Curcumin alleviates hypertrophic scarring by inhibiting fibroblast activation and regulating tissue inflammation

Hypertrophic scar (HS) that can lead to defects in appearance and function is often characterized by uncontrolled fibroblast proliferation and excessive inflammation. Curcumin has been shown to have anti-inflammatory and anti-oxidative effects and to play an anti-fibrotic role by interfering transforming growth factor-β1 (TGF-β1)/Smads signaling pathways.

To study the effect and mechanism of curcumin on HS from the perspective of fibroblast activity and inflammation regulation.

Cell proliferation, migration and the expression of α-smooth muscle actin (α-SMA) of TGF-β1-induced human dermal fibroblasts (HDFs) treated by curcumin were evaluated using Cell Counting Kit-8 assay, 5-ethynyl-2'-deoxyuridine staining, Transwell assay, Western blotting and immunofluorescence, respectively. The expression of TGF-β1/Smad3 pathway-related molecules (TGF-β1, TGFβ-R1/2, p-Smad3, Smad4) was detected by Western blotting. In a rabbit ear model, hematoxylin and eosin and Masson's staining were conducted to assess scar elevation and collagen deposition, and immunohistochemistry was performed to detect the activation of fibroblasts and infiltration of inflammatory cells.

Curcumin inhibited proliferation, migration and α-SMA expression of HDFs in a dose-dependent manner. Curcumin (25 μm mol/L) did not regulate the expression of endogenous TGF-β1, but suppressed Smad3 phosphorylation and nuclear translocation, leading to lower α-SMA expression. Curcumin also reduced hypertrophic scarring of rabbit ear, accompanied by the inhibited TGF-β1/Smad3 pathway, inflammatory infiltration and M2 macrophage polarization.

Curcumin plays an anti-scar role through regulating fibroblast activation and tissue inflammation. Our findings provide scientific reference for the clinical use of curcumin in the treatment of HS.