biostudies-literatureUnknown12(9)Oh SPoly-L-lactic acid (PLLA) fillers correct cutaneous volume loss by stimulating fibroblasts to synthesize collagen and by augmenting the volume. PLLA triggers the macrophage-induced activation of fibroblasts that secrete transforming growth factor-β (TGF-β). However, whether M2 macrophage polarization is involved in PLLA-induced collagen synthesis via fibroblast activation in aged skin is not known. Therefore, we evaluated the effect of PLLA on dermal collagen synthesis via M2 polarization in an H<sub>2</sub>O<sub>2</sub>-induced cellular senescence model and aged animal skin. H<sub>2</sub>O<sub>2</sub>-treated macrophages had increased expression levels of the M1 marker CD80 and decreased expression levels of the M2 marker CD163, which were reversed by PLLA. The expression levels of interlCells1320https://www.ebi.ac.uk/biostudies/studies/S-EPMC10177436biostudies-literaturePoly-L-Lactic Acid Fillers Improved Dermal Collagen Synthesis by Modulating M2 Macrophage Polarization in Aged Animal Skin.PMC10177436Lee MHKim HMByun KOh SSung MJSon KHBatsukh SLim THLee JHfalsePoly-L-Lactic Acid Fillers Improved Dermal Collagen Synthesis by Modulating M2 Macrophage Polarization in Aged Animal Skin.Poly-L-lactic acid (PLLA) fillers correct cutaneous volume loss by stimulating fibroblasts to synthesize collagen and by augmenting the volume. PLLA triggers the macrophage-induced activation of fibroblasts that secrete transforming growth factor-β (TGF-β). However, whether M2 macrophage polarization is involved in PLLA-induced collagen synthesis via fibroblast activation in aged skin is not known. Therefore, we evaluated the effect of PLLA on dermal collagen synthesis via M2 polarization in an H<sub>2</sub>O<sub>2</sub>-induced cellular senescence model and aged animal skin. H<sub>2</sub>O<sub>2</sub>-treated macrophages had increased expression levels of the M1 marker CD80 and decreased expression levels of the M2 marker CD163, which were reversed by PLLA. The expression levels of interl2023-01-01T00:00:00Z2023 May2025-04-05T16:14:23.644Z2025-04-05T16:14:23.644ZS-EPMC101774363717472010.3390/cells12091320