Abstract： Objective To evaluate the influence of narrow-band ultraviolet B on lesional microvessel density (MVD),vascular endothelial growth factor (VEGF),matrix metalloproteinases 2 (MMP-2)as well as on serum VEGF in patients with psoriasis vulgaris(PV).Methods Fifteen patients with PV were recruited into this study with 10 normal human controls.All patients received NB-UVB phototherapy thrice a week for 4-5 weeks.Prior and after the treatment,psoriasis area and severity index (PASI)was calculated,tissue specimens were taken from non-photoexposed lesions,and sera samples were obtained from these patients.Then,MvD and the expression level of VEGF and MMP-2 were measured by immunohistochemical labeled dextran polymer(LDP)method in the tissue specimens.Also,the serum level of VEGF was tested by enzyme-linked immunosorbent assay(ELISA).Results PASI score remarkably decreased in patients after the photothempy(t=13.35,P＜0.01).The MVDs were 20.52±5.02,7.33±1.24 and 4.26±0.79 capillaries per high power field(400 × amplification),in psoriatic lesions before treatment,after treatment,and normal control tissues,respectively,with a significant difference among the three groups (F=97.57,P＜0.05),and a significant increase was observed in the lesions before treatment compared with those after treatment and normal controls.The serum level of VEGF was 307.55±121.65 ng/L in psoriatic lesions before treatment,significantly higher than that after treatment(163.92±95.57 ng/L),and in normal control skin (139.78±79.06 ng/L),whereas there was no significant difference between the latter two groups(P＞0.05).The positivity rate of MMP-2 was similar among the three groups without statistical difference(P＞0.05).In psoriatic patients,a positive correlation was observed among PASI score,MVD,lesional and serum VEGF levels(P＜0.05),also among the MVD,VEGF and MMP-2 levels in lesions(P＜0.05).but lesional MMP-2 was unrelated to PASI score or sgrum VEGF(both P＞0.05).Conclusions NB-UVB may regulate superficial dermal microvascular proliferation by acting on the expression of VEGF in sera and lesions of psoriatic patients.VEGF and MMP-2 may bOth participate in the proliferation process of microvessels,while MMP-2 is unlikely to be involved in the therapeutic mechanism of NB-UVB.