Hsa_circ_0001550 impairs decidualization by regulating the proliferation and apoptosis of endometrial stromal cells

What is the molecular function of hsa_circ_0001550 in decidualization? Human endometrial stromal cells (HESC) were isolated from the endometrium tissues to build an in-vitro decidualization model. Different concentrations of medroxyprogesterone acetate (MPA) were used to observe whether the expression level of hsa_circ_0001550 was related to progesterone. Biological characteristics and distribution of hsa_circ_0001550 were determined by RNase R, actinomycin D (Act D) assay and cytoplasmic/nuclear fraction assay. Then the overexpression of hsa_circ_0001550 was achieved by adenovirus vector. Cell proliferation was determined by Cell Counting Kit-8 (CCK-8) assays. The cell cycle was assessed by flow cytometry analyses. Cell apoptosis was determined by annexin-V/propidium iodide double staining experiment and western blotting. The expression of hsa_circ_0001550 was decreased in decidua and decidualized HESC ( P < 0.001, P  = 0.014). Hsa_circ_0001550 is a covalently closed RNA molecule that was verified by RNase R assay and Act D assay ( P  = 0.012). Nuclear and cytoplasmic separation experiments confirmed that hsa_circ_0001550 was mainly distributed in the cytoplasm. Overexpression of hsa_circ_0001550 inhibited decidualization of HESC ( P < 0.0001). Furthermore, overexpression of hsa_circ_0001550 inhibited proliferation by decreasing the number of S phase cells ( P  = 0.033). Annexin-V/propidium iodide double staining experiment and western blotting revealed that overexpression of hsa_circ_0001550 promoted HESC apoptosis ( P < 0.001, P  = 0.0139). Hsa_circ_0001550 impairs decidualization of HESC. Progesterone decreases the expression of hsa_circ_0001550. The results may provide new insights into the cause of decidualization.