title: A tunable hydrogel system for long-term release of cell-secreted cytokines and bioprinted in situ wound cell delivery.
abstract: For many cellular therapies being evaluated in preclinical and clinical trials, the mechanisms behind their therapeutic effects appear to be the secretion of growth factors and cytokines, also known as paracrine activity. Often, delivered cells are transient, and half-lives of the growth factors that they secrete are short, limiting their long-term effectiveness. The goal of this study was to optimize a hydrogel system capable of in situ cell delivery that could sequester and release growth factors secreted from those cells after the cells were no longer present. Here, we demonstrate the use of a fast photocross-linkable heparin-conjugated hyaluronic acid (HA-HP) hydrogel as a cell delivery vehicle for sustained growth factor release, which extends paracrine activity. The hydrogel could be modulated through cross-linking geometries and heparinization to support sustained release proteins and heparin-binding growth factors. To test the hydrogel in vivo, we used it to deliver amniotic fluid-derived stem (AFS) cells, which are known to secrete cytokines and growth factors, in full thickness skin wounds in a nu/nu murine model. Despite transience of the AFS cells in vivo, the HA-HP hydrogel with AFS cells improved wound closure and reepithelialization and increased vascularization and production of extracellular matrix in vivo. These results suggest that HA-HP hydrogel has the potential to prolong the paracrine activity of cells, thereby increasing their therapeutic effectiveness in wound healing. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1986-2000, 2017.
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina.|Department of Biomedical Engineering, Virginia Tech-Wake Forest University School of Biomedical Engineering and Sciences, Wake Forest Baptist Health, Medical Center Boulevard, Winston-Salem, North Carolina.|Department of Cancer Biology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina.
authors.forename: Aleksander
authors.initials: A
authors.lastname: Skardal
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina.
authors.forename: Sean V
authors.initials: SV
authors.lastname: Murphy
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Crowell
authors.affiliation: Department of Rehabilitation Medicine, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, Washington.|Department of Bioengineering, University of Washington, Seattle, Washington.
authors.forename: David
authors.initials: D
authors.lastname: Mack
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina.|Department of Biomedical Engineering, Virginia Tech-Wake Forest University School of Biomedical Engineering and Sciences, Wake Forest Baptist Health, Medical Center Boulevard, Winston-Salem, North Carolina.
authors.forename: Anthony
authors.initials: A
authors.lastname: Atala
authors.affiliation: Wake Forest Institute for Regenerative Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina.|Department of Biomedical Engineering, Virginia Tech-Wake Forest University School of Biomedical Engineering and Sciences, Wake Forest Baptist Health, Medical Center Boulevard, Winston-Salem, North Carolina.|Department of Cancer Biology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, North Carolina.
authors.forename: Shay
authors.initials: S
authors.lastname: Soker
mesh_terms: D000650:Amnion / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D018914:Cells, Immobilized / Q000378:metabolism* / Q000473:pathology / Q000637:transplantation*; D016207:Cytokines / Q000378:metabolism*; D006493:Heparin / Q000737:chemistry / Q000494:pharmacology; D064593:Heterografts; D006801:Humans; D006820:Hyaluronic Acid / Q000737:chemistry / Q000494:pharmacology; D020100:Hydrogels / Q000737:chemistry / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D033581:Stem Cell Transplantation; D013234:Stem Cells / Q000378:metabolism* / Q000473:pathology; D014947:Wounds and Injuries / Q000378:metabolism / Q000473:pathology / Q000628:therapy*
chemical_list: D016207:Cytokines; D020100:Hydrogels; D006820:Hyaluronic Acid; D006493:Heparin
keywords: amniotic fluid-derived stem cells; growth factor release; hyaluronic acid; photopolymerization; skin regeneration