Extracellular Elastin Assembly and Vascular Hyperproliferation: Connections for Treatment and Tissue Engineering

Date of Award

Spring 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Cellular and Molecular Physiology

First Advisor

Qyang, Yibing

Abstract

Elastin is the load-bearing extracellular matrix protein complex that endows the aorta with the recoil necessary to propagate blood to the peripheral circulation following systolic ejection from the heart. The assembly of the elastin complex occurs early in perinatal development and degrades over the course of a human lifetime, leading to arterial stiffening and elevated blood pressure. Although this complex assembly process occurs seamlessly in vivo, it has been a large obstacle in the field to replicate this process in vitro, hampering efforts to engineer elastin-rich grafts for transplantation and to study and develop curative treatments for elastin-associated pathologies. Herein, I investigated how induced pluripotent stem cells (iPSCs) can be used to study elastin fiber assembly. Unlike primary cell lines, iPSCs are self-renewable and can differentiate into almost any cell type in the body, including elasto-generative smooth muscle cells. I utilize this capability to study the interconnections between the extracellular matrix and the phenotype of vascular smooth muscle in cells derived from both healthy and elastin insufficient donors. From this work, I discovered how the polyphenol epigallocatechin gallate (EGCG) can facilitate the extracellular assembly of elastin fibers and applied this to the contexts of tissue engineering and disease rescue. Further, I developed a doxycycline-inducible expression vector for elastin, which was genetically edited into iPSCs, to be used in tandem with EGCG to augment the production of elastin in engineered grafts. By increasing the deposition of elastin in the extracellular matrix, I was also able to characterize how the composition of the matrix, and thus its inherent elastic extensibility, can directly affect the phenotype of smooth muscle cells via mechanotransduction. I additionally demonstrated how the EGCG-facilitated assembly of elastin fibers can be used to promote the physiological rescue of elastin insufficient mice following an in utero treatment regimen, establishing a preclinical model for the future treatment of human elastinopathy. Together, this work provides new insights into the elastin field, a foundation for improving the physiology of engineered vascular grafts, and a promising avenue for therapeutic development.

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