Abstract
Keloids are pathological scars characterized by excessive proliferation of fibroblasts and abnormal extracellular matrix (ECM) accumulation, largely mediated by transforming growth factor-β1 (TGF-β1). Current therapeutic approaches often fail due to high recurrence and limited selectivity. Here, we investigate the potential of human hair-derived keratin (HK) as a biomaterial with selective anti-fibrotic activity. Using multiple in vitro models including 2D monolayers, 3D spheroids, fibroblast-keratinocyte coculture, and collagen gel contraction, we evaluated the effects of 0.5% HK on keloid fibroblasts (KFs) and normal dermal fibroblasts (DFs), with and without TGF-β1 stimulation. HK selectively inhibited KF proliferation, viability, and migration while sparing DF. In 3D models, HK significantly reduced KF-mediated spheroid expansion and collagen matrix contraction, even under profibrotic stimulation. Mechanistically, HK activated intrinsic apoptotic signaling, up-regulating pro-apoptotic proteins (Bax, caspase-3, CYCS) and down-regulating Bcl-2 and XIAP. Transcriptomic profiling revealed that HK down-regulated pathways associated with ECM-receptor interaction, focal adhesion, and aminoacyl-tRNA biosynthesis in KF, suggesting a dual modulation of fibrotic remodeling and mitochondrial function. These findings demonstrate that HK exerts selective anti-fibrotic and pro-apoptotic effects on pathological fibroblasts, with minimal impact on normal cells. By modulating both ECM organization and cell survival pathways, keratin demonstrates strong potential as a therapeutic biomaterial for targeted keloid treatment.