Insulin‐like growth factor‐1 in psoriatic plaques treated with PUVA and methotrexate

Background The pathogenesis of psoriasis is thought to depend on the activation of immune cells and their secreted cytokines, chemokines and growth factors like IGF‐1 which may contribute to the epidermal hyperplasia of psoriasis. Treatment of psoriasis with PUVA and methotrexate are associated with clinical improvement and decrease in epidermal hyperplasia. Objective To examine the effects of PUVA and methotrexate therapy on IGF‐1 expression in psoriatic plaques and whether this change correlates with clinical response. Methods For 24 psoriatic patients, the PASI score and levels of lesional IGF‐1 and its mRNA were determined by RT‐PCR before and after treatment with either methotrexate or PUVA. Skin biopsies from 12 healthy volunteers served as control for IGF‐1 levels in normal skin. Results Lesional skin of psoriatic patients showed a statistically significant elevation in IGF‐1 and its mRNA levels in comparison to control (P = 0.0001). Both methotrexate and PUVA treatment were associated with a significant decrease in both PASI scores and lesional IGF‐1 after 10 month treatment. Conclusion Both methotrexate and PUVA therapy for psoriasis are associated with a decrease in PASI score and IGF‐1. The IGF‐1 down‐regulation may possibly be a consequence of the decrease in cytokines and inflammatory cellular infiltrate that occur following treatment with either modalities or due to their effect on local fibroblast activity and proliferation.