Poly(ADP-Ribose) Polymerase Inhibitor PJ34 Reduces Brain Damage after Stroke in the Neonatal Mouse Brain

The poly(ADP-ribose) polymerase inhibitor PJ34 has recently been reported to increase cerebral blood flow, via the endothelial NO synthase, in the naive mouse brain throughout life. We addressed here the benefits of PJ34 after neonatal ischemia on hemodynamics and components of the neurovascular unit including the blood-brain barrier (BBB), microglia, and astrocytes. Nine-day-old mice were subjected to permanent MCA occlusion (pMCAo), and treated with either PBS or PJ34 (10 mg/kg). Mean blood-flow velocities (mBFV) were measured in both internal carotid arteries (ICA) and basilar trunk (BT) using Doppler-ultrasonography. BBB opening was assessed through somatostatin-receptor type-2 internalization and immunohistochemistry at 24 and 48 h. Lesion areas were measured 8 days after ischemia. In PBS-treated mice, pMCAo involved a drop in mBFV in the left ICA (p < 0.001 vs. basal), whereas mBFV remained stable in both right ICA and BT. PJ34 prevented this drop in the left ICA (NS vs. basal) and increased mBFV in the right ICA (p = 0.0038 vs. basal). No modification was observed in the BT. In contrast to PBS, BBB disruption extent and astrocyte demise were reduced in PJ34 mice only in the rostral brain at 48 h and 8 days post-pMCAo, respectively. Accordingly, 8 days after pMCAo, affected areas were reduced in the rostral brain (Bregma +0.86 and +0.14 mm), whereas total tissue loss was not reduced after PJ34 (4.0 ± 3.1%) vs. PBS (5.8 ± 3.4%). These results show that PJ34 reduced BBB permeability, astrocyte demise, and tissue loss (particularly in the rostral territories), suggesting that collateral supply mainly proceeds from the anterior ICA’s branches in the ischemic neonatal mouse brain.

Acute Neonatal Upper Limb Ischemia: Topical Vasodilation, Anticoagulation and Physical Therapy-A new option for complete reversal of ischemia

Acute upper limb ischemia in neonates is extremely rare and oftenassociated with disastrous outcomes including digital gangrene, chroniclimb ischemia, sepsis and limb loss. It is usually seen in the contextof intra-arterial catheters in the preterm neonates but it can be alsoseen in cases of difficult or traumatic deliveries as well as in infantswith coagulation deficits but can also be spontaneous with no obviousaetiology. Treatment options include topical vasodilators, systemicanticoagulation and in some instances, surgical intervention. We reportthree cases of acute limb ischemia in preterm neonates in which anew treatment option was introduced. The neonates responded to acombination of topical nitro-glycerine cream, systemic anticoagulationwith heparin and physical light massaging of the area just proximalto the site of reduced flow in the vessel assuming some degree ofvasospasm of the vessel occurs with or without thrombosis.Keywords: neonatal ischemia, management of neonatal ischemia, topicalvasodilators, systemic anticoagulation, massage therapy, surgicalintervention

Early Sex Differences in the Immune-Inflammatory Responses to Neonatal Ischemic Stroke

We recently reported that neonatal ischemia induces microglia/macrophage activation three days post-ischemia. We also found that female mice sustained smaller infarcts than males three months post-ischemia. The objective of our current study was to examine whether differential acute neuroinflammatory response and infiltrated immune cells occurs between male and females after three days post-ischemia. Permanent middle cerebral artery occlusion was induced in male and female postnatal 9-day-old (P9) mice, and mice were sacrificed three days after ischemia. Brains were analyzed for mRNA transcription after microglia magnetic cell sorting to evaluate M1 and M2 markers. FACS analysis was performed to assess myeloid infiltration and microglial expression of CX3 chemokine receptor 1 (CX3CR1). Inflammatory cytokine expression and microglia/macrophage activation were analyzed via in situ hybridization combined with immunofluorescence techniques. Lesion volume and cell death were measured. An increase in microglia/macrophages occurred in male versus female mice. The cells exhibited amoeboid morphology, and TNFα and ptgs2 (Cox-2) genes were more expressed in males. More myeloid cell infiltration was found in male versus female brains. However, we did not observe sex-dependent differences in the injured volume or cell death density. Our data show that sex differences in the acute microglial and immune responses to neonatal ischemia are likely both gene- and region-specific.

Diffusion Tensor Imaging Abnormalities in the Cerebral White Matter Correlate with Sex-Dependent Neurobehavioral Deficits in Adult Mice with Neonatal Ischemia

Background: Neonatal white matter injury (NWMI) is the leading cause of cerebral palsy in prematurely born children. In order to develop a test bed for therapeutics, we recently reported a mouse model of NWMI by using a modified Rice-Vannucci model of neonatal ischemia on postnatal day 5 (P5) in CD-1 mice. We have previously shown that these mice illustrate initial neuroinflammation and oligodendroglial differentiation arrest followed by long-term dysmyelination, periventricular astrogliosis and axonal injury, resembling human NWMI. The objective of this study was to determine the sex-dependent long-term effects of neonatal brain injury on neurobehavioral and advanced in vivo neuroimaging indices in this mouse model, and to correlate these variables with histopathology. Methods: After right common artery ligation on P5, in vivo T2-weighted imaging and diffusion tensor imaging (DTI) were performed on ligated and control animals at 4 and 8 weeks. Common sets of regions of interest were used to compare fractional anisotropy (FA) values between ischemic and control mice. Behavioral testing (open field, startle response and grip strength) was performed at adult age. Finally, the animals were sacrificed for immunohistochemical (IHC) assessment of major white matter tracts. Results: DTI revealed significant sex-dependent changes in FA values ipsi- and contralateral to the ligation. Behavioral testing showed decreased reaction to acoustic stimuli in males but not females. Similarly, increased number of rearings and lack of novelty-induced habituation in the open field were encountered only in the male subgroup. Several regional correlations were found between FA values and these behavioral alterations. IHC studies revealed degeneration of mature oligodendrocytes and damage of white matter tracts in ligated animals, as previously reported in this model, and showed regional correlation with in vivo FA values and behavioral alterations. Conclusions: Our findings suggest structural sex-dependent long-term abnormalities after neonatal ischemia. These changes lead to behavioral deficits resembling common problems of patients with cerebral palsy.