The authors wish to acknowledge Dr. Paul Witting and Ms. Genevieve Fong for their assistance with mRNA extraction and PCR, and the Garnett Passe and Rodney Williams Memorial Foundation for support.

Ethics Statement: All procedures outlined below were approved by the University of Sydney Animal Ethics Committee.
1. Animals
NOTE: 1 and 8 - 9 month old mice (C57/BL6) were obtained from the Animal Resources Centre (Perth, Australia). Mice were housed in the Bosch Rodent Facility at the University of Sydney.
<ol>
	<li>House mice in standard mouse cages on a 12/12 hr light/dark cycle with access to food and water ad libitum.</li>
	<li>Divide mice in each age group into near infrared (NIr) treated, or sham treated (control) groups for comparison.</li>
</ol>
2. Near Infrared (NIr) Irradiation and Sham Treatment
<ol>
	<li>Shave the fur on the head and neck region of the mouse with an electric razor as closely as possible to prevent quick regrowth of hair before the completion of the treatment regime. In order to maintain the pathogen-free status of the mice, use 70% ethanol to clean instruments between shaving animals and F10 veterinary disinfectant between animals from separate cages. Do this 2 - 3 days prior to the beginning of treatment so animals are not over-handled.</li>
	<li>Restrain mouse by holding the proximal end of the tail and allow it to relax in the palm of one hand or bench top so as to minimize stress which could lead to false results.</li>
	<li>Hold the NIr (670 nm) LED (light emitting diode) device 1 - 2 cm away from the exposed (shaved) area and switch on the device for 90 sec (Figure 1A). 
	NOTE: The temperature change as a result of 90 sec exposure was measured as &#60;0.2 &#176;C in 100 ml of water.</li>
	<li>Repeat steps 2.2 - 2.3 for the sham treatment group of animals but leave the device switched off (Figure 1B).</li>
	<li>Repeat steps 2.2 - 2.3 for the NIr-blocked treatment group of animals but cover the device with aluminium foil.</li>
	<li>Repeat steps 2.2 - 2.5&#160;daily at approximate 24 hr intervals for 5 consecutive days.</li>
	<li>Extract the vestibular sensory epithelium (3 cristae and 1 utricular macula) from both ears on the fifth day post-treatment (See Section 3 below).</li>
</ol>
3. Tissue Extraction20
<ol>
	<li>Prepare 300 ml of a glycerol-based artificial cerebrospinal fluid (ACSF) consisting of (in mM): 26 NaHCO3, 11 glucose, 250 glycerol, 2.5 KCl, 1.2 NaH2PO4, 1.2 MgCl2, and 2.5 CaCl2. Prior to the addition of CaCl2, gas the solution with carbogen (95% O2 and 5% CO2) to establish a pH of 7.4 and avoid calcium precipitation (cloudiness). Chill the solution in a -80 &#176;C freezer for 45 min so that an ice slurry is formed.</li>
	<li>Prepare the RNA isolation lysis buffer in labelled screw top microtubes (stops the popping of lids when tube pressure changes between freeze and thawing in liquid nitrogen) according to the instructions of the manufacturer or usual lab practices. Have liquid nitrogen ready in an aluminium dewar flask. 
	NOTE: Use protective clothing and eyeware when handling liquid nitrogen. Ensure that liquid nitrogen is used in a well-ventilated room as the volume of its gas form is approximately 700 times that of its liquid form and can cause asphyxiation.</li>
	<li>Deeply anaesthetize mice with ketamine (400 mg/kg) via an intra-peritoneal injection. Allow the hind-limb reflex to completely subside as indication that mice are fully anaesthetised.</li>
	<li>Decapitate mice with sharp stainless steel scissors and make an incision along the sagittal skin of the skull using a razor blade (rounded #22). At this point and throughout steps 3.5 - 3.9, keep the cranial vault, brain, and underlying vestibular apparatus as cool as possible by regular application of ice-cold ACSF over the tissue.</li>
	<li>Using the pointed arm of standard pattern scissors make a small incision in the skull at Lambda and cut along the sagittal suture.</li>
	<li>Gently slide one arm of a shallow rongeurs beneath the parietal bone keeping the blade as close as possible to the inferior surface of the bone without dragging the brain. Secure and pull away the parietal bone laterally and the occipital bone posteriorly until the brain is exposed.</li>
	<li>Use a small stainless steel spatula and lift the brain away from the anterior and middle cranial fossa to expose the vestibulocochlear nerve (CN VIII). Transect the nerve to prevent unnecessary tension on the primary afferent axons that directly innervate the vestibular hair cells.</li>
	<li>Remove the brain in toto after transection of CN VIII.</li>
	<li>Observe the bony labyrinth containing the cochlea and the peripheral vestibular organs in the middle cranial fossa. Make two small incisions beside each bony labyrinth and excise the entire structure by holding the anterior semicircular canal and pulling laterally.</li>
	<li>Immediately immerse excised labyrinths in a dissecting dish containing ice-cold ACSF solution (as described in step 3.1) while continuously perfusing with carbogen.</li>
	<li>Under a stereomicroscope, hold down the labyrinth by the cochlea and secure it to the bottom of the dish with forceps.
	<ol>
		<li>Use straight fine forceps to scratch a small opening in the bone above the anterior semicircular canal (SSC) ampulla.</li>
		<li>Gently enlarge this opening by reaching immediately below the bone and flicking outwards away from the ampulla. Exercise caution here to not push forceps into the opening and damage the fragile membranous labyrinth below. Continue in this fashion until the utricle, anterior and lateral ampullae are all exposed. If possible remove the posterior ampulla also.</li>
	</ol>
	</li>
	<li>Using fine forceps, gently lift the utricle and ampullae away from the bony labyrinth until they are completely detached. Where possible, hold them by their associated semicircular canals to avoid damaging the sensory epithelium. In some cases, the proximal part of the semicircular membranous duct may need to be cut with iris scissors to release the ampullae from the bone.</li>
	<li>Securely grasp the vestibular organs between the tip of forceps and place into the lysis buffer prepared earlier in step 3.2. Gently swirl the forceps around in the buffer to ensure vestibular organs have detached from the forceps. Check this is the case by bringing the forceps under the stereomicroscope.
	<ol>
		<li>Screw on the microtubule lid and freeze the sample in liquid nitrogen immediately.</li>
	</ol>
	</li>
</ol>
4. RNA Extraction and RT-PCR

<ol>
	<li>Follow standard methods of messenger RNA (mRNA) extraction according to manufacturer&#8217;s instructions or preferred lab protocols. 
	NOTE: A commercial kit that utilized carrier RNAs to help isolate small yields of mRNA was used in this protocol. Lower elution volumes can be used to increase final concentrations of mRNA. 
	NOTE: Negative &#8220;no enzyme&#8221; controls (NECs) and &#8220;no DNA template&#8221; controls (NTCs) must also be completed to ensure validity of observed effects.</li>
	<li>Apply standard methods of reverse transcription of mRNA to complementary DNA (cDNA) and amplification of target genes21-23.</li>
</ol>

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The authors declare they have no competing financial interests.

The representative results described here show that brief transcranial delivery of NIr light (90 sec/day for 5 days) is sufficient to raise the levels of antioxidant expression in older mice when compared with sham-treated mice. While emitted heat could represent a source of mitochondrial and/or neuronal activation, as reported for rat vestibular afferents24 &#8211; our measurement of heat emitted by the NIr LED device was &#60;0.2&#176;C over 90 sec, and as such is unlikely to cause the changes described here...

Declining balance performance and subsequent falls are common, and unfortunately often defining features of natural aging1. The impact of this decline can be both physical and social, and significantly reduces quality of life for older people. In response, physical therapies and rehabilitation have been the focus of research into falls but have not been associated with consistent reduction in the prevalence of repeated falls. At the same time, work investigating changes in the peripheral or central vestibular system (the system responsible for maintain balance) is scarce, and potential therapeutic strategies targeting these systems and the underlying causes of imbalance limited.
Recent work on age-associated neurodegenerative disorders including age-related macular degeneration2-4, Alzheimer&#8217;s disease models5-8, and Parkinson&#8217;s disease9-12 have shown neuroprotective effects of simple non-invasive application of near infrared (NIr) light. Further, in the vestibular system, NIr has been used to increase the activity of vestibular primary afferent neurons in vitro13. While the mechanism of NIr light is not well-understood, most studies using NIr have suggested that NIr stimulates mitochondria complex IV (cytochrome c oxidase)14-17 to facilitate cellular metabolism. In the vestibular sensory epithelium the subcuticular plate of type I hair cells is dense in mitochondria18 and as such may represent a site of action for therapeutic NIr treatment.
Here, a brief, non-invasive treatment regime of transcranially applied NIr that can be used to measure cellular metabolism (and by implication, mitochondrial function) in the mouse vestibular sensory epithelium is described. Also discussed is a preparation of the vestibular sensory epithelium and it is shown that NIr increases the expression of a ubiquitous anti-oxidant (superoxide dismutase 1) in the sensory epithelium &#8211; previously shown to be important for cochlea hair cell survival19.

<table><tbody><tr><td>Quantum WARP 10</td><td>Quantum Devices</td><td>2070N030-A</td><td></td></tr><tr><td>Screw top microtubules</td><td>Quality Scientific Plastics</td><td>520-GRD-Q</td><td></td></tr><tr><td>Ketamine</td><td>Parnell, Alexandria Australia</td><td></td><td></td></tr><tr><td>Standard pattern scissors</td><td>FST</td><td>14001-12</td><td></td></tr><tr><td>Carbon steel surgical blades #22</td><td>Livingstone</td><td>SBLDCL 22</td><td></td></tr><tr><td>Friedman-Pearson rongeurs</td><td>FST</td><td>16221-14</td><td></td></tr><tr><td>Stereo microscope</td><td>Leica Microsystems</td><td>A60S</td><td></td></tr><tr><td>Dumont #5 SF forceps</td><td>FST</td><td>11252-00</td><td></td></tr><tr><td>Isolate II RNA Micro Kit</td><td>Bioline</td><td>BIO-52075</td><td></td></tr></tbody></table>

near infrared (nir) light increases expression of a marker of mitochondrial function in the mouse vestibular sensory epithelium

Strategies for attenuating decline in balance function with increasing age are predominantly focused on physical therapies including balance tasks and exercise. However, these approaches do not address the underlying causes of balance decline. Using mice, the impact of near infrared light (NIr) on the metabolism of cells in the vestibular sensory epithelium was assessed. Data collected shows that this simple and safe intervention may protect these vulnerable cells from the deleterious effects of natural aging. mRNA was extracted from the isolated peripheral vestibular sensory epithelium (crista ampullaris and utricular macula) and subsequently transcribed into a cDNA library. This library was then probed for the expression of ubiquitous antioxidant (SOD-1). Antioxidant gene expression was then used to quantify cellular metabolism. Using transcranial delivery of NIr in young (4 weeks) and older (8 - 9 months) mice, and a brief treatment regime (90 sec/day for 5 days), this work suggests NIr alone may be sufficient to improve mitochondrial function in the vestibular sensory epithelium. Since there are currently no available, affordable, non-invasive methods of therapy to improve vestibular hair cell function, the application of external NIr radiation provides a potential strategy to counteract the impact of aging on cellular metabolism inthe vestibular sensory epithelium.

To compare the impact of NIr treatment in young (4 weeks) and older (8 - 9 months) mice we measured the expression of antioxidant superoxide dismutase 1 (SOD-1) in young (n = 16) and older (n = 20) mice that were NIr-treated, sham-treated, or NIr-blocked. Figure 2 shows a significant increase in &#946;-actin normalized SOD-1 expression of more than 2-fold in young NIr-treated animals compared to young sham-treated animals (p &#60; 0.01) and young NIr-blocked animals (p &#60; 0.01). Older NIr-treated anim...

Watch this Scientific Journal Video about Near Infrared NIr Light Increases Expression of a Marker of Mitochondrial Function in the Mouse Vestibular Sensory Epithelium at JoVE.com

Near Infrared NIr Light Increases Expression of a Marker of Mitochondrial Function in the Mouse Vestibular Sensory Epithelium

Mitochondrial dysfunction is a hallmark of cellular senescence. This paper uses non-invasive near-infrared (NIr) treatment to improve mitochondrial function in the aging mouse vestibular sensory epithelium.

Near Infrared (NIr) Light Increases Expression of a Marker of Mitochondrial Function in the Mouse Vestibular Sensory Epithelium

Strategies for attenuating decline in balance function with increasing age are predominantly focused on physical therapies including balance tasks and ...

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JoVE Journal

Biology

9.9K Views.  University of Sydney.  Mitochondriale dysfunctie is een kenmerk van cellulaire veroudering. Dit artikel maakt gebruik van niet-invasieve nabij-infrarood (NIR) behandeling om de mitochondriale functie in het verouderingsproces muis vestibulair sensorische epitheel verbeteren. 

Video: Near Infrared NIr Light Increases Expression of a Marker of Mitochondrial Function in the Mouse Vestibular Sensory Epithelium

An Isolated Semi-intact Preparation of the Mouse Vestibular Sensory Epithelium for Electrophysiology and High-resolution Two-photon Microscopy

Understanding vestibular hair cells function under normal conditions, or how trauma, disease, and aging disrupt this function is a vital step in the development of preventative approaches and/or novel therapeutic strategies. However, the majority of studies looking at abnormal vestibular function have not been at the cellular level but focused primarily on behavioral assays of vestibular dysfunction such as gait analyses and vestibulo-ocular reflex performance. While this work has yielded valuable data about what happens when things go wrong, little information is gleaned regarding the underlying causes of dysfunction. Of the studies that focus on the cellular and subcellular processes that underlie vestibular function, most have relied on acutely isolated hair cells, devoid of their synaptic connections and supporting cell environment. Therefore, a major technical challenge has been access to the exquisitely sensitive vestibular hair cells in a preparation that is least disrupted, physiologically. Here we demonstrate a semi-intact preparation of the mouse vestibular sensory epithelium that retains the local micro-environment including hair cell/primary afferent complexes.

Analysis of vestibular hair cell function is complicated by their location deep within the hardest part of the skull, the petrous temporal bone. Most functional hair cell studies have used acutely isolated hair cells. Here we describe a semi-intact preparation of mouse vestibular epithelium for electrophysiological and two-photon microscopy studies.

Understanding vestibular hair cells function  under normal conditions, or how trauma, disease, and aging disrupt this  function is a vital step in the ...

Neuroscience

In vivo Imaging of Optic Nerve Fiber Integrity by Contrast-Enhanced MRI in Mice

The rodent visual system encompasses retinal ganglion cells and their axons that form the optic nerve to enter thalamic and midbrain centers, and postsynaptic projections to the visual cortex. Based on its distinct anatomical structure and convenient accessibility, it has become the favored structure for studies on neuronal survival, axonal regeneration, and synaptic plasticity. Recent advancements in MR imaging have enabled the in vivo visualization of the retino-tectal part of this projection using manganese mediated contrast enhancement (MEMRI). Here, we present a MEMRI protocol for illustration of the visual projection in mice, by which resolutions of (200 &#181;m)3 can be achieved using common 3 Tesla scanners. We demonstrate how intravitreal injection of a single dosage of 15 nmol MnCl2 leads to a saturated enhancement of the intact projection within 24 hr. With exception of the retina, changes in signal intensity are independent of coincided visual stimulation or physiological aging. We further apply this technique to longitudinally monitor axonal degeneration in response to acute optic nerve injury, a paradigm by which Mn2+ transport completely arrests at the lesion site. Conversely, active Mn2+ transport is quantitatively proportionate to the viability, number, and electrical activity of axon fibers. For such an analysis, we exemplify Mn2+ transport kinetics along the visual path in a transgenic mouse model (NF-&#954;B p50KO) displaying spontaneous atrophy of sensory, including visual, projections. In these mice, MEMRI indicates reduced but not delayed Mn2+ transport as compared to wild type mice, thus revealing signs of structural and/or functional impairments by NF-&#954;B mutations.
In summary, MEMRI conveniently bridges in vivo assays and post mortem histology for the characterization of nerve fiber integrity and activity. It is highly useful for longitudinal studies on axonal degeneration and regeneration, and investigations of mutant mice for genuine or inducible phenotypes.

In vivo Imaging of Optic Nerve Fiber Integrity by Contrast-Enhanced MRI in Mice

This video illustrates a method, using a clinical 3 T scanner, for contrast-enhanced MR imaging of the na&#239;ve mouse visual projection and for repetitive and longitudinal in vivo studies of optic nerve degeneration associated with acute optic nerve crush injury and chronic optic nerve degeneration in knock-out mice (p50KO).

The rodent visual system encompasses retinal ganglion cells and their axons that form the optic nerve to enter thalamic and midbrain centers, and ...

Assessing Mitochondrial Function in Sciatic Nerve by High-Resolution Respirometry

Mitochondrial dysfunction in peripheral nerves accompanies several diseases associated with peripheral neuropathy, which can be triggered by multiple causes, including autoimmune diseases, diabetes, infections, inherited disorders, and tumors. Assessing mitochondrial function in mouse peripheral nerves can be challenging due to the small sample size, a limited number of mitochondria present in the tissue, and the presence of a myelin sheath. The technique described in this work minimizes these challenges by using a unique permeabilization protocol adapted from one used for muscle fibers, to assess sciatic nerve mitochondrial function instead of isolating the mitochondria from the tissue. By measuring fluorimetric reactive species production with Amplex Red/Peroxidase and comparing different mitochondrial substrates and inhibitors in saponin-permeabilized nerves, it was possible to detect mitochondrial respiratory states, reactive oxygen species (ROS), and the activity of mitochondrial complexes simultaneously. Therefore, the method presented here offers advantages compared to the assessment of mitochondrial function by other techniques.

High-resolution respirometry coupled to fluorescence sensors determines mitochondrial oxygen consumption and reactive oxygen species (ROS) generation. The present protocol describes a technique to assess mitochondrial respiratory rates and ROS production in the permeabilized sciatic nerve.

Mitochondrial dysfunction in peripheral nerves accompanies several diseases associated with peripheral neuropathy, which can be triggered by multiple ...

Biochemistry

In Vitro and In Vivo Detection of Mitophagy in Human Cells, C. Elegans, and Mice

Mitochondria are the powerhouses of cells and produce cellular energy in the form of ATP. Mitochondrial dysfunction contributes to biological aging and a wide variety of disorders including metabolic diseases, premature aging syndromes, and neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Maintenance of mitochondrial health depends on mitochondrial biogenesis and the efficient clearance of dysfunctional mitochondria through mitophagy. Experimental methods to accurately detect autophagy/mitophagy, especially in animal models, have been challenging to develop. Recent progress towards the understanding of the molecular mechanisms of mitophagy has enabled the development of novel mitophagy detection techniques. Here, we introduce several versatile techniques to monitor mitophagy in human cells, Caenorhabditis elegans (e.g., Rosella and DCT-1/ LGG-1 strains), and mice (mt-Keima). A combination of these mitophagy detection techniques, including cross-species evaluation, will improve the accuracy of mitophagy measurements and lead to a better understanding of the role of mitophagy in health and disease.

In Vitro and In Vivo Detection of Mitophagy in Human Cells, C. Elegans, and Mice

Mitophagy, the process of clearing damaged mitochondria, is necessary for mitochondrial homeostasis and health maintenance. This article presents some of the latest mitophagy detection methods in human cells, Caenorhabditis elegans, and mice.

Mitochondria are the powerhouses of cells and produce cellular energy in the form of ATP. Mitochondrial dysfunction contributes to biological aging and a ...

Medicine

A Protocol for Transcranial Photobiomodulation Therapy in Mice

Transcranial photobiomodulation is a potential innovative noninvasive therapeutic approach for improving brain bioenergetics, brain function in a wide range of neurological and psychiatric disorders, and memory enhancement in age-related cognitive decline and neurodegenerative diseases. We describe a laboratory protocol for transcranial photobiomodulation therapy (PBMT) in mice. Aged BALB/c mice (18 months old) are treated with a 660 nm laser transcranially, once daily for 2 weeks. Laser transmittance data shows that approximately 1% of the incident red light on the scalp reaches a 1 mm depth from the cortical surface, penetrating the dorsal hippocampus. Treatment outcomes are assessed by two methods: a Barnes maze test, which is a hippocampus-dependent spatial learning and memory task evaluation, and measuring hippocampal ATP levels, which is used as a bioenergetics index. The results from the Barnes task show an enhancement of the spatial memory in laser-treated aged mice when compared with age-matched controls. Biochemical analysis after laser treatment indicates increased hippocampal ATP levels. We postulate that the enhancement of memory performance is potentially due to an improvement in hippocampal energy metabolism induced by the red laser treatment. The observations in mice could be extended to other animal models since this protocol could potentially be adapted to other species frequently used in translational neuroscience, such as rabbit, cat, dog, or monkey. Transcranial photobiomodulation is a safe and cost-effective modality which may be a promising therapeutic approach in age-related cognitive impairment.

Photobiomodulation therapy is an innovative noninvasive modality for the treatment of a wide range of neurological and psychiatric disorders and can also improve healthy brain function. This protocol includes a step-by-step guide to performing brain photobiomodulation in mice by transcranial light delivery, which can be adapted for use in other laboratory rodents.

Transcranial photobiomodulation is a potential innovative noninvasive therapeutic approach for improving brain bioenergetics, brain function in a wide ...

Method for the Assessment of Effects of a Range of Wavelengths and Intensities of Red/near-infrared Light Therapy on Oxidative Stress In Vitro

Red/near-infrared light therapy (R/NIR-LT), delivered by laser or light emitting diode (LED), improves functional and morphological outcomes in a range of central nervous system injuries in vivo, possibly by reducing oxidative stress. However, effects of R/NIR-LT on oxidative stress have been shown to vary depending on wavelength or intensity of irradiation. Studies comparing treatment parameters are lacking, due to absence of commercially available devices that deliver multiple wavelengths or intensities, suitable for high through-put in vitro optimization studies. This protocol describes a technique for delivery of light at a range of wavelengths and intensities to optimize therapeutic doses required for a given injury model. We hypothesized that a method of delivering light, in which wavelength and intensity parameters could easily be altered, could facilitate determination of an optimal dose of R/NIR-LT for reducing reactive oxygen species (ROS) in vitro.
Non-coherent Xenon light was filtered through narrow-band interference filters to deliver varying wavelengths (center wavelengths of 440, 550, 670 and 810nm) and fluences (8.5 x 10-3 to 3.8 x 10-1 J/cm2) of light to cultured cells. Light output from the apparatus was calibrated to emit therapeutically relevant, equal quantal doses of light at each wavelength. Reactive species were detected in glutamate stressed cells treated with the light, using DCFH-DA and H2O2 sensitive fluorescent dyes.&#160;
We successfully delivered light at a range of physiologically and therapeutically relevant wavelengths and intensities, to cultured cells exposed to glutamate as a model of CNS injury. While the fluences of R/NIR-LT used in the current study did not exert an effect on ROS generated by the cultured cells, the method of light delivery is applicable to other systems including isolated mitochondria or more physiologically relevant organotypic slice culture models, and could be used to assess effects on a range of outcome measures of oxidative metabolism.

Method for the Assessment of Effects of a Range of Wavelengths and Intensities of Red/near-infrared Light Therapy on Oxidative Stress In Vitro

Non-coherent Xenon light was passed through narrow-band interference and neutral density filters to deliver light of varying wavelength and intensity to cultured cells. This protocol was used to assess the effects of red/near-infrared light therapy on production of reactive species in vitro: no effects were observed using the tested parameters.

Red/near-infrared light therapy (R/NIR-LT), delivered by laser or light emitting diode (LED), improves functional and morphological outcomes in a range of ...

A Screenable In Vivo Assay for Mitochondrial Modulators Using Transgenic Bioluminescent Caenorhabditis elegans

The multicellular model organism Caenorhabditis elegans is a small nematode of approximately 1 mm in size in adulthood that is genetically and experimentally tractable. It is economical and easy to culture and dispense in liquid medium which makes it well suited for medium-throughput screening. We have previously validated the use of transgenic luciferase expressing C. elegans strains to provide rapid in vivo assessment of the nematode&#8217;s ATP levels.1-3 Here we present the required materials and procedure to carry out bioassays with the bioluminescent C. elegans strains PE254 or PE255 (or any of their derivative strains). The protocol allows for in vivo detection of sublethal effects of drugs that may identify mitochondrial toxicity, as well as for in vivo detection of potential beneficial drug effects. Representative results are provided for the chemicals paraquat, rotenone, oxaloacetate and for four firefly luciferase inhibitory compounds. The methodology can be scaled up to provide a platform for screening drug libraries for compounds capable of modulating mitochondrial function. Pre-clinical evaluation of drug toxicity is often carried out on immortalized cancerous human cell lines which derive ATP mostly from glycolysis and are often tolerant of mitochondrial toxicants.4,5 In contrast, C. elegans depends on oxidative phosphorylation to sustain development into adulthood, drawing a parallel with humans and providing a unique opportunity for compound evaluation in the physiological context of a whole live multicellular organism.

A Screenable In Vivo Assay for Mitochondrial Modulators Using Transgenic Bioluminescent Caenorhabditis elegans

A protocol is described for in vivo detection of effects of mitochondrial inhibitors in the model organism Caenorhabditis elegans and for identification of potential enhancing compounds. This protocol can be used to screen drug libraries for compounds modulating mitochondrial function.

The multicellular model organism Caenorhabditis elegans is a small nematode of approximately 1 mm in size in adulthood that is genetically and ...

Time-Lapse Video Microscopy for Assessment of EYFP-Parkin Aggregation as a Marker for Cellular Mitophagy

Time-lapse video microscopy can be defined as the real time imaging of living cells. This technique relies on the collection of images at different time points. Time intervals can be set through a computer interface that controls the microscope-integrated camera. This kind of microscopy requires both the ability to acquire very rapid events and the signal generated by the observed cellular structure during these events. After the images have been collected, a movie of the entire experiment is assembled to show the dynamic of the molecular events of interest. Time-lapse video microscopy has a broad range of applications in the biomedical research field and is a powerful and unique tool for following the dynamics of the cellular events in real time. Through this technique, we can assess cellular events such as migration, division, signal transduction, growth, and death. Moreover, using fluorescent molecular probes we are able to mark specific molecules, such as DNA, RNA or proteins and follow them through their molecular pathways and functions. Time-lapse video microscopy has multiple advantages, the major one being the ability to collect data at the single-cell level, that make it a unique technology for investigation in the field of cell biology. However, time-lapse video microscopy has limitations that can interfere with the acquisition of high quality images. Images can be compromised by both external factors; temperature fluctuations, vibrations, humidity and internal factors; pH, cell motility. Herein, we describe a protocol for the dynamic acquisition of a specific protein, Parkin, fused with the enhanced yellow fluorescent protein (EYFP) in order to track the selective removal of damaged mitochondria, using a time-lapse video microscopy approach.

Herein, we describe in detail a time-lapse video microscopy approach to measuring the temporal recruitment of EYFP-Parkin during the selective removal of damaged mitochondria. This dynamic process of EYFP-Parkin-dependent removal of damaged mitochondria can be used as an indicator of cellular health under different experimental conditions.

Time-lapse video microscopy can be defined as the real time imaging of living cells. This technique relies on the collection of images at different time ...

MATLAB Optimization for Analyzing Mitochondrial Networks in Neuroscience

Optimized Automated Analysis of Live Neuronal Mitochondria Homeostasis Modulation by Isoform-Specific Retinoic Acid Receptors

The complex mitochondrial network makes it very challenging to segment, follow, and analyze live cells. MATLAB tools allow the analysis of mitochondria in timelapse files, considerably simplifying and speeding up the process of image processing. Nonetheless, existing tools produce a large output volume, requiring individual manual attention, and basic experimental setups have an output of thousands of files, each requiring extensive and time-consuming handling. 
To address these issues, a routine optimization was developed, in both MATLAB code and live-script forms, allowing for swift file analysis and significantly reducing document reading and data processing. With a speed of 100 files/min, the optimization allows an overall rapid analysis. The optimization achieves the results output by averaging frame-specific data for individual mitochondria throughout time frames, analyzing data in a defined manner, consistent with those output from existing tools. Live confocal imaging was performed using the dye tetramethylrhodamine methyl ester, and the routine optimization was validated by treating neuronal cells with retinoic acid receptor (RAR) agonists, whose effects on neuronal mitochondria are established in the literature. The results were consistent with the literature and allowed further characterization of mitochondrial network behavior in response to isoform-specific RAR modulation. 
This new methodology allowed rapid and validated characterization of whole-neuron mitochondria network, but it also allows for differentiation between axon and cell body mitochondria, an essential feature to apply in the neuroscience field. Moreover, this protocol can be applied to experiments using fast-acting treatments, allowing the imaging of the same cells before and after treatments, transcending the field of neuroscience.

Author Spotlight: An Optimized Automated Method for Investigating Retinoic Acid Receptors in Neuronal Mitochondria

The mitochondrial network is extremely complex, making it very challenging to analyze. A novel MATLAB tool analyzes live confocal imaged mitochondria in timelapse images but results in a large output volume requiring individual manual attention. To address this issue, a routine optimization was developed, allowing for speedy file analysis.

The complex mitochondrial network makes it very challenging to segment, follow, and analyze live cells. MATLAB tools allow the analysis of mitochondria in ...

Measurement of Energy Metabolism in Explanted Retinal Tissue Using Extracellular Flux Analysis

High acuity vision is a heavily energy-consuming process, and the retina has developed several unique adaptations to precisely meet such demands while maintaining transparency of the visual axis. Perturbations to this delicate balance cause blinding illnesses, such as diabetic retinopathy. Therefore, the understanding of energy metabolism changes in the retina during disease is imperative to the development of rational therapies for various causes of vison loss. The recent advent of commercially-available extracellular flux analyzers has made the study of retinal energy metabolism more accessible. This protocol describes the use of such an analyzer to measure contributions to retinal energy supply through its two principle arms - oxidative phosphorylation and glycolysis - by quantifying changes in oxygen consumption rates (OCR) and extracellular acidification rates (ECAR) as proxies for these pathways. This technique is readily performed in explanted retinal tissue, facilitating assessment of responses to multiple pharmacologic agents in a single experiment. Metabolic signatures in retinas from animals lacking rod photoreceptor signaling are compared to wild-type controls using this method. A major limitation in this technique is the lack of ability to discriminate between light-adapted and dark-adapted energy utilization, an important physiologic consideration in retinal tissue.

This technique describes real time recording of oxygen consumption and extracellular acidification rates in explanted mouse retinal tissues using an extracellular flux analyzer.

High acuity vision is a heavily energy-consuming process, and the retina has developed several unique adaptations to precisely meet such demands while ...

Near Infrared (NIr) Light Increases Expression of a Marker of Mitochondrial Function in the Mouse Vestibular Sensory Epithelium

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