Abstract
While recombinant human bone morphogenetic protein (rhBMP)-2-based bone therapy presents potential osteoinductivity, it also leads concern due to transient osteoclast activation during early healing periods, ultimately limiting its clinical use. Therefore, we investigated invivo and invitro rhBMP-2 signaling which mediates early bone resorbing effect, depending on the dose, and attempted to inhibit this resorption phenomenon using NFAT inhibitor as a target molecule. High-dose of rhBMP-2 (20μg/defect) enhanced osteoclast activation and the expression of bone resorption markers, compared to low dose (5μg/defect) at one week after surgery in collagen sponge-delivered rat calvarial defect models. Interestingly, this trend was also observed in the expression of bone formation markers. In particular, rhBMP-2 upregulated RANKL expression, while it downregulated osteoprotegerin (OPG) expression, resulting in a dose-dependent increase in the ratio of RANKL to OPG. NFAT inhibitor (150μ m) treatment invivo suppressed the high-dose effect of rhBMP-2 on both resorption and formation. Invitro results of rhBMP-2 signaling and NFAT inhibitor effects in rat mesenchymal stem cells showed similar trends as invivo results. Microcomputer tomography-based evaluation at 4 weeks showed that combined treatment of NFAT inhibitor with 20μg rhBMP-2 invivo increased bone volume (BV) more than 20μg rhBMP-2 alone, which showed little difference in BV compared to 5μg of rhBMP-2. These results demonstrated that rhBMP-2 implantation concurrently signalized into enhanced osteoclastogenesis and osteoblastogenesis invivo, dose-dependently. Ratio of RANKL/OPG might be an index for early bone resorbing activity of implanted rhBMP-2. A local cocktail treatment of NFAT inhibitor and high-dose rhBMP-2 might be an alternative to overcome early bone resorbing effects, thereby accelerating bone formation.
Original language | English |
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Pages (from-to) | 1869-1881 |
Number of pages | 13 |
Journal | Biomaterials |
Volume | 35 |
Issue number | 6 |
DOIs | |
State | Published - Feb 2014 |
Keywords
- Bone formation
- High-dose
- NFATc1
- Osteoclast activation
- RANKL
- RhBMP-2