Dissecting the Molecular Mechanism of Ionizing Radiation-Induced Tissue Damage in the Feather Follicle

Abstract

Ionizing radiation (IR) is a common therapeutic agent in cancer therapy. It damages normal tissue and causes side effects including dermatitis and mucositis. Here we use the feather follicle as a model to investigate the mechanism of IR-induced tissue damage, because any perturbation of feather growth will be clearly recorded in its regular yet complex morphology. We find that IR induces defects in feather formation in a dose-dependent manner. No abnormality was observed at 5 Gy. A transient, reversible perturbation of feather growth was induced at 10 Gy, leading to defects in the feather structure. This perturbation became irreversible at 20 Gy. Molecular and cellular analysis revealed P53 activation, DNA damage and repair, cell cycle arrest and apoptosis in the pathobiology. IR also induces patterning defects in feather formation, with disrupted branching morphogenesis. This perturbation is mediated by cytokine production and Stat1 activation, as manipulation of cytokine levels or ectopic Stat1 over-expression also led to irregular feather branching. Furthermore, AG-490, a chemical inhibitor of Stat1 signaling, can partially rescue IR-induced tissue damage. Our results suggest that the feather follicle could serve as a useful model to address the in vivo impact of the many mechanisms of IR-induced tissue damage.

Testing Chemotherapeutic Agents in the Feather Follicle Identifies a Selective Blockade of Cell Proliferation and a Key Role for Sonic Hedgehog Signaling in Chemotherapy-Induced Tissue Damage

“…In all cases, the rachis remained largely normal, whereas the branching barbs/barbules were reduced or disrupted in patterning, suggesting selective perturbation of the feather structure ( Figure 2b). In some cases, we noticed disrupted feather branching similar to those observed after ionizing radiation treatment ( Figure 2b and Supplementary Figure S1 online; Chen et al, 2014), suggesting an impact of cytokine signaling. Indeed, an increased expression of TNFa and IFNg in the feather follicles was noticed (Supplementary Figure S1 online).…”

“…Active feather growth was induced in 6-month-old adult chicken by plucking and regeneration (Chen et al, 2014). Adapting the established protocol of inducing complete alopecia in mice by CYP (Paus et al, 1994) G Xie et al…”

“…These defects can be graded into two subtypes (Chen et al, 2014). Grade I defects take a linear shape (Figure 1d): the feather barbs persist without barbules attached in short intervals.…”

“…All experimental protocols were approved by Fuzhou University Experimental Animal Ethics Board. Active feather growth was induced by a plucking-regeneration protocol (Chen et al, 2014), and active hair growth was induced as described previously (Paus et al, 1994). The doses used were as follows: CYP (Sigma, Shanghai, China) 150 mg kg À 1 , Ara-C (Sigma) 50mgkg À 1 , Doxorubicin (BBI, Shanghai, China) 10 mg kg À 1 , 5-FU (Meryer, Shanghai, China) 150 mg kg À 1 , and Taxol (BBI) 100 mg kg À 1 .…”

“…Histology, immunostaining, and TUNEL staining HE staining, immunostaining, TUNEL staining, and in situ hybridizations were processed as described (Chen et al, 2014). Briefly, feather follicles were fixed by 4% paraformaldehyde at 4 1 C overnight and processed for paraffin section.…”