Department of Psychology, Philipps-Universität Marburg, Marburg 35039, Germany.
Center for Mind, Brain and Behavior, Philipps-Universität Marburg and Justus-Liebig-Universität Giessen, Marburg 35039, Germany.
Proc Natl Acad Sci U S A. 2023 Aug 15;120(33):e2303491120. doi: 10.1073/pnas.2303491120. Epub 2023 Aug 7.
The formation of myelin, the fatty sheath that insulates nerve fibers, is critical for healthy brain function. A fundamental open question is what impact being born has on myelin growth. To address this, we evaluated a large ( = 300) cross-sectional sample of newborns from the Developing Human Connectome Project (dHCP). First, we developed software for the automated identification of 20 white matter bundles in individual newborns that is well suited for large samples. Next, we fit linear models that quantify how T1w/T2w (a myelin-sensitive imaging contrast) changes over time at each point along the bundles. We found faster growth of T1w/T2w along the lengths of all bundles before birth than right after birth. Further, in a separate longitudinal sample of preterm infants ( = 34), we found lower T1w/T2w than in full-term peers measured at the same age. By applying the linear models fit on the cross-section sample to the longitudinal sample of preterm infants, we find that their delay in T1w/T2w growth is well explained by the amount of time they spent developing in utero and ex utero. These results suggest that white matter myelinates faster in utero than ex utero. The reduced rate of myelin growth after birth, in turn, explains lower myelin content in individuals born preterm and could account for long-term cognitive, neurological, and developmental consequences of preterm birth. We hypothesize that closely matching the environment of infants born preterm to what they would have experienced in the womb may reduce delays in myelin growth and hence improve developmental outcomes.
髓鞘的形成，即神经纤维的脂肪鞘，对大脑健康功能至关重要。一个基本的开放性问题是出生对髓鞘生长有什么影响。为了解决这个问题，我们评估了来自发育人类连接组计划（dHCP）的一个大（= 300）的新生儿横断面样本。首先，我们开发了一种软件，用于自动识别个体新生儿的 20 个白质束，该软件非常适合于大样本。接下来，我们拟合了线性模型，定量描述了 T1w/T2w（一种髓鞘敏感的成像对比）在沿着束的每个点随时间的变化。我们发现，在出生前，T1w/T2w 在所有束的长度上的生长速度比出生后要快。此外，在另一项早产儿的纵向样本中（= 34），我们发现，与同龄的足月婴儿相比，T1w/T2w 较低。通过将横断面样本中的线性模型应用于早产儿的纵向样本，我们发现他们在 T1w/T2w 生长方面的延迟很好地解释了他们在子宫内和子宫外发育的时间。这些结果表明，白质在子宫内的髓鞘形成速度比子宫外快。出生后髓鞘生长速度的降低，反过来又解释了早产儿出生时髓鞘含量较低的原因，并且可能是早产儿出生带来的长期认知、神经和发育后果的原因。我们假设，使早产儿出生后的环境尽可能地与他们在子宫内经历的环境相匹配，可能会减少髓鞘生长的延迟，从而改善发育结果。
