Name: measurement of strial blood flow in mouse cochlea utilizing an open vessel-window and intravital fluorescence microscopy
Uploaded: 2021-09-21T13:30:00
Description: Watch this Scientific Journal Video about Measurement of Strial Blood Flow in Mouse Cochlea Utilizing an Open Vessel-Window and Intravital Fluorescence Microscopy at JoVE.com

This research was supported by NIH/NIDCD R21 DC016157 (X.Shi), NIH/NIDCD R01 DC015781 (X.Shi), NIH/NIDCD R01-DC010844 (X.Shi),&#160;and Medical Research Foundation from Oregon Health and Science University (OHSU) (X.Shi).

NOTE: This is a non-survival surgery. All procedures involving the use of animals were reviewed and approved by the Institutional Animal Care and Use Committee at Oregon Health &#38; Science University (IACUC approval number: TR01_IP00000968).
1. Preparation of the fluorescent-labeled blood cells
<ol>
	<li>Anesthetize the donor mice (male C57BL/6J mice aged ~6 weeks) with an intraperitoneal (i.p.) injection of ketamine/xylazine anesthetic solution (5 mL/kg, see the Table of Materials...

<ol>
	<li>Shi, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiopathology+of+the+cochlear+microcirculation.">Physiopathology of the cochlear microcirculation.</a> Hearing Research. 282 (1), 10-24 (2011).</li><li>Brown, J. N., Miller, J. M., Nuttall, A. L. <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+changes+in+cochlear+vascular+conductance+in+mice.">Age-related changes in cochlear vascular conductance in mice.</a> Hearing Research. 86 (1), 189-194 (1995).</li><li>Gratton, M. A., Schmiedt, R. A., Schulte, B. A. <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+decreases+in+endocochlear+potential+are+associated+with+vascular+abnormalities+in+the+stria+vascularis+[corrected+and+republished+article+originallly+printed+in+Hearing+Research.">Age-related decreases in endocochlear potential are associated with vascular abnormalities in the stria vascularis [corrected and republished article originallly printed in Hearing Research.</a> Hearing Research. 94 (1-2), 181-190 (1996).</li><li>Le Prell, C. G., Yamashita, D., Minami, S. B., Yamasoba, T., Miller, J. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+blood-flow+in+the+mouse+cochlea+using+an+endoscopic+laser+speckle+contrast+imaging+system.">Monitoring blood-flow in the mouse cochlea using an endoscopic laser speckle contrast imaging system.</a> PLoS One. 13 (2), 0191978 (2018).</li><li>Angelborg, C., Hillerdal, M., Hultcrantz, E., Larsen, 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+microsphere+method+for+studies+of+inner+ear+blood+flow.">The microsphere method for studies of inner ear blood flow.</a> ORL. 50 (6), 355-362 (1988).</li><li>Choudhury, N., Chen, F., Shi, X., Nuttall, A. L., Wang, R. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Volumetric+imaging+of+blood+flow+within+cochlea+in+gerbil+in+vivo.">Volumetric imaging of blood flow within cochlea in gerbil in vivo.</a> IEEE Journal of Selected Topics in Quantum Electronics. 16 (3), 524-529 (2010).</li><li>Subhash, H. 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=Volumetric+in+vivo+imaging+of+microvascular+perfusion+within+the+intact+cochlea+in+mice+using+ultra-high+sensitive+optical+microangiography.">Volumetric in vivo imaging of microvascular perfusion within the intact cochlea in mice using ultra-high sensitive optical microangiography.</a> IEEE Transactions on Medical Imaging. 30 (2), 224-230 (2011).</li><li>Reif, R., 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=Monitoring+hypoxia+induced+changes+in+cochlear+blood+flow+and+hemoglobin+concentration+using+a+combined+dual-wavelength+laser+speckle+contrast+imaging+and+Doppler+optical+microangiography+system.">Monitoring hypoxia induced changes in cochlear blood flow and hemoglobin concentration using a combined dual-wavelength laser speckle contrast imaging and Doppler optical microangiography system.</a> PLoS One. 7 (12), 52041 (2012).</li><li>Nuttall, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Techniques+for+the+observation+and+measurement+of+red+blood+cell+velocity+in+vessels+of+the+guinea+pig+cochlea.">Techniques for the observation and measurement of red blood cell velocity in vessels of the guinea pig cochlea.</a> Hearing Research. 27 (2), 111-119 (1987).</li><li>Nuttall, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cochlear+blood+flow:+measurement+techniques.">Cochlear blood flow: measurement techniques.</a> American Journal of Otolaryngology. 9 (6), 291-301 (1988).</li><li>Hanna, G., 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=Automated+measurement+of+blood+flow+velocity+and+direction+and+hemoglobin+oxygen+saturation+in+the+rat+lung+using+intravital+microscopy.">Automated measurement of blood flow velocity and direction and hemoglobin oxygen saturation in the rat lung using intravital microscopy.</a> American Journal of Physiology. Lung Cellular Molecular Physiology. 304 (2), 86-91 (2013).</li><li>Narciso, M. G., Nasimuzzaman, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purification+of+platelets+from+mouse+blood.">Purification of platelets from mouse blood.</a> Journal of Visualized Experiments. (147), e59803 (2019).</li><li>Shi, 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=Thin+and+open+vessel+windows+for+intra-vital+fluorescence+imaging+of+murine+cochlear+blood+flow.">Thin and open vessel windows for intra-vital fluorescence imaging of murine cochlear blood flow.</a> Hearing Research. 313, 38-46 (2014).</li><li>Lorenz, J. 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This paper demonstrates how capillaries in the cochlear lateral wall (and in the stria vascularis) of a mouse model can be visualized with fluorophore labeling in an open vessel-window preparation under a FIVM system. Mouse model is widely used and preferred as a mammalian model for investigating&#160; human health and disease. The protocol described here is a feasible approach for imaging and investigating CoBF in the mouse lateral wall (particularly in the stria vascularis) using an open vessel-window under FIVM system...

Normal function of the microcirculation in the lateral cochlear wall (comprising the majority of the capillaries in the spiral ligament and stria vascularis) is critically important for maintaining hearing function1. Abnormal CoBF is implicated in the pathophysiology of many inner ear disorders including noise-induced hearing loss, ear hydrops, and presbycusis2,3,4,5,6,7,8,9.&#160;Visualization of intravital CoBF will enable a better understanding of the links between hearing function and cochlear vascular pathology.
Although the complexity and location of the cochlea within the temporal bone precludes direct visualization and measurement of CoBF, various methods have been developed for the assessment of CoBF including laser-doppler flowmetry (LDF)10,11,12, magnetic resonance imaging (MRI)13, fluorescence intravital microscopy (FIVM)14, fluorescence microendoscopy (FME)15, endoscopic laser speckle contrast imaging (LSCI)16, and approaches based on the injection of labeled markers and radioactively tagged microspheres into the bloodstream (optical microangiography, OMAG)17,18,19,20. However, none of these methods has enabled absolute real-time tracking of changes in CoBF in vivo, with the exception of FIVM. FIVM, in combination with a vessel-window in the lateral cochlear wall, is an approach that has been used and validated in guinea pig under different experimental conditions by various laboratories14,21,22.
An FIVM method was successfully established for studying the structural and functional changes in the cochlear microcirculation in mouse using fluorescein isothiocyanate (FITC)-dextran as a contrast medium and a fluorescence dye-either DiO (3, 3&#8242;-dioctadecyloxacarbocyanine perchlorate, green) or Dil (1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine perchlorate, red)-for prelabeling blood cells, visualizing vessels, and tracking blood flow velocity. In the present study, the protocol of this method has been described for imaging and quantifying changes in CoBF in mouse under normal and pathological conditions (such as after noise exposure). This technique gives the researcher the tools needed to investigate the underlying mechanisms of CoBF related to hearing dysfunction and pathology in the stria vascularis, especially when applied in conjunction with readily available transgenic mouse models.

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		<tr>
			<td>0.9% Sodium Chloride</td>
			<td>Hospira</td>
			<td>NDC 0409-1966-02</td>
			<td>0.6 mL (for 1 mL)</td>
		</tr>
		<tr>
			<td>1,1&#8242;-Dioctadecyl-3,3,3&#8242;,3&#8242;-tetramethylindocarbocyanine perchlorate</td>
			<td>Sigma Aldrich</td>
			<td>468495</td>
			<td>20 &#181;M</td>
		</tr>
		<tr>
			<td>3,3&#8242;-Dioctadecyloxacarbocyanine perchlorateDio (3,3&#8242;-Dioctadecyloxacarbocyanine perchlorate</td>
			<td>Sigma Aldrich</td>
			<td>D4292</td>
			<td>20 &#181;M</td>
		</tr>
		<tr>
			<td>CODA Monitor system</td>
			<td>Kent scientific</td>
			<td></td>
			<td>CODA Monitor, for monitoring blood pressure and heartbeat</td>
		</tr>
		<tr>
			<td>Coverslip</td>
			<td>Fisher Scientific</td>
			<td>12-542A</td>
			<td></td>
		</tr>
		<tr>
			<td>DC Temperature Controller</td>
			<td>FHC</td>
			<td>40-90-8D</td>
			<td></td>
		</tr>
		<tr>
			<td>Fiji/ImageJ</td>
			<td>NIH</td>
			<td></td>
			<td>Measurement of vessel diameter</td>
		</tr>
		<tr>
			<td>FITC-dextran (2000 kDa)</td>
			<td>Sigma Aldrich</td>
			<td>FD2000s</td>
			<td>40 mg/mL</td>
		</tr>
		<tr>
			<td>Heparin Sodium Injection, USP MDV</td>
			<td>Mylan</td>
			<td>NDC 67457-374-12</td>
			<td>5000 USP units/mL</td>
		</tr>
		<tr>
			<td>Katathesia (100 mg/mL)</td>
			<td>Henry Schein</td>
			<td>NDC 11695-0702-1</td>
			<td>0.2 mL (for 1 mL)</td>
		</tr>
		<tr>
			<td>Microscope Objective</td>
			<td>Mitutoyo</td>
			<td>378-823-5</td>
			<td>Model: M Plan Apo NIR 10x</td>
		</tr>
		<tr>
			<td>ORCA-ER Camera</td>
			<td>Hamamatsu</td>
			<td></td>
			<td>Model: C4742-80-12AG</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Gibco</td>
			<td>2085387</td>
			<td></td>
		</tr>
		<tr>
			<td>Xyzaine (100 mg/ml, 5x diluted for use )</td>
			<td>Lloyd</td>
			<td>LPFL04821</td>
			<td>0.2 mL (for 1 mL)</td>
		</tr>
		<tr>
			<td>Zoom Stereo Microscope</td>
			<td>Olympus</td>
			<td></td>
			<td>Model: SZ61, fluorescent microscope</td>
		</tr>
	</tbody>
</table>

measurement of strial blood flow in mouse cochlea utilizing an open vessel-window and intravital fluorescence microscopy

Transduction of sound is metabolically demanding, and the normal function of the microvasculature in the lateral wall is critical for maintaining endocochlear potential, ion transport, and fluid balance. Different forms of hearing disorders are reported to involve abnormal microcirculation in the cochlea. Investigation of how cochlear blood flow (CoBF) pathology affects hearing function is challenging due to the lack of feasible interrogation methods and the difficulty in accessing the inner ear. An open vessel-window in the lateral cochlear wall, combined with fluorescence intravital microscopy, has been used for studying CoBF changes in vivo, but mostly in guinea pig and only recently in the mouse. This paper and the associated video describe the open vessel-window method for visualizing blood flow in the mouse cochlea. Details include 1) preparation of the fluorescent-labeled blood cell suspension from mice; 2) construction of an open vessel-window for intravital microscopy in an anesthetized mouse, and 3) measurement of blood flow velocity and volume using an offline recording of the imaging. The method is presented in video format to show how to use the open window approach in mouse to investigate structural and functional changes in the cochlear microcirculation under normal and pathological conditions.

After surgical exposure of the cochlear capillaries in the lateral wall (Figure 1), intravital high-resolution fluorescence microscopic observation of Dil-labeled blood cells in FITC-dextran-labeled vessels was feasible through an open vessel-window. Figure 2A is a representative image taken under FIVM that shows the capillaries of the mouse cochlear apex-middle turn lateral wall. The lumina of these vessels is made visible by th...

Watch this Scientific Journal Video about Measurement of Strial Blood Flow in Mouse Cochlea Utilizing an Open Vessel-Window and Intravital Fluorescence Microscopy at JoVE.com

Measurement of Strial Blood Flow in Mouse Cochlea Utilizing an Open Vessel-Window and Intravital Fluorescence Microscopy

An open vessel-window approach using fluorescent tracers provides sufficient resolution for cochlear blood flow (CoBF) measurement. The method facilitates the study of structural and functional changes in CoBF in mouse under normal and pathological conditions.

Transduction of sound is metabolically demanding, and the normal function of the microvasculature in the lateral wall is critical for maintaining ...

Normal blood supply to cochlea is critically important for cochlea Meniere's Disease especially for maintaining indoor cochlear potential which is the essential driving force for hair cells transaction. This function of blood circulation has been closely associated with different forms of hearing loss. Better understanding of cochlear blood flow will enable more effective management of hearing disorders resulting from blood flow dysfunction.However, direct blood flow measurement is very very challenging due to difficulty to assess the inner ear. Techniques for assessing cochlear blood flow is currently still under development. Here we demonstrate one of the recent methods established in our lab open muscle window in accommodation with high resolution fluorescence microscope to narrow cochlear blood flow in small animal species such as mouse.Application of this technique with transgenetic mass models has the potential for advancing research to unravel the links between hearing function and the pathology related to cochlear blood flow in intravascular risk. Our procedures should be conducted with caution. In addition to momentary body hemorrhage, animal's vital signs, including blood pressure and heartbeat, must be monitored during your surgery.Begin by collecting approximately one millimeter of blood in heparin by cardiac puncture. Centrifuge the blood at 3000 times G for three minutes at four degrees Celsius. Remove the plasma, then wash the blood cell pellet with one milliliter of PBS three times by centrifugation at 3000 times G for three minutes at four degrees Celsius.Label the blood cells with one milliliter of 20 micromolar DiO or Dil in PBS, and incubate in the dark for 30 minutes at room temperature. Wash the labeled blood cells with one milliliter of PBS and centrifuge three times at 3000 times G for three minutes. Resuspend the cell pellet in 30%hematocrit with approximately 0.9 milliliters of PBS before injection.Prepare sterile surgical instruments and imaging platform and place a heating pad beneath the drape. Monitor the poor reflex and general muscle tone of the anesthetized mice to check the depth of the anesthesia. Place the animal on the warm heating pad and its tail in the monitor system for monitoring blood pressure and heartbeat.Maintain the rectal temperature at 37 degrees Celsius and record the animal's systolic blood pressure, diastolic blood pressure, and mean blood pressure in the anesthetized condition. Open the left tympanic bulla via a lateral and vental approach under a stereo microscope leaving the tympanic membrane and ossicles intact. Make an incision along the midline of the animal's neck with its head immobilized to minimize movement.Remove the left sub mandibular gland and posterior belly of the digastric muscle and cauterize. Locate and expose the bony bulla by identifying the sternocleidomastoid muscle and facial nerve extending anterior toward the bulla. Open the bony bulla with a 30 gauge needle and carefully remove the surrounding bone with surgical tweezers to provide a clear view of the cochlear and stapedial artery with its medial margin lying over the edge of the round window niche and causing anterior superior towards the oval window.Use a small knife blade to scrape the lateral wall bone at the apex middle turn of the mouse cochlea approximately 1.25 millimeters from the apex until a thin spot is cracked. Remove the bone chips with small wire hooks. Cover the vessel window with a cut cover slip to preserve normal physiological conditions and provide an optical view for recording vessel images.Make a one centimeter incision along the right saphenous vein to expose the vessel. Successively infuse 100 microliters each of the FITC-Dextran solution and the blood cell suspension into the animal through the saphenous vein to enable visualization of the blood vessels and tracking of blood flow. Observe the blood flow in real time on a video monitor five minutes after the injection.Image the blood vessels using a fluorescence microscope equipped with a long working distance objective and a lamp housing containing a multiple band excitation filter and compatible emission filter. Record the video using a high resolution digital black and white charge coupled device camera acquiring more than 350 images per video. To ensure successful analysis of the flow velocity.Measure the vessel diameter using appropriate software and determine the distance between two fixed points across the vessel in the acquired images. Open the video of blood flow in the software and set the scale of the images. Track the selected DiO stained blood cells using the tracking function.Then use the distance the cells have moved and the interval of time between image frames in the video for auto calculation of the flow velocity. Calculate the volumetric flow using the equation given in the text manuscript. To create the noise exposure model before blood flow recording, place the animals in wire mesh cages and expose them to broadband noise at 120 decibels sound pressure level in a sound exposure booth for three hours.Then for an additional three hours on the next day. Record blood flow two weeks after noise exposure. After surgical exposure of the cochlear capillaries in the lateral wall, intravital high resolution fluorescence microscopic observation of DiL labeled blood cells in FITC Dextran labeled vessels was performed through an open vessel window.DiL labeled blood cells in Stria vessels labeled with FITC Dextran are shown here. Dio labeled blood cells labeled with FITC Dextran show that the vessel density of the spiral ligament is sparser than that of the denser Stria vascularis. High resolution IVM shows the blood flow patterns in control and noise exposed groups.The disturbed pattern of blood circulation can be seen in the noise exposed groups. Anomalies included reduced vessel diameter and increased variation in vessel diameter. The blood flow velocities in the control and noise exposed groups were calculated by tracking the roots of the DiO labeled blood cells.The blood velocity and volume in the noise exposed group were significantly lower than in the control group. The successful establishment of the open vessel window requires a high degree of surgical skill. Care must be exercised in removing the bone of the cochlear lateral wall.

measurement-strial-blood-flow-mouse-cochlea-utilizing-an-open-vessel

Research

JoVE Journal

Medicine

Visualization and Analysis of Blood Flow and Oxygen Consumption in Hepatic Microcirculation: Application to an Acute Hepatitis Model

There is a considerable discrepancy between oxygen supply and demand in the liver because hepatic oxygen consumption is relatively high but about 70% of the hepatic blood supply is poorly oxygenated portal vein blood derived from the gastrointestinal tract and spleen. Oxygen is delivered to hepatocytes by blood flowing from a terminal branch of the portal vein to a central venule via sinusoids, and this makes an oxygen gradient in hepatic lobules. The oxygen gradient is an important physical parameter that involves the expression of enzymes upstream and downstream in hepatic microcirculation, but the lack of techniques for measuring oxygen consumption in the hepatic microcirculation has delayed the elucidation of mechanisms relating to oxygen metabolism in liver. We therefore used FITC-labeled erythrocytes to visualize the hepatic microcirculation and used laser-assisted phosphorimetry to measure the partial pressure of oxygen in the microvessels there. Noncontact and continuous optical measurement can quantify blood flow velocities, vessel diameters, and oxygen gradients related to oxygen consumption in the liver. In an acute hepatitis model we made by administering acetaminophen to mice we observed increased oxygen pressure in both portal and central venules but a decreased oxygen gradient in the sinusoids, indicating that hepatocyte necrosis in the pericentral zone could shift the oxygen pressure up and affect enzyme expression in the periportal zone. In conclusion, our optical methods for measuring hepatic hemodynamics and oxygen consumption can reveal mechanisms related to hepatic disease.

An optical system was developed to visualize hepatic microcirculation with FITC-labeled erythrocytes and to measure the partial pressure of oxygen in the microvessels with laser-assisted phosphorimetry. This method can be used to investigate physiological and pathological mechanisms by analyzing microvascular structure, diameter, blood flow velocity, and oxygen tension.

There is a considerable discrepancy between oxygen supply and demand in the liver because hepatic oxygen consumption is relatively high but about 70% of ...

An Orthotopic Glioblastoma Mouse Model Maintaining Brain Parenchymal Physical Constraints and Suitable for Intravital Two-photon Microscopy

Glioblastoma multiforme (GBM) is the most aggressive form of brain tumors with no curative treatments available to date.
Murine models of this pathology rely on the injection of a suspension of glioma cells into the brain parenchyma following incision of the dura-mater. Whereas the cells have to be injected superficially to be accessible to intravital two-photon microscopy, superficial injections fail to recapitulate the physiopathological conditions. Indeed, escaping through the injection tract most tumor cells reach the extra-dural space where they expand abnormally fast in absence of mechanical constraints from the parenchyma.
Our improvements consist not only in focally implanting a glioma spheroid rather than injecting a suspension of glioma cells in the superficial layers of the cerebral cortex but also in clogging the injection site by a cross-linked dextran gel hemi-bead that is glued to the surrounding parenchyma and sealed to dura-mater with cyanoacrylate. Altogether these measures enforce the physiological expansion and infiltration of the tumor cells inside the brain parenchyma. Craniotomy was finally closed with a glass window cemented to the skull to allow chronic imaging over weeks in absence of scar tissue development.
Taking advantage of fluorescent transgenic animals grafted with fluorescent tumor cells we have shown that the dynamics of interactions occurring between glioma cells, neurons (e.g. Thy1-CFP mice) and vasculature (highlighted by an intravenous injection of a fluorescent dye) can be visualized by intravital two-photon microscopy during the progression of the disease.
The possibility to image a tumor at microscopic resolution in a minimally compromised cerebral environment represents an improvement of current GBM animal models which should benefit the field of neuro-oncology and drug testing.

We have established a cortical orthotopic glioblastoma model in mice for intravital two-photon microscopy that recapitulates the biophysical constraints normally at play during the growth of the tumor. A chronic glass window replacing the skull above the tumor enables the follow-up of the tumor progression over time by two-photon microscopy.

Glioblastoma multiforme (GBM) is the most aggressive form of brain tumors with no curative treatments available to date.
Murine models of this pathology ...

Intravital Video Microscopy Measurements of Retinal Blood Flow in Mice

Alterations in retinal blood flow can contribute to, or be a consequence of, ocular disease and visual dysfunction. Therefore, quantitation of altered perfusion can aid research into the mechanisms of retinal pathologies. Intravital video microscopy of fluorescent tracers can be used to measure vascular diameters and bloodstream velocities of the retinal vasculature, specifically the arterioles branching from the central retinal artery and of the venules leading into the central retinal vein. Blood flow rates can be calculated from the diameters and velocities, with the summation of arteriolar flow, and separately venular flow, providing values of total retinal blood flow. This paper and associated video describe the methods for applying this technique to mice, which includes 1) the preparation of the eye for intravital microscopy of the anesthetized animal, 2) the intravenous infusion of fluorescent microspheres to measure bloodstream velocity, 3) the intravenous infusion of a high molecular weight fluorescent dextran, to aid the microscopic visualization of the retinal microvasculature, 4) the use of a digital microscope camera to obtain videos of the perfused retina, and 5) the use of image processing software to analyze the video. The same techniques can be used for measuring retinal blood flow rates in rats.

Intravital microscopy can be used in animals to visualize and measure retinal vascular diameters, bloodstream velocities, and total retinal blood flow.

Alterations in retinal blood flow can contribute to, or be a consequence of, ocular disease and visual dysfunction. Therefore, quantitation of altered ...

Automated Measurement of Microcirculatory Blood Flow Velocity in Pulmonary Metastases of Rats

Because the lung is a major target organ of metastatic disease, animal models to study the physiology of pulmonary metastases are of great importance. However, very few methods exist to date to investigate lung metastases in a dynamic fashion at the microcirculatory level, due to the difficulty to access the lung with a microscope. Here, an intravital microscopy method is presented to functionally image and quantify the microcirculation of superficial pulmonary metastases in rats, using a closed-chest pulmonary window and automated analysis of blood flow velocity and direction. The utility of this method is demonstrated to measure increases in blood flow velocity in response to pharmacological intervention, and to image the well-known tortuous vasculature of solid tumors. This is the first demonstration of intravital microscopy on pulmonary metastases in a closed-chest model. Because of its minimized invasiveness, as well as due to its relative ease and practicality, this technology has the potential to experience widespread use in laboratories that specialize on pulmonary tumor research.

A method is presented to measure microcirculatory blood flow velocity in pulmonary cancer metastases of the pleural surface in rats in an automated fashion, using closed-chest pulmonary intravital microscopy. This model has potential to be used as a widespread tool to perform physiologic research on pulmonary metastases in rodents.

Because the lung is a major target organ of metastatic disease, animal models to study the physiology of pulmonary metastases are of great importance. ...

Evaluation of Planar-Cell-Polarity Phenotypes in Ciliopathy Mouse Mutant Cochlea

In recent years, primary cilia have emerged as key regulators in development and disease by influencing numerous signaling pathways. One of the earliest signaling pathways shown to be associated with ciliary function was the non-canonical Wnt signaling pathway, also referred to as planar cell polarity (PCP) signaling. One of the best places in which to study the effects of planar cell polarity (PCP) signaling during vertebrate development is the mammalian cochlea. PCP signaling disruption in the mouse cochlea disrupts cochlear outgrowth, cellular patterning and hair cell orientation, all of which are affected by cilia dysfunction. The goal of this protocol is to describe the analysis of PCP signaling in the developing mammalian cochlea via phenotypic analysis, immunohistochemistry and scanning electron microscopy. Defects in convergence and extension are manifested as a shortening of the cochlear duct and/or changes in cellular patterning, which can be quantified following dissection from developing mouse mutants. Changes in stereociliary bundle orientation and kinocilia length or positioning can be observed and quantitated using either immunofluorescence or scanning electron microscopy (SEM). A deeper insight into the role of ciliary proteins in cellular signaling pathways and other biological phenomena is crucial for our understanding of cellular and developmental biology, as well as for the development of targeted treatment strategies.

Primary cilia influence various signaling pathways. The mammalian cochlea is ideal for examining planar cell polarity (PCP) signaling. Cilia dysfunction affects cochlear outgrowth, cellular patterning and hair cell orientation, readouts of PCP. Our goal is to analyze PCP signaling in mouse cochlea via phenotypic analysis, immunohistochemistry and scanning electron microscopy.

In recent years, primary cilia have emerged as key regulators in development and disease by influencing numerous signaling pathways. One of the earliest ...

Combined Intravital Microscopy and Contrast-enhanced Ultrasonography of the Mouse Hindlimb to Study Insulin-induced Vasodilation and Muscle Perfusion

It has been demonstrated that insulin's vascular actions contribute to regulation of insulin sensitivity. Insulin's effects on muscle perfusion regulate postprandial delivery of nutrients and hormones to insulin-sensitive tissues. We here describe a technique for combining intravital microscopy (IVM) and contrast-enhanced ultrasonography (CEUS) of the adductor compartment of the mouse hindlimb to simultaneously visualize muscle resistance arteries and perfusion of the microcirculation in vivo. Simultaneously assessing insulin's effect at multiple levels of the vascular tree is important to study relationships between insulin's multiple vasoactive effects and muscle perfusion. Experiments in this study were performed in mice. First, the tail vein cannula is inserted for the infusion of anesthesia, vasoactive compounds and ultrasound contrast agent (lipid-encapsulated microbubbles). Second, a small incision is made in the groin area to expose the arterial tree of the adductor muscle compartment. The ultrasound probe is then positioned at the contralateral upper hindlimb to view the muscles in cross-section. To assess baseline parameters, the arterial diameter is assessed and microbubbles are subsequently infused at a constant rate to estimate muscle blood flow and microvascular blood volume (MBV). When applied before and during a hyperinsulinemic-euglycemic clamp, combined IVM and CEUS allow assessment of insulin-induced changes of arterial diameter, microvascular muscle perfusion and whole-body insulin sensitivity. Moreover, the temporal relationship between responses of the microcirculation and the resistance arteries to insulin can be quantified. It is also possible to follow-up the mice longitudinally in time, making it a valuable tool to study changes in vascular and whole-body insulin sensitivity.

Insulin-induced vasodilation regulates muscle perfusion and increases the microvascular surface area (microvascular recruitment) available for solute exchange between blood and tissue interstitium. Combined intravital microscopy and contrast-enhanced ultrasonography is presented to simultaneously assess insulin&#39;s action at the larger vessels and the microcirculation in vivo.

It has been demonstrated that insulin's vascular actions contribute to regulation of insulin sensitivity. Insulin's effects on muscle perfusion regulate ...

Intravital Microscopy and Thrombus Induction in the Earlobe of a Hairless Mouse

Thrombotic complications of vascular diseases are one leading cause of morbidity and mortality in industrial nations. Due to the complex interactions between cellular and non-cellular blood components during thrombus formation, reliable studies of the physiology and pathophysiology of thrombosis can only be performed in vivo. Therefore, this article presents an ear model in hairless mice and focuses on the in vivo analysis of microcirculation, thrombus formation, and thrombus evolution. By using intravital fluorescence microscopy and the intravenous (iv) application of the respective fluorescent dyes, a repetitive analysis of microcirculation in the auricle can easily be performed, without the need for surgical preparation. Furthermore, this model can be adapted for in vivo studies of different issues, including wound healing, reperfusion injury, or angiogenesis. In summary, the ear of hairless mice is an ideal model for the in vivo study of skin microcirculation in physiological or pathophysiological conditions and for the evaluation of its reaction to different systemic or topical treatments.

The ear model of the hairless SKH1-Hrhr mouse enables intravital fluorescence microscopy of microcirculation and phototoxic thrombus induction without prior surgical preparation in the examined microvascular bed. Therefore, the ear of the hairless mouse is an excellent in vivo model to study the complex interactions during microvascular thrombus formation, thrombus evolution, and thrombolysis.

Thrombotic complications of vascular diseases are one leading cause of morbidity and mortality in industrial nations. Due to the complex interactions ...

Simultaneous Electrocardiography Recording and Invasive Blood Pressure Measurement in Rats

For studies related to cardiovascular physiology or pathophysiology, blood pressure (BP) and electrocardiography are basic observational parameters. Research focusing on cardiovascular disease models, potential cardiovascular therapeutic targets or pharmaceutical agents requires assessment of systemic arterial pressure and heart rhythm changes. In situations where radio telemetry systems are not available or affordable, the technique of femoral artery cannulation is an alternative way to obtain intra-arterial pressure waveform recordings and systemic BP measurements. This technique is economical and can be performed with standard equipment in animal facilities. However, invasive arterial pressure recording requires cannulation of small arteries, which can be a challenging surgical skill. Here, we present step-by-step protocols for femoral artery cannulation procedures. Key procedures include the calibration of the data acquisition system, tissue dissection and femoral artery cannulation, and setup of the arterial cannulation system for pressure recording. Surface electrocardiography recording procedures are also included. We also present examples of BP recordings from normotensive and hypertensive rats. This protocol allows reliable direct recordings of systemic BP with simultaneous electrocardiography.

Here, we describe a setup for simultaneous recording of electrocardiography and intra-arterial blood pressure (BP) in experimental rats, which can be done with standard equipment in animal facilities and can be applied to physiological or pharmacological studies to investigate pathogenic or therapeutic mechanisms in cardiovascular medicine.

For studies related to cardiovascular physiology or pathophysiology, blood pressure (BP) and electrocardiography are basic observational parameters. ...

Simultaneous Flow Cytometric Characterization of Multiple Cell Types Retrieved from Mouse Brain/Spinal Cord Through Different Homogenization Methods

Recent advances in viral vector and nanomaterial sciences have opened the way for new cutting-edge approaches to investigate or manipulate the central nervous system (CNS). However, further optimization of these technologies would benefit from methods allowing rapid and streamline determination of the extent of CNS and cell-specific targeting upon administration of viral vectors or nanoparticles in the body. Here, we present a protocol that takes advantage of the high throughput and multiplexing capabilities of flow cytometry to allow a straightforward quantification of different cell subtypes isolated from mouse brain or spinal cord, namely microglia/macrophages, lymphocytes, astrocytes, oligodendrocytes, neurons and endothelial cells. We apply this approach to highlight critical differences between two tissue homogenization methods in terms of cell yield, viability and composition. This could instruct the user to choose the best method depending on the cell type(s) of interest and the specific application. This method is not suited for analysis of anatomical distribution, since the tissue is homogenized to generate a single-cell suspension. However, it allows to work with viable cells and it can be combined with cell-sorting, opening the way for several applications that could expand the repertoire of tools in the hands of the neuroscientist, ranging from establishment of primary cultures derived from pure cell populations, to gene-expression analyses and biochemical or functional assays on well-defined cell subtypes in the context of neurodegenerative diseases, upon pharmacological treatment or gene therapy.

We present a flow cytometry method to identify simultaneously different cell types retrieved from mouse brain or spinal cord. This method could be exploited to isolate or characterize pure cell populations in neurodegenerative diseases or to quantify the extent of cell targeting upon in vivo administration of viral vectors or nanoparticles.

Recent advances in viral vector and nanomaterial sciences have opened the way for new cutting-edge approaches to investigate or manipulate the central ...

Hemocompatibility Testing of Blood-Contacting Implants in a Flow Loop Model Mimicking Human Blood Flow

The growing use of medical devices (e.g., vascular grafts, stents, and cardiac catheters) for temporary or permanent purposes that remain in the body&#39;s circulatory system demands a reliable and multiparametric approach that evaluates the possible hematologic complications caused by these devices (i.e., activation and destruction of blood components). Comprehensive in vitro hemocompatibility testing of blood-contacting implants is the first step towards successful in vivo implementation. Therefore, extensive analysis according to the International Organization for Standardization 10993-4 (ISO 10993-4) is mandatory prior to clinical application. The presented flow loop describes a sensitive model to analyze the hemostatic performance of stents (in this case, neurovascular) and reveal adverse effects. The use of fresh human whole blood and gentle blood sampling are essential to avoid the preactivation of blood. The blood is perfused through a heparinized tubing containing the test specimen by using a peristaltic pump at a rate of 150 mL/min at 37 &#176;C for 60 min. Before and after perfusion, hematologic markers (i.e., blood cell count, hemoglobin, hematocrit, and plasmatic markers) indicating the activation of leukocytes (polymorphonuclear [PMN]-elastase), platelets (&#946;-thromboglobulin [&#946;-TG]), the coagulation system (thombin-antithrombin III [TAT]), and the complement cascade (SC5b-9) are analyzed. In conclusion, we present an essential and reliable model for extensive hemocompatibility testing of stents and other blood-contacting devices prior to clinical application.

This protocol describes a comprehensive hemocompatibility evaluation of blood-contacting devices using laser-cut neurovascular implants. A flow loop model with fresh, heparinized human blood is applied to mimic blood flow. After perfusion, various hematologic markers are analyzed and compared to the values gained directly after blood collection for hemocompatibility evaluation of the tested devices.