Glial fibrillary acidic protein: a marker of axonal Guillain-Barrè syndrome and outcome

Predicting of Mechanical Ventilation and Outcomes by Using Models and Biomarker in Guillain-Barré Syndrome

BACKGROUND

Guillain-Barré syndrome (GBS) is an acute inflammatory neuropathy. The Erasmus GBS Respiratory Insufficiency Score (EGRIS) and the modified Erasmus GBS Outcome Score (mEGOS) are prognostic models used in the prediction of mechanical ventilation and outcome. Thus far, there are only few biomarkers for the prognosis prediction of GBS patients, and albumin level is one that is promising.

METHODS

Patients diagnosed with GBS from 2013 to 2022 at Renmin Hospital, Wuhan University, China, were included. Patients hospitalized between 2016 and 2022 underwent short- and long-term follow-ups. The correlations between EGRIS/mEGOS and mechanical ventilation and outcome were evaluated. Serum albumin level was examined the day after admission. Furthermore, we also investigated whether the level of serum albumin was useful in predicting disease severity or poor outcome.

RESULTS

In all, 145 patients were enrolled. Nineteen patients (13.1%) who required mechanical ventilation had higher Hughes GBS disability score (HGDS) at admission and discharge (P < 0.05 and P < 0.0001, respectively), shorter time from onset to admission and treatment (P < 0.01 and P < 0.001, respectively) and longer hospital stays (P < 0.001) than patients who did not require mechanical ventilation. High EGRIS scores were linked with the need for mechanical ventilation (r = 0.427, P < 0.001, AUC = 0.623). Seventy-one patients were admitted between 2016 and 2022. Of these, 65 patients had a 4-week follow-up and 61 had a 6-month follow-up. Higher mEGOS scores at admission and 7 days after admission significantly correlated with short- (P < 0.0001 and P < 0.0001) and long-term (P < 0.05 and P < 0.05) outcomes, respectively. No significant difference in outcome was found between different subtypes (4 weeks [P = 0.099] and 6 months [P = 0.172]). Patients with lower albumin level tended to have higher HGDS (at admission P < 0.05, at nadir P < 0.001, and at discharge P < 0.001) and higher properties of the need of mechanical ventilation (P < 0.05) and ICU stay (P < 0.05) than those with normal albumin levels. Those with low albumin levels were also unable to walk independently at 6 months (P < 0.01).

CONCLUSIONS

mEGOS scores predicted the outcomes of GBS patients in China, and EGRIS score predicted the need for mechanical ventilation in these patients. Albumin level at admission correlated well with disease severity and outcomes.

Construction and evaluation of a prognostic prediction model based on the mEGOS score for patients with Guillain-Barré syndrome

Background

Guillain-Barré syndrome (GBS) is an immune-mediated acute peripheral neuropathy in which up to 20% patients remain unable to walk independently after 6 months of onset. This study aimed to develop a clinical prognostic model based on the modified Erasmus GBS Outcome Score (mEGOS) for predicting the prognosis of GBS patients at 6 months of onset.

Methods

The clinical data of 201 GBS patients were retrospectively analyzed. According to the GBS disability score (GBS-DS) at 6 months of onset, patients were divided into a good prognosis group (GBS-DS <3 points) and a poor prognosis group (GBS-DS≥3 points). Univariate and multivariate analysis was used to screen out independent risk factors for poor prognosis, and a prediction model was accordingly constructed for GBS prognosis.

Results

The mEGOS score, serum albumin (ALB) and fasting plasma glucose (FPG) were independent risk factors for poor prognosis in patients with GBS, and the above risk factors were used to construct a prognostic model of mEGOS-I and a nomogram. The receiver operating characteristic (ROC) curve showed that the area under curve (AUC) of mEGOS-I at admission and at 7 days of admission to predict poor prognosis at 6 months of GBS onset was 0.891 and 0.916, respectively, with sensitivities of 82.7% and 82.6% and specificities of 86.5% and 86.6%, respectively. Decision curve analysis showed that the nomogram had a very high clinical benefit.

Conclusion

To our knowledge, this is the first report of the construction of a prognostic prediction model based on the mEGOS score, ALB, and FPG that can accurately and stably predict the prognosis of GBS patients at 6 months of onset.

Fluid Biomarkers for Monitoring Structural Changes in Polyneuropathies: Their Use in Clinical Practice and Trials

Reliable and responsive tools for monitoring disease activity and treatment outcomes in patients with neuropathies are lacking. With the emergence of ultrasensitive blood bioassays, proteins released with nerve damage are potentially useful response biomarkers for many neurological disorders, including polyneuropathies. In this review, we provide an overview of the existing literature focusing on potential applications in polyneuropathy clinical care and trials. Whilst several promising candidates have been identified, no studies have investigated if any of these proteins can serve as response biomarkers of longitudinal disease activity, except for neurofilament light (NfL). For NfL, limited evidence exists supporting a role as a response biomarker in Guillain-Barré syndrome, vasculitic neuropathy, and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Most evidence exists for NfL as a response biomarker in hereditary transthyretin-related amyloidosis (hATTR). At the present time, the role of NfL is therefore limited to a supporting clinical tool or exploratory endpoint in trials. Future developments will need to focus on the discovery of additional biomarkers for anatomically specific and other forms of nerve damage using high-throughput technologies and highly sensitive analytical platforms in adequality powered studies of appropriate design. For NfL, a better understanding of cut-off values, the relation to clinical symptoms and long-term disability as well as dynamics in serum on and off treatment is needed to further expand and proceed towards implementation.

Modeling Neurological Disorders in 3D Organoids Using Human-Derived Pluripotent Stem Cells

Modeling neurological disorders is challenging because they often have both endogenous and exogenous causes. Brain organoids consist of three-dimensional (3D) self-organizing brain tissue which increasingly is being used to model various aspects of brain development and disorders, such as the generation of neurons, neuronal migration, and functional networks. These organoids have been recognized as important in vitro tools to model developmental features of the brain, including neurological disorders, which can provide insights into the molecular mechanisms involved in those disorders. In this review, we describe recent advances in the generation of two-dimensional (2D), 3D, and blood-brain barrier models that were derived from induced pluripotent stem cells (iPSCs) and we discuss their advantages and limitations in modeling diseases, as well as explore the development of a vascularized and functional 3D model of brain processes. This review also examines the applications of brain organoids for modeling major neurodegenerative diseases and neurodevelopmental disorders.

Plasma Biomarker for Post-concussive Syndrome: A Pilot Study Using an Alternating Current Electro-Kinetic Platform

Background: Technology platforms that afford biomarker discovery in patients suffering from traumatic brain injury (TBI) remain an unmet medical need. Here, we describe an observational pilot study to explore the utility of an alternating current electrokinetic (ACE) microchip device in this context.

Methods: Blood samples were collected from participating subjects with and without minor TBI. Plasma levels of glial fibrillary acidic protein (GFAP), Tau, ubiquitin C-terminal hydrolase L1 (UCH-L1), and cell-free DNA (cfDNA) were determined in subjects with and without minor TBI using ACE microchip device followed by on-chip immunofluorescent analysis. Post-concussive symptoms were assessed using the Rivermead Post Concussion Symptoms Questionnaire (RPCSQ) at one-month follow-up.

Results: Highest levels of GFAP, UCH-L1, and Tau were seen in two minor TBI subjects with abnormality on head computed tomography (CT). In patients without abnormal head CT, Tau and GFAP levels discriminated between plasma from minor-TBI and non-TBI patients, with sensitivity and specificity of 64–72 and 50%, respectively. Plasma GFAP, UCH-L1, and Tau strongly correlated with the cumulative RPCSQ score. Plasma UCH-L1 and GFAP exhibited highest correlation to sensitivity to noise and light (r = 0.96 and 0.91, respectively, p < 0.001). Plasma UCH-L1 and Tau showed highest correlation with headache (r = 0.74 and 0.78, respectively, p < 0.001), sleep disturbance (r = 0.69 and 0.84, respectively, p < 0.001), and cognitive symptoms, including forgetfulness (r = 0.76 and 0.74, respectively, p < 0.001), poor concentration (r = 0.68 and 0.76, respectively, p < 0.001), and time required for information processing (r = 0.77 and 0.81, respectively, p < 0.001). cfDNA exhibited a strong correlation with depression (r = 0.79, p < 0.01) and dizziness (r = 0.69, p < 0.01). While cfDNA demonstrated positive correlation with dizziness and depression (r = 0.69 and 0.79, respectively, p < 0.001), no significant correlation was observed between cumulative RPCSQ and cfDNA (r = 0.07, p = 0.81).

Conclusion: We provide proof-of-principle results supporting the utility of ACE microchip for plasma biomarker analysis in patients with minor TBI.

Studying Human Neurological Disorders Using Induced Pluripotent Stem Cells: From 2D Monolayer to 3D Organoid and Blood Brain Barrier Models

Neurological disorders have emerged as a predominant healthcare concern in recent years due to their severe consequences on quality of life and prevalence throughout the world. Understanding the underlying mechanisms of these diseases and the interactions between different brain cell types is essential for the development of new therapeutics. Induced pluripotent stem cells (iPSCs) are invaluable tools for neurological disease modeling, as they have unlimited self-renewal and differentiation capacity. Mounting evidence shows: (i) various brain cells can be generated from iPSCs in two-dimensional (2D) monolayer cultures; and (ii) further advances in 3D culture systems have led to the differentiation of iPSCs into organoids with multiple brain cell types and specific brain regions. These 3D organoids have gained widespread attention as in vitro tools to recapitulate complex features of the brain, and (iii) complex interactions between iPSC-derived brain cell types can recapitulate physiological and pathological conditions of blood-brain barrier (BBB). As iPSCs can be generated from diverse patient populations, researchers have effectively applied 2D, 3D, and BBB models to recapitulate genetically complex neurological disorders and reveal novel insights into molecular and genetic mechanisms of neurological disorders. In this review, we describe recent progress in the generation of 2D, 3D, and BBB models from iPSCs and further discuss their limitations, advantages, and future ventures. This review also covers the current status of applications of 2D, 3D, and BBB models in drug screening, precision medicine, and modeling a wide range of neurological diseases (e.g., neurodegenerative diseases, neurodevelopmental disorders, brain injury, and neuropsychiatric disorders). © 2019 American Physiological Society. Compr Physiol 9:565-611, 2019.

Blood Level of Glial Fibrillary Acidic Protein (GFAP) Does not Correlate With Disease Progression in a Rat Model of Familial ALS (SOD1G93A Transgenic)

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by specific loss of motor neurons in the spinal cord and brain stem. Currently, there are limited options for treating ALS and further investigation of the disease etiology and ALS disease progression need to be completed. There is an urgent need to identify biomarkers to detect and study disease progression in ALS. Glial fibrillary acidic protein (GFAP) is an intermediate filament protein that is expressed by a number of cells related to the central nervous system including glial cells and ependymal cells. Recent studies indicated that significant levels of GFAP protein were detected in peripheral tissues, such as skeletal muscle. In this study, we hypothesized that levels of GFAP in blood represent a biomarker of disease progression in ALS. To test this specific hypothesis, we used a rat model of familial ALS (SOD1^G93A transgenic), which has been extensively used to understand the complexity of this devastating disease. Disease progression in a cohort of male and female SOD1^G93A transgenic rats was monitored by motor function, and blood samples were collected when these animals reached disease end-stage. We measured GFAP protein levels by ELISA and found no correlation between GFAP concentration and disease progression in either serum and plasma samples of SOD1^G93A transgenic. Further investigation would be required in order to implicate blood GFAP as a potential biomarker for ALS.

Neurofilament light protein levels in cerebrospinal fluid predict long-term disability of Guillain-Barré syndrome: A pilot study

OBJECTIVES

Although the recovery from Guillain-Barré syndrome (GBS) is good in most patients, some develop permanent severe disability or even die. Early predictors would increase the likelihood to identify patients at risk for poor outcome at the acute stage, allowing them intensified therapeutic intervention.

MATERIALS AND METHOD

Eighteen patients with a history of GBS 9-17 years ago were reassessed with scoring of neurological disability and quality of life assessment (QoL). Their previous diagnostic work-up included clinical examination with scoring of disability, neurophysiological investigation, a battery of serology tests for infections, and cerebrospinal fluid (CSF) examination. Aliquots of CSF were frozen, stored for 20-28 years, and analyzed by ELISA for determination of neurofilament light protein (NFL) and glial fibrillary acidic protein (GFAP).

RESULTS

Patients with poor outcome (n = 3) had significantly higher NFL and GFAP levels at GBS nadir than those with good outcome (n = 15, P < .01 and P < .05, respectively). High NFL correlated with more prominent disability and worse QoL at long-term follow-up (r = .694, P < .001, and SF 36 dimension physical component summary (PCS) (r =-.65, P < .05), respectively, whereas GFAP did not correlate with clinical outcome or QoL.

CONCLUSION

High NFL in CSF at the acute stage of GBS seems to predict long-term outcome and might, together with neurophysiological and clinical measures, be useful in treatment decisions and clinical care of GBS.

Three-dimensional reconstruction of the pharyngeal tonsil innervation pattern in sheep

The pharyngeal tonsil has recently been identified as a new participant in airborne contamination by the ovine scrapie agent. In the context of scrapie pathogenesis, we conducted a three-dimensional reconstruction of the innervation pattern in the lymphoid compartments of this tonsil. This model confirmed that very few nerve fibres penetrated the lymphoid follicles and suggested that the nerve fibre distribution in the interfollicular and subepithelial areas is more suitable with neuro-invasion through direct contact between these nerve fibres and prion-transporting cells prior to or after prion amplification in the germinal centre of the pharyngeal tonsil lymphoid follicles.

High plasma-GFAP levels in metastatic myxopapillary ependymoma

Myxopapillary ependymoma (MPE) is a rare tumor of the distal spinal cord. Despite benign histopathology, local recurrences occur in ~30 % of patients and distant metastases have been described in few cases. MPE tumor cells typically express glial fibrillary acidic protein (GFAP), which could be released to the circulation. In this current report, we investigated circulating plasma-GFAP in a series of MPE patients. We analyzed circulating plasma-GFAP using a commercially available ELISA kit in 3 patients with completely resected MPE, 1 patient with locally advanced MPE and 2 patients with pleuropulmonary metastases of MPE. As controls we used blood samples of age and gender-matched healthy volunteers (n = 3), 6 glioblastoma patients with known plasma-GFAP status (positive for 3 and negative for 3 patients) and 3 brain metastases patients with known plasma-GFAP negativity. We found very high concentrations of plasma-GFAP in two MPE patients with pleuropulmonary metastases, while in none of the other MPE patients circulating plasma-GFAP was detectable. Circulating GFAP could be useful as marker for early detection or follow-up of distant metastases in MPE patients.

Neuroimmune connections in ovine pharyngeal tonsil: potential site for prion neuroinvasion

Recent studies have established the involvement of nasal-associated lymphoid tissues, mainly the pharyngeal tonsil, in prion pathogenesis. However, the mechanisms of the associated neuroinvasion are still debated. To determine potential sites for prion neuroinvasion inside the ovine pharyngeal tonsil, the topography of heavy (200 kDa) and light (70 kDa) neurofilaments and of glial fibrillar acidic protein has been semi-quantitatively analysed inside the various compartments of the tonsil. The results show that the most innervated areas are the interfollicular area and the connective tissue located beneath the respiratory epithelium. The existence of rare synapses between follicular dendritic cells and nerve fibres inside the germinal centre indicates that this mechanism of neuroinvasion is possible but, since germinal centres of lymphoid follicles are poorly innervated, other routes of neuroinvasion are likely. The host PRNP genotype does not influence the pattern of innervation in these various tonsil compartments, unlike ageing during which an increase of nerve endings occurs in a zone of high trafficking cells beneath the respiratory epithelium. A minimal age-related increase of innervation inside the lymphoid follicles has also been observed. An increase in nerve fibre density around the lymphoid follicles, in an area rich in mobile cells such as macrophages and dendritic cells capable of capturing and conveying pathogen prion protein (PrPd), might ensure more efficient infectivity, not in the early phase but in the advanced phase of lymphoinvasion after the amplification of PrPd; alternatively, this area might even act as a direct site of entry during neuroinvasion.

Selective enrichment and analysis of acidic peptides and proteins using polymeric reverse micelles and MALDI-MS

The typical difficulties associated with the detection of acidic peptides (i.e., those with low isoelectric points (pI)) by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) represent a challenge in some proteomic analyses. Here, reverse micelle-forming amphiphilic homopolymers with positively charged interiors are synthesized and used to selectively enrich low pI peptides from complex mixtures for MALDI-MS detection. When using these polymers, acidic proteolytic peptides that are undetectable during normal MALDI-MS analysis are selectively detected. We show that enrichment of these low pI peptides allows acidic proteins to be selectively targeted for detection in multiprotein digests. In addition, the presence of the positively charged polymers during MALDI-MS analyses enhances peptide ion signals by almost an order of magnitude, thereby achieving reproducible ion signals for acidic peptides at concentrations as low as 100 fM. Concurrent detection of acidic and basic peptides was also facilitated by utilizing a sequential extraction process involving reverse micelle forming polymers with positively and negatively charged interiors.

Biomarker-based dissection of neurodegenerative diseases

The diagnosis of neurodegenerative diseases within neurology and psychiatry are hampered by the difficulty in getting biopsies and thereby validating the diagnosis by pathological findings. Biomarkers for other types of disease have been readily adopted into the clinical practice where for instance troponins are standard tests when myocardial infarction is suspected. However, the use of biomarkers for neurodegeneration has not been fully incorporated into the clinical routine. With the development of cerebrospinal fluid (CSF) biomarkers that reflect pathological events within the central nervous system (CNS), important clinical diagnostic tools are becoming available. This review summarizes the most promising biomarker candidates that may be used to monitor different types of neurodegeneration and protein inclusions, as well as different types of metabolic changes, in living patients in relation to the clinical phenotype and disease progression over time. Our aim is to provide the reader with an updated lexicon on currently available biomarker candidates, how far they have come in development and how well they reflect pathogenic processes in different neurodegenerative diseases. Biomarkers for specific pathogenetic processes would also be valuable tools both to study disease pathogenesis directly in patients and to identify and monitor the effect of novel treatment strategies.

Dysfunctions of neuronal and glial intermediate filaments in disease

Intermediate filaments (IFs) are abundant structures found in most eukaryotic cells, including those in the nervous system. In the CNS, the primary components of neuronal IFs are alpha-internexin and the neurofilament triplet proteins. In the peripheral nervous system, a fifth neuronal IF protein known as peripherin is also present. IFs in astrocytes are primarily composed of glial fibrillary acidic protein (GFAP), although vimentin is also expressed in immature astrocytes and some mature astrocytes. In this Review, we focus on the IFs of glial cells (primarily GFAP) and neurons as well as their relationship to different neurodegenerative diseases.