Name: an in vitro model of a parallel-plate perfusion system to study bacterial adherence to graft tissues
Uploaded: 2019-01-07T14:00:00
Description: Watch this Scientific Journal Video about An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues at JoVE.com

This study was sponsored by a grant of the Research Fund KU Leuven (OT/14/097) given to RH. TRV was Postdoctoral Fellow of the FWO Research Foundation - Flanders (Belgium; Grant Number - 12K0916N) and RH is supported by the Clinical Research Fund of UZ Leuven.

1. Preparing Graft Tissues for In Vitro Studies
Note: Three types of tissues were used: Bovine Pericardium patch (BP), Cryopreserved Homograft (CH) and Bovine Jugular Vein grafts (BJV). In case of BJV conduit and CH (tissue processed by the European Homograft Bank (EHB) and stored in liquid nitrogen prior to use), both the wall and valvular leaflets were used. BP patch and BJV conduit were purchased from the manufacturers. Prior to use, thaw the CH following the EHB instructions<sup cla...

<ol>
	<li>Que, Y. A., Moreillon, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infective+endocarditis.">Infective endocarditis.</a> Nature Reviews Cardiology. 8 (6), 322-336 (2011).</li><li>Werdan, K., 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=Mechanisms+of+infective+endocarditis:+pathogen-host+interaction+and+risk+states.">Mechanisms of infective endocarditis: pathogen-host interaction and risk states.</a> Nature Reviews Cardiology. 11 (1), 35-50 (2014).</li><li>Moreillon, P., Que, Y. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Infective+endocarditis.">Infective endocarditis.</a> The Lancet. 363 (9403), 139-149 (2004).</li><li>Jalal, Z., 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=Selective+propensity+of+bovine+jugular+vein+material+to+bacterial+adhesions:+An+in+vitro+study.">Selective propensity of bovine jugular vein material to bacterial adhesions: An in vitro study.</a> International Journal of Cardiology. 198, 201-205 (2015).</li><li>Sharma, A., Cote, A. T., Hosking, M. C. K., Harris, K. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Systematic+Review+of+Infective+Endocarditis+in+Patients+With+Bovine+Jugular+Vein+Valves+Compared+With+Other+Valve+Types.">A Systematic Review of Infective Endocarditis in Patients With Bovine Jugular Vein Valves Compared With Other Valve Types.</a> JACC Cardiovascular Interventions. 10 (14), 1449-1458 (2017).</li><li>Malekzadeh-Milani, S., 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=Incidence+and+predictors+of+Melody(R)+valve+endocarditis:+a+prospective+study.">Incidence and predictors of Melody(R) valve endocarditis: a prospective study.</a> Archives of Cardiovascular Diseases. 108 (2), 97-106 (2015).</li><li>Hill, E. E., 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=Management+of+prosthetic+valve+infective+endocarditis.">Management of prosthetic valve infective endocarditis.</a> American Journal of Cardiology. 101 (8), 1174-1178 (2008).</li><li>Claes, J., 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=Clumping+factor+A,+von+Willebrand+factor-binding+protein+and+von+Willebrand+factor+anchor+Staphylococcus+aureus+to+the+vessel+wall.">Clumping factor A, von Willebrand factor-binding protein and von Willebrand factor anchor Staphylococcus aureus to the vessel wall.</a> Journal of Thrombosis and Haemostasis. 15 (5), 1009-1019 (2017).</li><li>Fowler, T., 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=Cellular+invasion+by+Staphylococcus+aureus+involves+a+fibronectin+bridge+between+the+bacterial+fibronectin-binding+MSCRAMMs+and+host+cell+beta1+integrins.">Cellular invasion by Staphylococcus aureus involves a fibronectin bridge between the bacterial fibronectin-binding MSCRAMMs and host cell beta1 integrins.</a> European Journal of Cell Biology. 79 (10), 672-679 (2000).</li><li>Patti, J. M., Hook, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microbial+adhesins+recognizing+extracellular+matrix+macromolecules.">Microbial adhesins recognizing extracellular matrix macromolecules.</a> Current Opinion in Cell Biology. 6 (5), 752-758 (1994).</li><li>Massey, R. C., 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=Fibronectin-binding+protein+A+of+Staphylococcus+aureus+has+multiple,+substituting,+binding+regions+that+mediate+adherence+to+fibronectin+and+invasion+of+endothelial+cells.">Fibronectin-binding protein A of Staphylococcus aureus has multiple, substituting, binding regions that mediate adherence to fibronectin and invasion of endothelial cells.</a> Cellular Microbiology. 3 (12), 839-851 (2001).</li><li>Jashari, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Belgian+and+European+experience+with+the+European+Homograft+Bank+(EHB)+cryopreserved+allograft+valves--assessment+of+a+20+year+activity.">Belgian and European experience with the European Homograft Bank (EHB) cryopreserved allograft valves--assessment of a 20 year activity.</a> Acta Chirurgica Belgica. 110 (3), 280-290 (2010).</li><li>Cheatham, J. P., 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=Clinical+and+hemodynamic+outcomes+up+to+7+years+after+transcatheter+pulmonary+valve+replacement+in+the+US+melody+valve+investigational+device+exemption+trial.">Clinical and hemodynamic outcomes up to 7 years after transcatheter pulmonary valve replacement in the US melody valve investigational device exemption trial.</a> Circulation. 131 (22), 1960-1970 (2015).</li><li>Que, Y. A., 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=Fibrinogen+and+fibronectin+binding+cooperate+for+valve+infection+and+invasion+in+Staphylococcus+aureus+experimental+endocarditis.">Fibrinogen and fibronectin binding cooperate for valve infection and invasion in Staphylococcus aureus experimental endocarditis.</a> The Journal of Experimental Medicine. 201 (10), 1627-1635 (2005).</li><li>Veloso, T. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+adherence+to+graft+tissues+in+static+and+flow+conditions.">Bacterial adherence to graft tissues in static and flow conditions.</a> The Journal of Thoracic and Cardiovascular Surgery. 155 (1), 325-332 (2018).</li><li>Liesenborghs, L., Verhamme, P., Vanassche, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Staphylococcus+aureus,+master+manipulator+of+the+human+hemostatic+system.">Staphylococcus aureus, master manipulator of the human hemostatic system.</a> Journal of Thrombosis and Haemostasis. 16 (3), 441-454 (2018).</li><li>Chiu, J. J., 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=Shear+stress+increases+ICAM-1+and+decreases+VCAM-1+and+E-selectin+expressions+induced+by+tumor+necrosis+factor-[alpha]+in+endothelial+cells.">Shear stress increases ICAM-1 and decreases VCAM-1 and E-selectin expressions induced by tumor necrosis factor-[alpha] in endothelial cells.</a> Artheriosclerosis, Thrombosis, and Vascular Biology. 24 (1), 73-79 (2004).</li><li>Jockenhoevel, S., Zund, G., Hoerstrup, S. P., Schnell, A., Turina, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiovascular+tissue+engineering:+a+new+laminar+flow+chamber+for+in+vitro+improvement+of+mechanical+tissue+properties.">Cardiovascular tissue engineering: a new laminar flow chamber for in vitro improvement of mechanical tissue properties.</a> ASAIO Journal. 48 (1), 8-11 (2002).</li><li>Veltrop, M. H. A. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bacterial+Species-+and+Strain-Dependent+Induction+of+Tissue+Factor+in+Human+Vascular+Endothelial+Cells.">Bacterial Species- and Strain-Dependent Induction of Tissue Factor in Human Vascular Endothelial Cells.</a> Infection and Immunity. 67 (11), 6130-6138 (1999).</li></ol>

Recent clinical observations give special awareness to IE as a complication in patients having undergone valve replacement of the RVOT6,13. Dysfunction of the implanted valve in IE is the result of bacterial interaction with the endovascular graft leading to extensive inflammatory and procoagulant reactions1,14. The presented novel in vitro model allowed us to investigate if differences in tissue...

Staphylococcus aureus (S. aureus) employs a variety of virulence strategies to circumvent the host immune defense system colonizing biological or non-biological surfaces implanted in the human circulation, which leads to severe intravascular infections such as sepsis and IE1,2,3,4,5. IE remains an important treatment associated complication in patients after implantation of prosthetic heart valves while individual factors contributing to the onset of IEare not yet fully understood6,7. Under flow conditions, bacteria encounter shear forces, which they need to overcome in order to adhere to the vessel wall8. Models, which allow studying the interplay between bacteria and prosthetic valve tissue or endothelium under flow, are of interest as they reflect the in vivo situation more.
Several specific mechanisms facilitate bacterial adherence to endothelial cells (ECs) and to the exposed subendothelial matrix (ECM) leading to tissue colonization and maturation of vegetations, being essential early steps in IE9. Various staphylococcal surface proteins or MSCRAMMs (microbial surface components recognizing adhesive matrix molecules) have been described as mediators of adhesion to host cells and to ECM proteins by interacting with molecules such as fibronectin, fibrinogen, collagen and von Willebrand factor (VWF)8,10,11. However, in view of intra-molecular folding of some virulence factors, mostly studied in static conditions, many of these interactions may have different relevance in endovascular infections in circulating blood.
Therefore, we present an in-house designed in vitro parallel-plate flow chamber model, which allows the assessment of bacterial adherence to different components of ECM and ECs in the context of tissue grafts implanted in the RVOT position. The overall purpose of the method described in this work is to study mechanisms of interaction between bacteria and underlying endovascular tissues in flow conditions, which are closely related to the in vivo environment of bloodstream pathogens such as S. aureus. This novel approach focuses on the susceptibility of graft tissue surfaces to bacterial adherence to identify potential risk factors for the development of IE.

<table>
	<tbody>
		<tr>
			<td>Bovine Pericardium (BP) patch, Supple Peri-Guard Pericardium</td>
			<td>Synovis Surgical Innovations, USA</td>
			<td>PC-0404SN</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Jugular Vein conduits (BJV)</td>
			<td>Contegra conduit; Medtronic Inc, USA</td>
			<td>M333105D001</td>
			<td></td>
		</tr>
		<tr>
			<td>CH cryopreserved homograft</td>
			<td>European Homograft Bank (EHB)</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr>
			<td>Acu-Punch</td>
			<td>Acuderm Inc, USA</td>
			<td>P850 (8 mm); P1050 (10 mm)</td>
			<td></td>
		</tr>
		<tr>
			<td>human Albumin</td>
			<td>Flexbumin; Baxter, Belgium</td>
			<td>BE171464 
			LOT:16G12C</td>
			<td></td>
		</tr>
		<tr>
			<td>Tryptic soy broth (TSB)</td>
			<td>Fluka, Steinheim, Germany</td>
			<td>22092-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Heart infusion broth (BHI)</td>
			<td>Fluka</td>
			<td>53286-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline (PBS).</td>
			<td>Gibco</td>
			<td>14190-094</td>
			<td></td>
		</tr>
		<tr>
			<td>5(6)-Carboxyfluorescein N-hydroxysuccinimide ester (CF)</td>
			<td>Sigma-Aldrich, Germany</td>
			<td>21878-100MG-F</td>
			<td></td>
		</tr>
		<tr>
			<td>Peristaltic pump (MODEL ISM444B)</td>
			<td>Ismatec BVP-Z Standard; Cole Parmer, Wertheim, Germany</td>
			<td>631942-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Sonication bath</td>
			<td>VWR Ultrasonic Cleaner; VWR, Radnor, Pa</td>
			<td>142-6044</td>
			<td>230V/50 -60Hz 60VA; HF45kHz, 30W</td>
		</tr>
		<tr>
			<td>ProLong Gold Antifade Mountant</td>
			<td>Invitrogen by ThermoFisher</td>
			<td>P36930</td>
			<td></td>
		</tr>
		<tr>
			<td>InCell Analyzer 2000 (fluorescence scanner)</td>
			<td>GE Healthcare Life Sciences, Pittsburgh, Pa</td>
			<td>29027886</td>
			<td></td>
		</tr>
		<tr>
			<td>Arium Pro VF - ultrapure water - H2O MilliQ</td>
			<td>Millipore</td>
			<td>87206462</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscopic slides - Tissue Culture Chambers (1-well)</td>
			<td>Sarstedt</td>
			<td>94.6140.102</td>
			<td></td>
		</tr>
		<tr>
			<td>1-well on Lumox detachable</td>
			<td>Sarstedt</td>
			<td>94.6150.101</td>
			<td></td>
		</tr>
		<tr>
			<td>Stainless Steel - surgical Blades</td>
			<td>Swann-Morton</td>
			<td>311</td>
			<td></td>
		</tr>
		<tr>
			<td>Tygon Silicone Tubing, 1/8&#34;ID x 1/4&#34;OD</td>
			<td>Cole-Parmer</td>
			<td>EW-95702-06</td>
			<td>Temperature range: &#8211;80 to 200&#176;C 
			Sterilize: With ethylene oxide, gamma irradiation, or autoclave for 30 min, 15 psi of pressure</td>
		</tr>
		<tr>
			<td>PharMed BPT Tubing</td>
			<td>Saint-Gobain</td>
			<td>AY242012</td>
			<td>Autoclavable 30 min at 121&#176;C</td>
		</tr>
		<tr>
			<td>Tygon LMT-55 Tubing</td>
			<td>Saint Gobain Performance Plastics&#8482;</td>
			<td>15312022</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermostat</td>
			<td>BMG BIOMEDIZINTECHNIK</td>
			<td>300-0042</td>
			<td>230V, 90VA, 50Hz</td>
		</tr>
	</tbody>
</table>

an in vitro model of a parallel-plate perfusion system to study bacterial adherence to graft tissues

Various valved conduits and stent-mounted valves are used for right ventricular outflow tract (RVOT) valve replacement in patients with congenital heart disease. When using prosthetic materials however, these grafts are susceptible to bacterial infections and various host responses.
Identification of bacterial and host factors that play a vital role in endovascular adherence of microorganisms is of importance to better understand the pathophysiology of the onset of infections such as infective endocarditis (IE) and to develop preventive strategies. Therefore, the development of competent models to investigate bacterial adhesion under physiological shear conditions is necessary. Here, we describe the use of a newly designed in vitro perfusion chamber based on parallel plates that allows the study of bacterial adherence to different components of graft tissues such as exposed extracellular matrix, endothelial cells and inert areas. This method combined with colony-forming unit (CFU) counting is adequate to evaluate the propensity of graft materials towards bacterial adhesion under flow. Further on, the flow chamber system might be used to investigate the role of blood components in bacterial adhesion under shear conditions. We demonstrated that the source of tissue, their surface morphology and bacterial species specificity are not the major determining factors in bacterial adherence to graft tissues by using our in-house designed in vitro perfusion model.

To better understand the mechanisms behind IE development, this model enables the evaluation of bacterial and tissue associated factors present in the in vivo situation of infection onset.
In detail, the novel in vitro approach allows to quantify bacterial adhesion in flow conditions to different graft tissues by perfusing fluorescently labeled bacteria over the tissues exerting the shear stresses in t...

Watch this Scientific Journal Video about An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues at JoVE.com

An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues

We describe an in-house designed in vitro flow chamber model, which allows the investigation of bacterial adherence to graft tissues.

An In Vitro Model of a Parallel-Plate Perfusion System to Study Bacterial Adherence to Graft Tissues

Various valved conduits and stent-mounted valves are used for right ventricular outflow tract (RVOT) valve replacement in patients with congenital heart ...

This method can help answer key questions in the pathogenesis of infective endocarditis, and pathobiograms through fields such as the interplay between bacteria, blood cells, and endothelial cells lining musculature. The main advantage of this technique is that the tissue grafts might be directly exposed to mutual interactions with various targets, such as bacteria, platelets, and proteins in standardized flow conditions. The implication of this technique extend to our therapy of infective endocarditis, because it can unravel important molecular interactions and factors driving high infectiveness of certain tissues.This method provides insight into pathogenesis of vegetation formation. It can also be applicable in studies investigating vascular permeability, cell mobility, and gene cell expression. To begin the protocol, place a previously prepared tissue biopsy 10 millimeters in diameter, and the same thickness between a microscope slide and an eight millimeter circular perforation, and a rubber gasket with the inner surface facing up, to contact the bacterial suspension.Focus on the tissue graft orientation while placed in the holder. Make sure the inner surface of the tissue is already exposed to the bloodstream faces up to contact your experimental medium. Next, insert your holder with the tissue into the gasket sheet that is embedded in the bottom metal frame of the chamber.Attach the upper metal frame with the corresponding gasket sheet onto the bottom of the chamber with the previously inserted tissue holder. Then mount the entire chamber with eight screws and screw nuts. Make sure that the chamber height is always the same across grafts by using a caliper or ruler.Next connect the flow chamber with a peristaltic pump. Then connect the 400 milliliter fluid reservoir with the tubes. Perfuse the tissues with 100 milliliter suspensions of ten to the seven fluorescently-labeled colony forming units in phosphate buffered saline with the sheer stress of three dines per square centimeter and corresponding flow rate of four milliliters per minute for one hour using the peristaltic pump and the bacterial reservoir.Recirculate continuously the 100 milliliter bacterial suspension using the same collection reservoir. After perfusion, dismantle the chamber to release the graft. Wash the tissue piece two times with four milliliters of PBS in a 12-well plate using an orbital shaker for three minutes.Then cut the inner part of the graft using a skin biopsy punch with a smaller diameter. Place each tissue biopsy into a separate 14 milliliter tube containing one milliliter of sterile 0.9%sodium chloride. Detach the bacteria from the tissue using a sonication bath for 10 minutes.Prepare a single 14 milliliter tube with 10 milliliters of sterile 0.9%sodium chloride to make serial dilutions of the bacterial suspension obtained after sonication. Label the tube number two. Prepare three 14 milliliter tubes with 10 milliliters of sterile 0.9%sodium chloride for serial dilutions of the initial bacterial suspension taken to the profusion experiment.Label the tubes number three, number four, and number five. Next, secure three agar plates, one for the bacterial perfusion, one for the control perfusion of PBS, and the third one for the initial bacterial suspension used for perfusions. Label three sectors per plate for the tissue experiment in the following manner:10-1, 10-3, and 10-4.To count the number of colony-forming units in the bacterial perfusing, label the plate as follows:10-1, 10-3, 10-5, and 10-7. Vortex the tubes containing the tissue biopsy for 15 seconds each, to make serial dilutions. To prepare the serial dilutions, transfer 100 microliters of tube number one to tube number two, and vortex the tube to thoroughly mix the solution.Spread 100 microliters of the contents of tube number one and number two onto the corresponding sectors, 10-1 and 10-3 of the agar plate. Then spread 10 microliters of tube number two on sector 10 four. Repeat this step four times to obtain four separate growths from each volume of 10 microliters.To prepare serial dilutions of the initial culture, first vortex the dilution for 15 seconds and transfer 100 microliters of bacterial suspension to tube number three, and mix vigorously by vortexing. Add 100 microliters of tube number three to tube number four and mix again. Repeat the procedure for tube number five from tube number four.Spread 100 microliters of the contents of tubes number three, number four, number five, and the labeled initial culture respectively onto sectors 10-3, 10-5, 10-7, and 10-1 of the blood agar plate. Leave the blood agar plates under the laminar hood to air dry the bacterial spreads, typically for 10 minutes. Afterwards, place the plates at 37 degrees Celsius for overnight incubation.After overnight incubation, count the bacterial colonies to obtain the number of CFUs. Under sheer stress conditions, similar bacterial attachment across the various graft tissues was observed for both staphylococcus aureus and staphylococcus epidermidis infection. Following the procedures, streptococcus sanguinis displayed significant reduction of adherence to the bovine jugular vein wall, when compared to the bovine pericardium patch.When comparing the three species of bacteria, streptococcus sanguinis presents significantly lower adhesion to the bovine jugular vein wall in relation to staphylococcus aureus and staphylococcus epidermidis. While attempting this procedure, it's important to remember to have prepared correct tissues of the same head. It will ensure similar conditions across all experiment specimens and minimize data variability between different series of experiments.After its development, this technique allows researchers to explore the complex disorder systems in a step by step manner by enriching their in vitro model approaches with different elements to build up full complexity close to medical status.

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Developmental Biology

A Novel Ex Ovo Banding Technique to Alter Intracardiac Hemodynamics in an Embryonic Chicken System

The new model presented here can be used to understand the influence of hemodynamics on specific cardiac developmental processes, at the cellular and molecular level. To alter intracardiac hemodynamics, fertilized chicken eggs are incubated in a humidified chamber to obtain embryos of the desired stage (HH17). Once this developmental stage is achieved, the embryo is maintained ex ovo and hemodynamics in the embryonic heart are altered by partially constricting the outflow tract (OFT) with a surgical suture at the junction of the OFT and ventricle (OVJ). Control embryos are also cultured ex ovo but are not subjected to the surgical intervention. Banded and control embryos are then incubated in a humidified incubator for the desired period of time, after which 2D ultrasound is employed to analyze the change in blood flow velocity at the OVJ as a result of OFT banding. Once embryos are maintained ex ovo, it is important to ensure adequate hydration in the incubation chamber so as to prevent drying and eventually embryo death. Using this new banded model, it is now possible to perform analyses of changes in the expression of key players involved in valve development and to understand the role of hemodynamics on cellular responses in vivo, which could not be achieved previously.

A Novel Ex Ovo Banding Technique to Alter Intracardiac Hemodynamics in an Embryonic Chicken System

For the first time we present here a reproducible banding procedure to alter hemodynamics in the developing heart ex ovo. This is achieved by partially constricting the outflow tract (OFT).

The new model presented here can be used to understand the influence of hemodynamics on specific cardiac developmental processes, at the cellular and ...

Development of an Ethanol-induced Fibrotic Liver Model in Zebrafish to Study Progenitor Cell-mediated Hepatocyte Regeneration

Sustained liver fibrosis with continuation of extracellular matrix (ECM) protein build-up results in the loss of cellular competency of the liver, leading to cirrhosis with hepatocellular dysfunction. Among multiple hepatic insults, alcohol abuse can lead to significant health problems including liver failure and hepatocellular carcinoma. Nonetheless, the identity of endogenous cellular sources that regenerate hepatocytes in response to alcohol has not been properly investigated. Moreover, few studies have effectively modeled hepatocyte regeneration upon alcohol-induced injury. We recently reported on establishing an ethanol (EtOH)-induced fibrotic liver model in zebrafish in which hepatic progenitor cells (HPCs) gave rise to hepatocytes upon near-complete hepatocyte loss in the presence of fibrogenic stimulus. Furthermore, through chemical screens using this model, we identified multiple small molecules that enhance hepatocyte regeneration. Here we describe in detail the procedures to develop an EtOH-induced fibrotic liver model and to perform chemical screens using this model in zebrafish. This protocol will be a critical tool to delineate the molecular and cellular mechanisms of how hepatocyte regenerates in the fibrotic liver. Furthermore, these methods will facilitate potential discovery of novel therapeutic strategies for chronic liver disease in vivo.

Sustained fibrosis with deposition of excessive extracellular matrix proteins leads to cirrhosis. Alcohol abuse is one of the main causes of severe liver disease. We established an ethanol-induced zebrafish fibrotic liver model to study the mechanisms and strategies of promoting hepatocyte regeneration upon alcohol-induced injury.

Sustained liver fibrosis with continuation of extracellular matrix (ECM) protein build-up results in the loss of cellular competency of the liver, leading ...

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

Corneal endothelial cells (CECs) play a crucial role in maintaining corneal clarity through active pumping. A reduced CEC count may lead to corneal edema and diminished visual acuity. However, human CECs are prone to compromised proliferative potential. Furthermore, stimulation of cell growth is often complicated by gradual endothelial-mesenchymal transition (EnMT). Therefore, understanding the mechanism of EnMT is necessary for facilitating the regeneration of CECs with competent function. In this study, we prepared a primary culture of bovine CECs by peeling the CECs with Descemet's membrane from the corneal button and demonstrated that bovine CECs exhibited the EnMT process, including phenotypic change, nuclear translocation of &#946;-catenin, and EMT regulators snail and slug, in the in vitro culture. Furthermore, we used a rat corneal endothelium cryoinjury model to demonstrate the EnMT process in vivo. Collectively, the in vitro primary culture of bovine CECs and in vivo rat corneal endothelium cryoinjury models offers useful platforms for investigating the mechanism of EnMT.

In Vitro and In Vivo Models to Study Corneal Endothelial-mesenchymal Transition

A primary culture of bovine corneal endothelial cells was used to investigate the mechanism of corneal endothelial-mesenchymal transition. Furthermore, a rat corneal endothelium cryoinjury model was used to demonstrate corneal endothelial-mesenchymal transition in vivo.

Corneal endothelial cells (CECs) play a crucial role in maintaining corneal clarity through active pumping. A reduced CEC count may lead to corneal edema ...

A 5-mC Dot Blot Assay Quantifying the DNA Methylation Level of Chondrocyte Dedifferentiation In Vitro

The dedifferentiation of hyaline chondrocytes into fibroblastic chondrocytes often accompanies monolayer expansion of chondrocytes in vitro. The global DNA methylation level of chondrocytes is considered to be a suitable biomarker for the loss of the chondrocyte phenotype. However, results based on different experimental methods can be inconsistent. Therefore, it is important to establish a precise, simple, and rapid method to quantify global DNA methylation levels during chondrocyte dedifferentiation.
Current genome-wide methylation analysis techniques largely rely on bisulfite genomic sequencing. Due to DNA degradation during bisulfite conversion, these methods typically require a large sample volume. Other methods used to quantify global DNA methylation levels include high-performance liquid chromatography (HPLC). However, HPLC requires complete digestion of genomic DNA. Additionally, the prohibitively high cost of HPLC instruments limits HPLC&#39;s wider application.
In this study, genomic DNA (gDNA) was extracted from human chondrocytes cultured with varying number of passages. The gDNA methylation level was detected using a methylation-specific dot blot assay. In this dot blot approach, a gDNA mixture containing the methylated DNA to be detected was spotted directly onto an N+ membrane as a dot inside a previously drawn circular template pattern. Compared with other gel electrophoresis-based blotting approaches and other complex blotting procedures, the dot blot method saves significant time. In addition, dot blots can detect overall DNA methylation level using a commercially available 5-mC antibody. We found that the DNA methylation level differed between the monolayer subcultures, and therefore could play a key role in chondrocyte dedifferentiation. The 5-mC dot blot is a reliable, simple, and rapid method to detect the general DNA methylation level to evaluate chondrocyte phenotype.

A 5-mC Dot Blot Assay Quantifying the DNA Methylation Level of Chondrocyte Dedifferentiation In Vitro

We present a method to quantify DNA methylation based on the 5-methylcytosine (5-mC) dot blot. We determined the 5-mC levels during chondrocyte dedifferentiation. This simple technique could be used to quickly determine the chondrocyte phenotype in ACI treatment.

The dedifferentiation of hyaline chondrocytes into fibroblastic chondrocytes often accompanies monolayer expansion of chondrocytes in vitro. The global ...

Whole-mount Confocal Microscopy for Adult Ear Skin: A Model System to Study Neuro-vascular Branching Morphogenesis and Immune Cell Distribution

Here, we present a protocol of a whole-mount adult ear skin imaging technique to study comprehensive three-dimensional neuro-vascular branching morphogenesis and patterning, as well as immune cell distribution at a cellular level. The analysis of peripheral nerve and blood vessel anatomical structures in adult tissues provides some insights into the understanding of functional neuro-vascular wiring and neuro-vascular degeneration in pathological conditions such as wound healing. As a highly informative model system, we have focused our studies on adult ear skin, which is readily accessible for dissection. Our simple and reproducible protocol provides an accurate depiction of the cellular components in the entire skin, such as peripheral nerves (sensory axons, sympathetic axons, and Schwann cells), blood vessels (endothelial cells and vascular smooth muscle cells), and inflammatory cells. We believe this protocol will pave the way to investigate morphological abnormalities in peripheral nerves and blood vessels as well as the inflammation in the adult ear skin under different pathological conditions.

Here, we describe a high resolution whole-mount imaging method in the entire adult mouse ear skin, which enables us to visualize branching morphogenesis and patterning of peripheral nerves and blood vessels, as well as immune cell distribution.

Here, we present a protocol of a whole-mount adult ear skin imaging technique to study comprehensive three-dimensional neuro-vascular branching ...

Organotypic Culture Method to Study the Development Of Embryonic Chicken Tissues

The embryonic chicken is commonly used as a reliable model organism for vertebrate development. Its accessibility and short incubation period makes it ideal for experimentation. Currently, the study of these developmental pathways in the chicken embryo is conducted by applying inhibitors and drugs at localized sites and at low concentrations using a variety of methods. In vitro tissue&#160;culturing is a technique that enables the study of tissues separated from the host organism, while simultaneously bypassing many of the physical limitations present when working with whole embryos, such as the susceptibility of embryos to high doses of potentially lethal chemicals. Here, we present an organotypic culturing protocol for culturing the embryonic chicken half head in vitro, which presents new opportunities for the examination of developmental processes beyond the currently established methods.

Here, we present an organotypic culturing protocol to grow embryonic chicken organs in vitro. Using this method, the development of embryonic chicken tissue can be studied, while maintaining a high degree of control over the culture environment.

The embryonic chicken is commonly used as a reliable model organism for vertebrate development. Its accessibility and short incubation period makes it ...

A Hyperandrogenic Mouse Model to Study Polycystic Ovary Syndrome

Hyperandrogenemia plays a critical role in reproductive and metabolic function in females and is the hallmark of polycystic ovary syndrome. Developing a lean PCOS-like mouse model that mimics women with PCOS is clinically meaningful. In this protocol, we describe such a model. By inserting a 4 mm length of DHT (dihydrotestosterone) crystal powder pellet (total length of pellet is 8 mm), and replacing it monthly, we are able to produce a PCOS-like mouse model with serum DHT levels 2 fold higher than mice not implanted with DHT (no-DHT). We observed reproductive and metabolic dysfunction without changing body weight and body composition. While exhibiting a high degree of infertility, a small subset of these PCOS-like female mice can get pregnant and their offspring show delayed puberty and increased testosterone as adults. This PCOS-like lean mouse model is a useful tool to study the pathophysiology of PCOS and the offspring from these PCOS-like dams.

We describe the development of a lean PCOS-like mouse model with&#160;dihydrotestosterone pellet to study the pathophysiology of PCOS and the offspring from these PCOS-like dams.

Hyperandrogenemia plays a critical role in reproductive and metabolic function in females and is the hallmark of polycystic ovary syndrome. Developing a ...

An In Vitro 3D Model and Computational Pipeline to Quantify the Vasculogenic Potential of iPSC-Derived Endothelial Progenitors

Induced pluripotent stem cells (iPSCs) are a patient-specific, proliferative cell source that can differentiate into any somatic cell type. Bipotent endothelial progenitors (EPs), which can differentiate into the cell types necessary to assemble mature, functional vasculature, have been derived from both embryonic and induced pluripotent stem cells. However, these cells have not been rigorously evaluated in three-dimensional environments, and a quantitative measure of their vasculogenic potential remains elusive. Here, the generation and isolation of iPSC-EPs via fluorescent-activated cell sorting are first outlined, followed by a description of the encapsulation and culture of iPSC-EPs in collagen hydrogels. This extracellular matrix (ECM)-mimicking microenvironment encourages a robust vasculogenic response; vascular networks form after a week of culture. The creation of a computational pipeline that utilizes open-source software to quantify this vasculogenic response is delineated. This pipeline is specifically designed to preserve the 3D architecture of the capillary plexus to robustly identify the number of branches, branching points, and the total network length with minimal user input.

Endothelial progenitors derived from induced pluripotent stem cells (iPSC-EPs) have the potential to revolutionize cardiovascular disease treatments and to enable the creation of more faithful cardiovascular disease models. Herein, the encapsulation of iPSC-EPs in three-dimensional (3D) collagen microenvironments and a quantitative analysis of these cells&#8217; vasculogenic potential are described.

Induced pluripotent stem cells (iPSCs) are a patient-specific, proliferative cell source that can differentiate into any somatic cell type. Bipotent ...

Assessment of Oxidative Damage in the Primary Mouse Ocular Surface Cells/Stem Cells in Response to Ultraviolet-C (UV-C) Damage

The ocular surface is subjected to regular wear and tear due to various environmental factors. Exposure to UV-C radiation constitutes an occupational health hazard. Here, we demonstrate the exposure of primary stem cells from the mouse ocular surface to UV-C radiation. Reactive oxygen species (ROS) formation is the readout of the extent of oxidative stress/damage. In an experimental in vitro setting, it is also essential to assess the percentage of dead cells generated due to oxidative stress. In this article, we will demonstrate the 2&#39;,7&#39;-Dichlorofluoresceindiacetate (DCFDA) staining of UV-C exposed mouse primary ocular surface stem cells and their quantification based on the fluorescent images of DCFDA staining. DCFDA staining directly corresponds to ROS generation. We also demonstrate the quantification of dead and live cells by simultaneous staining with propidium iodide (PI) and Hoechst 3332 respectively and the percentage of DCFDA (ROS positive) and PI positive cells.

Assessment of Oxidative Damage in the Primary Mouse Ocular Surface Cells/Stem Cells in Response to Ultraviolet-C UV-C Damage

This protocol demonstrates the simultaneous detection of reactive oxygen species (ROS), live cells, and dead cells in live primary cultures from mouse ocular surface cells. 2&#39;,7&#39;-Dichlorofluoresceindiacetate, propidium iodide, and Hoechst staining are used to assess the ROS, dead cells, and live cells, respectively, followed by imaging and analysis.

The ocular surface is subjected to regular wear and tear due to various environmental factors. Exposure to UV-C radiation constitutes an occupational ...

Clonal Genetic Tracing using the Confetti Mouse to Study Mineralized Tissues

Labeling an individual cell in the body to monitor which cell types it can give rise to and track its migration through the organism or determine its longevity can be a powerful way to reveal mechanisms of tissue development and maintenance. One of the most important tools currently available to monitor cells in vivo is the Confetti mouse model. The Confetti model can be used to genetically label individual cells in living mice with various fluorescent proteins in a cell type-specific manner and monitor their fate, as well as the fate of their progeny over time, in a process called clonal genetic tracing or clonal lineage tracing. This model was generated almost a decade ago and has contributed to an improved understanding of many biological processes, particularly related to stem cell biology, development, and renewal of adult tissues. However, preserving the fluorescent signal until image collection and simultaneous capturing of various fluorescent signals is technically challenging, particularly for mineralized tissue. This publication describes a step-by-step protocol for using the Confetti model to analyze growth plate cartilage that can be applied to any mineralized or nonmineralized tissue.

This method describes the use of the R26R-Confetti (Confetti) mouse model to study mineralized tissues, covering all steps from the breeding strategy to the image acquirements. Included is a general protocol that can be applied to all soft tissues and a modified protocol that can be applied to mineralized tissues.

Labeling an individual cell in the body to monitor which cell types it can give rise to and track its migration through the organism or determine its ...