PQCT Analysis of Cortical Bone in Rats Exposed to High Levels of Cortisol in‐utero

Abstract

Unperturbed fetal development is essential for future health of an individual. Previous studies have linked diseases of aging to harmful alterations that happen during fetal development. Given the significant long‐term impact that intrauterine environment has on an individual's life, it was hypothesized that maternal stress during pregnancy will have negative effects on the offspring's bone density and cross‐sectional area. To test this, twenty‐eight female and seven male Wistar rats (Rattus norvegicus) were purchased and bred to produce 176 offspring. During pregnancy, dams were randomly divided into four groups (n=7, per group) and immobilization stress induced as follows; Group 1 (GW1): immobilization stress on days 1–7 of pregnancy, Group 2 (GW2): on days 8–14, Group 3 (GW3): on days 15–21, Group 4 (Controls): left undisturbed. Maternal cortisol hormone, food intake, and weight gain were monitored during pregnancy. Pups were raised under normal laboratory conditions and sacrificed at ages: 4, 8, 12, and 16 weeks to determine the effect of prenatal stress. At necropsy, the femur was removed and preserved for image analysis.Differences among groups were determined by T‐test or analysis of variance (ANOVA). P values ≤ 0.05 were considered significant. Cortisol hormone levels in controls were lower than those of stressed animals. Stressed dams consumed 12.5% less food per day compared to controls. Animals in GW1 and GW2 gained less weight during pregnancy but had larger litters than did GW3 or the control group. Offspring born to GW3 were heavier compared to all other groups. The femurs were scanned using the XCT Research SA+ peripheral Quantitative Computed Tomography (pQCT). Preliminary analysis of cortical bone shows the GW1 males as having a significantly lower cortical thickness compared to the controls at the age of 8, 12 and 16 weeks. The GW1 males also had a significantly lower periosteal perimeter and endosteal perimeter compared to controls at the age of 8 weeks. There was no significant difference in cortical thickness, periosteal perimeter and endosteal perimeter of females. This preliminary analysis shows that bone development in males was significantly impacted when fetuses in this study were exposed to high levels of cortisol in‐utero during the first week of gestation. Analysis of the remaining data is ongoing.