Effects of electrophysiological manipulation on differentiation and wound healing capacity of human mesenchymal stem cells.
Electrophysiology is an important regulator of cell proliferation, differentiation,
migration, wound healing, and tissue regeneration. Stem cells participate in wound
healing and regeneration in many systems, yet the role of electrophysiology on stem cell
behavior has not been widely studied. In this work, we present evidence for a functional
role for membrane potential (Vmem) in hu... read moreman mesenchymal stem cell (hMSC) differentiation
toward osteogenic (OS) and adipogenic (AD) lineages. Endogenous hyperpolarization
accompanies and is required for OS and AD differentiation. Cells undergoing OS
differentiation responded to artificially-induced depolarization or hyperpolarization by
suppressing or augmenting differentiation, respectively. That stem cell differentiation
responds to changing Vmem levels suggests that Vmem can be used as a control point for
directing stem cell behavior for therapeutic applications and tissue engineering
efforts. We investigated the mechanisms underlying voltage signaling in hMSCs.
Modulation of both Ca2+ signaling and ATP signaling attenuated the effects of
depolarization, suggesting a role for Ca2+ channels and purinergic receptors in the
voltage-sensing pathway. We also identified several ion channels, including L-type Ca2+
channels, inward rectifying K+ channels, and Ca2+-sensitive K+ channels, which may be
involved in these pathways during depolarization. To further investigate the pathways
that are controlling and controlled by voltage modulation, we performed genome-wide
expression analysis of depolarized and hyperpolarized hMSCs undergoing OS
differentiation. The transcriptional signature of Vmem-modulated cells resembled that of
OS cells rather than undifferentiated cells, implying that voltage signals target some,
but not all, pathways involved in differentiation. We present several data analysis
approaches that uncover a number of Vmem-responsive genes and functions, which are
promising candidates for future work on voltage-sensing mechanisms. Finally, we
investigated the therapeutic potential of electrophysiological modulation of hMSCs by
developing in vitro models of wound healing as platforms in which to study Vmem effects.
We report some evidence pointing to depolarization-stimulated increases in cell
repopulation and OS differentiation in the wound. We also demonstrate the ability to
study paracrine signaling between osteoblasts and neurons in these models, which
suggests that these models can be further developed to simulate the complexity of the in
vivo wound environment.
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Biomedical Engineering.
Advisor: David Kaplan.
Committee: Michael Levin, Lauren Black, and Gordana Vunjak-Novakovic.
Keyword: Biomedical Engineering.read less