42 Adrenomedullin Stimulates Proliferation, Migration and Adhesion of Porcine Trophectoderm Cells Via CALCRL-AKT-TSC2-MTORC1 Cell Signaling Pathway

Abstract

Abstract Adrenomedullin (ADM) as a highly conserved peptide hormone has been reported to increase significantly in the uterine lumen during the peri-implantation period of pregnancy in pigs, but its functional roles in growth and development of porcine conceptus (embryonic/fetus and its extra-embryonic membranes) as well as underlying mechanisms remain largely unknown. Therefore, we conducted in vitro experiments using our established porcine trophectoderm cell line (pTr1) isolated from day -12 porcine conceptuses to test the hypothesis that porcine ADM stimulates cell proliferation, migration and adhesion via AKT-TSC2-MTOR cell signaling pathway in pTr1 cells. The pTr1 cells were cultured in DMEM/F12 medium with 10% fetal bovine serum (FBS), 50 U/mL penicillin, 50 μg/mL streptomycin, 0.1 mM each for nutritionally nonessential amino acids, 1 mM sodium pyruvate, 2 mM glutamine, and 4 μg/mL insulin. Opti-MEM supplied with 2.5% (vol/vol) charcoal-stripped FBS was used for siRNA-mediated knockdown targeting non-treated control (siNTC) or specific genes including ADM (siADM) and its shared receptor component calcitonin-receptor-like receptor (CALCRL; siCALCRL). Cells were starved in FBS- and insulin-free medium for 24 hours before treatment. For proliferation assay, cell numbers were determined by staining with Janus-Green B after 48 h incubation. For migration assay, cells were treated with ADM after straight scratch in 6-well plates, and area of cell migration was calculated after 12 h treatment. For adhesion assay, cells were trypsinized in T-25 flasks and allowed for seeding in 96-well plates with density of 2×105 cells/0.2 mL/well, and the numbers of attached cells were determined after 12 h incubation. Western blot analyses were used to determine the expressions of target proteins at total and phosphorylated level. Porcine ADM at 10-7 M stimulated (P < 0.05) pTr1 cell proliferation, migration and adhesion by 1.4%-, 1.5%- and 1.2%-folds, respectively. These ADM-induced effects were abrogated (P < 0.05) by siADM and siCALCRL, as well as by rapamycin, the inhibitor of mechanistic target of rapamycin (MTOR). Using siRNA-mediated knockdown of CALCRL coupled with Western blot analyses, ADM signaling transduction was determined in which ADM binds to CALCRL to increase phosphorylation of MTOR, its downstream effectors (4EBP1, P70S6K, and S6), and upstream regulators (AKT and TSC2). Collectively, these results suggest that porcine ADM in histotroph act on its receptor component CALCRL to activate AKT-TSC2-MTOR, particularly MTORC1 signaling cascade, leading to elongation, migration and attachment of conceptuses. This research was supported by Agriculture and Food Research Initiative Competitive Grant no. 2022-67015-36491 from the USDA National Institute of Food and Agriculture.