Hippocampal formation morphogenesis of the rats’ offspring after labour induction
Creators: name: Yuriyivna Mamai, Iryna
Publisher: name: University of Limerick
Year: 2025
Subjects: classificationCode: 42
subject: Health sciences
subject: FOS: Health sciences

description: Introduction: The rate of labour induction has significantly increased in recent decades. In the United States, over 22% of all women in labour undergo induction, with rates more than doubling since 1990 to 225 per 1,000 live births in 2006 [2]. By 2014, 23.2% of births in the US followed induced labour [56]. Labour induction may be medically indicated or chosen for non-medical reasons, termed 'elective induction' when there are no clear medical indications [167]. The appropriateness of elective induction at 39 weeks remains a topic of debate [56]. Given this debate, it's vital to study the potential effects of induction on fetal development. Our focus is on the hippocampus and dentate gyrus, key regions for understanding these effects due to ongoing neuronal development during critical brain maturation periods in both humans and rats [62]. Additionally, contemporary research has provided valuable insights into the developmental changes in these regions following exposure to various environmental and physiological factors, further justifying their selection for our investigation.Question: What structural changes occur in the hippocampus and dentate gyrus of offspring from rats induced into labour at term?Aim: To examine the morphological development of the hippocampus and dentate gyrus in rat offspring after labour induction using anatomical, histochemical, immunohistochemical, and electron microscopy methods.Methods: This study utilized a range of methods, including anatomical, morphometric, histological, immunohistochemical, electron microscopy, and statistical analyses. Offspring were euthanized at 1, 7, 14, 45, and 60 days of life. Body parameters such as weight and length then were measured. A comprehensive morphological study was then conducted, involving H&amp;E and Nissl staining, GFAP and NeuN expression analysis, and electron microscopy, to assess structural and developmental changes in the hippocampus following labour induction compared to control and intact groups.Results: The offspring of rats subjected to labour induction exhibited reduced weight (54,278±9,331 mg and 85,936±6,862 mg) and body length (87.2±3. mm, and 107.3±2.4 mm in the experimental and control groups, respectively) by day sixty. Offspring from induced labour exhibited the reductions in the area occupied by neuronal nuclei from the 1st (CA2: 18.95%±2.2% and 28.1%±1.8%; CA3: 17.98%±1.7% and 23, 03%±1.6%) to the 60th (DG: 16.6%±2.2% and 21.0%±1.8%; CA2: 16.2%±1.3% and 27.8%±1.5%; CA3: 16.1%±1.4% and 23.5%±1.9%) day of life, decreased cell density from the 14st (CA3: 4,5±0,7 and 3,4±0,7) to the 60th (CA1: 3.7±0.7 and 4.8±0, 8) day of life, and a decrease in the perikaryon perimeter from the 1st (CA1: 28.2±2.1 µm and 44.0±2.5 µm) to the 60th (DG: 26.6±1.5 µm and 36.8±2.3 µm; CA1: 41.0±1.5 µm and 48.5±2.8 µm; CA3: 59,9±2,5 and 54,2±2,2) day of life, in experimental animals compared to the control group, respectively. Increased GFAP expression on day 1 (DG: 49.88±2.9 and 36.6%±2.4%; CA1: 49.5±2.4 and 36.3%±2.8%; CA2: 47.94±2.3 and 36.6%±2.5%; CA3: 48, 71±2.6 and 36.81%±2.5% and 36.81%±2.5% in the experimental and control groups, respectively) and decreased NeuN expression on days 14, 45, and 60 (DG: 30, 5±2.2 and 41.3%±2.2%; CA1: 31.2%±2.4% and 41.5%±2.2%; CA2: 30.8%±2.1% and 41.3%±2.7%; CA3: 30.9%±2.5% and 41.1%±2.5% in experimental and control groups, respectively) were noted (all p&lt;0.05). Ultrastructural changes in astrocytic and synaptic processes, neuron organelles, oligodendroglia, and the hippocampal microcirculation were also observed in the experimental group.Conclusions: Our study revealed morphological changes in the hippocampus and dentate gyrus of offspring following labour induction, compared to control and intact groups. From day 1 to day 60, animals in the experimental group showed a decrease in the area occupied by nuclei, reduced cell density, and a reduction in perikaryon perimeter in the dentate gyrus and CA1, CA2, and CA3 hippocampal regions compared to controls. An increase of the GFAP expression on the first day of life, and a subsequent decrease of NeuN expression were observed by the 60th day of life in the offspring of rats after labour induction. Ultrastructural analyses revealed disruptions in synaptic terminals, oligodendroglia, neurons, and the microcirculatory system.