Abstract
Fibroblast growth factors (FGF) play an important role during embryo development. To date, the role of FGF and the respective receptors (FGFR) during the preimplantation phase in cattle are not fully characterized. We examined FGF1, FGF2, FGFR1, FGFR2, and FGFR3 in cyclic and early pregnant heifers at Days 12, 15, and 18 after insemination (Day 0). Endometrial FGF1 mRNA transcript abundance in heifers varied significantly with respect to the day after insemination, the pregnancy status, and their interaction. The expression was higher in nonpregnant than in pregnant heifers at Day 18. The conceptus transcripts abundance of FGFR2 and FGFR3 were significantly lower at Day 15 than 18. In the endometrium, FGF1 protein abundance significantly decreased from Day 12 onwards and FGF2 protein abundance showed a minor, but a significant increase at Day 15 in comparison to Days 12 and 18. We concluded that the decrease in FGF1 mRNA expression in pregnant heifers at Day 18 points towards a potential contribution of FGF1 in the preimplantation process. Additionally, successful embryo elongation might require a spatiotemporal FGF2 protein increase in the endometrium.
Highlights
Acidic (FGF1) and basic (FGF2) fibroblast growth factor (FGF) isoforms are well-characterized proangiogenic factors playing important roles in various physiological conditions, including the embryonic development [1,2]
FGF1 and/or FGF2 action influences embryo implantation [6] and mice lacking FGR1 and FGFR2 die before embryonic day of the estrous cycle (Day) 8.5 and 11, respectively [5]
We observed that the mRNA expression during early pregnancy period on Days 12, 15 and 18 after insemination was affected by the day of pregnancy (FGF1, FGFR1 and FGFR2) and status (FGF1) in both cyclic and pregnant heifers
Summary
Acidic (FGF1) and basic (FGF2) fibroblast growth factor (FGF) isoforms are well-characterized proangiogenic factors playing important roles in various physiological conditions, including the embryonic development [1,2]. FGF1 and/or FGF2 action influences embryo implantation [6] and mice lacking FGR1 and FGFR2 die before embryonic Days 8.5 and 11, respectively [5] This indicates that the preimplantation embryo is dependent on FGF [5]. The bovine uterine epithelium and the conceptus synthesize FGF2, and, between Days 14 and 17, FGF gene expression increases in the elongating conceptuses [12]. This indicates that FGF1 and FGF2 play critical roles during preimplantation in cattle. We aimed at elucidating the modulation of endometrial and embryonic acidic and basic FGF and the associated receptors during the preimplantation phase in cattle
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