Myofibrillar breakdown and cytoskeletal alterations in heart muscle cells during invasion by Trypanosoma cruzi: immunological and ultrastructural study.

The cytoskeletal organization of normal and Trypanosoma cruzi-infected mouse embryo heart muscle cells (HMC) in primary culture was investigated using immunofluorescence and transmission electron microscopy. Fluorescent probes revealed that in the early stages of infection, up to 24 h, the HMC cytoskeleton appeared to accommodate the intracellular parasites perinuclearly, with only a few cells displaying a slight disturbance in the distribution of filaments. However, as the infection progressed (48 to 72 h), microtubules and desmin filaments were disrupted. Breakdown of myofibrils occurred in regions where the parasites were present, followed by formation of actin polygons. Using Triton X-100 treated whole cell mount, we obtained a striking preservation of the three-dimensional architecture of the cytoskeleton. Combining electron spectroscopic imaging (ESI) with contrast tuning, we detected a highly interconnected cytoskeletal network in normal cells, and a loose network in infected cells. Bundles of filaments running under and over the parasites were also observed. Our results demonstrate that T. cruzi infection induces myofibrillar breakdown and destruction of several cytoskeleton filaments in heart muscle cells.