We thank Dr. William Cashdollar, and the Northwestern Mutual Foundation Imaging Center at the Blood Research Institute of Wisconsin for help with the imaging studies. We also thank Dr. Daria Ilatovskaya for critical reading of this manuscript and helpful discussion. This study was supported by National Institutes of Health Grants HL108880 (to A.S.) and DP2-OD008396 (to A.M.G.).

The experimental procedures described below were approved by the Institutional Animal Care and Use Committee (IACUC) at the Medical College of Wisconsin and were in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals.
1. Isolation of the Rat Aorta
<ol>
	<li>Anesthetize rats with isoflurane (5% induction, 1.5 to 2.5% maintenance) or another IACUC approved method.</li>
	<li>Place the rat in a supine position. In order to expose the abdominal organs, make a small ventral midline incision through the skin and the subcutaneous abdominal tissue. Using gauze pads gently deflect the intestines to expose the aorta and vena cava as shown in Figure 1.</li>
	<li>Briefly, blunt dissect the aorta from the connective tissue and from the vena cava. Using suture, tie off the aorta as close as possible to the kidney. Dissect about 1 - 2 cm of aorta and place it in a 15 ml&#160;conical tube containing normal Physiological Salt Solution (PSS; in mM: 140 NaCl, 1.2 MgCl2, 2 CaCl2, 4.5 KCl, 6 Glucose, 10 HEPES) on ice.</li>
	<li>Once the aorta is isolated, euthanize the animal according to approved IACUC protocols. At the completion of all non-survival procedures euthanize deeply anaesthetized animals by thoracotomy inducing pneumothorax to ensure the humane demise of the animal.3</li>
	<li>Using a dissection microscope, fine-tipped forceps, and microscissors dissect the fat and connective tissue off of the aorta. Once the aorta is clean, cut the aorta longitudinally and place it in PSS on ice for later.</li>
</ol>
2.&#160;Dye Loading and Incubation
<ol>
	<li>Pipet 7 &#181;l of 1 mM Fluo-4 AM dye, which is supplied in DMSO-based solution, into individual 500 &#181;l tubes that have been covered with aluminum foil. Store in the freezer at -20 &#730;C to preserve the dye properties over time. Note: these aliquoted solutions should be stable for at least six months.</li>
	<li>Before use, allow the dye solutions to warm up to RT before opening. Prepare working solutions immediately before use. Do not store the diluted reagent for later use.</li>
	<li>Add 7 &#956;l of ready-made 1 mM Fluo-4 AM dye dissolved in DMSO solution to 450 ul of PSS containing no calcium. Add 40 &#956;l of non DMSO based 10% Pluronic Acid solution to the loading cocktail to help disperse the acetoxymethyl (AM) esters and improve loading of the calcium dye.</li>
	<li>Place the dissected aortas into the 500 &#181;l tubes containing the loading cocktail (as described in 2.3) for 1 h. Cover all tubes with foil and place on a rotating shaker at RT.</li>
	<li>To monitor NO production in the vasculature, use DAF-FM diacetate dye. Incubate the aorta in a solution containing 450 &#181;l PSS, 40 &#181;l pluronic acid and 5 &#181;l of 10 mM DAF-FM diacetate. Similar to the calcium incubation protocol (described in 2.3), place the aorta in an 500 &#181;l tube containing the NO-dye solution covered in foil and place on a rotating shaker for 30 min at 4 &#730;C followed by next 30 min at RT.</li>
	<li>When NO production is measured, use the endothelial NO synthase blocker, L-NAME, to block NO production as a control as shown in Figure 4B. For that procedure, add to cocktail (as described at 2.5) 100 nM L-NAME for the last 30 min of incubation (at RT).</li>
</ol>
3. Laser Scanning Two photon Microscopy Protocol
<ol>
	<li>After the 1 h incubation, wash the aorta 2 - 3 times in clean PSS to remove extracellular dye.</li>
	<li>Transfer the aorta to a silicone-coated dish containing either normal PSS or Ca2+-free buffer (depends on the experimental protocol). Pin the aorta down onto the silicone coating with the adventitia in contact with the silicone (i.e., endothelial lumen exposed to the dish opening) using &#181;-shaped pins. Alternatively, use a Slice Anchor grid or glue to fix the tissue. 
	Note: To reduce stress and possible mechanical artifacts, transfer and fix aorta in Ca2+-free solution and wait 5 - 10 min before starting the experiment.</li>
	<li>Connect a peristaltic pump or a syringe to the silicone-coated plate for automatic or manual application of drugs or for changing the extracellular solution.</li>
	<li>Place the dish beneath the nose piece of the upright two-photon microscope, and install and position a 25&#215; (N.A. 1.05 and working distance 2 mm) water-immersion objective lens above the specimen. Note: If this specific lens is not available, use an objective specifically manufactured for two photon imaging, because it can increase signal resolution dramatically compared with a regular objective.</li>
	<li>Activate the two photon laser using the software (the laser begins to pump and turn on). Tune the laser excitation to 820 nm.</li>
	<li>Using epifluorescence, locate the aorta and focus the objective on the endothelial surface using coarse adjustment.</li>
	<li>Switch the microscope into two photon laser scanning mode, ensuring that the excitation laser is mode locked, the non-descanned detectors are engaged and the emission filters appropriate to the expected emission spectra are installed. Note: Here, the FV10-MRL/R&#160;(495 to 540 nM) were used.</li>
	<li>Start live scanning using approximately 5% laser power and finely focus the objective in order to visualize the endothelial cells. 
	Note: The endothelial cells will exhibit a strong fluorescent signal when incubated in normal PSS. This will be noticeably weaker when the vessels are incubated in calcium-free buffer. The endothelial cells will be present on the top of the opened aorta and the smooth muscle cells can be seen just below the endothelial cells (see Figure 2). Because blood vessels are neither smooth nor even, there will be places where both smooth muscle cells and endothelial cells are present.</li>
	<li>Once the cells are in focus, program the microscope software to collect sequential images in fast scan mode (raster scan, 512 x 512 pixel window with a frame collection frequency of 1.1 s). In parallel with Fluo-4 AM fluorescence, collect transmitted light images in order to detect changes in vessel contraction and better visualize the experimental conditions.</li>
	<li>After collection of baseline signal images, change the Ca2+ ion concentration in the external solution or slowly apply pharmacological stimulus agents using the peristaltic pump while imaging. Observe the fluorescent signal increase within the loaded cells. 
	Note: Endothelial cells respond to changes in flow, thus it is recommended to use low laminar applications and vehicle testing before application of pharmacological activators of Ca2+ or NO signaling. To recalculate intracellular calcium to nM concentration values in vessels loaded with Fluo-4 (dissociation constant for Fluo-4 is 345 nM), fluorescence intensity could be recorded at baseline and after addition of ionomycin and MnCl2.4</li>
</ol>
4. Image Processing and Calculations
<ol>
	<li>Download and install Fiji image processing package.</li>
	<li>Open the image file in Fiji. Upon importing the file, split the channels (transmitted light and fluorescent signal) when prompted. Use only the fluorescent signal for the data analysis.</li>
	<li>Within the Fiji program, click on the analyze tab and scroll down to the tools option. Under the tools option, find the tab that says ROI manager and click on it; a new window will appear.</li>
	<li>After this, click on set measurements under the analyze tab. Select the specific measurements of interest. For the calcium transient measurements, use the mean gray value option.</li>
	<li>With the circular trace tool, begin to trace the regions of interest (ROI) and click &#8220;add&#8221; on the ROI manager screen for every ROI. Once all cells of interest have been traced, in the ROI manager window, select Multi Measure under the &#8220;more&#8221; tab. Remember to either save the measurements directly or copy and paste all of these measurements into a spreadsheet.</li>
	<li>Open *.txt file or Excel spreadsheet from Fiji and transfer the numbers to a new Origin worksheet. Note: Alternatively, use any program like Sigma Plot or Prism for further analysis.</li>
	<li>Within the Origin program, use Plot &#8594; Line+Symbol menu to observe an overview of all transient responses. Deselect the unresponsive cells.</li>
	<li>Recalculate trace number to time scale (X axis), use Column &#8594; Set Column Values and multiply the trace number column to the image collection frequency (in our case 1.1s).</li>
	<li>Use Analysis &#8594; Statistics on Rows for all selected recordings to calculate Mean (Y axis) and Standard Error trace. Plot final Graph for current group of cells Plot &#8594; Line + Symbol.</li>
	<li>The mean calcium transient calculation is described as followed.
	<ol>
		<li>For total calcium release within the Origin program, click on Graph, then use menu Analysis &#8594; Calculus &#8594; Integrate. Total integral of area under curve appears in Result Log.</li>
		<li>For transient kinetics,&#160;click on Graph, then use menu: Analysis &#8594;&#160;Non-linear Curve Fit &#8594;&#160;Select Data Set (choose X axis range from maximum to end of transient response). Start Fitting&#160;&#8594;&#160;Select Function &#8594;&#160;Exponential Decay 1 &#8594;&#160;Done. 
		Note: Exponential fitting appears in Graph window and Result Log. Obtained data (values) represent total amount of calcium released, and kinetics of the channels mediated the transient response.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

Experimental Overview. To better understand the contribution of calcium and NO to vascular physiology, a novel method was developed for measuring [Ca2+]i and NO within smooth muscle and endothelial cells of isolated intact aortas. Together, this protocol consists of these critical steps: 1) Mechanical isolation and preparation (not enzymatic digestion) of the vessel. It is important to keep the tissue healthy and intact as much as possible to obtain optimal physiological recordings. 2) Incu...

Calcium is a fundamental second messenger within vascular cells such as endothelial and smooth muscle cells. It is the primary stimulus for vascular contraction and plays a major role in vascular dilation, including its effects through NO generation within the endothelium. Due to limitations of imaging technologies, it has been virtually impossible to observe calcium handling within the intact vessel. The development of two photon imaging systems and the creation of new calcium or NO labeling dyes, makes it possible to image at a sufficient depth and resolution to begin to understand calcium dynamics and NO production within the vasculature.
Two photon microscopy has recently been applied in&#160;tissue, organs and even whole animal studies because of its superior ability to deeply penetrate tissues with low background fluorescence and high signal sensitivity.1,2 The narrow spectrum of two photon excitation at the illumination focal point and the use of non-descanned detectors are the reasons why two photon microscopy is superior to traditional confocal microscopy. Confocal microscopy cannot produce high-quality images at the necessary tissue depth due to the auto-fluorescence and the scattering of out-of-focus light into the confocal pinhole. Consequently, we have developed a method using a two photon microscope to measure [Ca2+]i signaling and NO production in intact, individual blood vessel cells with high resolution and a low signal-to-noise ratio.&#160;

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>DAF-FM</td>
			<td>Life Technologies</td>
			<td>D-23842</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluo 4 AM</td>
			<td>Life Technologies</td>
			<td>F14217</td>
			<td>500&#181;l in DMSO</td>
		</tr>
		<tr>
			<td>Pluronic F-68 solution</td>
			<td>Sigma-Aldrich</td>
			<td>P5556</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Name</td>
			<td>Tocris</td>
			<td>0665</td>
			<td></td>
		</tr>
		<tr>
			<td>Olympus upright microscope</td>
			<td>Olympus</td>
			<td>Fluoview FV1000</td>
			<td></td>
		</tr>
		<tr>
			<td>MaiTai HP DeepSee-OL&#160;</td>
			<td>Spectra Physics</td>
			<td></td>
			<td>Ti:sapphire laser 690nm &#8212; 1040nm</td>
		</tr>
		<tr>
			<td>Filters</td>
			<td>Olympus</td>
			<td>FV10-MRL/R&#160;</td>
			<td>495 to 540 nm&#160;</td>
		</tr>
		<tr>
			<td>25&#215; water-immersion objective lens</td>
			<td>Olympus</td>
			<td>XLPL25XWMP</td>
			<td>N.A. 1.05 and working distance 2 mm</td>
		</tr>
		<tr>
			<td>Slice Anchor grid&#160;</td>
			<td>Warner Instrument&#160;</td>
			<td>SHD-27LH</td>
			<td></td>
		</tr>
		<tr>
			<td>Other basic reagents&#160;</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

two-photon imaging of intracellular ca2+ handling and nitric oxide production in endothelial and smooth muscle cells of an isolated rat aorta

Calcium is a very important regulator of many physiological processes in vascular tissues. Most endothelial and smooth muscle functions highly depend on changes in intracellular calcium ([Ca2+]i) and nitric oxide (NO). In order to understand how [Ca2+]i, NO and downstream molecules are handled by a blood vessel in response to vasoconstrictors and vasodilators, we developed a novel technique that applies calcium-labeling (or NO-labeling) dyes with two photon microscopy to measure calcium handling (or NO production) in isolated blood vessels. Described here is a detailed step-by-step procedure that demonstrates how to isolate an aorta from a rat, label calcium or NO within the endothelial or smooth muscle cells, and image calcium transients (or NO production) using a two photon microscope following physiological or pharmacological stimuli. The benefits of using the method are multi-fold: 1) it is possible to simultaneously measure calcium transients in both endothelial cells and smooth muscle cells in response to different stimuli; 2) it allows one to image endothelial cells and smooth muscle cells in their native setting; 3) this method is very sensitive to intracellular calcium or NO changes and generates high resolution images for precise measurements; and 4) described approach can be applied to the measurement of other molecules, such as reactive oxygen species. In summary, application of two photon laser emission microscopy to monitor calcium transients and NO production in the endothelial and smooth muscle cells of an isolated blood vessel has provided high quality quantitative data and promoted our understanding of the mechanisms regulating vascular function.

In order to accurately assess the contribution of calcium to vascular physiology (vasodilation and vasoconstriction), a protocol was designed to load calcium dyes into both endothelial cells and smooth muscle cells in isolated intact aortae. The general experimental set up depicted in Figure 1, shows the basic strategy for isolation and preparation of the vessel before imaging. Briefly, after isolation of the aorta from the rat, it should be cleaned of fat and connective tissue and slit longitudinally. T...

Watch this Scientific Journal Video about Two-photon Imaging of Intracellular Ca2+ Handling and Nitric Oxide Production in Endothelial and Smooth Muscle Cells of an Isolated Rat Aorta at JoVE.com

Two-photon Imaging of Intracellular Ca2+ Handling and Nitric Oxide Production in Endothelial and Smooth Muscle Cells of an Isolated Rat Aorta

Vascular cell functiondepends on activity of intracellular messengers. Described here is an ex vivo two photon imaging method that allows the measurement of intracellular calcium and nitric oxide levels in response to physiological and pharmacological stimuli in individual endothelial and smooth muscle cells of an isolated aorta.

Two-photon Imaging of Intracellular Ca2+ Handling and Nitric Oxide Production in Endothelial and Smooth Muscle Cells of an Isolated Rat Aorta

Calcium is a very important regulator of many physiological processes in vascular tissues. Most endothelial and smooth muscle functions highly depend on ...

two-photon-imaging-intracellular-ca2-handling-nitric-oxide-production

Research

JoVE Journal

Biology

11.2K vues.  Medical College of Wisconsin. Vascular cell functiondepends on activity of intracellular messengers. Described here is an ex vivo two photon imaging method that allows the measurement of intracellular calcium and nitric oxide levels in response to physiological and pharmacological stimuli in individual endothelial and smooth muscle cells of an isolated aorta. 

Vidéo: Two-photon Imaging of Intracellular Ca2+ Handling and Nitric Oxide Production in Endothelial and Smooth Muscle Cells of an Isolated Rat Aorta

Two-photon axotomy and time-lapse confocal imaging in live zebrafish embryos

Zebrafish have long been utilized to study the cellular and molecular mechanisms of development by time-lapse imaging of the living transparent embryo. Here we describe a method to mount zebrafish embryos for long-term imaging and demonstrate how to automate the capture of time-lapse images using a confocal microscope. We also describe a method to create controlled, precise damage to individual branches of peripheral sensory axons in zebrafish using the focused power of a femtosecond laser mounted on a two-photon microscope. The parameters for successful two-photon axotomy must be optimized for each microscope. We will demonstrate two-photon axotomy on both a custom built two-photon microscope and a Zeiss 510 confocal/two-photon to provide two examples.

Zebrafish trigeminal sensory neurons can be visualized in a transgenic line expressing GFP driven by a sensory neuron specific promoter 1. We have adapted this zebrafish trigeminal model to directly observe sensory axon regeneration in living zebrafish embryos. Embryos are anesthetized with tricaine and positioned within a drop of agarose as it solidifies. Immobilized embryos are sealed within an imaging chamber filled with phenylthiourea (PTU) Ringers. We have found that embryos can be continuously imaged in these chambers for 12-48 hours. A single confocal image is then captured to determine the desired site of axotomy. The region of interest is located on the two-photon microscope by imaging the sensory axons under low, non-damaging power. After zooming in on the desired site of axotomy, the power is increased and a single scan of that defined region is sufficient to sever the axon. Multiple location time-lapse imaging is then set up on a confocal microscope to directly observe axonal recovery from injury.

Here we describe a method for mounting zebrafish embryos for long-term imaging, two-photon imaging and tissue-damage techniques, and time-lapse confocal imaging.

Zebrafish have long been utilized to study the cellular and molecular mechanisms of development by time-lapse imaging of the living transparent embryo.  ...

Focal Ca2+ Transient Detection in Smooth Muscle

Ca2+ imaging of smooth muscle provides insight into cellular mechanisms that may not result in changes of membrane potential, such as the release of Ca2+ from internal stores, and allows multiple cells to be monitored simultaneously to assess, for example, coupling in syncytial tissue. Subcellular Ca2+ transients are common in smooth muscle, yet are difficult to measure accurately because of the problems caused by their stochastic occurrence, over an often wide field of view, in an organ that it prone to contract. To overcome this problem, we've developed a series of imaging protocols and analysis routines to acquire and then analyse, in an automated fashion, the frequency, location and amplitude of such events. While this approach may be applied in other contexts, our own work involves the detection of local purinergic Ca2+ transients for locating transmitter release with submicron resolution. 
ATP is released as a cotransmitter from autonomic nerves, where it binds to P2X1 receptors on the smooth muscle of the detrusor and vas deferens. Ca2+ enters the smooth muscle, resulting in purinergic neuroeffector Ca2+ transients (NCTs). The focal Ca2+ transients allow the optical monitoring of neurotransmitter release in a manner that has many advantages over electrophysiology. Apart from the greatly improved spatial resolution, optical recording has the additional advantage of allowing the recording of transmitter release from many distinguishable sites simultaneously. Furthermore, the optical plane of focus is easier to maintain or correct during long recording series than is the repositioning of an intracellular sharp microelectrode. 
In summary, a method for imaging of Ca2+ fluorescence is outlined which details the preparation of tissue, and the acquisition and analysis of data. We outline the use of several scripts for the analysis of such Ca2+ transients.

Focal Ca2+ Transient Detection in Smooth Muscle

Details methods for high-resolution Ca2+ imaging of smooth muscle within isolated organs, including: preparation of the tissue, image acquisition and data analysis.

Ca2+ imaging of smooth muscle provides insight into cellular mechanisms that may not result in changes of membrane potential, such as the release of Ca2+ ...

Isolation of Human Umbilical Arterial Smooth Muscle Cells (HUASMC)

The human umbilical cord (UC) is a biological sample that can be easily obtained just after birth. This biological sample is, most of the time, discarded and their collection does not imply any added risk to the newborn or mother s health. Moreover no ethical concerns are raised. The UC is composed by one vein and two arteries from which both endothelial cells (ECs) 1 and smooth muscle cells (SMCs) 2, two of the main cellular components of blood vessels, can be isolated. In this project the SMCs were obtained after enzymatic treatment of the UC arteries accordingly the experimental procedure previously described by Jaffe et al 3. After cell isolation they were kept in t-flash with DMEM-F12 supplemented with 5% of fetal bovine serum and were cultured for several passages. Cells maintained their morphological and other phenotypic characteristics in the different generations. The aim of this study was to isolate smooth muscle cells in order to use them as models for future assays with constrictor drugs, isolate and structurally characterize L-type calcium channels, to study cellular and molecular aspects of the vascular function 4 and to use them in tissue engineering.

Isolation of Human Umbilical Arterial Smooth Muscle Cells HUASMC

The umbilical cords are used to isolate smooth muscle cells by different ways. In this work we used the enzymatic treatment to isolated smooth muscle cells.

The human umbilical cord (UC) is a biological sample that can be easily obtained just after birth. This biological sample is, most of the time, discarded ...

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles

Described here is a method to measure contractility of isolated skeletal muscles. Parameters such as muscle force, muscle power, contractile kinetics, fatigability, and recovery after fatigue can be obtained to assess specific aspects of the excitation-contraction coupling (ECC) process such as excitability, contractile machinery and Ca2+ handling ability. This method removes the nerve and blood supply and focuses on the isolated skeletal muscle itself. We routinely use this method to identify genetic components that alter the contractile property of skeletal muscle though modulating Ca2+ signaling pathways. Here, we describe a newly identified skeletal muscle phenotype, i.e., mechanic alternans, as an example of the various and rich information that can be obtained using the in vitro muscle contractility assay. Combination of this assay with single cell assays, genetic approaches and biochemistry assays can provide important insights into the mechanisms of ECC in skeletal muscle.

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles

We describe a method to directly measure muscle force, muscle power, contractile kinetics and fatigability of isolated skeletal muscles in an in vitro system using field stimulation. Valuable information on Ca2+ handling properties and contractile machinery of the muscle can be obtained using different stimulating protocols.

 
Described here is a method to measure contractility of isolated skeletal muscles. Parameters such as muscle force, muscle power, contractile kinetics, ...

Measurement of Smooth Muscle Function in the Isolated Tissue Bath-applications to Pharmacology Research

Isolated tissue bath assays are a classical pharmacological tool for evaluating concentration-response relationships in a myriad of contractile tissues. While this technique has been implemented for over 100 years, the versatility, simplicity and reproducibility of this assay helps it to remain an indispensable tool for pharmacologists and physiologists alike. Tissue bath systems are available in a wide array of shapes and sizes, allowing a scientist to evaluate samples as small as murine mesenteric arteries and as large as porcine ileum &#8211; if not larger. Central to the isolated tissue bath assay is the ability to measure concentration-dependent changes to isometric contraction, and how the efficacy and potency of contractile agonists can be manipulated by increasing concentrations of antagonists or inhibitors. Even though the general principles remain relatively similar, recent technological advances allow even more versatility to the tissue bath assay by incorporating computer-based data recording and analysis software. This video will demonstrate the function of the isolated tissue bath to measure the isometric contraction of an isolated smooth muscle (in this case rat thoracic aorta rings), and share the types of knowledge that can be created with this technique. Included are detailed descriptions of aortic tissue dissection and preparation, placement of aortic rings in the tissue bath and proper tissue equilibration prior to experimentation, tests of tissue viability, experimental design and implementation, and data quantitation. Aorta will be connected to isometric force transducers, the data from which will be captured using a commercially available analog-to-digital converter and bridge amplifier specifically designed for use in these experiments. The accompanying software to this system will be used to visualize the experiment and analyze captured data.

This protocol describes the measurement of isometric contraction in an isolated smooth muscle preparation, using an isolated tissue bath system and computer-based data acquisition.

Isolated tissue bath assays are a classical pharmacological tool for evaluating concentration-response relationships in a myriad of contractile tissues.  ...

Imaging Local Ca2+ Signals in Cultured Mammalian Cells

Cytosolic Ca2+ ions regulate numerous aspects of cellular activity in almost all cell types, controlling processes as wide-ranging as gene transcription, electrical excitability and cell proliferation. The diversity and specificity of Ca2+ signaling derives from mechanisms by which Ca2+ signals are generated to act over different time and spatial scales, ranging from cell-wide oscillations and waves occurring over the periods of minutes to local transient Ca2+ microdomains (Ca2+ puffs) lasting milliseconds. Recent advances in electron multiplied CCD (EMCCD) cameras now allow for imaging of local Ca2+ signals with a 128 x 128 pixel spatial resolution at rates of &#62;500 frames sec-1 (fps). This approach is highly parallel and enables the simultaneous monitoring of hundreds of channels or puff sites in a single experiment. However, the vast amounts of data generated (ca. 1 Gb per min) render visual identification and analysis of local Ca2+ events impracticable. Here we describe and demonstrate the procedures for the acquisition, detection, and analysis of local IP3-mediated Ca2+ signals in intact mammalian cells loaded with Ca2+ indicators using both wide-field epi-fluorescence (WF) and total internal reflection fluorescence (TIRF) microscopy. Furthermore, we describe an algorithm developed within the open-source software environment Python that automates the identification and analysis of these local Ca2+ signals. The algorithm localizes sites of Ca2+ release with sub-pixel resolution; allows user review of data; and outputs time sequences of fluorescence ratio signals together with amplitude and kinetic data in an Excel-compatible table.

Imaging Local Ca2+ Signals in Cultured Mammalian Cells

Here we present techniques for imaging local IP3-mediated Ca2+ events using fluorescence microscopy in intact mammalian cells loaded with Ca2+ indicators together with an algorithm that automates identification and analysis of these events.

Cytosolic Ca2+ ions regulate numerous aspects of cellular activity in almost all cell types, controlling processes as wide-ranging as gene transcription, ...

En Face Detection of Nitric Oxide and Superoxide in Endothelial Layer of Intact Arteries

Endothelium-derived nitric oxide (NO) produced from endothelial NO-synthase (eNOS) is one of the most important vasoprotective molecules in cardiovascular physiology. Dysfunctional eNOS such as uncoupling of eNOS leads to decrease in NO bioavailability and increase in superoxide anion (O2.&#8722;) production, and in turn promotes cardiovascular diseases. Therefore, appropriate measurement of NO and O2.&#8722; levels in the endothelial cells are pivotal for research on cardiovascular diseases and complications. Because of the extremely labile nature of NO and O2.&#8722;, it is difficult to measure NO and O2.&#8722; directly in a blood vessel. Numerous methods have been developed to measure NO and O2.&#8722; production. It is, however, either insensitive, or non-specific, or technically demanding and requires special equipment. Here we describe an adaption of the fluorescence dye method for en face simultaneous detection and visualization of intracellular NO and O2.&#8722; using the cell permeable diaminofluorescein-2 diacetate (DAF-2DA) and dihydroethidium (DHE), respectively, in intact aortas of an obesity mouse model induced by high-fat-diet feeding. We could demonstrate decreased intracellular NO and enhanced O2.&#8722; levels in the freshly isolated intact aortas of obesity mouse as compared to the control lean mouse. We demonstrate that this method is an easy technique for direct detection and visualization of NO and O2.&#8722; in the intact blood vessels and can be widely applied for investigation of endothelial (dys)function under (physio)pathological conditions.

En Face Detection of Nitric Oxide and Superoxide in Endothelial Layer of Intact Arteries

In this article we describe an adapted relatively easy method using the fluorescence dye diaminofluorescein-2 diacetate (DAF-2DA) and dihydroethidium (DHE) for en face simultaneous detection and visualization of intracellular nitric oxide (NO) and superoxide anion (O2.&#8722;) respectively, in freshly isolated intact aortas of an obesity mouse model.

Endothelium-derived nitric oxide (NO) produced from endothelial NO-synthase (eNOS) is one of the most important vasoprotective molecules in cardiovascular ...

Isolation of Murine Coronary Vascular Smooth Muscle Cells

While the isolation and culture of vascular smooth muscle cells (VSMCs) from large vessels is well established, we sought to isolate and culture VSMCs from the coronary circulation. Hearts with intact aortic arches were removed and perfused via retrograde Langendorff with digestion solution containing 300 Units/ml of collagenase type II, 0.1 mg/ml soybean trypsin inhibitor and 1 M CaCl2. The perfusates were collected at 15 min intervals for 90 min, pelleted by centrifugation, resuspended in plating media, and plated on tissue culture dishes. VSMCs were characterized by presence of SM22&#945;, &#945;-SMA, and vimentin. One of the main advantages of using this technique is the ability to isolate VSMCs from the coronary circulation of mice. Although the small number of cells obtained can limit some of the applications for which the cells can be utilized, isolated coronary VSMCs can be used in a variety of well-established cell culture techniques and assays. Studies investigating VSMCs from genetically modified mice can provide further information about structure-function and signaling processes associated with vascular pathologies.

The purpose of this protocol is to demonstrate the isolation and culture techniques of murine primary vascular smooth muscle cells (VSMCs) from the coronary circulation. Once VSMCs have been isolated, they can be used for many standard culture techniques.

While the isolation and culture of vascular smooth muscle cells (VSMCs) from large vessels is well established, we sought to isolate and culture VSMCs ...

Development and Characterization of In Vitro Microvessel Network and Quantitative Measurements of Endothelial [Ca2+]i and Nitric Oxide Production

Endothelial cells (ECs) lining the blood vessel walls in vivo are constantly exposed to flow, but cultured ECs are often grown under static conditions and exhibit a pro-inflammatory phenotype. Although the development of microfluidic devices has been embraced by engineers over two decades, their biological applications remain limited. A more physiologically relevant in vitro microvessel model validated by biological applications is important to advance the field and bridge the gaps between in vivo and in vitro studies. Here, we present detailed procedures for the development of cultured microvessel network using a microfluidic device with a long-term perfusion capability. We also demonstrate its applications for quantitative measurements of agonist-induced changes in EC [Ca2+]i and nitric oxide (NO) production in real time using confocal and conventional fluorescence microscopy. The formed microvessel network with continuous perfusion showed well-developed junctions between ECs. VE-cadherin distribution was closer to that observed in intact microvessels than statically cultured EC monolayers. ATP-induced transient increases in EC [Ca2+]i and NO production were quantitatively measured at individual cell levels, which validated the functionality of the cultured microvessels. This microfluidic device allows ECs to grow under a well-controlled, physiologically relevant flow, which makes the cell culture environment closer to in vivo than that in the conventional, static 2D cultures. The microchannel network design is highly versatile, and the fabrication process is simple and repeatable. The device can be easily integrated to the confocal or conventional microscopic system enabling high resolution imaging. Most importantly, because the cultured microvessel network can be formed by primary human ECs, this approach will serve as a useful tool to investigate how pathologically altered blood components from patient samples affect human ECs and provide insight into clinical issues. It also can be developed as a platform for drug screening.

Development and Characterization of In Vitro Microvessel Network and Quantitative Measurements of Endothelial [Ca2+]i and Nitric Oxide Production

Primary human umbilical vein endothelial cells (HUVECs) were grown to confluence within a microfluidic network device. The endothelial cell junction and F-actin distributions were illustrated and the changes in intracellular calcium concentration and nitric oxide production in response to adenosine triphosphate (ATP) were quantified in real-time at individual cell levels.

Endothelial cells (ECs) lining the blood vessel walls in vivo are constantly exposed to flow, but cultured ECs are often grown under static conditions and ...

Murine Aortic Crush Injury: An Efficient In Vivo Model of Smooth Muscle Cell Proliferation and Endothelial Function

Arterial reconstruction, whether angioplasty or bypass surgery, involves iatrogenic trauma causing endothelial disruption and vascular smooth muscle cell (VSMC) proliferation. Common murine models study small vessels such as the carotid and femoral arteries. Herein we describe an in vivo system in which both VSMC proliferation and endothelial barrier function can be simultaneously assessed in a large vessel. We studied the infrarenal aortic response to injury in C57BL/6 mice. The aorta was injured from the left renal vein to the aortic bifurcation by 30 transmural crushes of 5-seconds duration with a cotton-tipped applicator. Morphological changes were assessed with conventional histology. Aorta wall thickness was measured from the luminal surface to the adventitia. EdU integration and counter staining with DAPI and alpha-actin was used to demonstrate VSMC proliferation. Activation of ERK1/2, a known moderator of intimal hyperplasia formation, was determined by Western Blot analysis. The effect of inflammation was determined by immunohistochemistry for B-cells, T-cells, and macrophages. En face sections of endothelium were visualized with scanning electron microscopy (SEM). Endothelial barrier function was determined with Evans Blue staining. Transmural injury resulted in aortic wall thickening. This injury induced VSMC proliferation, most prominently at 3 days after injury, and early activation of ERK1/2 and decreased p27kip1 expression. Injury did not result in increased B-cells, T-cells, or macrophages infiltration in the vessel wall. Injury caused partial endothelial cell denudation and loss of cell-cell contact. Injury resulted in a significant loss of endothelial barrier function, which returned to baseline after seven days. The murine transmural blunt aortic injury model provides an efficient system to simultaneously study both VSMC proliferation and endothelial barrier function in a large vessel.

Murine Aortic Crush Injury: An Efficient In Vivo Model of Smooth Muscle Cell Proliferation and Endothelial Function

Restenosis following cardiovascular procedures (bypass surgery, angioplasty, or stenting) is a significant problem reducing the durability of these procedures. An ideal therapy would inhibit smooth muscle cell (VSMC) proliferation while promoting regeneration of the endothelium. We describe a model for simultaneous assessment of VSMC proliferation and endothelial function in vivo.

Arterial reconstruction, whether angioplasty or bypass surgery, involves iatrogenic trauma causing endothelial disruption and vascular smooth muscle cell ...