A novel implantable device, the analytic bone implant, was used in order
to establish a model for studies of bone-healing and the evaluation of
factors that augment the process, such as transforming growth-factor beta
(TGF-beta). This device was implanted into the tibiae of four baboons.
After healing, bone was removed from the center chamber. Recombinant human
TGF beta-1 was then delivered to the core of the device. After twenty-two
days of healing, the device was disassembled and the newly formed bone was
removed from the core of the implant for histomorphometric analysis. An
analysis of the bone revealed a substantial effect of TGF-beta on
osteoblastic activity and proliferation compared with that seen in control
and placebo groups. However, despite increased osteoblastic activity,
trabecular bone volumes at twenty-two days were equivalent among the
groups. The number of osteoclasts and the erosion of the surface were also
increased, although not significantly so. Substantial endochondral
formation of bone was seen in the supraperiosteal tissues directly over the
implants that contained TGF-beta but not over the implants in the control
and placebo groups. These data demonstrate the utility of this bone-implant
model for studies of bone-healing with minimally invasive methods. In
addition, use of the device provided the first in vivo data on the effects
of TGF-beta at an intermediate (twenty-two-day) time-point in the healing
process in a non-human primate.