Fibulin-5 is upregulated in decidualized human endometrial stromal cells and promotes primary human extravillous trophoblast outgrowth.

Interactions between the highly invasive trophoblasts and the maternal uterine decidual extracellular matrix (ECM) are crucial in the determination of a successful pregnancy. Fibulin-5 (FBLN5) is a member of the fibulin family that alters cell adhesive and invasive properties and is expressed in human villous cytotrophoblasts. We aimed to determine the expression and immunolocalization of FBLN5 in human first trimester decidua and examine the effect of FBLN5 in trophoblast invasion in vitro using a first trimester placental villous outgrowth assay. We demonstrated that FBLN5 mRNA expression is upregulated in response to cAMP-mediated decidualization of primary human endometrial stromal cells, although FBLN5 itself does not enhance decidualization. We reported for the first time, FBLN5 protein production in first trimester decidual cells and also co-localization to HLAG-positive EVTs in first trimester decidua. Consequently, we investigated the effects of exogenous FBLN5 on placental villous outgrowth in vitro and demonstrated that FBLN5 promotes EVT migration/invasion. This is the first study to identify FBLN5 in decidualized human endometrial stromal cells, first trimester decidua and EVT and determine a functional role for FBLN5 in human EVTs, suggesting that decidual and or EVT-derived FBLN5 regulates EVT invasion and placentation in women.