Variations in protein permeability in different regions of the cerebrospinal fluid

Differential proteomic profile of lumbar and ventricular cerebrospinal fluid

BACKGROUND

Pathological cerebral conditions may manifest in altered composition of the cerebrospinal fluid (CSF). Although diagnostic CSF analysis seeks to establish pathological disturbances in the brain proper, CSF is generally sampled from the lumbar compartment for reasons of technical ease and ethical considerations. We here aimed to compare the molecular composition of CSF obtained from the ventricular versus the lumbar CSF compartments to establish a relevance for employing lumbar CSF as a proxy for the CSF bathing the brain tissue.

METHODS

CSF was collected from 46 patients with idiopathic normal pressure hydrocephalus (iNPH) patients during their diagnostic workup (lumbar samples) and in connection with their subsequent CSF diversion shunt surgery (ventricular samples). The mass-spectrometry-based proteomic profile was determined in these samples and in addition, selected biomarkers were quantified with ELISA (S100B, neurofilament light (NfL), amyloid-β (Aβ₄₀, Aβ₄₂), and total tau (T-tau) and phosphorylated tau (P-tau) forms). The latter analysis was extended to include paired porcine samples obtained from the lumbar compartment and the cerebromedullary cistern closely related to the ventricles.

RESULTS

In total 1231 proteins were detected in the human CSF. Of these, 216 distributed equally in the two CSF compartments, whereas 22 were preferentially (or solely) present in the ventricular CSF and four in the lumbar CSF. The selected biomarkers of neurodegeneration and Alzheimer's disease displayed differential distribution, some with higher (S100B, T-tau, and P-tau) and some with lower (NfL, Aβ₄₀, Aβ₄₂) levels in the ventricular compartment. In the porcine samples, all biomarkers were most abundant in the lumbar CSF.

CONCLUSIONS

The overall proteomic profile differs between the ventricular and the lumbar CSF compartments, and so does the distribution of clinically employed biomarkers. However, for a range of CSF proteins and biomarkers, one can reliably employ lumbar CSF as a proxy for ventricular CSF if or a lumbar/cranial index for the particular molecule has been established. It is therefore important to verify the compartmental preference of the proteins or biomarkers of interest prior to extrapolating from lumbar CSF to that of the ventricular fluid bordering the brain.

Comparison of Lumbar and Ventricular Cerebrospinal Fluid for Diagnosis and Monitoring of Meningitis

Severe meningitis, especially basilar meningitis, can lead to hydrocephalus requiring external ventricular drain (EVD) placement. There are differences in cerebrospinal fluid (CSF) obtained from an EVD compared to a lumbar puncture (LP). Hence, it becomes difficult to compare LP and EVD samples for diagnosis and monitoring of meningitis. Recognizing these differences is important to properly treat and discontinue antibiotics. We report a case series of 6 patients with meningitis comparing EVD and LP CSF study analysis. In all 6 patients, CSF from LP was obtained before EVD placement by 1.7 days on average. Although corrected white blood cell (WBC) counts were elevated in CSF obtained from LP and EVD, the counts were significantly higher in LP CSF. Protein concentration in LP CSF was also significantly higher than EVD CSF. Glucose and red blood cells varied in both LP and EVD samples. Even though EVD CSF was obtained later in the clinical course than LP, slower circulation of CSF in lumbar space as compared to ventricles is likely the reason for a more sterile appearance of EVD CSF for the diagnosis of meningitis. It is important to recognize these differences as EVD CSF analysis for diagnosis of meningitis may lead to a missed diagnosis and false perception of significant improvement when monitoring response to treatment. One can consider repeating LP prior to discontinuation of antibiotics to properly determine the extent of improvement given EVD CSF sample appears more sterile in comparison. Larger studies are needed to confirm the above findings.

Blood-cerebrospinal fluid (CSF) barrier dysfunction means reduced CSF flow not barrier leakage - conclusions from CSF protein data

BACKGROUND

Increased concentrations of serum proteins in cerebrospinal fluid (CSF) are interpreted as blood-CSF barrier dysfunction. Frequently used interpretations such as barrier leakage, disruption or breakdown contradict CSF protein data, which suggest a reduced CSF flow rate as the cause.

RESULTS

Even the severest barrier dysfunctions do not change the molecular size-dependent selectivity or the interindividual variation of the protein transfer across barriers. Serum protein concentrations in lumbar CSF increase with hyperbolic functions, but the levels of proteins that do not pass the barrier remain constant (brain proteins) or increase linearly (leptomeningal proteins). All CSF protein dynamics above and below a lumbar blockade can also be explained, independent of their barrier passage, by a reduced caudally directed flow. Local accumulation of gadolinium in multiple sclerosis (MS) is now understood as due to reduced bulk flow elimination by interstitial fluid (ISF). Nonlinear change of the steady state in barrier dysfunction and along normal rostro-caudal gradients supports the diffusion/flow model and contradicts obstructions of diffusion pathways. Regardless of the cause of the disease, pathophysiological flow blockages are found in bacterial meningitis, leukemia, meningeal carcinomatosis, Guillain-Barré syndrome, MS and experimental allergic encephalomyelitis. In humans, the fortyfold higher albumin concentrations in early fetal development decrease later with maturation of the arachnoid villi, i.e., with beginning CSF outflow, which contradicts a relevant outflow to the lymphatic system. Respiration- and heartbeat-dependent oscillations do not disturb net direction of CSF flow.

CONCLUSION

Blood-CSF and blood-brain barrier dysfunctions are an expression of reduced CSF or ISF flow rate.

Barrier dysfunction or drainage reduction: differentiating causes of CSF protein increase

BACKGROUND

Cerebrospinal fluid (CSF) protein analysis is an important element in the diagnostic chain for various central nervous system (CNS) pathologies. Among multiple existing approaches to interpreting measured protein levels, the Reiber diagram is particularly robust with respect to physiologic inter-individual variability, as it uses multiple subject-specific anchoring values. Beyond reliable identification of abnormal protein levels, the Reiber diagram has the potential to elucidate their pathophysiologic origin. In particular, both reduction of CSF drainage from the cranio-spinal space as well as blood-CNS barrier dysfunction have been suggested ρas possible causes of increased concentration of blood-derived proteins. However, there is disagreement on which of the two is the true cause.

METHODS

We designed two computational models to investigate the mechanisms governing protein distribution in the spinal CSF. With a one-dimensional model, we evaluated the distribution of albumin and immunoglobulin G (IgG), accounting for protein transport rates across blood-CNS barriers, CSF dynamics (including both dispersion induced by CSF pulsations and advection by mean CSF flow) and CSF drainage. Dispersion coefficients were determined a priori by computing the axisymmetric three-dimensional CSF dynamics and solute transport in a representative segment of the spinal canal.

RESULTS

Our models reproduce the empirically determined hyperbolic relation between albumin and IgG quotients. They indicate that variation in CSF drainage would yield a linear rather than the expected hyperbolic profile. In contrast, modelled barrier dysfunction reproduces the experimentally observed relation.

CONCLUSIONS

High levels of albumin identified in the Reiber diagram are more likely to originate from a barrier dysfunction than from a reduction in CSF drainage. Our in silico experiments further support the hypothesis of decreasing spinal CSF drainage in rostro-caudal direction and emphasize the physiological importance of pulsation-driven dispersion for the transport of large molecules in the CSF.

Selective Detection of the D-enantiomer of 2-Hydroxyglutarate in the CSF of Glioma Patients with Mutated Isocitrate Dehydrogenase

PURPOSE

Elevation in D-2-Hydroxyglutarate (D-2HG) has recently emerged as a mandatory byproduct of mutated Isocitrate Dehydrogenase (IDH) genes 1 and 2 in glioma patients. The goal of the present study was to demonstrate the feasibility of detection of elevated levels of D-2HG in the cerebrospinal fluid (CSF) of glioma patients that carry point substitutions in the IDH gene.

EXPERIMENTAL DESIGN

We developed a mass spectrometry (MS)-based platform to detect and quantify the D- and L-forms of 2HG in the CSF of glioma patients. Three independent cohorts of patients were analyzed, comprising a total of 176 samples derived from 84 patients. The levels of D- and L-2HG were used to stratify patients into IDH wild-type or IDH-mutated groups using an empirically obtained threshold of 0.69 μmol/L.

RESULTS

Using this platform, a greater than 17-fold mean increase in D-2HG was observed in the CSF of patients with IDH mutant versus wild-type gliomas. The means for the D-2HG levels in CSF were 0.427 μmol/L in wild-type and 7.439 μmol/L in mutant groups. The C statistic for the receiver operator curve was 0.938, with 84% sensitivity, 90% specificity, and 89% accuracy to detect D-2HG. The levels of D- and L-2HG in CSF from wild-type patients varied by location of CSF draw (cisternal > ventricular > lumbar).

CONCLUSIONS

Our findings demonstrate that the CSF of patients harboring IDH mutant gliomas contain increased levels of D-2HG, which can be reliably detected with a MS-based platform. Clin Cancer Res; 22(24); 6256-65. ©2016 AACR.

Differences between ventricular and lumbar cerebrospinal fluid in hydrocephalus secondary to cysticercosis

We studied ventricular and lumbar cerebrospinal fluid (CSF) in 16 patients with hydrocephalus secondary to meningeal cysticercosis, and samples were taken at the time of the surgical implantation of a ventricular shunt. All lumbar CSF samples revealed raised cell counts (mean, 72 +/- 28/mm3) and protein counts (mean, 78 +/- 12 mg/dl), as well as positive immune reactions to cysticerci antigens. In contrast, 50% of the ventricular CSF samples exhibited cell and protein counts within normal limits and five showed negative immune reactions to cysticerci antigens. Ample differences between ventricular and lumbar CSF were also observed in the contents of glucose and immunoglobulins G, A, and M. The biochemical and immunological composition of the CSF varied greatly along the cerebrospinal axis in patients with chronic arachnoiditis caused by cysticercosis. Our findings further support the premise of the subarachnoid space as an immunologically active substratum and provide information to explain the frequent occlusion of ventricular shunts in patients with hydrocephalus secondary to inflammatory disorders of the subarachnoid space.

[Ventriculo-lumbar gradient of concentration of total cerebrospinal fluid proteins: 1 - mechanisms of origin]

In normal conditions there is a concentration gradient of proteins along the neuraxis. From a low level in the ventricles, ranging from 5 to 15 mg/10C ml, to an intermediate level in the cisterna magna, the protein content reaches its highest level in the lumbar sac, 12 to 44 mg/100 ml. Several mechanisms were considered to elucidate the origin of this gradient but many investigators think that the progressive increase of the protein concentration is best explained by the transfer of proteins from serum to the cerebrospinal fluid due to the relatively raised permeability of blood-cerebrospinal fluid barrier in the spinal subarachnoid space. This paper presents a study of the protein concentrations in cisternal and lumbar cerebrospinal fluid samples of patients with neurocysticercosis in activity. The 11 patients of the first group had free subarachnoid space communication between the cisterna magna and the lumbar sac; the 6 patients of the second group had a complete block of the subarachnoid space between these two levels. In every cerebrospinal fluid specimen the quantitative complement fixation test for cysticercus was performed and the titer determined in order to make an assessment of the central nervous system humoral immune response. The analysis of the data of this investigation shows that the concentration gradient of proteins is evident in the cerebrospinal fluid of patients with patency of the spinal subarachnoid space, and the ratio of concentrations of protein contents in simultaneous cisternal and lumbar samples was similar to that one observed in normal individuals. This gradient is also detected when the intensity of the humoral immune response is determined by quantitative complement fixation test for cysticercus in simultaneous cisternal and lumbar specimens. After the onset of spinal subarachnoid block, the confront of the results of the tests in cerebrospinal fluid samples, obtained before and after the blockage, shows a large increase both in the total protein content as well as the intensity of the humoral immune response, in the lumbar level. The similar increases both in protein concentration and titer of cysticercus complement fixation test in the lumbar fluid, in comparison with the cisternal fluid, in patients with patent spinal subarachnoid space, and the large simultaneous and similar increases in both protein content and titer of the cysticercus complement fixation test in the lumbar fluid of patients with spinal subarachnoid block are in disagreement with the usual explanation of the origin mechanisms of the gradient.(ABSTRACT TRUNCATED AT 400 WORDS)

Intrathecal and extrathecal production of antibrain antibodies in multiple sclerosis

Complement-fixing antibrain antibodies of several specificities were titrated in paired serum and CSF samples from 27 MS patients. The results indicated that the antibodies were synthesized on both sides of the blood-brain barrier in proportions that showed a great interindividual variation. It is suggested that this variation applies also to other MS-associated immunoglobulins.

Effects of experimental ischemia on electrolytes of cortical cerebrospinal fluid and on brain water

✓ A procedure for perfusion over the cortical surfaces of the cerebral hemispheres of monkeys (Macaca mulatta) was used in combination with a procedure for producing sudden, temporary circulatory arrest in one hemisphere while the carotid circulation to the other hemisphere remained intact. The underlying disturbance in brain metabolism subsequent to circulatory arrest for 60 minutes was reflected in part by a decrease in the concentration of sodium and an elevation in the concentration of potassium in the cortical cerebrospinal fluid (CSF) on the ischemic side. The changes occurred at or within 30 minutes of the onset of circulatory arrest. The concentration of chloride in the cortical CSF on the ischemic side did not show significant differences from the control values. The ischemic brain exhibited as much as 18% swelling of cortical gray matter and 16% swelling of subcortical white matter at 5 hours after reestablishment of the carotid circulation. Vascular injury pursuant to ischemia was reflected in a significantly increased permeability to 131I-albumin entering the cortical CSF from the cerebral blood vessels. It is suggested that the CSF and vascular water are the sources of increased brain water.