Transmission electron microscopic and immunohistochemical observations of resting follicles of feathers in chicken show massive cell degeneration
The molting cycle of feathers includes an anagen (growth) stage, a likely catagen stage where the feather follicles degenerate, and a resting stage where fully grown feathers remain in their follicles and are functional before molting. However, the cytological changes involved in the resting and molting stages are poorly known, so the results of an ultrastructural analysis of these processes in adult chick feathers are presented here. The study showed that the dermal papilla shrinks, and numerous cells present increased heterochromatin and free collagen fibrils in the extracellular matrix. Degeneration of the germinal epithelium of the follicle—the papillary collar—occurs with an initial substantial contraction of cells followed by an increase in heterochromatin, vesicle and lipid accumulation, and membrane and organelle degeneration. Desmosomes are still present between degenerating epithelial cells, but ribosomes and tonofilaments disappear. This suggests that cell necrosis initially proceeds as a major contraction resembling apoptosis—a process termed necroptosis, which was previously also shown to occur during the formation of barbs and barbules in mature down and pennaceous feathers. This study suggests that, aside from apoptosis, the collar epithelium degenerates due to external factors, in particular the retraction of blood vessels supplying the dermal papilla. In contrast, revascularization of the dermal papilla triggers a new phase of feather growth (anagen).
KeywordsChick Feather Follicle Dermal papilla Regression Ultrastructure
This research, in particular the entire electron microscopy study, was self-supported (Comparative Histolab).
Compliance with ethical standards
Conflict of interest
I declare no conflict of interest in relation to the present manuscript.
- Alibardi L (2004) Dermo–epidermal interactions in reptilian scales: speculations on the evolution of scales, feathers and hairs. J Exp Zool 302B:365–383Google Scholar
- Alibardi L (2005a) Cell structure of developing barbs and barbules in downfeathers of the chick: central role of barb ridge morphogenesis for the evolution of feathers. J Subm Cytol Pathol 37:19–41Google Scholar
- Alibardi L (2005b) Fine structure of juvenile feathers of the zebrafinch in relation to the evolution and diversification of pennaceous feathers. J Subm Cytol Pathol 37:323–343Google Scholar
- Alibardi L (2008) Follicular patterns during feather morphogenesis in relation to the formation of asymmetric feathers, filoplumes and bristles Ital. J Zool 76:279–290Google Scholar
- Alibardi L (2009a) Molding and carving cell surfaces: the joke of a fold and the origin and evolution of feathers. In: Gorb S (ed) Surface biology, vol 9. Springer, Berlin, pp 163–176Google Scholar
- Alibardi L (2010) Ultrastructure of cells of the dermal papilla in pennaceous feathers. Trends Dev Biol 5:51–60Google Scholar
- Demarchez M, Mauger A, Sengel P (1981) The dermal-epidermal junction during the development of the skin and cutaneous appendages in the chick embryo. Arch Anat Microsc Morphol Experim 70:206–218Google Scholar
- Li A, Figueroa S, Jiang TX, Wu P, Widelitz R, Nie Q, Chuong CM (2017) Diverse feather shape evolution enabled by coupling anisotropic signaling modules with self-organizing branching programme. Nat Commun 8:ncomms14139. https://doi.org/10.1038/ncomms14139
- Lucas AM, Stettenheim PR (1972) Growth of follicles and feathers. Color of feathers and integument. Avian anatomy. Integument. Agriculture Handbook 362, 7th edn. US Department of Agriculture, Washington, DC, pp 341–419Google Scholar
- Roth SI (1965) The cytology of the murine resting (telogen) hair follicle. In: Lyne AG, Short BF (eds) Biology of the skin and hair growth. Angus and Robertson Pbl, Sydney, pp 233–250Google Scholar
- Sengel P (1975) Morphogenesis of skin. Cambridge University Press, CambridgeGoogle Scholar
- Spearman RIC, Hardy JA (1985) Integument. In: King AS, McLelland J (eds) Form and function of birds, vol 3. Academic, London, pp 1–56Google Scholar
- Stenn KS, Paus R (2001) Controls of hair follicle cycling. Phys Rev 81:449–494Google Scholar