Date of Award


Document Type

Campus Access Dissertation


Biomedical Science

First Advisor

Edie Goldsmith


Mechanical load (tension, compression, strain and stress) is constantly applied to the cardiac extracellular matrix (ECM) at the cellular level (i.e. myocyte contraction and/or fibroblast focal adhesions) or globally through hemodynamic pressures. While mechanical load can be an important factor in maintaining tissue homeostasis, little is known about how myocardial cells respond to mechanical loading in a 3D environment or how much tension myocardial cells exert on the ECM in vitro. The body of work described herein investigated the affects mechanical loading (5% and/or 10% peak strain) had on 1) RBL-2H3 cell degranulation; 2) the influences RBL-2H3 cells have on fibroblast function; and 3) age-dependent differences in cardiac fibroblast gene expression. In addition, we examined the differences in ECM remodeling behavior by neonatal and adult cardiac fibroblasts and analyzed changes in protein and gene expression, on 2-dimensional and 3-dimensional matrices, of the following collagen receptors: domain receptor 1 and 2 (DDR1, DDR2),and &beta 1 integrin, and the contractile protein, &alpha-smooth muscle actin (&alpha-SMA) . We report that mechanical loading induces RBL-2H3 degranulation via RGD integrins and regulates age-dependent differences in collagen I and III gene expression in neonatal and adult fibroblasts. We also report that load does not influence RBL cell mediated fibroblast activation or adult and neonatal cell fibroblast to myofibroblast differentiation. Our cell-mediated strain studies show neonatal fibroblasts apply greater strain in a 3D matrix and have increased expression of &alpha-smooth muscle actin and &beta 1 integrin compared to adult fibroblasts. To our knowledge, this is the first report of load-mediated activation of RBL-2H3 cells and cardiac fibroblasts in a 3D environment. Our results reinforce the role mechanical loading has on cell behavior and the loading system described provides an in vivo like environment to study cellular responses to changes in the mechanical environment.