Cathelicidin LL-37 Expression in Human Breast Implant Capsules

Abstract

Capsular contracture is the most common complication following breast implant placement. 1 Although not fully explained, the underlying pathogenic process was found to be multifactorial, involving several microbiological, inflammatory, and hormonal factors, 2-4 and receptors, such as Toll-like receptors (TLRs). 5,6 Myofibroblasts were addressed among the main players involved in the onset of this complication. 7,8 Furthermore, both clinical and subclinical infections were associated with increased incidence of contracture. 9,10 Cathelicidin LL-37 is a cationic peptide involved in innate immunity. It was proved to have broad-spectrum antimicrobial activity, to promote tissue healing, and to exert immunomodulatory Background: Capsular contracture is the most common complication following breast implant placement. Cathelicidin LL-37 is a cationic peptide involved in innate immunity. Initially investigated for its antimicrobial role, it was found to have pleiotropic activities, such as immunomodulation, angiogenesis stimulation, and tissue healing. The aim of the study was to investigate the expression and localization of LL-37 in human breast implant capsules and its relationship with capsular formation, remodeling, and clinical outcomes. Methods: The study enrolled 28 women (29 implants) who underwent expander substitution with definitive implant. Contracture severity was evaluated. Specimens were stained with hematoxylin and eosin, Masson trichrome, immunohistochemistry, and immunofluorescence for LL-37, CD68, α-smooth muscle actin, collagen type I and type III, CD31, and Toll-like receptor-4. Results: LL-37 was expressed in macrophages and myofibroblasts of capsular tissue in 10 (34%) and nine (31%) of the specimens, respectively. In eight cases (27.5%), it was expressed by both macrophages and myofibroblasts of the same specimen. In infected capsules, expression by both cell types was found in all (100%) specimens. LL-37 expression by myofibroblasts positively correlated with its expression by macrophages (P < 0.001). Moreover, LL-37 expression by macrophages of periexpander capsules negatively correlated with the severity of capsular contracture on definitive implants (P = 0.04). Conclusions: This study demonstrates the expression of LL-37 in macrophages and myofibroblasts of capsular tissue and its negative correlation with the severity of capsular contracture following permanent implant placement. Expression or up-regulation of LL-37 may be involved in myofibroblast and macrophage modulation, thus playing a role in the pathogenic fibrotic process underlying capsular contracture.