A Novel Osteogenic Oxysterol Compound for Therapeutic Development to Promote Bone Growth: Activation of Hedgehog Signaling and Osteogenesis Through Smoothened Binding |
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| Authors: | Scott R Montgomery Taya Nargizyan Vicente Meliton Sigrid Nachtergaele Rajat Rohatgi Frank Stappenbeck Michael E Jung Jared S Johnson Bayan Aghdasi Haijun Tian Gil Weintraub Hirokazu Inoue Elisa Atti Sotirios Tetradis Renata C Pereira Akishige Hokugo Raed Alobaidaan Yanlin Tan Theodor J Hahn Jeffrey C Wang Farhad Parhami |
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| Affiliation: | 1. Department of Orthopedic Surgery, University of California, Los Angeles (UCLA), Los Angeles, CA, USA;2. Department of Medicine, David Geffen School of Medicine, UCLA, Los Angeles, CA, USA;3. Department of Biochemistry, Stanford University School of Medicine, Stanford, CA, USA;4. Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA;5. Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA, USA;6. School of Dentistry, UCLA, Los Angeles, CA, USA;7. Department of Pediatric Nephrology, UCLA, Los Angeles, CA, USA;8. Department of Plastic Surgery, UCLA, Los Angeles, CA, USA;9. Veterans' Administration (VA) Greater Los Angeles Healthcare System and Geriatric Research, Education, and Clinical Center, Los Angeles, CA, USA;10. Department of Orthopedic Surgery, University of Southern California (USC), Los Angeles, CA, USA |
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| Abstract: | Osteogenic factors are often used in orthopedics to promote bone growth, improve fracture healing, and induce spine fusion. Osteogenic oxysterols are naturally occurring molecules that were shown to induce osteogenic differentiation in vitro and promote spine fusion in vivo. The purpose of this study was to identify an osteogenic oxysterol more suitable for clinical development than those previously reported, and evaluate its ability to promote osteogenesis in vitro and spine fusion in rats in vivo. Among more than 100 oxysterol analogues synthesized, Oxy133 induced significant expression of osteogenic markers Runx2, osterix (OSX), alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin (OCN) in C3H10T1/2 mouse embryonic fibroblasts and in M2‐10B4 mouse marrow stromal cells. Oxy133‐induced activation of an 8X‐Gli luciferase reporter, its direct binding to Smoothened, and the inhibition of Oxy133‐induced osteogenic effects by the Hedgehog (Hh) pathway inhibitor, cyclopamine, demonstrated the role of Hh pathway in mediating osteogenic responses to Oxy133. Oxy133 did not stimulate osteogenesis via BMP or Wnt signaling. Oxy133 induced the expression of OSX, BSP, and OCN, and stimulated robust mineralization in primary human mesenchymal stem cells. In vivo, bilateral spine fusion occurred through endochondral ossification and was observed in animals treated with Oxy133 at the fusion site on X‐ray after 4 weeks and confirmed with manual assessment, micro‐CT (µCT), and histology after 8 weeks, with equal efficiency to recombinant human bone morphogenetic protein‐2 (rhBMP‐2). Unlike rhBMP‐2, Oxy133 did not induce adipogenesis in the fusion mass and resulted in denser bone evidenced by greater bone volume/tissue volume (BV/TV) ratio and smaller trabecular separation. Findings here suggest that Oxy133 has significant potential as an osteogenic molecule with greater ease of synthesis and improved time to fusion compared to previously studied oxysterols. Small molecule osteogenic oxysterols may serve as the next generation of bone anabolic agents for therapeutic development. © 2014 American Society for Bone and Mineral Research. |
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| Keywords: | OXYSTEROL SPINAL FUSION BMP2 OSTEOGENESIS ADIPOGENESIS |
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