Análise morfológica e morfométrica do fígado, baço, e rim de camundongos Balb/c experimentalmente infectados com Leishmania infantum

Abstract

Leishmaniasis are infectious diseases that produces different kinds of lesions depending on the Leishmania species involved. It is known that the species responsible for causing visceral leishmaniasis is the Leishmania infantum, which infection target organs such as theliver, spleen and kidney.The experimental model considered susceptible to this infection is the Balb/c mouse, which lesions are similar to humans when infected by the referred species. Our objective was to analyze the morphological and morphometric characteristics of the liver, spleen and kidney on Balb/c mice infected for 15, 30, 45 and 60 days, experimentally infected with Leishmania infantum. Twenty-five mice were divided in five groups based on the infection time (L15 - 15 days of infection, L30 - 30 days of infection, L45 - 45 days of infection, L60 - 60 days of infection and the control group). After the euthanasia on the determined infection period, the following organs were collected: spleen, liver and kidney for infectivity evaluation by PCR (Polymerase Chain Reaction) and histopathological and morphometric analysis.Tissue fragments were processed and the microscope slides were stained with Hematoxylin and Eosin. The morphometry was performed on the software ImageJ; for the kidney, point counting was used to identify mesangial matrix and the glomerulus areas; for the liver, point counting was used to identify hepatocytes degeneration and inflammatory infiltrate areas and, for the spleen, the area of the structures. The PCR test demonstrated that all animals were infected by the parasite. The livers from the groups L15, L30 and L45 presented a pale-red coloration, while the group L60 presented a dark-red coloration, similar to the control group. The kidney did not present macroscopic differences, while a considerable growthwas detected on the spleen of the infected animals.In the quantification of the mesangial matrix in the glomerulus area, there was a significant difference between the groups L60 and L15, L30 and the control group and also between L45 and L15 (H=63,819;p<0,001).In the quantification of the glomerulus tuft area, there was a significant difference between L60 and L15; L30 and the control group (H=45,664; p<0,001). In the liver hydropic degeneration area quantification, there was a significant difference between all infected groups and the control group (H=44,506; p<0,001). The analysis on the inflammation area present on the hepatic tissue, there was a significant difference between the groups L15 and L30 when compared to the control group and between L15 when compared to L30, L45 and L60 (H=88,699; p<0,001). The quantification on the white pulp area showed a significant difference between the groups L15 and L60 (H=11,121; p< 0,05).Despite no substantial difference, the red pulp of the infected animals increased in size during the course of the infection. However, lesions persisted during the entire infection course studied such as the hydropic degeneration and the inflammatory infiltration present on the liver, the splenomegaly and the mesangial matrix growth on the renal glomerulus, which presented progression with the increase of infection period.