title: Growth factors for sequential cellular de- and re-differentiation in tissue engineering.
abstract: A model system for the in vitro generation of cartilaginous constructs was used to study a tissue engineering paradigm whereby sequentially applied growth factors promoted chondrocytes to first de-differentiate into a proliferative state and then re-differentiate and undergo chondrogenesis. Early cultivation in medium with supplemental TGF-beta1/FGF-2 doubled cell fractions in 2-week constructs compared to unsupplemented controls. Subsequent culture with supplemental IGF-I yielded large 4-week constructs with high fractions of cartilaginous extracellular matrix (ECM) and high compressive moduli, whereas prolonged culture with supplemental FGF-2 yielded small 4-week constructs with low ECM fractions and moduli. Sequential supplementation with TGF-beta1/FGF-2 and then IGF-I yielded 4-week constructs with type-specific mRNA expression and protein levels that were high for type II and negligible for type I collagen, in contrast to other growth factor regimens studied. The data demonstrate that structural, functional, and molecular properties of engineered cartilage can be modulated by sequential application of growth factors.
authors.affiliation: Division of Health Sciences and Technology, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139-4307, USA.
authors.forename: M
authors.initials: M
authors.lastname: Pei
authors.forename: J
authors.initials: J
authors.lastname: Seidel
authors.forename: G
authors.initials: G
authors.lastname: Vunjak-Novakovic
authors.forename: L E
authors.initials: LE
authors.lastname: Freed
mesh_terms: D000818:Animals; D002356:Cartilage / Q000166:cytology* / Q000187:drug effects; D002417:Cattle; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects*; D003470:Culture Media; D005109:Extracellular Matrix / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000008:administration & dosage / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D013329:Structure-Activity Relationship; D023822:Tissue Engineering / Q000379:methods*; D016212:Transforming Growth Factor beta / Q000008:administration & dosage / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
chemical_list: D003470:Culture Media; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D016222:Fibroblast Growth Factor 2; D007334:Insulin-Like Growth Factor I