Journal Article

Limited effects of preterm birth and the first enteral nutrition on cerebellum morphology and gene expression in piglets

van Elburg, Ruurd M., Sangild, Per T., Kaalund, Sanne S., Bergström, Anders, Andersen, Anders D., Pakkenberg, Bente, Skovgaard, Kerstin, Thymann, Thomas, Rosenørn, Ann, Greisen, Gorm O.

2016

Overview

Preterm pigs show many signs of immaturity that are characteristic of preterm infants. In preterm infants, the cerebellum grows particularly rapid and hypoplasia and cellular lesions are associated with motor dysfunction and cognitive deficits. We hypothesized that functional brain delays observed in preterm pigs would be paralleled by both structural and molecular differences in the cerebellum relative to term born piglets. Cerebella were collected from term (n = 56) and preterm (90% gestation, n = 112) pigs at 0, 5, and 26 days after birth for stereological volume estimations, large‐scale qPCR gene expression analyses (selected neurodevelopmental genes) and western blot protein expression analysis (Sonic Hedgehog pathway). Memory and learning was tested using a T‐maze, documenting that preterm pigs showed delayed learning. Preterm pigs also showed reduced volume of both white and gray matter at all three ages but the proportion of white matter increased postnatally, relative to term pigs. Early initiation of enteral nutrition had limited structural or molecular effects. The Sonic Hedgehog pathway was unaffected by preterm birth. Few differences in expression of the selected genes were found, except consistently higher mRNA levels of Midkine, p75, and Neurotrophic factor 3 in the preterm cerebellum postnatally, probably reflecting an adaptive response to preterm birth. Pig cerebellar development appears more affected by postconceptional age than by environmental factors at birth or postnatally. Compensatory mechanisms following preterm birth may include faster white matter growth and increased expression of selected genes for neurotrophic factors and regulation of angiogenesis. While the pig cerebellum is immature in 90% gestation preterm pigs, it appears relatively mature and resilient toward environmental factors. We recently demonstrated impaired motor skills and cognitive capacity in our well established pig model of premature birth (Andersen et al., Am. J. Physiol. Regul. Integr. Comp. Physiol., 310(6): R481‐R492, 2016) and hypothesized that moderate preterm birth would be associated with impaired cerebellar growth and altered gene expression postnatally. Cerebella were collected from term (n = 56) and preterm (90% gestation, n = 112) pigs at 0, 5 and 26 days after birth for stereological volume estimations, large‐scale qPCR neurodevelopmental gene expression analyses and Western blot (Sonic Hedgehog pathway). Although minor differences with regards to cerebellar gray and white matter volumes and gene expression difference for a few specific angiogenesis and neurotrophic factors was observed between the preterm and term cerebella, development of this pig brain region seemed more affected by postconceptional age than by environmental factors at birth or postnatally, indicating an advanced level of maturation.

• Publisher: John Wiley & Sons, Inc,John Wiley and Sons Inc
• Subject: Angiogenesis / Animals / Animals, Newborn - genetics / Animals, Newborn - growth & development / Animals, Newborn - metabolism / Behavior, Animal / Biometry - methods / Central Nervous System / Cerebellum / Cerebellum - growth & development / Cerebellum - metabolism / Cerebellum - pathology / Cognitive ability / Developmental Neuroscience / Enteral and parenteral nutrition / Enteral Nutrition - methods / Environmental factors / Gene expression / Gene Expression Regulation, Developmental - physiology / Gestation / Gestational Age / Hedgehog Proteins - metabolism / Hogs / Hypoplasia / Infants / Learning / Maternal, Fetal and Neonatal Physiology / Maze Learning - physiology / Memory / Midkine / neonatal brain development / Neurotrophic factors / Newborn babies / Nutrition / Organ Size - physiology / Original Research / Parenteral Nutrition - methods / Physiology / postconceptional age / Premature birth / prematurity / Signalling Pathways / Substantia alba / Substantia grisea / Suidae / Sus scrofa