Fatty acid transporters in the porcine conceptus and early placenta and the effects of polyunsaturated fatty acids on trophoblast cells

This study aimed to determine whether fatty acids (FAs) may affect the function of the early porcine placenta. First, the expression of FA transporters (CD36, SLC27A) in conceptuses and placentae of days 10-11, 12-13, 15-16, 18-20, 25, and 30 pregnant gilts (n = 5-8 per group) was examined using Real-time PCR, Western blot, and immunohistochemistry. Then, primary trophoblast (pTr) cells from days 15-16 conceptuses were exposed to n-6 and n-3 polyunsaturated FAs (PUFAs) to study prostaglandin (PG) synthesis and the expression of genes related to FA action, angiogenesis, steroidogenesis, and lipid transport. Furthermore, pTr cell proliferation and adhesion in response to PUFAs were determined colorimetrically. Increased mRNA expression of CD36, SLC27A1, and SLC27A2 was detected in days 18-25 placentae compared with days 10-13 conceptuses. SLC27A4 and SLC27A6 expression was greater in days 10-11 spherical than in days 15-16 elongated conceptuses. SLC27A1, SLC27A4, and SLC27A6 were localized at the placenta-endometrium interface. PUFAs of n-6 series elevated PGE2 and PGI2 synthesis, whereas n-3 PUFAs stimulated PGE2 but inhibited PGI2 output. All PUFAs up-regulated the mRNA expression of CPT1A, a rate-limiting enzyme of FA β-oxidation. Moreover, docosahexaenoic acid (DHA) increased FABP5, SLC27A4, LDLR (lipoprotein receptor), and proangiogenic ANGPT1 and ANGPTL4 mRNA expression. DHA and arachidonic acid stimulated pTr cell proliferation, while linoleic and eicosapentaenoic acids increased cell adhesion. These results are the first demonstrating dynamic changes of FA transporter expression in peri-implantation conceptuses and developing placentae of the pig and indicate FA uptake by the early placenta. Furthermore, PUFAs may support placenta development by modulating gene expression, increasing PGE2 level, and promoting trophoblast cell viability and adhesion.