Sex-dependent effect of a low neurosteroid environment and intrauterine growth restriction on fetal guinea pig brain development.

Abstract

Progesterone and its neuroactive metabolite, allopregnanolone, are present in high concentrations during pregnancy, but drop significantly following birth. Allopregnanolone influences foetal arousal and enhances cognitive and behavioural recovery following traumatic brain injury. Inhibition of allopregnanolone synthesis increases cell death in foetal animal brains with experimental hypoxia. We hypothesised that complications during pregnancy, such as early or preterm loss of placental steroids and intrauterine growth restriction (IUGR), would disrupt the foetal neurosteroid system, contributing to poor neurodevelopmental outcomes. This study aimed to investigate the effects of chronic inhibition of allopregnanolone synthesis before term and IUGR on developmental processes in the foetal brain. Guinea pig foetuses were experimentally growth restricted at midgestation and treated with finasteride, an inhibitor of allopregnanolone synthesis. Finasteride treatment reduced foetal brain allopregnanolone concentrations by up to 75% and was associated with a reduction in myelin basic protein (MBP) (PZ0 . 001) and an increase in glial fibrillary acidic protein expression in the subcortical white matter brain region (P!0 . 001). IUGR resulted in decreased MBP expression (P!0 . 01) and was associated with a reduction in the expression of steroidogenic enzyme 5a-reductase (5aR) type 2 in the foetal brain (PZ0 . 061). Brain levels of 5aR1 were higher in male foetuses (PZ0 . 008). Both IUGR and reduced foetal brain concentrations of allopregnanolone were associated with altered expression of myelination and glial cell markers within the developing foetal brain. The potential role of neurosteroids in protecting and regulating neurodevelopmental processes in the foetal brain may provide new directions for treatment of neurodevelopmental disorders in infants who are exposed to perinatal insults and pathologies.

Changes in Neuroactive Steroid Concentrations After Preterm Delivery in the Guinea Pig

“…Expression of GFAP, a marker of reactive gliosis, is altered in the late gestation fetal guinea pig brain exposed to reduced concentrations of allopregnanolone in utero. 9 The observation in this study that GFAP expression was affected by neonatal sex and gestational age, with an increase in GFAP in male preterm brains, may suggest increased vulnerability to injury in this group. Indeed, endogenous protective processes have been reported in cultured astrocytes from female neonatal mice that are more resistant to injury and cell death than male astrocytes.…”

“…18 Steroids were then reextracted using diethyl-ether/n-hexane (50%, v/v). Allopregnanolone concentration in each sample was quantified by radioimmunoassay using an antibody supplied by Dr R.H. Purdy (Department of Psychiatry, Veterans Administration Hospital, San Diego, California) and tritiumlabeled allopregnanolone (5a- [9,11,12,3 H(N)]; PerkinElmer Life and Analytical Sciences, Boston, Massachusetts). Extraction efficiency was determined by the addition of tritiated allopregnanolone prior to extraction and used to correct for extraction loss.…”

Long-term effects of preterm birth on behavior and neurosteroid sensitivity in the guinea pig

“…Immunohistochemistry was performed on 8-μm sections of paraffin-embedded brains that were cut using a Leica RM2145 Microtome (Leica Microsystems Pty, North Ryde, Australia) (25,39). Tissues were dewaxed, incubated in citrate buffer (pH 6.0) and phosphate-buffered saline containing 3% hydrogen peroxide, and blocked for 1 h at room temperature in Bovine serum albumin blocking solution (0.5% w/v bovine serum albumin, 0.05% w/v Saponin, 0.05% v/v Sodium Azide in 0.1M phosphate-buffered saline).…”

Programming the brain: Common outcomes and gaps in knowledge from animal studies of IUGR

“…Volume ↓ cerebrum, E60 [162] ↓cerebellum E60 [142,162] Myelination ↓cerebrum, cerebellum, CA1 hippocampus, dorsal fornix, dorsal fimbria, corpus callosum, periventricular white matter, parasagittal white matter [119,121,143,206] =/↓ spine, age dependent [119] = subcortical white matter, d65 [143] Delayed maturation of myelin [162] ↓cerebral cortex, striatum [108] Thinner sheaths, signs of degeneration [108] Damage + lesions in cerebrum [108] + lesions, gliosis, axonal degeneration [109] Oligodendrocytes ↑ numbers in cerebellum [162] ASTROGLIOSIS Cerebrum = E52 [119] ↑E60, E62 [119,162] = E65 [143] ↑cortex [108,109] Striatum ↑ [108] Cerebellum = [119] ↑ E60 [162] Hippocampus = E65 [143] [79] ↓11% [90] ↓17.3% [128,129] ↓10-18% [116,212] = [125] Forebrain ↓10-15% [79,85] ↓ [129] ↓13-16% [145,162] ↓19% [212] = [125] Cortex ↓31% [128] ↓20% [217] Striatum ↓12% [212] Hippocampus = …”

“…Similarly, this review is limited to those models of 142 IUGR in which neurodevelopmental and/or cognitive outcomes have been reported. This section 143 describes key features of these models, including effects on fetal nutrient supply and metabolism, 144 and development and timing relative to neurodevelopment. Specific neurodevelopmental and 148 Models of IUGR based on maternal undernutrition (UN) differ from human IUGR associated with 149 poor placentation, in that restriction is largely of nutrients without substantial restriction of oxygen.…”