Prediction of extracellular matrix stiffness in engineered heart valve tissues based on nonwoven scaffolds

Abstract

The in vitro development of tissue engineered heart valves (TEHV) exhibiting appropriate structural and mechanical characteristics remains a significant challenge. An important step yet to be addressed is establishing the relationship between scaffold and extracellular matrix (ECM) mechanical properties. In the present study, a composite beam model accounting for nonwoven scaffold-ECM coupling and the transmural collagen concentration distribution was developed, and utilized to retrospectively estimate the ECM effective stiffness in TEHV specimens incubated under static and cyclic flexure conditions (Engelmayr Jr et~al. in Biomaterials 26(2):175-187 2005). The ECM effective stiffness was expressed as the product of the local collagen concentration and the collagen specific stiffness (i.e., stiffness/concentration), and was related to the overall TEHV effective stiffness via an empirically determined scaffold-ECM coupling parameter and measured transmural collagen concentration distributions. The scaffold-ECM coupling parameter was determined by flexural mechanical testing of polyacrylamide gels (i.e., ECM analogs) of variable stiffness and associated scaffold-polyacrylamide gel composites (i.e., engineered tissue analogs). The transmural collagen concentration distributions were quantified from fluorescence micrographs of picro-sirius red stained TEHV sections. As suggested by a previous structural model of the nonwoven scaffold (Engelmayr Jr and Sacks in J Biomech Eng 128(4):610-622, 2006), nonwoven scaffold-ECM composites did not follow a traditional rule of mixtures. The present study provided further evidence that the primary mode of reinforcement in nonwoven scaffold-ECM composites is an increase in the number fiber-fiber bonds with a concomitant increase in the effective stiffness of the spring-like fiber segments. Simulations of potential ECM deposition scenarios using the current model indicated that the present approach is sensitive to the specific time course of tissue deposition, and is thus very suitable for studies of ECM formation in engineered heart valve tissues.

Cardiogenic differentiation of mesenchymal stem cells with gold nanoparticle loaded functionalized nanofibers

“…It is of utmost importance to clearly elucidate the relationship between the mechanical properties of the scaffold and the cellsecreted ECM which decides the strength of implanted scaffolds [17]. The ECM secreted by the cardiomyocytes was found to be a natural inducer which promotes cardiogenic differentiation of the stem cells [18].…”

Multiscale Biomimetic Topography for the Alignment of Neonatal and Embryonic Stem Cell-Derived Heart Cells

“…15,19 However, commonly used cardiomyocyte (CM) culture and tissue engineering methods do not provide the proper environmental factors to allow CM to respond morphologically, mechanically, or physiologically as they do in the native tissue. 15,20 Fabrication of cell culture substrates that mimic the native environment found in the heart may improve the culture conditions of cells for the development of functional cardiac tissue. [21][22][23][24] The alignment of CM has been studied for the last decade using different microfabrication (e.g., microcontact printing, abrasion, photolithography, hot embossing, electrospinning, and laser ablation) approaches.…”

Foreword to the special issue on “Theoretical, experimental, and computational aspects of growth and remodeling”

“…The growth model is able to predict parameters that change during growth that are difficult to measure such as depthdependent biomechanical properties. Engelmayr and Sacks (2007) aim for a relationship between scaffold and extracellular (ECM) matrix mechanical properties. The authors retrospectively predict the ECM effective stiffness in tissue-engineered heart valve specimens by means of a meso-scale composite beam model accounting for nonwoven scaffold-ECM coupling and variations in the transmural collagen concentration distribution.…”