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Intrinsic curvature in wool fibres is determined by differential lengths of two populations of cortex cells

journal contribution
posted on 2023-05-03, 15:05 authored by Duane HarlandDuane Harland, James Vernon, Joy Woods, Shinobu Nagase, Takashi Itou, Kenzo Koike, David Scobie, Anita Grosvenor, Jolon Dyer, Stefan ClerensStefan Clerens
Hair curvature underpins structural diversity and function in mammalian coats, but what causes curl in keratin hair fibres? To obtain structural data to determine one aspect of this question, we used confocal microscopy to provide in situ measurements of the two cell types that make up the cortex of merino wool fibres, which was chosen as a well-characterised model system representative of narrow diameter hairs, such as underhairs. We measured orthocortical and paracortical cross-sectional areas, and cortical cell lengths, within individual fibre snippets of defined uniplanar curvature. This allowed a direct test of two long-standing theories of the mechanism of curvature in hairs. We found evidence contradicting the theory that curvature results from there being more cells on the side of the fibre closest to the outside, or convex edge, of curvature. In all cases, the orthocortical cells close to the outside of curvature were longer than paracortical cells close to the inside of the curvature, which supports the theory that curvature is underpinned by differences in cell type length. However, the latter theory also implies that, for all fibres, curvature should correlate with the proportions of orthocortical and paracortical cells, and we found no evidence for this. In merino wool, it appears that the absolute length of cells of each type and proportion of cells varies from fibre to fibre, and only the difference between the length of the two cell types is important. Implications for curvature in higher diameter hairs, such as guard hairs and those on the human scalp, are discussed.


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© 2018. Published by The Company of Biologists Ltd


  • English

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The Company of Biologists

Journal title

Journal of Experimental Biology




Harland, D. P., Vernon, J. A., Woods, J. L., Nagase, S., Itou, T., Koike, K., Scobie, D. A., Grosvenor, A. J., Dyer, J. M., & Clerens, S. (2018). Intrinsic curvature in wool fibres is determined by differential lengths of two populations of cortex cells. Journal of Experimental Biology, 221(6), jeb172312. doi:10.1242/jeb.172312

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