title: Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression.
abstract: Understanding the passive mechanical properties of infarcted tissue at different healing stages is essential to explore the emerging biomaterial injection-based therapy for myocardial infarction (MI). Although rats have been widely used as animal models in such investigations, the data in literature that quantify the passive mechanical properties of rat heart infarcts is very limited. MI was induced in rats and hearts were harvested immediately (0 day), 7, 14 and 28 days after infarction onset. Left ventricle anterioapical samples were cut and underwent equibiaxial and non equibiaxial tension followed by uniaxial compression mechanical tests. Histological analysis was conducted to confirm MI and to quantify the size of the induced infarcts. Infarcts maintained anisotropy and the nonlinear biaxial and compressive mechanical behaviour throughout the healing phases with the circumferential direction being stiffer than the longitudinal direction. Mechanical coupling was observed between the two axes in all infarct groups. The 0, 7, 14 and 28 days infarcts showed 438, 693, 1048 and 1218kPa circumferential tensile moduli. The 28 day infarct group showed a significantly higher compressive modulus compared to the other infarct groups (p=0.0060, 0.0293, and 0.0268 for 0, 7 and 14 days groups). Collagen fibres were found to align in a preferred direction for all infarct groups supporting the observed mechanical anisotropy. The presented data are useful for developing material models for healing infarcts and for setting a baseline for future assessment of emerging mechanical-based MI therapies.
authors.affiliation: Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory 7925, South Africa; Department of Biomedical Engineering, University of Medical Sciences and Technology, P.O. Box 12810, Khartoum, Sudan.
authors.forename: Mazin S
authors.initials: MS
authors.lastname: Sirry
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, MS 39762, USA.
authors.forename: J Ryan
authors.initials: JR
authors.lastname: Butler
authors.affiliation: Tissue Bioengineering Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, MS 39762, USA.
authors.forename: Sourav S
authors.initials: SS
authors.lastname: Patnaik
authors.affiliation: Tissue Bioengineering Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, MS 39762, USA.
authors.forename: Bryn
authors.initials: B
authors.lastname: Brazile
authors.affiliation: Tissue Bioengineering Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, MS 39762, USA.
authors.forename: Robbin
authors.initials: R
authors.lastname: Bertucci
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, MS 39762, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Claude
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, MS 39762, USA.
authors.forename: Ron
authors.initials: R
authors.lastname: McLaughlin
authors.affiliation: Cardiovascular Research Unit, Chris Barnard Division of Cardiothoracic Surgery, University of Cape Town, Observatory 7925, South Africa.
authors.forename: Neil H
authors.initials: NH
authors.lastname: Davies
authors.affiliation: Tissue Bioengineering Laboratory, Department of Agricultural and Biological Engineering, Mississippi State University, MS 39762, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Liao
authors.affiliation: Division of Biomedical Engineering, Department of Human Biology, University of Cape Town, Observatory 7925, South Africa; Centre for High Performance Computing, Rosebank 7700, South Africa; Bioengineering Science Research Group, Engineering Sciences, Faculty of Engineering and the Environment, University of Southampton, Southampton SO171BJ, UK. Electronic address: thomas.franz@uct.ac.za.
authors.forename: Thomas
authors.initials: T
authors.lastname: Franz
mesh_terms: D000818:Animals; D006352:Heart Ventricles / Q000473:pathology*; D008297:Male; D009203:Myocardial Infarction / Q000473:pathology*; D009206:Myocardium / Q000473:pathology*; D011312:Pressure; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical
keywords: Biaxial; Collagen; Compression; Mechanical testing; Myocardial infarction; Rat