AT-rich interactive domain 1A protein expression in normal and pathological pregnancies complicated by preeclampsia.

AT-rich interactive domain 1A (ARID1A, as known as BAF250a) is a subunit of human switch/sucrose nonfermentable chromatin remodeling complex with tumour suppressor function. Mutations of Arid1a have been reported in many human cancers and low expression of this protein has been correlated to a poor prognosis outcome in patients affected by some types of cancer. Although there are many studies regarding ARID1A functions in cancer, little is known about its role in regulating cell differentiation and normal tissues homeostasis. Here, we investigate ARID1A expression in normal placental tissues of first and third trimester of gestation and in pathological placental tissues of pregnancy complicated by preeclampsia (PE) and intrauterine growth restriction (IUGR) to evaluate a possible role of this protein in trophoblast differentiation. We found that ARID1A was specifically expressed in villous and extravillous cytotrophoblastic cells in normal placentas whereas syncytiotrophoblast was negative. Interestingly, ARID1A was expressed in both cytotrophoblastic cells and syncytiotrophoblast in placentas affected by PE and PE-IUGR. Moreover, ARID1A was also present in syncitial knots of pathological placentas. The present results indicate that ARID1A is a good marker of poor trophoblast differentiation in these pathologies, because the significant high positive staining in syncytiotrophoblast nuclei may suggest a poor differentiation of this trophoblast layer due to the cytotrophoblast cells fusion with the syncytiotrophoblast overlaying before arresting their cell cycle.