Outer membrane vesicles from Porphyromonas gingivalis affect the growth and function of cultured human gingival fibroblasts and umbilical vein endothelial cells.

Background: The purpose of this study was to examine the effects of outer membrane vesicles (OMV) obtained from Porphyromonas gingivalis (Pg) on the growth and function of human gingival fibroblasts (HGF) and human umbilical vein endothelial cells (HUVEC).

Methods: OMV were obtained from a cell-free growth medium of Pg ATCC 33277 by 40% NH2SO4 precipitation and ultracentrifugation. Cell proliferation was measured by 3H-thymidine incorporation into growing HGF and HUVEC. Endothelial cell function was determined by their capacity to form a network of capillary tubes on an extracellular matrix (ECM).

Results: Proliferating HGF and HUVEC demonstrated a significant dose-dependent inhibition of 3H-thymidine uptake when cultured with 0 to 40 microg/ml of OMV protein. HGF and HUVEC showed an IC50 of growth of about 9.0 microg/ml and 4.5 microg/ml of OMV protein, respectively. Capillary tube formation by HUVEC cultured on an ECM was suppressed by 70% to 80% with 5 microg/ml OMV protein after 18 hours of incubation. The presence of proteolytic enzymes in the OMV did not contribute to capillary tube disruption, since blocking enzyme activity with specific inhibitors did not reduce the suppression of capillary tube formation. After heating at 90 degrees C for 5 minutes, OMV significantly lost their capacity to suppress capillary tube formation.

Conclusions: OMV significantly inhibit the proliferation of cultured HGF and HUVEC in a dose-dependent manner. OMV suppressed the capillary tube formation by cultured HUVEC. The factor(s) appeared to be a protein and not endotoxin because its inhibitory activity was markedly reduced by heat inactivation. These studies suggest that OMV contribute to chronic periodontitis by suppressing cell proliferation and revascularization in periodontal tissues.