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Quantitative evaluation of malignant gliomas damage induced by photoactivation of IR700 dye
Morito Sakuma1, Sayaka Kita1, Hideo Higuchi1
1Department of Physics, Graduate School of Science, The University of Tokyo , Tokyo , Japan.
Abstract:
The processes involved in malignant gliomas damage were quantitatively evaluated by microscopy. The near-infrared fluorescent dye IR700 that is conjugated to an anti-CD133 antibody (IR700-CD133) specifically targets malignant gliomas (U87MG) and stem cells (BT142) and is endocytosed into the cells. The gliomas are then photodamaged by the release of reactive oxygen species (ROS) and the heat induced by illumination of IR700 by a red laser, and the motility of the vesicles within these cells is altered as a result of cellular damage. To investigate these changes in motility, we developed a new method that measures fluctuations in the intensity of phase-contrast images obtained from small areas within cells. The intensity fluctuation in U87MG cells gradually decreased as cell damage progressed, whereas the fluctuation in BT142 cells increased. The endocytosed IR700 dye was co-localized in acidic organelles such as endosomes and lysosomes. The pH in U87MG cells, as monitored by a pH indicator, was decreased and then gradually increased by the illumination of IR700, while the pH in BT142 cells increased monotonically. In these experiments, the processes of cell damage were quantitatively evaluated according to the motility of vesicles and changes in pH.
Insights
This study quantifies malignant glioma damage using a novel microscopy method. The near-infrared fluorescent dye IR700-CD133 targets cancer cells, causing photodamage and altering vesicle motility and pH.
Area of Science:
- Biomedical Engineering
- Cell Biology
- Cancer Research
Background:
- Malignant gliomas are aggressive brain tumors.
- Targeted therapies are crucial for treating gliomas.
- Understanding cellular damage mechanisms is key to developing new treatments.
Purpose of the Study:
- To quantitatively evaluate the cellular damage processes in malignant gliomas.
- To develop a new method for assessing cell damage based on vesicle motility and pH changes.
- To investigate the effects of IR700-CD133 mediated photodamage on glioma and stem cells.
Main Methods:
- Utilized microscopy to quantitatively evaluate damage in malignant gliomas.
- Employed a near-infrared fluorescent dye (IR700-CD133) targeting CD133+ cells (U87MG and BT142).
- Developed a novel method measuring intensity fluctuations in phase-contrast images to assess vesicle motility.
- Monitored intracellular pH changes using a pH indicator.
Main Results:
- IR700-CD133 specifically targeted and was endocytosed by U87MG and BT142 cells.
- Photodamage induced by IR700 illumination altered vesicle motility, with decreased fluctuation in U87MG cells and increased fluctuation in BT142 cells.
- Intracellular pH changes differed between cell types: U87MG cells showed a decrease then increase, while BT142 cells exhibited a monotonic increase.
- IR700 dye co-localized with acidic organelles (endosomes, lysosomes).
Conclusions:
- The developed method effectively quantifies cellular damage in malignant gliomas.
- Vesicle motility and intracellular pH are sensitive indicators of photodamage.
- Differential responses in motility and pH suggest distinct cellular responses to damage in glioma and stem cells.
- This approach offers a new tool for evaluating therapeutic efficacy and understanding glioma biology.
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