in cerebral angiogenesis has not been clarified. The goal of this study was to identify the combined effects of VEGF and Ang-2 on cerebral angiogenesis and the blood-brain barrier (BBB).
Interleukin-6 Involvement in Brain Arteriovenous Malformations
We recently reported that the GG genotype of the interleukin-6 (IL-6)-174G>C promoter polymorphism is associated with clinical presentation of intracranial hemorrhage in brain arteriovenous malformation (AVM) patients. In this study, we investigated whether tissue IL-6 expression was associated with IL-6-174G>C genotype, and whether IL-6 was linked to downstream targets involved in angiogenesis and vascular instability. Our results showed that the highest IL-6 protein levels in brain AVM tissue were associated with IL-6-174GG genotype (GG: 57.7 +/- 20.2; GC: 35.6 +/- 26.6; CC: 13.9 +/- 10.2pg/mg; p = 0.001). IL-6 protein levels were increased in AVM tissue from patients with hemorrhagic presentation compared with patients without hemorrhage (55 +/- 22 vs 40 +/- 27pg/mg; p = 0.038). IL-6 messenger RNA expression strongly correlated with messenger RNA levels of IL-1beta, tumor necrosis factor-alpha, IL-8, matrix metalloproteinase-3 (MMP-3), MMP-9, and MMP-12. We further investigated the plausibility of IL-6 being an upstream cytokine responsible for initiating the angiogenic cascade by cell culture and animal experiments. IL-6 induced MMP-3 and MMP-9 expression and activity in mouse brain and increased proliferation and migration of cerebral endothelial cells. Together, our results suggest that the IL-6 genotype associated with intracranial hemorrhage modulates IL-6 expression in brain AVM tissue, which is consistent with the hypothesis that inflammatory processes induce angiogenic activity possibly contributory to brain AVM intracranial hemorrhage.
Recombinant Adeno-associated Viral Vector Encoding Human VEGF165 Induces Neomicrovessel Formation in the Adult Mouse Brain
Delivery of therapeutic genes represents a fascinating possibility to accelerate injury-repairing process in tissues that are otherwise difficult to treat, such as cerebral ischemia. Current studies indicate that gene transfer-induced focal angiogenesis in the brain may provide an important therapeutic strategy. In the present study, we reported the efficacy of induction of angiogenesis with an adeno-associated virus (AAV) vector expressing the 165 amino acid isoform of vascular endothelial growth factor (VEGF165). We found AAV serotype 1 has more efficiency in transduction of the brain tissue than AAV serotype 2. Quantitative vessel counting showed that microvessels in AAV-VEGF transduced mice significantly increased from 1 week up to 12 weeks compared to the control groups (AAV-VEGF: 316+/-58 vs. AAV-lacZ: 180+/-34 and saline: 152+/-35 vessels/mm2, at 6 weeks, p<0.05). Proliferating cell nuclear antigen (PCNA) staining confirmed these microvessels were actively proliferating. Double-labeled fluorescence staining demonstrated that neurons, astrocytes, and endothelial cells could express VEGF following AAV-VEGF gene transfer. AAV vectors did not elicit a detectable inflammatory response, cell loss or neuronal damage. Our data underline the importance of angiogenesis in the brain tissue and indicate that VEGF gene transfer might present a valuable approach to treat brain ischemic disorders.
Adeno-associated Viral-vector-mediated Hypoxia-inducible Vascular Endothelial Growth Factor Gene Expression Attenuates Ischemic Brain Injury After Focal Cerebral Ischemia in Mice
Exogenous delivery of vascular endothelial growth factor gene (VEGF) may provide a useful approach to the treatment of brain ischemia. We investigated the use of a hypoxia-responsive element to control VEGF expression given for neuroprotection.
Expression of Hypoxia-inducible Factor-1 and Vascular Endothelial Growth Factor in Response to Venous Hypertension
Experimentally, a fistula created surgically between the carotid artery and jugular vein, together with occlusion of venous sinuses, generate venous hypertension, which can induce dural arteriovenous fistula formation intracranially in rats. Our aim was to study the effect of nonischemic venous hypertension on the elaboration of the angiogenic signal, hypoxia-inducible factor-1 (HIF-1), and its downstream signal, vascular endothelial growth factor (VEGF).
Comparison of Doxycycline and Minocycline in the Inhibition of VEGF-induced Smooth Muscle Cell Migration
Smooth muscle cell migration plays an important role during angiogenesis and vascular remodeling. In this study, we examined the effects of doxycycline and minocycline on vascular endothelial growth factor (VEGF)-induced human aortic smooth muscle cell (HASMCs) migration, and explored the mechanisms in which doxycycline or minocycline inhibit HASMC migration. We demonstrated that both doxycycline and minocycline attain consistent anti-angiogenic effects in the inhibition of HASMC migration via a different signal pathway (p<0.05). This effect is through attenuating VEGF-induced matrix metalloproteinase-9 (MMP-9) activity (p<0.05). Doxycycline could increase tissue inhibitors of metalloproteinases-1 (TIMP-1) expression while minocycline down-regulated PI3K/Akt phosphorylation in HASMC. Our study suggests that doxycycline has a stronger ability to inhibit MMP secretion in HASMC by up-regulating endogenous MMPs inhibitor TIMP-1, while minocycline implements anti-angiogenic effect through inhibiting HASMC migration by down-regulating PI3K/Akt pathway.
Interleukin-6 Stimulates Circulating Blood-derived Endothelial Progenitor Cell Angiogenesis in Vitro
Circulating blood endothelial progenitor cells (EPCs) contribute to postnatal vasculogenesis, providing a novel therapeutic target for vascular diseases. However, the molecular mechanism of EPC-induced vasculogenesis is unknown. Interleukin-6 plays multiple functions in angiogenesis and vascular remodeling. Our previous study demonstrated that the polymorphism (174G>C) in IL-6 gene promoter was associated with brain vascular disease. In this study, we investigated if IL-6 receptor is expressed in human EPCs derived from circulating mononuclear cells, and if interleukin-6 (IL-6) stimulates EPC angiogenesis in vitro. First, we isolated and cultured mononuclear cells from adult human circulating blood. We obtained EPC clones that were further cultured and expended for the angiogenesis study. We found that the EPCs possessed human mature endothelial cell phenotypes; however, they proliferated much faster than mature endothelial cells (P<0.05). We then found that IL-6 receptor (gp-80) was expressed in the EPCs, and that administration of IL-6 could activate receptor gp80/gp130 signaling pathways including downstream extracellular signal-regulated kinase 1/2 and STAT3 phosphorylation in EPCs. Furthermore, IL-6 stimulated EPC proliferation, migration, and matrigel tube formation in a dose-dependent manner (P<0.05); anti-IL-6 antibodies or IL-6 receptor could abolish these effects (P<0.05). These results suggest that IL-6 plays a crucial role in the biologic behavior of blood-derived EPCs, which may help clarify the mechanism of IL-6 inflammatory-related diseases.
Upregulation of EMMPRIN After Permanent Focal Cerebral Ischemia
Elevated activities of matrix metalloproteinases (MMPs) following ischemic stroke have been shown to mediate ischemic injury as well as neurovascular remodeling. The extracellular MMP inducer (EMMPRIN) is a 58-kDa cell surface glycoprotein, which has been known to play a key regulatory role for MMP activities. The roles of EMMPRIN in stroke injury are not clearly understood. In this study, we investigated changes of EMMPRIN in a mouse model of permanent focal cerebral ischemia, and examined potential association between EMMPRIN and MMP-9 expression. Adult male CD-1 mice were subjected to permanent focal ischemia by intraluminal occlusion of the left middle cerebral artery (MCAO) under anesthesia. EMMPRIN expression was markedly upregulated in the peri-infarct area at 2-7 days after ischemia compared to the contralateral non-ischemic hemisphere by Western blot analysis. Immunofluorescent double staining demonstrated that EMMPRIN signals co-localized with vwF-positive endothelial cells and GFAP-positive peri-vascular astrocytes. In contrast, EMMPRIN signal did not co-localize with NeuN-positive neurons, or MPO-positive neutrophils. Dual fluorescent staining revealed that EMMPRIN co-localized with MMP-9. Our data also demonstrated that increased EMMPRIN expression correlated with increased MMP-9 levels in a temporal manner. In summary, we report for the first time that EMMPRIN expression was significantly increased in a mouse model of permanent focal cerebral ischemia. The spatial and temporal association between increased EMMPRIN expression and elevated MMP-9 levels suggest that EMMPRIN may modulate MMP-9 activity, and participate in neurovascular remodeling after ischemic stroke.
Overexpression of Netrin-1 Induces Neovascularization in the Adult Mouse Brain
Netrin-1 is a critical molecule for axonal pathfinding during embryo development, and because of its structural homology to the endothelial mitogens, it may share its effects on vascular network formation. Using an adeno-associated viral netrin-1 vector (AAV-NT-1) gene transfer, we demonstrated that netrin-1 was able to stimulate the proliferation and migration of human cerebral endothelial cells (HCECs) and human aortic smooth muscle cells (HASMCs) compared with the control (P<0.05), and could also promote HCEC tube formation on matrigel (P<0.05) in vitro. Moreover, netrin-1 hyperstimulation could promote focal neovascularization (P<0.05) in the adult brain in vivo. Unlike VEGF-induced microvessel increase, netrin-1-induced newly formed vessels showed an artery-like phenotype, with an intact endothelial cell monolayer surrounded by multiple cell layers, including smooth muscle cells and an astrocyte-connected outer layer. Our findings suggest that netrin-1 plays an important role in promoting blood vessel formation in the adult rodent central nervous system, and could have broad implication in cerebrovascular development and remodeling.
Del-1 Gene Transfer Induces Cerebral Angiogenesis in Mice
Developmental endothelial locus-1 (Del-1) is a novel angiomatrix protein that has been shown to stimulate a potent angiogenic response and promote functional recovery in hind-limb and cardiac ischemia in animal models; however, its impact on cerebral angiogenesis is unknown. In this study, we investigated whether Del-1 overexpression via gene transfer induces cerebral angiogenesis in a murine model, and examined Del-1 expression after ischemic stroke. Cerebral Del-1 overexpression was achieved with AAV (adeno-associated virus) transduction system via stereotactic injection. Control mice were injected with AAV-lacZ. Del-1 gene transduction led to a significant induction of cerebral angiogenesis compared to AAV-lacZ treatment at 4 weeks after gene transfer (Del-1: 97+/-7 vs lacZ: 64+/-28, vessels/field, p<0.05). Mice transduced with AAV-Del-1 showed significantly elevated vascular densities for up to 6 weeks after gene delivery. In addition, double immunofluorescent staining showed co-localization of endothelial cell marker CD31 with BrdU (specific marker for proliferating cells), indicating that Del-1 promoted endogenous endothelial cell proliferation and angiogenesis. Our immunohistochemical staining also showed that Del-1 expression was markedly up-regulated in the peri-infarct area at 3 days after permanent focal cerebral ischemia compared to the sham-operated non-ischemic control. Our data suggest that Del-1 may participate in modulating cerebral angiogenesis, and that gene transfer of Del-1 may provide a novel and potent means for stimulating cerebral angiogenesis.
Nonischemic Cerebral Venous Hypertension Promotes a Pro-angiogenic Stage Through HIF-1 Downstream Genes and Leukocyte-derived MMP-9
Cerebral venous hypertension (VH) and angiogenesis are implicated in the pathogenesis of brain arteriovenous malformation and dural arteriovenous fistulae. We studied the association of VH and angiogenesis using a mouse brain VH model. Sixty mice underwent external jugular vein and common carotid artery (CCA) anastomosis (VH model), CCA ligation, or sham dissection (n=20). Hypoxia-inducible factor-1alpha (HIF-1alpha), vascular endothelial growth factor (VEGF) and stromal-cell-derived factor-1alpha (SDF-1alpha) expression, and matrix metalloproteinase (MMP) activity were analyzed. We found VH animals had higher (P<0.05) sagittal sinus pressure (8+/-1 mm Hg) than control groups (1+/-1 mm Hg). Surface cerebral blood flow and mean arterial pressure did not change. Hypoxia-inducible factor-1alpha, VEGF, and SDF-1alpha expression increased (P<0.05). Neutrophils and MMP-9 activity increased 10-fold 1 day after surgery, gradually decreased afterward, and returned to baseline 2 weeks after surgery. Macrophages began to increase 3 days after surgery (P<0.05), which coincided with the changes in SDF-1alpha expression. Capillary density in the parasagittal cortex increased 17% compared with the controls. Our findings suggest that mild nonischemic VH results in a pro-angiogenic stage in the brain by upregulating HIF-1 and its downstream targets, VEGF and SDF-1alpha, increasing leukocyte infiltration and MMP-9 activity.
Postischemic IGF-1 Gene Transfer Promotes Neurovascular Regeneration After Experimental Stroke
Promoting neural regeneration after cerebral infarction has emerged as a potential approach for the treatment of stroke. Insulin-like growth factor 1 (IGF-1) possesses both neurotrophic and angiogenic properties. The aim of this study was to determine whether postischemic gene transfer of IGF-1 enhances neurovascular regeneration in a mouse model of permanent focal cerebral ischemia. Long-term cerebral IGF-1 overexpression was achieved with adeno-associated viral vector (AAV) by stereotaxic injection at 24 h after a stroke. Adeno-associated viral vector-green fluorescent protein (GFP) or saline was injected as a control. The success of postischemic gene transduction was confirmed by a strong GFP signal and by increased IGF-1 protein expression in the peri-infarct region. Postischemic gene transfer of IGF-1 significantly enhanced vascular density at 8 weeks after a stroke in the peri-infarct and injection needle tract area compared with AAV-GFP or saline treatment, as shown by immunohistochemical staining with the vascular marker lectin. Furthermore, increased vascular density was associated with improved local vascular perfusion. Immunohistochemical staining with the neuronal progenitor marker, DCX (doublecortin), and the cell proliferation marker, BrdU (5-bromo-2-deoxyuridine-5-monophosphate), indicated that AAV-IGF-1 treatment potently increased neurogenesis compared with AAV-GFP injection. These data show that postischemic treatment of IGF-1 effectively promoted neural and vascular regeneration in the chronic stage of cerebral infarction.
Attenuation of Brain Response to Vascular Endothelial Growth Factor-mediated Angiogenesis and Neurogenesis in Aged Mice
Alterations of neuroangiogenic response play important roles in the development of aging-related neurodisorders and affect gene-based therapies. We tested brain response to vascular endothelial growth factor (VEGF) in aged mice.
Reduced Expression of Integrin Alphavbeta8 is Associated with Brain Arteriovenous Malformation Pathogenesis
Brain arteriovenous malformations (BAVMs) are a rare but potentially devastating hemorrhagic disease. Transforming growth factor-beta signaling is required for proper vessel development, and defective transforming growth factor-beta superfamily signaling has been implicated in BAVM pathogenesis. We hypothesized that expression of the transforming growth factor-beta activating integrin, alphavbeta8, is reduced in BAVMs and that decreased beta8 expression leads to defective neoangiogenesis. We determined that beta8 protein expression in perivascular astrocytes was reduced in human BAVM lesional tissue compared with controls and that the angiogenic response to focal vascular endothelial growth factor stimulation in adult mouse brains with local Cre-mediated deletion of itgb8 and smad4 led to vascular dysplasia in newly formed blood vessels. In addition, common genetic variants in ITGB8 were associated with BAVM susceptibility, and ITGB8 genotypes associated with increased risk of BAVMs correlated with decreased beta8 immunostaining in BAVM tissue. These three lines of evidence from human studies and a mouse model suggest that reduced expression of integrin beta8 may be involved in the pathogenesis of sporadic BAVMs.
MicroRNA-9 Coordinates Proliferation and Migration of Human Embryonic Stem Cell-derived Neural Progenitors
Human pluripotent stem cells offer promise for use in cell-based therapies for brain injury and diseases. However, their cellular behavior is poorly understood. Here we show that the expression of the brain-specific microRNA-9 (miR-9) is turned on in human neural progenitor cells (hNPCs) derived from human embryonic stem cells. Loss of miR-9 suppressed proliferation but promoted migration of hNPCs cultured in vitro. hNPCs without miR-9 activity also showed enhanced migration when transplanted into mouse embryonic brains or adult brains of a mouse model of stroke. These effects were not due to precocious differentiation of hNPCs. One of the key targets directly regulated by miR-9 encodes stathmin, which increases microtubule instability and whose expression in hNPCs correlates inversely with that of miR-9. Partial inhibition of stathmin activity suppressed the effects of miR-9 loss on proliferation and migration of human or embryonic rat neural progenitors. These results identify miR-9 as a novel regulator that coordinates the proliferation and migration of hNPCs.
Endothelial Progenitor Cell Transplantation Improves Long-term Stroke Outcome in Mice
Endothelial progenitor cells (EPCs) play an important role in tissue repairing and regeneration in ischemic organs, including the brain. However, the cause of EPC migration and the function of EPCs after ischemia are unclear. In this study, we demonstrated the effects of EPCs on ischemic brain injury in a mouse model of transient middle cerebral artery occlusion (tMCAO).
VEGF Induces More Severe Cerebrovascular Dysplasia in Endoglin Than in Alk1 Mice
Brain arteriovenous malformations (BAVMs) are an important cause of intracranial hemorrhage (ICH) in young adults. A small percent of BAVMs is due to hereditary hemorrhagic telangiectasia 1 and 2 (HHT1 and 2), which are caused by mutations in two genes involved in TGF-β signaling: endoglin (ENG) and activin-like kinase 1 (ALK1). The BAVM phenotype is an incomplete penetrant in HHT patients, and the mechanism is unknown. We tested the hypothesis that a "response-to-injury" triggers abnormal vascular (dysplasia) development, using Eng and Alk1 haploinsufficient mice. Adeno-associated virus (AAV) expressing vascular endothelial growth factor (VEGF) was used to mimic the injury conditions. VEGF overexpression caused a similar degree of angiogenesis in the brain of all groups, except that the cortex of Alk1(+/-) mice had a 33% higher capillary density than other groups. There were different levels of cerebrovascular dysplasia in haploinsufficient mice (Eng(+/)>Alk1(+/-)), which simulates the relative penetrance of BAVM in HHT patients (HHT1>HHT2). Few dysplastic capillaries were observed in AAV-LacZ-injected mice. Our data indicate that both angiogenic stimulation and genetic alteration are necessary for the development of dysplasia, suggesting that anti-angiogenic therapies might be adapted to slow the progression of the disease and decrease the risk of spontaneous ICH.
Arteriovenous Malformation in the Adult Mouse Brain Resembling the Human Disease
Brain arteriovenous malformations (bAVMs) are an important cause of hemorrhagic stroke. The underlying mechanisms are not clear. No animal model for adult bAVM is available for mechanistic exploration. Patients with hereditary hemorrhagic telangiectasia type 2 (HHT2) with activin receptor-like kinase 1 (ALK1; ACVRL1) mutations have a higher incidence of bAVM than the general population. We tested the hypothesis that vascular endothelial growth factor (VEGF) stimulation with regional homozygous deletion of Alk1 induces severe dysplasia in the adult mouse brain, akin to human bAVM.
AAV-mediated Netrin-1 Overexpression Increases Peri-infarct Blood Vessel Density and Improves Motor Function Recovery After Experimental Stroke
Apart from its role in axon guidance, netrin-1 is also known to be pro-angiogenic. The aim of this study is to determine whether adeno-associated viral (AAV) mediated overexpression of netrin-1 improves post-stroke neurovascular structure and recovery of function. AAV-Netrin-1 or AAV-LacZ of 1×10(10) genome copies each was injected medial and posterior to ischemic lesion at one hour following reperfusion using the distal middle cerebral artery occlusion (MCAO) method. Quantitative RT-PCR revealed that the expression of netrin-1 transgene began as early as one day and increased dramatically about 3 weeks following vector injection. Western blot analysis and confocal microscopy suggested that both the endogenous and transduced netrin-1 were expressed in the neurons of the peri-infarct cortex after MCAO. AAV-mediated netrin-1 overexpression significantly increased vascular density in the peri-infarct cortex and promoted the migration of immature neurons into the peri-infarct white matter, but it did not significantly reduce infarct size. Netrin-1 overexpression also enhanced post-stroke locomotor activity, improved exploratory behavior, and reduced ischemia-induced motor asymmetry in forelimb usage. However, it had little effect on post-stroke spatial learning and memory. Our results suggest that AAV mediated netrin-1 overexpression improves peri-infarct vascular density and post stroke motor function.
Coexpression of Angiopoietin-1 with VEGF Increases the Structural Integrity of the Blood-brain Barrier and Reduces Atrophy Volume
Vascular endothelial growth factor (VEGF)-induced neovasculature is immature and leaky. We tested if coexpression of angiopoietin-1 (ANG1) with VEGF improves blood-brain barrier (BBB) integrity and VEGF neuroprotective and neurorestorative effects using a permanent distal middle cerebral artery occlusion (pMCAO) model. Adult CD-1 mice were injected with 2 × 10(9) virus genomes of adeno-associated viral vectors expressing VEGF (AAV-VEGF) or ANG1 (AAV-ANG1) individually or together in a 1:1 ratio into the ischemic penumbra 1 hour after pMCAO. AAV-LacZ was used as vector control. Samples were collected 3 weeks later. Compared with AAV-LacZ, coinjection of AAV-VEGF and AAV-ANG1 reduced atrophy volume (46%, P=0.004); injection of AAV-VEGF or AAV-ANG1 individually reduced atrophy volume slightly (36%, P=0.08 and 33%, P=0.09, respectively). Overexpression of VEGF reduced tight junction protein expression and increased Evans blue extravasation. Compared with VEGF expression alone, coexpression of ANG1 with VEGF resulted in upregulation of tight junction protein expression and reduction of Evans blue leakage (AAV-ANG1/AAV-VEGF: 1.4 ± 0.3 versus AAV-VEGF: 2.8 ± 0.7, P=0.001). Coinjection of AAV-VEGF and AAV-ANG1 induced a similar degree of angiogenesis as injection of AAV-VEGF alone (P=0.85). Thus, coexpression of ANG1 with VEGF improved BBB integrity and resulted in better neuroprotection compared with VEGF expression alone.
Oligogenesis and Oligodendrocyte Progenitor Maturation Vary in Different Brain Regions and Partially Correlate with Local Angiogenesis After Ischemic Stroke
Oligogenesis plays an important role in functional recovery after ischemic stroke. We tested the hypothesis that oligogenesis and the maturation of oligodendrocyte progenitor cells (OPCs) vary in different brain regions using a rat transient middle cerebral artery occlusion (tMCAO) model. Compared to Day 1, olig2(+) OPCs and oligodendrocytes (OLGs) increased in the peri-infarct basal ganglia (BG) 7 (44%) and 14 (61%) days after 2 hours of MCAO; OPCs (PDGFRα(+)) and OLGs (CC1(+)) increased in this region 14 days after tMCAO by 139% and 126%, respectively. Although the olig2(+) cells and OLGs did not increase significantly in the peri-infarct cortex (CTX), the OPCs increased in this region by 95% at Day 14 vs. Day 1 after tMCAO. The numbers of OPCs and OLGs remained low after an initial reduction at Day 1 in the peri-infarct corpus callosum (CC). Correlation analyses showed that the numbers of olig2(+) cells (r=0.73, P=0.03) and OLGs (r=0.74, P=0.02) correlated with local vessel density; however, the number of OPCs did not correlate with vessel density (r=0.43, P=0.24). Our data show that oligogenesis and the maturation of OPCs differ in various brain regions and the difference in regional angiogenic response is one of the potential reasons.
