Male fetal sex affects uteroplacental angiogenesis in growth restriction mouse model†.

Abnormally increased angiotensin II activity related to maternal angiotensinogen (AGT) genetic variants, or aberrant receptor activation, is associated with small-for-gestational-age babies and abnormal uterine spiral artery remodeling in humans. Our group studies a murine AGT gene titration transgenic (TG; 3-copies of the AGT gene) model, which has a 20% increase in AGT expression mimicking a common human AGT genetic variant (A[-6]G) associated with intrauterine growth restriction (IUGR) and spiral artery pathology. We hypothesized that aberrant maternal AGT expression impacts pregnancy-induced uterine spiral artery angiogenesis in this mouse model leading to IUGR. We controlled for fetal sex and fetal genotype (e.g., only 2-copy wild-type [WT] progeny from WT and TG dams were included). Uteroplacental samples from WT and TG dams from early (days 6.5 and 8.5), mid (d12.5), and late (d16.5) gestation were studied to assess uterine natural killer (uNK) cell phenotypes, decidual metrial triangle angiogenic factors, placental growth and capillary density, placental transcriptomics, and placental nutrient transport. Spiral artery architecture was evaluated at day 16.5 by contrast-perfused three-dimensional microcomputed tomography (3D microCT). Our results suggest that uteroplacental angiogenesis is significantly reduced in TG dams at day 16.5. Males from TG dams are associated with significantly reduced uteroplacental angiogenesis from early to late gestation compared with their female littermates and WT controls. Angiogenesis was not different between fetal sexes from WT dams. We conclude that male fetal sex compounds the pathologic impact of maternal genotype in this mouse model of growth restriction.

Fetal Renal DNA Methylation and Developmental Programming of Stress-Induced Hypertension in Growth-Restricted Male Mice.

Fetal growth restriction (FGR) is associated with developmental programming of adult onset hypertension, which may be related to differences in nephron development. Prior studies showed that maternal nutrient restriction is associated with reduced nephrogenesis in rodents, especially in male progeny. We hypothesized that maternal genetic risk for FGR may similarly affect fetal kidney development, leading to adult onset hypertension. We employed an angiotensinogen (AGT) gene titration transgenic (TG) construct with 3 copies of the mouse AGT gene that mimics a common human genotype (AGT A[-6]G) associated with FGR. We investigated whether FGR in 2-copy (wild type, [WT]) progeny from 3-copy TG dams leads to developmental programming differences in kidney development and adult blood pressure compared with age- and sex-matched controls. Progeny were tested in the late fetal period (e17.5), neonatal period (2 weeks of age), and as young adults (12 weeks). We measured weights, tested for renal oxidative stress, compared renal DNA methylation profiles, counted the number of glomeruli, and measured adult blood pressure ± stress. Progeny from TG dams were growth restricted with evidence of renal oxidative stress, males showed fetal renal DNA hypermethylation, they had fewer glomeruli, and they developed stress-induced hypertension as adults. Their female siblings did not share this pathology and instead resembled progeny from WT dams. Surprisingly, glomerular counts in the neonatal period were not different between sexes or maternal genotypes. In turn, we suspect that differences in fetal renal DNA methylation may affect the long-term viability of glomeruli, rather than reducing nephrogenesis.

Altered vertebral and femoral bone structure in juvenile offspring of microswine subject to maternal low protein nutritional challenge.

Epidemiological studies suggest skeletal growth is programmed during intrauterine and early postnatal life. We hypothesize that bone development may be altered by maternal diet and have investigated this using a microswine model of maternal protein restriction (MPR). Mothers were fed a control diet (14% protein) or isocaloric low (1%) protein diet during late pregnancy and for 2 weeks postnatally. Offspring were weaned at 4 weeks of age to ad lib or calorie-restricted food intake groups. Femur and vertebra were analysed by micro computed tomography in offspring 3-5 months of age. Caloric restriction from 4 weeks of age, designed to prevent catch-up growth, showed no significant effects on bone structure in the offspring from either maternal dietary group. A maternal low protein diet altered trabecular number in the proximal femur and vertebra in juvenile offspring. Cortical bone was unaffected. These results further support the need to understand the key role of the nutritional environment in early development on programming of skeletal development and consequences in later life.

Effects of postweaning calorie restriction on accelerated growth and adiponectin in nutritionally programmed microswine offspring.

Poor prenatal development, followed by rapid childhood growth, conveys greater cardiometabolic risk in later life. Microswine offspring exposed to perinatal maternal protein restriction [MPR; "low protein offspring" (LPO)] grow poorly in late-fetal/neonatal stages. After weaning to an ad libitum (AL) diet, LPO-AL exhibit accelerated growth and fat deposition rates with low adiponectin mRNA, despite low-normal body fat and small intra-abdominal adipocytes. We examined effects of caloric restriction (CR) on growth and metabolic status in LPO and normal protein offspring (NPO) randomized to AL or CR diets from weaning. CR transiently reduced growth in both LPO and NPO, delaying recovery in female LPO-CR. Over 7.5-12.5 weeks, linear growth rates in LPO-CR were slower than LPO-AL ( P < 0.001) but exceeded NPO-AL; body weight growth rates fell but were lower in LPO-CR versus NPO-CR. Linear acceleration ceased after 12 weeks. At 16 weeks, percent catch-up in LPO-CR was reduced versus LPO-AL ( P < 0.001). Plasma growth hormone was low in LPO ( P < 0.02). CR normalized fat deposition rate, yet adiponectin mRNA remained low in LPO-CR ( P < 0.001); plasma adiponectin was low in all LPO-AL and in female LPO-CR. Insulin sensitivity improved during CR. We conclude that in LPO: 1) CR delays onset of, but does not abolish, accelerated linear growth, despite low growth hormone; 2) CR yields stunting via delayed onset, plus a finite window for linear growth acceleration; 3) MPR lowers adiponectin mRNA independently of growth, adiposity, or adipocyte size; and 4) MPR reduces circulating adiponectin in LPO-AL and female LPO-CR, potentially enhancing cardiometabolic risk.