[Peripheral Neuropathy in Eosinophilic Granulomatosis with Polyangiitis].

Eosinophilic granulomatosis with polyangiitis (EGPA) is an antineutrophil cytoplasmic autoantibody-associated vasculitis secondary to inflammation of the small vessels. EGPA-induced neuropathy develops in approximately 90% of patients with peripheral blood eosinophilia and may lead to serious complications of the peripheral nervous system, necessitating emergency therapeutic intervention.

Physician awareness and understanding of chronic inflammatory demyelinating polyradiculoneuropathy in Japan: a web-based study.

OBJECTIVES: To investigate potential knowledge gaps between neurologists and non-specialists and identify challenges in the current management of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), with a focus on 'early diagnosis' and 'appropriate treatment' for CIDP. DESIGN: A non-interventional, cross-sectional, web-based quantitative survey of physicians working in healthcare clinics or hospitals in Japan. SETTING: Participants were recruited from the Nikkei Business Publications panel from 18 August to 14 September 2022. PARTICIPANTS: Responses from 360 physicians (120 each of internists, orthopaedists and neurologists) were collected. OUTCOME MEASURES: Responses relating to a CIDP hypothetical case and current understanding were assessed to determine awareness, collaboration preferences and diagnosis and treatment decisions. RESULTS: Understanding of CIDP was 90.8% among neurologists, 10.8% among orthopaedists and 13.3% among internists; >80% of orthopaedists and internists answered that neurologists are preferable for treatment. Diagnostic assessment using a hypothetical case showed 95.0% of neurologists, 74.2% of orthopaedists and 72.5% of internists suspected CIDP. Among orthopaedists and internists suspecting CIDP, >70% considered referring to neurology, while ~10% considered continuing treatment without a referral. Among neurologists, 69.4% chose intravenous immunoglobulin (IVIg) as first-line treatment and determined effectiveness to be ≤3 months. CONCLUSIONS: Orthopaedists and internists had lower CIDP awareness compared with neurologists, which may lead to inadequate referrals to neurology. Evaluation of IVIg effectiveness for maintenance therapy occurred earlier than the guideline recommendations (6-12 months), risking premature discontinuation. Improving CIDP knowledge among orthopaedists and internists is critical for better diagnosis and collaboration with neurologists. Neurologists should consider slow and careful evaluation of IVIg maintenance therapy. TRIAL REGISTRATION NUMBER: UMIN000048516.

Lead Encephalopathy in a 73-year-old Man Manifesting as Acute Disturbance of Consciousness with a Unique Magnetic Resonance Imaging Appearance.

A 73-year-old man was admitted with Cheyne-Stokes respiration and progressive disturbance of consciousness over the course of a month. Cranial magnetic resonance imaging revealed signs suggestive of angioedema in the posterior limb of the internal capsule, external capsule, and subcortical white matter. Acute lead encephalopathy was diagnosed based on abnormally high plasma lead levels. After methylprednisolone pulse therapy followed by chelation therapy, the patient fully recovered. In this case, the angioedema with a distinctive magnetic resonance imaging appearance was attributed to the cytotoxic effects of lead on the nervous system, which responded well to methylprednisolone pulse therapy.

LONRF2 is a protein quality control ubiquitin ligase whose deficiency causes late-onset neurological deficits.

Protein misfolding is a major factor of neurodegenerative diseases. Post-mitotic neurons are highly susceptible to protein aggregates that are not diluted by mitosis. Therefore, post-mitotic cells may have a specific protein quality control system. Here, we show that LONRF2 is a bona fide protein quality control ubiquitin ligase induced in post-mitotic senescent cells. Under unperturbed conditions, LONRF2 is predominantly expressed in neurons. LONRF2 binds and ubiquitylates abnormally structured TDP-43 and hnRNP M1 and artificially misfolded proteins. Lonrf2-/- mice exhibit age-dependent TDP-43-mediated motor neuron (MN) degeneration and cerebellar ataxia. Mouse induced pluripotent stem cell-derived MNs lacking LONRF2 showed reduced survival, shortening of neurites and accumulation of pTDP-43 and G3BP1 after long-term culture. The shortening of neurites in MNs from patients with amyotrophic lateral sclerosis is rescued by ectopic expression of LONRF2. Our findings reveal that LONRF2 is a protein quality control ligase whose loss may contribute to MN degeneration and motor deficits.

[Mechanism of Synthesis and Effect of Autoantibodies: Implications for Therapy].

The detailed mechanisms of autoantibody synthesis are different in each disease; however, the dysfunction of immune tolerance is attracting interest as the common mechanism in many autoantibody-associated diseases. Autoantibodies must pass through various physiological barriers, such as the blood-brain barrier, to approach their antigen in the central nervous system. The direct effects of autoantibodies on their antigens vary among antibodies. Exploring the detailed mechanism of synthesis and effect of autoantibodies would provide a more radical and effective therapeutic strategy.

Jo-1 Antibodies From Myositis Induce Complement-Dependent Cytotoxicity and TREM-1 Upregulation in Muscle Endothelial Cells.

BACKGROUND AND OBJECTIVES: Muscle microangiopathy due to dysfunction of endothelial cells because of inflammation is a critical hallmark of dermatomyositis (DM); however, its pathomechanism remains unclear. The aim of this study was to evaluate the effect of immunogloblin G (IgG) from patients with idiopathic inflammatory myopathies (IIM) on muscle endothelial cells in vitro. METHODS: Using a high-content imaging system, we analyzed whether IgG purified from sera from patients with IIM (n = 15), disease controls (DCs: n = 7), and healthy controls (HCs: n = 7) can bind to muscle endothelial cells and induce complement-dependent cellular cytotoxicity. RESULTS: IgGs from Jo-1 antibody myositis could bind to muscle endothelial cells and caused complement-dependent cell cytotoxicity. RNA-seq demonstrated the upregulation of genes associated with tumor necrosis factor (TNF)-α, triggering receptor expressed on myeloid cells-1 (TREM-1), CD25, and mitochondria pathways after exposure to IgG from the Jo-1, signal recognition particle (SRP), and polymyositis (PM) groups. The high-content imaging system showed that TREM-1 expression in the Jo-1, SRP, and PM groups was increased in comparison with DCs and HCs and that the TNF-α expression in the Jo-1 group was higher in comparison with the SRP, PM, DC, and HC groups. The expression of TREM-1 was observed in biopsied capillaries and the muscle membrane from patients with Jo-1 and in biopsied muscle fiber and capillaries from patients with DM and SRP. The depletion of Jo-1 antibodies by IgG of patients with Jo-1 antibody myositis reduced the Jo-1 antibody-induced complement-dependent cellular cytotoxicity in muscle endothelial cells. DISCUSSION: Jo-1 antibodies from Jo-1 antibody myositis show complement-dependent cellular cytotoxicity in muscle endothelial cells. IgGs from patients with Jo-1, SRP, and DM increase the TREM-1 expression in endothelial cells and muscles.

Autocrine TNF-α Increases Penetration of Myelin-Associated Glycoprotein Antibodies Across the Blood-Nerve Barrier in Anti-MAG Neuropathy.

BACKGROUND AND OBJECTIVES: Deposition of myelin-associated glycoprotein (MAG) immunoglobulin M (IgM) antibodies in the sural nerve is a key feature in anti-MAG neuropathy. Whether the blood-nerve barrier (BNB) is disrupted in anti-MAG neuropathy remains elusive.We aimed to evaluate the effect of sera from anti-MAG neuropathy at the molecular level using our in vitro human BNB model and observe the change of BNB endothelial cells in the sural nerve of anti-MAG neuropathy. METHODS: Diluted sera from patients with anti-MAG neuropathy (n = 16), monoclonal gammopathies of undetermined significance (MGUS) neuropathy (n = 7), amyotrophic lateral sclerosis (ALS, n = 10), and healthy controls (HCs, n = 10) incubated with human BNB endothelial cells to identify the key molecule of BNB activation using RNA-seq and a high-content imaging system, and exposed with a BNB coculture model to evaluate small molecule/IgG/IgM/anti-MAG antibody permeability. RESULTS: RNA-seq and the high-content imaging system showed the significant upregulation of tumor necrosis factor (TNF-α) and nuclear factor-kappa B (NF-κB) in BNB endothelial cells after exposure to sera from patients with anti-MAG neuropathy, whereas the serum TNF-α concentration was not changed among the MAG/MGUS/ALS/HC groups. Sera from patients with anti-MAG neuropathy did not increase 10-kDa dextran or IgG permeability but enhanced IgM and anti-MAG antibody permeability. Sural nerve biopsy specimens from patients with anti-MAG neuropathy showed higher TNF-α expression levels in BNB endothelial cells and preservation of the structural integrity of the tight junctions and the presence of more vesicles in BNB endothelial cells. Neutralization of TNF-α reduces IgM/anti-MAG antibody permeability. DISCUSSION: Sera from individuals with anti-MAG neuropathy increased transcellular IgM/anti-MAG antibody permeability via autocrine TNF-α secretion and NF-κB signaling in the BNB.

Glomerulonephritis and Interstitial Nephritis Originating from Vasculitis of the Interlobular Arteries of the Kidney in a Patient with Eosinophilic Granulomatosis with Polyangiitis.

Eosinophilic granulomatosis with polyangiitis (EGPA) is a type of antineutrophil cytoplasmic antibody-associated vasculitis. Patients often present with peripheral neuropathy and purpura, suggesting impairment of small vessels, especially capillaries. However, medium-sized vessels and small vessels with a vascular diameter larger than that of capillaries may also be impaired, causing atypical findings. We report a case of EGPA treated with corticosteroids, cyclophosphamide, and mepolizumab. Renal biopsy revealed vasculitis of the interlobular arteries as the cause of glomerulonephritis and interstitial nephritis. This case suggests the importance of considering vessels upstream of capillaries dominant EGPA as a differential diagnosis in patients with eosinophilia.

An In Vitro Model of the Blood-Brain Barrier to Study Alzheimer's Disease: The Role of ß-Amyloid and Its Influence on PBMC Infiltration.

The blood-brain barrier (BBB) is a highly specialized structure, constituted by endothelial cells that together with astrocytes and pericytes provide a functional interface between the central nervous system and the periphery. Several pathological conditions may affect its functions, and lately BBB involvement in the pathogenesis of Alzheimer's disease has been demonstrated. Both endothelial cells and astrocytes can be differentially affected during the course of the disease. In vitro BBB models present a powerful tool in evaluating the effects that ß-amyloid (Aß), or other pathogenic stimuli, play on the BBB at cellular level. In vitro BBB models derived from human cell sources are rare and not easily implemented. We generated two conditionally immortalized human cell lines, brain microvascular endothelial cells (TY10), and astrocytes (hAST), that, when co-cultured under appropriate conditions, exhibit BBB-like characteristics. This model allowed us to evaluate the transmigration of peripheral blood mononuclear cells (PBMCs) through the in vitro barrier exposed to Aß and the role played by astrocytes in the modulation of this phenomenon. We describe here the methodology used in our lab to set up our in vitro model of the BBB and to carry out a PBMC transmigration assay.

[Steroids-Resistant EGPA-Induced Neuropathy with Acute Disease Progression: How to Select Remission-Induction/Maintenance Therapy Based on The Characteristics].

Recently, given the availability of mepolizumab as a novel treatment for eosinophilic polyangiitis granulomatosis (EGPA), several studies on remission-induction/maintenance therapies are in progress. However, there is little evidence regarding the treatment of EGPA neuropathy. In this article, we clarify the characteristics of steroid-resistant EGPA neuropathy by presenting actual cases and explaining the selection of remission-induction/maintenance therapies based on the characteristics.

Spinal cord sarcoidosis in Japan: utility of cerebrospinal fluid examination and nerve conduction study for diagnosis and prognosis prediction.

Spinal cord sarcoidosis (SCS) is rare, and its diagnosis is challenging. We examined clinical, laboratory, and imaging features in patients with SCS to obtain useful clues for diagnosis and prognosis. Eleven consecutive patients (four males, seven females) at a single Japanese institution were investigated. Median age at onset was 66 years old. The most frequent site affected, other than the nervous system, was the respiratory system. While histological confirmation of non-caseating granulomas was often found there, no patient had respiratory symptoms. Peripheral nerve involvement was detected in 64% of patients. Soluble IL-2 receptor (sIL-2R) levels in serum and cerebrospinal fluid (CSF) were elevated in 64% and 45% of patients, respectively, and this finding was more common than elevation of angiotensin-converting enzyme (ACE). 18F-fluorodeoxyglucose (FDG) positron emission tomography showed abnormally high uptake in spinal lesions of all examined patients. Although corticosteroids were administrated to all patients, and immuno-suppressants were prescribed to six (55%), the modified Rankin Scale was unchanged or worsened in four (36%) patients during the follow-up period. Neurological exacerbation of myelopathy was seen in four (36%) patients. Complete response rate was only seen in 9%. High levels of cell count, protein, ACE, and sIL-2R in CSF were significantly more frequent in patients with a marked improvement after immunotherapy than in the other patients. These results suggest that high serum and CSF sIL-2R, high uptake of FDG, and peripheral nerve involvement are indicative of SCS. Given that SCS is commonly intractable, CSF abnormalities may predict efficacy of immunotherapies.

[Clinical and long-term characteristics of the subtypes of chronic inflammatory demyelinating polyneuropathy].

OBJECTIVE: To clarify the clinical and long-term characteristic of each subtype of chronic inflammatory demyelinating polyneuropathy (CIDP). METHODS: We evaluated data from 30 consecutive CIDP patients who met the criteria proposed by the European Federation of Neurological Societies and the Peripheral Nerve Society. RESULTS: Patients were classified as having typical CIDP (t-|CIDP) (10/30, 33%), multifocal acquired demyelinating sensory and motor (MADSAM) (12/30, 40%), DADS (4/30, 13%), sensory CIDP (3/30, 10%) or motor CIDP (1/30, 3%). Nerve conduction studies showed more prolonged distal motor latencies/F-wave latencies and slower motor nerve conduction in the typical CIDP group than in the MADSAM group. Intravenous immunoglobulin (IVIg) was effective in 80% (8/10) of t-|CIDP, 100% (12/12) of MADSAM, 100% (4/4) of DADS, and 100% (3/3) of sensory CIDP cases. Maintenance therapy with immunoglobulin was administered in patients with t-|CIDP (5/10, 50%), MADSAM (9/12, 75%), DADS (1/4, 25%), and sensory CIDP (2/3, 67%). There were no patients with CIDP, in whom CIDP subtype was transformed from the initial diagnosis during five years of follow-up. DISCUSSION: Percentage of MADSAM was the most common phenotype in our cohort of CIDP patients, and IVIg/immunoglobulin maintenance was effective for MADSAM as well as t-|CIDP in contrast to findings from the previous reports.

[An 11 year old woman with myelin-oligodendrocyte glycoprotein antibody showing various phenotypes of central nervous system disorders in one year].

An 11-year-old woman with myelin-oligodendrocyte glycoprotein (MOG) antibody developed cortical encephalitis twice, followed by acute disseminated encephalomyelitis (ADEM) and optic neuritis in one year. Although optic neuritis was refractory after corticosteroid therapy, plasma exchange was effective and complete remission was achieved. We considered that episodes of cortical encephalitis, ADEM and optic neuritis occurred in the present patient can be included in MOG IgG-associated disorders. Also, we recommend plasma exchange for refractory MOG IgG-associated optic neuritis, even in pediatric patient.

GRP78 Antibodies Are Associated With Blood-Brain Barrier Breakdown in Anti-Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disorder.

BACKGROUND AND OBJECTIVES: To analyze (1) the effect of immunoglobulin G (IgG) from patients with anti-myelin oligodendrocyte glycoprotein antibody (MOG-Ab)-associated disorder on the blood-brain barrier (BBB) endothelial cells and (2) the positivity of glucose-regulated protein 78 (GRP78) antibodies in MOG-Ab-associated disorders. METHODS: IgG was purified from sera with patients with MOG-Ab-associated disorder in the acute phase (acute MOG, n = 15), in the stable stage (stable MOG, n = 14), healthy controls (HCs, n = 9), and disease controls (DCs, n = 27). Human brain microvascular endothelial cells (BMECs) were incubated with IgG, and the number of nuclear NF-κB p65-positive cells in BMECs using high-content imaging system and the quantitative messenger RNA change in gene expression over the whole transcriptome using RNA-seq were analyzed. GRP78 antibodies from patient IgGs were detected by Western blotting. RESULTS: IgG in the acute MOG group significantly induced the nuclear translocation of NF-κB and increased the vascular cell adhesion molecule 1/intercellular adhesion molecule 1 expression/permeability of 10-kDa dextran compared with that from the stable MOG and HC/DC groups. RNA-seq and pathway analysis revealed that NF-κB signaling and oxidative stress (NQO1) play key roles. The NQO1 and Nrf2 protein amounts were significantly decreased after exposure to IgG in the acute MOG group. The rate of GRP78 antibody positivity in the acute MOG group (10/15, 67% [95% confidence interval, 38%-88%]) was significantly higher than that in the stable MOG group (5/14, 36% [13%-65%]), multiple sclerosis group (4/29, 14% [4%-32%]), the DCs (3/27, 11% [2%-29%]), or HCs (0/9, 0%). Removal of GRP78 antibodies from MOG-IgG reduced the effect on NF-κB nuclear translocation and increased permeability. DISCUSSION: GRP78 antibodies may be associated with BBB dysfunction in MOG-Ab-associated disorder.

Exploring lipophilic compounds that induce BDNF secretion in astrocytes beyond the BBB using a new multi-cultured human in vitro BBB model.

Brain-derived neurotrophic factor (BDNF) cannot cross the blood-brain barrier (BBB) when administered peripherally, which hinders its therapeutic potential. We utilized an in vitro BBB model-a tri-culture of a human endothelial cell line, a pericyte cell line, and an astrocyte cell line-to study the effect of twenty candidate lipophilic compounds on stimulating BDNF secretion in pericytes and astrocytes. The prostaglandin E2 receptor 4 agonist and sphingosine-1-phosphate receptor 5 agonist facilitated secretion of BDNF in the astrocyte, but did not decrease the transendothelial electrical resistance. These compounds may be promising agents for neurodegenerative and neuroinflammatory diseases.

New BBB Model Reveals That IL-6 Blockade Suppressed the BBB Disorder, Preventing Onset of NMOSD.

BACKGROUND AND OBJECTIVES: To evaluate the pathophysiology of neuromyelitis optica spectrum disorder (NMOSD) and the therapeutic mechanism and levels of interleukin-6 (IL-6) blockade (satralizumab), especially with respect to blood-brain barrier (BBB) disruption with the new in vitro and ex vivo human BBB models and in vivo model. METHODS: We constructed new static in vitro and flow-based ex vivo models for evaluating continued barrier function, leukocyte transmigration, and intracerebral transferability of neuromyelitis optica-immunoglobulin G (NMO-IgG) and satralizumab across the BBB using the newly established triple coculture system that are specialized to closely mimic endothelial cell contact of pericytes and endfeet of astrocytes. In the in vivo study, we assessed the effects of an anti-IL-6 receptor antibody for mice (MR16-1) on in vivo BBB disruption in mice with experimental autoimmune encephalomyelitis in which IL-6 concentration in the spinal cord dramatically increases. RESULTS: In vitro and ex vivo experiments demonstrated that NMO-IgG increased intracerebral transferability of satralizumab and NMO-IgG and that satralizumab suppressed the NMO-IgG-induced transmigration of T cells and barrier dysfunction. In the in vivo study, the blockade of IL-6 signaling suppressed the migration of T cells into the spinal cord and prevented the increased BBB permeability. DISCUSSION: These results suggest that (1) our triple-cultured in vitro and in ex vivo BBB models are ideal for evaluating barrier function, leukocyte transmigration, and intracerebral transferability; (2) NMO-IgG increased the intracerebral transferability of NMO-IgG via decreasing barrier function and induced secretion of IL-6 from astrocytes causing more dysfunction of the barrier and disrupting controlled cellular infiltration; and (3) satralizumab, which can pass through the BBB in the presence of NMO-IgG, suppresses the BBB dysfunction and the infiltration of inflammatory cells, leading to prevention of onset of NMOSD.

[Neuropathy presenting conduction block in ANCA-negative eosinophilic granulomatosis with polyangiitis].

A 74-year-old woman with a history of asthma and allergic rhinitis rapidly developed multiple mononeuropathy. Although anti-neutrophil cytoplasmic antibodies were negative, the presence of eosinophilia and eosinophilic infiltrations in the sural nerve led to a diagnosis of eosinophilic granulomatosis with polyangiitis. A motor nerve conduction study on admission revealed conduction block, which promptly disappeared after initiating immunotherapy without findings suggestive for remyelination or axonal degeneration. This electrophysiological change distinct from that of Wallerian degeneration. A biopsy of the sural nerve showed many eosinophil infiltrations and degranulation of eosinophilic cationic protein within nerve fascicles, whereas findings of necrotizing vasculitis were absent. These findings suggest that a direct effect of eosinophilic cationic protein, rather than ischemic damage due to vasculitis, was the main mechanism of transient nerve conduction failure in this patient.

[Primary Central Nervous System Vasculitis].

Primary central nervous system (CNS) vasculitis is an uncommon disorder of unknown etiology that is restricted to the brain and spinal cord. Patients do not present with specific clinical features or a classical clinical course, and no blood or imaging investigations are available for diagnostic confirmation. Cerebral biopsy and angiography are the gold standards for diagnosis. No randomized clinical trials have described a therapeutic regimen effective for primary CNS vasculitis; therefore, treatment of primary CNS vasculitis is based on therapeutic strategies used for other types of vasculitis. Early diagnosis is important because corticosteroid-based treatment with or without concomitant cyclophosphamide administration can often prevent serious outcomes and may be followed by a favorable response. Several immunosuppressants such as mycophenolate mofetil, tumor necrosis factor-α blockers, and rituximab may be useful options for patients refractory to the aforementioned regimen. We describe some diagnostic and therapeutic approaches for the management of this condition, with a focus on the importance of obtaining tissue and angiographic evaluation (formal contrast-enhanced or magnetic resonance/computed tomography angiography).

HLA genotype-clinical phenotype correlations in multiple sclerosis and neuromyelitis optica spectrum disorders based on Japan MS/NMOSD Biobank data.

HLA genotype-clinical phenotype correlations are not established for multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD). We studied HLA-DRB1/DPB1 genotype-phenotype correlations in 528 MS and 165 NMOSD cases using Japan MS/NMOSD Biobank materials. HLA-DRB1*04:05, DRB1*15:01 and DPB1*03:01 correlated with MS susceptibility and DRB1*01:01, DRB1*09:01, DRB1*13:02 and DPB1*04:01 were protective against MS. HLA-DRB1*15:01 was associated with increased optic neuritis and cerebellar involvement and worsened visual and pyramidal functional scale (FS) scores, resulting in higher progression index values. HLA-DRB1*04:05 was associated with younger onset age, high visual FS scores, and a high tendency to develop optic neuritis. HLA-DPB1*03:01 increased brainstem and cerebellar FS scores. By contrast, HLA-DRB1*01:01 decreased spinal cord involvement and sensory FS scores, HLA-DRB1*09:01 decreased annualized relapse rate, brainstem involvement and bowel and bladder FS scores, and HLA-DRB1*13:02 decreased spinal cord and brainstem involvement. In NMOSD, HLA-DRB1*08:02 and DPB1*05:01 were associated with susceptibility and DRB1*09:01 was protective. Multivariable analysis revealed old onset age, long disease duration, and many relapses as independent disability risks in both MS and NMOSD, and HLA-DRB1*15:01 as an independent risk only in MS. Therefore, both susceptibility and protective alleles can influence the clinical manifestations in MS, while such genotype-phenotype correlations are unclear in NMOSD.

Blood-Nerve Barrier (BNB) Pathology in Diabetic Peripheral Neuropathy and In Vitro Human BNB Model.

In diabetic peripheral neuropathy (DPN), metabolic disorder by hyperglycemia progresses in peripheral nerves. In addition to the direct damage to peripheral neural axons, the homeostatic mechanism of peripheral nerves is disrupted by dysfunction of the blood-nerve barrier (BNB) and Schwann cells. The disruption of the BNB, which is a crucial factor in DPN development and exacerbation, causes axonal degeneration via various pathways. Although many reports revealed that hyperglycemia and other important factors, such as dyslipidemia-induced dysfunction of Schwann cells, contributed to DPN, the molecular mechanisms underlying BNB disruption have not been sufficiently elucidated, mainly because of the lack of in vitro studies owing to difficulties in establishing human cell lines from vascular endothelial cells and pericytes that form the BNB. We have developed, for the first time, temperature-sensitive immortalized cell lines of vascular endothelial cells and pericytes originating from the BNB of human sciatic nerves, and we have elucidated the disruption to the BNB mainly in response to advanced glycation end products in DPN. Recently, we succeeded in developing an in vitro BNB model to reflect the anatomical characteristics of the BNB using cell sheet engineering, and we established immortalized cell lines originating from the human BNB. In this article, we review the pathologic evidence of the pathology of DPN in terms of BNB disruption, and we introduce the current in vitro BNB models.