Abstract 21346: Engineered Extracellular Matrix Bioactivity and Mechanics Modulate Cardiac Myocyte Phenotype
Cardiac remodeling is accompanied by alterations in the composition and mechanical properties of the extracellular matrix (ECM). The altered viscoelastic and bioactive properties of the ECM microenvironment disrupts the structural and functional integrity of myocardial tissue. Cardiac tissue engineering strategies involve the replacement of the diseased myocardium with new cells and /or bioactive materials. The study was designed to optimize the response of cardiac myocytes to engineered ECM proteins of varying bioactivity and stiffness. Neonatal myocytes were cultured on two model systems: polyacrylamide (PA) and semi-synthetic hyaluronan (HA) hydrogels (HyStem) of varying stiffness. PA gels were coated with either fibronectin (Fn) or Collagen type I. HyStem gels had either Fn, Collagen type I or a combination of the two incorporated either covalently or non-covalently throughout the hydrogel. After 48 hours of culture cells were fixed and stained for f-actin, α-actinin and vinculin. On soft fibronectin coated PA gels (1kPa) myocytes developed sparse f-actin fibers and were lacking in sarcomeric organization. At physiological stiffness (30kPa), cells showed striated f-actin and organized myofibrils. On stiffer substrates (>60kPa), cells displayed a phenotype with prominent f-actin “stress fiber-like” filaments and poorly defined myofibril architecture. The response (cell shape, myofibril assembly and organization) to collagen coated PA gels was highly attenuated implicating the importance of ligand type and activity on myocyte remodeling. Surprisingly, myocyte structure and contractile function (105% increase) on relatively soft (<1kPa) * Fn containing HyStem (HA) gels was highly preserved in comparison to Fn/Col-coated PA-gels of similar stiffness. These findings provide the rationale for engineering a new class of soft (injectable) biologically-responsive hybrid hydrogels for re-remodeling the myocardial microenvironment.
- © 2010 by American Heart Association, Inc.