Transplacental tranfer of nanoparticles inhaled due to maternal exposure to filtered diesel engine exhaust during pregnancy in a rabbit model
Résumé
Epidemiological studies in humans and animal experiments indicate that gestational exposure to airborne pollution, in particular diesel engine exhaust (DE), reduces birth weight, with effects depending on exposure duration, gestational window and nanoparticle (NP) concentration. Furthermore, whether the inhaled NP can reach the fetuses via a transplacental transfer remains unknown. In this study we used a rabbit model to evaluate the transport of maternally inhaled DE NP from the lungs to the placenta and to fetal organs using transmission electron microscopy (TEM). Pregnant females were exposed to diluted (1mg/m3), filtered DE (mean NP diameter ≈ 69 nm) or clean air for 2 hours/day, 5 days/week by nose-only exposure during 20 days in a 31-day gestation. At 28th day post-conception, the females were euthanized. Maternal lung samples as well as placental labyrinthine area, fetal liver and spleen were collected randomly from 4 fetuses in each litter and subsequently treated according to a classical TEM preparation protocol. The presence of NP was evaluated on ultrathin sections (75 nm). NP were identified in lungs of exposed does, in the alveoli, in type 1 pneumocytes and within blood vessels. When observed in the lung of exposed females, NP were also observed in the placenta, i.e. in the maternal blood space, close to the microvillous membrane, in trophoblastic cells, and both free and in fetal red blood cells with the fetal compartment. No NP were observed in control placentas. Some NP were also identified in the liver and the spleen of fetuses whose placenta contained NP, demonstrating transplacental transfer and accumulation in fetal organs. These results demonstrate that maternal exposure to DE during gestation at levels close to urban pollution leads to the transfer of the inhaled NP from maternal lung to the placenta and fetal organs.