Engineered biomaterials to modulate cell-cell signaling for the robust expansion of stem cells - PROJECT SUMMARY
Adult stem cells hold significant therapeutic potential to treat many diseases and injuries. For example, neural
progenitor cells (NPCs) are currently being investigated in over 20 clinical trials for use in a variety of indications.
Despite their significant clinical relevance, we currently lack the biological mechanistic understanding to
efficiently expand NPCs in vitro, even as neurospheres, while maintaining their undifferentiated, regenerative
stem phenotype. Recently, 3D matrices have emerged as a tool for stem cell expansion; unfortunately, once
encapsulated, NPCs commonly lose their stemness and ability to proliferate. Loss of NPC stemness is also
observed in vivo throughout the aging process and in pathological disease states causing diminished ability for
NPC self-renewal and biased differentiation. These phenotypic abnormalities are due in part to complex
environmental changes in the stem cell niche including altered extracellular matrix biochemical and
biomechanical properties. Therefore, we propose the use of a 3D in vitro hydrogel culture platform with controlled
matrix biochemistry and biomechanics that will enable the exploration of previously untestable hypotheses on
the mechanisms by which the surrounding cell microenvironment influences NPC maintenance, expansion, and
differentiation. We will use a family of protein-engineered hydrogels to understand the impact of the matrix
microenvironment on human iPSC-derived NPC (hNPC) phenotype. Specifically, we will study the role of matrix
biochemical and biomechanical properties on activation of the N-cadherin signaling pathway and downstream
hNPC phenotype. In Aim 1, we tune the biochemical cues presented within elastin-like protein (ELP) hydrogels
to display a N-cadherin-mimetic peptide. We hypothesize that cell engagement with the artificial N-cadherin will
result in downstream -catenin signaling, stemness maintenance, and enhanced symmetric proliferation
compared to neurosphere controls. In Aim 2, we tune the biomechanical cues presented by the recombinant
ELP hydrogels to enable dynamic matrix remodeling through viscoelastic stress relaxation. We hypothesize that
dynamic matrix remodeling will result in increased cell-cell contacts, induction of cellular-based N-cadherin
signaling, stemness maintenance, and enhanced symmetric proliferation compared to neurosphere controls. In
Aim 3, we evaluate the hypothesis that control of specific matrix material properties to tune N-cadherin
presentation and ELP hydrogel mechanics alters outside-in signal transduction that biases hNPC differentiation.
The biological mechanisms underlying this process will be explored via changes in nuclear architecture (lamin
expression and nuclear morphology) and epigenetics (histone modification and chromosomal organization).
Further mechanistic insight will be explored using inhibitors and agonists of key mechanotransduction signaling
pathways. Our engineered, modular hydrogels allow us to explore the mechanisms by which specific matrix cues
regulate hNPC stem maintenance and differentiation. Given the immense regenerative potential of these cells,
our findings will inform the design of a robust in vitro platform for the clinical expansion of hNPCs.
