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.