Opaque Polyploid Cells in Ishikawa Endometrial Cultures Are Capable of Forming Megamitochondria, Organelles Derived from the Adaptation of Fused Mitochondria Whose Capacity to Develop Gaseous Vacuoles Suggests CO2 Retention and Hypoxic Metabolism

Opaque polyploid cells capable of forming megamitochondria are a constant feature in colonies of Ishikawa endometrial epithelia, accounting for approximately 5% - 10% of the cells. Opaque cells appear to communicate with other opaque cells via membrane extensions and with other cells in a colony by extra-cellular vesicles. Opaque cells form first as rectangular structures, somewhat larger than surrounding monolayer cells. The cells eventually round up, remaining in the colony for 20 or more hours before detaching. The most unusual characteristic of Ishikawa opaque cells is their capacity to form mitonucleons, megamitochondria that surround aggregated chromatin. This paper reviews evidence that adaptations resulting in megamitochondria include a loss of the capacity for oxidative phosphorylation leaving the adapted megamitochondria reliant on metabolism such as reductive carboxylation.