Ultraviolet B light induced premature senescence in human dermal papilla cells. Effect on epithelial-mesenchymal interactions

MARTINEZ, NAHUEL MATÍAS; HAGELIN, KARIN; OPPENHEIMER, FLORENCIA MAIA; BALAÑÁ, MARÍA EUGENIA; CERUTI, JULIETA MARÍA

Congreso; LXVII REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC); 2022

The hair follicle (HF) is a mini-organ that supports the cyclical growth of hair starting with differentiation of hair follicle stem cells (HFSC) induced by dermal papilla cells (DPC). Baldness, as consequence of HF miniaturization  is a typical  aging  phenotype. In balding DPC, decrease in proliferation is associated with premature cell senescence. Senescent cells generate a complex mix of signals known as senescence associated secretory phenotype (SASP) that promotes inflammation and tissue damage. The aim of this work was to generate a model of UVB induced-senescence in human DPC grown as spheroids and to study its effect on HFSC differentiation. DPC irradiated six times with 4 mJ/cm2 UVB went into cell cycle arrest and decreased their metabolic activity measured by MTS assay (59%) comparable to cells grown with low serum concentration. UVB damaged DPC also showed high β-galactosidase activity (52% of cells) and higher expression of p16INK4a and p21Cip1 mRNAs, markers of cellular senescence, as cells treated with camptothecin (20 nM) or H2O2 (50 µM). The percentage of UVB treated cells that suffered apoptosis or necrosis (9,34%) was not significant compared with untreated cells (13,84%), measured as Anexin V binding by flow citometry. HFSC were cultured with conditioned media from DPC spheroids previously irradiated or not. Differentiation of HFSC to hair lineage, determined by the expression of keratin K6hf (K75)  was impaired in conditioned medium from UVB induced senescent DPC spheroids (UVB 0,4 vs. C 3,7 fold expression). The expression of SASP components IL-1α, IL-1β, IL-6 and MMP-1 was significantly increased in UVB treated DPC spheroids. Moreover, Dkk-1, an inhibitor of HFSC differentiation was up-regulated, whereas mRNA of Wnt10b, known inducer of differentiation, was downregulated by UVB. We conclude that senescent DPC lose their inductive ability, deregulating epithelial (HFSC)-mesenchymal (DPC) interactions and thus driving hair follicle aging.