Name: dynamic measurement and imaging of capillaries, arterioles, and pericytes in mouse heart
Uploaded: 2020-07-29T14:00:00
Description: Watch this Scientific Journal Video about Dynamic Measurement and Imaging of Capillaries, Arterioles, and Pericytes in Mouse Heart at JoVE.com

This work was supported in part by the Center for Biomedical Engineering and Technology (BioMET); NIH (1U01HL116321) and (1R01HL142290) and the American Heart Association 10SDG4030042 (GZ), 19POST34450156 (HCJ).

All animal care was in accordance with the guidelines of the University of Maryland Baltimore and the Institutional Animal Care and Use Committee approved protocols.
1. Preparation of the solutions
NOTE: Prepare solutions in advance. Two types of basic solutions are used in the experiments: (1) physiological saline solutions (PSS) for bath superfusate and (2) Tyrode&#8217;s solutions for lumen perfusate. Continuous bubbling with CO2 is needed to maintain th...

<ol>
	<li>Zhao, G., Joca, H. C., Nelson, M. T., Lederer, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ATP-+and+voltage-dependent+electro-metabolic+signaling+regulates+blood+flow+in+heart.">ATP- and voltage-dependent electro-metabolic signaling regulates blood flow in heart.</a> Proceedings of the National Academy of Sciences of the United States of America. 117, 7461-7470 (2020).</li><li>Schouten, V. J., Allaart, C. P., Westerhof, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+perfusion+pressure+on+force+of+contraction+in+thin+papillary+muscles+and+trabeculae+from+rat+heart.">Effect of perfusion pressure on force of contraction in thin papillary muscles and trabeculae from rat heart.</a> Journal of Physiology. 451, 585-604 (1992).</li><li>Tillmanns, H., 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=Microcirculation+in+the+ventricle+of+the+dog+and+turtle.">Microcirculation in the ventricle of the dog and turtle.</a> Circulation Research. 34, 561-569 (1974).</li><li>Martini, J., Honig, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+measurement+of+intercapillary+distance+in+beating+rat+heart+in+situ+under+various+conditions+of+O2+supply.">Direct measurement of intercapillary distance in beating rat heart in situ under various conditions of O2 supply.</a> Microvascular Research. 1, 244-256 (1969).</li><li>Nellis, S. H., Liedtke, A. J., Whitesell, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small+coronary+vessel+pressure+and+diameter+in+an+intact+beating+rabbit+heart+using+fixed-position+and+free-motion+techniques.">Small coronary vessel pressure and diameter in an intact beating rabbit heart using fixed-position and free-motion techniques.</a> Circulation Research. 49, 342-353 (1981).</li><li>Marcus, M. 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=Understanding+the+coronary+circulation+through+studies+at+the+microvascular+level.">Understanding the coronary circulation through studies at the microvascular level.</a> Circulation. 82, 1-7 (1990).</li><li>Ralevic, V., Kristek, F., Hudlicka, O., Burnstock, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+protocol+for+removal+of+the+endothelium+from+the+perfused+rat+hind-limb+preparation.">A new protocol for removal of the endothelium from the perfused rat hind-limb preparation.</a> Circulation Research. 64, 1190-1196 (1989).</li><li>Zhao, G., Adebiyi, A., Blaskova, E., Xi, Q., Jaggar, 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=Type+1+inositol+1,4,5-trisphosphate+receptors+mediate+UTP-induced+cation+currents,+Ca2++signals,+and+vasoconstriction+in+cerebral+arteries.">Type 1 inositol 1,4,5-trisphosphate receptors mediate UTP-induced cation currents, Ca2+ signals, and vasoconstriction in cerebral arteries.</a> Amercian Journal of Physiology-Cell Physiology. 295, 1376-1384 (2008).</li><li>Zhao, G., Li, T., Brochet, D. X., Rosenberg, P. B., Lederer, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=STIM1+enhances+SR+Ca2++content+through+binding+phospholamban+in+rat+ventricular+myocytes.">STIM1 enhances SR Ca2+ content through binding phospholamban in rat ventricular myocytes.</a> Proceedings of the National Academy of Sciences of the United States of America. 112, 4792-4801 (2015).</li><li>Stowe, D. F., Boban, M., Graf, B. M., Kampine, J. P., Bosnjak, Z. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contraction+uncoupling+with+butanedione+monoxime+versus+low+calcium+or+high+potassium+solutions+on+flow+and+contractile+function+of+isolated+hearts+after+prolonged+hypothermic+perfusion.">Contraction uncoupling with butanedione monoxime versus low calcium or high potassium solutions on flow and contractile function of isolated hearts after prolonged hypothermic perfusion.</a> Circulation. 89, 2412-2420 (1994).</li><li>Lawton, P. F., 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=a+Low-Cost+and+Open+Source+Pressure+Myograph+System+for+Vascular+Physiology.">a Low-Cost and Open Source Pressure Myograph System for Vascular Physiology.</a> Frontiers in Physiology. 10, 99 (2019).</li><li>Kim, K. J., Filosa, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advanced+in+vitro+approach+to+study+neurovascular+coupling+mechanisms+in+the+brain+microcirculation.">Advanced in vitro approach to study neurovascular coupling mechanisms in the brain microcirculation.</a> Journal of Physiology. 590, 1757-1770 (2012).</li></ol>

In the present work, we have introduced a remarkably simple yet highly practical ex vivo method to study the coronary microcirculation in heart under physiological conditions. This method was modified from mechanical investigations using rats2. The challenging addition was the imaging technology with high speed and high optical resolution. We, therefore, were able to take advantage of the advanced optical imaging systems that are now commercially available. By careful dissection and placement of t...

Appropriate coronary pressure-flow regulation assures sufficient blood supply to the heart to meet its metabolic demands1. However, it has only recently become clear how coronary pressure-flow is dynamically regulated in heart, despite extensive studies that have been performed in vivo and in vitro for the past decades. One of the reasons is the difficulty in establishing a physiological working model for such studies due to the constant beating of the heart. Regardless, a variety of methods have been established for the observation of the coronary micro-vessels in living tissues or animals, but none of these methods were able to achieve constant/stable focus and the measurements of the pressure, flow and microvascular diameter at the same time2,3. The direct visualization of coronary arterial micro-vessels in beating heart was introduced decades ago4,3, but the diameter measurements in small vessels was challenging and the specific functions of the many specialized cell types associated with the microcirculation was equally vexing. Even the stroboscopic method and the floating objective system could not provide the above information simultaneously5. Nevertheless, a significant amount of valuable information has been obtained using the aforementioned technologies, which have helped us understanding more about the regulation of coronary blood flow6. The method we are describing in this paper will help one investigate and understand in detail how components of coronary arteries, the arterioles and the microvasculature respond differently to stimulations and metabolic demands.
The working model we established to pursue these studies was built on the previous work of Westerhof et al.2. Following cannulation of the septal artery of the mouse heart, physiological saline solution was used to perfuse that artery to keep the myocytes and other components of the heart tissue nourished. The arterial perfusion pressure, the flow and the vascular diameter was monitored among other physiological functions using appropriate fluorescent indicators. This method enables us to visualize the coronary microvascular bed under physiological pressure in living tissue and study the cellular mechanisms underlying microcirculation regulation for the first time.

<table>
	<tbody>
		<tr>
			<td>1 M CaCl2 solution</td>
			<td>MilliporeSigma, USA</td>
			<td>21115</td>
			<td></td>
		</tr>
		<tr>
			<td>1 M MgCl2 solution</td>
			<td>MilliporeSigma, USA</td>
			<td>M1028</td>
			<td></td>
		</tr>
		<tr>
			<td>AxoScope software</td>
			<td>Molecular Devices, San Jose, CA, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chiller/water incubator</td>
			<td>FisherScientific, USA</td>
			<td>Isotemp 3016S</td>
			<td></td>
		</tr>
		<tr>
			<td>Confocal</td>
			<td>Nikon Instruments, USA</td>
			<td>A1R</td>
			<td></td>
		</tr>
		<tr>
			<td>Custom glass tubing</td>
			<td>Drummond Scientific Company</td>
			<td>9-000-3301</td>
			<td></td>
		</tr>
		<tr>
			<td>Digidata 1322A</td>
			<td>Molecular Devices, San Jose, CA, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting microscope</td>
			<td>Olympus, Japan</td>
			<td>SZX12</td>
			<td></td>
		</tr>
		<tr>
			<td>Endothelin-1</td>
			<td>MilliporeSigma, USA</td>
			<td>E7764</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps</td>
			<td>Fine Scientific Tools</td>
			<td>11295-51</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparin Sodium Salt</td>
			<td>Sigma-Aldrich, USA</td>
			<td>H3393</td>
			<td></td>
		</tr>
		<tr>
			<td>Inline solution Heater</td>
			<td>Warner Istruments, Hamden, CT, USA</td>
			<td>SH-27B</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>VETone, Idaho, USA</td>
			<td>502017</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipette puller</td>
			<td>Sutter Instruments, Novato, CA, USA</td>
			<td>P-97</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipette/cannula holder</td>
			<td>Warner Istruments, Hamden, CT, USA</td>
			<td>64-0981</td>
			<td></td>
		</tr>
		<tr>
			<td>NG2DsRedBAC transgenic mouse</td>
			<td>The Jackson Laboratory</td>
			<td>#008241</td>
			<td></td>
		</tr>
		<tr>
			<td>Nylon thread for tying blood vessels</td>
			<td>Living Systems Instrumentation, Burlington, Vt, USA</td>
			<td>THR-G</td>
			<td></td>
		</tr>
		<tr>
			<td>PDMS (polydimethylsiloxane)</td>
			<td>SYLGARD, Germantown, WI, USA</td>
			<td>184 SIL ELAST KIT</td>
			<td></td>
		</tr>
		<tr>
			<td>Peristaltic pump</td>
			<td>Gilson, Middleton, WI, USA</td>
			<td>minipuls 3</td>
			<td></td>
		</tr>
		<tr>
			<td>Pressure Servo Controller</td>
			<td>Living Systems Instrumentation, Burlington, Vt, USA</td>
			<td>PS-200-S</td>
			<td></td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>Fine Scientific Tools, Foster City, CA, USA</td>
			<td>15000-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Servo Pump</td>
			<td>Living Systems Instrumentation, Burlington, Vt, USA</td>
			<td>PS-200-P</td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature controller</td>
			<td>Warner Instruments, Hamden, CT, USA</td>
			<td>TC-324B</td>
			<td></td>
		</tr>
		<tr>
			<td>Wheat Germ Agglutinin, Alexa Fluor 488 Conjugate</td>
			<td>ThermoFisher Scientific, Waltham, MA USA</td>
			<td>W11261</td>
			<td></td>
		</tr>
	</tbody>
</table>

dynamic measurement and imaging of capillaries, arterioles, and pericytes in mouse heart

Coronary arterial tone along with the opening or closing of the capillaries largely determine the blood flow to cardiomyocytes at constant perfusion pressure. However, it is difficult to monitor the dynamic changes of the coronary arterioles and the capillaries in the whole heart, primarily due to its motion and non-stop beating. Here we describe a method that enables monitoring of arterial perfusion rate, pressure and the diameter changes of the arterioles and capillaries in mouse right ventricular papillary muscles. The mouse septal artery is cannulated and perfused at a constant flow or pressure with the other dynamically measured. After perfusion with a fluorescently labeled lectin (e.g., Alexa Fluor-488 or -633 labeled Wheat-Germ Agglutinin, WGA), the arterioles and capillaries (and other vessels) in right ventricle papillary muscle and septum could be readily imaged. The vessel-diameter changes could then be measured in the presence or absence of heart contractions. When genetically encoded fluorescent proteins were expressed, specific features could be monitored. For examples, pericytes were visualized in mouse hearts that expressed NG2-DsRed. This method has provided a useful platform to study the physiological functions of capillary pericytes in heart. It is also suitable for studying the effect of reagents on the blood flow in heart by measuring the vascular/capillary diameter and the arterial luminal pressure simultaneously. This preparation, combined with a state-of-the-art optic imaging system, allows one to study the blood flow and its control at cellular and molecular level in the heart under near-physiological conditions.

When a fluorescence vascular marker is perfused in vascular lumen (here WGA conjugated with Alexa Fluor-488), it is possible to visualize whole vascular trees as shown in Figure 5 (Left panel) using high-speed confocal microscope. Further magnification enables the imaging of capillary in detail (Figure 5, Right Panel). Since the pressurized system supports a constant monitoring of luminal pressure, this preparation can be used for associate changes in arterial d...

Watch this Scientific Journal Video about Dynamic Measurement and Imaging of Capillaries, Arterioles, and Pericytes in Mouse Heart at JoVE.com

Dynamic Measurement and Imaging of Capillaries, Arterioles, and Pericytes in Mouse Heart

Presented here is a protocol to study the coronary microcirculation in living murine heart tissue by ex vivo monitoring of the arterial perfusion pressure and flow that maintains the pressure, as well as vascular tree components including the capillary beds and pericytes, as the septal artery is cannulated and pressurized.

Coronary arterial tone along with the opening or closing of the capillaries largely determine the blood flow to cardiomyocytes at constant perfusion ...

This method can be used to study coronary microcirculation in living murine heart tissue and vascular-tree components by ex vivo monitoring of the arterial perfusion pressure and flow. This method provides a useful platform for studying the function of pericytes and reagents microcirculation within the heart, by so we tend measuring the vascular diameter and arteriole luminal pressure. To prepare a cannula for the experiment, use a micropipette puller to produce two cannulae with long thin tips, from a single clean borosilicate glass tube.Use a fine pair of scissors and a dissecting microscope to cut the tip of each cannula to a final tip diameter of 100 to 150 micrometers, and fire polish the tips to slightly round the sharp edges. Use a platinum wire positioned on the side of the shaft, approximately two millimeters from the tip to bend the cannula along the shaft to an about 45-degree angle, and insert the open end of the cannula into the cannula holder. Then, tighten the fitting, and use a five milliliter syringe to flush the cannula and tubing with Tyrode's solution.Mount the cannula holder onto micro-manipulation of a pressure myograph chamber. To collect a mouse heart for the experiment, first enter a pair in it inject 500 microliters of heparin into an anesthetized eight to 16-week-old C 57 black six mouse. After 10 minutes, place the mouse onto a heated bed in the supine position, and stabilize the paws with labeling tape.Use forceps and surgical scissors to make an incision in the abdominal skin, above the diaphragm and cut the diaphragm and the sternum to allow dissection of the heart from the thoracic cavity. Place the heart into ice cold Tyrode's solution containing 30 millimolar BDM and remove any connective tissues from the heart as necessary. Then place the heart into a pre-chilled dissecting chamber, filled with fresh Tyrode's solution supplemented with 30 millimolar BDM.To prepare the septal artery for cannulation, turn on the servo pomp, and set the servo controller pressure to flow mode. In the heart onto the PDMS, taking care to avoid damage to the middle area of the tissue and place the tissue under a dissecting microscope. Remove one or both atria, and cut open the right ventricle.Remove the right ventricular free wall and expose the septal artery. Use a 30 micrometer diameter nylon thread to tie a loose knot around the septal artery. Use fine scissors to remove the left ventricular free wall and transfer the papillary muscle preparation to the experimental chamber.Use a micro manipulator to insert a cannula into the septal artery and secure the cannula with the suture. Then use pins to secure the papillary muscle to the chamber floor with the tip of the cannula parallel to the arterial wall, so that a clear view of the vasculature can be obtained and use the syringe to gradually flush the solution through the cannula. To stabilize the tissue preparation, turn on a peristaltic pump and continuously super fuse the preparation with pre-gassed physiological saline solution at a three to four milliliters per minute flow rate, turn on the temperature controller for the superfusion solution, and adjust the temperature of the bath superfusate to 35 to 37 degrees Celsius.Connect the cannula to the servo pump and adjust the flow to set the pressure to approximately 10 millimeters of mercury. Let the superfusion run for about 10 minutes, then increase the flow of the luminal solution to set the artery pressure to approximately 60 millimeters of mercury and allow the sample to stabilize for 30 to 60 minutes with monitoring. To load the sample with wheat-germ agglutinin, perfuse the preparation with five milliliters of Tyrode's solution, supplemented with 100 micrograms of Alexa Fluor-488 Conjugated Wheat-Germ Agglutinin.After 30 minutes, change the perfuse aid back to normal Tyrode's solution and turn on the confocal microscope system. Use the microscope at a lower power of magnification, to locate the septal artery in transmitted light mode, and begin imaging with this spinning disc confocal. Select a 40X objective magnification, and the 488 nanometer excitation laser, and adjust the laser intensity and the sampling rate.To define the imaging range, set the top and bottom imaging positions for the microscope and set the step size and Z-stack imaging parameters. Then, select a folder for storing the image and click run to begin recording the images. When a fluorescence vascular marker is perfused into the vascular lumen, it's possible to visualize whole vascular trees, using high-speed confocal microscopy.Further magnification enables imaging of the capillary in detail. When pinacidil and ATP sensitive potassium channel agonist is served from the lumen, the diameter of the arterials increases. When the vasoconstrictor endothelin one is applied from the lumen.The diameter of the arterial decreases. When the flow set is constant, the luminal pressure increases. In these images of papillary tissue from an NG two DS red expressing transgenic mouse, both the capillary and pericytes can be visualized within the papillary muscle tissue, under conditions that better mimic the physiology of live animals.It's important that no bubbles are present within the tubing at any point during the procedure. Combining this method with optical imaging techniques, the preparation can be used to study microcirculation in the heart and intercellular communications between different cell types, using fluorescence tech transgenic mice.

dynamic-measurement-imaging-capillaries-arterioles-pericytes-mouse

Research

JoVE Journal

Medicine

Quantitative Visualization and Detection of Skin Cancer Using Dynamic Thermal Imaging

In 2010 approximately 68,720 melanomas will be diagnosed in the US alone, with around 8,650 resulting in death 1. To date, the only effective treatment for melanoma remains surgical excision, therefore, the key to extended survival is early detection 2,3. Considering the large numbers of patients diagnosed every year and the limitations in accessing specialized care quickly, the development of objective in vivo diagnostic instruments to aid the diagnosis is essential. New techniques to detect skin cancer, especially non-invasive diagnostic tools, are being explored in numerous laboratories. Along with the surgical methods, techniques such as digital photography, dermoscopy, multispectral imaging systems (MelaFind), laser-based systems (confocal scanning laser microscopy, laser doppler perfusion imaging, optical coherence tomography), ultrasound, magnetic resonance imaging, are being tested. Each technique offers unique advantages and disadvantages, many of which pose a compromise between effectiveness and accuracy versus ease of use and cost considerations. Details about these techniques and comparisons are available in the literature 4.
Infrared (IR) imaging was shown to be a useful method to diagnose the signs of certain diseases by measuring the local skin temperature. There is a large body of evidence showing that disease or deviation from normal functioning are accompanied by changes of the temperature of the body, which again affect the temperature of the skin 5,6. Accurate data about the temperature of the human body and skin can provide a wealth of information on the processes responsible for heat generation and thermoregulation, in particular the deviation from normal conditions, often caused by disease. However, IR imaging has not been widely recognized in medicine due to the premature use of the technology 7,8 several decades ago, when temperature measurement accuracy and the spatial resolution were inadequate and sophisticated image processing tools were unavailable. This situation changed dramatically in the late 1990s-2000s. Advances in IR instrumentation, implementation of digital image processing algorithms and dynamic IR imaging, which enables scientists to analyze not only the spatial, but also the temporal thermal behavior of the skin 9, allowed breakthroughs in the field.
In our research, we explore the feasibility of IR imaging, combined with theoretical and experimental studies, as a cost effective, non-invasive, in vivo optical measurement technique for tumor detection, with emphasis on the screening and early detection of melanoma 10-13. In this study, we show data obtained in a patient study in which patients that possess a pigmented lesion with a clinical indication for biopsy are selected for imaging. We compared the difference in thermal responses between healthy and malignant tissue and compared our data with biopsy results. We concluded that the increased metabolic activity of the melanoma lesion can be detected by dynamic infrared imaging.

We demonstrated that malignant pigmented lesions with increased metabolic activity generate quantifiable amounts of heat and the measurement of the transient thermal response of the skin to a cooling excitation allows quantitative identification of melanoma and other skin cancers (vs. non-proliferative nevi) at an early stage of the disease.

In 2010 approximately 68,720 melanomas will be diagnosed in the US alone, with around 8,650 resulting in death 1. To date, the only effective treatment ...

Segmentation and Measurement of Fat Volumes in Murine Obesity Models Using X-ray Computed Tomography

Obesity is associated with increased morbidity and mortality as well as reduced metrics in quality of life.1 Both environmental and genetic factors are associated with obesity, though the precise underlying mechanisms that contribute to the disease are currently being delineated.2,3 Several small animal models of obesity have been developed and are employed in a variety of studies.4 A critical component to these experiments involves the collection of regional and/or total animal fat content data under varied conditions.
Traditional experimental methods available for measuring fat content in small animal models of obesity include invasive (e.g. ex vivo measurement of fat deposits) and non-invasive (e.g. Dual Energy X-ray Absorptiometry (DEXA), or Magnetic Resonance (MR)) protocols, each of which presents relative trade-offs. Current invasive methods for measuring fat content may provide details for organ and region specific fat distribution, but sacrificing the subjects will preclude longitudinal assessments. Conversely, current non-invasive strategies provide limited details for organ and region specific fat distribution, but enable valuable longitudinal assessment. With the advent of dedicated small animal X-ray computed tomography (CT) systems and customized analytical procedures, both organ and region specific analysis of fat distribution and longitudinal profiling may be possible. Recent reports have validated the use of CT for in vivo longitudinal imaging of adiposity in living mice.5,6 Here we provide a modified method that allows for fat/total volume measurement, analysis and visualization utilizing the Carestream Molecular Imaging Albira CT system in conjunction with PMOD and Volview software packages.

Fat content analysis is routinely conducted in studies utilizing murine obesity models. Emerging methods in small animal CT imaging and analysis are providing for longitudinal detail rich fat content analysis. Here we detail step by step procedures for performing small animal CT imaging, analysis, and visualization.

Obesity is associated with increased morbidity and mortality as well as reduced metrics in quality of life.1 Both environmental and genetic factors are ...

Non-invasive Optical Measurement of Cerebral Metabolism and Hemodynamics in Infants

Perinatal brain injury remains a significant cause of infant mortality and morbidity, but there is not yet an effective bedside tool that can accurately screen for brain injury, monitor injury evolution, or assess response to therapy. The energy used by neurons is derived largely from tissue oxidative metabolism, and neural hyperactivity and cell death are reflected by corresponding changes in cerebral oxygen metabolism (CMRO2). Thus, measures of CMRO2 are reflective of neuronal viability and provide critical diagnostic information, making CMRO2 an ideal target for bedside measurement of brain health.
Brain-imaging techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) yield measures of cerebral glucose and oxygen metabolism, but these techniques require the administration of radionucleotides, so they are used in only the most acute cases.
Continuous-wave near-infrared spectroscopy (CWNIRS) provides non-invasive and non-ionizing radiation measures of hemoglobin oxygen saturation (SO2) as a surrogate for cerebral oxygen consumption. However, SO2 is less than ideal as a surrogate for cerebral oxygen metabolism as it is influenced by both oxygen delivery and consumption. Furthermore, measurements of SO2 are not sensitive enough to detect brain injury hours after the insult 1,2, because oxygen consumption and delivery reach equilibrium after acute transients 3. We investigated the possibility of using more sophisticated NIRS optical methods to quantify cerebral oxygen metabolism at the bedside in healthy and brain-injured newborns. More specifically, we combined the frequency-domain NIRS (FDNIRS) measure of SO2 with the diffuse correlation spectroscopy (DCS) measure of blood flow index (CBFi) to yield an index of CMRO2 (CMRO2i) 4,5.
With the combined FDNIRS/DCS system we are able to quantify cerebral metabolism and hemodynamics. This represents an improvement over CWNIRS for detecting brain health, brain development, and response to therapy in neonates. Moreover, this method adheres to all neonatal intensive care unit (NICU) policies on infection control and institutional policies on laser safety. Future work will seek to integrate the two instruments to reduce acquisition time at the bedside and to implement real-time feedback on data quality to reduce the rate of data rejection.

We combined frequency-domain near-infrared spectroscopy measures of cerebral hemoglobin oxygenation with diffuse correlation spectroscopy measures of cerebral blood flow index to estimate an index of oxygen metabolism. We tested the utility of this measure as a bedside screening tool to evaluate the health and development of the newborn brain.

Perinatal brain injury remains a significant cause of infant mortality  and morbidity, but there is not yet an effective bedside tool that can  accurately ...

In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography

Congenital heart disease (CHD) is the most frequent noninfectious cause of death at birth. The incidence of CHD ranges from 4 to 50/1,000 births (Disease and injury regional estimates, World Health Organization, 2004). Surgeries that often compromise the quality of life are required to correct heart defects, reminding us of the importance of finding the causes of CHD. Mutant mouse models and live imaging technology have become essential tools to study the etiology of this disease. Although advanced methods allow live imaging of abnormal hearts in embryos, the physiological and hemodynamic states of the latter are often compromised due to surgical and/or lengthy procedures. Noninvasive ultrasound imaging, however, can be used without surgically exposing the embryos, thereby maintaining their physiology. Herein, we use simple M-mode ultrasound to assess heart rates of embryos at E18.5 in utero. The detection of abnormal heart rates is indeed a good indicator of dysfunction of the heart and thus constitutes a first step in the identification of developmental defects that may lead to heart failure.

In utero Measurement of Heart Rate in Mouse by Noninvasive M-mode Echocardiography

Ultra-high frequency ultrasound is a powerful live imaging tool to examine cardiac abnormalities in small animals. Its noninvasiveness allows maintaining the physiologic state of embryos. Herein, we show the use of M-mode ultrasound to measure the heart rates of embryos at E18.5 in utero.

Congenital heart disease (CHD) is the most frequent noninfectious cause of death at birth. The incidence of CHD ranges from 4 to 50/1,000 births (Disease ...

Diagnostic Ultrasound Imaging of Mouse Diaphragm Function

Function analysis of rodent respiratory skeletal muscles, particularly the diaphragm, is commonly performed by isolating muscle strips using invasive surgical procedures. Although this is an effective method of assessing in vitro diaphragm activity, it involves non-survival surgery. The application of non-invasive ultrasound imaging as an in vivo procedure is beneficial since it not only reduces the number of animals sacrificed, but is also suitable for monitoring disease progression in live mice. Thus, our ultrasound imaging method may likely assist in the development of novel therapies that alleviate muscle injury induced by various respiratory diseases. Particularly, in clinical diagnoses of obstructive lung diseases, ultrasound imaging has the potential to be used in conjunction with other standard tests to detect the early onset of diaphragm muscle fatigue. In the current protocol, we describe how to accurately evaluate diaphragm contractility in a mouse model using a diagnostic ultrasound imaging technique.

Diagnostic ultrasound imaging has proven to be effective in diagnosing various respiratory diseases in human and animal subjects. We demonstrate a comprehensive ultrasound protocol utilized by Dr. Zuo's lab to analyze diaphragm kinetics specifically in mouse models. This is also a non-invasive research technique which can provide quantitative information on mouse respiratory muscle function.

Function analysis of rodent respiratory skeletal muscles, particularly the diaphragm, is commonly performed by isolating muscle strips using invasive ...

Dynamic Contrast Enhanced Magnetic Resonance Imaging of an Orthotopic Pancreatic Cancer Mouse Model

Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) has been limitedly used for orthotopic pancreatic tumor xenografts due to severe respiratory motion artifact in the abdominal area. Orthotopic tumor models offer advantages over subcutaneous ones, because those can reflect the primary tumor microenvironment affecting blood supply, neovascularization, and tumor cell invasion. We have recently established a protocol of DCE-MRI of orthotopic pancreatic tumor xenografts in mouse models by securing tumors with an orthogonally bent plastic board to prevent motion transfer from the chest region during imaging. The pressure by this board was localized on the abdominal area, and has not resulted in respiratory difficulty of the animals. This article demonstrates the detailed procedure of orthotopic pancreatic tumor modeling using small animals and DCE-MRI of the tumor xenografts. Quantification method of pharmacokinetic parameters in DCE-MRI is also introduced. The procedure described in this article will assist investigators to apply DCE-MRI for orthotopic gastrointestinal cancer mouse models.

The goal of this protocol is to apply dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) for orthotopic pancreatic tumor xenografts in mice. DCE-MRI is a non-invasive method to analyze microvasculature in a target tissue, and useful to assess vascular response in a tumor following a novel therapy.

Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) has been limitedly used for orthotopic pancreatic tumor xenografts due to severe ...

Preparation Steps for Measurement of Reactivity in Mouse Retinal Arterioles Ex Vivo

Vascular insufficiency and alterations in normal retinal perfusion are among the major factors for the pathogenesis of various sight-threatening ocular diseases, such as diabetic retinopathy, hypertensive retinopathy, and possibly glaucoma. Therefore, retinal microvascular preparations are pivotal tools for physiological and pharmacological studies to delineate the underlying pathophysiological mechanisms and to design therapies for the diseases. Despite the wide use of mouse models in ophthalmic research, studies on retinal vascular reactivity are scarce in this species. A major reason for this discrepancy is the challenging isolation procedures owing to the small size of these retinal blood vessels, which is ~ &#8804; 30 &#181;m in luminal diameter. To circumvent the problem of direct isolation of these retinal microvessels for functional studies, we established an isolation and preparation technique that enables ex vivo studies of mouse retinal vasoactivity under near-physiological conditions. Although the present experimental preparations will specifically refer to the mouse retinal arterioles, this methodology can readily be employed to microvessels from rats.

Preparation Steps for Measurement of Reactivity in Mouse Retinal Arterioles Ex Vivo

Many vision-threatening ocular diseases are associated with dysfunctional retinal microvessels. Therefore, the measurement of retinal arteriole responses is important to investigate the underlying pathophysiological mechanisms. This article describes a detailed protocol for mouse retinal arteriole isolation and preparation to assess the effects of vasoactive substances on vascular diameter.

Vascular insufficiency and alterations in normal retinal perfusion are among the major factors for the pathogenesis of various sight-threatening ocular ...

Quantitative [18F]-Naf-PET-MRI Analysis for the Evaluation of Dynamic Bone Turnover in a Patient with Facetogenic Low Back Pain

Imaging techniques that reflect dynamic bone turnover may aid in characterizing a wide range of bone pathologies. Bone is a dynamic tissue undergoing continuous remodeling with the competing activity of osteoblasts, which produce the new bone matrix, and osteoclasts, whose function is to eliminate mineralized bone. [18F]-NaF is a positron emission tomography (PET) radiotracer that enables visualization of bone metabolism. [18F]-NaF is chemically absorbed into hydroxyapatite in the bone matrix by osteoblasts and can thus noninvasively detect osteoblastic activity, which is occult to conventional imaging techniques. Kinetic modeling of dynamic [18F]-NaF-PET data provides detailed quantitative measures of bone metabolism. Conventional semi-quantitative PET data, which utilizes standardized uptake values (SUVs) as a measure of radiotracer activity, is referred to as a static technique due to its snapshot of tracer uptake in time.&#160; Kinetic modeling, however, utilizes dynamic image data where tracer levels are continuously acquired providing tracer uptake temporal resolution. From the kinetic modeling of dynamic data, quantitative values like blood flow and metabolic rate (i.e., potentially informative metrics of tracer dynamics) can be extracted, all with respect to the measured activity in the image data. When combined with dual modality PET-MRI, region-specific kinetic data can be correlated with anatomically registered high-resolution structural and pathologic information afforded by MRI. The goal of this methodological manuscript is to outline detailed techniques for performing and analyzing dynamic [18F]-NaF-PET-MRI data. The lumbar facet joint is a common site of degenerative arthritis disease and a common cause for axial low back pain.&#160; Recent studies suggest [18F]-NaF-PET may serve as a useful biomarker of painful facetogenic disease.&#160; The human lumbar facet joint will, therefore, be used as a prototypical region of interest for dynamic [18F]-NaF-PET-MRI analysis in this manuscript.

Quantitative [18F]-Naf-PET-MRI Analysis for the Evaluation of Dynamic Bone Turnover in a Patient with Facetogenic Low Back Pain

Imaging techniques that reflect dynamic bone turnover may aid in characterizing a wide range of bone pathologies. We present detailed methodologies for performing and analyzing dynamic [18F]-NaF-PET-MRI data in a patient with facetogenic low back pain using the lumbar facet joints as a prototypical region of interest.

Imaging techniques that reflect dynamic bone turnover may aid in characterizing a wide range of bone pathologies. Bone is a dynamic tissue undergoing ...

Isolation and Purification of Murine Cardiac Pericytes

Pericytes, perivascular cells of microvessels and capillaries, are known to play a part in angiogenesis, vessel stabilization, and endothelial barrier integrity. However, their tissue-specific functions in the heart are not well understood. Moreover, there is currently no protocol utilizing readily accessible materials to isolate and purify pericytes of cardiac origin. Our protocol focuses on using the widely used mammalian model, the mouse, as our source of cells. Using the enzymatic digestion and mechanical dissociation of heart tissue, we obtained a crude cell mixture that was further purified by fluorescence activating cell sorting (FACS) by a plethora of markers. Because there is no single unequivocal marker for pericytes, we gated for cells that were CD31-CD34-CD45-CD140b+NG2+CD146+. Following purification, these primary cells were cultured and passaged multiple times without any changes in morphology and marker expression. With the ability to regularly obtain primary murine cardiac pericytes using our protocol, we hope to further understand the role of pericytes in cardiovascular physiology and their therapeutic potential.

We have optimized a protocol to isolate and purify murine cardiac pericytes for basic research and investigation of their biology and therapeutic potential.

Pericytes, perivascular cells of microvessels and capillaries, are known to play a part in angiogenesis, vessel stabilization, and endothelial barrier ...

Whole-Mount Immunofluorescence Staining, Confocal Imaging and 3D Reconstruction of the Sinoatrial and Atrioventricular Node in the Mouse

The electrical signal physiologically generated by pacemaker cells in the sinoatrial node (SAN) is conducted through the conduction system, which includes the atrioventricular node (AVN), to allow excitation and contraction of the whole heart. Any dysfunction of either SAN or AVN results in arrhythmias, indicating their fundamental role in electrophysiology and arrhythmogenesis. Mouse models are widely used in arrhythmia research, but the specific investigation of SAN and AVN remains challenging.
The SAN is located at the junction of the crista terminalis with the superior vena cava and AVN is located at the apex of the triangle of Koch, formed by the orifice of the coronary sinus, the tricuspid annulus, and the tendon of Todaro. However, due to the small size, visualization by conventional histology remains challenging and it does not allow the study of SAN and AVN within their 3D environment.
Here we describe a whole-mount immunofluorescence approach that allows the local visualization of labelled mouse SAN and AVN. Whole-mount immunofluorescence staining is intended for smaller sections of tissue without the need for manual sectioning. To this purpose, the mouse heart is dissected, with unwanted tissue removed, followed by fixation, permeabilization and blocking. Cells of the conduction system within SAN and AVN are then stained with an anti-HCN4 antibody. Confocal laser scanning microscopy and image processing allow differentiation between nodal cells and working cardiomyocytes, and to clearly localize SAN and AVN. Furthermore, additional antibodies can be combined to label other cell types as well, such as nerve fibers.
Compared to conventional immunohistology, whole-mount immunofluorescence staining preserves the anatomical integrity of the cardiac conduction system, thus allowing the investigation of AVN; especially so into their anatomy and interactions with the surrounding working myocardium and non-myocyte cells.

We provide a step-by-step protocol for whole-mount immunofluorescence staining of the sinoatrial node (SAN) and atrioventricular node (AVN) in murine hearts.

The electrical signal physiologically generated by pacemaker cells in the sinoatrial node (SAN) is conducted through the conduction system, which includes ...