Preterm intraventricular hemorrhage in vitro: modeling the cytopathology of the ventricular zone

Early depletion of gut microbiota shape oligodendrocyte response after traumatic brain injury

White matter injury (WMI) is thought to be a major contributor to long-term cognitive dysfunctions after traumatic brain injury (TBI). This damage occurs partly due to apoptotic death of oligodendrocyte lineage cells (OLCs) after the injury, triggered directly by the trauma or in response to degenerating axons. Recent research suggests that the gut microbiota modulates the inflammatory response through the regulation of peripheral immune cell infiltration after TBI. Additionally, T-cells directly impact OLCs differentiation and proliferation. Therefore, we hypothesized that the gut microbiota plays a critical role in regulating the OLC response to WMI influencing T-cells differentiation and activation. Gut microbial depletion early after TBI chronically reduced re-myelination, acutely decreased OLCs proliferation, and was associated with increased myelin debris accumulation. Surprisingly, the absence of T-cells in gut microbiota depleted mice restored OLC proliferation and remyelination after TBI. OLCs co-cultured with T-cells derived from gut microbiota depleted mice resulted in impaired proliferation and increased expression of MHC-II compared with T cells from control-injured mice. Furthermore, MHC-II expression in OLCs appears to be linked to impaired proliferation under gut microbiota depletion and TBI conditions. Collectively our data indicates that depletion of the gut microbiota after TBI impaired remyelination, reduced OLCs proliferation with concomitantly increased OLC MHCII expression, and required the presence of T cells. This data suggests that T cells are an important mechanistic link by which the gut microbiota modulate the oligodendrocyte response and white matter recovery after TBI.

Gut Microbiota Shape Oligodendrocyte Response after Traumatic Brain Injury

White matter injury (WMI) is thought to be a major contributor to long-term cognitive dysfunctions after traumatic brain injury (TBI). This damage occurs partly due to apoptotic death of oligodendrocyte lineage cells (OLCs) after the injury, triggered directly by the trauma or in response to degenerating axons. Recent research suggests that the gut microbiota modulates the inflammatory response through the modulation of peripheral immune cell infiltration after TBI. Additionally, T-cells directly impact OLCs differentiation and proliferation. Therefore, we hypothesized that the gut microbiota plays a critical role in regulating the OLC response to WMI influencing T-cells differentiation and activation. Gut microbial depletion early after TBI chronically reduced re-myelination, acutely decreased OLCs proliferation, and was associated with increased myelin debris accumulation. Surprisingly, the absence of T-cells in gut microbiota depleted mice restored OLC proliferation and remyelination after TBI. OLCs co-cultured with T-cells derived from gut microbiota depleted mice resulted in impaired proliferation and increased expression of MHC-II compared with T cells from control-injured mice. Furthermore, MHC-II expression in OLCs appears to be linked to impaired proliferation under gut microbiota depletion and TBI conditions. Collectively our data indicates that depletion of the gut microbiota after TBI impaired remyelination, reduced OLCs proliferation with concomitantly increased OLC MHCII expression and required the presence of T cells. This data suggests that T cells are an important mechanistic link by which the gut microbiota modulate the oligodendrocyte response and white matter recovery after TBI.

Intraventricular dimethyl sulfoxide (DMSO) induces hydrocephalus in a dose-dependent pattern

Introduction

Dimethyl sulfoxide (DMSO), a widely utilized solvent in the medical industry, has been associated with various adverse effects, even at low concentrations, including damage to mitochondrial integrity, altered membrane potentials, caspase activation, and apoptosis. Notably, therapeutic molecules for central nervous system treatments, such as embolic agents or some chemotherapy drugs that are dissolved in DMSO, have been associated with hydrocephalus as a secondary complication. Our study investigated the potential adverse effects of DMSO on the brain, specifically focusing on the development of hydrocephalus and the effect on astrocytes.

Methods

Varied concentrations of DMSO were intraventricularly injected into 3-day-old mice, and astrocyte cultures were exposed to similar concentrations of DMSO. After 14 days of injection, magnetic resonance imaging (MRI) was employed to quantify the brain ventricular volumes in mice. Immunofluorescence analysis was conducted to delineate DMSO-dependent effects in the brain. Additionally, astrocyte cultures were utilized to assess astrocyte viability and the effects of cellular apoptosis.

Results

Our findings revealed a dose-dependent induction of ventriculomegaly in mice with 2%, 10%, and 100% DMSO injections (p < 0.001). The ciliated cells of the ventricles were also proportionally affected by DMSO concentration (p < 0.0001). Furthermore, cultured astrocytes exhibited increased apoptosis after DMSO exposure (p < 0.001).

Conclusion

Our study establishes that intraventricular administration of DMSO induces hydrocephalus in a dose-dependent manner. This observation sheds light on a potential explanation for the occurrence of hydrocephalus as a secondary complication in intracranial treatments utilizing DMSO as a solvent.

Design of a Stem Cell-Based Therapy for Ependymal Repair in Hydrocephalus Associated With Germinal Matrix Hemorrhages

BACKGROUND

In preterm birth germinal matrix hemorrhages (GMHs) and the consequent posthemorrhagic hydrocephalus (PHH), the neuroepithelium/ependyma development is disrupted. This work is aimed to explore the possibilities of ependymal repair in GMH/PHH using a combination of neural stem cells, ependymal progenitors (EpPs), and mesenchymal stem cells.

METHODS

GMH/PHH was induced in 4-day-old mice using collagenase, blood, or blood serum injections. PHH severity was characterized 2 weeks later using magnetic resonance, immunofluorescence, and protein expression quantification with mass spectrometry. Ependymal restoration and wall regeneration after stem cell treatments were tested in vivo and in an ex vivo experimental approach using ventricular walls from mice developing moderate and severe GMH/PHH. The effect of the GMH environment on EpP differentiation was tested in vitro. Two-tailed Student t or Wilcoxon-Mann-Whitney U test was used to find differences between the treated and nontreated groups. ANOVA and Kruskal-Wallis tests were used to compare >2 groups with post hoc Tukey and Dunn multiple comparison tests, respectively.

RESULTS

PHH severity was correlated with the extension of GMH and ependymal disruption (means, 88.22% severe versus 19.4% moderate). GMH/PHH hindered the survival rates of the transplanted neural stem cells/EpPs. New multiciliated ependymal cells could be generated from transplanted neural stem cells and more efficiently from EpPs (15% mean increase). Blood and TNFα (tumor necrosis factor alpha) negatively affected ciliogenesis in cells committed to ependyma differentiation (expressing Foxj1 [forkhead box J1] transcription factor). Pretreatment with mesenchymal stem cells improved the survival rates of EpPs and ependymal differentiation while reducing the edematous (means, 18% to 0.5% decrease in severe edema) and inflammatory conditions in the explants. The effectiveness of this therapeutical strategy was corroborated in vivo (means, 29% to 0% in severe edema).

CONCLUSIONS

In GMH/PHH, the ependyma can be restored and edema decreased from either neural stem cell or EpP transplantation in vitro and in vivo. Mesenchymal stem cell pretreatment improved the success of the ependymal restoration.

Polyvinylpyrrolidone-coated catheters decrease choroid plexus adhesion and improve flow/pressure performance in an in vitro model of hydrocephalus

PURPOSE

Proximal catheter obstruction is the leading cause of ventricular shunt failure in pediatric patients. Our aim is to evaluate various types of shunt catheters to assess in vitro cellular adhesion and obstruction.

METHODS

Four catheter types were tested: (1) antibiotic and impregnated, (2) barium-stripe polyvinylpyrrolidone coated (PVP), (3) barium-stripe, and (4) barium-impregnated. Catheters were seeded with choroid plexus epithelial cells to test cellular adhesion and inoculated with the same cells to test flow/pressure performance under choroid plexus growth conditions. Ventricular catheters were placed into a three-dimensional printed phantom ventricular replicating system through which artificial cerebrospinal fluid (CSF) was pumped. Differential pressure sensors were used to measure catheter performance.

RESULTS

PVP catheters had the lowest median cell attachment (10 cells) compared to antibiotic-impregnated (230 cells), barium stripe (513 cells), and barium-impregnated (146 cells) catheters after culture (p < 0.01). In addition, PVP catheters (- 0.247 cm H2O) and antibiotic-impregnated (- 1.15 cm H2O) catheters had significantly lower pressure in the phantom ventricular system compared to the barium stripe (0.167 cm H2O) and barium-impregnated (0.618 cm H2O; p < 0.01) catheters.

CONCLUSIONS

PVP catheters showed less cellular adhesion and, together with antibiotic-impregnated catheters, required less differential pressure to maintain a consistent flow. Our findings suggest clinical relevance for using PVP ventricular catheters in patients with recurrent catheter obstruction by choroid plexus.

Microglia-derived CCL20 deteriorates neurogenesis following intraventricular hemorrhage

Intraventricular hemorrhage (IVH) commonly occurs as an extension of intracerebral hemorrhage (ICH) into the brain ventricular system, leading to worse outcomes without effective management. Using a mouse model of IVH, we found that impaired neurogenesis is evident in the subventricular zone (SVZ), along with persistent microglia activation, leukocyte infiltration and cell death. Pharmacological depletion of microglia using PLX3397, an inhibitor of colony stimulating factor 1 receptor (CSF1R), promotes neurogenesis, and alleviated delayed functional impairments in IVH mice. Meanwhile, an elevated level of microglia-derived CC chemokine ligand 20 (CCL20) is observed in the SVZ following IVH, which can induce the upregulation of pro-inflammatory factors in microglia and impair the proliferation and survival of neural stem cells (NSCs) in vitro. Blocking CCL20 in microglia leads to downregulation of protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/the nuclear factor-κB (NF-κB) signaling pathway, which may contribute to CCL20-dependent pro-inflammatory responses and neural injury. These findings demonstrate a detrimental role of microglia in the neurogenesis and neurorepair after IVH in which CCL20 likely plays a role.

Recombinant Erythropoietin Induces Oligodendrocyte Progenitor Cell Proliferation After Traumatic Brain Injury and Delayed Hypoxemia

Traumatic brain injury (TBI) can result in axonal loss and demyelination, leading to persistent damage in the white matter. Demyelinated axons are vulnerable to pathologies related to an abnormal myelin structure that expose neurons to further damage. Oligodendrocyte progenitor cells (OPCs) mediate remyelination after recruitment to the injury site. Often this process is inefficient due to inadequate OPC proliferation. To date, no effective treatments are currently available to stimulate OPC proliferation in TBI. Recombinant human erythropoietin (rhEPO) is a pleiotropic neuroprotective cytokine, and its receptor is present in all stages of oligodendroglial lineage cell differentiation. Therefore, we hypothesized that rhEPO administration would enhance remyelination after TBI through the modulation of OPC response. Utilizing a murine model of controlled cortical impact and a primary OPC culture in vitro model, we characterized the impact of rhEPO on remyelination and proliferation of oligodendrocyte lineage cells. Myelin black gold II staining of the peri-contusional corpus callosum revealed an increase in myelinated area in association with an increase in BrdU-positive oligodendrocytes in injured mice treated with rhEPO. Furthermore, morphological analysis of OPCs showed a decrease in process length in rhEPO-treated animals. RhEPO treatment increased OPC proliferation after in vitro CSPG exposure. Erythropoietin receptor (EPOr) gene knockdown using siRNA prevented rhEPO-induced OPC proliferation, demonstrating that the rhEPO effect on OPC response is EPOr activation dependent. Together, our findings demonstrate that rhEPO administration may promote myelination by increasing oligodendrocyte lineage cell proliferation after TBI.

Generation of Periventricular Reactive Astrocytes Overexpressing Aquaporin 4 Is Stimulated by Mesenchymal Stem Cell Therapy

Aquaporin-4 (AQP4) plays a crucial role in brain water circulation and is considered a therapeutic target in hydrocephalus. Congenital hydrocephalus is associated with a reaction of astrocytes in the periventricular white matter both in experimental models and human cases. A previous report showed that bone marrow-derived mesenchymal stem cells (BM-MSCs) transplanted into the lateral ventricles of hyh mice exhibiting severe congenital hydrocephalus are attracted by the periventricular astrocyte reaction, and the cerebral tissue displays recovery. The present investigation aimed to test the effect of BM-MSC treatment on astrocyte reaction formation. BM-MSCs were injected into the lateral ventricles of four-day-old hyh mice, and the periventricular reaction was detected two weeks later. A protein expression analysis of the cerebral tissue differentiated the BM-MSC-treated mice from the controls and revealed effects on neural development. In in vivo and in vitro experiments, BM-MSCs stimulated the generation of periventricular reactive astrocytes overexpressing AQP4 and its regulatory protein kinase D-interacting substrate of 220 kDa (Kidins220). In the cerebral tissue, mRNA overexpression of nerve growth factor (NGF), vascular endothelial growth factor (VEGF), hypoxia-inducible factor-1 (HIF1α), and transforming growth factor beta 1 (TGFβ1) could be related to the regulation of the astrocyte reaction and AQP4 expression. In conclusion, BM-MSC treatment in hydrocephalus can stimulate a key developmental process such as the periventricular astrocyte reaction, where AQP4 overexpression could be implicated in tissue recovery.

Polyvinylpyrrolidone-Coated Catheters Decrease Astrocyte Adhesion and Improve Flow/Pressure Performance in an Invitro Model of Hydrocephalus

The leading cause of ventricular shunt failure in pediatric patients is proximal catheter occlusion. Here, we evaluate various types of shunt catheters to assess in vitro cellular adhesion and obstruction. The following four types of catheters were tested: (1) antibiotic- and barium-impregnated, (2) polyvinylpyrrolidone, (3) barium stripe, and (4) barium impregnated. Catheters were either seeded superficially with astrocyte cells to test cellular adhesion or inoculated with cultured astrocytes into the catheters to test catheter performance under obstruction conditions. Ventricular catheters were placed into a three-dimensional printed phantom ventricular replicating system through which artificial CSF was pumped. Differential pressure sensors were used to measure catheter performance. Polyvinylpyrrolidone catheters had the lowest median cell attachment compared to antibiotic-impregnated (18 cells), barium stripe (17 cells), and barium-impregnated (21.5 cells) catheters after culture (p < 0.01). In addition, polyvinylpyrrolidone catheters had significantly higher flow in the phantom ventricular system (0.12 mL/min) compared to the antibiotic coated (0.10 mL/min), barium stripe (0.02 mL/min) and barium-impregnated (0.08 mL/min; p < 0.01) catheters. Polyvinylpyrrolidone catheters showed less cellular adhesion and were least likely to be occluded by astrocyte cells. Our findings can help suggest patient-appropriate proximal ventricular catheters for clinical use.

AQP4, Astrogenesis, and Hydrocephalus: A New Neurological Perspective

Aquaporin 4 (AQP4) is a cerebral glial marker that labels ependymal cells and astrocytes' endfeet and is the main water channel responsible for the parenchymal fluid balance. However, in brain development, AQP4 is a marker of glial stem cells and plays a crucial role in the pathophysiology of pediatric hydrocephalus. Gliogenesis characterization has been hampered by a lack of biomarkers for precursor and intermediate stages and a deeper understanding of hydrocephalus etiology is needed. This manuscript is a focused review of the current research landscape on AQP4 as a possible biomarker for gliogenesis and its influence in pediatric hydrocephalus, emphasizing reactive astrogliosis. The goal is to understand brain development under hydrocephalic and normal physiologic conditions.

Mechanisms of neuroinflammation in hydrocephalus after intraventricular hemorrhage: a review

Intraventricular hemorrhage (IVH) is a significant cause of morbidity and mortality in both neonatal and adult populations. IVH not only causes immediate damage to surrounding structures by way of mass effect and elevated intracranial pressure; the subsequent inflammation causes additional brain injury and edema. Of those neonates who experience severe IVH, 25-30% will go on to develop post-hemorrhagic hydrocephalus (PHH). PHH places neonates and adults at risk for white matter injury, seizures, and death. Unfortunately, the molecular determinants of PHH are not well understood. Within the past decade an emphasis has been placed on neuroinflammation in IVH and PHH. More information has come to light regarding inflammation-induced fibrosis and cerebrospinal fluid hypersecretion in response to IVH. The aim of this review is to discuss the role of neuroinflammation involving clot-derived neuroinflammatory factors including hemoglobin/iron, peroxiredoxin-2 and thrombin, as well as macrophages/microglia, cytokines and complement in the development of PHH. Understanding the mechanisms of neuroinflammation after IVH may highlight potential novel therapeutic targets for PHH.

AQP4 labels a subpopulation of white matter-dependent glial radial cells affected by pediatric hydrocephalus, and its expression increased in glial microvesicles released to the cerebrospinal fluid in obstructive hydrocephalus

Hydrocephalus is a distension of the ventricular system associated with ventricular zone disruption, reactive astrogliosis, periventricular white matter ischemia, axonal impairment, and corpus callosum alterations. The condition's etiology is typically attributed to a malfunction in classical cerebrospinal fluid (CSF) bulk flow; however, this approach does not consider the unique physiology of CSF in fetal and perinatal patients. The parenchymal fluid contributes to the glymphatic system, and plays a fundamental role in pediatric hydrocephalus, with aquaporin 4 (AQP4) as the primary facilitator of these fluid movements. Despite the importance of AQP4 in the pathophysiology of hydrocephalus, it’s expression in human fetal life is not well-studied. This manuscript systematically defines the brain expression of AQP4 in human brain development under control (n = 13) and hydrocephalic conditions (n = 3). Brains from 8 postconceptional weeks (PCW) onward and perinatal CSF from control (n = 2), obstructive (n = 6) and communicating (n = 6) hydrocephalic samples were analyzed through immunohistochemistry, immunofluorescence, western blot, and flow cytometry. Our results indicate that AQP4 expression is observed first in the archicortex, followed by the ganglionic eminences and then the neocortex. In the neocortex, it is initially at the perisylvian regions, and lastly at the occipital and prefrontal zones. Characteristic astrocyte end-feet labeling surrounding the vascular system was not established until 25 PCW. We also found AQP4 expression in a subpopulation of glial radial cells with processes that do not progress radially but, rather, curve following white matter tracts (corpus callosum and fornix), which were considered as glial stem cells (GSC). Under hydrocephalic conditions, GSC adjacent to characteristic ventricular zone disruption showed signs of early differentiation into astrocytes which may affect normal gliogenesis and contribute to the white matter dysgenesis. Finally, we found that AQP4 is expressed in the microvesicle fraction (p < 0.01) of CSF from patients with obstructive hydrocephalus. These findings suggest the potential use of AQP4 as a diagnostic and prognostic marker of pediatric hydrocephalus and as gliogenesis biomarker.

Acquired hydrocephalus is associated with neuroinflammation, progenitor loss, and cellular changes in the subventricular zone and periventricular white matter

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.

Response of Astrocytes to Blood Exposure due to Shunt Insertion in vitro

The breakdown of the ventricular zone (VZ) with the presence of blood in cerebrospinal fluid (CSF) has been shown to increase shunt catheter obstruction in the treatment of hydrocephalus, but the mechanisms by which this occurs are generally unknown. Using a custom-built incubation chamber, we immunofluorescently assayed cell attachment and morphology on shunt catheters with and without blood after 14 days. Samples exposed to blood showed significantly increased cell attachment (average total cell count 392.0±317.1 versus control of 94.7±44.5, P<0.0001). Analysis of the glial fibrillary acidic protein (GFAP) expression showed similar trends (854.4±450.7 versus control of 174.3±116.5, P<0.0001). An in vitro model was developed to represent the exposure of astrocytes to blood following an increase in BBB permeability. Exposure of astrocytes to blood increases the number of cells and their spread on the shunt.

Genetics and Molecular Pathogenesis of Human Hydrocephalus

Hydrocephalus is a neurological disorder with an incidence of 80-125 per 100,000 live births in the United States. The molecular pathogenesis of this multidimensional disorder is complex and has both genetic and environmental influences. This review aims to discuss the genetic and molecular alterations described in human hydrocephalus, from well-characterized, heritable forms of hydrocephalus (e.g., X-linked hydrocephalus from L1CAM variants) to those affecting cilia motility and other complex pathologies such as neural tube defects and Dandy-Walker syndrome. Ventricular zone disruption is one key pattern among congenital and acquired forms of hydrocephalus, with abnormalities in cadherins, which mediate neuroepithelium/ependymal cell junctions and contribute to the pathogenesis and severity of the disease. Given the relationship between hydrocephalus pathogenesis and neurodevelopment, future research should elucidate the genetic and molecular mechanisms that regulate ventricular zone integrity and stem cell biology.

Impact of sex differences on thrombin-induced hydrocephalus and white matter injury: the role of neutrophils

BACKGROUND

Thrombin has been implicated in playing a role in hydrocephalus development following intraventricular hemorrhage (IVH). However, the mechanisms underlying the sex differences to the detrimental effects of thrombin post-IVH remain elusive.

METHOD

Three-month old male and female Sprague-Dawley rats underwent unilateral intracerebroventricular (ICV) injections of 3U or 5U thrombin, or saline, to examine differences in thrombin-induced hydrocephalus and white matter injury. Mortality, and lateral ventricle volume and white matter injury were measured on magnetic resonance imaging evaluation at 24 h post-injection. In addition, male rats were pretreated with 17-β estradiol (E2, 5 mg/kg) or vehicle at 24 and 2 h prior to ICV injection of 3U thrombin. All rats were euthanized at 24 h post-injection for histology and immunohistochemistry.

RESULTS

ICV injection of 5U thrombin caused 100 and 0% mortality in female and male rats, respectively. 3U of thrombin resulted in significant ventricular dilation and white matter damage at 24 h in both male and female rats, but both were worse in females (p < 0.05). Furthermore, neutrophil infiltration into choroid plexus and periventricular white matter was enhanced in female rats and may play a critical role in the sex difference in brain injury. Pre-treating male rats with E2, increased thrombin (3U)-induced hydrocephalus, periventricular white matter injury and neutrophil infiltration into the choroid plexus and white matter.

CONCLUSIONS

ICV thrombin injection induced more severe ventricular dilation and white matter damage in female rats compared to males. Estrogen appears to contribute to this difference which may involve greater neutrophil infiltration in females. Understanding sex differences in thrombin-induced brain injury may shed light on future interventions for hemorrhagic stroke.

Brain Barriers and brain fluids research in 2020 and the fluids and barriers of the CNS thematic series on advances in in vitro modeling of the blood-brain barrier and neurovascular unit

This editorial discusses advances in brain barrier and brain fluid research in 2020. Topics include: the cerebral endothelium and the neurovascular unit; the choroid plexus; the meninges; cerebrospinal fluid and the glymphatic system; disease states impacting the brain barriers and brain fluids; drug delivery to the brain. This editorial also highlights the recently completed Fluids Barriers CNS thematic series entitled, Advances in in vitro modeling of the bloodbrain barrier and neurovascular unit. Such in vitro modeling is progressing rapidly.