Transgenic Flash Mice for In Vivo Quantitative Monitoring of Canonical Wnt Signaling to Track Hair Follicle Cycle Dynamics

Abstract

Hair follicles (HFs) upon development enter a lifelong cycle of growth, regression, and resting. These phases have been extensively studied at the cellular and molecular levels for individual HFs. However, HFs group into domains with coordinated cycling strongly influenced by their environment. These macroscopic hair domains have been difficult to study and can be influenced by physiological or pathological conditions, such as pregnancy or skin wounds. To robustly address this issue, we generated a mouse model for quantitative monitoring of β-catenin activity reflecting HF cycle dynamics macroscopically by using live bioluminescence imaging. These mice allowed live tracking of HF cycles and development, and highlighted hair regenerative patterns known to occur through macro-environmental cues, including initiation events, propagating anagen and border stability, and allowed refinement of a mechanistic mathematical model that integrates epidermal cell population dynamics into an excitable reaction-diffusion model. HF cycling could be studied in situations of pregnancy, wound healing, hair plucking, as well as in response to cyclosporine or Wnt3a stimulation. In conclusion, we developed a model for analysis of HF cycling at the macroscopic level that will allow refined analysis of hair cycle kinetics as well as its propagation dynamics.

The Hair Follicle

“…This is in sharp contrast to the findings in the human scalp, where pregnancy results in an increased proportion of anagen HFs. The simultaneous entry of these anagen HFs into telogen during the postpartum period then results in increased hair loss and sometimes even in alopecia (Hodgson et al 2014;Gizlenti and Ekmekci 2014).…”

“…Hair loss (hypotrichosis or alopecia) is a common problem, and it is known that hair loss affects approximately 60 million men, women, and children in the United States, and the costs for medical consults and treatment sum up to US$1.3 billion per year (Hodgson et al 2014). …”

Mesenchymal-epidermal interactions in hair follicle cycling and regeneration

“…We collected samples of skin at various stages of hair follicle development between E14.5 and P24. Postnatal hair follicle phase was determined in vivo using Topflash β-catenin reporter mice developed in our laboratory, and confirmed histologically using criteria described in a previous study (Hodgson et al, 2014;Paus et al, 1999). The presence of P-STAT5 in the DP could only be detected from the first catagen phase at P19 and was most prominent during the first telogen phase at P24.…”

“…For adult skin samples, hair follicle phase was determined using luminescence as previously described (Hodgson et al, 2014). Briefly, mice were injected intraperitoneally with 150mg/kg firefly D-luciferin (Regis Technologies, IL, USA) and imaged using the Xenogen IVIS Spectrum live animal imaging system (Perkin Elmer, MA, USA).…”

“…Samples of embryonic mouse back skin at E14.5, E16.5 and E18.5 were collected from time-mated C57BL/6J mice. Postnatal skin was collected from Topflash reporter mice developed in our laboratory as previously described (Hodgson et al, 2014).…”