TEM studies on morphological “junctions” between Trichinella spiralis larvae and mouse skeletal muscle cells with particular emphasis on the early changes in host muscles

Larvae of the parasitic nematode Trichinella spiralis migrate via the bloodstream or the lymphatic system to the skeletal muscle cells where they induce multiple alterations in the intracellular environment leading to the formation of nurse cells. The “nurse cell-T. spiralis larva” complex is composed of a transformed fragment of a skeletal muscle cell and the wall of the larva. The pathological process responsible for the formation of this complex, known as basophilic transformation, is essential for the development of T. spiralis larvae, but it still not known how newborn larvae penetrate the transformed fragment of the muscle cell. In this study, we aimed to characterize the ultrastructure of the region of the nurse cell in direct contact with the larval wall, after one and two weeks of T. spiralis infection in mice. For this purpose, a transmission electron microscope fitted with a goniometer was used to make observations of samples tilted at an angle of ±40° relative to the axis of the electron beam. Examination of electron micrographs revealed the continuity of the nurse cell membrane adjacent to the larval surface and the presence of a large quantity of glycogen particles close to the inner surface of this membrane. Our results showed that death of the T. spiralis larvae was associated with destruction of the contact region between the larval wall and the adjacent surface of the nurse cell. We conclude that the T. spiralis larva does not penetrate the nurse cell, but a morphological “junction” is formed between the larval wall and the cell membrane.