Ex vivo

Ex vivo brainstem: A. coronal view displaying the anterior portion of the tissue sample; B. sagittal view displaying the left-hand side of the tissue sample

Ex vivo (Latin for 'out of the living') refers to experiments or measurements performed on tissues or cells that have been removed from an organism and maintained under conditions that closely mimic their natural environment. While certain ex vivo techniques have been employed since the early 20th century, their formalization and refinement as a research methodology accelerated in the mid-20th century. These approaches enable the study of biological processes in a controlled setting while preserving the structural and functional integrity of tissues and organs. Ex vivo studies are widely applied in medical research, pharmacology, and biotechnology, serving as an intermediate method between in vitro (test tube) experiments and in vivo (whole-organism) studies. They provide a balance between experimental control and physiological relevance, allowing for investigations that may be ethically or technically impractical in living subjects.

Techniques

Ex vivo research employs specialized techniques to sustain tissues or cells outside their natural environment while preserving their functional integrity. One such approach is ex vivo organ perfusion, in which whole organs, such as the heart or lungs, are maintained in a functional state by circulating nutrient-rich solutions that mimic physiological blood flow. This method enables researchers to investigate organ-level responses to drugs, disease states, or environmental changes under controlled conditions. In contrast, traditional organ culture typically involves maintaining organ sections or small fragments in static or semi-static conditions without active perfusion.

Another widely used technique involves culturing tissue slices, where thin sections of organs, such as the brain or liver, are maintained on supportive matrices to preserve their three-dimensional structure and cellular interactions. This method allows for the study of localized responses, tissue-specific dynamics, and physiological processes over extended periods. Organotypic slice cultures, such as hippocampal slices, are used in neuroscience research for examining long-term cellular and synaptic activity.

A third ex vivo method, cell culture, involves isolating individual cells from tissues and growing them in a medium enriched with nutrients and growth factors. While these cultures retain some functional characteristics of their tissue of origin, they often exhibit changes in phenotype and gene expression when removed from their native environment. Primary cell cultures, derived directly from tissues, more closely resemble physiological conditions than immortalized cell lines, making them essential for studying cellular behavior, disease mechanisms, and drug effects. The choice of technique depends on the research objectives and the biological properties of the tissue or cells under study.

Demonstration of isolation of choroid from the mouse eye

In situ lung function evaluation, and assessment of total lung capacity (TLC) and basal elastance after performing a recruitment maneuver

See also

• Animal testing – Use of animals in experiments
• List of medical roots, suffixes and prefixes
• Neoclassical compound – Compound words composed from Latin or ancient Greek