Masashige Kuwayama
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The Modern Laboratory
Masashige Kuwayama
A Tokyo embryologist who learnt his craft with cattle and then made egg freezing work for women.
Starting with cattle. Masashige Kuwayama began in animal embryology. In the early 1990s he worked at a livestock breeding centre in Tokyo, studying cattle eggs and embryos made in the laboratory, and in 1994 he published on vitrifying cattle blastocysts.
Denmark. He then worked at the Danish Institute of Agricultural Sciences, where he joined Gábor Vajta and colleagues on the open pulled straw, published in 1998. In 1997 the same group reported pig embryos successfully cryopreserved by vitrification.
A drop on a strip. Back in Tokyo he worked as an embryologist at Kato Ladies' Clinic. There he pushed the idea of minimal volume as far as it would go. Human eggs were vitrified in a droplet of less than a tenth of a microlitre, resting on a fine strip of plastic, and plunged into liquid nitrogen. In 2005, with Vajta, Stanley Leibo and a clinic colleague, he reported that 58 of 64 eggs survived warming, and that seven healthy babies had been born, with more pregnancies continuing.
A method used worldwide. He applied the same approach to embryos and blastocysts. In 2015 the American College of Embryology named him Embryologist of the Year, noting that his vitrification methods had been used in more than two million clinical cases in over 65 countries.
Much of the egg freezing done today, for patients, for donors and for women choosing to wait, follows the path he opened.
Also see: Gábor Vajta, Stanley Leibo
About the sources
- American College of Embryology. Embryologist of the Year 2015: Dr Masashige Kuwayama, PhD. embcol.org, accessed October 2026.
- Kuwayama M. Highly efficient vitrification for cryopreservation of human oocytes and embryos. Theriogenology 2007;67(1):73–80. PMID 17055564.
- Kuwayama M, Vajta G, Kato O, Leibo SP. Highly efficient vitrification method for cryopreservation of human oocytes. Reproductive BioMedicine Online 2005;11(3):300–308 (affiliation: Kato Ladies' Clinic, Tokyo). PMID 16176668.
- Vajta G, Holm P, Kuwayama M, et al. Open pulled straw (OPS) vitrification: a new way to reduce cryoinjuries of bovine ova and embryos. Molecular Reproduction and Development 1998;51(1):53–58. PMID 9712317.
- Kuwayama M, Holm P, Jacobsen H, Greve T, Callesen H. Successful cryopreservation of porcine embryos by vitrification. Veterinary Record 1997;141(14):365 (affiliation: Danish Institute of Agricultural Sciences). PMID 9351185.
- Kuwayama M, Fujikawa S, Nagai T. Ultrastructure of IVM-IVF bovine blastocysts vitrified after equilibration in glycerol 1,2-propanediol. Cryobiology 1994;31(5):415–422 (affiliation: Livestock Improvement Association, Tokyo). PMID 7988150.
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Compiled with AI-assisted research and checked against the original sources. Not yet peer-reviewed. Corrections are warmly welcomed.
