High temporal resolution fluorescence measurements of a mitochondrial dye for detection of early stage apoptosis

Performance of TMRM and Mitotrackers in mitochondrial morphofunctional analysis of primary human skin fibroblasts

Mitochondrial membrane potential (Δψ) and morphology are considered key readouts of mitochondrial functional state. This morphofunction can be studied using fluorescent dyes ("probes") like tetramethylrhodamine methyl ester (TMRM) and Mitotrackers (MTs). Although these dyes are broadly used, information comparing their performance in mitochondrial morphology quantification and Δψ-sensitivity in the same cell model is still scarce. Here we applied epifluorescence microscopy of primary human skin fibroblasts to evaluate TMRM, Mitotracker Red CMXros (CMXros), Mitotracker Red CMH2Xros (CMH2Xros), Mitotracker Green FM (MG) and Mitotracker Deep Red FM (MDR). All probes were suited for automated quantification of mitochondrial morphology parameters when Δψ was normal, although they did not deliver quantitatively identical results. The mitochondrial localization of TMRM and MTs was differentially sensitive to carbonyl cyanide-4-phenylhydrazone (FCCP)-induced Δψ depolarization, decreasing in the order: TMRM ≫ CHM2Xros = CMXros = MDR > MG. To study the effect of reversible Δψ changes, the impact of photo-induced Δψ "flickering" was studied in cells co-stained with TMRM and MG. During a flickering event, individual mitochondria displayed subsequent TMRM release and uptake, whereas this phenomenon was not observed for MG. Spatiotemporal and computational analysis of the flickering event provided evidence that TMRM redistributes between adjacent mitochondria by a mechanism dependent on Δψ and TMRM concentration. In summary, this study demonstrates that: (1) TMRM and MTs are suited for automated mitochondrial morphology quantification, (2) numerical data obtained with different probes is not identical, and (3) all probes are sensitive to FCCP-induced Δψ depolarization, with TMRM and MG displaying the highest and lowest sensitivity, respectively. We conclude that TMRM is better suited for integrated analysis of Δψ and mitochondrial morphology than the tested MTs under conditions that Δψ is not substantially depolarized.

Tumor ablation due to inhomogeneous anisotropic diffusion in generic three-dimensional topologies

In recent decades computer-aided technologies have become prevalent in medicine, however, cancer drugs are often only tested on in vitro cell lines from biopsies. We derive a full three-dimensional model of inhomogeneous -anisotropic diffusion in a tumor region coupled to a binary population model, which simulates in vivo scenarios faster than traditional cell-line tests. The diffusion tensors are acquired using diffusion tensor magnetic resonance imaging from a patient diagnosed with glioblastoma multiform. Then we numerically simulate the full model with finite element methods and produce drug concentration heat maps, apoptosis hotspots, and dose-response curves. Finally, predictions are made about optimal injection locations and volumes, which are presented in a form that can be employed by doctors and oncologists.

Regulating intracellular ROS signal by a dual pH/reducing-responsive nanogels system promotes tumor cell apoptosis

Purpose: The levels of reactive oxygen species (ROS) in tumor cells are much higher than that in normal cells, and rise rapidly under the influence of exogenous or endogenous inducing factors, eventually leading to the apoptosis of tumor cells. Therefore, this study prepared a dual pH/reducing-responsive poly (N-isopropylacrylamide-co-Cinnamaldehyde-co-D-α-tocopheryl polyethylene glycol 1000 succinate, PssNCT) nanogels, which employed two exogenous ROS inducers, cinnamaldehyde (CA) and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), to selectively induce apoptosis by regulating ROS levels in tumor cells. Methods: The PssNCT nanogels were prepared by the free radical precipitation polymerization under the crosslink between pH-sensitive hydrazone and reducing-sensitive disulfide bonds, followed by the physicochemical and morphological characteristics investigations. Plasma stability, dual pH/reducing responsive degradation and in vitro release were also assessed. In cell experiments, cytotoxicity in different cells were first detected. The intracellular ROS levels and mitochondrial functions of tumor cells were then evaluated. Moreover, the apoptosis and western-blot assays were employed to verify the association between ROS levels elevation and apoptosis in tumor cells. Results: The nanogels exhibited a round-like hollow structure with the diameter smaller than 200nm. The nanogels were stable in plasma, while showed rapid degradation in acidic and reducing environments, thus achieving significant release of CA and TPGS in these media. Furthermore, the sufficient amplification of ROS signals was induced by the synergistically function of CA and TPGS on mitochondria, which resulted in the opening of the mitochondrial apoptotic pathway and enhanced cytotoxicity on MCF-7 cells. However, nanogels barely affected L929 cells owing to their lower intracellular ROS basal levels. Conclusion: The specific ROS regulation method achieved by these nanogels could be explored to selectively kill tumor cells according to the difference of ROS signals in different kinds of cells.

Detection of apoptosis using fluorescent probes

Apoptosis plays a major role in both healthy and diseased cells. The analysis of apoptosis can take advantage of multiple cellular markers, enabling the process to be studied at different time points. In this chapter, several apoptosis assay protocols are provided.

Generation of a chemical gradient across an array of 256 cell cultures in a single chip

A microfluidic diffusion diluter to create stable chemical gradients across an array of cell cultures was demonstrated. The device enabled concentration based studies to be conducted at 256 different concentrations across individual, low shear cell cultures. A gradient of staurosporine on cells stained with Mitotracker Deep Red (MTDR) showed a concentration-based effect on cell apoptosis across the cell culture array.