Background: Hair loss following skin inflammation may in part be mediated by keratinocyte (KC) apoptosis. While the effects of different cytokines or other apoptosis stimulating agents such as interferon (IFN)-γ or tumour necrosis factor (TNF)-α on KC. apoptosis in vitro have been addressed in several studies, little is known about the effects of proinflammatory cytokines on KC apoptosis in vivo. Objectives: To study the effects of intradermally injected TNF-α, interleukin (IL)-1β and IFN-γ on KC apoptosis in the back skin of C5 7BL/6 mice. Methods Apoptosis in epidermal and hair bulb KCs was analysed by immunohistology using TUNEL staining. Results: Injection of TNF-α induced a significantly higher number of apoptotic cells within the epidermis than vehicle; all three proinflammatory cytokines together further increased their number. Intrafollicular hair bulb KCs were much more susceptible to apoptosis induction by TNF-α or IL-1β; their injection significantly upregulated apoptosis after 6 h, which was further increased after 24 h. The combination of all cytokines together accelerated intrafollicular apoptosis after 6 h by doubling the number of apoptotic cells per hair bulb, compared with the effects of TNF-α or IL-1β alone. Conclusions: These data suggest that programmed cell death of proliferating KCs in vivo can be induced by proinflammatory cytokines.
- Hair bulb
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