• secreted phosphoprotein 1 (SPP1);
  • osteopontin (OPN);
  • porcine embryos;
  • in vitro development;
  • apoptosis


An optimal environment for fertilization and early embryonic development is provided by the mammalian oviduct and uterus. The secretory cells lining the lumen of the oviduct and uterus synthesize and secrete proteins that have been shown to interact with and influence the activities of gametes and embryos. Western blotting in this study demonstrated that a 50-kDa secreted phosphoprotein 1 (SPP1) form was present in the uterus on Days 0, 3, and 5 in pregnant and nonbred gilts, and the concentration of SPP1 on Day 0 was higher than on Days 3 and 5 in pregnant gilts, but in nonbred gilts the concentration of SPP1 on Day 0 was higher than Day 3, but not Day 5. In addition, we show that addition of 0.1 µg/ml SPP1 to the culture medium after fertilization increased the percent cleaved (24 hr: 23.6 ± 1.29a vs. 18.7 ± 0.65b (2-cell %)), and the percent blastocyst (37.2 ± 1.12a vs. 30.9 ± 0.56b) derived from IVF (P < 0.05). In parthenogenetic-derived embryos the percent cleaved was increased due to SPP1 at 24 hr (24.0 ± 1.59a vs. 19.7 ± 1.59b (>2-cell %)), and at 48 hr (72.9± 2.99a vs. 63.3 ± 2.99b), but not the percent blastocyst. By TUNEL assay, SPP1 decreased both apoptosis (7.9 ± 0.04a vs. 13.1 ± 0.02b) and the percent fragmentation (45.2  ± 0.07a vs. 58.8  ± 0.03b). We conclude that SPP1 can improve development in vitro possibly by reducing the rate of apoptosis. Mol. Reprod. Dev. 75: 291–298, 2008. © 2007 Wiley-Liss, Inc.