Department of Animal & Poultry Sciences, Virginia Tech, Blacksburg, VA, USA.
Department of Animal Sciences, Texas A&M University, College Station, TX, USA.
Theriogenology. 2021 Aug;170:15-22. doi: 10.1016/j.theriogenology.2021.04.004. Epub 2021 Apr 28.
The use of in vitro produced embryos in dairy and beef cattle has increased in recent years, but compromised post-transfer pregnancy success prevents producers from capturing all the benefits this technology can provide. This study explored whether supplementing interleukin-6 (IL6) during in vitro embryo development influences post-transfer development of the embryo-proper, fetus and placenta during early gestation in cattle. Slaughterhouse-derived cumulus oocyte complexes underwent IVM (day -1) and IVF (day 0). On day 5 post-fertilization, embryos were treated with either 0 (CONT) or 100 ng/mL recombinant bovine IL6. No difference in blastocyst formation was detected on day 7.5 post-fertilization, but an increase (P < 0.05) in inner cell mass cell numbers and tendency for increased (P = 0.08) trophectoderm cell numbers were detected in IL6-treated blastocysts. A subset of the blastocysts was loaded individually into transfer straws, and embryo transfer (ET) was completed using estrous cycle stage-matched, nonlactating commercial beef and dairy cows. A subset of cows from each group underwent timed artificial insemination (TAI). Pregnancy rates were similar among all three treatment groups at day 28 and 70. No differences in crown-rump length (CRL), crown nose length (CNL), abdominal diameter (AD), or placental fluid volume (PFV) were detected between TAI and ET-IL6 groups. Reductions (P < 0.05) in CRL and AD were detected at day 56 and a tendency for a reduction (P = 0.08) in PFV was detected on day 35 when comparing the ET-CONT group with the TAI group. Reductions (P < 0.05) in CRL and PFV on day 28 and CNL and AD on day 56 as well as a tendency for a reduction (P = 0.08) in PFV on day 35 were detected when contrasting ET-CONT with ET-IL6. Circulating plasma pregnancy-associated glycoprotein concentrations were similar among all treatment groups. In summary, IL6 treatment to IVP embryos before ET produced pregnancies that more closely resembled TAI-generated pregnancies than pregnancies generated using conventionally cultured embryos. These findings failed to find any adverse effects of IL6 supplementation on early development of the embryo-proper and fetus or on placental activity. Rather, these observations suggest that IL6 treatment may normalize the developmental trajectory of the embryo-proper and fetus for in vitro produced embryos.
近年来，在奶牛和肉牛中使用体外生产的胚胎有所增加，但胚胎移植后妊娠成功率不理想，这使得生产者无法充分利用这项技术所能带来的好处。本研究探讨了在体外胚胎发育过程中补充白细胞介素 6（IL6）是否会影响牛在早期妊娠期间胚胎、胎儿和胎盘的后期发育。从屠宰场获得的卵丘卵母细胞复合物进行 IVM（第-1 天）和 IVF（第 0 天）。受精后第 5 天，胚胎分别用 0（CONT）或 100ng/ml 重组牛 IL6 处理。在受精后第 7.5 天，未检测到囊胚形成的差异，但在 IL6 处理的囊胚中检测到内细胞团细胞数量增加（P<0.05）和滋养外胚层细胞数量增加的趋势（P=0.08）。将一部分囊胚单独装入移植吸管中，然后使用发情周期阶段匹配的非泌乳商业肉牛和奶牛进行胚胎移植（ET）。每组中的一部分牛进行定时人工授精（TAI）。在第 28 天和第 70 天，所有三组治疗组的妊娠率相似。在 TAI 和 ET-IL6 组之间，未检测到冠臀长（CRL）、冠鼻长（CNL）、腹径（AD）或胎盘液体积（PFV）的差异。在第 56 天，与 TAI 组相比，ET-CONT 组的 CRL 和 AD 降低（P<0.05），在第 35 天，PFV 降低的趋势（P=0.08）。在第 28 天和第 56 天，CRL 和 PFV 以及 CNL 和 AD 降低，在第 35 天，PFV 降低的趋势（P=0.08），当将 ET-CONT 与 ET-IL6 进行对比时，发现了这些变化。所有治疗组的循环血浆妊娠相关糖蛋白浓度相似。总之，在 ET 之前对 IVP 胚胎进行 IL6 处理，产生的妊娠与 TAI 产生的妊娠更相似，而不是与常规培养的胚胎产生的妊娠相似。这些发现未能发现 IL6 补充对胚胎和胎儿的早期发育或胎盘活性有任何不良影响。相反，这些观察结果表明，IL6 处理可能使体外生产的胚胎的胚胎和胎儿的发育轨迹正常化。
