The Thermodynamics of Trichocyte Keratins

Learning from hair moisture sorption and hysteresis

OBJECTIVE

The process of moisture sorption and desorption by human hair was analysed for extracting hints on the hair structure.

METHODS

The isotherms of moisture sorption and desorption by hair were recorded for untreated and chemically treated (permed and bleached) hair. Data of swelling were also considered.

RESULTS

By examining the swelling and moisture sorption of keratin fibres, it is possible to conclude that hysteresis is quite improbably caused by capillary condensation. The mobility of the protein chains and the strength of the bonds binding water molecules to the active sites inside the matrix are proposed as causes instead. The concept of "breaking symmetry", derived from moisture sorption-desorption data, and the method of evaluating this parameter, is proposed as a way of characterizing the chemical treatment of hair. The results show that bleaching produces a larger breaking of symmetry than perming, and this is suggested to be due to new hydrogen bonds, created as a result of the chemical treatment, replacing the original disulfide bonds, which are of different strength compared to the bonds of untreated hair. The quantitative sorption data matched well to the model of grains of matrix enveloped in layers of water molecules at increasing relative humidity, up to 100 %. The analysis suggested that, aside from the glass transition event occurring at around 60-70 % relative humidity, there is another, less examined, transition occurring at around 30 % relative humidity, assigned to the opening of the hair inner structure, and accommodation of more water molecules. Both transitions are reflected by corresponding changes in the fibre mechanical behaviour.

CONCLUSION

The moisture sorption-desorption by hair was shown not only to allow a quantitative differentiation among various cosmetic treatments of the hair, but also to provide valuable information on the structure of the fibre.

Kinesin family member 23 exerts a protumor function in breast cancer via stimulation of the Wnt/β-catenin pathway

Kinesin family member 23 (KIF23) has been described as one of the main genes that are associated with malignant transformation in numerous cancers. However, the exact significance of KIF23 in breast cancer has not been well-addressed. The present study was dedicated to the comprehensive investigation of KIF23 in breast cancer. Initial expression analysis through The Cancer Genome Atlas (TCGA) demonstrated high KIF23 levels in breast cancer compared with normal controls. These in silico data showing high levels of KIF23 in breast cancer were verified by assessing clinical specimens using real-time quantitative PCR and immunoblot assays. Moreover, a high KIF23 level was correlated with adverse clinical outcomes in breast cancer patients. Cellular functional experiments showed that the down-regulation of KIF23 affected the malignant behaviors of breast cancer cells in vitro, whereas the forced expression of KIF23 stimulated them. Mechanistic studies revealed that KIF23 restraint down-regulated the levels of phosphorylated glycogen synthetase kinase-3β (GSK-3β), β-catenin, cyclin D1 and c-myc in breast cancer cells, showing an inhibitory effect on the Wnt/β-catenin pathway. The suppression of GSK-3β was able to reverse KIF23-silencing-induced inactivation of the Wnt/β-catenin pathway. Inhibition of the Wnt/β-catenin pathway abolished KIF23 overexpression-mediated protumor effects in breast cancer. A xenograft assay confirmed the in vivo antitumor function of KIF23 inhibition. In conclusion, these findings suggest that KIF23 may exert a protumor function in breast cancer by stimulating the Wnt/β-catenin pathway. This work suggests that KIF23 has potential values for targeted therapy and prognosis in breast cancer.

Wool fiber curvature is correlated with abundance of K38 and specific keratin-associated proteins

Curvature in mammalian fibers, such as wool and human hair, is an important feature of the functional trait of coat structure-it affects mechanical resilience and thermo-insulation. However, to examine the relationship between fiber curvature, ultrastructure and protein composition fiber diameter variability has to be minimal. To achieve this we utilised the progeny of straight-wool domestic sheep mutant rams (crimp mutants) and wild-type ewes. Proteomic and structural results of the resulting mutant/wild-type twin pairs confirmed that straight crimp mutant wool had a normal cuticle and the same cortical protein and ultrastructural building blocks as wild-type (crimpy) fibers but differed in the layout of its cortical cells and in the relative proportions of keratin (K) and keratin-associated proteins (KAPs). In the case of the crimp mutants (straight fibers), the orthocortex was distributed in a fragmented, annular ring, with some orthocortical cells near the central medulla, a pattern similar to that of straight hairs from humans and other mammals. Crimp mutant fibers were noted for the reduced abundance of some proteins in the high glycine-tyrosine class normally associated with the orthocortex, specifically the KAP6, KAP7, and KAP8 families, while proteins from the KAP16 and KAP19 were found in increased abundance. In addition to this, the type I keratin, K38, which is also associated with the orthocortex, was also found at lower abundance in the mutant fibers. Conversely, proteins from the ultra-high sulfur class normally associated with the paracortex, specifically the KAP4 and KAP9 families, were found in higher abundance.

Processing hair follicles for transmission electron microscopy

Transmission electron microscopy (TEM) has greatly advanced our knowledge of hair growth and follicle morphogenesis, but complex preparations such as fixation, dehydration and embedding compromise ultrastructure. While recent developments with cryofixation have been shown to preserve the ultrastructure of biological materials close to native state, they do have limitations. This review will focus on each stage of the TEM sample preparation process and their effects on the structural integrity of follicles.