Assessing brain involvement in Fabry disease with deep learning and the brain-age paradigm

While neurological manifestations are core features of Fabry disease (FD), quantitative neuroimaging biomarkers allowing to measure brain involvement are lacking. We used deep learning and the brain-age paradigm to assess whether FD patients' brains appear older than normal and to validate brain-predicted age difference (brain-PAD) as a possible disease severity biomarker. MRI scans of FD patients and healthy controls (HCs) from a single Institution were, retrospectively, studied. The Fabry stabilization index (FASTEX) was recorded as a measure of disease severity. Using minimally preprocessed 3D T1-weighted brain scans of healthy subjects from eight publicly available sources (N = 2160; mean age = 33 years [range 4-86]), we trained a model predicting chronological age based on a DenseNet architecture and used it to generate brain-age predictions in the internal cohort. Within a linear modeling framework, brain-PAD was tested for age/sex-adjusted associations with diagnostic group (FD vs. HC), FASTEX score, and both global and voxel-level neuroimaging measures. We studied 52 FD patients (40.6 ± 12.6 years; 28F) and 58 HC (38.4 ± 13.4 years; 28F). The brain-age model achieved accurate out-of-sample performance (mean absolute error = 4.01 years, R2 = .90). FD patients had significantly higher brain-PAD than HC (estimated marginal means: 3.1 vs. -0.1, p = .01). Brain-PAD was associated with FASTEX score (B = 0.10, p = .02), brain parenchymal fraction (B = -153.50, p = .001), white matter hyperintensities load (B = 0.85, p = .01), and tissue volume reduction throughout the brain. We demonstrated that FD patients' brains appear older than normal. Brain-PAD correlates with FD-related multi-organ damage and is influenced by both global brain volume and white matter hyperintensities, offering a comprehensive biomarker of (neurological) disease severity.

Mild Skin Heating Evokes Warmth Hyperknesis Selectively for Histaminergic and Serotoninergic Itch in Humans

Chronic itch can severely affect quality of life. Patients report that their chronic itch can be exacerbated by exposure to warm conditions (“warmth hyperknesis”). The aim of this mechanistic study was to investigate the effect of mild heating of the skin in humans on various experimental models of itch. A total of 18 healthy subjects were recruited to the study. Itch was provoked by histamine, serotonin, or cowhage in 3 different sessions. The provoked area was heated with an infrared lamp, and the skin temperature was either not altered, or was increased by 4°C or 7°C. Subsequent to induction of itch, the itch intensity was recorded for 10 min while the skin was heated continuously throughout the entire period of itch induction. Heating the skin resulted in a significant increase in itch intensity when provoked by histamine or serotonin. It is possible that thermoception and pruriception interact and selectively produce a higher itch intensity in histaminergic and serotoninergic itch.

Stratification of multiple sclerosis patients using unsupervised machine learning: a single-visit MRI-driven approach

OBJECTIVES

To stratify patients with multiple sclerosis (pwMS) based on brain MRI-derived volumetric features using unsupervised machine learning.

METHODS

The 3-T brain MRIs of relapsing-remitting pwMS including 3D-T1w and FLAIR-T2w sequences were retrospectively collected, along with Expanded Disability Status Scale (EDSS) scores and long-term (10 ± 2 years) clinical outcomes (EDSS, cognition, and progressive course). From the MRIs, volumes of demyelinating lesions and 116 atlas-defined gray matter regions were automatically segmented and expressed as z-scores referenced to external populations. Following feature selection, baseline MRI-derived biomarkers entered the Subtype and Stage Inference (SuStaIn) algorithm, which estimates subgroups characterized by distinct patterns of biomarker evolution and stages within subgroups. The trained model was then applied to longitudinal MRIs. Stability of subtypes and stage change over time were assessed via Krippendorf's α and multilevel linear regression models, respectively. The prognostic relevance of SuStaIn classification was assessed with ordinal/logistic regression analyses.

RESULTS

We selected 425 pwMS (35.9 ± 9.9 years; F/M: 301/124), corresponding to 1129 MRI scans, along with healthy controls (N = 148; 35.9 ± 13.0 years; F/M: 77/71) and external pwMS (N = 80; 40.4 ± 11.9 years; F/M: 56/24) as reference populations. Based on 11 biomarkers surviving feature selection, two subtypes were identified, designated as "deep gray matter (DGM)-first" subtype (N = 238) and "cortex-first" subtype (N = 187) according to the atrophy pattern. Subtypes were consistent over time (α = 0.806), with significant annual stage increase (b = 0.20; p < 0.001). EDSS was associated with stage and DGM-first subtype (p ≤ 0.02). Baseline stage predicted long-term disability, transition to progressive course, and cognitive impairment (p ≤ 0.03), with the latter also associated with DGM-first subtype (p = 0.005).

CONCLUSIONS

Unsupervised learning modelling of brain MRI-derived volumetric features provides a biologically reliable and prognostically meaningful stratification of pwMS.

KEY POINTS

• The unsupervised modelling of brain MRI-derived volumetric features can provide a single-visit stratification of multiple sclerosis patients. • The so-obtained classification tends to be consistent over time and captures disease-related brain damage progression, supporting the biological reliability of the model. • Baseline stratification predicts long-term clinical disability, cognition, and transition to secondary progressive course.

Software Tool for Soil Surface Parameters Retrieval from Fully Polarimetric Remotely Sensed SAR Data

The retrieval of soil surface parameters, in particular soil moisture and roughness, based on Synthetic Aperture Radar (SAR) data, has been the subject of a large number of studies, of which results are available in the scientific literature. However, although refined methods based on theoretical/analytical scattering models have been proposed and successfully applied in experimental studies, at the operative level very simple, empirical models with a number of adjustable parameters are usually employed. One of the reasons for this situation is that retrieval methods based on analytical scattering models are not easy to implement and to be employed by non-expert users. Related to this, commercially and freely available software tools for the processing of SAR data, although including routines for basic manipulation of polarimetric SAR data (e.g., coherency and covariance matrix calculation, Pauli decomposition, etc.), do not implement easy-to-use methods for surface parameter retrieval. In order to try to fill this gap, in this paper we present a user-friendly computer program for the retrieval of soil surface parameters from Polarimetric Synthetic Aperture Radar (PolSAR) imageries. The program evaluates soil permittivity, soil moisture and soil roughness based on the theoretical predictions of the electromagnetic scattering provided by the Polarimetric Two-Scale Model (PTSM) and the Polarimetric Two-Scale Two-Component Model (PTSTCM). In particular, nine different retrieval methodologies, whose applicability depends on both the used polarimetric data (dual- or full-pol) and the characteristics of the observed scene (e.g., on its topography and on its vegetation cover), as well as their implementation in the Interactive Data Language (IDL) platform, are discussed. One specific example from Germany’s Demmin test-site is presented in detail, in order to provide a first guide to the use of the tool. Obtained retrieval results are in agreement with what was expected according to the available literature.

Antipruritic effects of transient heat stimulation on histaminergic and nonhistaminergic itch

BACKGROUND

Chronic itch is notoriously difficult to treat. Counterstimuli are able to inhibit itch, but this principle is difficult to apply in clinical practice, and the mechanisms behind counterstimulation-induced itch suppression in humans are unclear.

OBJECTIVES

Firstly, to analyse the stimulus-response effects of transient heat stimuli on histaminergic and nonhistaminergic itch, and secondly, to investigate whether the antipruritic effect depends on homotopic (peripheral mediation) or heterotopic (central mediation) counterstimulation relative to the itch provocation site.

METHODS

Eighteen healthy volunteers participated (eight female, mean age 25·7 ± 0·8 years). Itch was evoked on premarked areas of the volar forearms, by either histamine (1% solution) or cowhage (35-40 spicules). In addition to the itch provocations (experiment 1), 5-s homotopic heat stimuli at 32, 40, 45 or 50 °C were applied. In experiment 2, heat stimuli were applied either homotopically, intrasegmentally (next to the provocation site) or extrasegmentally (dorsal forearm). Itch intensity was evaluated throughout the procedures using a digital visual analogue scale.

RESULTS

Homotopic counterstimuli inhibited histaminergic itch by 41·3% at 45 °C (P < 0·01) and by 76·7% at 50 °C (P < 0·001). Cowhage-induced itch was less prone to counterstimulation and was significantly diminished only at 50 °C, by 43·6% (P = 0·009). Counterstimulations applied heterotopically were not able to inhibit itch significantly.

CONCLUSIONS

Itch pathway-specific effects of counterstimuli were observed between homo- and heterotopic stimulation. Histaminergic itch was robustly inhibited by short-term homotopic noxious heat stimuli for up to 10 min. Nonhistaminergic itch was only weakly inhibited. The inhibitory effects exerted by the short-term heat stimuli only occurred following homotopic counterstimulation.

Tackling Chronic Pain and Inflammation through the Purinergic System

The purinergic system is composed of purine and pyrimidine transmitters, the enzymes that modulate the interconversion of nucleotides and nucleosides, the membrane transporters that control their extracellular concentrations, and the many receptor subtypes that are responsible for their cellular responses. The components of this system are ubiquitously localized in all tissues and organs, and their involvement in several physiological conditions has been clearly demonstrated. Moreover, extracellular purine and pyrimidine concentrations rise several folds under pathological conditions like tissue damage, ischemia, and inflammation, which suggest that this signaling system might contribute both to disease outcome and, possibly, to its tentative resolution. The complexity of this system has greatly impaired the clear identification of the mediators and receptors that are actually involved in a given pathology, also due to the often opposite roles played by the various receptor subtypes. Nevertheless, this knowledge is fundamental for the possible exploitation of these molecular entities as targets for the development of new pharmacological approaches. In this review, we aim at highlighting what is currently known on the role of the purinergic system in various pain conditions and during inflammatory processes. Although some confusion may arise from conflicting results, literature data clearly show that targeting specific purinergic receptors may represent an innovative approach to various pain and inflammatory conditions, and that new purine-based drugs are now very close to reach the market with these indications.

Purple Corn Extract as Anti-allodynic Treatment for Trigeminal Pain: Role of Microglia

Natural products have attracted interest in the search for new and effective analgesics and coadjuvant approaches to several types of pain. It is in fact well known that many of their active ingredients, such as anthocyanins (ACNs) and polyphenols, can exert potent anti-inflammatory actions. Nevertheless, their potential beneficial effects in orofacial painful syndromes have not been assessed yet. Here, we have evaluated the preventive effect of an ACN-enriched purple corn extract against the development of orofacial allodynia, in comparison with isogenic yellow corn extract containing only polyphenols. Orofacial allodynia developed following induction of temporomandibular joint (TMJ) inflammation in male rats, due to the injection of Complete Freund’s Adjuvant (CFA), and was evaluated by von Frey filaments. Animals drank purple or yellow corn extracts or water starting from 11 days before induction of inflammation and up to the end of the experiment 3 days later. To highlight possible additive and/or synergic actions, some animals also received the anti-inflammatory drug acetyl salicylic acid (ASA). In parallel with the evaluation of allodynia, we have focused our attention on the activation of microglia cells in the central nervous system (CNS), as it is well-known that they significantly contribute to neuronal sensitization and pain. Our data demonstrate that purple corn extract is as effective as ASA in preventing the development of orofacial allodynia, and only partial additive effect is observed when the two agents are co-administered. Yellow corn exerted no effect. Multiple mechanisms are possibly involved in the action of purple corn, including reduction of trigeminal macrophage infiltration and the shift of microglia cell polarization to an anti-inflammatory phenotype. In fact, in rats receiving yellow corn or water microglia cells show thick, short cell processes typical of activated cells. Conversely, thinner and longer microglia cell processes are observed in the brainstem of animals drinking purple corn extract; shape changes are accompanied by a reduction in the expression of pro-inflammatory molecules and increased production of anti-inflammatory mediators. Administration of purple corn extracts therefore represents a possible low-cost and easy way to reduce trigeminal-associated pain in various pathological conditions also thanks to the modulation of microglia reactivity.

Perturbation Theory for Scattering from Multilayers with Randomly Rough Fractal Interfaces: Remote Sensing Applications

A general, approximate perturbation method, able to provide closed-form expressions of scattering from a layered structure with an arbitrary number of rough interfaces, has been recently developed. Such a method provides a unique tool for the characterization of radar response patterns of natural rough multilayers. In order to show that, here, for the first time in a journal paper, we describe the application of the developed perturbation theory to fractal interfaces; we then employ the perturbative method solution to analyze the scattering from real-world layered structures of practical interest in remote sensing applications. We focus on the dependence of normalized radar cross section on geometrical and physical properties of the considered scenarios, and we choose two classes of natural stratifications: wet paleosoil covered by a low-loss dry sand layer and a sea-ice layer above water with dry snow cover. Results are in accordance with the experimental evidence available in the literature for the low-loss dry sand layer, and they may provide useful indications about the actual ability of remote sensing instruments to perform sub-surface sensing for different sensor and scene parameters.

Aquaporin 4 expression on trigeminal satellite glial cells under normal and inflammatory conditions

Aims

Limited information is currently available for the expression and role of Aquaporin 4 (AQP4) (AQ4) in the peripheral nervous system (PNS). It has been demonstrated that AQP4 is expressed in sensory ganglia. Immunohistochemistry has revealed that satellite glial cells (SGCs) surrounding the cell bodies of the primary afferent sensory neurons in these sensory ganglia exclusively express AQP4 at a considerably lower level than what is seen in astrocytes. The pathophysiological relevance of AQP4 in peripheral nociception; however, remains unclear. Hence, this study aimed at investigating AQP4 expression in trigeminal neurons and SGCs under normal and inflammatory conditions relevant to craniofacial pain conditions.

Methods

Rat trigeminal ganglia (TG) were isolated from adult male Sprague-Dawley rats subjected to a model of trigeminal inflammation evoked by unilateral complete Freund’s adjuvant (CFA) injection in temporomandibular joint. Immunohistochemistry was performed on TG sections of CFA-treated animals. NeuN and GS markers were used for identification of neurons and SGCs, respectively. AQP4 expression was investigated in both ipsilateral and contralateral TG sections. The study protocol was approved by the local ethics committee.

Results

Co-localization of NeuN-AQP4 and GS-AQP4 were identified in both ipsi and contralateral trigeminal ganglia of the CFA-treated rats. However, we did not detect any difference between the ipsi- and contralateral side in terms of alteration in AQP4 receptor expression.

Conclusions

AQP4 was expressed both on trigeminal neurons and SGCs and CFA did not cause a remarkable change in AQP4 expression, when ipsilateral and contralateral TG of the test animals was compared. Previously, it has been shown that in a neuropathic pain model no difference is detectable between wild type and AQP4-deficient mice, for mechanical and thermal perception; however, in formalin pain model AQP4-deficient mice have higher thermal pain thresholds. Further investigation is required to clarify role of AQP4 in pain.