BrdU

BrdU, or bromodeoxyuridine, is the chemical compound 5-bromo-2'-deoxyuridine, a synthetic nucleoside analog of thymidine. As a thymidine analog, BrdU can be incorporated into the DNA of dividing cells during DNA replication in S phase, substituting for thymidine. This property makes BrdU a widely used marker of cell proliferation in both in vitro and in vivo experiments.

Detection of BrdU relies on specific antibodies that recognize the incorporated analog. After DNA is denatured to expose BrdU epitopes, anti-BrdU antibodies are applied and the label is visualized by immunocytochemistry, immunohistochemistry, or flow cytometry. Denaturation methods include acid treatment, heat, or enzymatic approaches, selected to preserve tissue integrity as much as possible.

Applications include measuring cell proliferation in cultured cells, tissue sections, and developing or regenerating tissues. BrdU labeling is common in cancer research, neuroscience to study neurogenesis, developmental biology, and tissue repair. When used with additional markers, BrdU can help identify the cell cycle phase and track the fate of proliferating cells. Sequential labeling with different thymidine analogs (for example IdU or CldU) allows retrospective analysis of cell division over time; EdU provides an alternative detection method that avoids some denaturation steps but uses a different chemistry.

Limitations and considerations: BrdU labeling requires DNA denaturation, which can compromise epitopes and tissue structure. High BrdU doses or prolonged exposure may affect cell physiology and DNA replication fidelity. The assay's sensitivity and specificity depend on antibodies and detection methods, and BrdU can cross-react with other halogenated nucleosides under some conditions. BrdU is used in research settings and is not a routine diagnostic agent in clinical practice.