Correlations of Ventricular Enlargement with Rheologically Active Surfactant Proteins in Cerebrospinal Fluid

Reactive microglia and mitochondrial unfolded protein response following ventriculomegaly and behavior defects in kaolin-induced hydrocephalus

Ventriculomegaly induced by the abnormal accumulation of cerebrospinal fluid (CSF) leads to hydrocephalus, which is accompanied by neuroinflammation and mitochondrial oxidative stress. The mitochondrial stress activates mitochondrial unfolded protein response (UPRmt), which is essential for mitochondrial protein homeostasis. However, the association of inflammatory response and UPRmt in the pathogenesis of hydrocephalus is still unclear. To assess their relevance in the pathogenesis of hydrocephalus, we established a kaolin-induced hydrocephalus model in 8-week-old male C57BL/6J mice and evaluated it over time. We found that kaolin-injected mice showed prominent ventricular dilation, motor behavior defects at the 3-day, followed by the activation of microglia and UPRmt in the motor cortex at the 5-day. In addition, PARP-1/NF-κB signaling and apoptotic cell death appeared at the 5-day. Taken together, our findings demonstrate that activation of microglia and UPRmt occurs after hydrocephalic ventricular expansion and behavioral abnormal-ities which could be lead to apoptotic neuronal cell death, providing a new perspective on the pathogenic mechanism of hydrocephalus.

Postnatal Brain Growth Patterns in Pontocerebellar Hypoplasia

BACKGROUND

Pontocerebellar hypoplasia (PCH) is a rare group of disorders mainly affecting the cerebellum and pons. Supratentorial structures are variably involved. We assessed brain growth patterns in patients with the most frequent forms of PCH, namely PCH1B (OMIM#614678) and PCH2A (OMIM#277470), since in these types of PCH, pre- and postnatal neurodegeneration is established by neuropathological profiling. To assess the influence of the different pathomechanisms on postnatal growth patterns, we included CASK-associated microcephaly and PCH (MICPCH, OMIM#300749) patients in our analyses, as MICPH mimics PCH on magnetic resonance imaging (MRI) but represents a developmental disorder including abnormal neuronal migration.

METHODS

A total of 66 patients were included: 9 patients with PCH1B, 18 patients with PCH2A, 6 patients with MICPCH, and 33 age- and gender-matched hospital-based controls. Segmentation of the vermis and cerebellum was performed manually, as were measurements of the thickness of the head of the caudate nucleus, the width of the anterior horn, and lateral ventricle size.

RESULTS

The cerebellum was severely hypoplastic at birth in all patients, and postnatal growth was nearly absent. In patients with PCH1B/2A, we found relative sparing of the vermis compared with the cerebellar hemispheres. In addition, PCH1B and PCH2A cases demonstrated thinning of the head of the caudate nucleus, an associated increase in anterior horn width, and an increase in lateral ventricle size. None of these features were seen in the MICPCH group.

CONCLUSIONS

Our findings confirm the progressive nature including caudate nucleus atrophy in PCH1B and PCH2A. In MICPCH, the relative sparing of supratentorial structures confirms its different pathomechanism.

CSF Surfactant Protein Changes in Preterm Infants After Intraventricular Hemorrhage

Introduction: Surfactant proteins (SP) have been shown to be inherent proteins of the human CNS and are altered during acute and chronic disturbances of CSF circulation. Aim of the study was to examine the changes of surfactant protein concentrations in CSF of preterm babies suffering from intraventricular hemorrhage. Patients and Methods: Consecutive CSF samples of 21 preterm infants with intraventricular hemorrhages (IVH) and posthemorrhagic hydrocephalus (PHHC) were collected at primary intervention, after 5-10 days and at time of shunt insertion ~50 days after hemorrhage. Samples were analyzed for surfactant proteins A, B, C, and G by ELISA assays and the results were compared to 35 hydrocephalus patients (HC) without hemorrhage and 6 newborn control patients. Results and Discussion: Premature patients with IVH showed a significant elevation of surfactant proteins SP-A, C, and G compared to HC and control groups: mean values for the respective groups were SP-A 4.19 vs. 1.08 vs. 0.38 ng/ml. Mean SP-C 3.63 vs. 1.47 vs. 0.48 ng/ml. Mean SP-G 3.86 vs. 0.17 vs. 0.2 ng/ml. SP-A and G concentrations were slowly falling over time without reaching normal values. SP-C levels declined faster following neurosurgical interventions and reached levels comparable to those of hydrocephalus patients without hemorrhage. Conclusion: Intraventricular hemorrhages of premature infants cause posthemorrhagic CSF flow disturbance and are associated with highly significant elevations of surfactant proteins A, C, and G independent of total CSF protein concentrations.

Rheologically Essential Surfactant Proteins of the CSF Interacting with Periventricular White Matter Changes in Hydrocephalus Patients - Implications for CSF Dynamics and the Glymphatic System

Surfactant proteins (SP) are multi-systemic proteins playing crucial roles in the regulation of rheological properties of physiological fluids, host defense, and the clearance of potentially harmful metabolites. Hydrocephalus patients suffer from disturbed central nervous system (CNS) fluid homeostasis and exhibit remarkably altered SP concentrations within the cerebrospinal fluid (CSF). A connection between CSF-SPs, CSF flow, and ventricular dilatation, a morphological hallmark of hydrocephalus, has been reported previously. However, currently there are no studies investigating the link between rheologically active SPs and periventricular white matter changes caused by impaired CSF microcirculation in hydrocephalic conditions. Thus, the aim of this study was to assess their possible relationships. The present study included 47 individuals (27 healthy subjects and 20 hydrocephalus patients). CSF specimens were analyzed for concentrations of SP-A, SP-C, and SP-D by using enzyme-linked immunosorbent assays (ELISAs). Axial T2w turbo inversion recovery magnitude (TIRM) magnetic resonance imaging was employed in all cases. Using a custom-made MATLAB-based tool for quantification of magnetic resonance signal intensities in the brain, parameters related to disturbed deep white matter CSF microcirculation were estimated (TIRM signal intensity (SI)-mean, minimum, maximum, median, mode, standard deviation, and percentiles, p10th, p25th, p75th, p90th, as well as kurtosis, skewness, and entropy of the SI distribution). Subsequently, statistical analysis was performed (IBM SPSS 24™) to identify differences between hydrocephalic patients and healthy individuals and to further investigate the connections between CSF-SP changes and deep white matter signal intensities. SP-A (0.38 ± 0.23 vs. 0.76 ± 0.49 ng/ml) and SP-C (0.54 ± 0.28 vs. 1.27 ± 1.09 ng/ml) differed between healthy controls and hydrocephalus patients in a statistically significant manner. Also, corresponding quantification of white matter signal intensities revealed statistically significant differences between hydrocephalus patients and healthy individuals: SImean (370.41 ± 188.15 vs. 222.27 ± 99.86, p = 0.001), SImax (1115.30 ± 700.12 vs. 617.00 ± 459.34, p = 0.005), SImedian (321.40 ± 153.17 vs. 209.52 ± 84.86, p = 0.001), SImode (276.55 ± 125.63 vs. 197.26 ± 78.51, p = 0.011), SIstd (157.09 ± 110.07 vs. 81.71 ± 64.94, p = 0.005), SIp10 (229.10 ± 104.22 vs. 140.00 ± 63.12, p = 0.001), SIp25 (266.95 ± 122.62 vs. 175.63 ± 71.42, p = 0.002), SIp75 (428.80 ± 226.88 vs. 252.19 ± 110.91, p = 0.001), SIp90 (596.47 ± 345.61 vs. 322.06 ± 176.00, p = 0.001), skewness (1.19 ± 0.68 vs. 0.43 ± 1.19, p = 0.014), and entropy (5.36 ± 0.37 vs. 4.92 ± 0.51, p = 0.002). There were no differences regarding SP-D levels in hydrocephalus patients vs. healthy controls. In the acute hydrocephalic subgroup, correlations were as follows: SP-A showed a statistically significant correlation with SImax (r = 0.670, p = 0.024), SIstd (r = 0.697, p = 0.017), SIp90 (r = 0.621, p = 0.041), and inverse correlation with entropy (r = - 0.700, p = 0.016). SP-C correlated inversely with entropy (r = - 0.686, p = 0.020). For the chronic hydrocephalus subgroup, the following correlations were identified: SP-A correlated with kurtosis of the TIRM histogram (r = - 0.746, p = 0.021). SP-C correlated with SImean (r = - 0.688, p = 0.041), SImax (r = - 0.741, p = 0.022), SImedian (r = - 0.716, p = 0.030), SImode (r = - 0.765, p = 0.016), SIstd (r = - 0.671, p = 0.048), SIp25 (r = - 0.740, p = 0.023), SIp75 (r = - 0.672, p = 0.048), and SIp90 (r = - 0.667, p = 0.050). SP-D apparently does not play a major role in CSF fluid physiology. SP-A and SP-C are involved in different aspects of CNS fluid physiology. SP-A appears to play an essential compensatory role in acute hydrocephalus and seems less involved in chronic hydrocephalus. In contrary, SP-C profile and white matter changes are remarkably connected in CSF of chronic hydrocephalus patients. Considering the association between CSF flow phenomena, white matter changes, and SP-C profiles, the latter may especially contribute to the regulation of paravascular glymphatic physiology.

Localization, Occurrence, and CSF Changes of SP-G, a New Surface Active Protein with Assumable Immunoregulatory Functions in the CNS

Conventional surfactant proteins (A, B, C, and D) are important players of the innate immunity in the central nervous system and serve as effective regulators of cerebrospinal fluid rheology, probably being involved in clearance of detrimental metabolites like beta-amyloid and phospho-tau. Recently, a novel surfactant protein, SP-G, was described in kidneys and peripheral endocrine and exocrine glands. So far, its presence and possible functions in the central nervous system are unknown. Therefore, our study aimed to elucidate the presence of SP-G in the brain and its concentration in normal and pathologic samples of cerebrospinal fluid in order to gain first insight into its regulation and possible functions. A total of 121 samples of human cerebrospinal fluid (30 controls, 60 hydrocephalus patients, 7 central nervous system infections, and 24 brain hemorrhage patients) and 21 rat brains were included in our study. CSF samples were quantified using a commercially available ELISA system. Results were analyzed statistically using SPSS 22, performing Spearman Rho correlation and ANOVA with Dunnett's post hoc analysis. Rat brains were investigated via immunofluorescence to determine SP-G presence and colocalization with common markers like aquaporin-4, glial fibrillary acidic protein, platelet endothelial adhesion molecule 1, and neuronal nuclear antigen. SP-G occurs associated with brain vessels, comparable to other conventional SPs, and is present in a set of cortical neurons. SP-G is furthermore actively produced by ependymal and choroid plexus epithelium and secreted into the cerebrospinal fluid. Its concentrations are low in control subjects and patients suffering from aqueductal stenosis, higher in normal pressure hydrocephalus (p < 0.01), and highest in infections of the central nervous system and brain hemorrhage (p < 0.001). Interestingly, SP-G did correlate with total CSF protein in patients with CNS infections and hemorrhage, but not with cell count. Based on the changes in CSF levels of SP-G in hydrocephalus, brain hemorrhage, and CNS infections as well as its abundance at CSF flow-related anatomical structures closely associated with immunological barrier systems, importance for CSF rheology, brain waste clearance, and host defense is assumable. Thus, SP-G is a potential new CSF biomarker, possibly not only reflecting aspects of CNS innate immune responses, but also rheo-dynamically relevant changes of CSF composition, associated with CSF malabsorbtion. However, further studies are warranted to validate our findings and increase insight into the physiological importance of SP-G in the CNS.

Elevated Surfactant Protein Levels and Increased Flow of Cerebrospinal Fluid in Cranial Magnetic Resonance Imaging

Surfactant proteins (SPs) are a multifunctional group of proteins, responsible for the regulation of rheological properties of body fluids, host defense, and cellular waste clearance. Their concentrations are changed in cerebrospinal fluid (CSF) of patients suffering from communicating hydrocephalus. Hydrocephalic conditions are accompanied by altered CSF flow dynamics; however, the association of CSF-SP concentrations and CSF flow has not yet been investigated. Hence, the aim of this study was to evaluate the association between SP concentrations in the CSF and marked CSF flow phenomena at different anatomical landmarks of CSF spaces. Sixty-one individuals (15 healthy subjects and 46 hydrocephalus patients) were included in this study. CSF specimens were analyzed for SP-A, SP-B, SP-C, and SP-D concentrations by the use of enzyme-linked immunosorbent assays (ELISA). CSF flow was evaluated in axial T2_turbo inversion recovery magnitude (TIRM)-weighted and sagittal T2-weighted magnetic resonance imaging sections using a 4-grade scale (1-no flow, 2-subtle flow, 3-moderate flow, and 4-strong flow). CSF-SP concentrations (mean ± standard deviation) of the overall collective were as follows: SP-A = 0.73 ± 0.58 ng/ml, SP-B = 0.17 ± 0.93 ng/ml, SP-C = 0.95 ± 0.75 ng/ml, and SP-D = 7.43 ± 5.17 ng/ml. The difference between healthy controls and hydrocephalic patients regarding CSF concentrations of SP-A (0.34 ± 0.22 vs. 0.81 ± 0.59 ng/ml) and SP-C (0.48 ± 0.29 vs. 1.10 ± 0.79 ng/ml) revealed to be statistically significant as calculated by means of ANOVA (p values of 0.022 and 0.007, respectively). CSF flow voids were detectable at all investigated landmarks of the CSF spaces (foramina of Monro, third ventricle, mesencephalic aqueduct, prepontine cistern, fourth ventricle, cisterna magna, and craniocervical junction). CSF flow voids, reported as mean ± standard deviation, revealed to be significantly increased in hydrocephalic patients compared to controls as calculated by means of ANOVA (respective p values are given in brackets following values of descriptive statistics) at the following sites: foramina of Monro (1.60 ± 0.91 vs. 2.37 ± 0.99, p = 0.01), fourth ventricle (1.67 ± 0.98 vs. 2.52 ± 1.05, p = 0.007), and the cisterna magna (1.93 ± 1.10 vs. 2.72 ± 1.13, p = 0.022). Spearman's rank order calculation identified significant correlations for CSF flow voids at the foramina of Monro and the third ventricle with SP-A (r = 0.429, p = 0.001 and r = 0.464, p < 0.001) and CSF flow void at the mesencephalic duct with SP-D (r = - 0.371, p = 0.039). Furthermore, SP-C showed a moderate inverse correlation with age (r = - 0.302, p = 0.022). The present study confirmed statistically significant differences in SP-CSF concentrations between healthy controls and hydrocephalic patients. Additionally, significant correlations between SP concentrations in CSF with increased CSF flow were identified. These findings underline the role of SPs as regulators of CSF rheology.