Autologous or bovine pericardium for aortic cusp replacement? Histomorphological and biomechanical properties as decision making tools
Authors: Baehring S , Dittfeld C , Alexiou K , Welzel C , Jannasch A , Matschke K , Tugtekin S M 
Published: October 2022

Abstract

Background/Introduction
Aortic valve cusp replacement using autologous pericardium is a promising technique. Expected advantages are reduced immune response, proper biomechanics and lower treatment expenses. During surgery decision for preferred pericardium segment is based on visual criteria. Autologous pericardium can be affected by patient's condition and age. Bovine pericardium, also the basic material for aortic valve prostheses, is easy available and carefully pre-examined. In this study, the homogeneity of tissue thickness, elastic modulus, vessel density and ECM components of GA-treated residual pericardia after surgery is compared with bovine pericardia equivalently treated.

Purpose
Aim of the study is the comparison of homogeneity of remaining autologous pericardium after surgical aortic valve replacement with bovine pericardia to evaluate and classify the individual applicability.

Methods
Up to 12 samples of human (n=7) or bovine (n=3) pericardia were analysed. Tissues were treated with 0.6% glutaraldehyde according to surgical protocol. Picrosiriusred- and HE-staining were performed (three edges per separated leaflet). Vessel or collagen content was determined with Zen Blue resp. Fiji software (colour deconvolution plugin, user threshold values). Sample thickness was measured via thickness gauge FD50 before uniaxial tensile testing. Hydroxyproline content was determined and related to dry weight. T-Test or ANOVA were used to test inter-species or intra-individual differences, respectively.

Results
Human pericardia contain with 64.66±3.85% less collagenous fibres compared to bovine pericardia (86.01±1.713%); their vessel density is with 29.46±3.73 mm–2 significantly higher than in bovine samples (12.34±1.636 mm–2). In addition, human pericardia are with 367.7±59.2 μm significantly thinner than bovine (524.4±96.8 μm). Tensile testing (human: 36.00±15.17 MPa; bovine: 41.30±7.767 MPa) also revealed significant differences. With 77.80±11.76 mg/g merely a trend was observed for a lower hydroxyproline content in human samples (bovine 93.16±5.130 mg/g). ANOVA analyses of human pericardia illustrate significant differences for all properties, thus thickness, elastic modulus and hydroxyproline and collagen content between the individual human pericardium samples. In contrast, bovine pericardia showed an intra-individual difference only for the parameter of tissue thickness.

Conclusion
Human and bovine pericardia differ in histological and biomechanical parameters. In contrast to bovine pericardia, individual human pericardia were significantly different in most parameters investigated, leading to the conclusion that autologous materials are critically more heterogeneous than xenogeneic tissues. Vessel density in human pericardium was twofold higher than in bovine pericardia and can result in a higher risk for calcification.

Funding Acknowledgement
Type of funding sources: Public Institution(s). Main funding source(s): TU Dresden