ABSTRACT
BACKGROUND@#Hair follicles are among a handful of organs that exhibit immune privilege. Dysfunction of the hair follicle immune system underlies the development of inflammatory diseases, such as alopecia areata. @*METHODS@#Quantitative reverse transcription PCR and immunostaining was used to confirm the expression of major histocompatibility complex class I in human dermal papilla cells. Through transcriptomic analyses of human keratinocyte stem cells, major histocompatibility complex class I was identified as differentially expressed genes. Organ culture and patch assay were performed to assess the ability of WNT3a conditioned media to rescue immune privilege. Lastly, CD8? T cells were detected near the hair bulb in alopecia areata patients through immunohistochemistry. @*RESULTS@#Inflammatory factors such as tumor necrosis factor alpha and interferon gamma were verified to induce the expression of major histocompatibility complex class I proteins in dermal papilla cells. Additionally, loss of immune privilege of hair follicles was rescued following treatment with conditioned media from outer root sheath cells. Transcriptomic analyses found 58 up-regulated genes and 183 down-regulated genes related in MHC class I? cells. Using newborn hair patch assay, we demonstrated that WNT3a conditioned media with epidermal growth factor can restore hair growth. In alopecia areata patients, CD8? T cells were increased during the transition from mid-anagen to late catagen. @*CONCLUSION@#Identification of mechanisms governing epithelial and mesenchymal interactions of the hair follicle facilitates an improved understanding of the regulation of hair follicle immune privilege.
ABSTRACT
Background@#Particulate matters (PM) comprise a heterogeneous mixture of particles suspended in air. A recent study found that urban PMs may penetrate into hair follicles via transfollicular and transdermal routes in dorsal skin. @*Objective@#To investigate the effects of PM on ex vivo cultured human scalp hair follicles and hair follicular keratinocytes in vitro. @*Methods@#TUNEL staining was employed to check cells undergoing apoptosis in cultured hair follicles after PM treatment. MTT assay was employed to check cell viability after PM treatment. Quantitative real-time PCR analysis was employed to quantitate the expression of inflammatory genes, matrix metalloproteinases (MMPs), and Duox1. Inflammatory cytokine levels were measured by ELISA after PM treatment. The level of reactive oxygen species (ROS) production was measured using a chemical fluorescent probe by a fluorescence plate reader. Results: Abundant TUNEL-positive cells were observed in the keratinocyte region of hair including the epidermis, sebaceous gland, outer root sheath (ORS), inner root sheath (IRS), and bulb region. The viability of follicular cells, including the ORS, was found to be decreased upon PM exposure. mRNA expression and protein levels of inflammatory response genes and MMPs were upregulated in a dose-dependent manner by PM treatment. ROS levels were also increased by PM. @*Conclusion@#These data strongly suggest that penetrated PMs from air pollution may cause apoptotic cell death to follicular keratinocytes by increased production of ROS and inflammatory cytokines, which could impair hair growth.