Populações celulares em granulomas esquistossomáticos: biologia celular em uma perscpectiva ecológica

Abstract

Schistosomiasis mansoni is a parasitic disease caused by hematophagous worms of the genus Schistosoma. It is a serious public health problem. Currently, more than 240 million people worldwide are affected by this parasite and it is estimated that more than 700 million people are at risk of infection in 78 countries and territories of tropical and subtropical regions of Africa, Asia, Caribbean and South America. Schistosomiasis has a striking histopathological characteristic: the granuloma formation in target organs of vertebrate hosts. Granulomas form around each egg of the parasite, which reach metabolically active host tissues. The substances released by parasite eggs lead to the recruitment of numerous cells, which together with the target organ cells and the collagen-rich extracellular matrix, build the dynamic structure of the granulomas. Such structures have been extensively studied from the standpoint of immunology, parasitology and cell biology, but little is known from the point of view of cellular ecology. Here, we defined murine hepatic schistosomiasis granuloma as an ecological system, from the point of view of cellular ecology. In parallel, we investigated the composition and distribution of inflammatory cell populations in hepatic granuloma during the evolutionary stages of the experimental schistosomiasis mansoni. In this perspective, we proposed that granulomas works as a true ecological system and all cellular populations found there constitute a true cellular community. Moreover, we suggested that granuloma formation occurs as an ecological succession compared to larger scale environments. We identified and quantified all the cellular populations found there, using a whole slide imaging technique, which enabled visualization of entire sections of the liver. Applying classic strategies of diversity investigations in the granuloma, we detected that during the process of evolution, the richness (number of populations) remains the same in all granuloma formation process. On the other hand, the abundance frequencies values fluctuate, that is, all the cells identified are present at all stages of granuloma evolution, but the quantity varies throughout the process. Thus, it is important to investigate the factors that regulate the abundances of the cellular populations during the construction of granulomas. Describing the cell-cell interactions that exist in the granuloma, in a broad context, may be the key to understanding the complexity of this response and pointing to new therapeutic targets.