Explant Culture: What It Is and How It Is Used

Explant culture is a laboratory method where small fragments of tissue are removed from an organism and grown in an artificial environment, a state referred to as ex vivo. A key benefit is that it preserves the tissue’s three-dimensional structure and cell connections, providing a model that closely mimics the tissue’s natural state. This allows scientists to observe how tissues function, develop, and respond to stimuli in a controlled setting.

Initiating an Explant Culture

The process begins with procuring tissue from animal models, plants, or human samples obtained with ethical approval. The tissue is transported to a sterile environment, like a laminar flow hood, to prevent contamination from microorganisms. Here, it is dissected into smaller fragments, often around 1×1 millimeter, using surgical blades.

Following dissection, the tissue pieces are washed to remove any debris. Each explant is then placed into a culture dish containing a specialized growth medium, sometimes on a supportive substrate to encourage growth. Finally, the dishes are placed in an incubator that maintains a constant temperature, humidity, and gas composition, such as 37°C and 5% CO2 for mammalian tissues.

Sources of Explant Material

Many biological materials can be used to establish explant cultures. In plant biology, explants can be taken from nearly any part of the plant, including segments of leaves, stems, roots, or floral parts. This is possible due to the ability of many plant cells to regenerate into a whole organism, a concept known as totipotency.

For animal studies, researchers use tissues from many different organs. Common sources include embryonic tissues for studying development, as well as fragments from the skin, liver, lungs, or brain. Tumor tissues are frequently cultured as explants to study cancer progression, and human tissues, such as a piece of gingiva from a tooth extraction, are also used under strict ethical guidelines.

Applications in Biological Discovery

Explant cultures provide insight into complex biological processes that are difficult to observe within a living organism. One application is in developmental biology, where researchers can watch organogenesis—the formation of organs—unfold in a dish. For example, embryonic mouse lung or kidney explants are used to track how these organs develop their intricate structures, known as morphogenesis.

The technique is also used for disease modeling. By culturing tumor biopsies, researchers can observe how cancer cells behave and interact with their surrounding tissue, providing insights into tumor invasion and metastasis. Explants of lung or intestinal tissue can be infected with viruses or bacteria to study the mechanisms of infection and the tissue’s immune response in a contained system.

Explant cultures are also used for toxicology and drug discovery. Scientists can apply new drugs or potential toxins directly to the cultured tissue to assess their effects on cell viability, function, and structure. For instance, a drug candidate for liver disease could be tested on a liver explant to see if it reduces tissue damage. This provides more biologically relevant data than testing on isolated cells, helping to predict how a whole organ might respond.

Sustaining Explant Cultures

Maintaining the health of explant cultures requires managing their laboratory environment. A primary component is the culture medium, a liquid nutrient broth specifically formulated for the tissue type. This medium contains salts, sugars, amino acids, and vitamins, and is often supplemented with growth factors and hormones.

The incubator’s environment must be consistently maintained. For some advanced applications, specialized bioreactors or perfusion systems are used. These devices create a more dynamic environment by continuously flowing fresh medium over the tissue, which improves nutrient delivery and waste removal.

To ensure the explant remains a valid experimental model, its structure and viability are preserved with supportive materials or scaffolds. Regular monitoring with microscopy is performed to check for healthy cell morphology and detect any microbial contamination, which would compromise the experiment. This careful management allows the tissue to remain functional for days or even weeks.