Longitudinal Magnetic Resonance Imaging Analysis and Histological Characterization after Spinal Cord Injury in Two Mouse Strains with Different Functional Recovery: Gliosis as a Key Factor

Abstract

Spinal cord injuries (SCI) are disastrous neuropathologies causing permanent disabilities. The availability of different strains of mice is valuable for studying the pathophysiological mechanisms involved in SCI. However, strain differences have a profound effect on spontaneous functional recovery after SCI. CX3CR1 and Aldh1l1-EGFP mice that express green fluorescent protein in microglia/monocytes and astrocytes, respectively, are particularly useful to study glial reactivity. Whereas CX3CR1 mice have C57BL/6 background, Aldh1l1-EGFP are in Swiss Webster background. We first assessed spontaneous functional recovery in CX3CR1 and Aldh1l1-EGFP mice over 6 weeks after lateral spinal cord hemisection. Second, we carried out a longitudinal follow-up of lesion evolution using in vivo T2-weighted magnetic resonance imaging (MRI). Finally, we performed in-depth analysis of the spinal cord tissue using ex vivo T2-weighted MRI as well as detailed histology. We demonstrate that CX3CR1 mice have improved functional recovery and reduced anxiety after SCI compared with Aldh1l1-EGFP mice. We also found a strong correlation between in vivo MRI, ex vivo MRI, and histological analyses of the injured spinal cord in both strain of mice. All three modalities revealed no difference in lesion extension and volume between the two strains of mice. Importantly, histopathological analysis identified decreased gliosis and increased serotonergic axons in CX3CR1 compared with Aldh1l1-EGFP mice following SCI. These results thus suggest that the strain-dependent improved functional recovery after SCI may be linked with reduced gliosis and increased serotonergic innervation.

CSF1R Inhibition Reduces Microglia Proliferation, Promotes Tissue Preservation and Improves Motor Recovery After Spinal Cord Injury

“…Dynamic walking pattern analysis was done using CatWalk™ (Noldus, Wageningen, Netherlands). We analyzed data with CatMerge (InnovationNet, Tiranges, France), as previously described (Gerber et al, 2012 , 2013 ; Noristani et al, 2018a , b ). Six runs per animal were recorded at each time-point with a minimum inclusion criterion of three runs crossed at the same speed and at least 3-full step sequence patterns per mice per time point.…”

“…T2W-MRI acquisitions were done at 4 and 6 weeks after injury using a 9.4 Tesla apparatus (Agilent Varian 9.4/160/ASR, Santa Clara, CA, USA) equipped with a MAGNEX TS1276D, a Quadrature Volume Coils 400 MHz RF43 (43 mm internal diameter, Rapid Biomedical, Rimpar, Germany) and associated with a VnmrJ Imaging acquisition system (Agilent, Palo Alto, CA, USA), as previously described (Noristani et al, 2015 , 2018a ).…”

The effects of mouse strain and age on a model of unilateral cervical contusion spinal cord injury

“…Despite several reports of mouse strain differences in functional recovery and tissue pathology following thoracic SCI [9][10][11][12][13], the role of strain has been largely unexplored in cervical injuries, especially in a unilateral model. Therefore, this study aimed to compare functional deficits between the prevalent C57BL/6 and two common strains for xenograft cell transplantation studies, Rag2g (c) and Rag2g (c) hybrid mice, which lack T, B, and NK cells, making them effective transplant hosts for human cells.…”

“…We also report that a number of histological endpoints, including GFAP and lesion volume, are correlated with behavioral deficits, supporting the applicability of this model. Most importantly, based on earlier demonstrations of strain variation in responses to thoracic contusion SCI [9][10][11][12][13], we report data from three strains of mice, C57Bl/6 as the most commonly used background, and Rag2gamma(c)-/-as well as Agouti SCIDxRag2Gamma hybrid, as key strains for cell transplantation studies [14]. Finally, with evidence that histological damage and locomotor recovery are age-dependent, we describe the characteristics of injury in young (3-4 months old) versus aging (16-17 months old) animals.…”

Spinal cord microglia in health and disease

“…В таких моделях под контролем промотора гена специфического микроглиального белка экспрессируется легко идентифицируемая молекула, например, зеленого флуоресцентного белка (EGFP). В настоящее время доступны несколько линий мышей, в которых для флуоресцентной маркировки клеток используют локусы предполагаемых сигнатурных генов микроглии -Iba-1, Runx1, Csf1r, Lyz2, Itgam, Sall1, CX3cr1 [33][34][35][36]. Однако использование трансгенных животных перечисленных линий осложняется тем, что достаточно трудно отличать активированные микроглиоциты от таких функционально сходных клеток, как моноциты крови, периваскулярные макрофаги, менингеальные макрофаги и макрофаги сосудистого сплетения [37].…”