Autoschizis of human ovarian carcinoma cells: Scanning electron and light microscopy of a new cell death induced by sodium ascorbate: Menadione treatment

Abstract

Human ovarian carcinoma (MDAH 2774) cells were treated with sodium ascorbate (VC), menadione (VK3), or a combination of both in a ratio 100: 1 for 1 h and then examined with scanning electron microscopy (SEM) and light microscopy (LM). Light microscopy data corroborated SEM observations, which demonstrated that death of VC + VK3-treated tumor cells occurred primarily by autoschizis. This type of cell death is characterized by a decrease in cell size, cytoplasmic self-excisions, and nuclear and nucleolar morphologic degradations without the formation of apoptotic bodies. Ultimately, cell death results from karyorrhexis and karyolysis. This study illustrates that plasma membrane damage (branching filopodia, blisters, blebs) results from VC treatment; cytoskeletal damage and self-morsellation are caused by VC, VK3, and VC+VK3 treatments. The VC treatment results in a 23% decrease in cell diameter while VK3-treated cells decrease cell diameter by 66%. After 1 h of VC+VK3 treatment, a heterogenous cell population is found. This population can be resolved into one population whose diameters are 23% smaller than those of sham-treated cells, and a second population whose diameters are approximately twice those of sham-treated cells. This second population is indicative of doublet formation in which the cells appear to be dividing (an early stage of autoschizic cell death). One half of the doublet contains the cell nucleus while the other half consists of cytoplasm and membrane only. The enucleate portion of this doublet will then be excised. When the types of cell death are enumerated following VC+VK3 treatment, 43% of the cells die by autoschizis, 3% by apoptosis, and 1.9% by oncosis. These results confirm that autoschizis is the principal form of cell death that results from the in vitro treatment of human ovarian carcinoma cells with the vitamin combination.