PARENT SESSION
Pregnancy and Parturition

MORPHOLOGICAL DIFFERENCE OF PLACENTOME FORMATION BY SOMATIC CELL NUCLEAR TRANSFERRED EMBRYO .

Yamada, Osamu^1,4, Kohsaka, Tetueya³, Shimizu, Manabu ², Akagi, Satoshi¹, Takahashi, Seiya ¹, Geshi, Masaya ¹, Imai, Kei¹, Takahashi, Toru ¹, Takezawa, Toshiaki ¹, Hashizume, Kazuyoshi ¹, ^{1 4 3 2}

ABSTRACT- The technique of somatic cells nuclear transfer (SNT) is gaining popularity in many of the domesticated species. However, the rate of embryonic and/or fetal loss remains relatively high with this technique. It has been assumed that the latter may be due either asynchrony of implantation or placental malformation. Therefore, we compared the placental formation and development between pregnancies derived by artificial inseminated (AI) and SNT. Embryos were cloned from dermal fibroblast and granulosa cells, and transferred to the recipient cows on day 7 of estrous cycle (day 0= day of estrus). Artificially inseminated cows served as controls. Both the SNT recipients and AI cows were slaughtered between Days 30 and 100 of gestation and placental tissue collected for gross and microscopical examinations. A significant less number of placentomes were found in SNT cows when compared to AI cows on day 60 of gestation (P<0.05, 23±11.1(SEM) vs 80±5.4(SEM)), but no difference was noted on Day 100 (78±15.1 (SEM) vs 93±7.3(SEM)). The size of the placentomes in SNT recipients was relatively larger on Days 60 and 100. There was no evidence of caruncular hypertrophy at day 60 in SNT cows as observed in AI cows. Interestingly, the caruncular surface in SNT cows at this stage was comparable to that of estrous cycle. The uterus obtained from cloned animals on day 60 of pregnancy contained greater extent of loose connective tissue matrix, and underdeveloped endometrial glands when compared to AI cows. The most striking feature was the incomplete formation of chorionic villi in the placenta of SNT cows. In addition, a higher rate of fetal death was recorded in SNT fetuses (1/5, 4/7, 0/3 at Day 30, 60 and 100, respectively) than those obtained from AI (1/7, 0/9, 0/4 at Day 30, 60 and 100, respectively). These results suggest that early fetal loss in SNT recipients, especially during first half of gestation, may be caused by placental malfunction. This study was supported in part by Grants-in-aid from ORCS, BRAIN and MAFF, Japan.

KEY WORDS: somatic cells nuclear transfer , placentome , morphological examination, cow