Preparation of Mice for Long-Term Intravital Imaging of the Mammary Gland: FIGURE 1.

INTRODUCTION Genetic studies and tumor biopsies have shown the importance of stromal components for cancer progression, but much remains to be learned about the dynamic interactions among the distinct tumor components within live animals. One challenge of studying cell behavior in progressively developing tumors has been the difficulty of maintaining live mice on the microscope stage. To prepare mice for long-term intravital imaging, auxiliary equipment is necessary to enable and to control anesthesia (such as the anesthesia gas mixer itself, a gas humidifier, indwelling lines for saline, and heat blanket). The other important component is to gain optical access to the mammary gland. This protocol describes a surgical technique that creates a skin flap with the mammary gland. The method is relatively easily taught, does not compromise the peritoneal cavity or any major blood vessels, and is generally well tolerated by the mice. There is minimal inflammatory response to the surgery itself if the solutions and tools are sterile, the surgical work area is clean, and aseptic techniques are used. This protocol works well for a single long-term image session, but does not enable repeated imaging sessions. For such approaches, methods for implanting imaging windows over the inguinal mammary gland should be used instead.