Comparison of native xenogeneic and allogeneic bone morphogenetic proteins in the sheep skull defect assay model.
OBJECTIVE
The purpose of this study was to determine, if there is any difference in the osteoinductive response between xenogeneic and allogeneic bone morphogenetic protein (BMP) in the skull defect assay model.


METHODS
The skull samples of two experimental series were chosen for uniform radiomorphometric measurement. In the xenogeneic BMP group (X-group), 52 mg of native moose (Alces alces) BMP (mBMP) was implanted in six 22-mm sheep midline skull defects, and in the allogeneic BMP (A-group), 8 mg of native sheep BMP (sBMP) was used in six same size parietal skull defects. The formation of new bone was confirmed histologically and the quantity of it was measured radiomorphometrically at 16 weeks after implantation from the standardized radiographs using a common flatbed scanner and image processing software, the mean grey scale intensity (radiopacity) multiplied by the original defect area giving the new bone volume. This was divided by the milligram amount of implanted BMP to get the value for comparison of BMP activities.


RESULTS
The control defects in both groups, implanted with 13 mg of type IV collagen, showed that the defects did not heal spontaneously during the follow-up time. In the X-group, the healing percentage was 92.4 +/- 3.0%, the calculated average bone volume (ABV)/mg being 12.4 +/- 0.5 units, whereas in the A-group the healing percentage was 62.9 +/- 8.5% and ABV/mg 60.9 +/- 6.7. Hence the activity per milligram proved to be more than four-fold with allogeneic compared to xenogeneic BMP. However, when the difference in spontaneous healing of the defects in the two series was taken into consideration, only slight but not significant difference (P = 0.077) of activity could be demonstrated between xenogeneic (5.7 +/- 1.7) and allogeneic BMP (9.05 +/- 3.7).


CONCLUSIONS
The result is in concordance with the previous published results showing that no significant immune inhibition is seen after a single implantation of xenogeneic BMP in an orthotopic site.
Viljanen
V V
VV
Institute of Medical Technology, University of Tampere, Finland. Veikko.Viljanen@viljane.pp.fi
Lindholm
T S
TS
D000818:Animals; D019485:Bone Morphogenetic Proteins / Q000276:immunology / Q000627:therapeutic use*; D001861:Bone Regeneration; D016723:Bone Remodeling; D003670:Deer; D004195:Disease Models, Animal; D007091:Image Processing, Computer-Assisted; D020007:Implants, Experimental; D012756:Sheep; D012886:Skull / Q000473:pathology*; D014183:Transplantation, Heterologous; D014184:Transplantation, Homologous
D019485:Bone Morphogenetic Proteins