PD17 Skin-derived precursor conditioned-medium-alleviated photoageing via early activation of the transforming growth factor-β/Smad signalling pathway by thrombospondin 1: <i>in vitro</i> and <i>in vivo</i> studies

Abstract Photoageing is one major exogenous factor of skin ageing. Our previous studies indicated that skin-derived precursors (SKPs) alleviated photodamage by early activation of the transforming growth factor (TGF)-β/Smad signalling pathway via thrombospondin 1 (TSP1). However, research concerning SKP-conditioned medium (CM) has never been reported. In the current study, we aimed to explore the antiphotoageing effects of SKP-CM both in vitro and in vivo, and to elucidate the possible mechanisms. Mouse SKP-CM (mSKP-CM) collection was optimized by a comparative method. The concentration of protein and growth factors in mSKP-CM was detected using a BCA protein assay kit and growth factor protein chip. The antiphotoageing effects of mSKP-CM and its regulation of key factors in the TGF-β/Smad signalling pathway were explored using ultraviolet A + B photoaged mouse fibroblasts and nude mice dorsal skin. The research revealed that mSKP-CM contained a significantly higher concentration of protein and growth factors than mouse mesenchymal stem-cell-conditioned medium (mDMSC-CM). mSKP-CM alleviated photoageing of mouse fibroblasts by restoring cell viability and relieving senescence and death. Enzyme-linked immunosorbent assay, quantitative reverse-transcriptase polymerase chain reaction and Western blot results implied the potential mechanisms were associated with the early activation of the TGF-β/Smad signalling pathway by TSP1. In vivo experiments demonstrated that compared with topical intradermal mDMSC-CM injection and application of retinoic acid cream, the photodamaged mice dorsal skin intradermally injected with mSKP-CM showed significantly better improvement. Consistently with the in vitro results, both Western blot and immunohistochemistry results confirmed that protein expression of TSP1, SMAD2/3, p-SMAD2/3, TGF-β1 and collagen I increased, and matrix metalloproteinases decreased. In summary, both in vitro and in vivo experiments demonstrated that mSKP-CM alleviated photoageing through early activation of the TGF-β/Smad signalling pathway via TSP1. SKP-CM may serve as a novel and promising cell-free therapeutic approach for antiphotoageing treatment and regenerative medicine.