Organisms have an evolutionarily conserved internal rhythm that helps them anticipate and adapt to daily changes in the environment. Synchronized to the light-dark cycle with a period of around 24 hours, the timing of the circadian clock is set by light-triggering signals sent from the retina to the suprachiasmatic nucleus. Other inputs, including food intake, exercise, and temperature, also affect clocks in peripheral tissues, including skin. Here, we review the intricate interplay between the core clock network and fundamental physiological processes in skin such as homeostasis, regeneration, and immune-and stress responses. We illustrate the effect of feeding time on the skin circadian clock and skin functions, a previously overlooked area of research. We then discuss works that relate the circadian clock and its disruption to skin diseases, including skin cancer, sunburn, hair loss, aging, infections, inflammatory skin diseases, and wound healing. Finally, we highlight the promise of circadian medicine for skin disease prevention and management.

Background The development of public health policy is inextricably linked with governance structure. In our increasingly globalized world, human migration and infectious diseases often span multiple administrative jurisdictions that might have different systems of government and divergent management objectives. However, few studies have considered how the allocation of regulatory authority among jurisdictions can affect disease management outcomes. Methods Here we evaluate the relative merits of decentralized and centralized management by developing and numerically analyzing a two-jurisdiction SIRS model that explicitly incorporates migration. In our model, managers choose between vaccination, isolation, medication, border closure, and a travel ban on infected individuals while aiming to minimize either the number of cases or the number of deaths. Results We consider a variety of scenarios and show how optimal strategies differ for decentralized and centralized management levels. We demonstrate that policies formed in the best interest of individual jurisdictions may not achieve global objectives, and identify situations where locally applied interventions can lead to an overall increase in the numbers of cases and deaths. Conclusions Our approach underscores the importance of tailoring disease management plans to existing regulatory structures as part of an evidence-based decision framework. Most importantly, we demonstrate that there needs to be a greater consideration of the degree to which governance structure impacts disease outcomes.

The fungal pathogen Pseudogymnoascus destructans (Pd) causes white‐nose syndrome (WNS), an emerging disease that affects North American bat populations during hibernation. Pd has rapidly spread throughout much of the continent, leading to mass mortality and threatening extinction in several bat species. While previous studies have proposed treatment methods, little is known about the impact of metapopulation dynamics on these interventions. We investigate how the movement of bats between populations could affect the success of five WNS control strategies by posing and analyzing a two‐population disease model. Our results demonstrate that vaccination will benefit from greater bat dispersal, but the effectiveness of treatments targeting fungal growth or disease progression can be expected to diminish. We confirm that successful control depends on the relative contributions of bat‐to‐bat and environment‐to‐bat contact to Pd transmission, and additionally find that the route of transmission can influence whether interpopulation exchange increases or decreases control efficacy. Recommendations for Resource Managers Many WNS controls are under development, but an analysis of host dynamics is needed to select the most effective management strategies. Our study indicates that the long‐term efficacy of control strategies depends on the presence and magnitude of interpopulation movement, and highlights the importance of quantifying bat metapopulation dynamics together with the avenues of Pd transmission. We suggest that movement between populations suppresses the efficacy of most interventions and recommend managers to consider both their combination of control strategies and the primary route of pathogen transmission when evaluating the potential impacts of dispersal. Vaccination was the only intervention strategy to consistently benefit from bat dispersal so, if possible, we advocate for the development and widespread administration of a WNS vaccine.

No abstract

First described in the early 20 th century, diurnal oscillations in stem cell proliferation exist in multiple internal epithelia, including in the gastrointestinal track, and in the epidermis. In the mouse epidermis, 3- to 4-fold more stem cells are in S-phase during the night than during the day. Work that is more recent showed that an intact circadian clock intrinsic to keratinocytes is required for these oscillations in epidermal stem cell proliferation. The circadian clock also regulates DNA excision repair and DNA-damage in epidermal stem cells in response to ultraviolet B radiation. During skin inflammation, epidermal stem cell proliferation is increased and diurnal oscillations are suspended. Here we discuss possible reasons for the evolution of this stem cell phenomenon. We argue that the circadian clock coordinates intermediary metabolism and the cell cycle in epidermal stem cells to minimize accumulation of DNA damage from metabolism-generated reactive oxygen species. Circadian disruption, common in modern society, leads to asynchrony between metabolism and the cell cycle, and we speculate this will lead to oxidative DNA damage, dysfunction of epidermal stem cells, and skin aging.