Improved union and bone strength in a mouse model of NF1 pseudarthrosis treated with recombinant human bone morphogenetic protein-2 and zoledronic acid.

Abstract

Tibial pseudarthrosis associated with Neurofibromatosis type 1 (NF1) is an orthopedic condition with consistently poor clinical outcomes. Using a murine model that features localized double inactivation of the Nf1 gene in an experimental tibial fracture, we tested the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) and/or the bisphosphonate zoledronic acid (ZA). Tibiae were harvested at 3 weeks for analysis, at which time there was negligible healing in un-treated control fractures (7% union). In contrast, rhBMP-2 and rhBMP-2/ZA groups showed significantly greater union (87% and 93%, p < 0.01 for both). Treatment with rhBMP-2 led to a 12-fold increase in callus bone volume and this was further increased in the rhBMP-2/ZA group. Mechanical testing of the healed rhBMP-2 and rhBMP-2/ZA fractures showed that the latter group had significantly higher mechanical strength and was restored to that of the un-fractured contralateral leg. Co-treatment with rhBMP-2/ZA also reduced fibrous tissue infiltration at the fracture site compared to rhBMP alone (p = 0.068). These data support the future clinical investigation of this combination of anabolic and anti-resorptive agents for the treatment of NF1 pseudarthrosis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:930-936, 2018.