Cytokines and growth factors influence hair growth in vitro. Possible implications for the pathogenesis and treatment of alopecia areata

Abstract

Factors that influence the growth of the anagen hair follicle or initiate the switch to a catagen growth pattern have so far not been definitely determined, but there is increasing evidence that cytokines and growth factors play an important role during these processes. Recently we detected an aberrant in situ expression pattern of cytokines of the Th1 type (IFNγ, IL-2) plus IL-1β expression in untreated alopecia areata (AA), and a switch to high levels of IL-10 TGF-β1 expression after successful treatment with the contact allergen diphenylcyclopropenone (DCP). Hence the question arose as to whether cytokines are able to arrest hair growth and whether IL-10 or TGFβ1 have the capacity to antagonize this process. Using whole-organ cultures of microdissected human hair follicles we studied the effect of a panel of cytokines and growth factors on hair growth and on the gross morphology of the hair follicles in vitro. IL-2, IL-10 and IFN-γ had no effect in this regard, whereas TGFβ1 partially inhibited hair growth and EGF, TNFα and IL-1β completely abrogated it. EGF and TNFα induced the formation of a club-like hair follicle, similar to catagen morphology of the hair bulb, whereas hair follicles grown in the presence of IL-1β or TGFβ1 showed no particular morphological changes. We conclude that cytokines and growth factors are pivotal regulators of hair growth at least in vitro. IL-1 is suggested as playing an important role during the pathogenesis of AA. Possible mediators of therapeutic contact dermatitis (IL-10, TGFβ1, TNFα, PGE₂) are, at least in vitro, not able to antagonize the IL-1β-triggered hair growth inhibition. Therefore, we infer that these mediators rather ‘modulate’ the immune response in AA.