Document Type

Dissertation

Date of Award

2025

Keywords

Autonomic neuron, Cardiomyocytes, Co-culture, Heterotypic models, Innervation, Stem cell

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Engineering

First Advisor

Tracy Hookway

Second Advisor

Sha Jin

Third Advisor

Ying Wang

Abstract

The cardiac microenvironment is a complex system of multicellular interactions that enables proper heart function. In native heart muscle, sympathetic neurons (SN) and parasympathetic neurons (PSN) modulate the beat rate of cardiomyocytes (CM) to maintain homeostasis. Pluripotent stem cells can differentiate into CM, but differentiated CMs are fetal-like, with a high beat rate, and lack organized sarcomeric structure. Recent reports of co-cultured pluripotent CM/SN pairs have reported electrophysiological changes in the SN (increased upstroke velocity). However, interpretation of these results are obscured by the differences in co-culture parameters between studies (stage of development, co-culture duration, etc.). The goal of this work was to improve autonomic neuron differentiation efficiency (iPSC-ANs), establish a platform for CM/AN co-culture, and investigate the influence of these parameters on CM/AN crosstalk/responses.

A protocol was developed in-house that incorporated in vivo developmental cues. The differentiated progeny were characterized during/after optimizing initial seeding density, RA concentration, and BMP4 concentration. The resulting D19 iPSC-AN population was quantified with Stardist (FIJI plugin) as 50+% NF+, 50+% Phox2B+, and 40% Sox10+. Differentiated autonomic neurons were co-cultured with cardiomyocytes to investigate CM/AN morphologic changes. The selected media composition and CM/AN ratio maintained viable neurocardiac co-cultures. AN projections interacted with CMs, and exhibited target specificity in vitro. CMs continued to contract during co-culture reorganization and was recorded for analysis. There was a significant decrease in the beat rate of co-cultured CMs (p value < 0.001) in all CM+AN co-culture  experiments. After completing a systematic analysis of co-culture experiments for contraction strength, surprisingly early CMs co-cultured with early ANs contracted significantly stronger (p value < 0.05, n = 32) than late CMs co-cultured with late ANs.

The field of cardiac co-culture research is growing, and a systematic analysis pipeline streamlines observed relationships and conclusions about CM/AN crosstalk. This body of work entails a reliable protocol for iPSC-AN derivation and neurocardiac in vitro modeling for multiple CM/AN combinations. I have provided fundamental understanding of CM behavior in heterotypic models along with insight on AN behavior. CM/AN behavior serves as a building block for more complex CM multicellular models. Consistent CM contraction rate in the presence of ANs suggests that a systematic approach to co-culture could further improve cardiomyocyte Engineered Heart Tissue (EHT) research.

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