Cytoplasmic Intermediate Filaments in Cell Biology.

Intermediate filaments (IFs) are one of the three major elements of the cytoskeleton. Their stability, intrinsic mechanical properties, and cell type-specific expression patterns distinguish them from actin and microtubules. By providing mechanical support, IFs protect cells from external forces and participate in cell adhesion and tissue integrity. IFs form an extensive and elaborate network that connects the cell cortex to intracellular organelles. They act as a molecular scaffold that controls intracellular organization. However, IFs have been revealed as much more than just rigid structures. Their dynamics is regulated by multiple signaling cascades and appears to contribute to signaling events in response to cell stress and to dynamic cellular functions such as mitosis, apoptosis, and migration.

Microstructural associations between locus coeruleus, cortical, and subcortical regions are modulated by astrocyte reactivity: a 7T MRI adult lifespan study.

The locus coeruleus-norepinephrine system plays a key role in supporting brain health along the lifespan, notably through its modulatory effects on neuroinflammation. Using ultra-high field diffusion magnetic resonance imaging, we examined whether microstructural properties (neurite density index and orientation dispersion index) in the locus coeruleus were related to those in cortical and subcortical regions, and whether this was modulated by plasma glial fibrillary acidic protein levels, as a proxy of astrocyte reactivity. In our cohort of 60 healthy individuals (30 to 85 yr, 50% female), higher glial fibrillary acidic protein correlated with lower neurite density index in frontal cortical regions, the hippocampus, and the amygdala. Furthermore, under higher levels of glial fibrillary acidic protein (above ~ 150 pg/mL for cortical and ~ 145 pg/mL for subcortical regions), lower locus coeruleus orientation dispersion index was associated with lower orientation dispersion index in frontotemporal cortical regions and in subcortical regions. Interestingly, individuals with higher locus coeruleus orientation dispersion index exhibited higher orientation dispersion index in these (sub)cortical regions, despite having higher glial fibrillary acidic protein levels. Together, these results suggest that the interaction between locus coeruleus-norepinephrine cells and astrocytes can signal a detrimental or neuroprotective pathway for brain integrity and support the importance of maintaining locus coeruleus neuronal health in aging and in the prevention of age-related neurodegenerative diseases.

Compartmentalized citrullination in Muller glial endfeet during retinal degeneration.

Muller glia (MG) play a central role in reactive gliosis, a stress response associated with rare and common retinal degenerative diseases, including age-related macular degeneration (AMD). The posttranslational modification citrullination​ targeting glial fibrillary acidic protein (GFAP) in MG was initially discovered in a panocular chemical injury model. Here, we report in the paradigms of retinal laser injury, a genetic model of spontaneous retinal degeneration (JR5558 mice) and human wet-AMD tissues that MG citrullination is broadly conserved. After laser injury, GFAP polymers that accumulate in reactive MG are citrullinated in MG endfeet and glial cell processes. The enzyme responsible for citrullination, peptidyl arginine deiminase-4 (PAD4), localizes to endfeet and associates with GFAP polymers. Glial cell-specific PAD4 deficiency attenuates retinal hypercitrullination in injured retinas, indicating PAD4 requirement for MG citrullination. In retinas of 1-mo-old JR5558 mice, hypercitrullinated GFAP and PAD4 accumulate in MG endfeet/cell processes in a lesion-specific manner. Finally, we show that human donor maculae from patients with wet-AMD also feature the canonical endfeet localization of hypercitrullinated GFAP. Thus, we propose that endfeet are a "citrullination bunker" that initiates and sustains citrullination in retinal degeneration.

Aquaporin-4 deletion leads to reduced infarct volume and increased peri-infarct astrocyte reactivity in a mouse model of cortical stroke.

Aquaporin-4 (AQP4) is the main water channel in brain and is enriched in perivascular astrocyte processes abutting brain microvessels. There is a rich literature on the role of AQP4 in experimental stroke. While its role in oedema formation following middle cerebral artery occlusion (MCAO) has been studied extensively, its specific impact on infarct volume remains unclear. This study investigated the effects of total and partial AQP4 deletion on infarct volume in mice subjected to distal medial cerebral artery (dMCAO) occlusion. Compared to MCAO, this model induces smaller infarcts confined to neocortex, and less oedema. We show that AQP4 deletion significantly reduced infarct volume as assessed 1 week after dMCAO, suggesting that the role of AQP4 in stroke goes beyond its effect on oedema formation and dissolution. The reduction in infarct volume was associated with increased astrocyte reactivity in the peri-infarct areas. No significant differences were observed in the number of microglia among the genotypes. These findings provide new insights in the role of AQP4 in ischaemic injury indicating that AQP4 affects both infarct volume and astrocyte reactivity in the peri-infarct zone. KEY POINTS: Aquaporin-4 (AQP4) is the main water channel in brain and is enriched in perivascular astrocyte processes abutting microvessels. A rich literature exists on the role of AQP4 in oedema formation following middle cerebral artery occlusion (MCAO). We investigated the effects of total and partial AQP4 deletion on infarct volume in mice subjected to distal medial cerebral artery occlusion (dMCAO), a model inducing smaller infarcts confined to neocortex and less oedema compared to MCAO. AQP4 deletion significantly reduced infarct volume 1 week after dMCAO, suggesting a broader role for AQP4 in stroke beyond oedema formation. The reduction in infarct volume was associated with increased astrocyte reactivity in the peri-infarct areas, while no significant differences were observed in the number of microglia among the genotypes. These findings provide new insights into the role of AQP4 in stroke, indicating that AQP4 affects both infarct volume and astrocyte reactivity in the peri-infarct zone.

Structural flexibility and heterogeneity of recombinant human glial fibrillary acidic protein (GFAP).

Glial fibrillary acidic protein (GFAP) is a promising biomarker for brain and spinal cord disorders. Recent studies have highlighted the differences in the reliability of GFAP measurements in different biological matrices. The reason for these discrepancies is poorly understood as our knowledge of the protein's 3-dimensional conformation, proteoforms, and aggregation remains limited. Here, we investigate the structural properties of GFAP under different conditions. For this, we characterized recombinant GFAP proteins from various suppliers and applied hydrogen-deuterium exchange mass spectrometry (HDX-MS) to provide a snapshot of the conformational dynamics of GFAP in artificial cerebrospinal fluid (aCSF) compared to the phosphate buffer. Our findings indicate that recombinant GFAP exists in various conformational species. Furthermore, we show that GFAP dimers remained intact under denaturing conditions. HDX-MS experiments show an overall decrease in H-bonding and an increase in solvent accessibility of GFAP in aCSF compared to the phosphate buffer, with clear indications of mixed EX2 and EX1 kinetics. To understand possible structural interface regions and the evolutionary conservation profiles, we combined HDX-MS results with the predicted GFAP-dimer structure by AlphaFold-Multimer. We found that deprotected regions with high structural flexibility in aCSF overlap with predicted conserved dimeric 1B and 2B domain interfaces. Structural property predictions combined with the HDX data show an overall deprotection and signatures of aggregation in aCSF. We anticipate that the outcomes of this research will contribute to a deeper understanding of the structural flexibility of GFAP and ultimately shed light on its behavior in different biological matrices.

Upregulation of Integrin beta-3 in astrocytes upon Alzheimer's disease progression in the 5xFAD mouse model.

Integrins are receptors that have been linked to various brain disorders, including Alzheimer's disease (AD), the most prevalent neurodegenerative disorder. While Integrin beta-3 (ITGB3) is known to participate in multiple cellular processes such as adhesion, migration, and signaling, its specific role in AD remains poorly understood, particularly in astrocytes, the main glial cell type in the brain. In this study, we investigated alterations in ITGB3 gene and protein expression during aging in different brain regions of the 5xFAD mouse model of AD and assessed the interplay between ITGB3 and astrocytes. Primary cultures from adult mouse brains were used to gain further insight into the connection between ITGB3 and amyloid beta (Aß) in astrocytes. In vivo studies showed a correlation between ITGB3 and the astrocytic marker GFAP in the 5xFAD brains, indicating its association with reactive astrocytes. In vitro studies revealed increased gene expression of ITGB3 upon Aß treatment. Our findings underscore the potential significance of ITGB3 in astrocyte reactivity in the context of Alzheimer's disease.

NHH promotes Sepsis-associated Encephalopathy with the expression of AQP4 in astrocytes through the gut-brain Axis.

Sepsis-associated encephalopathy (SAE) is a significant cause of mortality in patients with sepsis. Despite extensive research, its exact cause remains unclear. Our previous research indicated a relationship between non-hepatic hyperammonemia (NHH) and SAE. This study aimed to investigate the relationship between NHH and SAE and the potential mechanisms causing cognitive impairment. In the in vivo experimental results, there were no significant abnormalities in the livers of mice with moderate cecal ligation and perforation (CLP); however, ammonia levels were elevated in the hippocampal tissue and serum. The ELISA study suggest that fecal microbiota transplantation in CLP mice can reduce ammonia levels. Reduction in ammonia levels improved cognitive dysfunction and neurological impairment in CLP mice through behavioral, neuroimaging, and molecular biology studies. Further studies have shown that ammonia enters the brain to regulate the expression of aquaporins-4 (AQP4) in astrocytes, which may be the mechanism underlying brain dysfunction in CLP mice. The results of the in vitro experiments showed that ammonia up-regulated AQP4 expression in astrocytes, resulting in astrocyte damage. The results of this study suggest that ammonia up-regulates astrocyte AQP4 expression through the gut-brain axis, which may be a potential mechanism for the occurrence of SAE.

4R-cembranoid suppresses glial cells inflammatory phenotypes and prevents hippocampal neuronal loss in LPS-treated mice.

Chronic neuroinflammation has been implicated in neurodegenerative disease pathogenesis. A key feature of neuroinflammation is neuronal loss and glial activation, including microglia and astrocytes. 4R-cembranoid (4R) is a natural compound that inhibits hippocampal pro-inflammatory cytokines and increases memory function in mice. We used the lipopolysaccharide (LPS) injection model to study the effect of 4R on neuronal density and microglia and astrocyte activation. C57BL/6J wild-type mice were injected with LPS (5 mg/kg) and 2 h later received either 4R (6 mg/kg) or vehicle. Mice were sacrificed after 72 h for analysis of brain pathology. Confocal images of brain sections immunostained for microglial, astrocyte, and neuronal markers were used to quantify cellular hippocampal phenotypes and neurons. Hippocampal lysates were used to measure the expression levels of neuronal nuclear protein (NeuN), inducible nitrous oxide synthase (iNOS), arginase-1, thrombospondin-1 (THBS1), glial cell-derived neurotrophic factor (GDNF), and orosomucoid-2 (ORM2) by western blot. iNOS and arginase-1 are widely used protein markers of pro- and anti-inflammatory microglia, respectively. GDNF promotes neuronal survival, and ORM2 and THBS1 are astrocytic proteins that regulate synaptic plasticity and inhibit microglial activation. 4R administration significantly reduced neuronal loss and the number of pro-inflammatory microglia 72 h after LPS injection. It also decreased the expression of the pro-inflammatory protein iNOS while increasing arginase-1 expression, supporting its anti-inflammatory role. The protein expression of THBS1, GDNF, and ORM2 was increased by 4R. Our data show that 4R preserves the integrity of hippocampal neurons against LPS-induced neuroinflammation in mice.

Glial fibrillary acidic protein, neurofilament light, matrix metalloprotease 3 and fatty acid binding protein 4 as non-invasive brain tumor biomarkers.

BACKGROUND: Gliomas are aggressive malignant tumors, with poor prognosis. There is an unmet need for the discovery of new, non-invasive biomarkers for differential diagnosis, prognosis, and management of brain tumors. Our objective is to validate four plasma biomarkers - glial fibrillary acidic protein (GFAP), neurofilament light (NEFL), matrix metalloprotease 3 (MMP3) and fatty acid binding protein 4 (FABP4) - and compare them with established brain tumor molecular markers and survival. METHODS: Our cohort consisted of patients with benign and malignant brain tumors (GBM = 77, Astrocytomas = 26, Oligodendrogliomas = 23, Secondary tumors = 35, Meningiomas = 70, Schwannomas = 15, Pituitary adenomas = 15, Normal individuals = 30). For measurements, we used ultrasensitive electrochemiluminescence multiplexed immunoassays. RESULTS: High plasma GFAP concentration was associated with GBM, low GFAP and high FABP4 were associated with meningiomas, and low GFAP and low FABP4 were associated with astrocytomas and oligodendrogliomas. NEFL was associated with progression of disease. Several prognostic genetic alterations were significantly associated with all plasma biomarker levels. We found no independent associations between plasma GFAP, NEFL, FABP4 and MMP3, and overall survival. The candidate biomarkers could not reliably discriminate GBM from primary or secondary CNS lymphomas. CONCLUSIONS: GFAP, NEFL, FABP4 and MMP3 are useful for differential diagnosis and prognosis, and are associated with molecular changes in gliomas.

Plasmatic profiles of cytokines/chemokines, glial fibrillary acidic protein (GFAP) and MRI brain damage in neonates with hypoxic ischemic encephalopathy (HIE).

BACKGROUND: Perinatal hypoxia triggers the release of cytokines and chemokines by neurons, astrocytes and microglia. In response to hypoxia-ischemia resting/ramified microglia proliferate and undergo activation, producing proinflammatory molecules. The brain damage extension seems to be related to both the severity of hypoxia and the balance between pro and anti-inflammatory response and can be explored with neuroimaging. AIMS: The aim of this preliminary study was to explore possible relationships between plasma levels of inflammatory cytokines/chemokines and the severe brain damage detectable by Magnetic Resonance Imaging (MRI), performed during the hospitalization. METHODS: In 10 full terms neonates with hypoxic ischemic encephalopathy (HIE) undergoing therapeutic hypothermia (TH), divided into cases and controls, according to MRI results, we measured and compared the plasma levels of CCL2/MCP-1, CXCL8, GFAP, IFN y, IL-10, IL-18, IL-6, CCL3, ENOLASE2, GM-CSF, IL-1b, IL-12p70, IL-33, TNFα, collected at four different time points during TH (24, 25-48, 49-72 h of life, and 7-10 days from birth). Five of enrolled babies had pathological brain MRI (cases) and 5 had a normal MRI examination (controls). Cytokines were measured by Magnetic Luminex Assay. MRI images were classified according to Barkovich's score. RESULTS: Mean levels of all cytokines and molecules at time T1 were not significantly different in the two groups. Comparing samples paired by day of collection, the greatest differences between cases and controls were found at times T2 and T3, during TH. At T4, levels tended to get closer again (except for IL-6, IL10 and IL18). Infants with worse MRI showed higher plasmatic GFAP levels than those with normal MRI, while their IL-18 was lower. The mean levels of CCL3MIP1alpha, GMCSF, IL1BETA overlapped throughout the observation period in both groups. CONCLUSION: In a small number of infants with worse brain MRI, we found higher levels of GFAP and of IL-10 at T4 and a trend toward low IL-18 levels than in infants with normal MRI, considered early biomarker of brain damage and a predictor of adverse outcome, respectively. The greatest, although not significant, difference between the levels of molecules was found in cases and controls at time points T2 and T3, during TH.

New insights into neuropathology and pathogenesis of autoimmune glial fibrillary acidic protein meningoencephalomyelitis.

Anti-glial fibrillary acidic protein (GFAP) meningoencephalomyelitis (autoimmune GFAP astrocytopathy) is a new autoimmune central nervous system (CNS) disease diagnosable by the presence of anti-GFAP autoantibodies in the cerebrospinal fluid and presents as meningoencephalomyelitis in the majority of patients. Only few neuropathological reports are available and little is known about the pathogenic mechanisms. We performed a histopathological study of two autopsies and nine CNS biopsies of patients with anti-GFAP autoantibodies and found predominantly a lymphocytic and in one autopsy case a granulomatous inflammatory phenotype. Inflammatory infiltrates were composed of B and T cells, including tissue-resident memory T cells. Although obvious astrocytic damage was absent in the GFAP-staining, we found cytotoxic T cell-mediated reactions reflected by the presence of CD8+/perforin+/granzyme A/B+ cells, polarized towards astrocytes. MHC-class-I was upregulated in reactive astrocytes of all biopsies and two autopsies but not in healthy controls. Importantly, we observed a prominent immunoreactivity of astrocytes with the complement factor C4d. Finally, we provided insight into an early phase of GFAP autoimmunity in an autopsy of a pug dog encephalitis that was characterized by marked meningoencephalitis with selective astrocytic damage with loss of GFAP and AQP4 in the lesions.Our histopathological findings indicate that a cytotoxic T cell-mediated immune reaction is present in GFAP autoimmunity. Complement C4d deposition on astrocytes could either represent the cause or consequence of astrocytic reactivity. Selective astrocytic damage is prominent in the early phase of GFAP autoimmunity in a canine autopsy case, but mild or absent in subacute and chronic stages in human disease, probably due to the high regeneration potential of astrocytes. The lymphocytic and granulomatous phenotypes might reflect different stages of lesion development or patient-specific modifications of the immune response. Future studies will be necessary to investigate possible implications of pathological subtypes for clinical disease course and therapeutic strategies.

MENIN-mediated regulation of gastrin gene expression and its role in gastrinoma development.

The Multiple Endocrine Neoplasia I (MEN1) locus encodes the protein MENIN, which functions as a tumor suppressor protein in neuroendocrine tissues. Gastrinomas are neuroendocrine neoplasms that overproduce the hormone gastrin and can arise sporadically or as part of the MEN1 syndrome, in which mutations in the MEN1 gene lead to loss or inactivation of MENIN protein. Gastrin is a peptide hormone that is primarily synthesized in the gastric antrum and stimulates the secretion of histamine from enterochromaffin-like (ECL) cells and subsequently acid from parietal cells in the gastric corpus. In addition, gastrin exerts a mitogenic function primarily on ECL cells and progenitor cells in the gastric isthmus. Current studies seek to understand how MEN1 mutations generate a mutant MENIN protein that abrogates its tumor suppressor function. Mutations in the MEN1 gene are broadly distributed throughout its nine protein-coding exons, making it difficult to correlate protein structure with its function. Although disruption of the Men1 locus in mice causes functional neuroendocrine tumors in the pituitary and pancreas, gastrinomas do not develop in these transgenic animal models. Prior studies of human gastrinomas suggest that tissue-specific microenvironmental cues in the submucosal foregut may contribute to tumorigenesis by reprogramming of epithelial cells toward the neuroendocrine phenotype. Accordingly, recent studies suggest that neural crest-derived cells are also sensitive to reprogramming when MEN1 is deleted or mutated. Thus, the goal of this report is to review our current understanding of how MENIN modulates gastrin gene expression while highlighting its role in the prevention/suppression of neuroendocrine cell transformation.

Changes in Astroglial Water Flow in the Pre-amyloid Phase of the STZ Model of AD Dementia.

Alzheimer's disease (AD) is an age-dependent neurodegenerative disease that is typically sporadic and has a high social and economic cost. We utilized the intracerebroventricular administration of streptozotocin (STZ), an established preclinical model for sporadic AD, to investigate hippocampal astroglial changes during the first 4 weeks post-STZ, a period during which amyloid deposition has yet to occur. Astroglial proteins aquaporin 4 (AQP-4) and connexin-43 (Cx-43) were evaluated, as well as claudins, which are tight junction (TJ) proteins in brain barriers, to try to identify changes in the glymphatic system and brain barrier during the pre-amyloid phase. Glial commitment, glucose hypometabolism and cognitive impairment were characterized during this phase. Astroglial involvement was confirmed by an increase in glial fibrillary acidic protein (GFAP); concurrent proteolysis was also observed, possibly mediated by calpain. Levels of AQP-4 and Cx-43 were elevated in the fourth week post-STZ, possibly accelerating the clearance of extracellular proteins, since these proteins actively participate in the glymphatic system. Moreover, although we did not see a functional disruption of the blood-brain barrier (BBB) at this time, claudin 5 (present in the TJ of the BBB) and claudin 2 (present in the TJ of the blood-cerebrospinal fluid barrier) were reduced. Taken together, data support a role for astrocytes in STZ brain damage, and suggest that astroglial dysfunction accompanies or precedes neuronal damage in AD.

Exploring Astrocytes Involvement and Glutamate Induced Neuroinflammation in Chlorpyrifos-Induced Paradigm Of Autism Spectrum Disorders (ASD).

Autism spectrum disorders (ASD) are neurodevelopmental disorders manifested mainly in children, with symptoms ranging from social/communication deficits and stereotypies to associated behavioral anomalies like anxiety, depression, and ADHD. While the patho-mechanism is not well understood, the role of neuroinflammation has been suggested. Nevertheless, the triggers giving rise to this neuroinflammation have not previously been explored in detail, so the present study was aimed at exploring the role of glutamate on these processes, potentially carried out through increased activity of inflammatory cells like astrocytes, and a decline in neuronal health. A novel chlorpyrifos-induced paradigm of ASD in rat pups was used for the present study. The animals were subjected to tests assessing their neonatal development and adolescent behaviors (social skills, stereotypies, sensorimotor deficits, anxiety, depression, olfactory, and pain perception). Markers for inflammation and the levels of molecules involved in glutamate excitotoxicity, and neuroinflammation were also measured. Additionally, the expression of reactive oxygen species and markers of neuronal inflammation (GFAP) and function (c-Fos) were evaluated, along with an assessment of histopathological alterations. Based on these evaluations, it was found that postnatal administration of CPF had a negative impact on neurobehavior during both the neonatal and adolescent phases, especially on developmental markers, and brought about the generation of ASD-like symptoms. This was further corroborated by elevations in the expression of glutamate and downstream calcium, as well as certain cytokines and neuroinflammatory markers, and validated through histopathological and immunohistochemical results showing a decline in neuronal health in an astrocyte-mediated cytokine-dependent fashion. Through our findings, conclusive evidence regarding the involvement of glutamate in neuroinflammatory pathways implicated in the development of ASD-like symptoms, as well as its ability to activate further downstream processes linked to neuronal damage has been obtained. The role of astrocytes and the detrimental effect on neuronal health are also concluded. The significance of our study and its findings lies in the evaluation of the involvement of chlorpyrifos-induced neurotoxicity in the development of ASD, particularly in relation to glutamatergic dysfunction and neuronal damage.

Co-occurrence of glial fibrillary acidic protein astrocytopathy in a patient with Leber's hereditary optic neuropathy due to DNAJC30 mutations.

Leber's hereditary optic neuropathy (LHON) is a mitochondrial disease characterized by visual loss, and rarely associated with extraocular manifestations including multiple sclerosis-like lesions. The association of LHON and neuromyelitis optica spectrum disorders has rarely been reported. Here is reported a case of glial fibrillary acidic protein astrocytopathy presenting with area postrema syndrome in a patient with previously diagnosed recessive LHON due to mutations in the nuclear gene DNAJC30. This case emphasizes the necessity of extensive investigations for other treatable conditions in patients with LHON and otherwise unexplained extraocular involvement and the possibility that also visual symptoms can respond to immune therapy.

Clinical and neuroimaging phenotypes of autoimmune glial fibrillary acidic protein astrocytopathy: A systematic review and meta-analysis.

OBJECTIVE: This study was undertaken to provide a comprehensive review of neuroimaging characteristics and corresponding clinical phenotypes of autoimmune glial fibrillary acidic protein astrocytopathy (GFAP-A), a rare but severe neuroinflammatory disorder, to facilitate early diagnosis and appropriate treatment. METHODS: A PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis)-conforming systematic review and meta-analysis was performed on all available data from January 2016 to June 2023. Clinical and neuroimaging phenotypes were extracted for both adult and paediatric forms. RESULTS: A total of 93 studies with 681 cases (55% males; median age = 46, range = 1-103 years) were included. Of these, 13 studies with a total of 535 cases were eligible for the meta-analysis. Clinically, GFAP-A was often preceded by a viral prodromal state (45% of cases) and manifested as meningitis, encephalitis, and/or myelitis. The most common symptoms were headache, fever, and movement disturbances. Coexisting autoantibodies (45%) and neoplasms (18%) were relatively frequent. Corticosteroid treatment resulted in partial/complete remission in a majority of cases (83%). Neuroimaging often revealed T2/fluid-attenuated inversion recovery (FLAIR) hyperintensities (74%) as well as perivascular (45%) and/or leptomeningeal (30%) enhancement. Spinal cord abnormalities were also frequent (49%), most commonly manifesting as longitudinally extensive myelitis. There were 88 paediatric cases; they had less prominent neuroimaging findings with lower frequencies of both T2/FLAIR hyperintensities (38%) and contrast enhancement (19%). CONCLUSIONS: This systematic review and meta-analysis provide high-level evidence for clinical and imaging phenotypes of GFAP-A, which will benefit the identification and clinical workup of suspected cases. Differential diagnostic cues to distinguish GFAP-A from common clinical and imaging mimics are provided as well as suitable magnetic resonance imaging protocol recommendations.

Integrated Assessment of GFAP and UCH-L1 for their utility in severity assessment and outcome prediction in Traumatic Brain Injury.

OBJECTIVES: This study aimed to explore the potential of glial fibrillary acidic protein (GFAP) and ubiquitin C-terminal hydrolase-L1 (UCH-L1) as biomarkers for diagnosis and prognosis in mild and severe TBI cases, including TBI-related deaths. METHODS: This prospective cohort study includes 40 cases each of mild, severe, fatal TBI cases, and 40 healthy controls. Serum samples were collected from live patients at 8 and 20 h post injury for UCH-L1 and GFAP respectively, and from deceased patients within 6 h of death. RESULTS: Elevated levels of both GFAP and UCH-L1 were observed in patients with severe and fatal TBI cases. These biomarkers exhibited promising potential for predicting various Glasgow Outcome Scale Extended (GOSE) categories. Combining GFAP and UCH-L1 yielded higher predictive accuracy both for diagnosis and prognosis in TBI cases. The study additionally established specific cut-off levels for GFAP and UCH-L1 stratified according to the severity and prognosis. CONCLUSION: GFAP and UCH-L1 individually demonstrated moderate to good discrimination capacity in predicting TBI severity and functional outcomes. However, combining these biomarkers is recommended for improved diagnostic and prognostic utility. This precision tool can enhance patient care, enabling tailored treatment plans, ultimately reducing morbidity and mortality rates in TBI cases.

Delivery of miR-15b-5p via magnetic nanoparticle-enhanced bone marrow mesenchymal stem cell-derived extracellular vesicles mitigates diabetic osteoporosis by targeting GFAP.

Diabetic osteoporosis (DO) presents significant clinical challenges. This study aimed to investigate the potential of magnetic nanoparticle-enhanced extracellular vesicles (GMNPE-EVs) derived from bone marrow mesenchymal stem cells (BMSCs) to deliver miR-15b-5p, thereby targeting and downregulating glial fibrillary acidic protein (GFAP) expression in rat DO models. Data was sourced from DO-related RNA-seq datasets combined with GEO and GeneCards databases. Rat primary BMSCs, bone marrow-derived macrophages (BMMs), and osteoclasts were isolated and cultured. EVs were separated, and GMNPE targeting EVs were synthesized. Bioinformatic analysis revealed a high GFAP expression in DO-related RNA-seq and GSE26168 datasets for disease models. Experimental results confirmed elevated GFAP in rat DO bone tissues, promoting osteoclast differentiation. miR-15b-5p was identified as a GFAP inhibitor, but was significantly downregulated in DO and enriched in BMSC-derived EVs. In vitro experiments showed that GMNPE-EVs could transfer miR-15b-5p to osteoclasts, downregulating GFAP and inhibiting osteoclast differentiation. In vivo tests confirmed the therapeutic potential of this approach in alleviating rat DO. Collectively, GMNPE-EVs can effectively deliver miR-15b-5p to osteoclasts, downregulating GFAP expression, and hence, offering a therapeutic strategy for rat DO.

Incidental Gliosis in the Central Nervous System of Control Nonhuman Primates and Rats.

Gliosis, including microgliosis and astrocytosis, can be challenging to interpret in nonclinical studies. Incidences of glial foci in brains and spinal cords of control rats and nonhuman primates (NHPs) were reviewed in the historical control databases from two contract research organizations, including one specializing in neuropathology. In the brain, minimal to mild (grades 1-2) microgliosis was the most common diagnosis, especially in NHPs, although occasional moderate or marked microgliosis (grades 3 and 4) was encountered in both species. Microgliosis was more common in the cerebral cortex, cerebellum, and medulla oblongata in both species and was frequent in the white matter (brain), thalamus, and basal nuclei of NHPs. Gliosis ("not otherwise specified") of minimal severity was diagnosed in similar brain sub-sites for both species and was more common in NHPs compared with rats. Astrocytosis was most prominent in the cerebellum (molecular layer) of NHPs but was otherwise uncommon. In the spinal cord, microgliosis was most common in the lateral white matter tracts in rats and NHPs, and in the dorsal white matter tracts in NHPs. These data indicate that low-grade spontaneous glial responses occur with some frequency in control animals of two common nonclinical species.

Quantification of blood glial fibrillary acidic protein using a second-generation microfluidic assay. Validation and comparative analysis with two established assays.

OBJECTIVES: Increased levels of glial fibrillary acidic protein (GFAP) in blood have been identified as a valuable biomarker for some neurological disorders, such as Alzheimer's disease and multiple sclerosis. However, most blood GFAP quantifications so far were performed using the same bead-based assay, and to date a routine clinical application is lacking. METHODS: In this study, we validated a novel second-generation (2nd gen) Ella assay to quantify serum GFAP. Furthermore, we compared its performance with a bead-based single molecule array (Simoa) and a homemade GFAP assay in a clinical cohort of neurological diseases, including 210 patients. RESULTS: Validation experiments resulted in an intra-assay variation of 10 %, an inter-assay of 12 %, a limit of detection of 0.9 pg/mL, a lower limit of quantification of 2.8 pg/mL, and less than 20 % variation in serum samples exposed to up to five freeze-thaw cycles, 120 h at 4 °C and room temperature. Measurement of the clinical cohort using all assays revealed the same pattern of GFAP distribution in the different diagnostic groups. Moreover, we observed a strong correlation between the 2nd gen Ella and Simoa (r=0.91 (95 % CI: 0.88-0.93), p<0.0001) and the homemade immunoassay (r=0.77 (95 % CI: 0.70-0.82), p<0.0001). CONCLUSIONS: Our results demonstrate a high reliability, precision and reproducibility of the 2nd gen Ella assay. Although a higher assay sensitivity for Simoa was observed, the new microfluidic assay might have the potential to be used for GFAP analysis in daily clinical workups due to its robustness and ease of use.