Characterization of placental cholesterol transport: ABCA1 is a potential target for in utero therapy of Smith–Lemli–Opitz syndrome

Patients with Smith –L emli –O pitz syndrome (SLOS) are born with multiple congenital abnormalities. Postnatal cholesterol supplementation is provided; however, it cannot correct developmental malformations due to in utero cholesterol deficit. Increased transport of cholesterol from maternal to fetal circulation might attenuate congenital malformations. The cholesterol transporters Abca1, Abcg1, and Sr-b1 are present in placenta; however, their potential role in placental transport remains undetermined. In mice, expression analyses showed that Abca1 and Abcg1 transcripts increased 2–3-fold between embryonic days 13.5 and 18.5 in placental tissue; whereas, Sr-b1 expression decreased. To examine the functional role of Abca1, Abcg1 and Sr-b1 we measured the maternal–fetal transfer of 14 C-cholesterol in corresponding mutant embryos. Disruption of either Abca1 or Sr-b1 decreased cholesterol transfer by 30%. In contrast, disruption of the Abcg1 had no effect. Treatment of pregnant C57Bl/6 female mice with TO901317, an LXR-agonist, increased both Abca1 expression and maternal –f etal cholesterol transfer to the fetus. In an SLOS mouse model (Dhcr7 2/2 ), which is incapable of de novo synthesis of cholesterol, in utero treatment with TO901317 resulted in increased cholesterol content in Dhcr7 2/2 embryos. Our data support the hypothesis that Abca1, and possibly Sr-b1, contributes to transport maternal cholesterol to the developing fetus. Furthermore, we show, as a proof of principle, that modulating maternal –f etal cholesterol transport has potential for in utero therapy of SLOS.