Histomorphometric analysis of the extracellular matrix of popliteal lymph nodes from dogs naturally infected by Leishmania (L.) chagasi

Kondo K.R.J., Fonseca C.C., Da Matta S.L.P. & Viloria M.I.V. 2009. [Histomorphometric analysis of the extracellular matrix of popliteal lymph nodes from dogs naturally infected by Leishmania (L.) chagasi.] Analise histomorfometrica da matriz extracelular do linfonodo popliteo de caes naturalmente infectados por Leishmania (L.) chagasi. Pesquisa Veterinaria Brasileira 29(8):610-616. Departmento de Veterinaria, Universidade Federal de Vicosa, Av. Peter Henry Rolfs s/n, Campus Universitario, Vicosa, MG 36570-000, Brazil. E-mail: krisregia@hotmail.com In the Americas, canine visceral leishmaniasis is caused by Leishmania (Leishmania) chagasi, an obligatory intracellular parasite of the phagocytic-monocytic system; the main histological changes associated with this disease occur in the lymphoid organs. Although dogs are considered to be the main carriers and disseminators of leishmaniasis in urban areas, there are few studies on the histopathologic and histomorphometric aspects in dogs naturally infected by L.chagasi analyzing the interaction between parasite and extracellular matrix. The current study characterize and quantify changes in the cellular and extracellular matrix (collagens type I and III) components of the popliteal lymph node from of 22 dogs with the natural infection by L. chagasi confirmed by indirect immunofluorescence assay (IFA) and compare theses findings with those fund in the popliteal lymph node from 10 non-infected dogs, that reacted negative in the IFA, and were clinically healthy. Lymph node fragments were longitudinally sliced and sections were processed for routine histopathology and stained by hematoxylin and eosin. For histomorphometry, additional sections from the same lymph node were fixed in glycol methacrylate and stained with toluidine blue. Lymph nodes from affected dogs were systemically enlarged, had increased numbers of lymphoid follicles, capsule hyperplasia and hypertrophy, and significant hyperplasia of lymphoid cells. In the lymph nodes from infected dogs, quantitative analyses of collagen fibers revealed predominance of type I collagen over type III fibers. These results demonstrate that dogs infected by L.chagasi experience degradation of the extracellular matrix components and consequently destruction of the lymphoid framework, thus altering nodal morphology.