Glial Fibrillary Acidic Protein and Ionized Calcium-Binding Adapter Molecule 1 Immunostaining Score for the Central Nervous System of Horses With Non-suppurative Encephalitis and Encephalopathies.

Gisele Silva Boos,Daniele Mariath Bassuino,José Diomedes Barbosa,Christiane Herden,Edson Moleta Colodel,Klaus Failing,Márcio Botelho De Castro,David Driemeier

doi:10.3389/fvets.2021.660022

Abstract

Like humans, horses are susceptible to neurotropic and neuroinvasive pathogens that are not always readily identified in histological sections. Instead, alterations in astrocytes and microglia cells can be used as pathological hallmarks of injured nervous tissue in a variety of infectious and degenerative diseases. On the other hand, equine glial cell alterations are poorly characterized in diseases. Therefore, in this study, we provide a statistically proved score system to classify astrogliosis and microgliosis in the central nervous system (CNS) of horses, based on morphological and quantitative analyses of 35 equine cases of encephalitis and/or encephalopathies and four non-altered CNS as controls. For this system, we used glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (Iba1) immunohistochemistry, allied to statistical analysis to confirm that the scores were correctly designated. The scores of alterations ranged from 0 (non-altered) to 3 (severely altered) and provided a helpful method for describing astrocytic and microglial alterations in horses suffering from inflammatory and degenerative lesions. This system could be a template for comparative studies in other animal species and could aid algorithms designed for artificial intelligence methods lacking a defined morphological pattern.

Highlights

Astrogliosis and microgliosis have been used as pathological hallmarks of injured nervous tissue in a variety of degenerative and infectious diseases [1,2,3,4,5,6,7]
Normal astrocytes from these controls were characterized by a light brown cytoplasmic glial fibrillary acidic protein (GFAP) staining, surrounded by long and thin processes, while the nucleus remained unstained (Figure 1, grade 0)
Astrogliosis is widely used as a hallmark of diseased central nervous system (CNS) tissue, the correct designation of morphologic and quantitative astrocytic alterations, which were missing for horses, can help to relate certain pathogens/conditions in unresolved cases of encephalitis and encephalopathies

Summary

Introduction

Astrogliosis and microgliosis have been used as pathological hallmarks of injured nervous tissue in a variety of degenerative and infectious diseases [1,2,3,4,5,6,7]. Astrocytic and microglial alterations have been more closely documented in neurodegenerative diseases in humans and experimental animal models, but little information is available on glial alterations in the central nervous system (CNS) of horses [14, 15]. The establishment of a reliable quantitative and morphological classification system of astrocytic and microglial alterations in horses can help address lesion patterns on unresolved cases of encephalitis and encephalopathies. Pathologists could use the system for a complimentary assessment of lesions in the CNS and comparative studies involving glial response to injury by pathogens and/or degenerative lesions in other animal species and humans. An established score system for glial alterations would benefit machine learning systems, as it would provide a morphological template of different stages of alterations to complement algorithms for automatic quantification

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