UC Riverside

Magnetic resonance imaging (MRI) is a non-invasive and non-ionizing imaging modality used to study cellular and molecular events as well as track disease progression in tissues. Due to limited sensitivity, genes, proteins and other molecules can be utilized to increase contrast in specifically labeled tissues and cells for MRI images. MRI reporters are able to provide information on gene expression, cell tracking and migration, and cellular energy metabolism. Additionally, many genes and molecules used to produce contrast may yield therapeutic benefit. Here, we take a closer look at two established MRI reporter genes: creatine and mms6, and determine their therapeutic potential.We tested the efficacy of creatine (Cr) supplementation on the brain. Recent studies suggest that Cr supplementation may improve cognitive function and memory, but the major hurdle is bypassing the blood brain barrier. Initially, we developed a creatine nasal spray and hypothesized that we could increase creatine and phosphocreatine (pCr) concentration in mouse brain. Despite multiple rounds of experiments with varying creatine concentration and duration of administrations, we did not confirm an increase in Cr or pCr in experimental groups. Due to issues resolving Cr and pCr on small tissue samples, we developed a novel pre-incubation technique to convert Cr and pCr to creatinine (Crn) and calculate the concentration of total creatine using commercially available creatine and creatinine assay kits. This technique was demonstrated on Cr and pCr standards as well as mouse muscle and brain tissue. We tested the ability of MRI reporter mms6 to enhance gemcitabine cytotoxicity on pancreatic tumor cell line, PANC-1. Mms6 is an iron binding protein found in magnetotactic bacteria. When the mms6 gene is expressed in mammalian cells, they increase iron uptake and storage producing measurable contrast in T2-weighted MRI images. We created a PANC-mms6 cell line capable of producing MRI contrast, and treated them with a common pancreatic cancer drug, gemcitabine. Given its resistant nature in PANC-1 cells, we hypothesized that we could increase cytotoxicity and cell death in PANC-mms6 cells over non-expressing PANC-WT cells. The results revealed a significant reduction in viability of PANC-mms6 cells after treatment with gemcitabine while PANC-WT cells remained viable under the same conditions.