A paucity of structural integrity in cloned porcine blastocysts produced in vitro.
The structural integrity of blastocyst stage embryos, consisting of the inner cell mass (ICM) and trophectoderm (TE) cells, is a prerequisite for normal development after implantation in mammals. In this study, allocation of nuclear transfer (NT)-derived porcine blastocysts to the ICM and to the TE cells was examined and compared with IVF- and in vivo-derived embryos. NT-derived embryos had a lower developmental competence to the blastocyst stage than IVF-derived embryos (P < 0.05). Total cell number of NT-derived blastocysts was inferior to that of IVF-derived embryos (P < 0.05), although no difference was detected between the two groups in the ratio of ICM to total cells. However, in vivo-derived blastocysts had a higher proportion of ICM to total cells compared with in vitro-produced embryos (P < 0.01). To investigate what proportions of in vitro-produced porcine embryos represent normal structural integrity, differentially-stained blastocysts were individually classified into three presumptive groups (I: <20%; II: 20-40%; III: >40%) according to the ratio of ICM to total cells. Low proportions of NT- (12.5%, 7/56) and IVF-derived blastocysts (15.8%, 9/57) were assigned to Group II, presumptively having a normal range of structural integrity, whereas, almost all in vivo-derived embryos (97.5%, 39/40) were allocated to Group II. In conclusion, limited structural integrity may lead to the poor survival to term of NT- or IVF-derived porcine embryos produced in vitro.
Koo
Deog-Bon
DB
Laboratory of Development and Differentiation, Korea Research Institute of Bioscience and Biotechnology, 52 Eoeun-dong, Yuseong, Daejeon 305-806, Republic of Korea.
Kang
Yong-Kook
YK
Park
Jung Sun
JS
Park
Jin-Ki
JK
Chang
Won-Kyong
WK
Lee
Kyung-Kwang
KK
Han
Yong-Mahn
YM
D000818:Animals; D001755:Blastocyst / Q000166:cytology* / Q000502:physiology*; D002452:Cell Count; D019976:Cloning, Organism; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D008297:Male; D053652:Nuclear Transfer Techniques; D013552:Swine