Human dermal papilla (DP) cells grown in twodimensional (2D) culture have been studied extensively. However, key differences exist between DP cell activities in vivo and in vitro. Using a suspension method of cell culture to maintain DP cells, we created three-dimensional (3D) dermal spheres morphologically akin to intact (anagen) DPs. Analysis of these spheres using immunocytochemistry demonstrates that they have expression profiles different from papilla cells cultured in 2D but with many similarities to intact DPs. This method of DP cell culture may provide us with a tool to elucidate our understanding of signalling within the DP as it relates to induction, maintenance or even inhibition of hair growth.

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An increase in NK1+ and CD16+ cells in combination with complement activation indicates that an irritant non-immunogenic stimulation of the immune system is important. The result with the interleukins showed both an increase in the production of inflammatory interleukins as well as in the regulatory interleukins for both TH1 and TH2 cells. Similarities to the immune response described for Candida albicans infections indicate the role of Malassezia in the skin response in seborrhoeic dermatitis and Pityrosporum folliculitis.

Differentiation within the nail unit was examined using a range of antikeratin monoclonal antibodies including the recently described antibody LHTric-1, specific to the acidic hair-type keratin Ha1. Keratinocytes of the nail matrix, nail bed and the digit pulp were characterized by different patterns of keratin expression. Nail matrix was the sole site of expression of Ha1, which colocalized in suprabasal matrix epidermis with epidermal keratins K1 and K10. Small amounts of K17 were found at the apex of the matrix in some cases. K6 and K16 were found where the epidermal surface folds forwards to become the ventral aspect of the proximal nail fold. The nail bed was distinguished by the absence of hair-type keratin Ha1 and the absence of markers of cornified epidermis and mucosal differentiation K1/K10 and K4/K13, respectively, while K6, K16 and K17 were detected. The basal keratin conformation marker, LH6, was expressed suprabasally throughout the nail bed. This complement of keratins exists in the nail bed in the absence of notable proliferative activity, and suggests a state of minimally developed differentiation which may be afforded by the physical or biological properties of the overlying nail. Keratins, K6, K16 and K17 were all found in the digit pulp in limited amounts, possibly in association with the epidermal component of the eccrine duct. The simple epithelial keratins, K7, K8 and K18, were found in small amounts in the specimens from younger individuals, mainly in epibasal cells of the apex of the matrix and in putative Merkel cells.

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The hair follicle has the unique capacity to undergo periods of growth, regression, and rest before regenerating itself to restart the cycle. This dynamic cycling capacity enables mammals to change their coats, and for hair length to be controlled on different body sites. More recently, the process of club fiber shedding has been described as a distinct cycle phase known as exogen, and proposed to be an active phase of the hair cycle. This review focuses on the importance of the shedding phase of the hair cycle and, in the context of current literature, analyzes the processes of club fiber formation, retention, and release, which may influence progression through exogen, particularly in relation to human hair.

SynopsisHair diversity, its style, colour, shape and growth pattern is one of our most defining characteristics. The natural versus temporary style is influenced by what happens to our hair during our lifetime, such as genetic hair loss, sudden hair shedding, greying and pathological hair loss in the various forms of alopecia because of genetics, illness or medication. Despite the size and global value of the hair care market, our knowledge of what controls the innate and within-lifetime characteristics of hair diversity remains poorly understood. In the last decade, drivers of knowledge have moved into the arena of genetics where hair traits are obvious and measurable and genetic polymorphisms are being found that raise valuable questions about the biology of hair growth. The recent discovery that the gene for trichohyalin contributes to hair shape comes as no surprise to the hair biologists who have believed for 100 years that hair shape is linked to the structure and function of the inner root sheath. Further conundrums awaiting elucidation include the polymorphisms in the androgen receptor (AR) described in male pattern alopecia whose location on the X chromosome places this genetic contributor into the female line. The genetics of female hair loss is less clear with polymorphisms in the AR not associated with female pattern hair loss. Lifestyle choices are also implicated in hair diversity. Greying, which also has a strong genetic component, is often suggested to have a lifestyle (stress) influence and hair follicle melanocytes show declining antioxidant protection with age and lowered resistance to stress. It is likely that hair research will undergo a renaissance on the back of the rising information from genetic studies as well as the latest contributions from the field of epigenetics. R esum eLa diversit e des cheveux, leur style, leur couleur, leur forme et leur courbe de croissance sont parmi les caract eristiques qui nous d eterminent les plus. Le style naturel compar e au style temporaire est influenc e par ce qui arrive a nos cheveux au cours de notre vie, comme la perte g en etique de cheveux, perte soudainede cheveux, le vieillissement et la perte pathologiquede cheveux dans les diff erentes formes d'alop ecie due a la g en etique, la maladie ou des m edicaments. En d epit de la taille et de la valeur globale du march e des soins capillaires, notre connaissance de ce qui contrôle les caract eristiques inn ees et exog ene de la diversit e des cheveux reste limit ee. Dans la derni ere d ecennie, la recherches'est concentr ee dans le domaine de la g en etique o u les caract eristiques des cheveux sont evidentes et mesurables et les polymorphismes g en etiques sont trouv es qui soul event des questions int eressantes sur la biologie de la croissance des cheveux. La r ecente d ecouverte que le g ene de la trichohyaline contribue a la forme des cheveux n'est pas une surprise pour les biologistes du cheveux qui ont cru pendant 100 ans que la forme des cheveux est li ee a la structure et la fonction de l...

Hair fibres show wide diversity across and within all human populations, suggesting that hair fibre form and colour have been subject to much adaptive pressure over thousands of years. All human hair fibres typically have the same basic structure.However, the three-dimensional shape of the entire fibre varies considerably depending on ethnicity and geography, with examples from very straight hair with no rotational turn about the long axis, to the tightly sprung coils of African races. The creation of the highly complex biomaterials in hair follicle and how these confer mechanical functions on the fibre so formed is a topic that remains relatively unexplained thus far.We review the current understanding on how hair fibres are formed into a nonlinear coiled form and which genetic and biological factors are thought to be responsible for hair shape. We report on a new GWAS comparing low and high curl individuals in South Africa, revealing strong links to polymorphic variation in trichohyalin, a copper transporter protein CUTC and the inner root sheath component keratin 74. This builds onto the growing knowledge base describing the control of curly hair formation. K E Y W O R D Scurl, hair follicle, hair trait genetics, human hair | INTRODUCTIONThe basic structure of hair-a cuticle, cortex and medulla (in some)-does not reveal how these structures are built by the hair follicle or shaped into the curly fibre, suggesting there is a level of "fine control" on the process of hair fibre formation by the hair follicle.The distribution of forms of curly hair is shown in Figure 1 and a closer inspection reveals that curly hair fibres are rarely a true coil but exhibit heterogeneity in the direction of the curl in all but the mildest cases. Curly hairs have an elliptical or "D" shape in cross section.This enables bidirectional bending stiffness, bending most easily in the direction of the flattened axis. The relationship of the long and short diameter to the direction of hair growth also changes (unlike the eyelash where this relationship is maintained [1] ). Therefore, we need to understand how the arrangement of cells results in a fibre that is elliptical with the orientation of the ellipse changing with time during hair growth to form a coil.Hair fibres across all races and geographies show degrees of curl that are readily measurable.[2-4] Both Hrdy and de la Mettrie [2,5] studied various hair types sampled from countries and cultures across the world. The degree of curvature of a fibre in its natural state appears to account for most of the variation (87% [5] ), which is as expected. The presence of a medulla is chiefly correlated with hair diameter. The major curl forms are "twist" (with irregular natural constrictions in the fibre producing a discontinuity in curvature), "crimp" (change in direction of curvature), "wave" (number of oscillations/coils per unit length) and "kink" (sharp twist or bend).Hrdy 1973 [2] showed that kinking and crimp were not always correlated with curvature and irregular curvature ca...