title: The use of covalently immobilized stem cell factor to selectively affect hematopoietic stem cell activity within a gelatin hydrogel.
abstract: Hematopoietic stem cells (HSCs) are a rare stem cell population found primarily in the bone marrow and responsible for the production of the body's full complement of blood and immune cells. Used clinically to treat a range of hematopoietic disorders, there is a significant need to identify approaches to selectively expand their numbers ex vivo. Here we describe a methacrylamide-functionalized gelatin (GelMA) hydrogel for in vitro culture of primary murine HSCs. Stem cell factor (SCF) is a critical biomolecular component of native HSC niches in vivo and is used in large dosages in cell culture media for HSC expansion in vitro. We report a photochemistry based approach to covalently immobilize SCF within GelMA hydrogels via acrylate-functionalized polyethylene glycol (PEG) tethers. PEG-functionalized SCF retains the native bioactivity of SCF but can be stably incorporated and retained within the GelMA hydrogel over 7 days. Freshly-isolated murine HSCs cultured in GelMA hydrogels containing covalently-immobilized SCF showed reduced proliferation and improved selectivity for maintaining primitive HSCs. Comparatively, soluble SCF within the GelMA hydrogel network induced increased proliferation of differentiating hematopoietic cells. We used a microfluidic templating approach to create GelMA hydrogels containing gradients of immobilized SCF that locally direct HSC response. Together, we report a biomaterial platform to examine the effect of the local presentation of soluble vs. matrix-immobilized biomolecular signals on HSC expansion and lineage specification. This approach may be a critical component of a biomaterial-based artificial bone marrow to provide the correct sequence of niche signals to grow HSCs in the laboratory.
authors.affiliation: Dept. Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
authors.forename: Bhushan P
authors.initials: BP
authors.lastname: Mahadik
authors.affiliation: Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
authors.forename: Sara
authors.initials: S
authors.lastname: Pedron Haba
authors.affiliation: Dept. Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States.
authors.forename: Luke J
authors.initials: LJ
authors.lastname: Skertich
authors.affiliation: Dept. Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States; Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, United States. Electronic address: bharley@illinois.edu.
authors.forename: Brendan A C
authors.initials: BA
authors.lastname: Harley
mesh_terms: D000178:Acrylamides / Q000737:chemistry; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D005780:Gelatin / Q000494:pharmacology*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000494:pharmacology*; D055767:Immobilized Proteins / Q000494:pharmacology*; D008810:Mice, Inbred C57BL; D044085:Microfluidics; D011092:Polyethylene Glycols / Q000737:chemistry; D019089:Stem Cell Factor / Q000494:pharmacology*; D034421:Sus scrofa
chemical_list: D000178:Acrylamides; D055767:Immobilized Proteins; D019089:Stem Cell Factor; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols; D005780:Gelatin; C045985:methacrylamide
keywords: Bone marrow; Cell activation; Growth factor; Hydrogel; Stem cell