Date of Award

Spring 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Experimental Pathology

First Advisor

Qyang, Yibing

Abstract

Tissue engineering and regenerative medicine are relatively new fields that aim to combine principals of chemistry, physics and biology to recreate tissues of the body within lab settings. By utilizing these concepts, novel tissues can be created from entirely biologic material for use as therapeutic replacement tissues. The advent of stem cell technology has been an incredible enabling factor for tissue engineering as a field, especially that of human induced pluripotent stem cells (hiPSCs). hiPSCs are a class of stem cell that may be readily produced using non-invasively derived patient samples that are subsequently transfected with what are commonly known as the Yamanaka factors (Oct4, Sox2, Klf4, C-myc) that will cause epigenetic reprogramming of these patient specific cells into a stem cell phenotype. hiPSCs do not display replicative fatigue as seen in somatic cell populations, in addition to being able to generate any tissue of the body. Using these cells enables researchers to create complex, multicellular tissues in the lab from this theoretically inexhaustible cell source of the patients’ own cells for regenerative medicine applications such as the treatment of cardiovascular diseases. Cardiovascular disease is one of the leading causes of death worldwide and can affect patients at any stage of life. Some patients are born with physiologic defects in their heart that lead to life threatening conditions such as single ventricle diseases (SVDs). SVDs represent a class of congenital disorder that may occur through a variety of physiologic and genetic mechanisms, but ultimately results in a single functional ventricle forming rather than the standard two. Due to the decreased output of the heart, in addition to the excess stress placed on that single ventricle, patients suffer a variety of complications, including abhorrent remodeling of the pulmonary artery, mixing of oxygenated and deoxygenated blood and valvular dysfunction that leads to a 70% mortality rate by age 5 without surgical intervention. Corrective surgery for SVD patients traditionally relies on a series of reconstructive surgeries known as the Fontan procedure. The main goal of the Fontan procedure is to re-route blood flow coming from the body to flow directly into the pulmonary artery, while the single ventricle is responsible for generating pressures to drive both systemic and pulmonary flows. To complete the Fontan a vascular conduit is required to connect the inferior vena cava to the pulmonary artery. Although effective, current Fontan conduits are limited by their inability to aid in the pumping of blood into the pulmonary circulation. Because of this, it was hypothesized that a tissue engineered pulsatile conduit (TEPC) could improve Fontan patient morbidity by aiding in circulation through the pulmonary system by producing contractile force. Several design strategies were tested for production of a functional TEPC. Ultimately, we found that porcine extracellular matrix (ECM)-based engineered heart tissue (EHT) composed of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and primary cardiac fibroblasts (HCF) wrapped around decellularized human umbilical artery (HUA) made an efficacious basal TEPC. Importantly, the TEPCs showed effective electrical and mechanical function. Initial pressure readings from our TEPC in vitro (0.68 mmHg) displayed efficient electrical conductivity enabling them to follow electrical pacing up to a 2 Hz frequency. This work represents a proof of principle study for our current TEPC design strategy. Refinement and optimization of this promising TEPC design will lay the groundwork for testing the construct’s therapeutic potential in the future. Together this work represents a progressive step toward developing an improved treatment for SVD patients and can help the lives of patients even from birth.

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