INDUCTION OF CEMENTOGENESIS BY RECOMBINANT HUMAN OSTEOGENIC PROTEIN-1(HOP-1 BMP-7) IN THE BABOON (PAPIO-URSINUS)/

Recombinant human osteogenic protein-1 (hOP-1), a member of the bone m orphogenetic protein family, was examined for its efficacy in periodon tal regeneration. Twelve furcation defects, surgically prepared in the first and second mandibular molars, were treated with bovine insolubl e collagenous matrix in conjunction with 0.0 (control), 100 and 500 mu g of recombinant hOP-1 per g of matrix. After 60 days of healing, his tological and histometric analyses on serial, undemineralized sections cut at 7 mu m showed substantial cementogenesis on the exposed dentin e of furcations treated with both doses of hOP-1 (p < 0.01 vs control) . Foci of nascent mineralization were seen within the newly deposited cementoid along the coronal areas of hOP-1-treated defects. Within the furcations, there were substantial amounts of residual collagenous ca rrier, interspersed with a mineralized matrix having histological feat ures of cementum. This mineralized cementum-like material was predomin antly deposited around the carrier, and blended into newly formed ceme ntum along the root surfaces. In the apical area, the cementum-like ma terial and the remaining alveolar bony housing were not connected; ind eed the two components were separated by a fibrovascular tissue that h ad numerous features of the periodontal ligament space. Formation and insertion of Sharpey's fibres into newly formed root cementum were als o observed. It is likely that the expression of specific cell phenotyp es by hOP-1 is regulated, in part, by the extracellular matrix microen vironment, including dentine. Thus, exposed dentine, in the presence o f exogenous hOP-1 at the doses tested, may preferentially modulate the expression of the cementogenic phenotype. These findings in a non-hum an primate show that hOP-1, at the doses tested, induced cementogenesi s on surgically denuded root surfaces, indicating a specific function during repair and regeneration of periodontal tissues.