Immunolocalization of acidic and basic fibroblast growth factors in porcine uterine and conceptus tissues.

Immunohistochemical techniques were used to localize acidic and basic fibroblast growth factor (FGF) polypeptides in porcine uterine and conceptus tissues collected on Days 10 through 14 of gestation, which is the peri-implantation period, and in uterine tissues collected on the same days of the estrous cycle. Our results demonstrate differential expression of acidic and basic FGF (aFGF, bFGF) in porcine uterine and conceptus tissues. Localization of these peptides in the uterus of cycling and pregnant pigs was different from that reported for other species, suggesting species-specific roles for FGFs in early pregnancy. Increases in both cytoplasmic and nuclear bFGF immunostaining were detected in uterine luminal and glandular epithelial cells from Days 10 to 14 of gestation but not in the uterine epithelium of cycling pigs. Acidic FGF immunostaining was not detected in luminal or glandular epithelium of either cycling or pregnant uterine tissue; however, differential stromal staining was observed. Uterine tissues collected from pigs on Days 10-14 of the estrous cycle had diffuse aFGF immunostaining throughout the stroma. During early pregnancy, however, intense aFGF immunostaining was concentrated around the glandular epithelial and below the luminal epithelial cells as gestation progressed. Basic FGF, but not aFGF, was detected in porcine conceptuses collected during the peri-implantation period (Days 10-14 of gestation). Although both acidic and basic FGF belong to the same family of proteins, results of the present study indicate that they likely play different roles in uterine function and conceptus development in pigs.