Ex vivo

Ex vivo (Latin: "out of the living") means that which takes place outside an organism. In science, ex vivo refers to experimentation or measurements done in or on tissue in an artificial environment outside the organism with the minimum alteration of natural conditions. Ex vivo conditions allow experimentation under more controlled conditions than is possible in in vivo experiments (in the intact organism), at the expense of altering the "natural" environment.

A primary advantage of using ex vivo tissues is the ability to perform tests or measurements that would otherwise not be possible or ethical in living subjects. Tissues may be removed in many ways, including in part, as whole organs, or as larger organ systems.

Examples of ex vivo specimen use include:

• assays;
• measurements of physical, thermal, electrical, mechanical, optical and other tissue properties, especially in various environments that may not be life-sustaining (for example, at extreme pressures or temperatures);
• realistic models for surgical procedure development;
• investigations into the interaction of different energy types with tissues;
• or as phantoms in imaging technique development.

The term ex vivo is often differentiated from the term in vitro ("within the glass") in that the tissue or cells need not be in culture; these two terms are not synonymous.

In cell biology, ex vivo procedures often involve living cells or tissues taken from an organism and cultured in a laboratory apparatus, usually under sterile conditions with no alterations for up to 24 hours. Experiments lasting longer than this using living cells or tissue are typically considered to be in vitro. One widely performed ex vivo study is the chick chorioallantoic membrane (CAM) assay. In this assay, angiogenesis is promoted on the CAM membrane of a chicken embryo outside the organism (chicken).

See also

• Animal testing
• in situ
• in utero
• in vitro
• in vivo
• in silico