The effect of repeated plucking on mouse skin cell kinetics

Potential Effect of Epilation on the Outcome of Surgery for Trachomatous Trichiasis

Purpose

To evaluate the association of epilation before surgery on the surgical outcome in trachomatous trichiasis (TT) patients.

Methods

As a secondary data analysis, 1452 patients enrolled in the STAR trial were categorized according to preoperative epilation status. The main outcome was recurrent trichiasis after surgery. We used multivariable analysis, time-to-event analysis, and Cox proportional hazards model.

Results

Those who epilated prior to surgery tended to be older and female, with worse entropion at baseline. The proportion with postoperative trichiasis was 7.7%, 8.8% in those who epilated versus 5.3% in those who did not (P = 0.03). Adjusting for age and sex, the risk of postoperative TT with epilation was 1.71 (P value = 0.02). Although entropion may be in the biological pathway from epilation to postoperative TT, we adjusted for entropion, and the risk of postoperative TT with epilation was 1.41 (P = 0.14).

Conclusions

The study suggests that preoperative epilation may increase the risk of postoperative trichiasis. Further research is needed to confirm the finding.

Translational Relevance

Patients with TT often self-treat, epilating their inturned eyelashes. The World Health Organization recommends surgery to treat TT, but when patients refuse the procedure or mild trichiasis is present, epilation is often recommended. There is some evidence that repetitive or improper epilation can be harmful to the lid and hair follicles. If there is damage to the lid margin, any subsequent surgery could have deleterious outcomes.

Proliferation in murine epidermis after minor mechanical stimulation. Part 1. Sustained increase in keratinocyte production and migration

It was our objective to obtain an insight into the details and dynamics of the cell proliferative changes following minor barrier disruption, the mechanisms of recovery, and their regulation. Hair of the dorsal area of DBA2-mice was removed and the epidermis was tape stripped. Tritiated thymidine was injected into groups of mice at daily intervals thereafter. Labelling and nuclear densities were measured at several time intervals later in the various epidermal strata to characterize cell production and cell fluxes through the tissue. A dramatic proliferative response was observed at 24 h when the labelling density increased more than sixfold in the basal layer. Labelled cells rapidly appeared in suprabasal layers within a few hours in large quantities while this process took over 2 days in normal skin. Some cycling cells were also found in the suprabasal layer (pulse labelling at 24 h) in contrast with the controls. The cellular flux through the suprabasal layers was drastically (20-fold) increased and the transit time was shortened. Although the nuclear density in the basal layer showed only moderate changes it increased four-fold in the suprabasal layer within 5 days. A kinetic model analysis suggested that the cell cycle time of proliferative cells dropped from a normal value of about 200 h to less than 12 h post tape strip. After 7 days, the proliferative activation still persisted, even though at 3 days post tape strip the stratum corneum had been re-established. Hence, a mild mechanical alteration with removal of some parts of the cornified layer in mouse backskin epidermis triggers a huge proliferative response with massive overproduction of cells that lasts at least 7 days. Our findings suggest that the re-establishment of the cornified layer does not immediately shut down cell proliferation and that more complex, slower (long-term) regulatory processes are involved.

Pten deficiency in melanocytes results in resistance to hair graying and susceptibility to carcinogen-induced melanomagenesis

Phosphate and tensin homologue deleted on chromosome 10 (PTEN) is a tumor suppressor gene inactivated in numerous sporadic cancers, including melanomas. To analyze Pten functions in melanocytes, we used the Cre-loxP system to delete Pten specifically in murine pigment-producing cells and generated DctCrePten(flox/flox) mice. Half of DctCrePten(flox/flox) mice died shortly after birth with enlargements of the cerebral cortex and hippocampus. Melanocytes were increased in the dermis of perinatal DctCrePten(flox/flox) mice. When the mutants were subjected to repeated depilations, melanocyte stem cells in the bulge of the hair follicle resisted exhaustion and the mice were protected against hair graying. Although spontaneous melanomas did not form in DctCrePten(flox/flox) mice, large nevi and melanomas developed after carcinogen exposure. DctCrePten(flox/flox) melanocytes were increased in size and exhibited heightened activation of Akt and extracellular signal-regulated kinases, increased expression of Bcl-2, and decreased expression of p27(Kip1). Our results show that Pten is important for the maintenance of melanocyte stem cells and the suppression of melanomagenesis.

Dermatologic investigation of alopecia in rhesus macaques (Macaca mulatta)

Coat damage has been reported frequently in captive rhesus macaques (Macaca mulatta), and it is a serious health problem because the hair coat functions as an anatomic and physiologic barrier between the animal and the environment. The purpose of this study was to identify the pathogenesis of coat damage in this species and to exclude the most frequent causes of alopecia. The investigation included clinical, hematologic, bacteriologic, mycologic, parasitologic, and histopathologic evaluations. A broad systematic dermatologic investigation was performed on 156 rhesus macaques, kept under variable environmental conditions, at the German Primate Center, Göttingen. In addition, 27 animals from other primate facilities were incorporated into the study. Clinically, 126 animals showed partial alopecia of varying severity, with complete alopecia in the worst cases. In 88% of the cases, the disorder was bilaterally symmetrical. The back and extremities were most commonly affected. No gross clinical changes of the skin surface were detected. Histologic changes consisted predominantly of mild epidermal hyperkeratosis and mild perivascular dermatitis. The presence and severity of histologic lesions were not correlated to coat damage. Parasitic, bacterial, and mycotic causes of alopecia were ruled out. Overviewing these results, disturbances in environment and behavior controlling or influencing hair growth may lead to hair loss in captive rhesus macaques. Future studies should try to identify disturbances in extrinsic or intrinsic factors influencing hair follicle activity in rhesus macaques.

Inhibitory autocrine factors produced by the mesenchyme-derived hair follicle dermal papilla may be a key to male pattern baldness

BACKGROUND

Androgenetic alopecia, or male pattern baldness, is a common, progressive disorder where large, terminal scalp hairs are gradually replaced by smaller hairs in precise patterns until only tiny vellus hairs remain. This balding can cause a marked reduction in the quality of life. Although these changes are driven by androgens, most molecular mechanisms are unknown, limiting available treatments. The mesenchyme-derived dermal papilla at the base of the mainly epithelial hair follicle controls the type of hair produced and is probably the site through which androgens act on follicle cells by altering the regulatory paracrine factors produced by dermal papilla cells. During changes in hair size the relationship between the hair and dermal papilla size remains constant, with alterations in both dermal papilla volume and cell number. This suggests that alterations within the dermal papilla itself play a key role in altering hair size in response to androgens. Cultured dermal papilla cells offer a useful model system to investigate this as they promote new hair growth in vivo, retain characteristics in vitro which reflect their parent follicle's response to androgens in vivo and secrete mitogenic factors for dermal papilla cells and keratinocytes.

OBJECTIVES

To investigate whether cultured dermal papilla cells from balding follicles secrete altered amounts/types of mitogenic factors for dermal papilla cells than those from larger, normal follicles. We also aimed to determine whether rodent cells would recognize mitogenic signals from human cells in vitro and whether factors produced by balding dermal papilla cells could alter the start of a new mouse hair cycle in vivo.

METHODS

Dermal papilla cells were cultured from normal, balding and almost clinically normal areas of balding scalps and their ability to produce mitogenic factors compared using both human and rat whisker dermal papilla cells as in vitro targets and mouse hair growth in vivo.

RESULTS

Normal scalp cells produced soluble factors which stimulated the growth of both human scalp and rat whisker dermal papilla cells in vitro, demonstrating dose-responsive mitogenic capability across species. Although balding cells stimulated some growth, this was much reduced and they also secreted inhibitory factor(s). Balding cell media also delayed new hair growth when injected into mice.

CONCLUSIONS

Human balding dermal papilla cells secrete inhibitory factors which affect the growth of both human and rodent dermal papilla cells and factors which delay the onset of anagen in mice in vivo. These inhibitory factor(s) probably cause the formation of smaller dermal papillae and smaller hairs in male pattern baldness. Identification of such factor(s) could lead to novel therapeutic approaches.

Methods of hair removal

The methods of hair removal vary between simple inexpensive means of home treatment (shaving, plucking, depilatories) to expensive and potentially time-consuming means used by paraprofessionals, nurses, and/or physicians (electrolysis, lasers, x-ray). The ways in which these different methods induce hair removal, the duration of such removal, and the nuances between devices within the same category of methods are discussed.

Extracellular stimulation of epidermal DNA synthesis

The removal of the topmost cell layers of the epidermal stratum corneum by stripping initiates a series of biochemical events which alters the normal homeostatic control of and results in the acceleration of the cell cycle in basal cells which are ten to twenty cell layers removed from the site of stripping. One measure of accelerated events is a stimulation of thymidine incorporation into epidermal DNA at time intervals following stripping. Two peaks of maximal stimulation occur between 12 and 24 hr and 48 and 54 hr after stripping. Stimulation of thymidine incorporation into epidermal DNA by limited stripping is a useful technique for studying the stripping-initiated signal at the stratum corneum and its subsequent translation at the proliferative cell receptor site.

Hair

The psychologic importance of hair to man is in inverse ratio to its physical function. Except for scalp hair and desultory areas of sexual hair, most of man's hair follicles are vestigial. Three problems of hair growth remain to be solved: (1) how the intermittent activity of hair follicles in both animals and man is controlled; (2) how the male hormone alters the hair cycle in human skin; and (3) why larger hairs are produced by testosterone in some areas of the body when in some individuals the hair follicles in the scalp regress. Studies in which skin grafts from rats of different ages were exchanged showed that hair follicles are innately programmed but can be slowly influenced by systemic factors. Steroid hormones, especially estrogens, slow down the moult cycle whereas thyroid hormones accelerate it. What establishes the innate rhythm remains problematical. The fact that plucking out the club hair initiates activity in resting follicles has been explained by the hypothesis that the mitotic inhibitor which accumulates during anagen is normally used up or dispersed during telogen or by wounding. However, contrary to this theory, follicular activity is not prolonged by epilation during anagen. Moreover, if rats are epilated within one or two days of eruption, only club hairs are removed since forceps cannot grasp the tips of the new hairs. Such epilation does not affect the anagen in progress, but remarkedly enough the subsequent resting phase is shortened. Both sexual hair and male-pattern baldness depend on androgenic hormones. Target organs of testosterone convert the hormone to active metabolites, chiefly 5alpha-dihydrotestosterone. In skin, however, 5alpha-dihydrotestosterone may not be the only active tissue androgen. The major metabolite of testosterone incubated with hair roots in androstenedione, and hirsute women without other obvious endocrine abnormality sometimes excrete high levels of androstanediol. Both steroids stimulated the sebaceous glands of hypophysectomized-castrated rats, which, however, showed only a limited response to testosterone. The androgenic steroids, the enzymes that convert them to their active metabolites, and the proteins that bind them are undoubtedly very important to the problems of the growth of sexual hair and male-pattern baldness.