Effect of transient maternal hypotension on apoptotic cell death in foetal rat brain

Abstract

Background: Intrauterine perfusion insufficiency induced by transient maternal hypotension has been reported to be associated with foetal brain malformations. However, the effects of maternal hypotension on apoptotic processes in the foetal brain have not been investigated experimentally during the intrauterine period.

Aims: The aim of this study was to investigate the effects of transient maternal hypotension on apoptotic cell death in the intrauterine foetal brain.

Study design: Animal experimentation.

Methods: Three-month-old female Wistar albino rats were allocated into four groups (n=5 each). The impact of hypoxic/ischemic injury induced by transient maternal hypotension on the 15th day of pregnancy (late gestation) in rats was investigated at 48 (H17 group) or 96 hours (H19 group) after the insult. Control groups underwent the same procedure except for induction of hypotension (C17 and H17 groups). Brain sections of one randomly selected foetus from each pregnant rat were histopathologically evaluated for hypoxic/ischemic injury in the metencephalon, diencephalon, and telencephalon by terminal transferase-mediated dUTP nick end labelling and active cysteine-dependent aspartate-directed protease-3 (caspase-3) positivity for cell death.

Results: The number of terminal transferase-mediated dUTP nick end labelling (+) cells in all the areas examined was comparable in both hypotension and control groups. The H17 group had active caspase-3 (+) cells in the metencephalon and telencephalon, sparing diencephalon, whereas the C19 and H19 groups had active caspase-3 (+) cells in all three regions. The number of active caspase-3 (+) cells in the telencephalon in the H19 group was higher compared with the metencephalon and diencephalon and compared with H17 group (p<0.05).

Conclusion: Our results suggest that prenatal hypoxic/ischemic injury triggers apoptotic mechanisms. Therefore, blockade of apoptotic pathways, considering the time pattern of the insult, may constitute a potential neuroprotective approach for the detrimental effects of prenatal hypoperfusion.

Keywords: Apoptosis; foetal rat brain; hypotension; hypoxic; ischemic injury; pregnancy.

FIG. 1.

Histopathological evaluation of foetal brain sections. In the Hypotension 19 days group, localised oedematous changes are observed in the deep lateral periventricular wall in the telencephalon (haematoxylineosin, ×100). At higher magnification (haematoxylin-eosin ×400), necrotic cells are visible (black arrows) next to oedematous areas

FIG. 2. a, b.

Assessment of TUNEL (+) cells in foetal brain sections in Hypotension 17 days (a) and Hypotension 19 days (b) groups. A group of TUNEL (+) cells (black arrows) in the diencephalon region are seen (×400, methyl green counterstain)

FIG. 3. a–d.

Assessment of active caspase-3 (+) cells in foetal brain sections in the Control 17 days (a), Hypotension 17 days (b), Control 19 days (c), and Hypotension 19 days (d) groups. Active caspase-3 (+) cells in the metencephalon in the 17 days groups and in the diencephalon in the 19 days groups. (×400, inset: ×1000, haematoxylin counterstain)