Jonathan Baio

Abstract

The heart and its cellular components are profoundly altered by missions to space and injury on Earth. Increasing evidence has identified that one such alteration induced by spaceflight is the promotion of the efficacious use of stem cells in therapies on Earth. For this reason, neonatal and adult human cardiovascular progenitor cells (CPCs) were cultured aboard the International Space Station (ISS). Subsequently, we assessed the effects of mechanical unloading on developmental properties and signaling. Spaceflight induced the expression of genes that are typically associated with an earlier state of cardiovascular development. In particular, in neonatal CPCs, we measured increased expression of pre-cardiac and developmental regulatory (Bmp and Tbx) genes; decreased expression of mesodermal derivative markers, including endothelial tube formation; and enhanced proliferative potential, as indicated by cell growth and cell cycle analysis. Interestingly, these changes were not observed in adult CPCs. To understand the mechanism by which such changes occurred in neonatal CPCs, we assessed the expression of mechanosensitive small RhoGTPases. Given the effect of these molecules on intracellular calcium levels, we evaluated changes in non-canonical Wnt/calcium signaling. ISS-cultured CPCs exhibited elevated levels of calcium handling and signaling

genes, which corresponded to activation of protein kinase C alpha (PKCα), a calciumdependent protein kinase, and Akt, a regulator of stem cell self-renewal, after 30 days. To explore the effect of calcium induction in neonatal CPCs, we activated PKCα using hWnt5a treatment on Earth, which resulted in an induction of early cardiovascular developmental marker expression. Interestingly, markers of the sinoatrial node, which may represent embryonic myocardium maintained in its primitive state, were induced by culture of neonatal CPCs aboard the ISS, which was modeled on Earth, at least in part, using the calcium signaling activators angiotensin II and hWnt5a. To test whether such signaling could induce sinoatrial nodal gene development on Earth, we treated neonatal CPCs with angiotensin II and observed the reliable induction of a sinoatrial nodal phenotype. We found that, in neonatal CPCs, spaceflight induces PKCα and Akt signaling, promotes the induction of an earlier developmental state, and highlights signaling events that may underpin biological pacemaker development on Earth.

LLU Discipline

Anatomy

Department

Basic Sciences

School

School of Medicine

First Advisor

Kearns-Jonker, Mary

Second Advisor

Oberg, Kerby C.

Third Advisor

Soriano-Castell, Salvador

Fourth Advisor

Wilson, Christopher G.

Fifth Advisor

Xu, Chunhui

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

2018

Date (Title Page)

6-2018

Language

English

Library of Congress/MESH Subject Headings

Cardiovascular System; Reduced gravity environments;

Subject - Local

Progenitor Cell Development; Spaceflight

Type

Dissertation

Page Count

200

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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