Abstract: Objective To explore the influences of extracellular matrices （ECM） secreted by ultraviolet B （UVB）-induced senescent fibroblasts on the proliferation of and extracellular signal-regulated kinase （ERK） signaling in HaCaT cells. Methods Fibroblasts were irradiated with UVB of 15 mJ/cm2 once daily for 5 days to induce premature senescence, which was identified by SA-β-gal staining 72 hours after the last irradiation. HaCaT cells were divided into 3 groups and inoculated into plates coated with extracellular matrices secreted by non-senescent （PRE-ECM） or senescent fibroblasts （SIPS-ECM） or into uncoated plates （NON-ECM）, followed by additional culture. U0126, an inhibitor of ERK1/2, was used to treat the HaCaT cells 1 hour before inoculation. Then, MTT assay was carried out to detect the proliferation of HaCaT cells after a 3-day culture, Western blot to assess the phosphorylation of ERK at 0.5, 1, 2 and 4 hours after the inoculation, flow cytometry to analyse cell cycle and apoptosis after 24 hours of culture. Results The most rapid and intense phosphorylation of ERK was observed in SIPS-ECM group. Inhibiting the activation of ERK pathway with U0126 could completely suppress the promoting effect of ECM from senescent fibroblasts on the proliferation of HaCaT cells. After the blocking of ERK activation, the proportion of HaCaT cells in S and G2/M phase decreased from 37.40%, 41.34% and 43.31% to 29.41%, 36.48% and 39.96%, respectively, in NON-ECM, PRE-ECM and SCIP-ECM group. Conclusion The ECM produced by UVB-induced senescent fibroblasts promote the proliferation of HaCaT cells via inducing the phosphorylation of ERK.

Key words: Ultraviolet, Mitogen-activated protein kinase kinase