In vitro methodology, hormonal and nutritional effects and fibre production in isolated ovine and caprine anagen hair follicles

Abstract

Mammalian hair follicles are complex multicellular structures in the skin, which produce hair fibre under the influence of locally produced and systemic signalling systems. Investigation to determine mechanisms of regulation, follicular responses and the importance of nutritional supply have utilised a number of in vivo and in vitro approaches. Included in these are studies on isolated intact anagen secondary follicles singly or in groups with incubation in culture medium. These utilise techniques developed for investigation of follicles from human skin. Results from selected studies reviewed here demonstrate differences in capacity for hair growth and protein synthesis between secondary follicles from Angora and cashmere-bearing goats. Mohair follicles were shown to exhibit faster hair shaft elongation both in vivo and in vitro, to have greater DNA content per follicle and to deposit significantly more protein per follicle and per unit of DNA. Incubation of anagen mohair and cashmere follicles in the presence of melatonin or prolactin showed positive responses in hair shaft growth and protein synthesis to both signalling molecules. This result indicated directly acting effects on the follicle in addition to any indirect effects arising at a whole animal level in response to, for example, variation in photoperiod. Similarly, epidermal growth factor was shown to alter elongation and protein synthesis in mohair follicles and to produce, at higher concentration, club hair structures similar to effects observed in other species. The vitamin biotin was shown to be important in maintaining viability of isolated sheep secondary hair follicles where supplementation increased the proportion continuing to grow. Effects on growth and apparent protein synthesis suggested comparatively lesser effects on follicles, which remained viable. Histology on follicles indicated effects of biotin deficiency in reducing proliferation of basal keratinocytes. The final study, included in this review, demonstrated that supply of the essential sulphur-containing amino acid L-methionine was necessary to maintain the viability and growth of mohair follicles. L-cysteine was not required in the presence of L-methionine, although there was evidence of an optimisation when both amino acids were present in adequate concentrations. Consideration is given to the importance of transport mechanisms and capacity to utilise absorbed nutrients when considering optimising nutritional supply to individual follicles. These may then provide targets for attainment in applied nutrition of animals in vivo.Keywords: hair follicle, in vitro culture, cashmere, mohair, sheep wool ImplicationsHair fibres are products with value depending on quality and quantity produced. We require information to optimise breeding and husbandry of fibre-producing animals. This includes better understanding of the hair follicles in skin, which produce fibre. This report reviews results from in vitro studies on follicles removed from skin of sheep and goats. It describes how: (i) var...

Fundamental hair follicle biology and fine fibre production in animals

“…Craven et al (2006) have identified, in skin and hair follicles of transgenic mice, local production of prolactin which is considered to interact with that present systemically. The addition of prolactin (200 mg/l) to culture medium been shown to stimulate both hair shaft elongation and protein synthesis in isolated cashmere and mohair anagen hair follicles (Galbraith, 2010). However, downstream effects of prolactin and potential interaction with, for example, paracrine regulators and pathways appear not to have been described.…”

“…The disparity between the concentrations of cysteine in hair fibre and that in sulphur amino acid supply are factors in the relatively low value (0.3) relating conversion of metabolisable protein to hair follicle protein in animals such as sheep (Agricultural and Food Research Council (AFRC), 1993). Additional factors of importance are transport in blood and uptake into follicles by mechanisms which are now becoming understood in integumental tissues including the hair follicle (Thomas et al, 2007;Hepburn et al, 2008;Galbraith, 2010). Post-absorptive utilisation depends on supply at the follicle level and synthetic activities of structures (particularly medulla: cortex, cuticle and IRS) according to position in the follicular cycle.…”

“…Deficiency symptoms have been described for inadequacy of vitamin supply, which relate to generally well-understood roles in cell biochemistry. These include ribloflavin, niacin, pantothenic acid, folic acid and biotin (general effects on integumental tissues including caprine and sheep hair follicles (Tahmasbi et al, 2007a and2007b;Galbraith 2010)), vitamin A and retinoids, which are essential for cell proliferation and vitamin D that influences TGF b2 upregulation and follicle development (Inoue et al, 2009). Important cations include calcium that provides signal transduction in keratinocytes (Pruche et al, 1996) and magnesium, which has a role in energy-providing phosphate transfer reactions and DNA degradation and synthesis.…”

Relationships between integumental characteristics and thermoregulation in South American camelids

“…During moult, the hair number, diameter or growth intensity are modified (Galbraith, 2010b). While wild lamoids (guanaco, vicuñ a) are reported to shed annually (Fowler, 1998), adult male llamas kept under natural light and ambient conditions in Scotland have been reported as shedding only partially, with 30% to 50% of the fibres being shed over an extended period (Russel and Redden, 1994).…”

Animal fibre: connecting science and production

“…The application of in vitro methodology, developed from studies on human HFs, to investigation of the regulation of fibre growth in small ruminants is the subject of the paper by Galbraith (2010a). This approach enables measurement of intrinsic growth and physiological/metabolic behaviour of individual, or groups of, isolated anagen HFs in culture media.…”