Relaxin Enhances Bone Regeneration with BMP-2-Loaded Hydroxyapatite Microspheres


Our aims were to 1) evaluate the capacity of hollow hydroxyapatite (HA) microspheres (212–250 μm) to serve as a delivery system for controlled release of BMP-2 in vitro and 2) examine relaxin as an enhancer of BMP-2 for bone regeneration. Hollow HA microspheres were converted from borate glass microspheres and characterized using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, and the Brunauer–Emmett–Teller method. The microspheres loaded with BMP-2 and relaxin were implanted for 6 weeks in Sprague Dawley rats with calvarial defects. BMP-2 alone in the range up to 1 μg per defect exhibited dose-dependent bone regeneration while relaxin alone in the range up to 0.25 μg per defect did not promote bone regeneration. When compared with BMP-2 alone (1 μg per defect), a 50% reduction in the BMP-2 dose was achieved with the addition of 0.05, 0.1, or 0.25 μg of relaxin per defect. These results show that loading HA microspheres with a combination of relaxin and BMP-2 can significantly reduce the BMP-2 dose required to regenerate an equivalent amount of bone.


Materials Science and Engineering

Second Department

Biological Sciences

Research Center/Lab(s)

Center for Research in Energy and Environment (CREE)


This project was funded by a grant from National Institute of Dental and Craniofacial Research (NIDCR) (grant # R15DE023987) and a seed grant from Missouri S&T Center for Biomedical Science and Engineering.

Keywords and Phrases

Bone Morphogenetic Protein-2bone Regeneration; Hydroxyapatite Microsphere; Protein Growth Factor; Rat Calvarial Defect Model; Relaxin

International Standard Serial Number (ISSN)

1549-3296; 1552-4965

Document Type

Article - Journal

Document Version


File Type





© 2020 John Wiley & Sons Inc., All rights reserved.

Publication Date

01 May 2020

PubMed ID