Stem cells cycle through active and quiescent states. Large populations of stem cells in an organ may cycle randomly or in a coordinated manner. Although stem cell cycling within single hair follicles has been studied, less is known about regenerative behavior in a hair follicle population. By combining predictive mathematical modeling with in vivo studies in mice and rabbits, we show that a follicle progresses through cycling stages by continuous integration of inputs from intrinsic follicular and extrinsic environmental signals based on universal patterning principles. Signaling from the WNT/bone morphogenetic protein activator/inhibitor pair is coopted to mediate interactions among follicles in the population. This regenerative strategy is robust and versatile because relative activator/inhibitor strengths can be modulated easily, adapting the organism to different physiological and evolutionary needs.

SUMMARY Coordinated organ behavior is crucial for an effective response to environmental stimuli. By studying regeneration of hair follicles in response to patterned hair removal, we demonstrate that organ-level quorum sensing allows coordinated responses to skin injury. Removing hair at different densities leads to a regeneration of up to 5 times more neighboring, unplucked resting hairs, indicating activation of a collective decision-making process. Through data modeling, the range of the quorum signal was estimated to be on the order of 1 mm, greater than expected for a diffusible molecular cue. Molecular and genetic analysis uncovered a two-step mechanism, where release of CCL2 from injured hairs leads to recruitment of TNF-α secreting macrophages, which accumulate and signal to both plucked and unplucked follicles. By coupling immune response with regeneration, this mechanism allows skin to respond predictively to distress, disregarding mild injury, while meeting stronger injury with full-scale cooperative activation of stem cells.

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The aim of this study was to determine the prevalence, treatment modalities and comorbidity of psoriasis in Taiwan. A nationally representative cohort of 1,000,000 individuals from the National Health Insurance database was followed up for the years 2000 to 2006. Their claims data was used for an epidemiological study. The mean one-year prevalence of psoriasis was 0.23% for men and 0.16% for women, respectively. The prevalence of psoriasis increased more rapidly in male patients aged 30 years and over and reached its peak in patients aged 70 years and over, regardless of sex. Overall, 98.4% of patients received treatment with topical corticosteroids, while 13.1% used Chinese herbal medicines and 13.6% received systemic treatment. Patients with psoriasis had a higher comorbidity of diabetes, hyperlipidaemia, and hypertension. In conclusion, in contrast to Caucasians, the prevalence of psoriasis in Taiwanese people is high er in men than in women and the prevalence increases significantly in patients over 70 years of age.

It has long been a debate that whether atopy is a risk factor or protective factor for cancer. However, no large‐scale study of different cancers in patients with atopic diseases has been conducted among Asians. Here, we conducted a nationwide study to evaluate the cancer risk in patients with allergic rhinitis (AR), asthma and atopic dermatitis (AD). Drawing on Taiwan's National Health Insurance Research Database, 225,315 patients with AR, 107,601 patients with asthma and 34,263 patients with AD without prior cancers were identified in the period from 1996 to 2008. The standard incidence ratio (SIR) of each cancer was calculated. Although the overall cancer risks in patients with atopic symptoms were not increased, the risks were slightly elevated in female patients with AR or asthma (SIR: 1.13 and 1.08, AR and asthma, respectively) and slightly decreased in males patients with AR. Those aged 20–39 years‐old possessed the highest risk. A higher risk of developing brain cancer was found in patients with atopic diseases, and patient with AR or asthma also had an elevated risk of developing cancer of kidney and urinary bladder. In contrast, the risk of nonmelanoma skin cancer was lower in patients with AR and asthma. Compared to patients with only one atopic disease, those with more than one atopic disease had lower cancer risks. Our data suggests that the association between atopy and cancer is site‐specific.

To study the prevalence of atopic dermatitis, allergic rhinitis, and asthma in Taiwan, we analysed the claims data of a nationally representative cohort of 997,729 enrolees from the National Health Insurance register from 2000 to 2007. Overall, 66,446 patients were diagnosed with atopic dermatitis, and 49.8% of them had concomitant allergic rhinitis and/or asthma. The overall 8-year prevalences of atopic dermatitis, allergic rhinitis, and asthma were 6.7%, 26.3% and 11.9%, respectively. Children and adolescents had significantly higher prevalences of these atopic diseases. The prevalence of atopic dermatitis in females was lower than that in males before the age of 8 years, but became higher after that. Patients with atopic dermatitis were more likely to have allergic rhinitis and asthma. Those having both atopic dermatitis and allergic rhinitis possessed an even higher risk for asthma (odds ratio 9.04). The numbers of visits for atopic dermatitis were highest in late spring to mid-summer. These data suggest that atopic diseases are common in Taiwan.

To analyse the epidemiological characteristics and related costs of herpes zoster in Taiwan, a nationally representative cohort of 1,000,000 individuals from the National Health Insurance register was followed up from 2000 to 2006 and their claims data analysed. Overall, 34,280 patients were diagnosed with zoster (incidence 4.89/1000 person-years) and 2944 patients (8.6%) developed post-herpetic neuralgia 3 months after the start of the zoster rash (incidence 0.42/1000 person-years). People with older age, diabetes, and immunocompromising conditions were at higher risk of developing zoster and post-herpetic neuralgia. The overall hospitalization rate for zoster was 16.1 cases per 100,000 person-years. The cost for each home care case and per hospitalized case were approximately 53.30 euro and 1224.70 euro, respectively. Further research into the cost-effectiveness of zoster vaccine is needed.

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