Date of Award

8-2018

Degree Type

Thesis

Degree Name

Master of Science in Biomedical Engineering

Department

Biomedical Engineering

Committee Chair

Sarah Calve

Committee Member 1

Alyssa Panitch

Committee Member 2

Luis Solorio

Abstract

Volumetric muscle loss (VML) occurs when skeletal muscle injury is too large for the body’s self-regenerative capabilities. As a consequence, fibrotic tissue fills the void, which reduces muscle functionality and limb movement. In the military, VML occurs mainly through explosions which represent more than 70% of total war injuries. Otherwise, the most common causes are traumatic accidents, tumor ablation, and musculoskeletal diseases.

Although a wide variety of natural and synthetic scaffolds have been studied with the purpose of providing the appropriate structural support, to date no scaffold has been able to significantly restore muscle functionality after VML. Satellite cells, adult stem cells within the muscle capable of self-renewal and restoring smaller injuries, are sensitive to the stiffness and composition of the surrounding environment. Scaffolds that only address structural support are not sufficient to restore muscle functionality and instead need to be designed to promote satellite cell activation as well. We hypothesized that generating a scaffold that mimicked the stiffness and composition of regenerating muscle tissue would promote good satellite cell recruitment into the scaffold.

One of the main extracellular matrix (ECM) molecules that is upregulated during scar-free repair is hyaluronic acid (HA). Therefore, thiol-modified HA and polyethylene glycol diacrylate (PEGDA) hydrogels were generated and functionalized with ECM-derived peptides that are highly upregulated during muscle regeneration, including RGD (found in fibronectin), IKVAV (found in laminin) or VFDNFVLK (found in Tenascin-C). Scaffolds with different stiffness were created by increasing the percentage of HA in the hydrogel. To test our hypothesis, we conducted an in vitro study quantifying the influence of HA stiffness and peptide functionalization on satellite cells and fibroblast cell proliferation, migration and gene expression. Results showed high promise for the use of HA hydrogels functionalized with the laminin peptide, IKVAV, due the promotion of cell spreading while enhancing cell migration, and the increase in gene expression of factors correlated with myogenic cell activation.

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