Development of myelin in fetal and postnatal neocortex of the pig, the European wild boar Sus scrofa

Abstract

Myelination of the neocortex of altricial species is mostly a postnatal event, and the appearance of myelin has been associated with the end of the critical period for ocular dominance plasticity in rodent visual cortex. Due to their precocality, ungulates may tell a different story. Here, we analyzed the development of PDGFRα positive oligodendrocyte precursor cells and expression of myelin proteins in the laminar compartments of fetal and postnatal porcine cortex from E45 onwards. Precursor cell density initially increased and then decreased but remained present at P90. MAG and MBP staining were detectable at E70 in subventricular zone and deep white matter, ascending into gyral white matter at E85, and into the gray matter and marginal zone at E100 (birth in pig at E114). Protein blots confirmed the declining expression of PDGFRα from E65 onwards, and the increase of MBP and MAG expression from E80 onwards. Somatosensory input elicited by spontaneous activity is considered important for the formation of the body representation. Indeed, PDGFRα, MBP and MAG expression started earlier in somatosensory than in visual cortex. Taken together, myelination proceeded in white and gray matter and marginal zone of pig cortex before birth with an areal-specific time course, and an almost mature pattern was present at P5 in visual cortex.

Vascular development of fetal and postnatal neocortex of the pig, the European wild boarSus scrofa

“…All litters prepared for immunohistochemistry and for protein blots, respectively, have been listed in detail earlier (Sobierajski et al, 2023; see Table 1). Dissected brains were immersion-fixed in 4% paraformaldehyde in 0.1 M phosphate buffer pH 7.4 with 5% (vol/vol) water-saturated picric acid for about 2 weeks at 8°C (refreshed once).…”

“…As described (Sobierajski et al, 2023), tissue blocks of visual and somatosensory cortex were taken during preparation of the fetuses (ages E65, E80, E95, E100 and P90) and frozen on dry ice for storage. Small blocks were first pulverized on dry ice.…”

“…As described (Sobierajski et al, 2023) 1) were incubated overnight at 4°C, followed by washes for 10 min in TBST (50 mM Tris, pH 7.4, 150 mM NaCl, 0.1% Tween-20) and 10 min in TBS. Appropriate alkaline phosphatase-conjugated secondaries were incubated for 90 minutes.…”

“…Also, myelination begins early with the first oligodendrocyte progenitors found at E45 (gestation in pig is 114 days) and large amounts of myelinated axons being present already at E100. Expression of myelin-related proteins commences 1-2 weeks earlier in the somatosensory compared to the visual cortex which suggests a driving role of specific somatosensory activity (Sobierajski et al, 2023). The present study analyzes vascular development in visual cortex, and the expression of selected proteins in visual and somatosensory cortex.…”

A hydrolyzed lipid blend diet promotes myelination in neonatal piglets in a region and concentration‐dependent manner

“…In humans, myelination begins around the third trimester of gestation, surges until around age 5, and continues well into adulthood (Barkovich, 2005;Lebel & Beaulieu, 2011;Miller et al, 2012). In contrast to rodents in which myelination is a predominately postnatal event, myelin development of pigs begins in utero and mirrors that of humans (Conrad et al, 2012;Conrad & Johnson, 2015;Pond et al, 2000;Sweasey et al, 1976), and is a useful model to study myelination of cortical regions (Sobierajski et al, 2023). In addition, the proportion of white matter to gray matter volume in pigs is comparable to that of humans (Conrad et al, 2012;Ryan et al, 2018).…”