Synergistic effects of growth and differentiation factor-5 (GDF-5) and insulin on expanded chondrocytes in a 3-D environment.

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. DESIGN: 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.

[Fibrin gel for treatment of tympanic membrane perforations: an experimental animal model]. / Behandlung von Trommelfellperforationen mit Fibringel: Eine tierexperimentelle Studie.

BACKGROUND: The goal of this study was to evaluate the effects of a fibrin gel on the healing of tympanic membrane perforation in rats. METHODS: Prolonged tympanic membrane perforations in 12 rats were created by application of mitomycin C to the intact tympanic membranes followed by bilateral myringotomy. Repeated applications of a fibrin gel to the perforation site of one tympanic membrane were performed in each animal. Tympanic membranes were observed for a total of 8 weeks. RESULTS: One perforation in each group was already patent at the end of the observation period. The mean healing period of the remaining tympanic membranes was found to be 16.7 days in the fibrin gel group and 19.6 days in the control group. CONCLUSION: A fibrin sheet does not seem to promote the wound healing process of tympanic membranes. However, the sheet might serve as a drug-delivery system for growth factors in the treatment of tympanic membrane perforations, because of its biocompatibility.