This study was performed to investigate the activity of partially purified bone morphogenetic protein (BMP) in ectopic bone induction and the characteristics of bone inductive cascades. The BMP was purified from bovine tibia through 3 steps of
chromatography; Hydroxyapatite column, Heparin-Sepha-rose column, and Sephacryl S-300 gel filtration column. The partially purified bovine BMP absorbed in the fibrous glass membrane(FGM) measuring 1.0(0.5cm was implanted into the dorsal
subcutaneous
pouches of rats, and the FGM alone was implanted as a control. The implants were harvested at 1, 2 and 3 weeks after implantation, then prepared for routine LM and EM examination.
1. The implanted 0.3mg of partially purified bovine BMP carried by FGM revealed high activity of ectopic bone formation without specific inflammation and immunologic reactions within 3 weeks.
2. The implants were separated form the host by fibrotic encapsulation with mild foreign body reactions. Within the capsule, the undifferentiated mesenchymal cells were chemotatically migrated toward the central area with gradual chondroblastic
differentiation.
3. With time, the endochondral bone formation was evident. The massive cartilage within the glass fiber mashwork was resistant to resorption but gradually eroded from the surface and was infiltrated by vasculature and marrow elements with an
appositional growth of bone trabeculae.
4. However there was no exophic growth of bone trabecular. The bone formation was defind within the fibrotic capsule The outer mature lamellar bone trabeculae were untied to form a shell of an ossicle containing bone marrow elements.
5. The implants without BMP showed only fibrosis with marked infiltration of foreign body giant cells.
These findings indicate that the BMP activity may be activated without associated bone matrix, and the BMP induced bone permited a limited growth according to the carrier's character and its shape. Thus, it is suggested that appropriate selection
of
carrier and its shaping is more important than the degree of BMP activity in inductive bone formation.
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