Location: Reproduction Research
Title: Differential gene regulation of steroidogenic transcripts and estradiol production following in vitro pig embryo elongation in alginate hydrogel three-dimensional matrix Authors
Submitted to: Reproduction, Fertility and Development
Publication Type: Abstract Only
Publication Acceptance Date: August 4, 2011
Publication Date: January 1, 2012
Citation: Miles, J.R., Sargus, C.N., Plautz, S.A., Vallet, J.L., Pannier, A.K. 2012. Differential gene regulation of steroidogenic transcripts and estradiol production following in vitro pig embryo elongation in alginate hydrogel three-dimensional matrix. Reproduction, Fertility and Development. 24(1):162 (Abstract #99). Technical Abstract: Between d 10 and 12 of gestation, the pig embryo elongates from a sphere to a long thin, filament. During this time, the embryo increases the production of estrogen via an increase in steroidogenic transcripts, which is critical for maternal recognition of pregnancy. To date, attempts to elongate porcine embryos in vitro have been unsuccessful. The objective of this study was to utilize alginate hydrogels to establish a culture system that promotes in vitro embryo elongation with a corresponding increase in steroidogenic transcripts and estradiol production. In three replicate collections, White crossbred gilts (n=15) were bred at d 0 of the estrous cycle. At d 9 of gestation, reproductive tracts were collected and flushed with RPMI-1640 containing antibiotics. Embryos were recovered, grouped according to size, and washed with RPMI-1640 containing antibiotics and 10% FBS. Embryos were randomly assigned to be encapsulated using a double encapsulation technique (0.7% sodium alginate and 1.5% calcium chloride solution) or used as controls. Encapsulated and control embryos were cultured for 96 h in CO2-pretreated RPMI-1640 containing antibiotics and 10% FBS at 38ºC, 5% CO2 in air and 100% humidity. Every 24 h, the embryos were imaged and half of the media was replaced. The removed media was stored at -20ºC and used to assess estradiol levels by radioimmunoassay. At the end of culture, a subset of encapsulated and control embryos were snap frozen and used to assess the expression level of steroidogenic transcripts (STAR, CYP11, and CYP19) using quantitative PCR. All data were analyzed using GLM procedures for ANOVA. Cell survival, assessed by blastocyst fragmentation and confirmed by live/dead staining in representative embryos, was greater (P=0.01) for encapsulated embryos (60.1±4.8%) compared with controls (33.3±4.8%). Of encapsulated embryos, 27% had some morphological change (minor flattening and tubal formation) and 14% had significant morphological changes (considerable flattening and tubal formation elongating through the gel), consistent with in vivo embryo elongation. In contrast, the control embryos had no morphological changes observed and remained spherical during culture. The expression levels of STAR, CYP11 and CYP19 were significantly (P<0.05) greater in encapsulated embryos compared with control embryos. Furthermore, a significant (P<0.01) time-dependent increase in estradiol levels in the culture media of encapsulated embryos was identified compared with controls and culture media alone. These results illustrate that cultured pig embryos encapsulated in alginate hydrogels undergo limited morphological changes with increased expression of steroidogenic transcripts and estrogen production. USDA is an equal opportunity provider and employer.