Inhibitory effect of bovine milk osteopontin on the initial attachment of Streptococcus mutans

Abstract

We investigated the effect of bovine milk osteopontin (OPN) on the initial adhesion of Streptococcus mutans to hydroxyapatite. Hydroxyapatite pellets were immersed in a 5.4 µM OPN solution at 37°C for 30 min. As a control, Milli-Q water was used. Streptococcus mutans were incubated at 37°C for 2 h on the pellets. Crystal violet staining and the quantitation of DNA were evaluated. Violet staining was observed on the hydroxyapatite pellets in the control group, but faint staining was seen in the OPN group. The amount of DNA attached to the hydroxyapatite pellet was significantly lower in the OPN group. These results suggest that initial adhesion of S. mutans to the hydroxyapatite is inhibited with OPN.

Summary: We investigated the effect of bovine milk osteopontin (OPN) on the initial adhesion of Streptococcus mutans to hydroxyapatite. Hydroxyapatite pellets were immersed in 5.4 μM OPN solution at 37°C for 30 minutes. As a control, Milli-Q water was used. Streptococcus mutans were incubated at 37°C for 2 hours on the pellets. Results of crystal violet staining and the quantitation of DNA showed a lower quantity of S. mutans on the hydroxyapatite pellets in the OPN group (P < 0.05), suggesting that initial adhesion of S. mutans to the hydroxyapatite is inhibited with OPN.

Figure 1

Schematic diagram showing the flow of the study procedures.

Figure 2

Representative figures of crystal violet staining (a) OPN (−) GS5 group, (b) OPN (−) UA159 group, (c) OPN (+) GS5 group, (d) OPN (+) UA159 group. Both GS5 and UA159 strains showed staining over the entire surface of the samples in the OPN (−) groups (panels a and b). Concerning the OPN (+) groups, the GS5 OPN (+) group showed light purple staining in part of the sample margins but not in the center of the sample (panel c). In the UA159 OPN (+) group, the entire surface of the sample was unstained with crystal violet solution (panel d).

Figure 3

Relative amounts of Streptococcus mutans DNA attached to hydroxyapatite pellets. (a) GS5 strain, (b) UA159 strain. Data are presented as means ± SD. The amount of DNA in the OPN (+) group and SD when the amount of DNA in the OPN (−) group is set at 1. When the amount of DNA in the OPN (−) group was set at 1, that in the OPN (+) group was 0.44 ± 0.09 (a) for the GS5 strain and 0.21 ± 0.06 for the UA159 strain (b). There was a significant difference between the OPN (−) and OPN (+) groups for both strains. *P < 0.05.