Tamoxifen-induced hair colour change

Human Hair Graying Revisited: Principles, Misconceptions, and Key Research Frontiers

Hair graying holds psychosocial importance and serves as an excellent model for studying human pigmentation and aging in an accessible miniorgan. Current evidence suggests that graying results from an interindividually varying mixture of cumulative oxidative and DNA damage, excessive mTORC1 activity, melanocyte senescence, and inadequate production of pigmentation-promoting factors in the hair matrix. Various regulators modulate this process, including genetic factors (DNA repair defects and IRF4 sequence variation, peripheral clock genes, P-cadherin signaling, neuromediators, HGF, KIT ligand secretion, and autophagic flux. This leads to reduced MITF- and tyrosinase-controlled melanogenesis, defective melanosome transfer to precortical matrix keratinocytes, and eventual depletion of hair follicle (HF) pigmentary unit (HFPU) melanocytes and their local progenitors. Graying becomes irreversible only when bulge melanocyte stem cells are also depleted, occurring later in this process. Distinct pigmentary microenvironments are created as the HF cycles: early anagen is the most conducive phase for melanocytic reintegration and activation, and only during anagen can the phenotype of hair graying and repigmentation manifest, whereas the HFPU disassembles during catagen. The temporary reversibility of graying is highlighted by several drugs and hormones that induce repigmentation, indicating potential target pathways. We advise caution in directly applying mouse model concepts, define major open questions, and discuss future human antigraying strategies.

A Comprehensive Review of Mammalian Pigmentation: Paving the Way for Innovative Hair Colour-Changing Cosmetics

The natural colour of hair shafts is formed at the bulb of hair follicles, and it is coupled to the hair growth cycle. Three critical processes must happen for efficient pigmentation: (1) melanosome biogenesis in neural crest-derived melanocytes, (2) the biochemical synthesis of melanins (melanogenesis) inside melanosomes, and (3) the transfer of melanin granules to surrounding pre-cortical keratinocytes for their incorporation into nascent hair fibres. All these steps are under complex genetic control. The array of natural hair colour shades are ascribed to polymorphisms in several pigmentary genes. A myriad of factors acting via autocrine, paracrine, and endocrine mechanisms also contributes for hair colour diversity. Given the enormous social and cosmetic importance attributed to hair colour, hair dyeing is today a common practice. Nonetheless, the adverse effects of the long-term usage of such cosmetic procedures demand the development of new methods for colour change. In this context, case reports of hair lightening, darkening and repigmentation as a side-effect of the therapeutic usage of many drugs substantiate the possibility to tune hair colour by interfering with the biology of follicular pigmentary units. By scrutinizing mammalian pigmentation, this review pinpoints key targetable processes for the development of innovative cosmetics that can safely change the hair colour from the inside out.

The biology of human hair greying

Hair greying (canities) is one of the earliest, most visible ageing-associated phenomena, whose modulation by genetic, psychoemotional, oxidative, senescence-associated, metabolic and nutritional factors has long attracted skin biologists, dermatologists, and industry. Greying is of profound psychological and commercial relevance in increasingly ageing populations. In addition, the onset and perpetuation of defective melanin production in the human anagen hair follicle pigmentary unit (HFPU) provides a superb model for interrogating the molecular mechanisms of ageing in a complex human mini-organ, and greying-associated defects in bulge melanocyte stem cells (MSCs) represent an intriguing system of neural crest-derived stem cell senescence. Here, we emphasize that human greying invariably begins with the gradual decline in melanogenesis, including reduced tyrosinase activity, defective melanosome transfer and apoptosis of HFPU melanocytes, and is thus a primary event of the anagen hair bulb, not the bulge. Eventually, the bulge MSC pool becomes depleted as well, at which stage greying becomes largely irreversible. There is still no universally accepted model of human hair greying, and the extent of genetic contributions to greying remains unclear. However, oxidative damage likely is a crucial driver of greying via its disruption of HFPU melanocyte survival, MSC maintenance, and of the enzymatic apparatus of melanogenesis itself. While neuroendocrine factors [e.g. alpha melanocyte-stimulating hormone (α-MSH), adrenocorticotropic hormone (ACTH), ß-endorphin, corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH)], and micropthalmia-associated transcription factor (MITF) are well-known regulators of human hair follicle melanocytes and melanogenesis, how exactly these and other factors [e.g. thyroid hormones, hepatocyte growth factor (HGF), P-cadherin, peripheral clock activity] modulate greying requires more detailed study. Other important open questions include how HFPU melanocytes age intrinsically, how psychoemotional stress impacts this process, and how current insights into the gerontobiology of the human HFPU can best be translated into retardation or reversal of greying.

Medication-Induced Repigmentation of Gray Hair: A Systematic Review

Hair graying is a common sign of aging resulting from complex regulation of melanogenesis. Currently, there is no medical treatment available for hair repigmentation. In this article we review the literature on medication-induced hair repigmentation, discuss the potential mechanisms of action, and review the quality of the literary data. To date, there have been 27 studies discussing medication-induced gray hair repigmentation, including 6 articles on gray hair repigmentation as a primary objective, notably with psoralen treatment or vitamin supplementation, and 21 reports on medication-induced gray hair repigmentation as an incidental finding. Medications noted in the literature include anti-inflammatory medications (thalidomide, lenalidomide, adalimumab, acitretin, etretinate, prednisone, cyclosporin, cisplatinum, interferon-α, and psoralen), stimulators of melanogenesis (latanoprost, erlotinib, imatinib, tamoxifen, and levodopa), vitamins (calcium pantothenate and para-amino benzoic acid), a medication that accumulates in tissues (clofazimine), and a medication with an undetermined mechanism (captopril). Diffuse repigmentation of gray hair can be induced by certain medications that inhibit inflammation or stimulate melanogenesis. There is also low-quality evidence that some vitamin B complex supplementation can promote gray hair darkening. While these compounds are not currently indicated for the treatment of gray hair, their mechanisms shed light on targets for future medications for hair repigmentation.

Hair darkening in porphyria cutanea tarda

Repigmentation of grey hair is rare, but has been described in several clinical settings. It has most often been reported as a postinflammatory effect, but several drugs, chronic arsenic exposure and coeliac disease have also been cited in addition to darkening as a spontaneous phenomenon. We report two patients with sustained repigmentation of the hair in association with porphyria cutanea tarda. The mechanism for this repigmentation remains elusive, but presumably involves recruitment of outer root sheath melanocytes, which are then activated to form functional hair bulb melanocytes.

Cutaneous Reactions to Chemotherapeutic Agents

The task of evaluating a cutaneous eruption in the patient receiving chemotherapy can be quite formidable. Most of the time, these patients are receiving a multitude of agents and have profound immunosuppression. These factors may alter the more common manifestations of cutaneous eruptions. This article presents some of the more common cutaneous eruptions that may occur in an oncology patient receiving chemotherapy. It is hoped we may recognize clinical patterns seen with chemotherapeutic agents in the immunosuppressed population and, by recognizing these cutaneous eruptions, we may avoid the pitfalls of discontinuing medicines that may certainly be needed or altering the treatment course in a patient.

Mucocutaneous reactions to chemotherapy

Chemotherapeutic agents are a widely used treatment modality. Side effects range from common to unusual and may be confused with other cutaneous sequelae of oncologic treatment. The goal of this communication is to elaborate on previous descriptions of the cutaneous manifestations of chemotherapeutic treatment and to discuss more recent findings.

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should be able to generate a differential diagnosis of possible etiologies for varying patterns of cutaneous involvement in patients receiving chemotherapy and identify the various cutaneous side effects of chemotherapeutic treatment. In addition, they should be able to distinguish life-threatening side effects that require immediate management from more benign manifestations of chemotherapeutic treatment.