Leishmaniosis—A report about the microvascular and cellular architecture of the infected spleen inCanis familiaris

Abstract

Leishmaniosis is an anthropozoonosis caused by an intracellular protozoan parasite that causes a wide spectrum of diseases in humans and dogs worldwide. In the Mediterranean basin, Portugal, Central and South America, and in the Middle East, visceral leishmaniosis is caused by Leishmania infantum. In these areas, dogs are believed to be the natural reservoirs of this parasite. In the case of visceral leishmaniosis, the spleen is one of the several hematopoietic and immunocompetent organs involved. Since this viscera is a blood filter, the authors investigated the expression of the morphological and microvascular environment and modifications of the spleen cell population related to immunological responses to this parasitic condition. The tools used to perform this study were scanning electronic microscopy of intact tissue and corrosion casts, transmission electronic microscopy, histology and immunohistochemistry. The results reveal three important modifications concerning the spleen's microvascular architecture when compared with its normal pattern, independently of the serological titer obtained with indirect immunofluorescence. (1) A marked scarcity of the sinusoidal system sheet that surrounds the central artery/arteriole of the white pulp; (2) A huge development of pulp venules and veins; (3) The presence of a surprising development of reticular fibers. The authors postulate that independent of the virulence of the parasite involved and the type of immunity prevalent in a particular host, the spleen develops blood dynamic conditions that permit reduction in the speed of blood flow so that cells involved in immunological processes can proliferate and differentiate, and also contributes to trapping lymphocytes within the area through the differentiation of characteristics that resemble those of HEV endothelial cells.

Inhibition of receptor tyrosine kinases restores immunocompetence and improves immune-dependent chemotherapy against experimental leishmaniasis in mice

“…First, in spite of clear anatomical differences in the microarchitecture of rodent and human spleen (33), H&E studies of human spleens taken from postmortem VL patients show white pulp atrophy, with loss of germinal centers, depletion of lymphocytes (presumptive T cells), follicular disruption, and extensive macrophage egress into the tissue (29,49), all histopathologic changes that were also observed in experimental VL (17,20) and in canine VL (50). Second, studies in canine VL have provided clear electron microscopical evidence for microvascular changes associated with progressive disease (34), data confirmed here by a variety of other approaches in experimental murine VL. Clearly, future immuno-histochemical analysis of the L. donovaniinfected human spleen could provide further evidence to support the use of RTKIs for the treatment of this disease in humans.…”

“…A role for vascular remodeling in the development of splenomegaly associated with leishmaniasis was first suggested by electron microscopical studies of splenic architecture in dogs with progressive canine VL (34). We therefore first analyzed whether vascular changes occurred during the progression of L. donovani infection in mice at 14-28 days postinfection (dpi), when severe splenomegaly and increased tissue parasite burden became most evident ( Figure 1, A and B).…”

Natural Substances as New Potential Strategies for the Treatment of Leishmaniosisin Dogs

“…Other symptoms are the marked enlargement of lymph nodes caused by the increased number and size of lymphoid follicles and the marked hypertrophy and hyperplasia of medullary macrophages in the cords and sinuses (Lima et al, 2004). The splenomegaly is associated with increased monocyte and macrophage cellularity and changes in the microvasculature structure with abundant pulp venules and veins and increased reticular fibers (Alexandre-Pires et al, 2006). Renal disease can be the result of tubulointerstitial nephritis, glomerulonephritis and amyloidosis with a progression from asymptomatic proteinuria to nephrotic syndrome or chronic renal disease with azotemia (Koutinas et al, 1999).…”

ALTERAÇÕES DA MATRIZ EXTRACELULAR ESPLÊNICA EM CÃES NATURALMENTE INFECTADOS COM Leishmania (Leishmania) infantum chagasi

“…A correlação foi significativa ao teste de correlação de Pearson (r=0,6531, p=0,00213) (Figura 06). Outra explicação para a intensa congestão e colapso estrutural do parênquima, que contribuiria para o aumento de peso e de tamanho esplênico, assim como a deposição de fibras reticulares na leishmaniose visceral canina demonstrado por Weiss et al (32) e Alexandre-Pires et al (33) , é que a presença de maior número de células reticulares que formam o leito de filtração sinusoidal seria responsável por vários mecanismos como controle da circulação do baço através da contração, alinhamento da expansão das células dendríticas e reticulares promovendo a síntese de colágeno do tipo III (fibras reticulares). Uma rede de fibras reticulares pôde ser observada nas condições de parasitismo esplênico na leishmaniose visceral.…”