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Background Receptor-mediated transcytosis is one of the major routes for drug delivery of large molecules into the brain. The aim of this study was to develop a novel model of the human blood–brain barrier (BBB) in a high-throughput microfluidic device. This model can be used to assess passage of large biopharmaceuticals, such as therapeutic antibodies, across the BBB. Methods The model comprises human cell lines of brain endothelial cells, astrocytes, and pericytes in a two-lane or three-lane microfluidic platform that harbors 96 or 40 chips, respectively, in a 384-well plate format. In each chip, a perfused vessel of brain endothelial cells was grown against an extracellular matrix gel, which was patterned by means of surface tension techniques. Astrocytes and pericytes were added on the other side of the gel to complete the BBB on-a-chip model. Barrier function of the model was studied using fluorescent barrier integrity assays. To test antibody transcytosis, the lumen of the model’s endothelial vessel was perfused with an anti-transferrin receptor antibody or with a control antibody. The levels of antibody that penetrated to the basal compartment were quantified using a mesoscale discovery assay. Results The perfused BBB on-a-chip model shows presence of adherens and tight junctions and severely limits the passage of a 20 kDa FITC-dextran dye. Penetration of the antibody targeting the human transferrin receptor (MEM-189) was markedly higher than penetration of the control antibody (apparent permeability of 2.9 × 10 −5 versus 1.6 × 10 −5  cm/min, respectively). Conclusions We demonstrate successful integration of a human BBB microfluidic model in a high-throughput plate-based format that can be used for drug screening purposes. This in vitro model shows sufficient barrier function to study the passage of large molecules and is sensitive to differences in antibody penetration, which could support discovery and engineering of BBB-shuttle technologies.

Blood–brain barrier (BBB) dysfunction is a key feature in neuroimmunological and neurodegenerative diseases. In this study, we developed a microfluidic human BBB-on-a-chip to model barrier dysfunction and immune cell migration using immortalized TY10 brain endothelial cells, pericytes, and astrocytes. It was found that immortalized TY10 brain endothelial cells developed a microvascular structure under flow. Pericytes were localized on the basal side surrounding the TY10 microvascular structure, showing an in vivo-like structure. Barrier integrity increased under co-culture with pericytes. In addition, both ethylenediaminetetraacetic acid (EDTA) and anti-Claudin-5 (CLDN5) neutralizing antibody caused a decrease in the transendothelial electrical resistance (TEER). EDTA caused the leakage of 20 kDa dextran, suggesting different effects on the BBB based on the mechanism of action, whereas anti-CLDN5 antibody did not cause leakage. In the tri-culture model, human T cells migrated through endothelial vessels towards basal C-X-C motif chemokine ligand 12 (CXCL12). The live-imaging analysis confirmed the extravasation of fluorescence-labelled T cells in a CXCL12-concentration- and time-dependent manner. Our BBB model had an in vivo-like structure and successfully represented barrier dysfunction and transendothelial T cell migration. In addition, our study suggests that the inhibition of CLDN5 attenuates the BBB in humans. This platform has various potential uses in relation to the BBB in both drug discovery research and in elucidating the mechanisms of central nervous system diseases.

The blood–brain barrier (BBB) acts as a structural and functional barrier for brain homeostasis. This review highlights the pathological contribution of BBB dysfunction to neuroimmunological diseases, including multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), autoimmune encephalitis (AE), and paraneoplastic neurological syndrome (PNS). The transmigration of massive lymphocytes across the BBB caused by the activation of cell adhesion molecules is involved in the early phase of MS, and dysfunction of the cortical BBB is associated with the atrophy of gray matter in the late phase of MS. At the onset of NMOSD, increased permeability of the BBB causes the entry of circulating AQP4 autoantibodies into the central nervous system (CNS). Recent reports have shown the importance of glucose-regulated protein (GRP) autoantibodies as BBB-reactive autoantibodies in NMOSD, which induce antibody-mediated BBB dysfunction. BBB breakdown has also been observed in MOGAD, NPSLE, and AE with anti-NMDAR antibodies. Our recent report demonstrated the presence of GRP78 autoantibodies in patients with MOGAD and the molecular mechanism responsible for GRP78 autoantibody-mediated BBB impairment. Disruption of the BBB may explain the symptoms in the brain and cerebellum in the development of PNS, as it induces the entry of pathogenic autoantibodies or lymphocytes into the CNS through autoimmunity against tumors in the periphery. GRP78 autoantibodies were detected in paraneoplastic cerebellar degeneration and Lambert–Eaton myasthenic syndrome, and they were associated with cerebellar ataxia with anti-P/Q type voltage-gated calcium channel antibodies. This review reports that therapies affecting the BBB that are currently available for disease-modifying therapies for neuroimmunological diseases have the potential to prevent BBB damage.

Biological mediators secreted during peripheral chronic inflammation reach the bloodstream and may damage the blood–brain barrier (BBB), triggering central nervous system (CNS) disorders. Full-fledged human BBB models are efficient tools to investigate pharmacological pathways and mechanisms of injury at the BBB. We here employed a human in vitro BBB model to investigate the effects of either plasma from inflammatory bowel disease (IBD) patients or tumor necrosis factor α (TNFα), a cytokine commonly released in periphery during IBD, and the anti-inflammatory role of pioglitazone, a peroxisome proliferator-activated receptor γ agonist (PPARγ). The BBB model was treated with either 10% plasma from healthy and IBD donors or 5 ng/mL TNFα, following treatment with 10 µM pioglitazone. Patient plasma did not alter BBB parameters, but TNFα levels in plasma from all donors were associated with varying expression of claudin-5, claudin-3 and ICAM-1. TNFα treatment increased BBB permeability, claudin-5 disarrangement, VCAM-1 and ICAM-1 expression, MCP1 secretion and monocyte transmigration. These effects were attenuated by pioglitazone. Plasma from IBD patients, which evoked higher BBB permeability, also increased ICAM-1 expression, this effect being reversed by pioglitazone. Our findings evidence how pioglitazone controls periphery-elicited BBB inflammation and supports its repurposing for prevention/treating of such inflammatory conditions.

We describe here the design and implementation of an microvascular open model system using human brain microvascular endothelial cells. The design has several advantages over other traditional closed microfluidic platforms: (1) it enables controlled unidirectional flow of media at physiological rates to support vascular function, (2) it allows for very small volumes which makes the device ideal for studies involving biotherapeutics, (3) it is amenable for multiple high resolution imaging modalities such as transmission electron microscopy (TEM), 3D live fluorescence imaging using traditional spinning disk confocal microscopy, and advanced lattice light sheet microscopy (LLSM). Importantly, we miniaturized the design, so it can fit within the physical constraints of LLSM, with the objective to study physiology in live cells at subcellular level. We validated barrier function of our brain microvessel-on-a-chip by measuring permeability of fluorescent dextran and a human monoclonal antibody. One potential application is to investigate mechanisms of transcytosis across the brain microvessel-like barrier of fluorescently-tagged biologics, viruses or nanoparticles.

Immune checkpoint inhibitors (ICIs) are a cornerstone of systemic therapy for clear cell renal cell carcinoma (ccRCC), yet response rates remain variable and predictive biomarkers are lacking. This study aimed to determine whether baseline levels of myeloid-derived suppressor cells (MDSCs), especially monocytic (M-MDSC) and polymorphonuclear (PMN-MDSC) subtypes, could predict ICI response in ccRCC patients. In this prospective cohort study, 20 ccRCC patients receiving ICI-based therapy for at least 3 months were enrolled. Peripheral blood mononuclear cells were collected before and after treatment to quantify total MDSCs, M-MDSCs, and PMN-MDSCs via flow cytometry. Additional clinical variables, including blood cell counts and metabolic profiles, were assessed. Elastic net regression identified key variables associated with treatment response. Multivariable logistic regression was used to evaluate their predictive value. The primary outcome was objective response (CR/PR) based on RECIST 1.1. Among 47 clinical and laboratory variables with an area under the curve (AUC) greater than 0.6, elastic net regression identified 7 key predictors of immunotherapy response. Notably, higher baseline levels of monocytic MDSCs (M-MDSCs) and their proportion within total MDSCs were independently associated with objective response to immune checkpoint inhibitors (OR = 3.082, p = 0.041 and OR = 5.764, p = 0.036, respectively). Following treatment, responders exhibited a significant decline in circulating M-MDSC levels, whereas non-responders did not. Baseline circulating M-MDSC levels and their relative proportion within total MDSCs may serve as potential predictive biomarkers for response to immune checkpoint inhibitors in ccRCC patients. These findings highlight the role of MDSCs in modulating immunotherapy efficacy and suggest their clinical utility in guiding personalized treatment strategies.

Cell-based therapeutic strategies have been proposed as an alternative for brain and blood vessels repair after stroke, but their clinical application is hampered by potential adverse effects. We therefore tested the hypothesis that secretome of these cells might be used instead to still focus on cell-based therapeutic strategies. We therefore characterized the composition and the effect of the secretome of brain microvascular endothelial cells (BMECs) on primary in vitro human models of angiogenesis and vascular barrier. Two different secretome batches produced in high scale (scHSP) were analysed by mass spectrometry. Human primary CD34 + -derived endothelial cells (CD34 + -ECs) were used as well as in vitro models of EC monolayer (CMECs) and blood–brain barrier (BBB). Cells were also exposed to oxygen–glucose deprivation (OGD) conditions and treated with scHSP during reoxygenation. Protein yield and composition of scHSP batches showed good reproducibility. scHSP increased CD34 + -EC proliferation, tubulogenesis, and migration. Proteomic analysis of scHSP revealed the presence of growth factors and proteins modulating cell metabolism and inflammatory pathways. scHSP improved the integrity of CMECs, and upregulated the expression of junctional proteins. Such effects were mediated through the activation of the interferon pathway and downregulation of Wnt signalling. Furthermore, OGD altered the permeability of both CMECs and BBB, while scHSP prevented the OGD-induced vascular leakage in both models. These effects were mediated through upregulation of junctional proteins and regulation of MAPK/VEGFR2. Finally, our results highlight the possibility of using secretome from BMECs as a therapeutic alternative to promote brain angiogenesis and to protect from ischemia-induced vascular leakage.

ObjectiveIn neuromyelitis optica (NMO), the destruction of the blood–brain barrier (BBB) has been considered to be the first step of the disease process. It is unclear whether sera from patients with NMO can open the BBB, and which component of patient sera is most important for this disruption.MethodsThe effects of sera from antiaquaporin4 (AQP4) antibody positive NMO patients, multiple sclerosis patients and control subjects were evaluated for expression of tight junction proteins and for transendothelial electrical resistance (TEER) of human brain microvascular endothelial cells (BMECs). Whether antibodies against human BMECs as well as anti-AQP4 antibodies exist in NMO sera was also examined using western blot analysis.ResultsExpression of tight junction proteins and TEER in BMECs was significantly decreased after exposure to NMO sera. However, this effect was reversed after application of an antivascular endothelial growth factor (VEGF) neutralising antibody. Antibodies against BMECs other than anti-AQP4 antibodies were found in the sera of NMO patients whereas no specific bands were detected in the sera of healthy and neurological controls. These antibodies apparently disrupt the BBB by increasing the autocrine secretion of VEGF by BMECs themselves. Absorption of the anti-AQP4 antibody by AQP4 transfected astrocytes reduced AQP4 antibody titres but was not associated with a reduction in BBB disruption.ConclusionsSera from NMO patients reduce expression of tight junction proteins and disrupt the BBB. Autoantibodies against BMECs other than anti-AQP4 antibodies may disrupt the BBB through upregulation of VEGF in BMECs.

Myeloid-derived suppressor cell (MDSC) exhibits immunosuppressive functions and affects cancer progression, but its relationship with prostate cancer remains unclear. We elucidated the association of polymorphonuclear MDSC (PMN-MDSC) and monocytic MDSC (M-MDSC) levels of the total peripheral blood mononuclear cells (PBMCs) with prostate cancer progression and evaluated their roles as prognostic indicators. We enrolled 115 patients with non-metastatic hormone-sensitive prostate cancer (nmHSPC, n = 62), metastatic hormone-sensitive prostate cancer (mHSPC, n = 23), and metastatic castration-resistant prostate cancer (mCRPC, n = 30). Subsequently, the proportions of MDSCs in each disease progression were compared. Log-rank tests and multivariate Cox regression analyses were performed to ascertain the associations of overall survival. The patients with mCRPC had significantly higher PMN-MDSC percentage than those with nmHSPC and mHSPC (P = 7.73 × 10 and 0.0014). Significantly elevated M-MDSC levels were observed in mCRPC patients aged <70 years (P = 0.016) and with a body mass index (BMI) <25 kg/m (P = 0.043). The high PMN-MDSC group had notably shorter median survival duration (159 days) than the low PMN-MDSC group (768 days, log-rank P = 0.018). In the multivariate analysis including age, BMI, and MDSC subset, PMN-MDSC was significantly associated with prognosis (hazard ratios, 3.48; 95% confidence interval: 1.05-11.56, P = 0.042). PMN-MDSC levels are significantly associated with mCRPC prognosis. Additionally, we highlight the remarkable associations of age and BMI with M-MDSC levels in mCRPC, offering novel insights into MDSC dynamics in prostate cancer progression.

The destruction of blood–brain barrier (BBB) and blood-nerve barrier (BNB) has been considered to be a key step in the disease process of a number of neurological disorders including cerebral ischemia, Alzheimer’s disease, multiple sclerosis, and diabetic neuropathy. Although glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) facilitate neuronal or axonal regeneration in the brain or peripheral nerves, their action in the BBB and BNB remains unclear. The purpose of the present study was to elucidate whether these neurotrophic factors secreted from the brain or peripheral nerve pericytes increase the barrier function of the BBB or BNB, using our newly established human brain microvascular endothelial cell (BMEC) line or peripheral nerve microvascular endothelial cell (PnMEC) line. GDNF increased the expression of claudin-5 and the transendothelial electrical resistance (TEER) of BMECs and PnMECs, whereas BDNF did not have this effect. Furthermore, we herein demonstrate that the GDNF secreted from the brain and peripheral nerve pericytes was one of the key molecules responsible for the up-regulation of claudin-5 expression and the TEER value in the BBB and BNB. These results indicate that the regulation of GDNF secreted from pericytes may therefore be a novel therapeutic strategy to modify the BBB or BNB functions and promote brain or peripheral nerve regeneration.