Mapping metabolic activity using functional Mass Spectrometry Imaging (fMSI)

Determining how diseased tissue functions differently from normal, healthy tissue is usually accomplished by profiling the differences in genetic content (genome), protein content (proteome) or metabolites (metabolome). However, these approaches offer a limited understanding as they are static measures of tissue content at one point in time and do not inform as to how these components function together. This is similar to determining how an automobile functions (or dysfunctions) just from an inventory of its parts. My laboratory has focused on metabolic dynamics as a functional measure of the interaction of genes, proteins and metabolic under the influence of regulatory processes and the tissue environment. In order to do this, we have developed a novel functional mass spectrometry imaging method to provide metabolic dynamic information at high spatial resolution.

In collaboration with Dr. David Muddiman of the NCSU Chemistry Department and Dr. Shawn Gomez in UNC/NCSU BME, we are mapping the spatial differences in metabolic activity in mouse tissues as part of a new multi-PI R01 grant.  Using a novel infusion protocol, stable isotope labeling is tracked as a function of time and spatial location in normal mouse tissues and mouse mammary tumors using state-of-the-art mass spectrometry imaging methods developed in the Muddiman laboratory. These data are fit to metabolic models developed in collaboration with the Gomez laboratory to detail the metabolic networks involved in maintaining tissue function. The effect of static or changing oxygenation levels on tissue functional properties is measured using 2-nitroimidazole dyes. These approaches allow us to map the rate of metabolic turnover rather than the static picture of genes, proteins or metabolites in the tissue.

We hypothesize that functional measures form a complete picture of how tumor tissue differs from normal, healthy tissue. This value of functional studies is illustrated by the unique functional measures provided by positron emission tomography used in clinical studies.  Our fMSI approach offers higher spatial resolution and access to a greater array of functional pathways to better identify disease biomarkers and therapeutic targets.

Effects of oxygen on cell growth, molecular profile and toxicity response

Oxygen levels in healthy tissue range from a high pO2 level adjacent to arterioles of approximately 100 mmHg down to hypoxic levels (<10 mmHg). In tumors, hypoxia and even anoxic tissue is commonly observed. In addition, due to poorly formed vasculature, some regions of tumor tissue experience cycling oxygen levels. Clinical studies have shown that patient tumors with a high fraction of hypoxic tissue is correlated with aggressive cancer, so determining the influence of oxygen on tissue function is critical to treating the most deadly cancers. However, oxygen is difficult to measure or control in vivo, so our laboratory has developed novel devices to screen cell growth and response under a range of static and cycling environments. We use these devices to screen for markers of static and cycling hypoxia in cancer cells and to determine how these cells respond to therapy. These in vitro studies can be compared to in vivo studies of tissue function under varying oxygen environments.  In addition, in normal cell lines, we can perform risk assessment studies upon exposure of cells to environmental toxins under physiologically relevant oxygen levels.