Choroid Epithelium Research Articles

Intravitreal Metformin Protects Against Choroidal Neovascularization and Light-Induced Retinal Degeneration.

Neovascular age-related macular degeneration (nAMD), a leading cause of blindness in older adults, presents a challenging pathophysiology involving choroidal neovascularization (CNV) and retinal degeneration. Current treatments relying on intravitreal (IVT) administration of anti-angiogenic agents are costly and of moderate effectiveness. Metformin, the common anti-diabetic drug, has been associated with decreased odds of developing AMD. Studies have shown that metformin can mitigate cellular aging, neoangiogenesis, and inflammation across multiple diseases. This preclinical study assessed metformin's impact on vessel growth using choroidal explants before exploring IVT metformin's effects on laser-induced CNV and light-induced retinal degeneration in C57BL/6J and BALB/cJ mice, respectively. Metformin reduced new vessel growth in choroidal explants in a dose-dependent relationship. Following laser induction, IVT metformin suppressed CNV and decreased peripheral infiltration of IBA1+ macrophages/microglia. Furthermore, IVT metformin protected against retinal thinning in response to light-induced degeneration. IVT metformin downregulated genes in the choroid and retinal pigment epithelium which are associated with angiogenesis and inflammation, two key processes that drive nAMD progression. These findings underscore metformin's capacity as an anti-angiogenic and neuroprotective agent, demonstrating this drug's potential as an accessible option to help manage nAMD.

Two-year follow-up of a post-traumatic choroidal rupture with a lens luxation patient: a case report

Background: A choroidal rupture is a break in the choroid, Bruch membrane, and retinal pigment epithelium (RPE) that occurs most commonly as a result of blunt ocular trauma. It may be a secondary effect of direct or indirect trauma. This case illustrates an indirect post-traumatic choroidal rupture with lens luxation. Three months following the incident, the patient presented with impaired vision. The posterior segment was found to have a luxated lens during the objective examination of the eye. The funduscopy revealed a white, curvilinear, crescent-shaped streak that was concentric to the optic nerve. Case description: A 45-year-old male from East Java visited the ophthalmology outpatient clinic with a chief complaint of blurred vision in the left eye for three months, followed by pain in the left eye. On examination, the visual acuity was a one-meter counting finger. The lens was luxated to the posterior. The funduscopy examination revealed a curvilinear crescent-shaped streak. Vitrectomy and lensectomy were implemented. After four months of aphakia, the patient underwent a scleral fixation intraocular lens (IOL) implantation. The visual acuity was satisfactory, and no complications were observed during the two-year follow-up. Conclusion: We reported a post-traumatic choroidal rupture and a lens luxation with an optimal outcome after a two-year follow-up.

THE ORGANIZATION OF THE BASEMENT MEMBRANES IN THE CHOROID PLEXUS VILLI OF THE HUMAN BRAIN

THE ORGANIZATION OF THE BASEMENT MEMBRANES IN THE Choroid PLEXUS VILLI OF THE HUMAN BRAIN Authors O.V. Kirik 1*, O.S. Alekseeva 1,2, I.P. Grigorev 1, E.A. Fedorova 1, A.A. Beketova 1, D.E. Korzhevsky 1 Affiliation 1 Institute of Experimental Medicine, Saint Petersburg, Russian Federation 2 Sechenov Institute of Evolutionary Physiology and Biochemistry of the Russian Academy of Sciences, Saint Petersburg, Russian Federation Abstract BACKGROUND: The choroid plexus of the brain is the main component of the blood-cerebrospinal fluid barrier, separating these two biological fluids. Basement membranes of the choroid plexus have a special role in the implementation of barrier functions: they underlie the choroidal epithelium and capillary endothelium, and serve as an additional filter for substances penetrating from the blood into the cerebrospinal fluid. AIM: The purpose of this work was to study the organization of basement membranes in the villi of the human telencephalon choroid plexus using immunohistochemical detection of type IV collagen. METHODS: The study was performed on archival material from the choroid plexus of the human brain (age 29-50 years, n=10) using the immunohistochemical method for detecting type IV collagen. RESULTS: An immunohistochemical reaction using antibodies to type IV collagen showed the distribution of this protein in the subepithelial area and in the stroma of the choroid plexus villi. All immunopositive structures had clear contours; there was no reaction in the cell cytoplasm or a nonspecific background. Contacts of subepithelial and subcapillary basement membranes labeled with antibodies to type IV collagen were not detected. CONCLUSION: The study showed that the basement membranes of the villi of the choroid plexus of the human brain in the subepithelial and perivascular areas have a different organization. In this case, the union of the subepithelial and perivascular components containing type IV collagen, as a rule, does not occur.

RETINAL STRUCTURAL CHANGES AFTER CESSATION OF PENTOSAN POLYSULFATE SODIUM.

To quantify baseline and longitudinal structural changes post-cessation in patients with pentosan polysulfate sodium retinopathy. This is a retrospective cohort study. Retinal thickness and volume of choroidal and hyperreflective retinal pigment epithelium excrescences were manually segmented from optical coherence tomography volume scans. Baseline measurements were compared against age-matched control subjects. Longitudinal measurements were performed on patients with follow-up data. Twenty-four eyes of 13 patients were included. At baseline, the mean total retinal thickness was lower in the pentosan polysulfate sodium retinopathy cohort than in age- and sex-matched control subjects (269.1 µ m vs. 290.2 µ m, P = 0.006). The median (range) of follow-up was 18.6 (4.1-34.7) months, with the mean last follow-up of 35.2 months after cessation. During the follow-up period, the thickness of the retina decreased significantly by 11.3 µ m (CI: 16.8, 5.8) ( P < 0.001), with an annual mean decrease of 6.70 µ m. However, the mean hyperreflective retinal pigment epithelium excrescence volume did not change significantly ( P = 0.140) over the follow-up period. After pentosan polysulfate sodium discontinuation, although retinal pigment epithelium excrescence volume do not change significantly, there continues to be a progressive long-term thinning of the retina, which continues at a rate greater than that associated with normal aging. Consequently, long-term follow-up is suggested to monitor patients with pentosan polysulfate sodium retinopathy.

Multimodal Imaging in Diagnosis of Vogt Koyanagi Harada Disease with Reference to Choroid and Retinal Pigment Epithelium

A 48 year dark skinned North Indian male presented first time to our outpatient with history of bilateral visual decline of 3 weeks duration with associated features of headache, myalgia and rhinitus of 4 weeks duration. A detailed examination confirmed bilateral active anterior granulomatous uveitis with bilateral disc oedema with serous retinal detachment. Multimodal imaging examination was carried out with nideks mirante. Diagnosis in favour of vogt koyanagi harada disease was confirmed. The posterior segment was assessed for various changes in acute and remission phase of vogt koyanagi harada disease with fundus fluorescein angiography, fundus autoflourescence, retroillumination and optical coherence tomography. Thickness and structural change related to central macula thickness, retinal pigment epithelium and choroid were assessed pre and post treatment with additional support of optical coherence tomography and retroillumination. Both these techniques were able to document a greater value change pre and post treatment in these structures. Hence we conclude the need to include these techniques in retinal pigment epithelium and choroidal assessment in vogt koyanagi harada disease.

Single-cell analysis of mesenchymal cells in permeable neural vasculature reveals novel diverse subpopulations of fibroblasts

BackgroundIn the choroid plexus and pituitary gland, vasculature is known to have a permeable, fenestrated phenotype which allows for the free passage of molecules in contrast to the blood brain barrier observed in the rest of the CNS. The endothelium of these compartments, along with secretory, neural-lineage cells (choroid epithelium and pituitary endocrine cells) have been studied in detail, but less attention has been given to the perivascular mesenchymal cells of these compartments.MethodsThe Hic1CreERT2 Rosa26LSL−TdTomato mouse model was used in conjunction with a PdgfraH2B−EGFP mouse model to examine mesenchymal cells, which can be subdivided into Pdgfra+ fibroblasts and Pdgfra− pericytes within the choroid plexus (CP) and pituitary gland (PG), by histological, immunofluorescence staining and single-cell RNA-sequencing analyses.ResultsWe found that both CP and PG possess substantial populations of distinct Hic1+ mesenchymal cells, including an abundance of Pdgfra+ fibroblasts. Within the pituitary, we identified distinct subpopulations of Hic1+ fibroblasts in the glandular anterior pituitary and the neurosecretory posterior pituitary. We also identified multiple distinct markers of CP, PG, and the meningeal mesenchymal compartment, including alkaline phosphatase, indole-n-methyltransferase and CD34.ConclusionsNovel, distinct subpopulations of mesenchymal cells can be found in permeable vascular interfaces, including the CP, PG, and meninges, and make distinct contributions to both organs through the production of structural proteins, enzymes, transporters, and trophic molecules.

Breast-to-brain metastasis is exacerbated with chemotherapy through blood-cerebrospinal fluid barrier and induces Alzheimer's-like pathology.

Control of breast-to-brain metastasis remains an urgent unmet clinical need. While chemotherapies are essential in reducing systemic tumor burden, they have been shown to promote non-brain metastatic invasiveness and drug-driven neurocognitive deficits through the formation of neurofibrillary tangles (NFT), independently. Now, in this study, we investigated the effect of chemotherapy on brain metastatic progression and promoting tumor-mediated NFT. Results show chemotherapies increase brain-barrier permeability and facilitate enhanced tumor infiltration, particularly through the blood-cerebrospinal fluid barrier (BCSFB). This is attributed to increased expression of matrix metalloproteinase 9 (MMP9) which, in turn, mediates loss of Claudin-6 within the choroid plexus cells of the BCSFB. Importantly, increased MMP9 activity in the choroid epithelium following chemotherapy results in cleavage and release of Tau from breast cancer cells. This cleaved Tau forms tumor-derived NFT that further destabilize the BCSFB. Our results underline for the first time the importance of the BCSFB as a vulnerable point of entry for brain-seeking tumor cells post-chemotherapy and indicate that tumor cells themselves contribute to Alzheimer's-like tauopathy.

Transcriptomic analysis of the ocular posterior segment completes a cell atlas of the human eye

Although the visual system extends through the brain, most vision loss originates from defects in the eye. Its central element is the neural retina, which senses light, processes visual signals, and transmits them to the rest of the brain through the optic nerve (ON). Surrounding the retina are numerous other structures, conventionally divided into anterior and posterior segments. Here, we used high-throughput single-nucleus RNA sequencing (snRNA-seq) to classify and characterize cells in six extraretinal components of the posterior segment: ON, optic nerve head (ONH), peripheral sclera, peripapillary sclera (PPS), choroid, and retinal pigment epithelium (RPE). Defects in each of these tissues are associated with blinding diseases-for example, glaucoma (ONH and PPS), optic neuritis (ON), retinitis pigmentosa (RPE), and age-related macular degeneration (RPE and choroid). From ~151,000 single nuclei, we identified 37 transcriptomically distinct cell types, including multiple types of astrocytes, oligodendrocytes, fibroblasts, and vascular endothelial cells. Our analyses revealed a differential distribution of many cell types among distinct structures. Together with our previous analyses of the anterior segment and retina, the data presented here complete a "Version 1" cell atlas of the human eye. We used this atlas to map the expression of >180 genes associated with the risk of developing glaucoma, which is known to involve ocular tissues in both anterior and posterior segments as well as the neural retina. Similar methods can be used to investigate numerous additional ocular diseases, many of which are currently untreatable.

The phosphoproteome of choroid plexus epithelial cells following infection with Neisseria meningitidis.

The Gram-negative bacterium Neisseria meningitidis, which causes meningitis in humans, has been demonstrated to manipulate or alter host signalling pathways during infection of the central nervous system (CNS). However, these complex signalling networks are not completely understood. We investigate the phosphoproteome of an in vitro model of the blood-cerebrospinal fluid barrier (BCSFB) based on human epithelial choroid plexus (CP) papilloma (HIBCPP) cells during infection with the N. meningitidis serogroup B strain MC58 in presence and absence of the bacterial capsule. Interestingly, our data demonstrates a stronger impact on the phosphoproteome of the cells by the capsule-deficient mutant of MC58. Using enrichment analyses, potential pathways, molecular processes, biological processes, cellular components and kinases were determined to be regulated as a consequence of N. meningitidis infection of the BCSFB. Our data highlight a variety of protein regulations that are altered during infection of CP epithelial cells with N. meningitidis, with the regulation of several pathways and molecular events only being detected after infection with the capsule-deficient mutant. Mass spectrometry proteomics data are available via ProteomeXchange with identifier PXD038560.

Punctate Inner Choroidopathy in a Young Filipino Female: A Case Report

A 30-year-old, monocular myopic female consulted for new onset scotoma on her left eye. Best corrected visualacuity was 20/20 for the left eye. Fundus exam revealed a hypopigmented lesion in the inferior juxtafoveal areawith no overlying vitreous reaction/opacity. Spectral domain optical coherence tomography (SD-OCT) showedfocal disruption and elevation of the inner choroid and retinal pigment epithelium (RPE), indicating punctate inner choroidopathy (PIC). OCT angiography (OCT-A) revealed the presence of a choroidal neovascular membrane (CNV) on RPE-RPE fit segmentation. The CNV and lesion resolved upon treatment with one intravitreal bevacizumab injection and oral prednisone 60 mg (1.2 mg/kg body weight) per day tapering over 2 months.This is the first reported case of PIC in a Filipino that was diagnosed and treated with the guidance of high-resolution SD-OCT and OCT-A. These diagnostic tests proved useful in identifying the lesions based on cross-sectional views of the retina, RPE and choroid.

Single-cell RNA sequencing reveals transcriptional changes of human choroidal and retinal pigment epithelium cells during fetal development, in healthy adult and intermediate age-related macular degeneration.

Age-related macular degeneration (AMD) is the most prevalent cause of blindness in the developed world. Vision loss in the advanced stages of the disease is caused by atrophy of retinal photoreceptors, overlying retinal pigment epithelium (RPE) and choroidal endothelial cells. The molecular events that underline the development of these cell types from in utero to adult as well as the progression to intermediate and advanced stages AMD are not yet fully understood. We performed single-cell RNA-sequencing (RNA-Seq) of human fetal and adult RPE-choroidal tissues, profiling in detail all the cell types and elucidating cell type-specific proliferation, differentiation and immunomodulation events that occur up to midgestation. Our data demonstrate that progression from the fetal to adult state is characterized by an increase in expression of genes involved in the oxidative stress response and detoxification from heavy metals, suggesting a better defence against oxidative stress in the adult RPE-choroid tissue. Single-cell comparative transcriptional analysis between a patient with intermediate AMD and an unaffected subject revealed a reduction in the number of RPE cells and melanocytes in the macular region of the AMD patient. Together these findings may suggest a macular loss of RPE cells and melanocytes in the AMD patients, but given the complex processing of tissues required for single-cell RNA-Seq that is prone to technical artefacts, these findings need to be validated by additional techniques in a larger number of AMD patients and controls.

Genetic deficiency and pharmacological modulation of RORα regulate laser-induced choroidal neovascularization.

Choroidal neovascularization (CNV) causes acute vision loss in neovascular age-related macular degeneration (AMD). Genetic variations of the nuclear receptor RAR-related orphan receptor alpha (RORα) have been linked with neovascular AMD, yet its specific role in pathological CNV development is not entirely clear. In this study, we showed that Rora was highly expressed in the mouse choroid compared with the retina, and genetic loss of RORα in Staggerer mice (Rorasg/sg) led to increased expression levels of Vegfr2 and Tnfa in the choroid and retinal pigment epithelium (RPE) complex. In a mouse model of laser-induced CNV, RORα expression was highly increased in the choroidal/RPE complex post-laser, and loss of RORα in Rorasg/sg eyes significantly worsened CNV with increased lesion size and vascular leakage, associated with increased levels of VEGFR2 and TNFα proteins. Pharmacological inhibition of RORα also worsened CNV. In addition, both genetic deficiency and inhibition of RORα substantially increased vascular growth in isolated mouse choroidal explants ex vivo. RORα inhibition also promoted angiogenic function of human choroidal endothelial cell culture. Together, our results suggest that RORα negatively regulates pathological CNV development in part by modulating angiogenic response of the choroidal endothelium and inflammatory environment in the choroid/RPE complex.

Choroid plexus imaging to track neuroinflammation - a translational model for mouse and human studies.

Choroid plexus imaging to track neuroinflammation - a translational model for mouse and human studies.

Syndromic Cherry – Goldberg Cotlier syndrome

The cherry-red spot in typical central retinal artery occlusion occurs because of the reddish color of the vascular choroid and retinal pigment epithelium seen through the foveola while the adjacent inner retina is opacified. We report a case of a bilateral pseudo-cherry-red spot in association with conjunctival telangiectasia and corneal posterior stromal clouding.

Do Choroidal Melanocytes Affect Choroidal Thickness in Patients with Newly Diagnosed Vitiligo?

Aim: Vitiligo is a chronic skin disease and considered to be an autoimmune, neural, and autocytotoxic&#x0D; pathophysiology in which mainly the melanocytes in the epidermis are focused and destroyed.&#x0D; Therefore, alterations in the choroid and retinal pigment epithelium are expected, and there are very&#x0D; few publications using modern technology in research of this subject.&#x0D; This study aimed to examine the optic disc, retinal nerve fiber layer (RNFL), and choroidal thickness&#x0D; in patients with vitiligo by spectral-domain optical coherence tomography (SD-OCT) as a prospective&#x0D; observational study.&#x0D; Material and Methods: This single-center prospective cross-sectional study included 40 eyes of 40&#x0D; patients with vitiligo and 42 eyes of 42 healthy individuals. The RNFL thickness, choroidal thickness,&#x0D; and optic disc parameters (rim area, disc area, and cup volume) were compared between the two&#x0D; groups.&#x0D; Results: The study consisted of 21 female and 19 male in the vitiligo group, and 21 female and 21&#x0D; male in controls; no difference was found in gender distribution between two groups (p=0.836). Vitiligo&#x0D; and control groups had similar optic disc parameters, and RNFL and choroidal thicknesses; so the&#x0D; differences in the mentioned parameters did not differ statistically (p&gt;0.05 for all).&#x0D; Conclusion: Vitiligo patients’ optic disc parameters, and RNFL and choroidal thicknesses did not differ&#x0D; from those in healthy individuals. Based on unknown pathogenesis, the melanocytes at the choroidal&#x0D; region may have compensatory mechanisms in vitiligo.

CNSC-02. BREAST TO BRAIN METASTASIS IS EXACERBATED WITH CHEMOTHERAPY THROUGH BLOOD-CEREBRAL SPINAL FLUID-BARRIER AND INDUCES ALZHEIMER’S-LIKE PATHOLOGY

Abstract Control of breast to brain metastasis remains an urgent unmet clinical need. While chemotherapies are essential in reducing systemic tumor burden, they have also shown to promote non-brain metastatic invasiveness and drug-driven neurocognitive deficits through formation of neurofibrillary tangles (NFT) independently. Now, in this study we investigated the effect of chemotherapy on brain metastatic progression and promoting tumor-mediated NFT. Results show chemotherapies promote increased brain-barrier permeability and facilitate enhanced tumor infiltration, particularly through the blood-cerebrospinal fluid-barrier (BCSFB). This is attributed to increased expression of matrix metalloproteinase 9 (MMP9) which, in turn, mediates loss of Claudin-6 within the choroid plexus cells of the BCSFB. Importantly, increased MMP9 activity in the choroid epithelium following chemotherapy results in cleavage of Tau released from breast cancer cells. This cleaved Tau forms tumor-derived NFT that further destabilize the BCSFB. Our results underline for the first time the importance of the BCSFB as a vulnerable point of entry for brain-seeking tumor cells post-chemotherapy and indicate that tumor cells themselves contribute to Alzheimer’s-like tauopathy.

BSCI-12 BREAST TO BRAIN METASTASIS IS EXACERBATED WITH CHEMOTHERAPY THROUGH BLOOD-CEREBRAL SPINAL FLUID-BARRIER AND INDUCES ALZHEIMER’S-LIKE PATHOLOGY

Abstract Control of breast to brain metastasis remains an urgent unmet clinical need. While chemotherapies are essential in reducing systemic tumor burden, they have also shown to promote non-brain metastatic invasiveness and drug-driven neurocognitive deficits through formation of neurofibrillary tangles (NFT) independently. Now, in this study we investigated the effect of chemotherapy on brain metastatic progression and promoting tumor-mediated NFT. Results show chemotherapies promote increased brain-barrier permeability and facilitate enhanced tumor infiltration, particularly through the blood-cerebrospinal fluid-barrier (BCSFB). This is attributed to increased expression of matrix metalloproteinase 9 (MMP9) which, in turn, mediates loss of Claudin-6 within the choroid plexus cells of the BCSFB. Importantly, increased MMP9 activity in the choroid epithelium following chemotherapy results in cleavage of Tau released from breast cancer cells. This cleaved Tau forms tumor-derived NFT that further destabilize the BCSFB. Our results underline for the first time the importance of the BCSFB as a vulnerable point of entry for brain-seeking tumor cells post-chemotherapy and indicate that tumor cells themselves contribute to Alzheimer’s-like tauopathy.

Nuclear Receptor Atlases of Choroidal Tissues Reveal Candidate Receptors Associated with Age-Related Macular Degeneration.

The choroid is a vulnerable tissue site in the eye, impacted in several blinding diseases including age related macular degeneration (AMD), which is the leading cause of central vision loss in the aging population. Choroidal thinning and choriocapillary dropout are features of the early form of AMD, and endothelial dysfunction and vascular changes are primary characteristics of the neovascular clinical sub-type of AMD. Given the importance, the choroidal endothelium and outer vasculature play in supporting visual function, a better understanding of baseline choroidal signaling pathways engaged in tissue and cellular homeostasis is needed. Nuclear receptors are a large family of transcription factors responsible for maintaining various cellular processes during development, aging and disease. Herein we developed a comprehensive nuclear receptor atlas of human choroidal endothelial cells and freshly isolated choroidal tissue by examining the expression levels of all members of this transcription family using quantitative real time PCR. Given the close relationship between the choroid and retinal pigment epithelium (RPE), this data was cross-referenced with the expression profile of nuclear receptors in human RPE cells, to discover potential overlap versus cell-specific nuclear receptor expression. Finally, to identify candidate receptors that may participate in the pathobiology of AMD, we cataloged nuclear receptor expression in a murine model of wet AMD, from which we discovered a subset of nuclear receptors differentially regulated following neovascularization. Overall, these databases serve as useful resources establishing the influence of nuclear receptor signaling pathways on the outer vascular tissue of the eye, while providing a list of receptors, for more focused investigations in the future, to determine their suitability as potential therapeutic targets for diseases, in which the choroid is affected.

Exploring the Vitreoretinal Interface: A Key Instigator of Unique Retinal Hemorrhage Patterns in Pediatric Head Trauma.

PurposeVarious types of trauma can cause retinal hemorrhages in children, including accidental and nonaccidental head trauma. We used animal eyes and a finite element model of the eye to examine stress patterns produced during purely linear and angular accelerations, along with stresses attained during simulated repetitive shaking of an infant.MethodsUsing sheep and primate eyes, sclerotomy windows were created by removing the sclera, choroid, and retinal pigment epithelium to expose the retina. A nanofiber square was glued to a 5 mm2 area of retina. The square was pulled and separated from vitreous while force was measured. A finite element model of the pediatric eye was used to computationally measure tension stresses during shaking.ResultsIn both sheep and primate eyes, tension stress required for separation of retina from vitreous range from 1 to 5 kPa. Tension stress generated at the vitreoretinal interface predicted by the computer simulation ranged from 3 to 16 kPa during a cycle of shaking. Linear acceleration generated lower tension stress than angular acceleration. Angular acceleration generated maximal tension stress along the retinal vasculature. Linear acceleration produced more diffuse force distribution centered at the poster pole.ConclusionsThe finite element model predicted that tension stress attained at the retina during forcible shaking of an eye can exceed the minimum threshold needed to produce vitreoretinal separation as measured in animal eyes. Furthermore, the results show that movements that involve significant angular acceleration produce strong stresses localized along the vasculature, whereas linear acceleration produces weaker, more diffuse stress centered towards the posterior pole of the eye.

Capsule-dependent impact of MAPK signalling on host cell invasion and immune response during infection of the choroid plexus epithelium by Neisseria meningitidis

BackgroundThe Gram-negative bacterium Neisseria meningitidis (Nm) can cause meningitis in humans, but the host signalling pathways manipulated by Nm during central nervous system (CNS) entry are not completely understood.MethodsWe investigate the role of the mitogen-activated protein kinases (MAPK) Erk1/2 and p38 in an in vitro model of the blood-cerebrospinal fluid barrier (BCSFB) based on human epithelial choroid plexus (CP) papilloma (HIBCPP) cells during infection with Nm serogroup B (NmB) and serogroup C (NmC) strains. A transcriptome analysis of HIBCPP cells following infection with Nm by massive analysis of cDNA ends (MACE) was done to further characterize the cellular response to infection of the barrier.ResultsInterestingly, whereas NmB and NmC wild type strains required active Erk1/2 and p38 pathways for infection, invasion by capsule-deficient mutants was independent of Erk1/2 and, in case of the NmB strain, of p38 activity. The transcriptome analysis of HIBCPP cells following infection with Nm demonstrated specific regulation of genes involved in the immune response dependent on Erk1/2 signalling. Gene ontology (GO) analysis confirmed loss of MAPK signalling after Erk1/2 inhibition and revealed an additional reduction of cellular responses including NFκB and JAK-STAT signalling. Interestingly, GO terms related to TNF signalling and production of IL6 were lost specifically following Erk1/2 inhibition during infection with wild type Nm, which correlated with the reduced infection rates by the wild type in absence of Erk1/2 signalling.ConclusionOur data point towards a role of MAPK signalling during infection of the CP epithelium by Nm, which is strongly influenced by capsule expression, and affects infection rates as well as the host cell response.