Investigation of characteristics of feather follicle stem cells and their regeneration potential

Development and Maintenance of Epidermal Stem Cells in Skin Adnexa

The skin surface is modified by numerous appendages. These structures arise from epithelial stem cells (SCs) through the induction of epidermal placodes as a result of local signalling interplay with mesenchymal cells based on the Wnt–(Dkk4)–Eda–Shh cascade. Slight modifications of the cascade, with the participation of antagonistic signalling, decide whether multipotent epidermal SCs develop in interfollicular epidermis, scales, hair/feather follicles, nails or skin glands. This review describes the roles of epidermal SCs in the development of skin adnexa and interfollicular epidermis, as well as their maintenance. Each skin structure arises from distinct pools of epidermal SCs that are harboured in specific but different niches that control SC behaviour. Such relationships explain differences in marker and gene expression patterns between particular SC subsets. The activity of well-compartmentalized epidermal SCs is orchestrated with that of other skin cells not only along the hair cycle but also in the course of skin regeneration following injury. This review highlights several membrane markers, cytoplasmic proteins and transcription factors associated with epidermal SCs.

Methionine improves feather follicle development in chick embryos by activating Wnt/β-catenin signaling

This study was conducted to explore the regulatory role of methionine (Met) in feather follicle and feather development during the embryonic period of chicks. A total of 280 fertile eggs (40 eggs/group) were injected with 0, 5, 10, 20 mg of L-Met or DL-Met/per egg on embryonic day 9 (E9), and whole-body feather and skin tissues were collected on E15 and the day of hatching (DOH). The whole-body feather weight was determined to describe the feather growth, and the skin samples were subjected to hematoxylin and eosin staining and Western blotting for the evaluation of feather follicle development and the expressions of Wingless/Int (Wnt)/β-catenin signaling pathway proteins, respectively. The results showed that L- or DL-Met did not affect the embryo weight (P > 0.05), but increased the absolute and relative whole-body feather weights. Specifically, 5 and 10 mg of L-Met and 5, 10, and 20 mg of DL-Met significantly increased the absolute feather weight at E15 (P < 0.05), and 10 mg of L-Met and 5 and 10 mg of DL-Met significantly increased the absolute and relative feather weight on the DOH (P < 0.05). Moreover, a main effect analysis suggested that changes in the embryo and feather weights were related to the Met levels (P < 0.05) but not the Met source (P > 0.05). The levels of L- and DL-Met were quadratically correlated with the absolute and relative feather weights of chicks on the DOH (P < 0.05). Correspondingly, all doses of L- and DL-Met significantly increased the diameter and density of feather follicles on the DOH (P < 0.05), as well as the activity of Wnt/β-catenin on E15 and the DOH (P < 0.05). In conclusion, injection of either L- or DL-Met can improve feather follicle development by activating Wnt/β-catenin signaling, and thereby promoting feather growth; furthermore, no difference in feather growth was found between L- and DL-Met treatments. Our findings might provide a nutritional intervention for regulating feather growth in poultry production.

Technical note: Induction of pluripotent stem cell-like cells from chicken feather follicle cells

Pluripotent stem cells including embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) are regarded as representative tools for conservation of animal genetic resources. Although ESC have been established from chicken, it is very difficult to obtain enough embryos for isolation of stem cells for avian conservation in most wild birds. Therefore, the high feasibility of obtaining the pluripotent cell is most important in avian conservation studies. In this study, we generated induced pluripotent stem cell-like cells (iPSLC) from avian Feather Follicular cells (FFC). Avian FFC are one of the most easily accessible cell sources in most avian species, and their reprogramming into pluripotent stem cells can be an alternative system for preservation of avian species. Intriguingly, FFC had mesenchymal stromal cells (MSC)-like characteristics with regard to gene expression, protein expression, and adipocyte differentiation. Subsequently, we attempted to generate iPSLC from FFC using retroviral vectors. The FFC-iPSLC can proliferate with the stem pluripotent property and differentiate into several types of cells in vitro. Our results suggest that chicken FFC are an alternative cell source for avian cell reprogramming into pluripotent stem cells. This experimental strategy should be useful for conservation and restoration of endangered or high-value avian species without sacrificing embryos.