Abstract: Objective To develop a model of ultraviolet B （UVB）-induced premature senescence in human skin fibroblasts （HSF） so as to assess the relationship between stress-induced premature senescence and tumorigenesis. Methods The irradiation dose and frequency were optimized for the induction of premature senescence. HSF were irradiated with UVB of 10 mJ/cm2 once daily for 5 days, and unirradiated HSFs served as the control. After the last irradiation, cell proliferation was determined by MTT assay on day 3, 4, 5, 6 and 7, SA β-Gal staining was performed to evaluate the senescence state of cells on day 3, and RT-PCR to detect the expressions of three senescene-associated genes, including fibronectin （FN）, osteonectin （ON） and smooth muscle 22 （SM22） on day 3. Results After five exposures to UVB, HSF showed biological characteristics of senescence. As assessed by MTT assay, there was a loss of replicative potential in irradiated cells. The proportion of SA-β-gal-positive cells was 82.0% in UVB-stressed HSFs and 33.7% in the control cells（P < 0.01）. The mRNA levels of FN, ON and SM22 were upregulated by 2.7, 2.0 and 2.3 folds respectively in irradiated HSF compared with the control cells （all P < 0.05）. Conclusion A stress-induced premature senescence model is established using HSF by repeated exposure to subcytotoxic UVB.

Key words: ultraviolet B