Protein-energy malnutrition (PEM) is a common post-stroke problem. PEM can independently induce a systemic acute-phase response, and pre-existing malnutrition can exacerbate neuroinflammation induced by brain ischemia. In contrast, the effects of PEM developing in the post-ischemic period have not been studied. Since excessive inflammation can impede brain remodeling, we investigated the effects of post-ischemic malnutrition on neuroinflammation, the acute-phase reaction, and neuroplasticity-related proteins. Male, Sprague-Dawley rats were exposed to global forebrain ischemia using the 2-vessel occlusion model or sham surgery. The sham rats were assigned to control diet (18% protein) on day 3 after surgery, whereas the rats exposed to global ischemia were assigned to either control diet or a low protein (PEM, 2% protein) diet. Post-ischemic PEM decreased growth associated protein-43, synaptophysin and synaptosomal-associated protein-25 immunofluorescence within the hippocampal CA3 mossy fiber terminals on day 21, whereas the glial response in the hippocampal CA1 and CA3 subregions was unaltered by PEM. No systemic acute-phase reaction attributable to global ischemia was detected in control diet-fed rats, as reflected by serum concentrations of alpha-2-macroglobulin, alpha-1-acid glycoprotein, haptoglobin, and albumin. Acute exposure to the PEM regimen after global brain ischemia caused an atypical acute-phase response. PEM decreased the serum concentrations of albumin and haptoglobin on day 5, with the decreases sustained to day 21. Serum alpha-2-macroglobulin concentrations were significantly higher in malnourished rats on day 21. This provides the first direct evidence that PEM developing after brain ischemia exerts wide-ranging effects on mechanisms important to stroke recovery.
Following spinal cord injury (SCI) there are drastic changes that occur in the spinal microvasculature, including ischemia, hemorrhage, endothelial cell death and blood-spinal cord barrier disruption. Vascular endothelial growth factor-A (VEGF-A) is a pleiotropic factor recognized for its pro-angiogenic properties; however, VEGF has recently been shown to provide neuroprotection. We hypothesized that delivery of AdV-ZFP-VEGF--an adenovirally delivered bio-engineered zinc-finger transcription factor that promotes endogenous VEGF-A expression--would result in angiogenesis, neuroprotection and functional recovery following SCI. This novel VEGF gene therapy induces the endogenous production of multiple VEGF-A isoforms; a critical factor for proper vascular development and repair. Briefly, female Wistar rats--under cyclosporin immunosuppression--received a 35 g clip-compression injury and were administered AdV-ZFP-VEGF or AdV-eGFP at 24 hours post-SCI. qRT-PCR and Western Blot analysis of VEGF-A mRNA and protein, showed significant increases in VEGF-A expression in AdV-ZFP-VEGF treated animals (p<0.001 and p<0.05, respectively). Analysis of NF200, TUNEL, and RECA-1 indicated that AdV-ZFP-VEGF increased axonal preservation (p<0.05), reduced cell death (p<0.01), and increased blood vessels (p<0.01), respectively. Moreover, AdV-ZFP-VEGF resulted in a 10% increase in blood vessel proliferation (p<0.001). Catwalk™ analysis showed AdV-ZFP-VEGF treatment dramatically improves hindlimb weight support (p<0.05) and increases hindlimb swing speed (p<0.02) when compared to control animals. Finally, AdV-ZFP-VEGF administration provided a significant reduction in allodynia (p<0.01). Overall, the results of this study indicate that AdV-ZFP-VEGF administration can be delivered in a clinically relevant time-window following SCI (24 hours) and provide significant molecular and functional benefits.
In vivo and direct imaging of the murine spinal cord and its vasculature using multimodal (optical and acoustic) imaging techniques could significantly advance preclinical studies of the spinal cord. Such intrinsically high resolution and complementary imaging technologies could provide a powerful means of quantitatively monitoring changes in anatomy, structure, physiology and function of the living cord over time after traumatic injury, onset of disease, or therapeutic intervention. However, longitudinal in vivo imaging of the intact spinal cord in rodent models has been challenging, requiring repeated surgeries to expose the cord for imaging or sacrifice of animals at various time points for ex vivo tissue analysis. To address these limitations, we have developed an implantable spinal cord window chamber (SCWC) device and procedures in mice for repeated multimodal intravital microscopic imaging of the cord and its vasculature in situ. We present methodology for using our SCWC to achieve spatially co-registered optical-acoustic imaging performed serially for up to four weeks, without damaging the cord or induction of locomotor deficits in implanted animals. To demonstrate the feasibility, we used the SCWC model to study the response of the normal spinal cord vasculature to ionizing radiation over time using white light and fluorescence microscopy combined with optical coherence tomography (OCT) in vivo. In vivo power Doppler ultrasound and photoacoustics were used to directly visualize the cord and vascular structures and to measure hemoglobin oxygen saturation through the complete spinal cord, respectively. The model was also used for intravital imaging of spinal micrometastases resulting from primary brain tumor using fluorescence and bioluminescence imaging. Our SCWC model overcomes previous in vivo imaging challenges, and our data provide evidence of the broader utility of hybridized optical-acoustic imaging methods for obtaining multiparametric and rich imaging data sets, including over extended periods, for preclinical in vivo spinal cord research.
Spinal cord injury (SCI) leads to local vascular disruption and progressive ischemia, which contribute to secondary degeneration. Enhancing angiogenesis through the induction of vascular endothelial growth factor (VEGF)-A expression therefore constitutes an attractive therapeutic approach. Moreover, emerging evidence suggests that VEGF-A may also exhibit neurotrophic, neuroprotective, and neuroproliferative effects. Building on this previous work, we seek to examine the potential therapeutic benefits of an engineered zinc finger protein (ZFP) transcription factor designed to activate expression of all isoforms of endogenous VEGF-A (ZFP-VEGF). Administration of ZFP-VEGF resulted in increased VEGF-A mRNA and protein levels, an attenuation of axonal degradation, a significant increase in vascularity and decreased levels of apoptosis. Furthermore, ZFP-VEGF treated animals showed significant improvements in tissue preservation and neurobehavioural outcomes. These data suggest that activation of VEGF-A via the administration of an engineered ZFP transcription factor holds promise as a therapy for SCI and potentially other forms of neurotrauma.
Spinal cord injury (SCI) causes neuronal death, demyelination of surviving axons, and altered ion channel functioning, resulting in impaired axonal conduction. The large-conductance, voltage and Ca(2+)-activated K(+) (BK or Maxi K(+)) channels contribute to the repolarization phase of action potentials. Therefore, they may play a significant role in regulating axonal conduction in SCI. In this paper, using combined electrophysiological and molecular approaches, we tested the hypothesis that the deficit in axonal conduction in chronic SCI is partially due to the activation of axonal BK channels. BK channels were found to be expressed in spinal cord white matter axons. These channels are not sensitive to BK channel blocker iberiotoxin in uninjured cords, likely reflecting their juxtaparanodal localization. After chronic injury, BK channels were exposed due to axonal demyelination at the injured site and their activation was found to depend on calcium influx, likely through N-type voltage-dependent calcium channels. Activation of BK channels introduced a reduction in the size of the compound action potentials (CAPs) and in axonal response to high frequency stimulation (HFS). Administration of BK channel blocker iberiotoxin significantly enhanced axonal conduction in the injured cords. Thus, pharmacological targeting of axonal BK channels may provide a therapeutic strategy for the treatment of chronic SCI, by restoring conduction to the remaining functional axons.
Significant vascular changes occur following spinal cord injury (SCI) which contribute to the progressive pathophysiology. In the present study, we used female Wistar rats (300-350g) and a 35 g clip-compression injury at T6-T7 to characterize the spatial and temporal vascular changes that ensue post-SCI. Before sacrifice, animals were injected with vascular tracing dyes: 2% Evans Blue (EB) or FITC-LEA to assess blood-spinal cord barrier (BSCB) integrity or vascular architecture, respectively. Spectrophotometry of EB tissue showed maximal BSCB disruption at 24 hours post-injury, with significant disruption observed until 5 days post-injury (p < 0.01). FITC-LEA identified functional vasculature was dramatically reduced by 24 hours. Similarly, RECA-1 immunohistochemistry showed a significant decrease in the number of vessels at 24 hours post-injury compared to uninjured animals (p < 0.01), with slight increases in endogenous re-vascularization by 10 days post-injury. White matter vs. grey matter quantification showed grey matter vessels are more susceptible to SCI. Finally, we observed an endogenous angiogenic response between 3 and 7 days post-injury: maximal endothelial cell proliferation was observed at day 5. These data indicate that BSCB disruption and endogenous re-vascularization occur at specific time-points following injury, which may be important for developing effective therapeutic interventions for SCI.
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