This work is supported by the Intramural Research Program of the National Eye Institute (ZIAEY000450 and ZIAEY000546).

All mouse protocols were approved by the Animal Care and Use Committee of the National Eye Institute (NEI ASP# 650). Mice were housed in 12 h light-dark conditions and cared for by following the recommendations of the Guide for the Care and Use of Laboratory Animals, the Institute of Laboratory Animal Resources, and the Public Health Service Policy on Humane Care and Use of Laboratory Animals.
1. Hydrating sensor cartridge and preparation of the assay medium
<ol>
	<li>The day before the expe...

<ol>
	<li>Nunnari, J., Suomalainen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondria:+In+sickness+and+in+health.">Mitochondria: In sickness and in health.</a> Cell. 148 (6), 1145-1159 (2012).</li><li>Wong-Riley, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Energy+metabolism+of+the+visual+system.">Energy metabolism of the visual system.</a> Eye Brain. 2, 99-116 (2010).</li><li>Yu, D. Y., Cringle, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxygen+distribution+and+consumption+within+the+retina+in+vascularised+and+avascular+retinas+and+in+animal+models+of+retinal+disease.">Oxygen distribution and consumption within the retina in vascularised and avascular retinas and in animal models of retinal disease.</a> Progress in Retina and Eye Research. 20, 175-208 (2001).</li><li>Barot, M., Gokulgandhi, M. R., Mitra, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+dysfunction+in+retinal+diseases.">Mitochondrial dysfunction in retinal diseases.</a> Current Eye Research. 36 (12), 1069-1077 (2011).</li><li>Joyal, J. S., Gantner, M. L., Smith, L. E. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinal+energy+demands+control+vascular+supply+of+the+retina+in+development+and+disease:+The+role+of+neuronal+lipid+and+glucose+metabolism.">Retinal energy demands control vascular supply of the retina in development and disease: The role of neuronal lipid and glucose metabolism.</a> Progress in Retina and Eye Research. 64, 131-156 (2018).</li><li>Hurley, J. B., Lindsay, K. J., Du, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glucose,+lactate,+and+shuttling+of+metabolites+in+vertebrate+retinas.">Glucose, lactate, and shuttling of metabolites in vertebrate retinas.</a> Journal of Neuroscience Research. 93 (7), 1079-1092 (2015).</li><li>Haydinger, C. D., Kittipassorn, T., Peet, D. 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J., Sennlaub, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Is+retinal+metabolic+dysfunction+at+the+center+of+the+pathogenesis+of+age-related+macular+degeneration.">Is retinal metabolic dysfunction at the center of the pathogenesis of age-related macular degeneration.</a> International Journal of Molecular Sciences. 20 (3), (2019).</li><li>Vlachantoni, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+of+severe+mitochondrial+oxidative+stress+and+a+protective+effect+of+low+oxygen+in+mouse+models+of+inherited+photoreceptor+degeneration.">Evidence of severe mitochondrial oxidative stress and a protective effect of low oxygen in mouse models of inherited photoreceptor degeneration.</a> Human Molecular Genetics. 20 (2), 322-335 (2011).</li><li>Grenell, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loss+of+MPC1+reprograms+retinal+metabolism+to+impair+visual+function.">Loss of MPC1 reprograms retinal metabolism to impair visual function.</a> Proceedings of the National Academy of Science U. S. A. 116 (9), 3530-3535 (2019).</li><li>Wright, A. F., Chakarova, C. F., Abd El-Aziz, M. M., Bhattacharya, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photoreceptor+degeneration:+genetic+and+mechanistic+dissection+of+a+complex+trait.">Photoreceptor degeneration: genetic and mechanistic dissection of a complex trait.</a> Nature Reviews in Genetics. 11 (4), 273-284 (2010).</li><li>Jarrett, S. G., Boulton, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Consequences+of+oxidative+stress+in+age-related+macular+degeneration.">Consequences of oxidative stress in age-related macular degeneration.</a> Molecular Aspects of Medicine. 33 (4), 399-417 (2012).</li><li>Rozing, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Age-related+macular+degeneration:+A+two-level+model+hypothesis.">Age-related macular degeneration: A two-level model hypothesis.</a> Progress in Retina Eye Research. 76, 100825 (2020).</li><li>Yokosako, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glycolysis+in+patients+with+age-related+macular+degeneration.">Glycolysis in patients with age-related macular degeneration.</a> Open Ophthalmology Journal. 8, 39-47 (2014).</li><li>Bek, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mitochondrial+dysfunction+and+diabetic+retinopathy.">Mitochondrial dysfunction and diabetic retinopathy.</a> Mitochondrion. 36, 4-6 (2017).</li><li>Yumnamcha, T., Guerra, M., Singh, L. P., Ibrahim, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabolic+dysregulation+and+neurovascular+dysfunction+in+diabetic+retinopathy.">Metabolic dysregulation and neurovascular dysfunction in diabetic retinopathy.</a> Antioxidants. 9 (12), (2020).</li><li>Futterman, S., Kinoshita, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabolism+of+the+retina.+I.+Respiration+of+cattle+retina.">Metabolism of the retina. I. Respiration of cattle retina.</a> Journal of Biological Chemistry. 234 (4), 723-726 (1959).</li><li>Linsenmeier, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+light+and+darkness+on+oxygen+distribution+and+consumption+in+the+cat+retina.">Effects of light and darkness on oxygen distribution and consumption in the cat retina.</a> Journal of General Physiology. 88 (4), 521-542 (1986).</li><li>Medrano, C. J., Fox, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxygen+consumption+in+the+rat+outer+and+inner+retina:+light-+and+pharmacologically-induced+inhibition.">Oxygen consumption in the rat outer and inner retina: light- and pharmacologically-induced inhibition.</a> Experiments in Eye Research. 61 (3), 273-284 (1995).</li><li>Kooragayala, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+oxygen+consumption+in+retina+ex+vivo+demonstrates+limited+reserve+capacity+of+photoreceptor+mitochondria.">Quantification of oxygen consumption in retina ex vivo demonstrates limited reserve capacity of photoreceptor mitochondria.</a> Investigative Ophthalmology and Visual Science. 56 (13), 8428-8436 (2015).</li><li>Adlakha, Y. K., Swaroop, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+mitochondrial+oxygen+consumption+in+the+retina+ex+vivo:+applications+for+retinal+disease.">Determination of mitochondrial oxygen consumption in the retina ex vivo: applications for retinal disease.</a> Methods in Molecular Biology. 1753, 167-177 (2018).</li><li>. Agilent Mitocondrial stress test user guide Available from: <a target="_blank" href="https://www.agilent.com/cs/library/usermanuals/public/XF_Cell_Mito_Stress_Test_Kit_User_Guide.pdf">https://www.agilent.com/cs/library/usermanuals/public/XF_Cell_Mito_Stress_Test_Kit_User_Guide.pdf</a> (2021)</li><li>. Agilent Glycolytic rate assay user guide Available from: <a target="_blank" href="https://www.agilent.com/cs/library/usermanuals/public/103344-400.pdf">https://www.agilent.com/cs/library/usermanuals/public/103344-400.pdf</a> (2021)</li><li>. Agilent wave 2.6 user guide Available from: <a target="_blank" href="https://www.agilent.com/cs/library/usermanuals/public/103344-400.pdf">https://www.agilent.com/cs/library/usermanuals/public/103344-400.pdf</a> (2021)</li><li>. AVMA Guidelines for the Euthanasia of Animals Available from: <a target="_blank" href="https://www.avma.org/sites/default/files/2020-01/2020-Euthanasia-Final-1-17-20.pdf">https://www.avma.org/sites/default/files/2020-01/2020-Euthanasia-Final-1-17-20.pdf</a> (2021)</li><li>. Improving Quantification of Cellular Glycolytic Rate Using Agilent Seahorse XF Technology Available from: <a target="_blank" href="https://www.agilent.com/cs/library/whitepaper/public/whitepaper-improve-quantification-of-cellular-glycolytic-rate-cell-analysis-5991-7894en-agilent.pdf">https://www.agilent.com/cs/library/whitepaper/public/whitepaper-improve-quantification-of-cellular-glycolytic-rate-cell-analysis-5991-7894en-agilent.pdf</a> (2021)</li><li>. Report Generator User Guide Agilent Seahorse XF Cell Mito Stress Test Available from: <a target="_blank" href="https://www.agilent.com/cs/library/usermanuals/public/Report_Generator_User_Guide_Seahorse_XF_Cell_Mito_Stress_Test_Single_File.pdf">https://www.agilent.com/cs/library/usermanuals/public/Report_Generator_User_Guide_Seahorse_XF_Cell_Mito_Stress_Test_Single_File.pdf</a> (2021)</li><li>. Agilent Seahorse XF Buffer Factor Protocol Available from: <a target="_blank" href="https://www.agilent.com/cs/library/usermanuals/public/usermanual-xf-buffer-factor-protocol-cell-analysis-S7888-10010en-agilent.pdf">https://www.agilent.com/cs/library/usermanuals/public/usermanual-xf-buffer-factor-protocol-cell-analysis-S7888-10010en-agilent.pdf</a> (2021)</li><li>. Agilent sensor cartridges and cell culture microplates Available from: <a target="_blank" href="https://www.agilent.com/cs/library/brochures/5991-8657EN_seahorse_plastics_brochure.pdf">https://www.agilent.com/cs/library/brochures/5991-8657EN_seahorse_plastics_brochure.pdf</a> (2021)</li><li>. Agilent Seahorse XF Glycolysis Stress Test Kit User Guide Available from: <a target="_blank" href="https://www.agilent.com/cs/library/usermanuals/public/XF_Glycolysis_Stress_Test_Kit_User_Guide.pdf">https://www.agilent.com/cs/library/usermanuals/public/XF_Glycolysis_Stress_Test_Kit_User_Guide.pdf</a> (2021)</li><li>Fan, Y. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+bioassay+to+measure+energy+metabolism+in+mouse+colonic+crypts,+organoids,+and+sorted+stem+cells.">A bioassay to measure energy metabolism in mouse colonic crypts, organoids, and sorted stem cells.</a> American Journal of Physiology-Gastrointestinal and Liver Physiology. 309, 1-9 (2015).</li><li>Huang, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ductal+pancreatic+cancer+modeling+and+drug+screening+using+human+pluripotent+stem+cell-+and+patient-derived+tumor+organoids.">Ductal pancreatic cancer modeling and drug screening using human pluripotent stem cell- and patient-derived tumor organoids.</a> Nature Medicine. 21 (11), 1364-1371 (2015).</li><li>Jeon, C. J., Strettoi, E., Masland, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+major+cell+populations+of+the+mouse+retina.">The major cell populations of the mouse retina.</a> Journal of Neuroscience. 18 (21), 8936-8946 (1998).</li><li>Akimoto, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+of+GFP+to+newborn+rods+by+Nrl+promoter+and+temporal+expression+profiling+of+flow-sorted+photoreceptors.">Targeting of GFP to newborn rods by Nrl promoter and temporal expression profiling of flow-sorted photoreceptors.</a> Proceedings of the National Academy of Science U. S. A. 103 (10), 3890-3895 (2006).</li><li>Kenwood, B. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+a+novel+mitochondrial+uncoupler+that+does+not+depolarize+the+plasma+membrane.">Identification of a novel mitochondrial uncoupler that does not depolarize the plasma membrane.</a> Molecular Metabolism. 3 (2), 114-123 (2014).</li><li>Corso-Diaz, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome-wide+profiling+identifies+DNA+methylation+signatures+of+aging+in+rod+photoreceptors+associated+with+alterations+in+energy+metabolism.">Genome-wide profiling identifies DNA methylation signatures of aging in rod photoreceptors associated with alterations in energy metabolism.</a> Cell Reports. 31 (3), 107525 (2020).</li><li>Berkowitz, B. 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Provided here are detailed instructions for performing microplate-based assays of mitochondrial respiration and glycolysis activity using ex vivo, freshly dissected retinal punch disks. The protocol has been optimized to: 1) ensure the use of a suitable assay medium for ex vivo retinal tissue; 2) employ proper size of retinal punch disks to obtain OCR and ECAR readings that fall within the machine&#39;s optimal detecting range; 3) coating mesh inserts to enhance the adhesiveness of retinal punch for sta...

Mitochondria are essential organelle that regulates cellular metabolism, signaling, homeostasis, and apoptosis by coordinating multiple crucial physiological processes1. Mitochondria serve as the powerhouse in the cell to generate adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS) and provide energy that supports almost all cellular events. The majority of cellular oxygen is metabolized in mitochondria, where it serves as the final electron acceptor in the electron transport chain (ETC) during aerobic respiration. Low amounts of ATP can also be produced from glycolysis in the cytosol, where glucose is converted to pyruvate, which can be further converted to lactate or be transported into mitochondria and oxidized to acetyl-CoA, a substrate in the tricarboxylic acid cycle (TCA cycle).
The retina is one of the most metabolically active tissues in mammals2, displaying high levels of mitochondrial respiration and extremely high oxygen consumption3. The rod and cone photoreceptors contain a high density of mitochondria4, and OXPHOS generates most ATP in the retina5. In addition, the retina also relies heavily on aerobic glycolysis6,7 by converting glucose to lactate5. Mitochondrial defects are associated with various neurodegenerative diseases8,9; and with its unique high energy demands, the retina is especially vulnerable to metabolic defects, including those affecting mitochondrial OXPHOS4 and glycolysis10. Mitochondrial dysfunction and defects in glycolysis are implicated in retinal11,12 and macular13 degenerative diseases, age-related macular degeneration10,14,15,16, and diabetic retinopathy17,18. Therefore, accurate measurements of mitochondrial respiration and glycolysis can provide important parameters for assessing the integrity and health of the retina.
Mitochondrial respiration can be measured through the determination of oxygen consumption rate (OCR). Given that the conversion of glucose to pyruvate and subsequently to lactate results in extrusion of protons into and acidification of the extracellular environment, measurements of the extracellular acidification rate (ECAR) provide an indication of glycolysis flux. As the retina is composed of multiple cell types with intimate relationships and active synergy, including the exchange of substrates6, it is imperative to analyze mitochondrial function and metabolism in the context of whole retinal tissue with intact lamination and circuitry. For the past several decades, the Clark type O2 electrodes and other oxygen microelectrodes have been used to measure oxygen consumption in the retina19,20,21. These oxygen electrodes have major limitations in sensitivity, requirement of a large sample volume, and the need for continuous stirring of suspending sample, which usually leads to the disruption of cellular and tissue context. The protocol described here was developed using a microplate-based, fluorescence technique to measure mitochondrial energy metabolism in freshly dissected ex vivo mouse retina tissue. It allows mid-throughput real-time measurements of both OCR and ECAR simultaneously using a small sample (1 mm punch) of ex vivo retinal tissue while avoiding the need for suspension and continuous stirring.
Demonstrated here is the experimental procedure for mitochondrial stress assay and glycolytic rate assay on freshly dissected retinal punch disks. This protocol allows the measurement of mitochondria-related metabolic activities in an ex vivo tissue context. Different from the assays performed using cultured cells, the readings obtained here reflect combined energy metabolism at the tissue level and are influenced by interactions between the different cell types within the tissue. The protocol is modified from a previously published version22,23 to adapt to the new generation of the Agilent Seahorse extracellular flux 24-wells (XFe24) analyzer with Islet Capture plate. The assay medium, injection compound concentrations, and number/duration of assay cycles have also been optimized for retinal tissue. A detailed step-by-step protocol is given for the preparation of retinal punch disks. More information on the program setup and data analysis can be obtained from the manufacturer&#39;s user guide24,25,26.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1X PBS</td>
			<td>Thermo Fisher</td>
			<td>14190-144</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Deoxy glucose (2-DG), 500 mM stock solution</td>
			<td>Sigma</td>
			<td>D6134</td>
			<td>Dissolve in Seahorse XF DMEM medium, prepare ahead of time</td>
		</tr>
		<tr>
			<td>30-gauge needle</td>
			<td>BD Precision Glide</td>
			<td>305106</td>
			<td></td>
		</tr>
		<tr>
			<td>Antimycin A, 10 mM stock solution</td>
			<td>Sigma</td>
			<td>A8674</td>
			<td>Dissolve in DMSO, prepare ahead of time</td>
		</tr>
		<tr>
			<td>Bam15, 10 mM stock solution</td>
			<td>TimTec</td>
			<td>ST056388</td>
			<td>Dissolve in DMSO, prepare ahead of time</td>
		</tr>
		<tr>
			<td>Biopsy puncher, 1 mm</td>
			<td>Integra Miltex</td>
			<td>33-31AA</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell-Tak</td>
			<td>Corning Life Sciences</td>
			<td>CB40240</td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 asphyxiation chamber</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dissection forceps-Dumont #5</td>
			<td>Fine Science Tools</td>
			<td>11251-10</td>
			<td>Stright tip</td>
		</tr>
		<tr>
			<td>Dissection forceps-Dumont #7</td>
			<td>Fine Science Tools</td>
			<td>11274-20</td>
			<td>Curved tip</td>
		</tr>
		<tr>
			<td>Dissection microscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Sigma</td>
			<td>D2438</td>
			<td></td>
		</tr>
		<tr>
			<td>Graefe forceps</td>
			<td>Fine Science Tools</td>
			<td>11051-10</td>
			<td>Curved, Serrated tip</td>
		</tr>
		<tr>
			<td>Microscissors</td>
			<td>Fine Science Tools</td>
			<td>15004-08</td>
			<td>Curved tip</td>
		</tr>
		<tr>
			<td>NaOH solution, 1 M</td>
			<td>Sigma-Aldrich</td>
			<td>S8263</td>
			<td>Aqueous solution, prepare ahead of time</td>
		</tr>
		<tr>
			<td>Rotenone, 10 mM stock solution</td>
			<td>Sigma</td>
			<td>R8875</td>
			<td>Dissolve in DMSO, prepare ahead of time</td>
		</tr>
		<tr>
			<td>Seahorse calibration medium</td>
			<td>Agilent</td>
			<td>100840-000</td>
			<td></td>
		</tr>
		<tr>
			<td>Seahorse XF 1.0 M glucose</td>
			<td>Agilent</td>
			<td>103577-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Seahorse XF 100 mM pyruvate</td>
			<td>Agilent</td>
			<td>103578-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Seahorse XF 200 mM glutamine</td>
			<td>Agilent</td>
			<td>103579-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Seahorse XF DMEM medium</td>
			<td>Agilent</td>
			<td>103575-100</td>
			<td>pH 7.4, with 5 mM HEPES</td>
		</tr>
		<tr>
			<td>Seahorse XFe24 Islet Capture FluxPak</td>
			<td>Agilent</td>
			<td>103518-100</td>
			<td>Containing Sensor Cartridge and Islet Capture microplate</td>
		</tr>
		<tr>
			<td>Seahorse XFe24, Extra Cellular Flux Analyzer</td>
			<td>Agilent</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium bicarbonate solution, 0.1 M</td>
			<td>Sigma-Aldrich</td>
			<td>S5761</td>
			<td>Aqueous solution, prepare ahead of time</td>
		</tr>
		<tr>
			<td>Superfine eyelash brush</td>
			<td>Ted Pella</td>
			<td>113</td>
			<td></td>
		</tr>
	</tbody>
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determination of mitochondrial respiration and glycolysis in ex vivo retinal tissue samples

Mitochondrial respiration is a critical energy-generating pathway in all cells, especially retinal photoreceptors that possess a highly active metabolism. In addition, photoreceptors also exhibit high aerobic glycolysis like cancer cells. Precise measurements of these metabolic activities can provide valuable insights into cellular homeostasis under physiological conditions and in disease states. High throughput microplate-based assays have been developed to measure mitochondrial respiration and various metabolic activities in live cells. However, a vast majority of these are developed for cultured cells and have not been optimized for intact tissue samples and for application ex vivo. Described here is a detailed step-by-step protocol, using microplate-based fluorescence technology, to directly measure oxygen consumption rate (OCR) as an indicator of mitochondrial respiration, as well as extracellular acidification rate (ECAR) as an indicator of glycolysis, in intact ex vivo retinal tissue. This method has been used to successfully assess metabolic activities in adult mouse retina and demonstrate its application in investigating cellular mechanisms of aging and disease.

The data reported here are representative mitochondrial stress assay showing OCR trace (Figure 1) and glycolytic rate assay showing OCR trace and ECAR trace (Figure 2), which were performed using freshly dissected 1 mm retinal punch disks from 4 months old transgenic Nrl-L-EGFP mice36 (C57B/L6 background). These mice express GFP specifically in rod photoreceptors without altering normal retinal development, histology, and physiol...

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Determination of Mitochondrial Respiration and Glycolysis in Ex Vivo Retinal Tissue Samples

Described here is a detailed protocol for performing mitochondrial stress assay and glycolytic rate assay in ex vivo retinal tissue samples using a commercial bioanalyzer.

Determination of Mitochondrial Respiration and Glycolysis in Ex Vivo Retinal Tissue Samples

Mitochondrial respiration is a critical energy-generating pathway in all cells, especially retinal photoreceptors that possess a highly active metabolism. ...

This protocol provides real-time analysis of two major bioenergetic pathways:mitochondrial respiration and glycolysis in freshly dissected ex vivo mouse retinal tissues. Traditional seahorse analysis was focused on cultured monolayered cells, while this protocol allows researchers to study mitochondrial activity in freshly dissected tissues, specifically the retina. This technique is used to study mitochondria's activities and glycolysis flags in retinas of inherited retinal degeneration mouse models.It is a useful tool to retinal research and also has potential to be applied to other type of tissue to develop potential therapies. The most difficult part of this protocol is to obtain quality punch discs from freshly dissected mouse retina, so it's recommended that the individual who will perform this technique has good retinal dissecting skills. The day before the experiment, open the sensor cartridge cassette and add one milliliter of calibration medium to each well of the utility plate.Incubate overnight in a carbon dioxide-free incubator at 37 degrees Celsius to activate the fluorophores. On the day of the experiment, prepare assay medium in dilute compound drugs from stock. Warm up the assay medium in the 37 degrees Celsius water bath.Set up the assay program on the machine as described in the text manuscript. Open the lid of the cassette containing mesh inserts. Pipette eight microliters of the coating mix to each mesh insert, then use a pipette tip to gently spread the droplet around to distribute the coating mix equally throughout the mesh insert.Close the cassette and allow the mesh inserts to incubate at room temperature for at least 25 minutes for absorption. After incubation, wash the mesh inserts by pipetting four milliliters of the assay medium directly onto the inserts. Gently shake the cassette to ensure all mesh inserts are washed with the assay medium.To prepare the retinal punch, enucleate the eyes from an adult euthanized mouse and place them into ice cold PBS in a Petri dish, then place the Petri dish under a dissection microscope. Using microscissors, cut off the optic nerve, then carefully remove the extrarectus muscles attached outside the eyeball. Using a 30 gauge needle, punch a hole at the edge of the cornea.Then use fine dissection microscissors to make a circular cut along the edge of the cornea. Using sharp dissection forceps, remove the cornea, lens, and the vitreous humor from the eye cup. Make several small cuts on the scleral layer at the rim of the eye cup using fine dissection microscissors.Use two sharp dissection forceps to hold onto the scleral tissue at each side and pull on the scleral layer very carefully to remove it from the neural retina. Repeat this around the eye cup until all sclera is removed and an intact retinal cup is obtained. Make radial cuts on the retinal cup to flatten it and generate several distinct sections using dissection microscissors.Next, using a one millimeter diameter biopsy puncher, cut one retinal disc from each section of the flattened retinal cup. Punch at an equal distance from the optic nerve head. Transfer the pre-coated mesh inserts into the dissection Petri dish using forceps.With the help of two super fine eyelash brushes, place the retinal punch disc at the center of the mesh insert with the ganglion cell layer side down touching the mesh and the photoreceptor layer facing up. To load the sensor cartridge, take the hydrated sensor cartridge plate cassette out of the 37 degree Celsius incubator. After removing the hydro booster cover, place the sensor cartridge back on the utility plate.Load the desired volume of injection compound solutions into appropriate ports by holding the pipette tip at a 45 degree angle, inserting the pipette tip halfway into an injection port with the bevel of the tip against the opposite wall of the injection port. Gently load the compound into each port. Load the sensor cartridge into the machine for calibration by clicking start run button to open the machine tray.Place the sensor cartridge into the machine and click I am ready button to start calibration. Load desired volume of the assay medium into each well of the islet capture plate. Using forceps, grab the rim of the mesh insert containing retinal punch discs and take it out from the Petri dish.Lightly tap the bottom of the mesh insert on an absorbing wipe tissue to remove extra liquid and put it into the well of the islet capture plate. Repeat this step until all mesh inserts with retinal punches are placed into the islet capture plate filling the background correction wells and blank wells with empty mesh inserts. Using two Graefe forceps, press the rim of each mesh insert carefully and gently, making sure that these are securely inserted at the bottom of the islet capture plate.Place the loaded islet capture plate into a 37 degree Celsius incubator for five minutes to warm up, then eject the utility plate after the calibration is complete. Replace it with the islet capture plate containing retinal punches and resume the assay run by clicking the load cell plate button. After the run is complete, eject the sensor cartridge and islet capture plate containing retinal punches by clicking eject button, then click the done button so that the data is automatically saved as a ASYR file and screen change automatically to result display.The mitochondrial stress assay showing an OCR trace and glycolytic rate assay showing both OCR and ECAR trace were performed using freshly dissected one millimeter retinal punch discs. In the mitochondrial stress assay, Bam15 was injected to uncouple proton gradient from mitochondrial ATP production, resulting in the increase of OCR to maximal level. Rotenone and antimycin A were injected to inhibit mitochondria respiration at complex one and complex three respectively, resulting in a drop in the OCR to the minimal level.The difference between the maximal level of OCR and the last measurement of the basal OCR level reflects mitochondrial reserve capacity. In the glycolytic rate assay, injection of rotenone and antimycin A shuts down mitochondrial respiration and drives glycolysis higher. Glycolysis is seized by injecting 2-deoxy-d-glucose, which competes with glucose for hexokinase binding, causing the ECAR to drop to the minimal level.The difference between the maximal level of glyco ECAR in the last measure of glyco ECAR basal level reflects the glycolysis reserve capacity. To produce reliable data, it's critical to obtain good quality of retinal punch discs and to limit the total dissecting time within 1.5 hour. Following the experiment, one can quantify the DNA of protein content of a retinal disc in a well and use that to normalize the seahorse data.So this protocol was utilized to study development, aging, and disease in the retina. Tissue preference or reliance for different fuel substrates such as glucose or fatty acids was also analyzed.

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