Browsing by Author "Limbrick, David D."

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    A novel model of acquired hydrocephalus for evaluation of neurosurgical treatments
    (2021-11-08) McAllister, James P.; Talcott, Michael R.; Isaacs, Albert M.; Zwick, Sarah H.; Garcia-Bonilla, Maria; Castaneyra-Ruiz, Leandro; Hartman, Alexis L.; Dilger, Ryan N.; Fleming, Stephen A.; Golden, Rebecca K.; Morales, Diego M.; Harris, Carolyn A.; Limbrick, David D.
    Abstract Background Many animal models have been used to study the pathophysiology of hydrocephalus; most of these have been rodent models whose lissencephalic cerebral cortex may not respond to ventriculomegaly in the same way as gyrencephalic species and whose size is not amenable to evaluation of clinically relevant neurosurgical treatments. Fewer models of hydrocephalus in gyrencephalic species have been used; thus, we have expanded upon a porcine model of hydrocephalus in juvenile pigs and used it to explore surgical treatment methods. Methods Acquired hydrocephalus was induced in 33–41-day old pigs by percutaneous intracisternal injections of kaolin (n = 17). Controls consisted of sham saline-injected (n = 6) and intact (n = 4) animals. Magnetic resonance imaging (MRI) was employed to evaluate ventriculomegaly at 11–42 days post-kaolin and to plan the surgical implantation of ventriculoperitoneal shunts at 14–38-days post-kaolin. Behavioral and neurological status were assessed. Results Bilateral ventriculomegaly occurred post-induction in all regions of the cerebral ventricles, with prominent CSF flow voids in the third ventricle, foramina of Monro, and cerebral aqueduct. Kaolin deposits formed a solid cast in the basal cisterns but the cisterna magna was patent. In 17 untreated hydrocephalic animals. Mean total ventricular volume was 8898 ± 5917 SD mm3 at 11–43 days of age, which was significantly larger than the baseline values of 2251 ± 194 SD mm3 for 6 sham controls aged 45–55 days, (p < 0.001). Past the post-induction recovery period, untreated pigs were asymptomatic despite exhibiting mild-moderate ventriculomegaly. Three out of 4 shunted animals showed a reduction in ventricular volume after 20–30 days of treatment, however some developed ataxia and lethargy, from putative shunt malfunction. Conclusions Kaolin induction of acquired hydrocephalus in juvenile pigs produced an in vivo model that is highly translational, allowing systematic studies of the pathophysiology and clinical treatment of hydrocephalus.
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    Acquired hydrocephalus is associated with neuroinflammation, progenitor loss, and cellular changes in the subventricular zone and periventricular white matter
    (2022-02-22) Garcia-Bonilla, Maria; Castaneyra-Ruiz, Leandro; Zwick, Sarah; Talcott, Michael; Otun, Ayodamola; Isaacs, Albert M.; Morales, Diego M.; Limbrick, David D.; McAllister, James P.
    Abstract Background Hydrocephalus is a neurological disease with an incidence of 80–125 per 100,000 births in the United States. Neuropathology comprises ventriculomegaly, periventricular white matter (PVWM) alterations, inflammation, and gliosis. We hypothesized that hydrocephalus in a pig model is associated with subventricular and PVWM cellular alterations and neuroinflammation that could mimic the neuropathology described in hydrocephalic infants. Methods Hydrocephalus was induced by intracisternal kaolin injections in 35-day old female pigs (n = 7 for tissue analysis, n = 10 for CSF analysis). Age-matched sham controls received saline injections (n = 6). After 19–40 days, MRI scanning was performed to measure the ventricular volume. Stem cell proliferation was studied in the Subventricular Zone (SVZ), and cell death and oligodendrocytes were examined in the PVWM. The neuroinflammatory reaction was studied by quantifying astrocytes and microglial cells in the PVWM, and inflammatory cytokines in the CSF. Results The expansion of the ventricles was especially pronounced in the body of the lateral ventricle, where ependymal disruption occurred. PVWM showed a 44% increase in cell death and a 67% reduction of oligodendrocytes. In the SVZ, the number of proliferative cells and oligodendrocyte decreased by 75% and 57% respectively. The decrease of the SVZ area correlated significantly with ventricular volume increase. Neuroinflammation occurred in the hydrocephalic pigs with a significant increase of astrocytes and microglia in the PVWM, and high levels of inflammatory interleukins IL-6 and IL-8 in the CSF. Conclusion The induction of acquired hydrocephalus produced alterations in the PVWM, reduced cell proliferation in the SVZ, and neuroinflammation.
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    Biochemical profile of human infant cerebrospinal fluid in intraventricular hemorrhage and post-hemorrhagic hydrocephalus of prematurity
    (2021-12-24) Otun, Ayodamola; Morales, Diego M.; Garcia-Bonilla, Maria; Goldberg, Seth; Castaneyra-Ruiz, Leandro; Yan, Yan; Isaacs, Albert M.; Strahle, Jennifer M.; McAllister, James P.; Limbrick, David D.
    Abstract Background Intraventricular hemorrhage (IVH) and post-hemorrhagic hydrocephalus (PHH) have a complex pathophysiology involving inflammatory response, ventricular zone and cell–cell junction disruption, and choroid-plexus (ChP) hypersecretion. Increased cerebrospinal fluid (CSF) cytokines, extracellular matrix proteins, and blood metabolites have been noted in IVH/PHH, but osmolality and electrolyte disturbances have not been evaluated in human infants with these conditions. We hypothesized that CSF total protein, osmolality, electrolytes, and immune cells increase in PHH. Methods CSF samples were obtained from lumbar punctures of control infants and infants with IVH prior to the development of PHH and any neurosurgical intervention. Osmolality, total protein, and electrolytes were measured in 52 infants (18 controls, 10 low grade (LG) IVH, 13 high grade (HG) IVH, and 11 PHH). Serum electrolyte concentrations, and CSF and serum cell counts within 1-day of clinical sampling were obtained from clinical charts. Frontal occipital horn ratio (FOR) was measured for estimating the degree of ventriculomegaly. Dunn or Tukey’s post-test ANOVA analysis were used for pair-wise comparisons. Results CSF osmolality, sodium, potassium, and chloride were elevated in PHH compared to control (p = 0.012 − < 0.0001), LGIVH (p = 0.023 − < 0.0001), and HGIVH (p = 0.015 − 0.0003), while magnesium and calcium levels were higher compared to control (p = 0.031) and LGIVH (p = 0.041). CSF total protein was higher in both HGIVH and PHH compared to control (p = 0.0009 and 0.0006 respectively) and LGIVH (p = 0.034 and 0.028 respectively). These differences were not reflected in serum electrolyte concentrations nor calculated osmolality across the groups. However, quantitatively, CSF sodium and chloride contributed 86% of CSF osmolality change between control and PHH; and CSF osmolality positively correlated with CSF sodium (r, p = 0.55,0.0015), potassium (r, p = 0.51,0.0041), chloride (r, p = 0.60,0.0004), but not total protein across the entire patient cohort. CSF total cells (p = 0.012), total nucleated cells (p = 0.0005), and percent monocyte (p = 0.016) were elevated in PHH compared to control. Serum white blood cell count increased in PHH compared to control (p = 0.042) but there were no differences in serum cell differential across groups. CSF total nucleated cells also positively correlated with CSF osmolality, sodium, potassium, and total protein (p = 0.025 − 0.0008) in the whole cohort. Conclusions CSF osmolality increased in PHH, largely driven by electrolyte changes rather than protein levels. However, serum electrolytes levels were unchanged across groups. CSF osmolality and electrolyte changes were correlated with CSF total nucleated cells which were also increased in PHH, further suggesting PHH is a neuro-inflammatory condition.
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    Pathophysiology and Proteogenomics of Post-infectious and Post-hemorrhagic Hydrocephalus in Infants
    (2020-07-21) Isaacs, Albert M.; Dunn, Jeff F.; Limbrick, David D.; McAllister, James Patterson; Smyser, Christopher D.; Shimony, Joshua S.; Hamilton, Mark G.; Ballabh, Praveen
    Post-infectious (PIH) and post-hemorrhagic (PHH) hydrocephalus occur as sequalae of neonatal sepsis or intraventricular hemorrhage (IVH) of prematurity, respectively. Together, PIH and PHH represent the most common form of infantile hydrocephalus, the most common indication for neurosurgery in children globally, and the leading cause of neurological morbidity and mortality worldwide. The lack of understanding of the pathophysiology of PIH and PHH, particularly with regards to the host central nervous system response to the antecedent infection and hemorrhage, perturbation of differentiating neural stems in the ventricular (VZ) and subventricular (SVZ) zones, and damage to periventricular white matter (PVWM) tracts carrying sensorimotor fibers, has hindered the identification of therapeutic targets to prevent these two debilitating conditions. To this end, we hypothesized that PIH and PHH share a common pathophysiological mechanism characterized by host immune response to infection or hemorrhage, activation of the metalloprotease ADAM10 and cleavage of the cell-junctional protein, N-cadherin, which results in impaired VZ/SVZ differentiation and PVWM damage. The studies presented in this dissertation collectively explore novel overarching lines of scientific inquiry - the concept that there are unique host immune responses to PIH and PHH, as well as ones that are common to both conditions that underlie their observed clinical similarities. To test the hypothesis, we leveraged the cerebrospinal fluid (CSF) of human PIH, PHH and matched non-infectious non-hemorrhagic hydrocephalic control infants. First, we defined the differentially expressed proteome and transcriptome of PIH using high throughput proteomics and RNA-seq, respectively. The integration of proteogenomic techniques defined critical gene networks and pathway level mechanisms of PIH pathophysiology. Second, our validated proteomics pipeline was used to identify the common and unique molecular pathways that underlie the pathophysiology of PIH and PHH. Third, our CSF findings were related to VZ/SVZ development and PVWM microstructural damage with diffusion MRI (dMRI) in PHH and control infants. Neurocytology of human postmortem brain tissues of PIH, PHH and controls was performed to correlate the dMRI findings. Fourth, we defined the mechanistic triggers underlying PIH and PHH pathogenesis utilizing a mouse in vitro cell culture model of periventricular VZ cells. Finally, we developed in vivo animal models of PIH (mice) and PHH (ferrets), to recapitulate our findings of VZ/SVZ disruption, neuroinflammation and PVWM injury in both PIH and PHH. Through our comprehensive experiments, we determined the following: 1) human CSF profiles of PIH and PHH reflect similar alterations in gene-activated pathways related to neuroinflammation and cell-cell junction structure; 2) neuroinflammation-associated cell junction (VZ/SVZ) disruption and PVWM injury is a pathophysiological mechanism that is common to both PIH and PHH; 3) dMRI can non-invasively assess the VZ/SVZ region as well as differentiate and quantify tract-specific patterns of PVWM injury. Therefore, it can distinguish direct effects on axons/myelin from changes in the extracellular milieu to reflect neuroinflammation, axonal fiber loss, and dysmyelination; 4) VZ/SVZ disruption in PIH and PHH is mediated by metalloprotease (e.g., ADAM10) cleavage of cell junctional proteins (e.g., N-cadherin); and 5) pharmacologic inhibition of ADAM10-mediated N-cadherin cleavage represents a viable therapeutic approach to prevent PIH and PHH. These novel insights into the pathophysiology of PIH and PHH may enable investigation of ADAM10 inhibitors and other therapeutic strategies to minimize the developmental disability in PIH and PHH patients. The biomarkers we identified can be further investigated as diagnostic measures for monitoring and providing therapy to infants who develop neonatal sepsis or IVH to prevent PHH/PIH. Finally, the in vitro and in vivo experimental models we generated are poised for future preclinical and translational studies into the pathogenesis of these previously inaccessible and debilitating conditions.