Name: labeling of blood vessels in the teleost brain and pituitary using cardiac perfusion with a dii-fixative
Uploaded: 2019-06-13T14:45:00
Description: Watch this Scientific Journal Video about Labeling of Blood Vessels in the Teleost Brain and Pituitary Using Cardiac Perfusion with a DiI-fixative at JoVE.com

We thank Dr Shinji Kanda for demonstration of cardiac perfusion with fixative solution in medaka, Ms Lourdes Carreon G Tan for help with medaka husbandry, and Mr Anthony Peltier for illustrations. This work was funded by NMBU and by the Research Council of Norway, grant number 248828 (Digital Life Norway program).

All animal handling was performed according to the recommendations for the care and welfare of research animals at the Norwegian University of Life Sciences, and under the supervision of authorized investigators.
1. Preparation of Instruments and Solutions
<ol>
	<li>Prepare DiI stock solution dissolving 5 mg of DiI crystal in 1.5 mL plastic tube with 1 mL of 96 % EtOH. Vortex for 30 s and keep covered using aluminum foil. 
	NOTE: The DiI stock solution can be conserved ...

<ol>
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Cardiac perfusion with DiI previously has been used to label blood vessels in several model species24, including teleost fish13.
As DiI is directly delivered to the endothelial cell membrane by perfusion in the vasculature, it is possible to increase the signal-to-noise ratio by increasing the DiI concentration in the fixative solution. In addition, the fluorophore provides intense staining when excited with minimal bleaching allowing ...

Blood vessels play an essential part of the vertebrate body as they provide the necessary nutrients, oxygen and hormonal signals to all organs. Also, since the discovery of their involvement in cancer development1, they have received much attention in clinical research. Although a number of publications have investigated the mechanisms allowing blood vessel growth and morphogenesis, and a large number of genes important for their formation have been identified2, a lot remains to be understood regarding the interaction between cells or tissues and the circulating blood.
Visualization of blood vasculature in the brain and pituitary is important. Neurons in the brain require a high supply of oxygen and glucose3, and the pituitary contains up to eight important hormone-producing cell types that use the blood flow to receive signal from the brain and send their respective hormones to different peripheral organs4,5. While in mammals, the portal system at the base of the hypothalamus named the median eminence, links the brain and the pituitary6, such a clear blood bridge has not been described in teleost fish. Indeed, in teleosts, preoptico-hypothalamic neurons directly project their axons into the pars nervosa of the pituitary7 and mostly innervate the different endocrine cell types directly8,9. However, some of these neurons have their nerve endings located in the extravascular space, in close vicinity to blood capillaries10. Therefore, the difference between teleost fish and mammals is not so clear, and the relationship between the blood vasculature and the brain and pituitary cells requires greater investigation in teleost fish.
Zebrafish has, in many aspects, an anatomically and functionally comparable vascular system to other vertebrate species11. It has become a powerful vertebrate model for cardiovascular research mostly thanks to the development of several transgenic lines where components of the vascular system are labeled with fluorescent reporter proteins12. However, exact circulatory system anatomy may vary between species, or even between two individuals belonging to the same species. Therefore, visualization of blood vessels may be of high interest also in other teleost species for which transgenesis tools do not exist.
Several techniques have been described to label blood vessels in both mammals and teleosts. These include in situ hybridization for vasculature-specific genes, alkaline phosphatase staining, microangiography, and dye injections (for a review see13). Fluorescent lipophilic cationic indocarbocyanine dye (DiI) was first used to study membrane lipids lateral mobility as it is retained in the lipid bilayers and can migrate through it14,15,16. Indeed, a molecule of DiI is composed of two hydrocarbon chains and chromophores. While the hydrocarbon chains integrate in the lipid bilayer cell membrane of the cells in contact with it, the chromophores remain on its surface17. Once in the membrane, DiI molecules diffuse laterally within the lipid bilayer which helps to stain membrane structures that are not in direct contact with the DiI solution. Injecting a DiI solution through cardiac perfusion, will therefore label all endothelial cells in contact with the compound allowing direct labelling of the blood vessels. Today DiI is also used for other staining purposes, such as single molecule imaging, fate mapping, and neuronal tracing. Interestingly, several fluorophores exist (with different wavelengths of emission) allowing the combination with other fluorescent labels, and the incorporation as well as the lateral diffusion of DiI can occur in both live and fixed tissues18,19.
Formaldehyde, discovered by Ferdinand Blum in 1893, has been used widely to the present day as the preferred chemical for tissue fixation20,21. It shows broad specificity for most cellular targets and preserves the cellular structure22,23. It also preserves the fluorescent properties of most fluorophores, and thus can be used to fixate transgenic animals for which targeted cells express fluorescent reporter proteins.
In this manuscript, a previous protocol developed to label blood vessels in small experimental mammalian models24&#160;has been adapted to the use in fish. The entire procedure takes only a couple of hours to perform. It demonstrates how to perfuse a fixative solution of formaldehyde containing DiI in the fish heart in order to directly label all blood vessels in the brain and the pituitary of the model fish medaka. Medaka is a small freshwater fish native to Asia, primarily found in Japan. It is a research model organism with a suite of molecular and genetic tools available25. Therefore, identification of blood vessels in this species as well as in others will allow to improve our understanding on how the brain and pituitary cells interact with blood vasculature in whole tissue or thick tissue slices.

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			<td height="21" style="height:21px;width:432px;">16% paraformaldehyde</td>
			<td style="width:171px;">Electron Microscopy Sciences</td>
			<td style="width:123px;">RT 15711</td>
			<td style="width:152px;"></td>
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			<td height="21" style="height:21px;width:432px;">5 mL Syringe PP/PE without needle</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:123px;">Z116866-100EA</td>
			<td style="width:152px;">syringes</td>
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		<tr height="42">
			<td height="42" style="height:42px;width:432px;">BD Precisionglide syringe needles</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:123px;">Z118044-100EA</td>
			<td style="width:152px;">needles 18G (1.20*40)</td>
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			<td height="21" style="height:21px;width:432px;">borosilicate glass 10cm OD1.2mm</td>
			<td style="width:171px;">sutter instrument</td>
			<td style="width:123px;">BF120-94-10</td>
			<td style="width:152px;">glass pipette</td>
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			<td height="21" style="height:21px;width:432px;">DiI (1,1&#8242;-Dioctadecyl-3,3,3&#8242;,3&#8242;-tetramethylindocarbocyanine perchlorate)</td>
			<td style="width:171px;">Invitrogen</td>
			<td style="width:123px;">D-282</td>
			<td style="width:152px;"></td>
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			<td height="42" style="height:42px;width:432px;">LDPE tube O.D 1.7mm and I.D 1.1mm</td>
			<td style="width:171px;">Portex</td>
			<td style="width:123px;">800/110/340/100</td>
			<td style="width:152px;">canula</td>
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			<td height="21" style="height:21px;width:432px;">Phosphate Buffer Saline (PBS) solution</td>
			<td style="width:171px;">Sigma</td>
			<td style="width:123px;">D8537-6X500ML</td>
			<td style="width:152px;"></td>
		</tr>
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			<td height="21" style="height:21px;width:432px;">pipette puller</td>
			<td style="width:171px;">Narishige</td>
			<td style="width:123px;">PC-10</td>
			<td style="width:152px;"></td>
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			<td height="21" style="height:21px;width:432px;">plastic petri dishes</td>
			<td style="width:171px;">VWR</td>
			<td style="width:123px;">391-0442</td>
			<td style="width:152px;"></td>
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			<td height="21" style="height:21px;width:432px;">Super glue gel</td>
			<td style="width:171px;">loctite</td>
			<td style="width:123px;">c4356</td>
			<td style="width:152px;"></td>
		</tr>
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			<td height="21" style="height:21px;width:432px;">tricaine (ms-222)</td>
			<td style="width:171px;">sigma</td>
			<td style="width:123px;">E10521-50G</td>
			<td style="width:152px;"></td>
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labeling of blood vessels in the teleost brain and pituitary using cardiac perfusion with a dii-fixative

Blood vessels innervate all tissues in vertebrates, enabling their survival by providing the necessary nutrients, oxygen, and hormonal signals. It is one of the first organs to start functioning during development. Mechanisms of blood vessel formation have become a subject of high scientific and clinical interest. In adults however, it is difficult to visualize the vasculature in most living animals due to their localization deep within other tissues. Nevertheless, visualization of blood vessels remains important for several studies such as endocrinology and neurobiology. While several transgenic lines have been developed in zebrafish, with blood vessels directly visualized through expression of fluorescent proteins, no such tools exist for other teleost species. Using medaka (Oryzias latipes) as a model, the current protocol presents a quick and direct technique to label blood vessels in brain and pituitary by perfusing through the heart with fixative containing DiI. This protocol allows improvement of our understanding on how brain and pituitary cells interact with blood vasculature in whole tissue or thick tissue slices.

This protocol demonstrates a step by step procedure to label blood vessels in the medaka brain and pituitary, and at the same time fix the tissue. After labelling by cardiac injection of a fixative solution containing DiI into the heart, blood vessels can be observed on slices using a fluorescent stereomicroscope (Figure 4) or on whole tissue using a confocal microscope (Figure 5). Either on the thick tissue slice or on the whole tissue, the architecture of the ...

Watch this Scientific Journal Video about Labeling of Blood Vessels in the Teleost Brain and Pituitary Using Cardiac Perfusion with a DiI-fixative at JoVE.com

Labeling of Blood Vessels in the Teleost Brain and Pituitary Using Cardiac Perfusion with a DiI-fixative

The article describes a quick protocol for labeling blood vessels in a teleost fish by cardiac perfusion of DiI diluted in fixative, using medaka (Oryzias latipes) as a model and focusing on brain and pituitary tissue.

Blood vessels innervate all tissues in vertebrates, enabling their survival by providing the necessary nutrients, oxygen, and hormonal signals. It is one ...

The overall goal of this procedure is to label blood vessels in the brain and pituitary of teleost fish, and we use cardiac perfusion with a fixative containing DiI in the model species medaka. So this technique which is simple and efficient will help answer important questions regarding the vascular anatomy in the brain and pituitary of teleost fish as well as the relationship between neurons or endocrine cells and blood vessels. Some advantages of this technique include a fast and easy simple preparation, and its adaptability to the teleost fish species.To prepare a fish holder, cut a piece of polystyrene to a five centimeter length, a three centimeter width, and a two centimeter thickness, and glue the polystyrene to a nine centimeter diameter plastic dish. Then use a scalpel to make a three centimeter boat shaped hole in the polystyrene. To prepare the perfusion system, add a 30 to 50 centimeter long plastic cannula at the extremity of the perfusion system needle.To prepare five centimeter glass pipettes, use a pipette puller to stretch individual glass capillaries according to the manufacturer's instructions. Before beginning the dissection, load a 10 milliliters syringe with the prepared DiI-fixative solution and place a needle with a cannula at the extremity of the syringe. Then use several pieces of tape placed in different orientations to fix the syringe to the bench, and adjust the position of the microscope and the seat to obtain a good position for dissection and for pressing the syringe piston with the elbow.Next, place a euthanized fish in the fish holder abdomen side up and secure the head and tail with pins. Use scissors to horizontally cut the superficial layer of skin to open the anterior abdomen, and use forceps to remove the skin above the heart until a clear access to the ventricle and the bulbus arteriosus is achieved. Add a glass pipe at the extremity of the capillary and break the tip of the pipette.Bring the glass pipe close to the ventricle and add elbow pressure to the syringe piston to force the liquid out while pinning the heart ventricle with the pipette. Then immediately perforate the sinus venosus with forceps to release the blood from circulation. From the ventricle, adjust the angle of the glass pipette to locate the entrance of the bulbus arteriosus, and move the pipette opening inside the bulbus arteriosus.Then add pressure to the syringe for an additional 30 to 60 seconds while keeping the pipette inside the bulbus arteriosus. For optimal labeling of all the blood vessels it is critical to perfuse into the bulbus arteriosus long enough to replace all the blood with the DiI-fixative solution. After about 60 seconds of perfusion, when no more blood leakage is observed, remove the glass pipette and needles from the fish, and harvest the brain and pituitary into fresh 4%paraformaldehyde for two hours at room temperature in the dark.Then rinse the tissues two times in fresh PBS for 10 minutes per wash before preparing the samples for imaging. After cardiac injection of a fixative solution containing DiI as demonstrated, the labeled blood vessels can be observed on tissue slices by fluorescent stereo microscopy or on whole tissue by confocal microscopy. Note that if the solution is injected in the heart ventricle instead of the bulbus arteriosus or if the solution is injected with too low of a pressure and/or for too short a period, an inadequate labeling of the vessels will be observed.In addition, when imaging the same tissue with the same imaging parameters, a decrease in the labeling intensity can be observed after several days, with the signal appearing more spread-out within the tissue sample. Tissue slices from transgenic lines within which the cells of interest express fluorescent reporter proteins can be further labeled for specific proteins of interest using standard immunofluorescence protocols allowing the investigation of interactions between blood vessels and other cell types. It is important to reach the bulbus arteriosus.When this is achieved, adding pressure to the syringe piston should induce an expansion of the bulbus confirming a successful procedure. This technique can be used to investigate the interaction between endocrine cells and blood vessels in the teleost pituitary in general, but maybe more specifically to investigate possible differences or similarities between the portal systems in teleost and mammals. Because this political use toxic and volatile compounds precautions such as using a gas mask and a ventilated room should always be taken when performing these procedures.

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Research

JoVE Journal

Bioengineering

Anatomical Reconstructions of the Human Cardiac Venous System using Contrast-computed Tomography of Perfusion-fixed Specimens

A detailed understanding of the complexity and relative variability within the human cardiac venous system is crucial for the development of cardiac devices that require access to these vessels. For example, cardiac venous anatomy is known to be one of the key limitations for the proper delivery of cardiac resynchronization therapy (CRT)1 Therefore, the development of a database of anatomical parameters for human cardiac venous systems can aid in the design of CRT delivery devices to overcome such a limitation. In this research project, the anatomical parameters were obtained from 3D reconstructions of the venous system using contrast-computed tomography (CT) imaging and modeling software (Materialise, Leuven, Belgium). The following parameters were assessed for each vein: arc length, tortuousity, branching angle, distance to the coronary sinus ostium, and vessel diameter.
	CRT is a potential treatment for patients with electromechanical dyssynchrony. Approximately 10-20% of heart failure patients may benefit from CRT2. Electromechanical dyssynchrony implies that parts of the myocardium activate and contract earlier or later than the normal conduction pathway of the heart. In CRT, dyssynchronous areas of the myocardium are treated with electrical stimulation. CRT pacing typically involves pacing leads that stimulate the right atrium (RA), right ventricle (RV), and left ventricle (LV) to produce more resynchronized rhythms. The LV lead is typically implanted within a cardiac vein, with the aim to overlay it within the site of latest myocardial activation. 
	We believe that the models obtained and the analyses thereof will promote the anatomical education for patients, students, clinicians, and medical device designers. The methodologies employed here can also be utilized to study other anatomical features of our human heart specimens, such as the coronary arteries. To further encourage the educational value of this research, we have shared the venous models on our free access website: <a href="http://www.vhlab.umn.edu/atlas" target="_blank">www.vhlab.umn.edu/atlas</a>.

The objective of this research is to recreate and then access the anatomy of the human cardiac venous system using 3D reconstructions generated from contrast-computed tomography scans.

A detailed  understanding of the complexity and relative variability within the human  cardiac venous system is crucial for the development of cardiac ...

Improved Method for the Preparation of a Human Cell-based, Contact Model of the Blood-Brain Barrier

The blood-brain barrier (BBB) comprises impermeable but adaptable brain capillaries which tightly control the brain environment. Failure of the BBB has been implied in the etiology of many brain pathologies, creating a need for development of human in vitro BBB models to assist in clinically-relevant research. Among the numerous BBB models thus far described, a static (without flow), contact BBB model, where astrocytes and brain endothelial cells (BECs) are cocultured on the opposite sides of a porous membrane, emerged as a simplified yet authentic system to simulate the BBB with high throughput screening capacity. Nevertheless the generation of such model presents few technical challenges. Here, we describe a protocol for preparation of a contact human BBB model utilizing a novel combination of primary human BECs and immortalized human astrocytes. Specifically, we detail an innovative method for cell-seeding on inverted inserts as well as specify insert staining techniques and exemplify how we use our model for BBB-related research.

Establishment of human models of the blood-brain barrier (BBB) can benefit research into brain conditions associated with BBB failure. We describe here an improved technique for preparation of a contact BBB model, which permits coculturing of human astrocytes and brain endothelial cells on the opposite sides of a porous membrane.

The blood-brain barrier (BBB) comprises impermeable but adaptable brain capillaries which tightly control the brain environment. Failure of the BBB has ...

Generation and Grafting of Tissue-engineered Vessels in a Mouse Model

The construction of vascular conduits is a fundamental strategy for surgical repair of damaged and injured vessels resulting from cardiovascular diseases. The current protocol presents an efficient and reproducible strategy in which functional tissue engineered vessel grafts can be generated using partially induced pluripotent stem cell (PiPSC) from human fibroblasts. We designed a decellularized vessel scaffold bioreactor, which closely mimics the matrix protein structure and blood flow that exists within a native vessel, for seeding of PiPSC-endothelial cells or smooth muscle cells prior to grafting into mice. This approach was demonstrated to be advantageous because immune-deficient mice engrafted with the PiPSC-derived grafts presented with markedly increased survival rate 3 weeks after surgery. This protocol represents a valuable tool for regenerative medicine, tissue engineering and potentially patient-specific cell-therapy in the near future.

Here, we present a protocol to generate tissue engineered vessel grafts that are functional for grafting into mice by double seeding partially induced pluripotent stem cell (PiPSC) - derived smooth muscle cells and PiPSC - derived endothelial cells on a decellularized vessel scaffold bioreactor.

The construction of vascular conduits is a fundamental strategy for surgical repair of damaged and injured vessels resulting from cardiovascular diseases. ...

In Vivo Quantitative Assessment of Myocardial Structure, Function, Perfusion and Viability Using Cardiac Micro-computed Tomography

The use of Micro-Computed Tomography (MicroCT) for in vivo studies of small animals as models of human disease has risen tremendously due to the fact that MicroCT provides quantitative high-resolution three-dimensional (3D) anatomical data non-destructively and longitudinally. Most importantly, with the development of a novel preclinical iodinated contrast agent called eXIA160, functional and metabolic assessment of the heart became possible. However, prior to the advent of commercial MicroCT scanners equipped with X-ray flat-panel detector technology and easy-to-use cardio-respiratory gating, preclinical studies of cardiovascular disease (CVD) in small animals required a MicroCT technologist with advanced skills, and thus were impractical for widespread implementation. The goal of this work is to provide a practical guide to the use of the high-speed Quantum FX MicroCT system for comprehensive determination of myocardial global and regional function along with assessment of myocardial perfusion, metabolism and viability in healthy mice and in a cardiac ischemia mouse model induced by permanent occlusion of the left anterior descending coronary artery (LAD).

In Vivo Quantitative Assessment of Myocardial Structure, Function, Perfusion and Viability Using Cardiac Micro-computed Tomography

This method outlines the use of Quantum Micro-Computed Tomography (MicroCT) to assess cardiac morphology, function, perfusion, metabolism and viability with iodinated contrast agent in mice with experimentally-induced myocardial ischemia. The technique can be applied for non-destructive high-throughput longitudinal in vivo imaging of various animal models of human heart disease.

The use of Micro-Computed Tomography (MicroCT) for in vivo studies of small animals as models of human disease has risen tremendously due to the fact that ...

Protocol for MicroRNA Transfer into Adult Bone Marrow-derived Hematopoietic Stem Cells to Enable Cell Engineering Combined with Magnetic Targeting

While CD133+ hematopoietic stem cells (SCs) have been proven to provide high potential in the field of regenerative medicine, their low retention rates after injection into injured tissues as well as the observed massive cell death rates lead to very restricted therapeutic effects. To overcome these limitations, we sought to establish a non-viral based protocol for suitable cell engineering prior to their administration. The modification of human CD133+ expressing SCs using microRNA (miR) loaded magnetic polyplexes was addressed with respect to uptake efficiency and safety as well as the targeting potential of the cells. Relying on our protocol, we can achieve high miR uptake rates of 80&#8211;90% while the CD133+ stem cell properties remain unaffected. Moreover, these modified cells offer the option of magnetic targeting. We describe here a safe and highly efficient procedure for the modification of CD133+ SCs. We expect this approach to provide a standard technology for optimization of therapeutic stem cell effects and for monitoring of the administered cell product via magnetic resonance imaging (MRI).

This protocol illustrates a safe and efficient procedure to modify CD133+ hematopoietic stem cells. The presented non-viral, magnetic polyplex-based approach may provide a basis for the optimization of therapeutic stem cell effects as well as for monitoring the administered cell product via magnetic resonance imaging.

While CD133+ hematopoietic stem cells (SCs) have been proven to provide high potential in the field of regenerative medicine, their low retention rates ...

Lucifer Yellow - A Robust Paracellular Permeability Marker in a Cell Model of the Human Blood-brain Barrier

The blood-brain barrier BBB consists of endothelial cells that form a barrier between the systemic circulation and the brain to prevent the exchange of non-essential ions and toxic substances. Tight junctions (TJ) effectively seal the paracellular space in the monolayers resulting in an intact barrier. This study describes a LY-based fluorescence assay that can be used to determine its apparent permeability coefficient (Papp) and in turn can be used to determine the kinetics of the formation of confluent monolayers and the resulting tight junction barrier integrity in hCMEC/D3 monolayers. We further demonstrate an additional utility of this assay to determine TJ functional integrity in transfected cells. Our data from the LY Papp assay shows that the hCMEC/D3 cells seeded in a transwell setup effectively limit LY paracellular transport 7 days-post culture. As an additional utility of the presented assay, we also demonstrate that the DNA nanoparticle transfection does not alter LY paracellular transport in hCMEC/D3 monolayers.

We present a fluorescence assay to demonstrate that Lucifer Yellow (LY) is a robust marker to determine the apparent paracellular permeability of hCMEC/D3 cell monolayers, an in vitro model of the human blood-brain barrier. We used this assay to determine the kinetics of a confluent monolayer formation in cultured hCMEC/D3 cells.

The blood-brain barrier BBB consists of endothelial cells that form a barrier between the systemic circulation and the brain to prevent the exchange of ...

Intra-cardiac Side-Firing Light Catheter for Monitoring Cellular Metabolism using Transmural Absorbance Spectroscopy of Perfused Mammalian Hearts

Absorbance spectroscopy of cardiac muscle provides non-destructive assessment of cytosolic and mitochondrial oxygenation via myoglobin and cytochrome absorbance respectively. In addition, numerous aspects of the mitochondrial metabolic status such as membrane potential and substrate entry can also be estimated. To perform cardiac wall transmission optical spectroscopy, a commercially available side-firing optical fiber catheter is placed in the left ventricle of the isolated perfused heart as a light source. Light passing through the heart wall is collected with an external optical fiber to perform optical spectroscopy of the heart in near real- time. The transmission approach avoids numerous surface scattering interference occurring in widely used reflection approaches. Changes in transmural absorbance spectra were deconvolved using a library of chromophore reference spectra, providing quantitative measures of all the known cardiac chromophores simultaneously. This spectral deconvolution approach eliminated intrinsic errors that may result from using common dual wavelength methods applied to overlapping absorbance spectra, as well as provided a quantitative evaluation of the goodness of fit. A custom program was designed for data acquisition and analysis, which permitted the investigator to monitor the metabolic state of the preparation during the experiment. These relatively simple additions to the standard heart perfusion system provide a unique insight into the metabolic state of the heart wall in addition to conventional measures of contraction, perfusion, and substrate/oxygen extraction.

Here we introduce a method for using an intra-ventricle optical catheter in perfused hearts to perform absorbance spectroscopy across the heart wall. The data obtained provides robust information on tissue oxygen tension as well as substrate utilization and membrane potential simultaneously with cardiac performance measures in this ubiquitous preparation.

Absorbance spectroscopy of cardiac muscle provides non-destructive assessment of cytosolic and mitochondrial oxygenation via myoglobin and cytochrome ...

Preclinical Cardiac Electrophysiology Assessment by Dual Voltage and Calcium Optical Mapping of Human Organotypic Cardiac Slices

Human cardiac slice preparations have recently been developed as a platform for human physiology studies and therapy testing to bridge the gap between animal and clinical trials. Numerous animal and cell models have been used to examine the effects of drugs, yet these responses often differ in humans. Human cardiac slices offer an advantage for drug testing in that they are directly derived from viable human hearts. In addition to having preserved multicellular structures, cell-cell coupling, and extracellular matrix environments, human cardiac tissue slices can be used to directly test the effect of innumerable drugs on adult human cardiac physiology. What distinguishes this model from other heart preparations, such as whole hearts or wedges, is that slices can be subjected to longer-term culture. As such, cardiac slices allow for studying the acute as well as chronic effects of drugs. Furthermore, the ability to collect several hundred to a thousand slices from a single heart makes this a high-throughput model to test several drugs at varying concentrations and combinations with other drugs at the same time. Slices can be prepared from any given region of the heart. In this protocol, we describe the preparation of left ventricular slices by isolating tissue cubes from the left ventricular free wall and sectioning them into slices using a high precision vibrating microtome. These slices can then either be subjected to acute experiments to measure baseline cardiac electrophysiological function or cultured for chronic drug studies. This protocol also describes dual optical mapping of cardiac slices for simultaneous recordings of transmembrane potentials and intracellular calcium dynamics to determine the effects of the drugs being investigated.

This protocol describes the procedure for sectioning and culturing human cardiac slices for preclinical drug testing and details the use of optical mapping for recording transmembrane voltage and intracellular calcium signals simultaneously from these slices.

Human cardiac slice preparations have recently been developed as a platform for human physiology studies and therapy testing to bridge the gap between ...

Blood Flow Imaging with Ultrafast Doppler

The pulsed-Doppler effect is the main technique used in clinical echography to assess blood flow. Applied with conventional focused ultrasound Doppler modes, it has several limits. Firstly, a finely tuned signal filtering operation is needed to distinguish blood flows from surrounding moving tissues. Secondly, the operator must choose between localizing the blood flows or quantifying them. In the last two decades, ultrasound imaging has undergone a paradigm shift with the emergence of ultrafast ultrasound using unfocused waves. In addition to a hundredfold increase in framerate (up to 10000 Hz), this new technique also breaks the conventional quantification/localization trade-off, offering a complete blood flow mapping of the field of view and a simultaneous access to fine velocities measurements at the single-pixel level (down to 50 &#181;m). This data continuity in both spatial and temporal dimensions strongly improves the tissue/blood filtering process, which results in an increase sensitivity to small blood flow velocities (down to 1 mm/s). In this method paper, we aim to introduce the concept of ultrafast Doppler as well as its main parameters. Firstly, we summarize the physical principles of unfocused wave imaging. Then, we present the Doppler signal processing main steps. Particularly, we explain the practical implementation of the critical tissue/blood flow separation algorithms and on the extraction of velocities from these filtered data. This theoretical description is supplemented by in vitro experiences. A tissue phantom embedding a canal with flowing blood-mimicking fluid is imaged with a research programmable ultrasound system. A blood flow image is obtained and the flow characteristics are displayed for several pixels in the canal. Finally, a review of in vivo applications is proposed, showing examples in several organs such as carotids, kidney, thyroid, brain and heart.

This protocol shows how to apply ultrafast ultrasound Doppler imaging to quantify blood flows. After a 1 s long acquisition, the experimenter has access to a movie of the full field of view with axial velocity values for each pixel every &#8776;0.3 ms (depending on the ultrasound time of flight).

The pulsed-Doppler effect is the main technique used in clinical echography to assess blood flow. Applied with conventional focused ultrasound Doppler ...

Stepwise Cell Seeding on Tessellated Scaffolds to Study Sprouting Blood Vessels

The cardiovascular system is a key player in human physiology, providing nourishment to most tissues in the body; vessels are present in different sizes, structures, phenotypes, and performance depending on each specific perfused tissue. The field of tissue engineering, which aims to repair or replace damaged or missing body tissues, relies on controlled angiogenesis to create a proper vascularization within the engineered tissues. Without a vascular system, thick engineered constructs cannot be sufficiently nourished, which may result in cell death, poor engraftment, and ultimately failure. Thus, understanding and controlling the behavior of engineered blood vessels is an outstanding challenge in the field. This work presents a high-throughput system that allows for the creation of organized and repeatable vessel networks for studying vessel behavior in a 3D scaffold environment. This two-step seeding protocol shows that vessels within the system react to the scaffold topography, presenting distinctive sprouting behaviors depending on the compartment geometry in which the vessels reside. The obtained results and understanding from this high throughput system can be applied in order to inform better 3D bioprinted scaffold construct designs, wherein fabrication of various 3D geometries cannot be rapidly assessed when using 3D printing as the basis for cellularized biological environments. Furthermore, the understanding from this high throughput system may be utilized for the improvement of rapid drug screening, the rapid development of co-cultures models, and the investigation of mechanical stimuli on blood vessel formation to deepen the knowledge of the vascular system.

Engineered tissues heavily rely on proper vascular networks to provide vital nutrients and gases and remove metabolic waste. In this work, a stepwise seeding protocol of endothelial cells and support cells creates highly organized vascular networks in a high-throughput platform for studying developing vessel behavior in a controlled 3D environment.

The cardiovascular system is a key player in human physiology, providing nourishment to most tissues in the body; vessels are present in different sizes, ...