Metamorfose morfológica e imune no desenvolvimento hepático neonatal

Abstract

The liver is a vital organ performs numerous essential functions. Among them, there are metabolic, catabolic, excretory, secretory, synthesis and storage and immune defense functions. The processes of organogenesis and embryonic development of the liver have been studied by many researchers. However, the complexities of neonatal liver development are still neglected. Thus, the aim of this work was to study the postnatal development of the organ, focusing on the morphology and populations of immune cells. We found changes in the architecture of the parenchyma, related to cell density, organization and composition. While the adult liver is completely organized in strings of hepatocytes interspersed by sinusoids with immune cells inside the vessels, neonates have a liver architecture without a clear pattern of organization, with islands of immune cells in the hepatic parenchyma and bee-shaped vessels. In the characterization of immune cell populations, the adult liver is especially a lymphoid organ, and neonatal liver is mostly composed of myeloid cells. We also observed a chronological sequence between cell populations suggesting that precursor cells with monocytic characteristics give rise to resident mature cells that are relocated in the different hepatic compartments. Finally, functional studies revealed an inefficiency in neonates related to their function of hepatic clearance and to the production of transaminases. Human histological samples confirm retention of immune cells in the hepatic parenchyma of neonates, forming islands of cells very similar to the mice. Therefore, our data demonstrated that there is a huge difference, morphologically, immunologically and functionally, in the liver of the neonate compared to the adult liver.