Novel approach to hypertrophic scar treatment based on evidence of bacterial overload

doi:10.3969/j.issn.1674-8115.2026.05.004

Abstract

Abstract:

Objective ·To investigate the effects of bacteria on fibroblast function in vitro and the impact of bacterial intervention on hypertrophic scars in rabbit ears in vivo. Methods ·A total of 16 clinical hypertrophic scar specimens and normal skin tissues were collected from patients admitted to the Department of Burns, Plastic Surgery and Wound Repair, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, from January 2023 to December 2024, and subjected to Gram staining. After amplification and inactivation, standard Staphylococcus aureus was used to treat fibroblasts derived from normal skin at concentrations of 10², 10³, and 10⁴ CFU/mL. The effects on fibroblast proliferation were observed by using Edu staining, while α-smooth muscle actin (α-SMA) expression was detected by immunofluorescence. The expression levels of vascular endothelial growth factor (VEGF), transforming growth factor-β1 (TGF-β1), type Ⅰ collagen and type Ⅲ collagen were measured by Western blotting. Additionally, the secretion of inflammatory cytokines, including interleukin-6 (IL-6), interleukin-8 (IL-8), tumor necrosis factor-α (TNF-α), and monocyte chemoattractant protein-1 (MCP-1), was evaluated by using enzyme-linked immunosorbent assay (ELISA). In the in vivo study, 80 wounds were created on the ears of 10 New Zealand white rabbits, followed by inoculation with Staphylococcus aureus. After hypertrophic scar formation, intradermal injections of levofloxacin or saline were administered. Scar growth was monitored, and Vancouver Scar Scale scores were recorded. Scar tissues were harvested for hematoxylin and eosin staining, Masson staining, and Gram staining, along with immunohistochemical detection of IL-6, IL-8, TNF-α, and MCP-1 expression. Results ·Clinical scar tissues exhibited significantly greater abundance of Gram-positive bacteria than normal skin tissues (P=0.001). In vitro experiments demonstrated that low-abundance bacteria (10² and 10³ CFU/mL) significantly promoted fibroblast proliferation (P=0.045, P=0.017) and α-SMA expression (P=0.042, P=0.002). These bacteria also enhanced the expression of VEGF (P=0.023, P=0.011), TGF-β1 (P=0.029, P=0.031), type Ⅰ collagen (P=0.032, P=0.025), and type Ⅲ collagen (P=0.019, P=0.027), as well as the secretion of inflammatory cytokines IL-6 (P=0.023, P=0.011), IL-8 (P=0.021, P=0.009), TNF-α (P=0.029, P=0.011), and MCP-1 (P=0.023, P=0.008). In the rabbit ear model, levofloxacin injection significantly reduced scar hyperplasia at 45 and 60 days (P=0.019, P=0.013). At 60 days, treated scars showed decreased inflammatory cell infiltration, reduced bacterial load, less collagen deposition, and lower expressions of IL-6 (P=0.025), IL-8 (P=0.021), MCP-1 (P=0.028), and TNF-α (P=0.019). Conclusions ·Low-abundance bacteria promote the profibrotic capacity of scar fibroblasts, while antibiotic application effectively mitigates hypertrophic scar formation.

Key words: hypertrophic scar, bacteria, fibroblast, inflammatory cytokine

CLC Number:

R453.2

Yuan Bo, Yu Jiarong, Zhang Zheng, Wang Xiqiao, Liu Yan, Xia Zhaofan. Novel approach to hypertrophic scar treatment based on evidence of bacterial overload[J]. Journal of Shanghai Jiao Tong University (Medical Science), 2026, 46(5): 585-593.

Figures/Tables 8

Fig 1 Gram staining results of normal skin and hypertrophic scar tissues

Fig 2 Changes in fibroblast proliferation after treatment with different bacterial concentrations detected by Edu assay

Fig 3 Secretion levels of IL-6, IL-8, TNF-α, and MCP-1 in fibroblasts after treatment with different concentrations of bacteria

Fig 4 Effects of different bacterial concentrations on the protein expression of VEGF, TGF-β1, type Ⅰ collagen, and type Ⅲ collagen in fibroblasts

Fig 5 Changes in α-SMA expression in fibroblasts after exposure to different bacterial concentrations

Fig 6 Scar appearance and Vancouver Scar Scale scores at different time points after levofloxacin injection in rabbit ear hypertrophic scars

Fig 7 Histological staining of rabbit ear hypertrophic scars at day 60 after levofloxacin injection

Fig 8 Expression of inflammatory cytokines IL-6, IL-8, TNF-α, and MCP-1 in rabbit ear hypertrophic scar tissues after intralesional injection of levofloxacin

TrendMD

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