title: Synergistic effects of growth and differentiation factor-5 (GDF-5) and insulin on expanded chondrocytes in a 3-D environment.
abstract: OBJECTIVE
  To investigate the effects of growth and differentiation factor-5 (GDF-5) alone or in combination with insulin on engineered cartilage from primary or expanded chondrocytes during 3-dimensional in vitro culture.
  
  
  METHODS
  Juvenile bovine chondrocytes were seeded either as primary or as expanded (passage 2) cells onto polyglycolic acid fiber meshes and cultured for 3 weeks in vitro. Additionally, adult human chondrocytes were grown in pellet culture after expansion (passage 2). The culture medium was supplemented either with GDF-5 in varying concentrations or insulin alone, or with combinations thereof.
  
  
  RESULTS
  For primary chondrocytes, the combination of GDF-5 and insulin led to increased proliferation and construct weight, as compared to either factor alone, however, the production of glycosaminoglycans (GAG) and collagen per cell were not affected. With expanded bovine chondrocytes, the use of GDF-5 or insulin alone led to only very small constructs with no type II collagen detectable. However, the combination of GDF-5 (0.01 or 0.1 microg/ml) and insulin (2.5 microg/ml) yielded cartilaginous constructs and, in contrast to the primary cells, the observed redifferentiating effects were elicited on the cellular level independent of proliferation (increased production of GAG and collagen per cell, clear shift in collagen subtype expression with type II collagen observed throughout the construct). The synergistic redifferentiating effects of the GDF-5/insulin combination were confirmed with expanded adult human cells, also exhibiting a clear shift in collagen subtype expression on the mRNA and protein level.
  
  
  CONCLUSIONS
  In combination with insulin, GDF-5 appears to enable the redifferentiation of expanded chondrocytes and the concurrent generation of cartilaginous constructs. The demonstration of these synergistic effects also for adult human chondrocytes supports the clinical relevance of the findings.
authors.affiliation: Department of Pharmaceutical Technology, University of Regensburg, 93040 Regensburg, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Appel
authors.forename: J
authors.initials: J
authors.lastname: Baumer
authors.forename: D
authors.initials: D
authors.lastname: Eyrich
authors.forename: H
authors.initials: H
authors.lastname: Sarhan
authors.forename: S
authors.initials: S
authors.lastname: Toso
authors.forename: C
authors.initials: C
authors.lastname: Englert
authors.forename: D
authors.initials: D
authors.lastname: Skodacek
authors.forename: S
authors.initials: S
authors.lastname: Ratzinger
authors.forename: S
authors.initials: S
authors.lastname: Grässel
authors.forename: A
authors.initials: A
authors.lastname: Goepferich
authors.forename: T
authors.initials: T
authors.lastname: Blunk
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism*; D024043:Collagen Type II / Q000235:genetics / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000378:metabolism*; D055428:Growth Differentiation Factor 5 / Q000096:biosynthesis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D023822:Tissue Engineering
chemical_list: D024043:Collagen Type II; D006025:Glycosaminoglycans; D055428:Growth Differentiation Factor 5