Small molecule stimulation enhances bone regeneration but not titanium implant osseointegration

The osteogenic and osseointegrative potential of a small molecule was examined to assess its usefulness in regenerative procedures. Purmorphamine was used to stimulate bone growth and repair in an in vitro cell-based assay and an in vivo chick embryo CAM-assay with and without the presence of an implant. Purmorphamine adhered to precipitated hydroxyapatite coating, could activate the sonic hedgehog pathway and thereby stimulated osteodifferentiation. Porous calcium phosphate beads were used to deliver this small molecule in vivo and showed that purmorphamine increased the trabecular bone to bone area significantly. The assay showed purmorphamine failed to induce any significant difference in osseointegration on titanium coated PTFE implants. This suggests that, while a small molecule can enhance osteogenesis and might be useful in regenerative procedures, it failed to enhance the osseointegration of a Ti coated implant, suggesting that this sort of stimulation might be useful for enhancing bone regeneration where bone loss due to disease exists, but not for enhancing early stability of an implant.

Hedgehog pathway agonism: therapeutic potential and small-molecule development

The Hedgehog (Hh) pathway is a developmental signaling pathway that plays multiple roles during embryonic development and in adult tissues. Constitutive Hh signaling has been linked to the development and progression of several forms of cancer, and the application of small-molecule pathway inhibitors as anticancer chemotherapeutics is well studied and clearly defined. Activation of the Hh pathway as a therapeutic strategy for a variety of degenerative or ischemic disorders has also been proposed; however, the development of small-molecule Hh agonists has received less attention. The goal of this review is to highlight the recent evidence supporting the therapeutic potential of Hh pathway activators and to provide a comprehensive overview of small-molecule pathway agonists.