Date of Award

Spring 1-1-2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical & Biochemical Engineering

First Advisor

Stephanie J Bryant

Second Advisor

Christopher N Bowman

Third Advisor

Leslie A Leinwand

Abstract

Coronary heart disease has become increasingly prevalent in the U.S. and worldwide, and now affects over one million Americans annually. The damaged tissue that results from cardiac injury lacks the ability to regenerate, but no therapies exist to regenerate heart tissue. Tissue engineering is one promising method through which cardiac tissue could be regenerated. This research focuses on developing a tissue engineered hydrogel scaffold using a design regimen that facilitates nutrient transport, tensile properties, and cardiomyocyte adhesion and alignment. A porous structure incorporated into the bulk of the scaffold was selected as a means to enhance nutrient transport. Variations in hydrogel chemistry, crosslinking density and presence and size of pores between 50-200 ìm allowed the scaffold properties to be tailored more closely to that of native tissue. Alteration of hydrogel formulation and chemistry of poly (ethylene glycol) (PEG) and poly (2-hydroxyethyl methacrylate) (pHEMA) led to increased strength or increased ultimate tensile strain. Towards designing hydrogels that promote cardiomyocyte adhesion, several proteins and peptides were examined. Results indicated that biological modification of the surface through covalent linkage of whole proteins, laminin or collagen I, supported cell spreading, the development of a contractile network, and phenotype. Interestingly, cardiomyocytes did not adhere to the cell-adhesive peptide sequence arginine-glycine-aspartic acid (RGD), which is commonly employed to support cell attachment. Changes in stiffness of protein-modified hydrogels produced changes in cardiomyocyte gene expression of several genes important in maturation and disease pathways. However, the changes in gene expression based on stiffness and time did not indicate maturation nor disease on the substrates within the tested stiffness range. To mimic the aligned cellular architecture found in muscle, scaffolds were fabricated with an array of 3D surface channels with dimensions between 40-200 mm. Muscle cells cultured several layers thick and wide aligned within these channel structures, and alignment improved with decreases in channel width and increases in channel depth. These findings aid in development of a tissue engineered scaffold for cardiac muscle that can simultaneously incorporate architecture, mechanical properties and biological cues to promote a healthy cardiomyocyte phenotype.

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