Hepatic hematopoiesis in the alpaca (Vicugna pacos), a species with development in hypoxic environments

Hematopoiesis occurs in different anatomical niches throughout the life of the individual. The first hematopoietic extra-embryonic stage is replaced by a intra-embryonic stage that occurs in a region that is adjacent to the dorsal aorta. Then, the prenatal hematopoietic function is continued by the liver and spleen, and later by the bone marrow. The objective of the present work was to describe the morphological characteristics of hepatic hematopoiesis in the alpaca and to analyze the proportion of the hematopoietic compartment of the organ and the cell types, at different times of ontogeny. Sixty-two alpaca samples were collected from the municipal slaughterhouse of Huancavelica, Perú. They were processed by routine histological techniques. Hematoxylin-eosin staining, special dyes, immunohistochemical techniques and supplementary analyses by lectinhistochemistry, were performed. The prenatal liver is an important structure in the expansion and differentiation of hematopoietic stem cells. Their hematopoietic activity was characterized by four stages: initiation, expansion, peak, and involution. The liver started its hematopoietic function at 21 days EGA and it was maintained until shortly before birth. Differences were found in the proportion and morphology of the hematopoietic tissue in the different groups corresponding to each gestational stage.