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This Article Full Text Full Text (PDF) All Versions of this Article: 68/5/1821    most recent biolreprod.102.011726v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ogonuki, N. Articles by Ogura, A. Search for Related Content PubMed PubMed Citation Articles by Ogonuki, N. Articles by Ogura, A. Agricola Articles by Ogonuki, N. Articles by Ogura, A.

Fertilization of Oocytes and Birth of Normal Pups Following Intracytoplasmic Injection with Spermatids in Mastomys (Praomys coucha)¹

Bioresource Center,³ RIKEN, Tsukuba, Ibaraki 305-0074, Japan Department of Veterinary Science,⁴ National Institute of Infectious Diseases, Shinjuku, Tokyo 162-8640, Japan

The mastomys is a small laboratory rodent that is native to Africa. Although it has been used for research concerning reproductive biology, in vitro fertilization (IVF) and intracytoplasmic sperm injection are very difficult in mastomys because of technical problems, such as inadequate sperm capacitation and large sperm heads. The present study was undertaken to examine whether mastomys spermatids could be used to fertilize oocytes in vitro using a microinsemination technique, because spermatids are more easily injected than mature spermatozoa into oocytes. Most mastomys oocytes (80%–90%) survived intracytoplasmic injection with either round or elongated spermatids. Round spermatids had little oocyte-activating capacity, similar to those of mice and rats, and exogenous stimuli were needed for normal fertilization. Treatment with an electric pulse in the presence of 50 µM Ca²⁺ followed by culture in 10 mM SrCl₂ led to successful oocyte activation. After injection of round spermatids into preactivated oocytes, 93% of oocytes were normally fertilized (male and female pronuclei formed), and 100% of cultured oocytes developed to the 2-cell stage. However, none reached term after transfer into recipient females. Elongated spermatids, which correspond to steps 9–11 in rats, activated oocytes on injection without additional activation treatment. After embryo transfer, five offspring (6% per transfer) developed to term. These results indicate that microinsemination with spermatids is a feasible alternative in animal species that are refractory to IVF and sperm injection and that using later-stage spermatids may lead to increased production of viable embryos that can develop into normal offspring.

¹ Supported by grants from MEXT, Japan; MHLW, Japan; and the Japan Health Sciences Foundation, Japan.

² Correspondence: Atsuo Ogura, RIKEN Bioresource Center, 3-1-1, Koyadai, Tsukuba, Ibaraki 305-0074, Japan. FAX: 81 298 36 9172; ogura{at}rtc.riken.go.jp