Quantitative and Microstructural Changes of the Blood-Nerve Barrier in Peripheral Neuropathy

Peripheral neuropathy is accompanied by changes in the neuronal environment. The blood-nerve barrier (BNB) is crucial in protecting the neural homeostasis: Tight junctions (TJ) seal paracellular spaces and thus prevent external stimuli from entering. In different models of neuropathic pain, the BNB is impaired, thus contributing to local damage, immune cell invasion and, ultimately, the development of neuropathy with its symptoms. In this study, we examined changes in expression and microstructural localization of two key tight junction proteins (TJP), claudin-1 and the cytoplasmic anchoring ZO-1, in the sciatic nerve of mice subjected to chronic constriction injury (CCI). Via qPCR and analysis of fluorescence immunohistochemistry, a marked downregulation of mRNA as well as decreased fluorescence intensity were observed in the nerve for both proteins. Moreover, a distinct zig-zag structure for both proteins located at cell-cell contacts, indicative of the localization of TJs, was observed in the perineurial compartment of sham-operated animals. This microstructural location in cell-cell-contacts was lost in neuropathy as semiquantified via computational analysis, based on a novel algorithm. In summary, we provide evidence that peripheral neuropathy is not only associated with decrease in relevant TJPs but also exhibits alterations in TJP arrangement and loss in barrier tightness, presumably due to internalization. Specifically, semiquantification of TJP in cell-cell-contacts of microcompartments could be used in the future for routine clinical samples of patients with neuropathy

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder

Neue Ansätze bei neuropathischem Schmerz: microRNA-Expression in Spinalganglien und eine differenzierte Transkriptionsanalyse von primären sensorischen Neuronen

Neuropathic pain, caused by neuronal damage, is a severely impairing mostly chronic condition. Its underlying molecular mechanisms have not yet been thoroughly understood in their variety. In this doctoral thesis, I investigated the role of microRNAs (miRNAs) in a murine model of peripheral neuropathic pain. MiRNAs are small, non-coding RNAs known to play a crucial role in post-transcriptional gene regulation, mainly in cell proliferation and differentiation. Initially, expression patterns in affected dorsal root ganglia (DRG) at different time points after setting a peripheral nerve lesion were studied. DRG showed an increasingly differential expression pattern over the course of one week. Interestingly, a similar effect, albeit to a smaller extent, was observed in corresponding contralateral ganglia. Five miRNA (miR-124, miR-137, miR-183, miR-27b, and miR-505) were further analysed. qPCR, in situ hybridization, and bioinformatical analysis point towards a role for miR-137 and -183 in neuropathic pain as both were downregulated. Furthermore, miR-137 is shown to be specific for non-peptidergic non-myelinated nociceptors (C fibres) in DRG. As the ganglia consist of highly heterocellular tissue, I also developed a neuron-specific approach. Primarily damaged neurons were separated from intact adjacent neurons using fluorescence-activated cell-sorting and their gene expression pattern was analysed using a microarray. Thereby, not only were information obtained about mRNA expression in both groups but, by bioinformatical tools, also inferences on miRNA involvement. The general expression pattern was consistent with previous findings. Still, several genes were found differentially expressed that had not been described in this context before. Among these are corticoliberin or cation-regulating proteins like Otopetrin1. Bioinformatical data conformed, in part, to results from whole DRG, e.g. they implied a down-regulation of miR-124, -137, and -183. However, these results were not significant. In summary, I found that a) miRNA expression in DRG is influenced by nerve lesions typical of neuropathic pain and that b) these changes develop simultaneously to over-expression of galanin, a marker for neuronal damage. Furthermore, several miRNAs (miR-183, -137) exhibit distinct expression patterns in whole-DRG as well as in neuron-specific approaches. Therefore, further investigation of their possible role in initiation and maintenance of neuropathic pain seems promising. Finally, the differential expression of genes like Corticoliberin or Otopetrin 1, previously not described in neuropathic pain, has already resulted in follow-up projects.Neuropathischer Schmerz, d.h. Schmerz durch neuronale Schäden, ist eine stark beeinträchtigendes, oft chronisches Leiden. Die hierfür verantwortlichen molekularen Geschehen sind in ihrer Breite bislang nur unzureichend verstanden. In meiner Promotion habe ich die Rolle von microRNAs (miRNAs) in einem Mäusemodell des peripheren neuropathischen Schmerzes untersucht. MiRNAs sind kleine, nicht kodierende RNAs, die für posttranskriptionelle Genregulation, besonders Zellproliferation und –differenzierung verantwortlich sind. Im Experiment wurde zunächst ihre Expression in den Dorsalganglien geschädigter Nerven analysiert. Hier zeigte sich im Verlauf einer Woche ein zunehmend differentielles Expressionsmuster. Bemerkenswert war ein ähnlicher, wenn auch geringerer Effekt in kontralateralen Ganglien. In einem weiteren Schritt wurden fünf ausgewählte miRNAs (miR-124, miR-137, miR-183, miR-27b und miR-505) weiter analysiert. qPCR, In-situ-Hybridisierung und bioinformatische Untersuchungen deuteten auf Minderexpression von miR-137 und -183 bei neuropathischem Schmerz hin. Weiterhin stellte sich miR-137 als spezifisch für nicht-peptiderge nicht-myelinisierte Nozizeptoren in Dorsalganglien heraus. Da Dorsalganglien aus äußerst heterozellulärem Gewebe bestehen, entwickelte ich im Folgenden einen neuronenspezifischen Ansatz: Primär geschädigte sowie intakte benachbarte Neuronen wurden durch fluoreszenz¬aktivierte Zellsortierung (FACS) selektiert und ihre Genexpression jeweils in einem Microarray analysiert. Hierdurch konnten nicht nur direkte Informationen über mRNA-Expression in beiden Gruppen gewonnen, sondern durch bioinformatische Techniken auch Rückschlüsse auf miRNA-Expression gezogen werden. Das generelle Expressionsmuster entsprach der einschlägigen Literatur, allerdings zeigten sich auch bislang nicht beschriebene Veränderungen. Hierzu gehören Corticoliberin sowie Otopetrin1. Die bioinformatische Analyse bestätigte teilweise die Ergebnisse aus der ersten, ganglienweiten Untersuchung: Sie wiesen auf eine Minderexpression von miR-124, -137 und -183 hin, allerdings waren diese Ergebnisse nicht signifikant. Zusammengefasst zeigte sich, dass sich a) die Expression von miRNA in Dorsalganglien nach neuropathischen Läsionen ändert, und b) diese Veränderungen parallel zum neuropathischen Phänotyp entwickeln. Weiterhin wiesen mehrere miRNAs markante Expressionsmuster sowohl in ganglienweiten wie in neuronenspezifischen Untersuchugen auf. Daher scheint die weitere Untersuchung ihrer Rolle in Entwicklung und Aufrechterhaltung von neuropathischem Schmerz vielversprechend. Schließlich hat die Entdeckung von Expressionsveränderungen bei Genen wie Corticoliberin und Otopetrin1, bislang nicht im Zusammenhang mit neuropathischem Schmerz beschrieben, bereits zu Nachfolgeprojekten geführt

Quantitative and Microstructural Changes of the Blood-Nerve Barrier in Peripheral Neuropathy

Peripheral neuropathy is accompanied by changes in the neuronal environment. The blood-nerve barrier (BNB) is crucial in protecting the neural homeostasis: Tight junctions (TJ) seal paracellular spaces and thus prevent external stimuli from entering. In different models of neuropathic pain, the BNB is impaired, thus contributing to local damage, immune cell invasion and, ultimately, the development of neuropathy with its symptoms. In this study, we examined changes in expression and microstructural localization of two key tight junction proteins (TJP), claudin-1 and the cytoplasmic anchoring ZO-1, in the sciatic nerve of mice subjected to chronic constriction injury (CCI). Via qPCR and analysis of fluorescence immunohistochemistry, a marked downregulation of mRNA as well as decreased fluorescence intensity were observed in the nerve for both proteins. Moreover, a distinct zig-zag structure for both proteins located at cell-cell contacts, indicative of the localization of TJs, was observed in the perineurial compartment of sham-operated animals. This microstructural location in cell-cell-contacts was lost in neuropathy as semiquantified via computational analysis, based on a novel algorithm. In summary, we provide evidence that peripheral neuropathy is not only associated with decrease in relevant TJPs but also exhibits alterations in TJP arrangement and loss in barrier tightness, presumably due to internalization. Specifically, semiquantification of TJP in cell-cell-contacts of microcompartments could be used in the future for routine clinical samples of patients with neuropathy

MicroRNA-21-5p functions via RECK/MMP9 as a proalgesic regulator of the blood nerve barrier in nerve injury

Both nerve injury and complex regional pain syndrome (CRPS) can result in chronic pain. In traumatic neuropathy, the blood nerve barrier (BNB) shielding the nerve is impaired—partly due to dysregulated microRNAs (miRNAs). Upregulation of microRNA-21-5p (miR-21) has previously been documented in neuropathic pain, predominantly due to its proinflammatory features. However, little is known about other functions. Here, we characterized miR-21 in neuropathic pain and its impact on the BNB in a human-murine back translational approach. MiR-21 expression was elevated in plasma of patients with CRPS as well as in nerves of mice after transient and persistent nerve injury. Mice presented with BNB leakage, as well as loss of claudin-1 in both injured and spared nerves. Moreover, the putative miR-21 target RECK was decreased and downstream Mmp9 upregulated, as was Tgfb. In vitro experiments in human epithelial cells confirmed a downregulation of CLDN1 by miR-21 mimics via inhibition of the RECK/MMP9 pathway but not TGFB. Perineurial miR-21 mimic application in mice elicited mechanical hypersensitivity, while local inhibition of miR-21 after nerve injury reversed it. In summary, the data support a novel role for miR-21, independent of prior inflammation, in elicitation of pain and impairment of the BNB via RECK/MMP9

Baseline and demographic characteristics according to the result of the screening questionnaire used in a cross-sectional study conducted among a rural population of the Balaka district of Malawi, October to December 2012.

Baseline and demographic characteristics according to the result of the screening questionnaire used in a cross-sectional study conducted among a rural population of the Balaka district of Malawi, October to December 2012.</p

NCC diagnosis and serological findings among patients with epilepsy in rural Balaka district, Malawi.

NCC diagnosis and serological findings among patients with epilepsy in rural Balaka district, Malawi.</p

Flowchart of the people with epilepsy with detailed characteristics.

Flowchart of the people with epilepsy with detailed characteristics.</p