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Heat shock of porcine zygotes immediately after oocyte activation increases viability
S Clay Isom1, Liangxue Lai, Randall S Prather
1Division of Animal Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA. sci345@mizzou.edu
Insights
Applying heat shock immediately after oocyte activation significantly improves the in vitro development of porcine embryos. This early heat treatment enhances cleavage and blastocyst rates for parthenogenetically activated, in vitro fertilized, and somatic cell nuclear transfer embryos.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Embryology
Background:
- Optimizing in vitro embryo production is crucial for livestock breeding and research.
- Heat shock is a known stressor that can affect embryonic development.
- Understanding the precise timing of heat shock application is key to manipulating developmental outcomes.
Purpose of the Study:
- To investigate the impact of different heat shock timing strategies on the developmental potential of porcine embryos.
- To determine if early heat shock enhances in vitro development in parthenogenetically activated (PA) embryos.
- To assess the effects of heat shock timing on in vitro fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos.
Main Methods:
- Parthenogenetically activated (PA) porcine embryos were subjected to a 9-hour heat shock at 42°C at different time points post-activation (0-9, 13-22, or 22-31 hours post-activation).
- In vitro fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos were also exposed to heat shock treatments.
- Developmental parameters including cleavage rates, cell numbers at different stages, and blastocyst rates were analyzed.
Main Results:
- Heat shock applied from 0-9 hours post-activation (09HS) significantly improved 24-hour cleavage rates, day 5 cell numbers, day 7 blastocyst rates, and day 7 cell numbers in PA embryos compared to other treatments and controls.
- Both IVF and SCNT embryos showed increased cleavage rates when heat shocked immediately after fertilization or activation, respectively.
- Blastocyst rates showed only modest or no significant improvement in IVF and SCNT embryos, respectively.
Conclusions:
- Applying heat shock immediately after oocyte activation dramatically enhances the developmental potential of PA porcine embryos.
- Early post-activation heat shock can improve early cleavage rates in IVF and SCNT embryos.
- Further research into this phenomenon could lead to more efficient in vitro production of PA, IVF, and SCNT embryos.
Abstract:
We evaluated the effect of different timing variations of an applied heat shock on parthenogenetically activated (PA) porcine embryos. PA embryos were heat shocked for 9 hr at 42 degrees C from either 0-9 hr post activation (hpa; 09HS), 13-22 hpa (1322HS), or 22-31 hpa (2231HS). Analysis of 24-hr cleavage rates (P < 0.0001), day 5 cell numbers (P < 0.005), day 7 blastocyst rates (P < 0.0001), and day 7 cell numbers (P < 0.05) showed that 09HS embryos developed more successfully in vitro than did all other treated and control embryos. In vitro fertilized (IVF) embryos were exposed to similar heat treatments as described for PA embryos, and embryos derived from somatic cell nuclear transfer (SCNT) were exposed only to the control and 09HS treatments to assess the effects of the different heat treatments on the timing of first cleavage and development to blastocyst. Embryos derived from both IVF and SCNT showed higher proportions of cleaved embryos on day 1 of development when heat shocked immediately after fertilization or fusion/activation as compared to NHS controls (P < 0.05). Blastocyst rates however, showed only modest (IVF; P = 0.089) or no (SCNT; P > 0.1) improvement as compared with control embryos. In summary, exposing PA embryos to elevated temperatures immediately after oocyte activation results in dramatically enhanced developmental potential. A thorough characterization of this phenomenon may yield findings that can serve to increase the efficiency with which PA, IVF, and SCNT embryos are produced in vitro.
