Published: January 7th, 2019
We describe an in-house designed in vitro flow chamber model, which allows the investigation of 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.
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 understood
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
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.......
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.......
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.....
|Bovine Pericardium (BP) patch, Supple Peri-Guard Pericardium
|Synovis Surgical Innovations, USA
|Bovine Jugular Vein conduits (BJV)
|Contegra conduit; Medtronic Inc, USA
|CH cryopreserved homograft
|European Homograft Bank (EHB)
|Acuderm Inc, USA
|P850 (8 mm); P1050 (10 mm)
|Flexbumin; Baxter, Belgium
|Tryptic soy broth (TSB)
|Fluka, Steinheim, Germany
|Heart infusion broth (BHI)
|Phosphate buffered saline (PBS).
|5(6)-Carboxyfluorescein N-hydroxysuccinimide ester (CF)
|Peristaltic pump (MODEL ISM444B)
|Ismatec BVP-Z Standard; Cole Parmer, Wertheim, Germany
|VWR Ultrasonic Cleaner; VWR, Radnor, Pa
|230V/50 -60Hz 60VA; HF45kHz, 30W
|ProLong Gold Antifade Mountant
|Invitrogen by ThermoFisher
|InCell Analyzer 2000 (fluorescence scanner)
|GE Healthcare Life Sciences, Pittsburgh, Pa
|Arium Pro VF - ultrapure water - H2O MilliQ
|Microscopic slides - Tissue Culture Chambers (1-well)
|1-well on Lumox detachable
|Stainless Steel - surgical Blades
|Tygon Silicone Tubing, 1/8"ID x 1/4"OD
|Temperature range: –80 to 200°C
Sterilize: With ethylene oxide, gamma irradiation, or autoclave for 30 min, 15 psi of pressure
|PharMed BPT Tubing
|Autoclavable 30 min at 121°C
|Tygon LMT-55 Tubing
|Saint Gobain Performance Plastics™
|230V, 90VA, 50Hz
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