Fig. 6. Proposed model based on this study. Penetrated PM enters hair component cells via epidermal and transfollicular routes to increase ROS production and upregulate inflammatory cytokines and MMPs in follicular keratinocytes, which in turn results in apoptotic cell death and inflammation. Thereby, penetrated PMs from air pollution may have negative effects on hair growth. PM: particulate matter, ROS: reactive oxygen species, MMPs: matrix metalloproteinases.
