Reductions in Complete Rat Serum Yields Promising Results in Whole Embryo Culture

Nomrota Majumder ‘21

Figure 1: Whole Embryo Culture utilizes large amounts of 100% rat serum, but scientists are attempting to substitute this in culture media to lower costs, time, and labor.

Whole Embryo Culture (WEC) came about in the 1950s as a way to observe patterns in mammalian development, investigate birth defects, and analyze explanted organogenesis-stage rodent embryos. Since then, it has been a very treasured technique in biological research methods. Since WEC is conducted in vitro, a serum properly suited for an embryo is crucial to the process, and ever since its invention, rat serum has been the ideal one as a result of its ability to sustain life and development outside the uterus. However, inherent with the use of rat serum is high costs, labor, and time for its preparation. Scientists have thus been trying to find a substitute for this culture for years. From testing serum from calves all the way to that from humans, nothing truly supported normal embryonic growth in culture. To alleviate this issue, researchers from UCL GOS Institute of Child Health shifted from the idea of replacing rat serum in culture to reducing it and tested mouse embryo in serum-free media as well as rat serum diluted with defined media. 

Researchers collected mouse embryo on embryonic day 8.5 and treated them for 24 hours. The embryos were separated into three groups: media with no serum, media with diluted serum, and 100 percent rat serum. After 24 hours, the different cultures were observed for developmental deficits and observations surrounding yolk sac circulation, protein content, and cranial neural tube closure, or the completion of the development of the neural tube. Postculture embryo scoring showed maximum yolk sac circulation (fully turned), highest protein concentration, and full neural tube closure in the control ( 100% rat serum), as expected, and close results in the diluted rat serum cultures. The serum-free media, however, showed little to no development corresponding to these criteria. Researchers concluded this to confirm that although rat serum cannot be completely avoided for WEC, it can be reduced and diluted, yielding similar results. 

Similarities in embryonic growth patterns exist between rodents as well as humans as a result of evolutionary relationships and DNA. As a result, WEC is a valuable tool to understanding and alleviating embryonic disease and prevent birth defects. If further refinements are made to partially or fully substitute 100% rat serum, scientists can further investigate embryonic development quicker and easier without cost and time restrictions, which would ultimately prove beneficial to the emergence of embryonic and neonatal treatment.



  1. L. Culshaw, et. al., Mouse whole embryo culture: Evaluating the requirement for rat serum as culture medium. Birth Defects Research, 1-13(2019). doi: 10.1002/bdr2.1538.
  2. Image retrieved from:

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