title: The effect of two point mutations in GDF-5 on ectopic bone formation in a beta-tricalciumphosphate scaffold.
abstract: The osteoinductivity of human growth-and-differentiation factor-5 (GDF-5) is well established, but a reduced amount of ectopic bone is formed compared to other members of the bone morphogenetic protein (BMP) family like BMP-2. We hypothesized that swap of two BMP-receptor-interacting residues of GDF-5 to amino acids present in BMP-2 (methionine to valine at the sites 453 and 456) may improve the bone formation capacity of the mutant GDF-5. Heterotopic bone formation of a mutant GDF-5 coated beta-TCP carrier was compared to carriers coated with similar amounts (10 microg) of GDF-5 and BMP-2 in SCID mice. Four week explants revealed 6-fold higher ALP activity in the mutant GDF-5 versus the wild type GDF-5 group (p < 0.0001) and 1.4-fold higher levels compared to BMP-2 (p < 0.006). Bone area in histology was significantly higher in mutant GDF-5 versus all other groups at 4 weeks; however, at 8 weeks BMP-2 reached a similar neo-bone formation like mutant GDF-5. Micro-CT evaluation confirmed higher values in the mutant GDF-5 and BMP-2 groups compared to wild type GDF-5. In conclusion, the mutant GDF-5 showed superior bone formation capacity than GDF-5, and a faster induction at similar final outcome as BMP-2. Mutant GDF-5 thus represents a promising new GDF-5 variant for bone regeneration possibly acting via an increased binding affinity to the BMP-type I receptor.
authors.affiliation: Research Center for Experimental Orthopaedics, Orthopaedic University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: Philip
authors.initials: P
authors.lastname: Kasten
authors.forename: Ingo
authors.initials: I
authors.lastname: Beyen
authors.forename: Dirk
authors.initials: D
authors.lastname: Bormann
authors.forename: Reto
authors.initials: R
authors.lastname: Luginbühl
authors.forename: Frank
authors.initials: F
authors.lastname: Plöger
authors.forename: Wiltrud
authors.initials: W
authors.lastname: Richter
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D002130:Calcium Phosphates / Q000737:chemistry*; D002828:Choristoma / Q000473:pathology*; D004789:Enzyme Activation / Q000187:drug effects; D055428:Growth Differentiation Factor 5 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D010012:Osteogenesis / Q000187:drug effects*; D017354:Point Mutation / Q000235:genetics*; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D054457:Tissue Scaffolds / Q000737:chemistry*; D055114:X-Ray Microtomography
chemical_list: D002130:Calcium Phosphates; C525893:GDF5 protein, human; D055428:Growth Differentiation Factor 5; D011994:Recombinant Proteins; C485817:beta-tricalcium phosphate; D000469:Alkaline Phosphatase