Global perinatal asphyxia impairs myelination and oliodendrocyte maturation in rats : prevention by neonatal mesenchymal stem cells treatment

Abstract

The effect of global perinatal asphyxia (PA) on myelination, oligodendrocytes (OLs), neuroinflammation and cell viability was evaluated in telencephalon and hippocampus of rats at postnatal day (P)1, 7 and 14, covering a period characterised by a spur of neuronal networking, finding a sustained injury that may have profound adverse effects on brain development. The study evaluated the effect of neonatal treatment with mesenchymal stem cells (MSCs). PA was induced by immersing foetus-containing uterine horns into a water bath at 37°C for 21 min. Asphyxia-exposed (AS) and sibling caesarean-delivered (CS) foetuses were resuscitated and nurtured by surrogate dams. Two hours after delivery, AS and CS neonates were injected with either 5 μl of vehicle (10% rat plasma) or 5x104 rat adipose tissue-derived MSCs into the left lateral ventricle. Animals were euthanized at P1, 7 or 14, dissecting samples from telencephalon and hippocampus to be assayed for (i) myelination (myelin-basic protein, MBP) and Olig-1/Olig-2 transcriptional factors (by immunofluorescence, IF, and RT-qPCR); (ii) Glial number (OLs, MBP-DAPI/mm3; astrocytes, GFAP-DAPI/mm3; microglia, Iba-1-DAPI/mm3, by IF); (iii) neuroinflammation, including proinflammatory cytokines (IL-1β, IL-6, TNF-α and Cox-2, by RT-qPCR and ELISA), and (iv) delayed cell death (by TUNEL assay). It was found that PA produced at P7: (i) a decrease of MBP immunoreactivity in telencephalon (external capsule, corpus callosum, cingulum), but not in fimbriae of hippocampus; (ii) an increase of Olig-1 transcriptional factor mRNA levels in telencephalon; (iii) an increase of IL-6 mRNA, but not of protein levels in telencephalon; (iv) an increase of cell death, including OLs-specific cell death in telencephalon. (v) MSCs treatment prevented the effect of PA on myelination, OLs number and cell death. The present study demonstrates that PA induces regional and developmental-dependent changes on myelination and OLs maturation, but not on astroglia and microglia. Thus, OLs are the most vulnerable glial cells to hypoxia-reoxygenation insults at early neonatal stages, evaluated in vulnerable areas. Early neonatal MSCs treatment significantly improves survival of mature OLs and myelination in telencephalic white matter. The outcome occurred in association with decreased apoptosis. Future studies are required to elucidate the precise pharmacological mechanism