Histological and molecular biological analysis on the reaction of absorbable thread; Polydioxanone and polycaprolactone in rat model

Introduction One of the most frequently performed anti‐aging surgical procedures is thread facelift. Since the 2010s, thread lifts using absorbable polydioxanone (PDO) thread were developed and have become increasingly popular. This research aims to identify the changes in and the mechanisms of absorbable thread‐lifting components, namely, PDO (polydioxanone) and PCL (polycaprolactone), with varied absorption periods in the body. Methods Four different types of threads, namely, single‐stranded thread, 4‐stranded thread, 12‐stranded thread, and barbed Cog thread, were used for each component. Histological changes in the thread and neighboring tissue of rat model were investigated for 2‐week interval, and PCR was conducted for genes related to fibroblast proliferation including type 1α1 collagen, type 3α1 collagen, transforming growth factor beta 1 (TGF‐β1). Results An increase in the collagen formation in all types of PDO and PCL groups was observed during the first 12 weeks and decreased afterward. Collagen formation decreased later in the PCL thread group significantly than the POD group. PCL thread remained logner in the tissue for over a year regarding POD requiring around 24 weeks of absorption–degradation. A larger surface area between the thread and the tissue induces a greater response in the tissue, resulting in an increase in inflammatory cells, myofibroblasts, and fibroblasts. Results showed a similar pattern of increase in type 1α1 collagen and TGF‐β in the PDO thread group. This suggests that TGF‐β signal transduction leads to fibroblast proliferation that stimulates collagen formation and tissue re‐formation. In contrast, only type 3α1 collagen increased in the PCL thread group. Conclusion More collagen formation and tissue responses are induced by PCL thread, remaining longer in the tissue than PDO, leading to more tissue tightening effects that is one of the most important points of face lifting. Morphological comparison of threads shows that not only an increase in surface area between thread and tissue but also multi‐strand increase tissue response, which in turn increases tissue maintenance effects.