Bone morphogenetic protein-2 enhances bone formation when delivered by a synthetic matrix containing hydroxyapatite/tricalciumphosphate.
OBJECTIVE
The aim of the present study was to test whether or not a synthetic matrix consisting of a polyethylene glycol (PEG) hydrogel containing recombinant human bone morphogenetic protein-2 (rhBMP-2) combined with grafting materials enhances bone regeneration compared with grafting alone or empty control sites.


METHODS
In each of 10 rabbits, four titanium cylinders were screwed in perforated slits made in the external cortical bones of the calvaria. The following four treatment modalities were randomly allocated: (1) empty control, (2) a combination of a PEG matrix and hydroxyapatite/tricalciumphosphate (HA/TCP) granules and a combination of a PEG matrix containing either 10 microg/ml (3) or 30 microg/ml (4) of BMP-2 and HA/TCP granules. After 8 weeks, the animals were sacrificed and ground sections were obtained for histological analysis. For statistical analysis repeated measures ANOVA and subsequent pairwise Student's t-test were applied (P<0.01).


RESULTS
Histomorphometric analysis showed an average area fraction of newly formed bone of 13.96+/-5.98% for the empty control, 15.16+/-7.95% for the PEG and HA/TCP group, 26.32+/-8.56% for the group containing 10 mug rhBMP-2/ml, and 30.15+/-7.63% for the group containing 30 microg rhBMP-2/ml. Statistical analysis revealed significantly more newly formed bone in the two rhBMP-2 groups compared with the PEG and HA/TCP group and with the empty control. Regarding the surface fraction of the HA/TCP graft particles covered with newly formed bone the addition of rhBMP-2 revealed a more than two-fold increase compared with cylinders containing HA/TCP granules without rhBMP-2. This difference reached statistical significance.


CONCLUSIONS
It is concluded that rhBMP-2 significantly enhances bone regeneration in rabbits when delivered by a synthetic matrix containing HA/TCP. This synthetic PEG matrix containing HA/TCP granules apparently fulfills a number of criteria required for an ideal carrier system for rhBMP-2.
Jung
Ronald E
RE
Department of Fixed and Removable Prothodontics and Dental Material Science, Dental School, University of Zurich, Zurich, Switzerland. jung@zzmk.unizh.ch
Weber
Franz E
FE
Thoma
Daniel S
DS
Ehrbar
Martin
M
Cochran
David L
DL
Hämmerle
Christoph H F
CH
D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000627:therapeutic use*; D001861:Bone Regeneration / Q000187:drug effects*; D018786:Bone Substitutes / Q000627:therapeutic use*; D016025:Bone Transplantation / Q000379:methods*; D002130:Calcium Phosphates / Q000627:therapeutic use; D004337:Drug Carriers / Q000627:therapeutic use; D017886:Durapatite / Q000627:therapeutic use; D006801:Humans; D011092:Polyethylene Glycols / Q000627:therapeutic use; D011817:Rabbits; D012886:Skull / Q000601:surgery; D016212:Transforming Growth Factor beta / Q000627:therapeutic use*
C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D018786:Bone Substitutes; D002130:Calcium Phosphates; D004337:Drug Carriers; D016212:Transforming Growth Factor beta; D011092:Polyethylene Glycols; D017886:Durapatite; C018392:tricalcium phosphate