Neurovascular unit pathology is observed very early in disease progression in the mutant SOD1G93A mouse model of amyotrophic lateral sclerosis

Abstract

Amyotrophic lateral sclerosis (ALS) is a debilitating neurodegenerative disease characterized by motor neuron degeneration that causes neuromuscular denervation, resulting in muscle weakness and atrophy. Work over the decades using ALS mouse models has revealed that while initial pathology may occur within motor neurons, disease pathology is cell non-autologous. Impairment of the blood-spinal cord barrier (BSCB) occurs before motor neuron frank degeneration; however, precisely when the early pathogenesis of the neurovascular units occurs is not fully understood. Here we examine changes in morphology of neurovascular units, associated gene and protein expression in the lumbar spinal cord of SOD1G93A, and wild-type mice and correlate results with previous reports of early pathological events. Using RNA-sequencing and immunolabeling, we also show that both the neurovascular units and the vasculature of the SOD1G93A lumbar spinal cord present important modifications throughout the disease. Genes relevant for the neurovascular unit and immune cells were differentially expressed in the SOD1G93A ventral lumbar spinal cord compared to wild-type. A reduction in capillary density and tight junction (TJ) with overt BSCB breakdown was observed in the SOD1G93A lumbar spinal cord and ultrastructural observation revealed intact TJ. Additionally, thickened basement membrane, increased pericytes, and string vessels were observed. These alterations in neurovascular units and the vasculature are observed prior to reports of initial neuromuscular junction denervation. The identification of early pathogenesis may be critical to develop diagnostic tests and development of novel treatment strategies that target these early events.