Flow Cytometric Analysis of Multiple Mitochondrial Parameters in Human Induced Pluripotent Stem Cells and Their Neural and Glial Derivatives
Summary
This study reports a novel approach to measure multiple mitochondrial functional parameters based on flow cytometry and double staining with two fluorescent reporters or antibodies to detect changes in mitochondrial volume, mitochondrial membrane potential, reactive oxygen species level, mitochondrial respiratory chain composition, and mitochondrial DNA.
Abstract
Mitochondria are important in the pathophysiology of many neurodegenerative diseases. Changes in mitochondrial volume, mitochondrial membrane potential (MMP), mitochondrial production of reactive oxygen species (ROS), and mitochondrial DNA (mtDNA) copy number are often features of these processes. This report details a novel flow cytometry-based approach to measure multiple mitochondrial parameters in different cell types, including human induced pluripotent stem cells (iPSCs) and iPSC-derived neural and glial cells. This flow-based strategy uses live cells to measure mitochondrial volume, MMP, and ROS levels, as well as fixed cells to estimate components of the mitochondrial respiratory chain (MRC) and mtDNA-associated proteins such as mitochondrial transcription factor A (TFAM).
By co-staining with fluorescent reporters, including MitoTracker Green (MTG), tetramethylrhodamine ethyl ester (TMRE), and MitoSox Red, changes in mitochondrial volume, MMP, and mitochondrial ROS can be quantified and related to mitochondrial content. Double staining with antibodies against MRC complex subunits and translocase of outer mitochondrial membrane 20 (TOMM20) permits the assessment of MRC subunit expression. As the amount of TFAM is proportional to mtDNA copy number, the measurement of TFAM per TOMM20 gives an indirect measurement of mtDNA per mitochondrial volume. The entire protocol can be carried out within 2-3 h. Importantly, these protocols allow the measurement of mitochondrial parameters, both at the total level and the specific level per mitochondrial volume, using flow cytometry.
Introduction
Mitochondria are essential organelles present in almost all eukaryotic cells. Mitochondria are responsible for energy supply by producing adenosine triphosphate (ATP) via oxidative phosphorylation and act as metabolic intermediaries for biosynthesis and metabolism. Mitochondria are deeply involved in many other important cellular processes, such as ROS generation, cell death, and intracellular Ca2+ regulation. Mitochondrial dysfunction has been associated with various neurodegenerative diseases, including Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD), Friedreich's ataxia (FRDA), and amyotrophic lateral sclerosis (ALS)1. Increased mitochondrial dysfunction and mtDNA abnormality are also thought to contribute to human aging2,3.
Various types of mitochondrial dysfunction occur in neurodegenerative diseases, and changes in mitochondrial volume, MMP depolarization, production of ROS, and alterations in mtDNA copy number are common4,5,6,7. Therefore, the ability to measure these and other mitochondrial functions is of great importance when studying disease mechanisms and testing potential therapeutic agents. Moreover, in view of the lack of animal models that faithfully replicate human neurodegenerative diseases, establishing suitable in vitro model systems that recapitulate the human disease in brain cells is an important step towards a greater understanding of these diseases and the development of new therapies2,3,8,9.
Human iPSCs can be used to generate various brain cells, including neuronal and non-neuronal cells (i.e., glial cells), and mitochondrial damage associated with neurodegenerative disease has been found in both cell types3,10,11,12,13. Appropriate methods for iPSC differentiation into neural and glial lineages are available14,15,16. These cells provide a unique human/patient platform for in vitro disease modeling and drug screening. Further, as these are derived from patients, iPSC-derived neurons and glial cells provide disease models that reflect what is happening in humans more accurately.
To date, few convenient and reliable methods for measuring multiple mitochondrial functional parameters in iPSCs, particularly living neurons and glial cells, are available. The use of flow cytometry provides the scientist with a powerful tool for measuring biological parameters, including mitochondrial function, in single cells. This protocol provides details for the generation of different types of brain cells, including neural stem cells (NSCs), neurons, and glial astrocytes from iPSCs, as well as novel flow cytometry-based approaches to measure multiple mitochondrial parameters in different cell types, including iPSCs and iPSC-derived neural and glial cells. The protocol also provides a co-staining strategy for using flow cytometry to measure mitochondrial volume, MMP, mitochondrial ROS level, MRC complexes, and TFAM. By incorporating measures of mitochondrial volume or mass, these protocols also allow the measurement of both total level and specific level per mitochondrial unit.
Protocol
Representative Results
Discussion
Herein are protocols for generating iPSC−derived neurons and astrocytes and evaluating multiple aspects of mitochondrial function using flow cytometry. These protocols allow efficient conversion of human iPSCs into both neurons and glial astrocytes and the detailed characterization of mitochondrial function, mostly in living cells. The protocols also provide a co-staining flow cytometry-based strategy for acquiring and analyzing multiple mitochondrial functions, including volume, MMP, and mitochondrial ROS lev…
Divulgations
The authors have nothing to disclose.
Acknowledgements
We kindly thank the Molecular Imaging Centre and the Flow Cytometry Core Facility at the University of Bergen in Norway. This work was supported by funding from the Norwegian Research Council (Grant number: 229652), Rakel og Otto Kr.Bruuns legat and the China Scholarship Council (project number: 201906220275).
Materials
| anti-Oct4 | Abcam | ab19857, RRID:AB_445175 | Primary Antibody; use as 1:100, 10 μL in 1000 μL staining solution; use Alexa Fluor ® 488 goat anti-rabbit IgG (1:400, Thermo Fisher Scientific, Catalog # A-11008) as secondary antibody. |
| anti-SSEA4 | Abcam | ab16287, RRID:AB_778073 | Primary Antibody; use as 1:100, 10 μL in 1000 μL staining solution; use Alexa Fluor ® 594 goat anti-mouse IgG (1:800, Thermo Fisher Scientific, Catalog # A-11005) as secondary antibody. |
| anti-Sox2 | Abcam | ab97959, RRID:AB_2341193 | Primary Antibody; use as 1:100, 10 μL in 1000 μL staining solution; use Alexa Fluor ® 488 goat anti-rabbit IgG (1:400, Thermo Fisher Scientific, Catalog # A-11008) as secondary antibody. |
| anti-Pax6 | Abcam | ab5790, RRID:AB_305110 | Primary Antibody; use as 1:100, 10 μL in 1000 μL staining solution; use Alexa Fluor ® 488 goat anti-rabbit IgG (1:400, Thermo Fisher Scientific, Catalog # A-11008) as secondary antibody. |
| anti-Nestin | Santa Cruz Biotechnology | sc-23927, RRID:AB_627994 | Primary Antibody; use as 1:50, 20 μL in 1000 μL staining solution; use Alexa Fluor ® 594 goat anti-mouse IgG (1:800, Thermo Fisher Scientific, Catalog # A-11005) as secondary antibody. |
| anti-GFAP | Abcam | ab4674, RRID:AB_304558 | Primary Antibody; use as 1:100, 10 μL in 1000 μL staining solution; use Alexa Fluor ® 594 goat anti-chicken IgG (1:800, Thermo Fisher Scientific, Catalog # A-11042) as secondary antibody. |
| anti-S100β conjugated with Alexa Fluor 488 | Abcam | ab196442, RRID:AB_2722596 | Primary Antibody; use as 1:400, 2.5 μL in 1000 μL staining solution; |
| anti-TH | Abcam | ab75875, RRID:AB_1310786 | Primary Antibody; use as 1:100, 10 μL in 1000 μL staining solution; use Alexa Fluor ® 488 goat anti-rabbit IgG (1:400, Thermo Fisher Scientific, Catalog # A-11008) as secondary antibody. |
| anti-Tuj 1 | Abcam | ab78078, RRID:AB_2256751 | Primary Antibody; use as 1:1000, 1 μL in 1000 μL staining solution; use Alexa Fluor ® 594 goat anti-mouse IgG (1:800, Thermo Fisher Scientific, Catalog # A-11005) as secondary antibody. |
| anti-Synaptophysin | Abcam | ab32127, RRID:AB_2286949 | Primary Antibody; use as 1:100, 10 μL in 1000 μL staining solution; use Alexa Fluor ® 488 goat anti-rabbit IgG (1:400, Thermo Fisher Scientific, Catalog # A-11008) as secondary antibody. |
| anti-PSD-95 | Abcam | ab2723, RRID:AB_303248 | Primary Antibody; use as 1:100, 10 μL in 1000 μL staining solution; use Alexa Fluor ® 594 goat anti-chicken IgG (1:800, Thermo Fisher Scientific, Catalog # A-11042) as secondary antibody. |
| anti-TFAM conjugated with Alexa Fluor 488 | Abcam | ab198308 | Primary Antibody; use as 1:400, 2.5 μL in 1000 μL staining solution; use mouse monoclonal IgG2b Alexa Fluor® 488 as an isotype control. |
| anti-TOMM20 conjugated with Alexa Fluor 488 | Santa Cruz Biotechnology | Cat# sc-17764 RRID:AB_628381 | Primary Antibody; use as 1:400, 2.5 μL in 1000 μL staining solution; use mouse monoclonal IgG2a Alexa Fluor® 488 as an isotype control. |
| anti-NDUFB10 | Abcam | ab196019 | Primary Antibody; use as 1:1000, 1 μL in 1000 μL staining solution; use Alexa Fluor ® 488 goat anti-rabbit IgG (1:400, Thermo Fisher Scientific, Catalog # A-11008) as secondary antibody; use rabbit monoclonal IgG as an isotype control. |
| anti-SDHA | Abcam | ab137040 | Primary Antibody; use as 1:1000, 1 μL in 1000 μL staining solution; use Alexa Fluor ® 488 goat anti-rabbit IgG (1:400, Thermo Fisher Scientific, Catalog # A-11008) as secondary antibody; use rabbit monoclonal IgG as an isotype control. |
| anti-COX IV | Abcam | ab14744, RRID:AB_301443 | Primary Antibody; use as 1:1000, 1 μL in 1000 μL staining solution; use Alexa Fluor ® 488 goat anti-mouse IgG (1:400, Thermo Fisher Scientific, Catalog # A-11001) as secondary antibody; use mouse monoclonal IgG as an isotype control. |
| Activin A | PeproTech | 120-14E | Astrocyte differentiation medium ingredient |
| ABM Basal Medium | Lonza | CC-3187 | Basal medium for astrocyte culture |
| AGM SingleQuots Supplement Pack | Lonza | CC-4123 | Supplement for astrocyte culture |
| Antibiotic-Antimycotic | Thermo Fisher Scientific | 15240062 | CDM ingredient |
| Advanced DMEM/F-12 | Thermo Fisher Scientific | 12634010 | Basal medium for dilute Geltrex |
| Bovine Serum Albumin | Europa Bioproducts | EQBAH62-1000 | Blocking agent to prevent non-specific binding of antibodies in immunostaining assays and CDM ingredient |
| BDNF | PeproTech | 450-02 | DA neurons medium ingredient |
| B-27 Supplement | Thermo Fisher Scientific | 17504044 | Astrocyte differentiation medium ingredient |
| BD Accuri C6 Plus Flow Cytometer | BD Biosciences, USA | ||
| Chemically Defined Lipid Concentrate | Thermo Fisher Scientific | 11905031 | CDM ingredient |
| Collagenase IV | Thermo Fisher Scientific | 17104019 | Reagent for gentle dissociation of human iPSCs |
| CCD Microscope Camera Leica DFC3000 G | Leica Microsystems, Germany | ||
| Corning non-treated culture dishes | Sigma-Aldrich | CLS430589 | Suspension culture |
| DPBS | Thermo Fisher Scientific | 14190250 | Used for a variety of cell culture wash |
| DMEM/F-12, GlutaMAX supplement | Thermo Fisher Scientific | 10565018 | Astrocyte differentiation basal Medium |
| EDTA | Thermo Fisher Scientific | 15575020 | Reagent for gentle dissociation of human iPSCs |
| Essential 8 Basal Medium | Thermo Fisher Scientific | A1516901 | Basal medium for iPSC culture |
| Essential 8 Supplement (50X) | Thermo Fisher Scientific | A1517101 | Supplement for iPSC culture |
| EGF Recombinant Human Protein | Thermo Fisher Scientific | PHG0314 | Supplement for NSC culture |
| FGF-basic (AA 10–155) Recombinant Human Protein | Thermo Fisher Scientific | PHG0024 | Supplement for NSC culture |
| Fetal Bovine Serum | Sigma-Aldrich | 12103C | Medium ingredient |
| FGF-basic | PeproTech | 100-18B | Astrocyte differentiation medium ingredient |
| FCCP | Abcam | ab120081 | Eliminates mitochondrial membrane potential and TMRE staining |
| Fluid aspiration system BVC control | Vacuubrand, Germany | ||
| Formaldehyde (PFA) 16% | Thermo Fisher Scientific | 28908 | Cell fixation |
| Geltrex | Thermo Fisher Scientific | A1413302 | Used for attachment and maintenance of human iPSCs |
| GlutaMAX Supplement | Thermo Fisher Scientific | 35050061 | Supplement for NSC culture |
| GDNF | Peprotech | 450-10 | DA neurons medium ingredient |
| Glycine | Sigma-Aldrich | G8898 | Used for blocking buffer |
| Ham's F-12 Nutrient Mix | Thermo Fisher Scientific | 31765027 | Basal medium for CDM |
| Heregulin beta-1 human | Sigma-Aldrich | SRP3055 | Astrocyte differentiation medium ingredient |
| Hoechst 33342 | Thermo Fisher Scientific | H1399 | Stain the nuclei for confocal image |
| Heracell 150i CO2 Incubators | Fisher Scientific, USA | ||
| IMDM | Thermo Fisher Scientific | 21980032 | Basal medium for CDM |
| Insulin | Roche | 1376497 | CDM ingredient |
| InSolution AMPK Inhibitor | Sigma-Aldrich | 171261 | Neural induction medium ingredient |
| Insulin-like Growth Factor-I human | Sigma-Aldrich | I3769 | Astrocyte differentiation medium ingredient |
| KnockOut DMEM/F-12 medium | Thermo Fisher Scientific | 12660012 | Basal medium for NSC culture |
| Laminin | Sigma-Aldrich | L2020 | Promotes attachment and growth of neural cells in vitro |
| Leica TCS SP8 STED confocal microscope | Leica Microsystems, Germany | ||
| Monothioglycerol | Sigma-Aldrich | M6145 | CDM ingredient |
| MitoTracker Green FM | Thermo Fisher Scientific | M7514 | Used for mitochondrial volume indicator |
| MitoSox Red | Thermo Fisher Scientific | M36008 | Used for mitochondrial ROS indicator |
| N-Acetyl-L-cysteine | Sigma-Aldrich | A7250 | Neural induction medium ingredient |
| N-2 Supplement | Thermo Fisher Scientific | 17502048 | Astrocyte differentiation medium ingredient |
| Normal goat serum | Thermo Fisher Scientific | PCN5000 | Used for blocking buffer |
| Orbital shakers – SSM1 | Stuart Equipment, UK | ||
| Poly-L-ornithine solution | Sigma-Aldrich | P4957 | Promotes attachment and growth of neural cells in vitro |
| Poly-D-lysine hydrobromide | Sigma-Aldrich | P7405 | Promotes attachment and growth of neural cells in vitro |
| Purmorphamine | STEMCELL Technologies | 72204 | Promotes DA neuron differentiation |
| ProLong Gold Antifade Mountant | Thermo Fisher Scientific | P36930 | Mounting the coverslip for confocal image |
| PBS 1x | Thermo Fisher Scientific | 18912014 | Used for a variety of wash |
| Recombinant Human/Mouse FGF-8b Protein | R&D Systems | 423-F8-025/CF | Promotes DA neuron differentiation |
| SB 431542 | Tocris Bioscience | TB1614-GMP | Neural Induction Medium ingredient |
| StemPro Neural Supplement | Thermo Fisher Scientific | A10508-01 | Supplement for NSCs culture |
| TrypLE Express Enzyme | Thermo Fisher Scientific | 12604013 | Cell dissociation reagent |
| Transferrin | Roche | 652202 | CDM ingredient |
| TRITON X-100 | VWR International | 9002-93-1 | Used for cells permeabilization in immunostaining assays |
| TMRE | Abcam | ab113852 | Used for mitochondrial membrane potential staining |
| Water Bath Jb Academy Basic Jba5 JBA5 Grant Instruments | Grant Instruments, USA |
References
- Wang, Y., Xu, E., Musich, P. R., Lin, F. Mitochondrial dysfunction in neurodegenerative diseases and the potential countermeasure. CNS Neuroscience & Therapeutics. 25 (7), 816-824 (2019).
- Chen, A., et al. Nicotinamide riboside and metformin ameliorate mitophagy defect in induced pluripotent stem cell-derived astrocytes with POLG mutations. Frontiers in Cell and Developmental Biology. 9, 737304 (2021).
- Liang, K. X., et al. Disease-specific phenotypes in iPSC-derived neural stem cells with POLG mutations. EMBO Molecular Medicine. 12 (10), 12146 (2020).
- Chen, H., Chan, D. C. Mitochondrial dynamics–fusion, fission, movement, and mitophagy–in neurodegenerative diseases. Human Molecular Genetics. 18, 169-176 (2009).
- Lin, M. T., Beal, M. F. Mitochondrial dysfunction and oxidative stress in neurodegenerative diseases. Nature. 443 (7113), 787-795 (2006).
- Singh, A., Kukreti, R., Saso, L., Kukreti, S. Oxidative stress: A key modulator in neurodegenerative diseases. Molecules. 24 (8), 1583 (2019).
- Kondadi, A. K., Anand, R., Reichert, A. S. Functional interplay between cristae biogenesis, mitochondrial dynamics and mitochondrial DNA integrity. International Journal of Molecular Sciences. 20 (17), 4311 (2019).
- Sterneckert, J. L., Reinhardt, P., Schöler, H. R. Investigating human disease using stem cell models. Nature Reviews. Genetics. 15 (9), 625-639 (2014).
- Patani, R. Human stem cell models of disease and the prognosis of academic medicine. Nature Medicine. 26 (4), 449 (2020).
- Liang, K. X., et al. N-acetylcysteine amide ameliorates mitochondrial dysfunction and reduces oxidative stress in hiPSC-derived dopaminergic neurons with POLG mutation. Experimental Neurology. , 337 (2021).
- Kikuchi, T., et al. Human iPS cell-derived dopaminergic neurons function in a primate Parkinson’s disease model. Nature. 548 (7669), 592-596 (2017).
- Juopperi, T. A., et al. Astrocytes generated from patient induced pluripotent stem cells recapitulate features of Huntington’s disease patient cells. Molecular Brain. 5, 17 (2012).
- Liang, K. X., et al. Stem cell derived astrocytes with POLG mutations and mitochondrial dysfunction including abnormal NAD+ metabolism is toxic for neurons. bioRxiv. , (2020).
- Liu, Q., et al. Human neural crest stem cells derived from human ESCs and induced pluripotent stem cells: induction, maintenance, and differentiation into functional schwann cells. Stem Cells Translational Medicine. 1 (4), 266-278 (2012).
- Hong, Y. J., Do, J. T. Neural lineage differentiation from pluripotent stem cells to mimic human brain tissues. Frontiers in Bioengineering and Biotechnology. 7, 400 (2019).
- Lundin, A., et al. Human iPS-derived astroglia from a stable neural precursor state show improved functionality compared with conventional astrocytic models. Stem Cell Reports. 10 (3), 1030-1045 (2018).
- Liang, K. X., et al. N-acetylcysteine amide ameliorates mitochondrial dysfunction and reduces oxidative stress in hiPSC-derived dopaminergic neurons with POLG mutation. Experimental Neurology. 337, 113536 (2021).
- Pendergrass, W., Wolf, N., Poot, M. Efficacy of MitoTracker Green™ and CMXrosamine to measure changes in mitochondrial membrane potentials in living cells and tissues. Cytometry. Part A. 61 (2), 162-169 (2004).
- Keij, J. F., Bell-Prince, C., Steinkamp, J. A. Staining of mitochondrial membranes with 10-nonyl acridine orange, MitoFluor Green, and MitoTracker Green is affected by mitochondrial membrane potential altering drugs. Cytometry. 39 (3), 203-210 (2000).
- Buckman, J. F., et al. MitoTracker labeling in primary neuronal and astrocytic cultures: influence of mitochondrial membrane potential and oxidants. Journal of Neuroscience Methods. 104 (2), 165-176 (2001).
- Zanchetta, L. M., Kirk, D., Lyng, F., Walsh, J., Murphy, J. E. Cell-density-dependent changes in mitochondrial membrane potential and reactive oxygen species production in human skin cells post sunlight exposure. Photodermatology, Photoimmunology & Photomedicine. 26 (6), 311-317 (2010).
