Spore-like cells

Spore-like cells are cells that exhibit behavior characteristic of spores. Known spore-like cells are a specific class of stem cells in adult organisms, including humans, which are very small, very versatile, and most frequently remain in a dormant "spore-like" state as the rest of the cells of the organism divide, grow, and die. Despite their dormancy, they retain the ability to grow, divide, and differentiate into other cell types expressing characteristics appropriate to the tissue environment from which they were initially isolated, if some external stimulus should prompt them to do so. This capacity to continue to regenerate new cells has been shown in in-vitro conditions for some animals in which all other cells have died, especially if the animal died from exposure to cold elements.

Study
Spore-like cells were described first by Vacanti et al. in 2001 (Vacanti, M. P., A. Roy, J. Cortiella, L. Bonassar, and C. A. Vacanti. 2001. Identification and initial characterization of spore-like cells in adult mammals. J Cell Biochem 80:455-60.) They are extremely small (less than 5 micrometers). They appear to lie dormant and to be dispersed throughout the parenchyma of virtually every tissue in the body. Being dormant, they survive in extremely low oxygen environments and other hostile conditions, known to be detrimental to mammalian cells, including extremes of temperatures.

Spore-like cells remain viable in unprepared tissue (using no special preservation techniques), frozen at -86°C and then thawed, or heated to 85°C for more than 30 minutes. This has led researchers to try to revitalize spore-like cells from tissue samples of frozen carcasses deposited in permafrost for decades (frozen walrus meat more than 100 years old, and mammoth and bison in Alaska estimated to be 50,000 years old). Vacanti et al. believed that these unique cells lie dormant until activated by injury or disease, and that they have the potential to regenerate tissues lost to disease or damage. Because the cell-size of less than 5 micrometers seems rather small as to contain the entire human genome the authors speculate on the "concept of a minimal genome" for these cells.