Method: Titanium discs with a large grit sandblasted and acid-etched microrough (SLA) or hydrophilic-modified SLA (modSLA) surface were used to cover critical-sized calvarial defects in female Sprague-Dawley rats. Samples of the exudate within the calvarial defect and beneath the titanium discs were collected for inflammatory cytokine (IL-1a, IL-1b, MCP-1, IL-10, IL-12p40, MIP-2, RANTES and TNFa) analysis 1, 4 and 7 days post-surgery. The phenotype of macrophages adherent to the titanium surfaces were determined by CD11c (M1) and CD163 (M2) immuno-fluorescent staining. Samples of the healing defect were also prepared for histological analysis.
Result: After one day of healing, high levels of all the inflammatory cytokines were observed. These levels fell by day 4, apart from MCP-1 which decreased only on the modSLA surface. The level of TNFa decreased on both surfaces, however the extent of the decrease was significantly (p <0.05) more so on the modSLA surface. At day 7 of healing, the level of MCP-1 on the modSLA surface decreased further while the levels of this cytokine on the SLA surface were maintained at the levels seen at day 1 and 4. The levels of TNFa at day 7 on both surfaces were maintained at that seen at day 4. Compared to modSLA, more CD11c+ve (M1) macrophages were also seen on the SLA surface at days 4 and 7. These results correlate with increased new bone formation on the modSLA surface by day 7.
Conclusion: This study demonstrates that the modSLA titanium surface modulates the adherent macrophage phenotype, the secretion of the pro-inflammatory cytokines TNFa and MCP-1 and bone formation in the early stages of osseous wound healing.