Assessment of myelination development in neonatal rats using chemical exchange saturation transfer (CEST) 7-T MRI

Abstract

Myelination is a crucial process in the nervous system. This study aimed to evaluate the progression of myelin sheath development in different brain regions of neonatal rats at distinct developmental stages using Chemical Exchange Saturation Transfer (CEST) 7-T MRI. Male SD rats of different ages (3 days, 1 week, 2 weeks, 3 weeks, 1 month, 2 months) were selected for the study. Advanced in vivo MRI experiments were conducted using a 7-T MRI scanner. Custom MatLab scripts were employed to generate MR images and process the data. Myelin staining was used to assess myelin distribution in various brain regions. Statistical analysis was performed using repeated measures multivariate analysis of variance (MANOVA) and Spearman's rank correlation. The progression of myelination was significantly different in different brain regions (F(5, 30) = 3.34, P < 0.05), with the corpus callosum showing an accelerated rate of myelination. Within the first month alone, there was an increase of 46.1% in myelination (t(35) = 2.29, P < 0.05). The hypothalamus and internal capsule exhibited a more gradual yet consistent increase in myelination over the two-month period, with increases of 47.1% (t(35) = 2.27, P < 0.05) and 39.8% (t(35) = 2.59, P < 0.05), respectively. A substantial positive correlation was found between the MRI-based and histological measurements of myelination (r = 0.31, P < 0.05). This study demonstrates the potential of CEST 7-T MRI as a non-invasive tool for assessing myelination progression and provides insights into the differential myelination rates across various brain regions during early development.

Keywords: 7-T MRI; Chemical exchange saturation transfer; Histological evaluation; Myelination; Neonatal rats.