Imaging Cell Competition in Ex-Vivo Drosophila Adult Brains

Live imaging has been instrumental in understanding cellular dynamics in <i>Drosophila</i> tissues, but technical limitations have prevented the long-term visualization of cell competition in adult brains. Here, we describe a simple ex vivo protocol that enables extended live imaging of adult <i>Drosophila</i> brains for up to 32 h. The method relies on non-supplemented Schneider's <i>Drosophila</i> medium and hydrophobic interactions to maintain brain stability during imaging, eliminating the need for complex culture conditions or embedding procedures. We validate this approach by studying cell competition in the optic lobes following traumatic brain injury, where cell competition is expected to occur with a peak at 48 h after damage. We demonstrate the value of this method by visualizing the expression of the fitness checkpoint Azot in a loser cell and its subsequent elimination. This protocol offers a versatile platform for studying cell competition and other cellular processes requiring extended observation of the adult <i>Drosophila</i> brain.