Dendra2 Photoswitching through the Mammary Imaging Window

In the last decade, intravital microscopy of breast tumors in mice and rats at single-cell resolution(1-4) has resulted in important insights into mechanisms of metastatic behavior such as migration, invasion and intravasation of tumor cells(5, 6), angiogenesis(3) and immune cells response(7-9). We have recently reported a technique to image orthotopic mammary carcinomas over multiple intravital imaging sessions in living mice(10). For this, we have developed a Mammary Imaging Window (MIW) and optimized imaging parameters for Dendra2(11) photoswitching and imaging in vivo. Here, we describe the protocol for the manufacturing of MIW, insertion of the MIW on top of a tumor and imaging of the Dendra2- labeled tumor cells using a custom built imaging box. This protocol can be used to image the metastatic behavior of tumor cells in distinct microenvironments in tumors and allows for long term imaging of blood vessels, tumor cells and host cells.