title: HhAntag, a Hedgehog Signaling Antagonist, Suppresses Chondrogenesis and Modulates Canonical and Non-Canonical BMP Signaling.
abstract: Chondrogenesis subtends the development of most skeletal elements and involves mesenchymal cell condensations differentiating into growth plate chondrocytes that proliferate, undergo hypertrophy, and are replaced by bone. In the pediatric disorder Hereditary Multiple Exostoses, however, chondrogenesis occurs also at ectopic sites and causes formation of benign cartilaginous tumors--exostoses--near the growth plates. No treatment is currently available to prevent or reverse exostosis formation. Here, we asked whether chondrogenesis could be stopped by targeting the hedgehog pathway, one of its major regulators. Micromass cultures of limb mesenchymal cells were treated with increasing amounts of the hedgehog inhibitor HhAntag or vehicle. The drug effectively blocked chondrogenesis and did so in a dose-dependent manner as monitored by: alcian blue-positive cartilage nodule formation; gene expression of cartilage marker genes; and reporter activity in Gli1-LacZ cell cultures. HhAntag blocked chondrogenesis even when the cultures were co-treated with bone morphogenetic protein 2 (rhBMP-2), a strong pro-chondrogenic factor. Immunoblots showed that HhAntag action included modulation of canonical (pSmad1/5/8) and non-canonical (pp38) BMP signaling. In cultures co-treated with HhAntag plus rhBMP-2, there was a surprising strong up-regulation of pp38 levels. Implantation of rhBMP-2-coated beads near metacarpal elements in cultured forelimb explants induced formation of ectopic cartilage that however, was counteracted by HhAntag co-treatment. Collectively, our data indicate that HhAntag inhibits not only hedgehog signaling, but also modulates canonical and non-canonical BMP signaling and blocks basal and rhBMP2-stimulated chondrogenesis, thus representing a potentially powerful drug-based strategy to counter ectopic cartilage growth or induce its involution.
authors.affiliation: Translational Research Program in Pediatric Orthopaedics, Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Christina
authors.initials: C
authors.lastname: Mundy
authors.affiliation: Bucknell University, Lewisburg, Pennsylvania.
authors.forename: Adebayo
authors.initials: A
authors.lastname: Bello
authors.affiliation: Translational Research Program in Pediatric Orthopaedics, Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Federica
authors.initials: F
authors.lastname: Sgariglia
authors.affiliation: Translational Research Program in Pediatric Orthopaedics, Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Eiki
authors.initials: E
authors.lastname: Koyama
authors.affiliation: Translational Research Program in Pediatric Orthopaedics, Division of Orthopaedic Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Pacifici
mesh_terms: D000813:Anilides / Q000494:pharmacology*; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism*; D002356:Cartilage / Q000187:drug effects / Q000254:growth & development; D020219:Chondrogenesis / Q000187:drug effects* / Q000235:genetics; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D005552:Forelimb / Q000378:metabolism; D053823:Hedgehog Proteins / Q000037:antagonists & inhibitors*; D008024:Ligands; D008297:Male; D051379:Mice; D011725:Pyridines / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000378:metabolism*
chemical_list: D000813:Anilides; D015415:Biomarkers; D055396:Bone Morphogenetic Protein 2; D053823:Hedgehog Proteins; C538724:HhAntag691; D008024:Ligands; D011725:Pyridines; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2