Three-dimensional microscopy of the tumor microenvironment in vivo using optical frequency domain imaging

Abstract

Optical frequency domain imaging (OFDI) is a wide-field, three-dimensional intravital imaging technique that provides information on the entire tumor vasculature and surrounding tissue microenvironment, allowing visualization of angiogenesis and lymphangiogenesis during tumor growth and with therapy. Here, Vakoc et al. show that, in contrast to multiphoton microscopy, OFDI can image at greater tissue depths with a wider field of view and without the need for exogenous contrast agents. Intravital multiphoton microscopy has provided powerful mechanistic insights into health and disease and has become a common instrument in the modern biological laboratory. The requisite high numerical aperture and exogenous contrast agents that enable multiphoton microscopy, however, limit the ability to investigate substantial tissue volumes or to probe dynamic changes repeatedly over prolonged periods. Here we introduce optical frequency domain imaging (OFDI) as an intravital microscopy that circumvents the technical limitations of multiphoton microscopy and, as a result, provides unprecedented access to previously unexplored, crucial aspects of tissue biology. Using unique OFDI-based approaches and entirely intrinsic mechanisms of contrast, we present rapid and repeated measurements of tumor angiogenesis, lymphangiogenesis, tissue viability and both vascular and cellular responses to therapy, thereby demonstrating the potential of OFDI to facilitate the exploration of physiological and pathological processes and the evaluation of treatment strategies.