Intravital Imaging of Human Melanoma Cells in the Mouse Ear Skin by Two-Photon Excitation Microscopy
Noninvasive imaging of reporter gene expression by two-photon excitation (2PE) laser scanning microscopy is uniquely suited to perform dynamic and multidimensional imaging down to single-cell detection sensitivity in vivo in deep tissues. Here we used 2PE microscopy to visualize green fluorescent protein (GFP) as a reporter gene in human melanoma cells implanted into the dermis of the mouse ear skin. We first provide a step-by-step methodology to set up a 2PE imaging model of the mouse ear’s skin and then apply it for the observation of the primary tumor and its associated vasculature in vivo. This approach is minimally invasive and allows repeated imaging over time and continuous visual monitoring of malignant growth within intact animals. Imaging fluorescence reporter gene expression in small living animals by 2PE provides a unique tool to investigate critical pathways and molecular events in cancer biology such as tumorigenesis and metastasis in vivo with high-spatial and temporal resolutions.
Key wordsMelanoma Metastasis Cancer cell migration Angiotropism Blood vessel Dermis Mouse ear Two-photon microscopy Multiphoton Intravital imaging Reporter gene expression
We thanks Dr. Danny Welch (The Kansas University Medical Center) for providing the C8161 GFP human melanoma cell line. 2PE microscopy was performed at the California NanoSystems Institute (CNSI) Advanced Light Microscopy/Spectroscopy Shared Resource Facility at UCLA with support from a NIH/National Center for Advancing Translational Science UCLA CTSI Grant (UL1TR000124). The authors also thank Mr. Ian Arenas from the YULA Genesis Innovation Lab for help with the 3D printing of the mouse ear stage.
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