title: Effect of temporally patterned TNF-α delivery on in vitro osteogenic differentiation of mesenchymal stem cells cultured on biodegradable polymer scaffolds.
abstract: Recent insight into the critical role of pro-inflammatory cytokines, particularly tumor necrosis factor-α (TNF-α), in bone regeneration has heralded a new direction in the design of tissue engineering constructs. Previous studies have demonstrated that continuous delivery of 50 ng/ml TNF-α to mesenchymal stem cells (MSCs) cultured on three-dimensional (3D) biodegradable electrospun poly(ϵ-caprolactone) (PCL) microfiber meshes stimulates mineralized matrix deposition, a marker of osteogenic differentiation. Since TNF-α exhibits a biphasic pattern of expression following bone fracture in vivo, this study aimed to investigate the effects of temporal patterns of TNF-α delivery on in vitro osteogenic differentiation of MSCs cultured on 3D electrospun PCL scaffolds. MSCs were cultured for 16 days and exposed to continuous, early, intermediate, or late TNF-α delivery. To further elucidate the effects of TNF-α on osteogenic differentiation, the study design included MSCs precultured both in the presence and absence of typically required osteogenic supplement dexamethasone. Mineralized matrix deposition was not observed in constructs with dexamethasone-naïve MSCs, suggesting that TNF-α is not sufficient to trigger in vitro osteogenic differentiation of MSCs. For MSCs precultured with dexamethasone, TNF-α suppressed alkaline phosphatase activity, an early marker of osteogenic differentiation, and stimulated mineralized matrix deposition, a late stage marker of MSC osteogenic differentiation. By elucidating the impact of temporal variations in TNF-α delivery on MSC osteogenic differentiation, our results offer insight into the regenerative mechanism of TNF-α and provide the design parameters for a novel tissue engineering strategy that rationally controls TNF-α signaling to stimulate bone regeneration.
authors.affiliation: a Department of Bioengineering , Rice University , P.O. Box 1892, MS 142 , Houston , TX , 77251-1892 , USA.
authors.forename: Paschalia M
authors.initials: PM
authors.lastname: Mountziaris
authors.forename: E
authors.initials: E
authors.lastname: Dennis Lehman
authors.forename: Ioannis
authors.initials: I
authors.lastname: Mountziaris
authors.forename: David C
authors.initials: DC
authors.lastname: Sing
authors.forename: F Kurtis
authors.initials: FK
authors.lastname: Kasper
authors.forename: Antonios G
authors.initials: AG
authors.lastname: Mikos
mesh_terms: D000818:Animals; D001861:Bone Regeneration / Q000187:drug effects / Q000276:immunology; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D006651:Histocytochemistry; D008297:Male; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects*; D008855:Microscopy, Electron, Scanning; D010012:Osteogenesis / Q000187:drug effects* / Q000276:immunology; D011091:Polyesters / Q000737:chemistry*; D051381:Rats; D011916:Rats, Inbred F344; D023822:Tissue Engineering / Q000379:methods; D054457:Tissue Scaffolds / Q000737:chemistry*; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage* / Q000276:immunology
chemical_list: D011091:Polyesters; D014409:Tumor Necrosis Factor-alpha; C016240:polycaprolactone