What’s new in hair — June 2016 | Dr. Claire A. Higgins
Inhibition of β-catenin signalling in dermal fibroblasts enhances hair follicle regeneration during wound healing.
Development. 2016 Jun 10. pii: dev.131797.
In mouse skin, hair follicle neogenesis in the centre of large wounds (>1.5cm) is a well-known phenomenon. The Cotsarelis group previously demonstrated that epidermal wnt signalling is required for this process. In this study, Rognoni et al assess hair follicle neogenesis in small wounds (2mm). They observe hair neogenesis in the skin of young mice (<p21), and find the ability of skin to form de novo follicles is lost with increasing age. Comparing skin dermis from young mice (with hair neogenesis capacity) and old mice (no hair neogenesis capacity) the authors uncovered a down regulation of many wnt associated genes with age. Comparatively, in response to wounding young skin dermis up-regulates a wnt inhibitor, Dkk1, while in old skin dermis Dkk1 was not expressed. The authors conclude that wnt inhibition after wounding, specifically in young skin, creates a permissive environment for hair neogenesis. This perhaps explains why de novo follicles are seen in young mouse skin, but not old mouse skin, following creation of small wounds.
Minoxidil topical treatment may be more efficient if applied on damp scalp in comparison with dry scalp.
Dermatol Ther. 2016 Jun 30. doi: 10.1111/dth.12369.
Minoxidil is approved for topical treatment of Androgenetic Alopecia. However, there is no consensus or guidelines for the mode of application; should the scalp be dry or wet? In this study, Angelo et al used ex vivo rat skin tied to a support to answer this question. After washing and drying the skin/hair to recreate either towel dried (wet) or blow dried (dry) samples, minoxidil was applied to the hair for 30-120 minutes, then rinsed off using water. The authors found significantly more minoxidil was taken up into the hair and skin of wet, towel dried skin compared to blow dried skin. This demonstrates that scalp hydration is a key factor in drug penetrance, and suggests that minoxidil should be applied on wet hair/scalp for maximal uptake and therefore effect.
JAAD Case Rep. 2016 May 26;2(3):212-5. doi: 10.1016/j.jdcr.2016.02.011. eCollection 2016 May.
Monilethrix is an autosomal dominant condition characterised by fragile moniliform hairs. The fragility of these hairs means the fibers break prematurely, giving the appearance of hair loss. In this case report two patients, a 35 year old woman, and a 40 year old woman, both of whom were diagnosed with Monilethrix, were both treated with oral minoxidil, 0.25mg or 0.5mg daily. Oral minoxidil was used rather than topical application, as this may have caused hair breakage during application. Six months after the start of treatment, both patients had a significant improvement in their hair density, and less hair shedding/breakage. It is not known how minoxidil acts on the follicle in Monilethrix, but it is likely that the resultant increased diameter of the hair shaft confers some structural stability to the fiber, meaning there is less breakage.
FEBS J. 2016 Jun 17. doi: 10.1111/febs.13784.
CD133, or Prominin-1, is expressed in a small percentage of dermal papilla cells and is known to be a marker of hair follicle inductivity. In this paper, Zhou et al grow CD133+ve dermal papilla cells in spheroids within hydrogels, to try and determine how papilla cells signal to and interact with adjacent hair follicle keratinocytes. Using a transgenic mouse model to overexpress β-catenin in CD133+ dermal papilla cells, they found this enhanced spheroid forming ability within hydrogels. When CD133+ papilla cells over expressing β-catenin were used in hair inductive patch assays, more hairs with longer hair shafts were induced compared to CD133+ controls. The authors conclude that β-catenin/wnt signalling within dermal papilla cells enhances hair growth, and hair inducing capacity. This is slightly different to the Rognoni paper described above, that showed that hair neogenesis requires an inhibition of wnt signalling within the dermis. However, in the latter paper hair neogenesis is wound induced, while in the Zhou paper neogenesis is in an inductive assay.
Expansion of hair follicle stem cells sticking to isolated sebaceous glands to generate in vivo epidermal structures.
Cell Transplant. 2016 Jun 9.
Isolating hair follicle stem cells is a long process, requiring microdissection or enzymatic digestion, followed by FACs to purify out the relevant cells. In this study, Zhang et al describe a new method of isolating hair follicle stem cells from rat whisker follicles. They found that when they isolated sebaceous glands from these follicles and grew them in culture, after a few days epithelial cells migrated away from the glands. These epithelial cells were Itga6, p63, Plet1 and Krt15 positive, suggesting that they were hair follicle stem cells. In induction assays, these cells contributed to the formation of new hair follicles and fibers. The authors conclude that hair follicle stem cells adhere, or stick to sebaceous glands. Therefore, isolation of sebaceous glands with adhered keratinocytes is a novel way to isolate hair follicle stem cells.
Familial frontal fibrosing alopecia treated with dutasteride, minoxidil and artificial hair transplantation.
Australas J Dermatol. 2016 Jun 7. doi: 10.1111/ajd.12499.
Frontal fibrosing alopecia was first described in 1994, and has been rapidly increasing in incidence since ever since. It is characterised by hair loss along the frontal hairline and eyebrows. It is a scarring alopecia, and mainly affects postmenopausal women, however no conclusive treatment plans have been described. In this case report, Cranwell and Sinclair describe frontal fibrosing alopecia in a premenopausal woman. Upon diagnosis the patient’s mother was examined, and also diagnosed with frontal fibrosing alopecia. This is interesting as it implies there are genetic factors that can increase susceptibility to frontal fibrosing alopecia, rather than just environmental factors. The patient was initially given triamcinolone 5mg/ml with lignocaine 1% at 6 week intervals, although this did not arrest progression of hair loss. Subsequently, treatment with dutasteride 0.1mg daily and minoxidil 1mg daily seemed to stabilise hair loss, for at least 3 years post follow up. This report suggests that dutasteride is an effective stabiliser of frontal fibrosing alopecia, although more expansive studies are required in the future.