Intralesional Adipose-Derived Stem Cells Reverse Established Dermal Fibrosis and Modulate Angiogenesis-Related Readouts in a Murine Systemic Sclerosis Model

Background: Systemic sclerosis (SSc) is characterized by progressive dermal fibrosis and microvascular dysfunction, and no approved therapy reliably reverses established skin fibrosis or durably restores microvascular perfusion. Adipose-derived stem cells (ASCs) possess anti-fibrotic, immunomodulatory, and vascular-related parameters properties, but their therapeutic impact in a strictly therapeutic (rather than preventive) SSc-like setting remains incompletely defined. Methods: Bleomycin-induced systemic sclerosis model was induced in male C57BL/6 mice by daily subcutaneous bleomycin injections (100 μg) into dorsal skin for 28 days. On day 14, mice received a single intralesional injection of ASCs (1 × 10⁵ cells) or vehicle. At day 28, cutaneous perfusion was measured by laser Doppler perfusion imaging, and dorsal skin was analyzed by histology, hydroxyproline assay, RT-qPCR, and immunohistochemistry for CD34, α-SMA, and TNF-α. To support mechanistic interpretation, TGF-β1–stimulated dermal fibroblasts were co-cultured with ASCs and fibrosis-related gene expression was assessed. Results: Intralesional ASC administration significantly attenuated bleomycin-induced dermal fibrosis, reducing dermal thickness (244.0–163.5 μm) and collagen area fraction (87.2–62.8%). Hydroxyproline content decreased from 0.187 to 0.121 μg/mg tissue. ASC treatment also suppressed profibrotic and inflammatory transcripts (α-SMA ~ 3.99-fold, TGF-β1 ~ 6.07-fold, TNF-α ~ 7.48-fold, IL-6 ~ 2.36-fold vs. BLM + PBS) and increased vascular responses transcripts (VEGF ~ 2.65-fold, CD34 ~ 1.28-fold vs. BLM + PBS). ASC co-culture suppressed profibrotic activation of TGF-β1–stimulated fibroblasts, reducing profibrotic expression (α-SMA ~ 2.5-fold, TGF-β1 ~ 3.5 -fold, and COL1A1 ~ 2.7-fold). Conclusions: A single intralesional ASC injection alleviated established bleomycin-induced dermal fibrosis and was associated with vascular-related changes in fibrotic tissue. These effects may involve paracrine-mediated suppression of TGF-β1–driven fibroblast activation, supporting ASCs as a promising regenerative strategy for systemic sclerosis skin disease.