Cbl: complex formation and functional implications

Although the influence of tetracyclines on periodontal connective tissue cells has been the topic of many in vitro and in vivo studies, data regarding their effects on gingival epithelial cells are scarce. The present in vitro study was designed to examine the influence of minocycline, a semi-synthetic analog of tetracycline, on human gingival keratinocyte (HGK) attachment and migration. Attachment tests were performed with HGK prelabeled by tritiated amino-acids. Increasing concentrations of minocycline (10, 50, 100 micrograms/ml) in the medium produced no significant modification of cell adhesion kinetics compared to control conditions, except for 100 micrograms/ml which statistically significantly (p < 0.05) reduced the number of attached cells beyond 6 h. A 24-h cell preincubation in 10 micrograms/ml of minocycline did not alter the kinetics of HGK attachment. Scanning electron microscopic observations of attached HGK showed that the presence of 10 micrograms/ml of minocycline in the "attachment medium" induced the production of multiple filopodial extensions. Migration tests in Boyden chambers for 40 h demonstrated that HGK preincubation for 24 h in a 10 micrograms/ml minocycline-HCl solution increased significantly (p < 0.005) cell migration towards a gradient of fetal calf serum. The presence of 10 micrograms/ml of minocycline in contact with the keratinocytes in the upper compartment of the migration chambers also produced a significant (p < 0.005) result. In contrast, the presence of minocycline in the lower compartments did not produce any chemoattractive effect. Within the limits of their significance, these results suggest that, at concentrations not beyond 50 micrograms/ml, minocycline could fasten the periodontal wound coverage by epithelial cells and allow the normal reformation of a junctional epithelium.