Knockdown of lysyl oxidase like 1 inhibits the proliferation and pro-fibrotic effects of transforming growth factor-β1-induced hypertrophic scar fibroblasts

The excessive healing response during wound repair can result in hypertrophic scars (HS). Lysyl oxidase like 1 (LOXL1) has been reported to be associated with fibrosis via targeting transforming growth factor β1 (TGF-β1) signaling. This study aimed to investigate the effect of LOXL1 on HS formation. The expression of LOXL1 in HS tissues and TGF-β1-induced HS-derived fibroblasts (HSFs) was detected via reverse transcription quantitative PCR and Western blot. LOXL1 was silenced in HSFs using transfection with short hairpin RNA (shRNA), then wound healing process including cell proliferation, cell cycle distribution, migration, and extracellular matrix (ECM) deposition along with Smad expression were measured by cell counting kit-8, EdU staining, flow cytometry, transwell, immunofluorescence, and Western blot assays. LOXL1 was upregulated in HS tissues and TGF-β1-induced HSFs. Knockdown of LOXL1 inhibited proliferation and migration but promoted cell cycle G0/G1 phase arrest in TGF-β1-induced HSFs; it increased expression of cyclin D1, CDK4, MMP2, MMP9, COL1A1, COL1A2, fibronectin, COL3A1, α-SMA, but decreased expression of p27, and the phosphorylation of Smad2 and Smad3 caused by TGF-β1 were also blocked by LOXL1 silencing. Silence of LOXL1 could effectively inhibit TGF-β1-induced proliferation, migration, and ECM deposition in HSFs via inactivating Smad pathway. Targeting LOXL1 may have future therapeutic implications for HS treatment.