The Histology of Keratin Fibers

Swift, J. A.

doi:10.1007/978-1-4613-4109-3_3

Cited by 46 publications

(25 citation statements)

References 178 publications

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“…AFM enables high-resolution images to be recorded without the ultrathin sectioning or staining required for transmission electron microscopy (TEM) (Figs. S2 and S3), which already revealed profound changes in the IF network (29,30). The topographic images were obtained using the peak force quantitative nanomechanical mapping (QNM) mode of the AFM on dried follicles that retain the fibernetwork architecture (Fig.…”

Section: Resultsmentioning

confidence: 99%

Keratin network modifications lead to the mechanical stiffening of the hair follicle fiber

Bornschlögl

Bildstein

Thibaut

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The complex mechanical properties of biomaterials such as hair, horn, skin, or bone are determined by the architecture of the underlying fibrous bionetworks. Although much is known about the influence of the cytoskeleton on the mechanics of isolated cells, this has been less studied in tridimensional tissues. We used the hair follicle as a model to link changes in the keratin network composition and architecture to the mechanical properties of the nascent hair. We show using atomic force microscopy that the soft keratinocyte matrix at the base of the follicle stiffens by a factor of ∼360, from 30 kPa to 11 MPa along the first millimeter of the follicle. The early mechanical stiffening is concomitant to an increase in diameter of the keratin macrofibrils, their continuous compaction, and increasingly parallel orientation. The related stiffening of the material follows a power law, typical of the mechanics of nonthermal bending-dominated fiber networks. In addition, we used X-ray diffraction to monitor changes in the (supra)molecular organization within the keratin fibers. At later keratinization stages, the inner mechanical properties of the macrofibrils dominate the stiffening due to the progressive setting up of the cystine network. Our findings corroborate existing models on the sequence of biological and structural events during hair keratinization.atomic force microscopy | elastic modulus | human hair follicle | biomechanics | X-ray diffraction B iological tissues are structurally complex materials with remarkable mechanics and elastic moduli that can range from a few pascals to several gigapascals (1-3). An active field aims at understanding how the local structural and mechanical properties of bionetworks define its macroscopic mechanics from a molecular scale toward a cellular and tissue scale (4-6). One challenge is that the properties of these networks have to be considered over multiple length and force scales with macroscopic mechanical forces being transduced from the whole tissue scale down to the cellular and molecular level and vice versa.At the cellular level, the last decades witnessed for a considerable advancement toward a better understanding of how the cytoskeleton composed of actin, microtubules, and intermediate filaments (IFs) determines cellular mechanics (1,(6)(7)(8). In vitro studies on isolated cells (6) and reconstituted in vitro bionetworks with controllable architecture and composition (9-12) considerably advanced our knowledge of cytoskeletal mechanics. However, these models are only approximations of the complex tridimensional architecture of most tissues. At the tissue level, the mechanical anisotropy together with the variety of mechanically different constituents usually hamper direct correlations between network architecture and mechanical properties (3, 13). Analytical models and computer modeling allow to theoretically link the macroscopic mechanical properties of the network with parameters of the local network architecture (5, 14, 15).The human hair follicle was used here...

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Section: Resultsmentioning

confidence: 99%

Keratin network modifications lead to the mechanical stiffening of the hair follicle fiber

Bornschlögl

Bildstein

Thibaut

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The common morphology of the differentiated cuticle cell can be divided into three main layers on the basis of half-cystine content, namely the A layer and exocuticle which are cystine-rich and the endocuticle which is relatively cystine-poor (Bradbury 1973;Swift and Bews 1976;Swift 1977Swift , 1981. There is also evidence for a thin cystine-rich layer on the inner, cortical side of the cell (Swift 1967;Fraser et al 1972).…”

Section: Cuticle Keratin Synthesismentioning

confidence: 91%

“…Their observations also suggest that the thin cystine-rich layer apposing the cortex is derived from the first peripheral deposition of granules and therefore it would have the same composition as that region of the A layer. Microfibrils typical of the cortex are not found in the cuticlc (Bradbury 1973;Swift 1977), although a loose filamentous network is discernible (Happey and Johnson 1962;Roth and Helwig 1964;Woods and Orwin 1980) and appears to be associated with the granules and their ordered deposition. During keratinization the granules first fuse and are then transformed into lamellar networks (Woods and Orwin 1980).…”

Section: Cuticle Keratin Synthesismentioning

confidence: 94%

“…The endocuticle appears to be the result of the condensation and dehydration of the cytoplasmic contents of the cell as it keratinizes. Ristochemical methods applied at the electron microscopic level indicate that the proteins of the A layer and exocuticle are sulphur-rich (Swift 1967(Swift , 1977. This has been supported by chemical studies of enriched cuticle cell preparations obtained by the selective release of cuticle cells from wool fibres by mechanical agitation in various solvents and subsequent centrifugation (Knott et al 1980;Ley and Crewther 1980).…”

Section: Proteins Of the Cuticlementioning

confidence: 95%

“…The fibre cuticle, composed of a uniform cell type of flattened appearance, varies in thickness from the single cell layer of wool to six layers in human hair and up to 35layers in pig bristl (Bradbury 1973;Swift 1977). The common morphology of the differentiated cuticle cell can be divided into three main layers on the basis of half-cystine content, namely the A layer and exocuticle which are cystine-rich and the endocuticle which is relatively cystine-poor (Bradbury 1973;Swift and Bews 1976;Swift 1977Swift , 1981.…”

Section: Cuticle Keratin Synthesismentioning

confidence: 99%

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