Foreign body response induced by tissue expander implantation.

The foreign body response (FBR) is described as the host's response to implanted biomaterials, which involves a complex cascade of immune modulators. The dynamic changes of immune cells, inflammatory cytokines and the formation of a fibrous capsule remain to be elucidated. In the present study, a model of subcutaneous implantation of a tissue expander was used. The results revealed that macrophages, the main immune cells in FBR, infiltrated into the expanded tissue and located at the tissue‑material interface from day 1‑90. Following the decrease of the number of macrophages, collagen deposited and fibroblasts transformed into myofibroblasts at the tissue‑material interface, leading to the formation of a fibrous capsule from day 14. The persistent existing macrophages led to a high expression of proinflammatory cytokines, including tumor necrosis factor‑α and interleukin‑1β, both of which initiated the NK-κB and JNK inflammatory pathways, mediating the FBR to tissue expander implantation.