Sclerostin small molecule inhibitors promote osteogenesis by activating canonical Wnt and BMP pathways
- Emory University, United States
- Panjab University, India
- Atlanta VA Medical Center, United States
Abstract
Background: The clinical healing environment after a posterior spinal arthrodesis surgery is one of the most clinically challenging bone healing environments across all orthopaedic interventions due to the absence of a contained space and the need to form de novo bone. Our group has previously reported that sclerostin in expressed locally at high levels throughout a developing spinal fusion. However, the role of sclerostin in controlling bone fusion remains to be established.
Methods: We computationally identified two FDA-approved drugs, as well as a single novel small molecule drug, for their ability to disrupt the interaction between sclerostin and its receptor, LRP5/6. The drugs were tested in several in vitro biochemical assays using murine MC3T3 and MSCs, assessing their ability to: (1) enhance canonical Wnt signaling, (2) promote the accumulation of the active (non-phosphorylated) form of b-catenin, and (3) enhance the intensity and signaling duration of BMP signaling. These drugs were then tested subcutaneously in rats as standalone osteoinductive agents on plain collagen sponges. Finally, the top drug candidates (called VA1 and C07) were tested in a rabbit posterolateral spine fusion model for their ability to achieve a successful fusion at 6 weeks.
Results: We show that by controlling GSK3b phosphorylation, our three SMIs simultaneously enhance canonical Wnt signaling and potentiate canonical BMP signaling intensity and duration. We also demonstrate that the SMIs produce dose-dependent ectopic mineralization in vivo in rats as well as significantly increase posterolateral spine fusion rates in rabbits in vivo, both as standalone osteogenic drugs and in combination with autologous iliac crest bone graft.
Conclusions: Few if any osteogenic small molecules possess the osteoinductive potency of BMP itself – that is, the ability to form de novo ectopic bone as a standalone agent. Herein, we describe two such SMIs that have this unique ability and were shown to induce de novo bone in a stringent in vivo environment. These SMIs may have the potential to be used in novel, cost-effective bone graft substitutes for either achieving spinal fusion or in the healing of critical-sized fracture defects.
Funding: This work was supported by a Veteran Affairs Career Development Award (IK2-BX003845).
Data availability
All data generated or analysed during this study are included in the manuscript and supporting file.
Article and author information
Author details
Steven M Presciutti
Funding
U.S. Department of Veterans Affairs (IK2-BX003845)
- Lorenzo M Fernandes
U.S. Department of Veterans Affairs (I01BX001516)
- George R Beck
U.S. Department of Veterans Affairs (I01 BX004708)
- Hicham Drissi
U.S. Department of Veterans Affairs (I01 BX004878)
- Hicham Drissi
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All rat and rabbit surgeries and procedures were first approved (#VOOS-14 - 2016-020211) by the Atlanta VA Medical Center Institutional Animal Care and Use Committee (IACUC).
Copyright
This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
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Sclerostin small molecule inhibitors promote osteogenesis by activating canonical Wnt and BMP pathways
eLife 12:e63402.
https://doi.org/10.7554/eLife.63402
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