Neonatal Mesenchymal Stem Cell Treatment Improves Myelination Impaired by Global Perinatal Asphyxia in Rats

Abstract

The effect of perinatal asphyxia (PA) on oligodendrocyte (OL), neuroinflammation, and cell viability was evaluated in telencephalon of rats at postnatal day (P)1, 7, and 14, a period characterized by a spur of neuronal networking, evaluating the effect of mesenchymal stem cell (MSCs)-treatment. The issue was investigated with a rat model of global PA, mimicking a clinical risk occurring under labor. PA was induced by immersing fetus-containing uterine horns into a water bath for 21 min (AS), using sibling-caesarean-delivered fetuses (CS) as controls. Two hours after delivery, AS and CS neonates were injected with either 5 μL of vehicle (10% plasma) or 5 × 104 MSCs into the lateral ventricle. Samples were assayed for myelin-basic protein (MBP) levels; Olig-1/Olig-2 transcriptional factors; Gglial phenotype; neuroinflammation, and delayed cell death. The main effects were observed at P7, including: (i) A decrease of MBP-immunoreactivity in external capsule, corpus callosum, cingulum, but not in fimbriae of hippocampus; (ii) an increase of Olig-1-mRNA levels; (iii) an increase of IL-6-mRNA, but not in protein levels; (iv) an increase in cell death, including OLs; and (v) MSCs treatment prevented the effect of PA on myelination, OLs number, and cell death. The present findings show that PA induces regional- and developmental-dependent changes on myelination and OLs maturation. Neonatal MSCs treatment improves survival of mature OLs and myelination in telencephalic white matter.

Sustained Energy Deficit Following Perinatal Asphyxia: A Shift towards the Fructose-2,6-bisphosphatase (TIGAR)-Dependent Pentose Phosphate Pathway and Postnatal Development

“…The effect of PA on mature OLs (MBP positive cells), astrocytes (GFAP positive cells), and microglia (Ionized calcium-binding adaptor molecule 1, Iba-1 positive cells) was further investigated in the same telencephalic coronal section of AS and CS animals taken at P7. We observed that the number of MBP cells/mm 3 was decreased in AS compared to that in CS animals (by ~50%), without any effect on astrocytes and microglia markers [ 68 ], supporting the view that OLs are the most vulnerable glial cells to hypoxia-reoxygenation injury, at least in the examined brain regions. In the external capsule and corpus callosum, TUNEL/MBP-DAPI/mm 3 quantification was increased in AS compared to the CS condition, suggesting that PA increases OLs specific cell death, but also disrupts oligodendroglial lineage maturation, explaining the significant decrease observed in the number of OLs.…”

“…40 min after delivery (accounted from the time the uterine horns are excised from the abdominal cavity, cutting the uterine artery and venous at the level of the cervix), surviving pups are evaluated with an Apgar scale adapted to rats, monitoring the body weight, sex, color of the skin, respiratory frequency, gasping, vocalization, muscular rigidity and spontaneous movements [ 66 , 67 ]. The evaluation can be extended to several days after delivery [ 68 , 69 ]. The Apgar evaluation is critical for this experimental model because it assesses the extent of the insult since severity is directly correlated with the rate of survival and recovery by the pups of a litter.…”

“…Nevertheless, caution is advised when extrapolating to human data obtained in rodents. Compared to humans, the brain of rodent neonates is premature, based on neocortex development [ 72 ] and the pattern of the oligodendrocyte (OL) lineage progression required for cerebral myelination [ 68 , 73 ]. Nevertheless, despite the obvious limitations, experimental models in rodents have led to significant progress for the understanding of the mechanisms of the long-term impairments produced by PA.…”

“…Gene transcripts were amplified by RT-qPCR, quantified by the ΔΔCT method, using β-actin as a housekeeping gene. We found [ 68 ] that myelin basic protein (MBP), and Olig-1 and Olig-2 mRNA levels increased along with development in CS and AS newborns, without any significant difference among the conditions, except for Olig-1 mRNA levels, a transcription factor involved in the modulation of OLs function, that under pathological conditions, is able to promote repair of demyelinating lesions [ 184 ]. At P7, Olig-1 mRNA levels increased in AS compared to the CS condition, suggesting a myelin repairing mechanism.…”

“…In coronal formalin-fixed sections, myelinated fibers were detected (MBP-positive immunofluorescence) and monitored by confocal microscopy, observing a decrease of MBP-positive signals in sections from PA-exposed, versus sections from control animals. Such decrease was only observed at P7, affecting the external capsule (decreased by ~50%), corpus callosum (by ~60%), and cingulum (by ~70%) [ 68 ]. No differences were observed at P14, indicating a CNS plasticity to respond in line with the brain injury [ 185 ].…”