title: Surface tethered epidermal growth factor protects proliferating and differentiating multipotential stromal cells from FasL-induced apoptosis.
abstract: Multipotential stromal cells or mesenchymal stem cells (MSCs) have been proposed as aids in regenerating bone and adipose tissues, as these cells form osteoblasts and adipocytes. A major obstacle to this use of MSC is the initial loss of cells postimplantation. This cell death in part is due to ubiquitous nonspecific inflammatory cytokines such as FasL generated in the implant site. Our group previously found that soluble epidermal growth factor (sEGF) promotes MSC expansion. Furthermore, tethering EGF (tEGF) onto a two-dimensional surface altered MSC responses, by restricting epidermal growth factor receptor (EGFR) to the cell surface, causing sustained activation of EGFR, and promoting survival from FasL-induced death. sEGF by causing internalization of EGFR does not support MSC survival. However, for tEGF to be useful in bone regeneration, it needs to allow for MSC differentiation into osteoblasts while also protecting emerging osteoblasts from apoptosis. tEGF did not block induced differentiation of MSCs into osteoblasts, or adipocytes, a common default MSC-differentiation pathway. MSC-derived preosteoblasts showed increased Fas levels and became more susceptible to FasL-induced death, which tEGF prevented. Differentiating adipocytes underwent a reduction in Fas expression and became resistant to FasL-induced death, with tEGF having no further survival effect. tEGF protected undifferentiated MSC from combined insults of FasL, serum deprivation, and physiologic hypoxia. Additionally, tEGF was dominant in the face of sEGF to protect MSC from FasL-induced death. Our results suggest that MSCs and differentiating osteoblasts need protective signals to survive in the inflammatory wound milieu and that tEGF can serve this function.
authors.affiliation: Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Melanie
authors.initials: M
authors.lastname: Rodrigues
authors.forename: Harry
authors.initials: H
authors.lastname: Blair
authors.forename: Linda
authors.initials: L
authors.lastname: Stockdale
authors.forename: Linda
authors.initials: L
authors.lastname: Griffith
authors.forename: Alan
authors.initials: A
authors.lastname: Wells
mesh_terms: D017667:Adipocytes / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D001672:Biocompatible Materials; D001854:Bone Marrow Cells / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D053222:Fas Ligand Protein / Q000378:metabolism*; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D010006:Osteoblasts / Q000378:metabolism
chemical_list: D001672:Biocompatible Materials; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D004815:Epidermal Growth Factor; C512478:EGFR protein, human; D066246:ErbB Receptors