Sheep and goat pregnancies were established by embryo transfer in three multiparous, interspecies chimeras (two sheep-goat chimeras and one sheep/goat hybrid-sheep chimera). At day 39 of gestation, placentomes were collected for immunohistochemical evaluation using anti-sheep and anti-goat antibodies. The degree of trophoblastic attachment to the maternal endometrium was determined for concepti of the two species, with special attention to areas in which the conceptus trophoblast was the same versus different species as the maternal caruncular epithelium. Goat concepti were dead and sheep concepti alive at sample collection. The goat concepti had fewer (P < 0.01) and smaller (P < 0.01) placentomes than the sheep concepti and the goat trophoblast was less adhered to the maternal epithelium than was the sheep trophoblast. Of particular interest were areas at the conceptus/caruncular interface in the sheep/goat hybrid-sheep chimera. The goat conceptus trophoblast had adhered to the hybrid but not to the sheep caruncular epithelium. The sheep conceptus trophoblast had adhered to areas of the sheep but not to the hybrid maternal epithelium. These results suggest that faulty attachment between trophoblast and maternal epithelium is a major factor in sheep-goat interspecies pregnancy failure. Since sheep-goat chimeras are tolerant to monomorphic sheep and goat species-specific antigens, the results are likely due to inappropriate signalling at the conceptus/maternal interface and not due to classical immune rejection. Selection of embryo/recipient combinations for successful interspecies pregnancies in ruminants, and development of strategies to overcome barriers to interspecies pregnancies that currently exist, might be aimed more productively at concerns for adequate placental formation than at concerns over maternal immunological rejection of the conceptus.
|Original language||English (US)|
|Number of pages||8|
|Journal||Small Ruminant Research|
|State||Published - Mar 1997|
ASJC Scopus subject areas
- Animal Science and Zoology