Sequential morphological characteristics of murine fetal liver hematopoietic microenvironment in Swiss Webster mice |
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Authors: | Jackline de Paula Ayres-Silva Pedro Paulo de Abreu Manso Mariana Rietmann da Cunha Madeira Marcelo Pelajo-Machado Henrique Leonel Lenzi |
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Institution: | 1.Laboratory of Pathology,Instituto Oswaldo Cruz/Fiocruz,Rio de Janeiro,Brazil;2.Morphology Sciences Program, Biomedical Sciences Institute,Universidade Federal do Rio de Janeiro,Rio de Janeiro,Brazil |
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Abstract: | Embryonic hematopoiesis occurs via dynamic development with cells migrating into various organs. Fetal liver is the main hematopoietic
organ responsible for hematopoietic cell expansion during embryologic development. We describe the morphological sequential
characteristics of murine fetal liver niches that favor the settlement and migration of hematopoietic cells from 12 days post-coitum
(dpc) to 0 day post-partum. Liver sections were stained with hematoxylin and eosin, Lennert’s Giemsa, Sirius Red pH 10.2,
Gomori’s Reticulin, and Periodic Acid Schiff/Alcian Blue pH 1.0 and pH 2.5 and were analyzed by bright-field microscopy. Indirect
imunohistochemistry for fibronectin, matrix metalloproteinase-1 (MMP-1), and MMP-9 and histochemistry for naphthol AS-D chloroacetate
esterase (NCAE) were analyzed by confocal microscopy. The results showed that fibronectin was related to the promotion of
hepatocyte and trabecular differentiation; reticular fibers did not appear to participate in fetal hematopoiesis but contributed
to the physical support of the liver after 18 dpc. During the immature phase, hepatocytes acted as the fundamental stroma
for the erythroid lineage. The appearance of myeloid cells in the liver was related to perivascular and subcapsular collagen,
and NCAE preceded MMP-1 expression in neutrophils, an occurrence that appeared to contribute to their liver evasion. Thus,
the murine fetal liver during ontogenesis shows two different phases: one immature and mainly endodermic (<14 dpc) and the
other more developed (endodermic-mesenchymal; >15 dpc) with the maturation of hepatocytes, a better definition of trabecular
pattern, and an increase in the connective tissue in the capsule, portal spaces, and liver parenchyma. The decrease of hepatic
hematopoiesis (migration) coincides with hepatic maturation. |
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