Abstract:

Objective To observe the expression changes of CD34 and M30 in skin homogenate from a mouse model of scleroderma after irradiation with different doses of UVA1, and to investigate the effect of UVA1 phototherapy on vascular endothelial cell function in scleroderma. Methods The experimental mouse models of scleroderma were established by the injection with bleomycin and randomly divided into model control group （n = 10）, UVA1 irradiation group （n = 30） and unirradiated group （n = 10）. The UVA1 irradiation group was further equally divided into 3 groups, HD-UVA1 group irradiated with UVA1 at 100 J/cm2, MD-UVA1 group with UVA1 at 60 J/cm2, and LD-UVA1 group with UVA1 at 20 J/cm2; phototherapy was performed thrice weekly for 10 weeks followed by the sacrifice of mice. The mice in model control group were killed immediately after the establishment of models, and the mice in unirradiated group received no irradiation after the establishment of models and were maintained till the killing of mice in UVA1 irradiation groups. Skin specimens were obtained from the bleomycin-induced scleroderma lesions of mice and separated into two parts, one was subjected to histopathological examination, and the other one was used to prepare skin homogenate for the detection of CD34 and M30 content with ELISA assay. Results After 30 sessions of treatment with UVA1, the softening and thinning of sclerotic skin were seen by the naked eye, with the most obvious changes in HD-UVA1 group; pathological examination revealed a reduction in dermal thickness and the presence of hair follicular structures in subcutaneous fat tissue with no obvious proliferation of collagen in these mice. Compared with the mice in model control group and unirradiated group, there was an increase in CD34 and decrease in M30 content in skin homogenate from UVA1-irradiated mice, with the most marked changes in mice irradiated with UVA1 at 100 J/cm2. The concentration of CD34 and M30 in skin homogenate from unirradiated group and model control group was significantly different from that in HD-UVA1 group （22.25 ± 8.91 μg/L and 31.97 ± 17.97 μg/L vs. 72.39 ± 13.04 μg/L, 162.41 ± 58.00 U/L and 195.71 ± 71.09 U/L vs. 38.06 ± 19.89 U/L, all P < 0.01）. Additionally, significant differences were observed between the three UVA1 groups in the concentration of CD34 and M30 （F = 21.23, 15.32, respectively, both P < 0.01）. Conclusions UVA1 phototherapy could up-regulate the expression of CD34 but down-regulate that of M30 in skin homogenate from the mouse model of scleroderma, and the effect is correlated with the intensity and cumulative dose of irradiation.

Key words: vascular endothelial cell