In vivo formation steps of the hard α-keratin intermediate filament along a hair follicle: Evidence for structural polymorphism

Er-Rafik, Mériem; Briki, Fatma; Burghammer, Manfred; Doucet, J.

doi:10.1016/j.jsb.2005.11.013

Cited by 23 publications

(19 citation statements)

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“…Those early disulfides should therefore mainly represent intra-IF disulfides (40), which contribute to the overall mechanical properties of the macrofibril. It is plausible that this intra-IF disulfide formation constitutes the driving force that leads to the maturation of the IFs in this area of the follicle (21,41). This picture is in agreement with recent work by Fraser and Parry (42), establishing that the maturation of the IFs in zone III should be accompanied by an alignment of intra-IF cysteine moieties to enable such crosslinks.…”

Section: Discussionsupporting

confidence: 90%

“…Together with cysteine-rich KAPs, this ensures a covalent cross-linking of the IFs (31). Evidence of a gradual constitution of this disulfide keratin-KAP network was shown by X-ray diffraction in the late hair follicle (21). These observations indicate that cysteine formation and final axial rearrangement together with drying of the structure leads to the final stiffening.…”

Section: Resultsmentioning

confidence: 81%

“…Our DTT reduction experiments show that a significant contribution of disulfide bonds to the overall network mechanics becomes visible already in zone II (Fig. 5F), whereas the matrix architecture there is far from being complete because most of the KAP/IF disulfide bonds are constituted much further up the follicle (in zone IV, 650 μm at earliest) (21). Those early disulfides should therefore mainly represent intra-IF disulfides (40), which contribute to the overall mechanical properties of the macrofibril.…”

Section: Discussionmentioning

confidence: 93%

“…During zones I and II, the IFs start forming a network of small macrofibrils that grow in diameter by lateral aggregation (Fig. 2 and 3B) (21,35,36). Also a gradual increase in volume fraction occupied by the macrofibrils occurs (Fig.…”

Section: Discussionmentioning

confidence: 98%

“…It is accompanied by multiple biological processes such as a specific expression of different keratins and keratin-associated proteins (KAPs) (19) that lead, together with the reorganization of the keratin network and the loss of water, to a compaction and hardening of the fiber. However, although several complementary studies analyzed the changes in the network architecture accompanying the keratinization process (20)(21)(22), little is known about the consequence, its mechanical hardening.…”

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confidence: 99%

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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: Discussionsupporting

confidence: 90%

Section: Resultsmentioning

confidence: 81%

Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 98%

mentioning

confidence: 99%

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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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Marine Keratins

Ehrlich

2014

Biological Materials of Marine Origin

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Keratins represent the largest subgroup among all intermediate fi lament proteins. These structural proteins are mechanically robust and chemically unreactive. This is due to tight packing of protein chains in the form of alpha-helices or β-sheets into supercoiled polypeptide chains crosslinked with disulphide bonds. This chapter is dedicated to keratins of marine fi sh, birds, reptilian and mammalian origin. Keratin-like biological materials from hagfi sh slime are also discussed.

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Development of Hair Fibres

Harland

Plowman

2018

Advances in Experimental Medicine and Biology

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The growth of hairs occurs during the anagen phase of the follicle cycle. Hair growth begins with basement membrane-bound stem cells (mother cells) around the dermal papilla neck which continuously bud off daughter cells which further divide as a transient amplifying population. Division ceases as cell line differentiation begins, which entails changes in cell junctions, cell shape and position, and cell-line specific cytoplasmic expression of keratin and trichohyalin. As the differentiating cells migrate up the bulb, nuclear function ceases in cortex, cuticle and inner root sheath (IRS) layers. Past the top of the bulb, cell shape/position changes cease, and there is a period of keratin and keratin-associated protein (KAP) synthesis in fibre cell lines, with increases, in particular of KAP species. A gradual keratinization process begins in the cortex at this point and then non-keratin cell components are increasingly broken down. Terminal cornification, or hardening, is associated with water loss and precipitation of keratin. In the upper follicle, the hair, now in its mature form, detaches from the IRS, which is then extracted of material and becomes fragmented to release the fibre. Finally, the sebaceous and sudoriferous (if present) glands coat the fibre in lipid-rich material and the fibre emerges from the skin. This chapter follows the origin of the hair growth in the lower bulb and traces the development of the various cell lines.

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In vivo formation steps of the hard α-keratin intermediate filament along a hair follicle: Evidence for structural polymorphism

Cited by 23 publications

References 58 publications

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

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

Marine Keratins

Development of Hair Fibres

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