Tissues and cells in organism are continuously exposed to complex mechanical cues from the environment. Mechanical stimulations affect cell proliferation, differentiation, and migration, as well as determining tissue homeostasis and repair. By using a specially designed skin-stretching device, we discover that hair stem cells proliferate in response to stretch and hair regeneration occurs only when applying proper strain for an appropriate duration. A counterbalance between WNT and BMP-2 and the subsequent two-step mechanism are identified through molecular and genetic analyses. Macrophages are first recruited by chemokines produced by stretch and polarized to M2 phenotype. Growth factors such as HGF and IGF-1, released by M2 macrophages, then activate stem cells and facilitate hair regeneration. A hierarchical control system is revealed, from mechanical and chemical signals to cell behaviors and tissue responses, elucidating avenues of regenerative medicine and disease control by demonstrating the potential to manipulate cellular processes through simple mechanical stimulation.

Vitiligo is an autoimmune disease characterized by destruction of melanocytes and associated with other autoimmune disease. Whether the dysregulation of immune system enhances oncogenesis or not remains obscure. Until now, no nationwide population-based study has been conducted regarding this. As such, this paper aims to clarify cancer risk in vitiligo patients. A retrospective nationwide population-based cohort study between 2000 and 2010 was performed based on data from the National Health Insurance Research Database of Taiwan. Standardized incidence ratios (SIRs) of cancers were analyzed. Among the 12,391 vitiligo patients (5364 males and 7027 females) and 48,531.09 person-years of observation, a total of 345 cancers were identified. Significantly increased SIRs were observed for prostate cancer in male patients, thyroid cancer and breast cancer in female patients and bladder cancers in both male and female patients. Unfortunately, the low incidence rate of certain cancers limited the power of our statistical analyses. This study demonstrated the patterns of malignancies in vitiligo patients of Taiwan. Compared with the general population, male patients had higher risks of prostate cancer and female patients had higher risks of thyroid cancer and breast cancer. The risks of bladder cancer were also increased in both male and female patients.