Soluble factors and remodeling in a synthetic stem cell niche

Hematopoietic stem cells produce the body’s entire complement of blood and immune cells, in a process known as hematopoiesis. Producing half a trillion cells daily, this rare population (<0.01% of human bone marrow) possess the ability to produce multiple cell lines (differentiation) and stem cell daughters (self-renewal). HSCs are found throughout the body but primarily reside in the adult bone marrow, in specialized compartments termed the niche. Within the niche is a host of biophysical, cellular, and soluble factor cues that combine in temporally and spatially organized zones which elicit distinct responses from resident HSCs. Clinically, HSC transplants are the most widely used regenerative therapy, treating disorders of the blood and immune system e.g., anemias, leukemias, and myelo-ablative chemoradiation treatments. However, the rarity of the cells and scarcity of appropriately matched donors (<25% in some demographics) has necessitated methods to expand and maintain HSC populations ex vivo. Development of expansion methods requires identification of essential features of the native HSC microenvironment for design of tissue engineering constructs. Herein, we describe the use of gelatin-based hydrogels to provide biophysical cues, recapitulating mechanical features of the niche. Cellular cues are provided by heterotypic cultures of niche-associated mesenchymal stromal cells (MSCs) and HSCs. The cell-cell interactions are mediated by biotransport of secreted soluble factors, which are in turn mediated by the biophysical properties of the matrix. This interdependence motivates a series of investigations to define the role of material properties on transport-mediated cell-cell interactions as well as the role of cell-mediated remodeling on dynamic cell interactions. We identified a regime of HSC-MSC interactions that improve maintenance of HSCs in an environment with restricted biotransport. Employing mathematical modeling techniques, features of the artificial niche (soluble factors) were correlated to hematopoietic activity. To adapt conventional macro-scale hydrogel platforms to study HSC activity at single cell resolution, this thesis also describes development of micro-scale (~150 µm) droplet hydrogels with control over cell-cell interactions and enables high-throughput generation of identical microenvironments. Overall, these studies demonstrate that dynamic cell-cell signaling are essential features in artificial niche for ex vivo HSC culture and expansion.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Materials Science & Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2021

Author dc:creator

• Gilchrist, Aidan E

Contributors dc:contributor

• Harley, Brendan
• Das Neves Barbosa Leal Lauten, Cecelia
• Sottos, Nancy
• Cheng, JianJun

• biomaterials
• hematopoietic stem cells
• stem cell engineering

Statement dc:rights

• Copyright 2020 Aidan Gilchrist

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/110616

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/110616