{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T14:28:42Z","timestamp":1772807322657,"version":"3.50.1"},"reference-count":25,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T00:00:00Z","timestamp":1772755200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000002","name":"Office of the Director, National Institutes of Health","doi-asserted-by":"publisher","award":["P40 OD011062-22S1 (ECB)"],"award-info":[{"award-number":["P40 OD011062-22S1 (ECB)"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Biology"],"abstract":"<jats:p>Optimizing cryo-resuscitation from frozen sperm would improve access to cryopreserved rat models. In this study, the possibility of replacing intracytoplasmic sperm injection (ICSI) with in vitro fertilization (IVF) for model cryo-resuscitation from frozen\u2013thawed sperm was investigated. Rat IVF protocol was modified to allow the procedures to be performed during a 9 h workday. The possibility of genetic background-specific modification of the superovulation protocol for the improvement in IVF outcomes was explored. Wild-type and genetically modified Sprague Dawley (SD), Long Evans (LE) and Fischer 344 (F344) rats were used. Sperm freezing and IVF were conducted as previously described. Cleavage, blastocyst formation and hatching of the resulting embryos were used to assess their developmental potential in vitro. The results showed that, with limited repetitions, current sperm freezing and IVF protocols resulted in cleavage rates ranging from 58 \u00b1 11% to 87 \u00b1 7% and blastocyst rates ranging from 21 \u00b1 25% to 54 \u00b1 23%, which are acceptable for the cryo-resuscitation of rat models. With slight modifications, the procedure can be fit into a 9 h workday (SD: 48 \u00b1 35%; F344: 36 \u00b1 13%). Strain\/stock-specific differences in oocyte maturation timing were observed: LE females had a two-hour delay compared to SD and F344 rats in response to the same superovulation protocol. However, modifying the protocol for LE rats did not significantly improve IVF outcomes (34 \u00b1 6 vs. 32 \u00b1 12%). Overall, while IVF with frozen\u2013thawed sperm is a promising alternative to ICSI, significant variability remains across strains\/stocks and protocols. Continued research is necessary to advance our understanding of factors affecting the efficiency and repeatability of rat sperm freezing and IVF.<\/jats:p>","DOI":"10.3390\/biology15050433","type":"journal-article","created":{"date-parts":[[2026,3,6]],"date-time":"2026-03-06T09:22:14Z","timestamp":1772788934000},"page":"433","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Optimizing Rat In Vitro Fertilization for Rat Model Cryo-Resuscitation from Frozen\u2013Thawed Sperm"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8101-4644","authenticated-orcid":false,"given":"Hongsheng","family":"Men","sequence":"first","affiliation":[{"name":"Rat Resource and Research Center, Columbia, MO 65201, USA"},{"name":"Department of Pathobiology and Integrative Biomedical Sciences, University of Missouri, 4011 Discovery Drive, Columbia, MO 65201, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-4232-5122","authenticated-orcid":false,"given":"Payton S.","family":"Oswalt","sequence":"additional","affiliation":[{"name":"Rat Resource and Research Center, Columbia, MO 65201, USA"},{"name":"Department of Pathobiology and Integrative Biomedical Sciences, University of Missouri, 4011 Discovery Drive, Columbia, MO 65201, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9936-3607","authenticated-orcid":false,"given":"Elizabeth C.","family":"Bryda","sequence":"additional","affiliation":[{"name":"Rat Resource and Research Center, Columbia, MO 65201, USA"},{"name":"Department of Pathobiology and Integrative Biomedical Sciences, University of Missouri, 4011 Discovery Drive, Columbia, MO 65201, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1038\/nrg702","article-title":"Rat genetics: Attaching physiology and pharmacology to the genome","volume":"3","author":"Jacob","year":"2002","journal-title":"Nat. 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