The biological basis for poly-L-lactic acid-induced augmentation.

ABSTRACT

BACKGROUND: Granulomatous reactions to poly-L-lactic acid (PLLA)-based filler have been described previously. Neither the biological background of these partly late-onset reactions or the desired augmenting effect of PLLA has been studied to date. Histological studies have revealed foreign body reactions and foreign body giant cell formation. OBJECTIVE: The aim of this study was to increase our knowledge about the biological mechanisms behind the augmenting effect of PLLA-based filler. METHODS: We characterised the cell infiltrate and collagen type of PLLA-treated tissue by immunofluorescence staining. The expression of genes related to collagen metabolism was determined. RESULTS: CD68(+) macrophages were found next to PLLA. CD90(+) fibroblasts were found alongside. αSMA-positive structures indicated myofibroblasts and neovascularisation. Substantial collagen type III deposition was detected next to PLLA particles and collagen type I was found at the periphery of PLLA encapsulations. mRNA expression for collagen type I and III transcripts, as well as for TGFß1 and TIMP1, was upregulated significantly. CONCLUSION: PLLA-induced augmentation is most likely based on capsule formation orchestrating macrophages, (myo-)fibroblasts, and collagen type I and III fibres. We observed considerably slower degradation of PLLA particles than described previously. Thus PLLA particles were still retrievable 28 months after subcutaneous application.