Ultrastructural Features of Mast Cell Death in Autotransplanted Lymph Heart of Adult Frog Rana temporaria

Abstract

Abstract—Lymph heart of frog are hollow pulsating organs 1–2 mm in diameter that pump lymph into the venous system. They were used in this work as an experimental model to study the processes of initiation and development of aseptic inflammation in damaged tissues and necrosis-like death of mast cells (MCs). The ultrastructure of damaged and dying MCs was studied in striated muscle tissue of the posterior lymph heart of the adult frog in conditions of temporary ischemia (hypoxia) caused by autotransplantation of this organ into its own bed. It was found that damaged MCs die via oncotic necrosis after autotransplantation of the lymph heart within the period of time from 3 days to 6 weeks. Swelling of the cells and their membrane organelles (except for cytoplasmic secretory granules), dilatation of perinuclear space, budding of vesicles strewn with ribosomes from the outer nuclear membrane, and enrichment of nuclei of some MCs with heterochromatin occur at the early stages of oncosis. For late stages of oncotic necrosis, disintegration of the plasma membrane, release of intact and structurally little modified secretory granules into extracellular space, and karyolysis are typical. The presence of presumably nuclear material was found in extended perinuclear spaces of some damaged and dying MCs. The release of vesicles of rough endoplasmic reticulum (RER) into extracellular space was detected in places of local violation of the plasma membrane integrity of still undestroyed MCs. Immunocytochemical labeling of MCs using antibodies to histamine, substance P (SP), and atrial natriuretic peptide (ANP) (conducted at the ultrastructural level) detected the localization of aurum particles both over secretory granules located in the cytoplasm of damaged and dying cells and over the granules released into extracellular space after disintegration of MCs. Data obtained in the present study suggest that MCs dying via oncotic necrosis may be involved in the initiation and development of aseptic inflammatory process in autotransplanted lymph heart of frog and be a source of alarmins that contribute to the development of inflammation.