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

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. 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. 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). 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.