Biomaterials 24 (2003) 89–95 An in vitro model of pericardial tissue healing Douglas C. Marchion, Jean C. Pfau, Patricia A. Weber, Albert C. Grobe, Carlos M.G. Duran*, David T. Cheung The International Heart Institute of Montana Foundation, 554 West Broadway, 59802-4008, Missoula, MT, USA Received 8 August 2001; received in revised form 20 March 2002; accepted 21 June 2002 Abstract Introduction: A previous study in our laboratory showed that a flap of fresh autologous pericardium bisecting the aorta of sheep retractedandbecamefibrotic.Histologicanalysessuggestedthatactivatedcellswithinthepericardiumcontributedtotheretraction oftheimplant.Herewereportthedevelopmentofaninvitromodeltoinvestigatetheeffectsofserumoncellularproliferationand cell-mediated tissue contraction. Methods:Sectionsoflivingandethanol-treatedsheeppericardiumwereincubatedwith0.5%,5%,10%,20%,and50%serumin mediumforupto8daysandevaluatedforcellularproliferationandtissuecontraction.Theseserum-stimulatedeventswerefurther evaluated in the presence of Mitomycin C, Cytochalasin B and D, Aphidicolin, AraC, and Cycloheximide. Results: Cellular proliferation and cell-mediated tissue contraction were induced by serum in a dose-dependent manner. ExpressionofPCNAwassuppressedinthepresenceofCytochalasinB,CytochalasinD,Aphidicolin,andAraC.Tissuecontraction was prevented by Cycloheximide. Mitomycin C inhibited both proliferation and tissue contraction. Ethanol-treated tissue, which was absent of living cells, did not respond to stimulation with serum. Conclusions:Aninvitromodelwasdevelopedtostudytheresponsesofcellswithinpericardialtissuestostimulationbyserum.In thismodel,seruminducedcellularproliferationandtissuecontraction.Differentchemicalinhibitorsindependentlymodulatedthese serum-stimulated events. Pre-existing cells within pericardial tissues might respond to stimulus through differential pathways. This model may help to develop methods to make autologous pericardium a clinically useful biomaterial. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Pericardium; In vitro model; Contraction; Proliferation; Serum 1. Introduction Since the early days of cardiovascular surgery, autologous pericardium has been used as a repair biomaterial [1,2]. Its accessibility within the operative field and the ease of obtaining large sheaths of pliable material made it an obvious choice to the surgeon. Autologous pericardium was first used as a patch to close atrial septal defects and to enlarge the right ventricular outflow tract [3–5]. Valve-bearing conduits were also constructed and used in the low-pressure right side of the heart [6,7]. Although it healed well to the surrounding tissues and therefore solved the clinical problem, thickening and retraction of the pericardium was a constant finding. When used as a large patch to redirect blood flow within the atria, reoperation was often needed because of retraction [8]. However, autologous pericardium became dilated and even aneurysmatic when used in a high-pressure environment such as a large ventricular septal defect, the right outflow tract in the presence of pulmonary hyperten- sion, or in the aorta [9]. In practice, the clinical use of autologous pericardium has been abandoned; but, recently, the need for a biomaterial in heart valve repair has rekindled interest. Its experimental use for leaflet enlargement and mitral valve chordae replacement still shows progressive fibrosis and severe retraction [2,10]. Despite these negative findings and in the absence of a satisfactory biomaterial with the accessibility, low cost, non-immunogenicity, and freedom from donor- derived pathogens, autologous pericardium remains an *Corresponding author. Tel.: +1-406-329-5668; fax: +1-406-329- 5880. E-mail address: duran@saintpatrick.org (C.M.G. Duran). 0142-9612/02/$-see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S0142-9612(02)00255-7