Cell localization of SLC2 glucose transporter family member mRNA in endometria and placentae from pregnant pigs

Authors: BURROUGHS, CHELSIE - Texas A&M University; LANDERS, MCKINSEY - Texas A&M University; GAO, HAIJUN - Texas A&M University; Vallet, Jeff; WU, GUOYAO - Texas A&M University; BURGHARDT, ROBERT - Texas A&M University; BAZER, FULLER - Texas A&M University; JOHNSON, GREGORY - Texas A&M University

Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2014
Publication Date: 7/19/2014
Citation: Burroughs, C.A., Landers, M., Gao, H., Vallet, J.L., Wu, G., Burghardt, R.C., Bazer, F.W., Johnson, G.A. 2014. Cell localization of SLC2 glucose transporter family member mRNA in endometria and placentae from pregnant pigs [abstract]. In: Society for the Study of Reproduction, 47th annual meeting, 19-23 July 2014, Grand Rapids, MI. Abstract 104.

Interpretive Summary:

Technical Abstract: Glucose is a major hexose sugar involved with fetal and placental development, but fructose concentrations are notably higher than glucose in porcine fetal blood and allantoic fluid. Fructose plays a minor role as an energy source, but is used as a substrate in the biosynthesis of glycosaminoglycans, phospholipids, and nucleic acids that support conceptus development. Additionally, glucose is converted to fructose in the porcine placenta. While the hexose sugar functions in the placenta are being defined, the transport mechanisms that facilitate glucose and fructose movement from maternal to fetal circulation remain to be delineated. We previously quantified mRNA expression for members of the solute carrier family 2 (SLC2A) of facilitated glucose transporters including SLC2A1, SLC2A3, SLC2A4, SLC2A5, and SLC2A8 in endometrium and noted their regulation by ovarian steroids in pigs. In situ hybridization (ISH) on paraffin-embedded sections was used to localize mRNAs for SLC2A1, SLC2A3, SLC2A4, SLC2A5, and SLC2A8 to specific endometrial and placental cell types. In Exp 1, gilts were hysterectomized on Day 9, 10, 12, 15, 25, 30, 60, or 85 of pregnancy. SLC2A1 is expressed in the luminal (LE) and glandular (GE) epithelia from Day 9 to at least Day 85 of pregnancy. SLC2A1 is also expressed in the trophectoderm/chorion (TE/CE), although at lower levels than in uterine LE. SLC2A3 is expressed in TE/CE throughout pregnancy with increased expression in cells of the areolae. SLC2A4 is expressed in the LE and GE beginning at Day 12. SLC2A5 is found in the LE and GE beginning at Day 12 with increased expression at Day 30 in uterine LE and GE and fetal CE. SLC2A8 is highly expressed in uterine LE and GE from Days 10 to 15 of pregnancy with decreased expression through Day 85. In Exp 2, cyclic gilts were injected daily (Days 11-14) with estradiol benzoate (i.m.) or vehicle and hysterectomized on Day 15 of pseudopregnancy. SLC2A1, SLC2A4 and SLC2A8 expression increased in response to estradiol, but there was no effect on expression of SLC2A3 and SLC2A5. In Exp 3, gilts were ovariectomized on Day 12, injected daily with progesterone (P4; i.m.) or vehicle for 28 days, and hysterectomized on Day 40. P4 increased expression of SLC2A1, SLC2A3, SLC2A4 and SLC2A5 in uterine LE and GE. There was no effect of P4 on expression of SLC2A8. Collectively, SLC2A8 mRNA levels increased during the peri-implantation period when secretion of components of histotroph is high, while expression of SLC2A5 was highest between Days 30 and 85 of pregnancy. SLC2A1, SLC2A3 and SLC2A4 were expressed throughout pregnancy in uterine LE and GE, but SLC2A3 expression was restricted to fetal TE/CE. Hexose sugars are, therefore, differentially transported depending on cell type and pregnancy stage. Pigs have a true epitheliochorial placenta, which requires nutrients to cross multiple cell layers during transport from maternal to fetal circulation. Each cell layer has transporters on the apical and basal surfaces that facilitate nutrient movement. However, the same transporters are not typically present on both apical and basal cell surfaces; it is this differential cellular localization of the transporters that aids in moving nutrients across both plasma membranes. Future studies will localize SLC2A1, SLC2A3, SLC2A4, SLC2A5, and SLC2A8 proteins specifically to the apical or basal cell surfaces in pig endometrial and placental cells.