Tissue reactions to cog structure and pure gold in lifting threads: a histological study in rats.

BACKGROUND Thread lifting has become popular as a minimally-invasive suspension procedure, but there is little basic and clinical evidence in the literature on the long-term effects. OBJECTIVES The authors investigate the effects of two types of lifting threads in a rat model over the course of seven months. METHODS The dorsal skin of 18 Wistar rats was implanted with a 20-mm fragment of one of three types of thread: nonabsorbable monofilament cog, pure gold (24 karat) with no cog, and pure gold-coated cog. Six rats were in each group. Tissue samples were harvested and histologically evaluated at one, three, and seven months. RESULTS Histological assessment indicated (1) acute tissue reactions to the regular cog thread involving myofibroblasts and (2) delayed tissue reactions to the pure gold thread involving giant cells. The gold-coated cog thread showed a combination of the histological reactions associated with the cog thread and the pure gold thread, including faint early reactions, strong delayed reactions, and long-lasting capsule formation. Notably, the gold coating gradually came loose from the thread surface, suggesting that the release of tiny gold particles may promote longer-lasting tissue reactions. CONCLUSIONS The combination of cog structure and pure gold coating was evaluated for the first time in this study and results suggest that the gold-coated cog thread has clinical potential.