ORAL PSORALEN WITH UV-A THERAPY RELEASES CIRCULATING GROWTH FACTOR(S)THAT STIMULATES CELL-PROLIFERATION

Background: The mechanism by which oral psoralen with UV-A (PUVA) stim ulates melanocyte proliferation in vitiligo is unknown. This study was conducted to examine the hypothesis that it does so by stimulating th e release of growth factors that stimulate melanocyte proliferation. D esign: We examined the effect of serum samples obtained from patients with vitiligo before and following 2 and 4 months of PUVA therapy, and from non-PUVA-treated patients with vitiligo and normal individuals o n the growth of melanocytes in vitro. Setting: Outpatient clinic in re ferral center. Patients: The study was conducted on serum samples obta ined from 18 patients with vitiligo, 8 of whom were treated with PUVA, and from 10 normal individuals. Intervention: Treatment with PUVA. Ma in Outcome Measure: Ability of serum samples to stimulate the growth o f melanocytes in culture. Results: Proliferation of melanocytes in ser um collected after 4 months of PUVA therapy was on the average 3-fold greater than that in serum samples collected from the same patients pr ior to therapy with PUVA. This circulating growth factor was absent in serum samples of non-PUVA-treated patients with vitiligo and normal i ndividuals. The effect was nonspecific, as it also stimulated the prol iferation of fibroblasts. Conclusions: These findings suggest that PUV A treatment results in the release into the circulation of growth fact or(s) that can stimulate a proliferation of melanocytes and of other c ells. This could account for the repigmentation of vitiligo by PUVA tr eatment. As the growth factor(s) also stimulated the growth of other c ells, it could also explain the thickening of the epidermis that occur s following exposure to UV light.