MARKERS OF BONE AND CEMENTUM FORMATION ACCUMULATE IN TISSUES REGENERATED IN PERIODONTAL DEFECTS TREATED WITH EXPANDED POLYTETRAFLUOROETHYLENE MEMBRANES

Guided tissue regeneration (GTR) is a concept that evolved from the de velopment of membrane-barrier techniques, which allow the repopulation of periodontal wounds by specific cells, resulting in a new attachmen t apparatus, To help understand the biological mechanisms involved in membrane barrier-led periodontal healing, the present study investigat ed the macromolecules phenotypic of bone and cementum formation in tis sues grown under the GTR barrier by immunolocalization. Periodontal re generation was initiated by placing barriers on experimentally induced periodontal defects in a Rhesus monkey model, Samples were harvested 6 wk after healing and sections of soft tissues grown under GTR barrie rs (membrane tissue) were stained with antibodies to bone morphogeneti c proteins-2 and 4 (BMP-2, BMP-4), bone morphogenetic protein-ii (OP-1 ), cementum attachment protein (CAP), osteonectin (OTN) and bone sialo protein (BSP). Tissues grown in the absence of any barrier device serv ed as a control (control tissue), Membrane periodontal tissues from be neath the ePTFE membrane were comprised of spindle-shaped fibroblast-l ike cells encased in a dense fibrillar extracellular matrix (ECM). Rou nd-shaped cells aggregated to form nodules. Newly formed hard tissue w as conspicuous. A similar, but very disorganized, fiber network was ob served in control tissues, but neither nodule formation nor hard tissu e was observed. Osteonectin staining was observed in the ECM of membra ne tissues and particularly in the area of the connective tissue adjac ent to newly formed hard tissue. The dense network of connective tissu e fibers was also stained. In control tissues, cells and fiber network had a significantly weaker signal for osteonectin, An intense reactio n was observed in membrane tissues stained for BSP, particularly the c onnective tissue adjacent to the newly formed hard tissue, while the c ontrol tissues did not stain for BSP. Cementum attachment protein (CAP ) was observed in the connective tissue adjacent to the newly formed h ard tissue of the membrane tissues whereas control tissues exhibited n o CAP staining, In membrane tissues, BMP-2 and 4 distribution was foun d to concentrate in nodule areas, in the newly formed hard tissue and in the fiber network, while very faint staining was observed in contro l sections. The distribution of OP-l in membrane and control tissues w as found to mimic the BMP-2 pattern, but staining was more distributed in hard tissue matrix. When the profile of BMP-2, BMP-4, OF-1, OTN, C AP and BSP staining was analyzed on membrane tissue sections, striking similarities were noted in the connective tissue adjacent to the newl y formed hard tissue and in nodular areas. In addition, the localizati on of BMP-2 and BMP-4 mRNA was investigated in both tissues by in situ hybridization. An intense expression of BMP-2 and 4 transcripts was o bserved in membrane tissues while control tissues never yielded any po sitive hybridization signal. The correlation between these histochemic al findings strongly suggests that the forming soft tissues under ePTF E membranes contain cells and ECM macromolecules normally associated w ith bone and cementum.