A novel bioreactor for combined magnetic resonance spectroscopy and optical imaging of metabolism in 3D cell cultures

Abstract

Purpose Fluorescence lifetime imaging microscopy (FLIM) of endogenous fluorescent metabolites permits the measurement of cellular metabolism in cell, tissue and animal models. In parallel, magnetic resonance spectroscopy (MRS) of dynamic nuclear (hyper)polarized (DNP) 13C‐pyruvate enables measurement of metabolism at larger in vivo scales. Presented here are the design and initial application of a bioreactor that connects these 2 metabolic imaging modalities in vitro, using 3D cell cultures. Methods The model fitting for FLIM data analysis and the theory behind a model for the diffusion of pyruvate into a collagen gel are detailed. The device is MRI‐compatible, including an optical window, a temperature control system and an injection port for the introduction of contrast agents. Three‐dimensional printing, computer numerical control machining and laser cutting were used to fabricate custom parts. Results Performance of the bioreactor is demonstrated for 4 T1 murine breast cancer cells under glucose deprivation. Mean nicotinamide adenine dinucleotide (NADH) fluorescence lifetimes were 10% longer and hyperpolarized 13C lactate:pyruvate (Lac:Pyr) ratios were 60% lower for glucose‐deprived 4 T1 cells compared to 4 T1 cells in normal medium. Looking at the individual components of the NADH fluorescent lifetime, τ1 (free NADH) showed no significant change, while τ2 (bound NADH) showed a significant increase, suggesting that the increase in mean lifetime was due to a change in bound NADH. Conclusion A novel bioreactor that is compatible with, and can exploit the benefits of, both FLIM and 13C MRS in 3D cell cultures for studies of cell metabolism has been designed and applied.

FLIM as a Promising Tool for Cancer Diagnosis and Treatment Monitoring

“…Under some conditions, the long lifetime τ 2 (bound-NADH lifetime) is more sensitive, as indicated by the metabolic changes in breast cancer cells under glucose deprivation conditions [ 50 ]. Additionally, under enzymatic activity changes in glycometabolism, when using 10 μM FX11-inhibiting lactate dehydrogenase (LDH) and 50 mM dichloroacetate-relieving pyruvate dehydrogenase kinases (PDK) inhibition on the PDH of the cancer cells, the lifetime change is more obvious in τ 2 group.…”

Intracellular Sodium Changes in Cancer Cells Using a Microcavity Array-Based Bioreactor System and Sodium Triple-Quantum MR Signal

“…The non-invasive capability of the MR technique to obtain a variety of physiological information resulted in a large effort to investigate living cells in bioreactor systems by MR [31][32][33]35,[61][62][63][64][65][66][67][68][69][70][71][72][73][74][75]. In general, the low sensitivity of the MR technique requires a high cell density/number, which can be obtained by densely packed 3D cell cultures, to achieve a sufficient SNR within a high temporal resolution.…”

Metabolic mapping of glioblastoma stem cells reveals NADH fluxes associated with glioblastoma phenotype and survival

“…Cellular metabolic information provided by FLIM can be coupled with either in vivo photoacoustic measurements of glucose uptake in the mouse brain 46 or magnetic resonance spectroscopy of 13 C-pyruvate to track metabolic changes across multiple spatial scales. 47 In addition, Shah et al 48 successfully used NADH FLIM parameters, such as mean lifetime and amount of free NAD(P)H, to quantify cellular heterogeneity across cells and to track the metabolic response to chemotherapy treatment. GBM is a complicated heterogeneous cancer model with a hierarchy of subtypes and different cell populations, and we propose that characterizing the GSC influence on metabolic plasticity provides a more comprehensive understanding of this cancer.…”