Portable multi-parametric microscopy for noninvasive metabolic and vascular imaging of orthotopic tongue cancer models in vivo.

Significance: Precise imaging of tumor metabolism with its vascular microenvironment becomes emerging critical for cancer research because increasing evidence shows that the key attribute that allows a tumor to survive therapies is metabolic and vascular reprogramming. However, there are surprisingly few imaging techniques available to provide a systems-level view of tumor metabolism and vasculature in vivo on small animals for cancer discoveries.

Aim: We aim to develop a new multi-parametric microscope that can faithfully recapitulate in vivo metabolic and vascular changes with a wide field of view and microscope-level resolution to advance cancer-related investigations. To maximize the ease and accessibility of obtaining in vivo tissue metabolism and vasculature measurements, we aim to develop our new metabolic imaging tool with minimal cost and size, allowing one to easily quantify tissue metabolic and vascular endpoints together in vivo, advancing many critical biomedical inquiries.

Approach: We have combined fluorescence microscopy and dark-field microscopy in a re-emission geometry into one portable microscope to image the key metabolic and vascular endpoints on the same tissue site. The portable microscope was first characterized by tissue-mimicking phantoms. Then the multi-parametric system was demonstrated on small animals to image glucose uptake (using 2-NBDG) and mitochondrial membrane potential (using TMRE) along with vascular parameters (oxygen saturation and hemoglobin contents) of orthotopic tongue tumors in vivo.

Results: Our phantom studies demonstrated the capability of the portable microscope for effective measurements of several key vascular and metabolic parameters with a comparable accuracy compared with our former reported benchtop spectroscopy and imaging systems. Our in vivo animal studies revealed increased glucose uptake and mitochondrial membrane potential along with reduced vascular oxygenation in tongue tumors compared with normal tongue tissues. The spatial analysis of metabolic and vascular images showed a more heterogeneous metabolic and oxygenation profile in tongue tumors compared with normal tongue tissues.

Conclusions: Our in vivo animal studies demonstrated the capability of our portable multi-parametric microscope for imaging the key metabolic and vascular parameters at the same tissue site with about one hour delay using an orthotopic tongue tumor model in vivo. Our study showed the potential of a portable functional microscope to noninvasively evaluate tumor biology using orthotopic tongue cancer models for future head and neck cancer research.