Placentation in the alpaca Lama pacos

Abstract

Reproduction in South American camelids is poorly studied. To extend our knowledge of the development and cellular physiology of the placenta in the alpaca Lama pacos, we have examined specimens from day 150 of pregnancy to term. Morphological investigations using light, transmission and scanning electron microscopy, the histochemical localization of iron, alkaline and acid phosphatase activity, and the immunodetection of placental lactogen hormone were performed. Throughout pregnancy there was a progressive increase in the depths of folds on the uterine mucosa surface together with a thickening of the endometrium. Glandular cells exhibited PAS and acid phosphatase (AcP) positive secretion granules. In the chorion, giant trophoblast polyploid cells gradually became more numerous and larger. Non-giant cells exhibited positive granules for PAS, alkaline phosphatase (AkP) reaction and immunostaining for bovine placental lactogen hormone (PLH). SDS -PAGE electrophoresis and Western blotting procedures also confirmed the presence of a bovine PLH-like glycoprotein in the fetal alpaca placenta. Over the glandular openings, the chorion formed typical areolae, where the trophoblast exhibited AcP and PAS positive reactions. At these sites, the fetal endothelial cells contained iron-storage granules in their cytoplasm. The trophoblast-epithelial interface exhibited a complex microvillous interdigitation, in which an AkP reaction was very prominent. The chorionic capillaries progressively indented adjacent trophoblast cells. These data suggest that although the epitheliochorial alpaca placenta is diffuse, various trophoblast cell types and specialized areas of the maternofetal interface give the placenta micro-regional functions where histiotrophic nutrition, hormone production and molecular exchange are prevalent.

The materno-fetal interface in llama (Lama guanicoe glama)

“…Generally speaking, the morphological and histochemical characteristics of the areolae in our study were very similar to those described in peccaries (Santos 2006), sows (Dantzer 1984) and alpacas (Olivera 2002, Olivera et al 2003a. The classification of regular and irregular areolae as observed in sows was not found in the llama (Abd-Elnaeim et al 2003).…”

“…Both uni-and binucleated cells of the trophoblastic layer exhibited PAS-positive reactivity similar to that observed in dromedaries and alpacas (Jones et al 2000, Olivera et al 2003a. Acid phosphatase enzyme reactivity was observed in some trophoblastic cells localized, mainly localized at the top of the chorionic projections, differing from that found in the alpacas where this reactivity was only noted in the trophoblastic cells related to the areolae (Olivera et al 2003a). The PAS and acid phosphatase reactions showed that the trophoblastic cells actively participate in the uptake of products coming from the maternal surface, as well as in their metabolism and catalysis.…”

“…The morphological variability of the trophoblastic cells has also been described in other species of camelids, such as in dromedaries (Gorokhovskii et al 1975, Abd-Elnaeim et al 1999, Jones et al 2000, Wooding et al 2003 and in alpacas (Bustinza 1961, Jones et al 2000. Both uni-and binucleated cells of the trophoblastic layer exhibited PAS-positive reactivity similar to that observed in dromedaries and alpacas (Jones et al 2000, Olivera et al 2003a. Acid phosphatase enzyme reactivity was observed in some trophoblastic cells localized, mainly localized at the top of the chorionic projections, differing from that found in the alpacas where this reactivity was only noted in the trophoblastic cells related to the areolae (Olivera et al 2003a).…”

“…Giant trophoblastic cells were less frequently observed than in other species of camelids, such as in alpacas, and even less than in those seen in dromedaries (Jones et al 2000, Olivera et al 2003a). Remains of intercellular membranes observed in the cytoplasm of some giant cells fit the proposition that the source of these cells in dromedaries results from the fusion of contiguous mononucleated cells (Skidmore et al 1996).…”

“…This type of placenta is also similar in mares and sows, although the fetal membranes of the camelids have particular characteristics (Stevens et al 1980, Zhang et al 1991, Fowler & Bravo 1998. As stated by some authors (Abd-Elnaeim et al 1999, Jones et al 2002, Olivera 2002, Olivera et al 2003a, Wooding et al 2003 very large cells which contain large nuclei and numerous nucleoli in the trophoblastic layer of alpacas, Bactrian camels and dromedaries have been found.…”