Prevention of postcardiopulmonary bypass pericardial adhesions by a new resorbable collagen membrane

INSTITUTIONAL REPORT Interactive CardioVascular and Thoracic Surgery 14 (2012) 469–473 doi:10.1093/icvts/ivr159 Advance Access publication 19 January 2012 Prevention of postcardiopulmonary bypass pericardial adhesions by a new resorbable collagen membrane Alain Bela,b,c,*, Massimo Riccic, Julie Piquetc,d, Patrick Brunevald,e, Marie-Cécile Perierf, Christian Gagnieug, Jean-Noël Fabiania,d and Philippe Menaschéa,b,c,d a b c d e f * Corresponding author. Department of Cardiovascular Surgery, Hôpital Européen Georges Pompidou, 20, rue Leblanc, 75908 Paris Cedex 15, France. Tel: +33-1-56093622; fax: +33-1-56093261; email: (A. Bel). Received 15 September 2011; received in revised form 29 November 2011; accepted 6 December 2011 Reduction in mediastinal adhesions is an issue in cardiac surgery. To evaluate a porcine-bioengineered collagen membrane (Cova™ CARD) intended to promote tissue regeneration, 18 sheep underwent a sternotomy and a 30 min period of cardiopulmonary bypass. They were divided into three equal groups: pericardium left open, placement of an e-polytetrafluoroethylene membrane (Preclude®) taken as a non-absorbable substitute comparator and placement of the absorbable Cova™ CARD membrane. Four months thereafter, the study animals underwent repeat sternotomy and were macroscopically assessed for the degree of material resorption and the intensity of adhesions. Explanted hearts were evaluated blindly for the magnitude of the inflammatory response, fibrosis and epicardial re-mesothelialization. The bioengineered membrane was absorbed by 4 months and replaced by a loosely adherent tissue leading to the best adhesion score. There was no inflammatory reaction (except for a minimal one in an animal). Fibrosis was minimal (P = 0.041 vs Preclude®). The highest degree of epicardial re-mesothelialization, albeit limited, was achieved by the bioengineered group in which five of six sheep demonstrated a new lining of mesothelial cells in contrast to two animals in each of the other groups. This collagen membrane might thus represent an attractive pericardial substitute for preventing post-operative adhesions. Keywords: Pericardial adhesions • Biomaterials • Reoperation • Pericardium INTRODUCTION MATERIALS AND METHODS Despite continuous improvements, reoperations in cardiac surgery remain challenging because injury to the heart, great vessels or bypass conduits can be life-threatening. Several pericardial substitutes have been developed that broadly fall into two categories: non-absorbable materials, exemplified by the e-polytetrafluoroethylene (ePTFE) membrane, and absorbable membranes. The latter are expected to provide superior healing by guiding tissue regeneration [1]. However, they raise technical challenges as mechanical strength and suturability to provide good handling characteristics; and biological challenges because they need to be as biocompatible as possible and degrade according to a time frame matching the kinetics of the natural healing process without releasing pro-inflammatory by-products. The present study was designed to test a new bioengineered collagen pericardial substitute (Cova™ CARD, Biom’Up, Lyon, France) in a clinically relevant large animal model of sternotomy and cardiopulmonary bypass (CPB). Eighteen pre-Alpes sheep, weighing
60 kg, were used in this study. The study was approved by our Institutional Review Board and conducted in compliance with the European Convention on Animal Care. Preparation of the absorbable pericardial membrane Cova™ CARD is a CE-marked patented membrane made of purified porcine tendon type I collagen (Fig. 1) according to a preparation protocol described previously [2]. Surgical protocol After isoflurane-based anaesthesia and endotracheal intubation, a median sternotomy was performed, the pericardium was © The Author 2012. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. CARDIAC GENERAL Abstract g Department of Cardiovascular Surgery, Assistance Publique - Hôpitaux de Paris, Hospital European Georges Pompidou, Paris, France INSERM U 633, Paris, France Laboratory of BioSurgical Research, Alain Carpentier Foundation, Paris, France University Paris Descartes, Paris, France Department of Pathology, Assistance Publique - Hôpitaux de Paris, Hospital European Georges Pompidou, INSERM U 970, Paris, France INSERM PARCC University Paris Descartes UMR-S970, Paris, France University of Lyon, INSA of Lyon UMR 5510 MATEIS/I2B, Lyon, France 470 A. Bel et al. / Interactive CardioVascular and Thoracic Surgery The re-mesothelialization of the epicardial surface was assessed after immunostaining with an antibody against cytokeratins AE1/ AE3 (Dako, Trappes, France), diluted at 1/100. Antigen retrieval used citrate buffer. The sections were revealed using the Avidin-Biotin Complex technique. The extent of immunolabeling was classified from 0 to 3 (0 = no cell marking; 1 = lining involving less than one-third of the section area; 2 = lining involving between one-third and two-thirds of the section area; 3 = almost complete lining marking). Five blocks were assessed for each animal leading to a score ranging from 0 to 15. Figure 1: Bioengineered collagen Cova™ CARD membrane. Pathology An in-block fragment was obtained from the anterior surface of the heart which comprised, from the inside to the outside, the right ventricular wall, the adhesion tissue and occasionally bone fragments. Specimens were fixed in 10% formaldehyde. For each animal, five fragments were systematically embedded in paraffin and cut into 5-µm-thick slices. The sections were stained with haematoxylin–eosin to assess the inflammatory reaction and fibrosis, identify potential remnants of the pericardial substitute and look for a mesothelial cell lining. Sections were examined by a pathologist blinded to the treatment group. The severity of the inflammatory reaction was based on the quantification of inflammatory cells and inflammatory foci and graded using an inflammatory reaction score derived from that described by Lu et al. [4] (from Grade 0 (no cell infiltration) to Grade 3 (diffuse inflammatory cell infiltration)). Fibrosis was assessed with regard to its extent (0 = limited; 1 = extensive), density (0 = loose; 1 = dense) and thickness (0 = thin; 1 = thick) and a composite fibrosis score was created (from 0 to 3). Statistical analysis The Kruskall–Wallis test was used for assessing the statistical difference between the three groups. Statistical significance was set at the 0.05 level. If a difference was found significant, a Mann– Whitney–Wilcoxon test with exact P-values was subsequently performed within the groups. RESULTS Macroscopic findings After 4 months, the bioengineered collagen membranes were absorbed and replaced by a loose regenerated tissue, leading to the best adhesion score. The surface of the heart was smooth and the coronary vessels were clearly identifiable. The ePTFE membrane (...truncated)