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The skin continuously serves as a biosensor of multiple exogenous stressors and integrates the resulting responses with an individual's central and peripheral endogenous response systems to perceived stress; it also acts to protect against external challenges such as wounding and infection. We have previously shown in mice that stress induces nerve growth factor- and substance P-dependent neurogenic inflammation, which includes the prominent clustering of MHC class II(+) cells. Because the contribution of dendritic cells (DCs) in response to stress is not well understood, we examined the role of DCs in neurogenic inflammation in murine skin using a well-established murine stress model. We show that sound stress increases the number of intradermal langerin(+) and CD11c(+) DCs and induces DC maturation, as indicated by the up-regulated expression of CD11c, MHC class II, and intercellular adhesion molecule-1 (ICAM-1). Blocking of ICAM-1/leukocyte function-associated antigen-1 interactions significantly abrogated the stress-induced numeric increase, maturation, and migration of dermal DCs in vivo and also reduced stress-induced keratinocyte apoptosis and endothelial cell expression of ICAM-1. In conclusion, stress exposure causes a state of immune alertness in the skin. Such adaptation processes may ensure protection from possible infections on wounding by stressors, such as attack by predators. However, present-day stressors have changed and such adaptations appear redundant and may overrun skin homeostasis by inducing immune dermatoses.

Background: Depilation has greatly promoted our understanding of hair follicle biology, however, only marginally of telogen (the "resting" stage of the hair cycle). Since electron paramagnetic resonance (EPR) spectroscopy provides an instructive technique for analyzing hair biology, it may be useful for telogen research., Objectives: To identify differences in murine telogen skin after a spontaneous and depilation-induced hair follicle cycling, and to analyze applicability of EPR to investigate telogen., Methods: Spontaneous or depilation-induced hair cycling in C57BL/6 mice. EPR spectroscopy of unshaven skin and of shaved hair shafts, microscopical examination of plucked or shed hair shafts, standardized histomorphometry., Results: Melanin EPR signals did not differ qualitatively between the two examined types of skin, nor did depilation change the hair length. However, unmanipulated telogen skin revealed greater thickness, stronger EPR signals, 25% more hair shafts, and lower melanin content of individual hair shafts, as creating a much more intricate mosaic of telogen hair follicles with various numbers of hair shafts (0-3) than the skin after depilation-induced hair growth. In both types of skin empty pilary canals were found. Both groups of animals lost hair shafts which were typical of exogen (the actively controlled process of hair shedding)., Conclusions: EPR spectroscopy can be profitably employed to study telogen. Murine telogen skin reveals a kenogen-like phenomenon (the "lag" phase following telogen and exogen when hair follicles remain empty, i.e. are devoid of hair shafts). Murine skin thickness in telogen and individual hair shaft pigmentation depend on the way of hair growth induction. Telogens after a spontaneous or depilation-induced hair growth are biologically distinct.

The materno-fetal interface has for long been considered as an immune privileged biological site and thus understanding the mechanisms underlying fetal survival have been the focus of intense research. In adults, survivin and Stat-3 proteins are involved in tolerance as well as the induction of apoptosis. However, the role of these molecules in pregnancy and development has not been addressed. We have evaluated the expression of survivin and Stat-3 in allogeneic mouse models of low abortions (CBA/J x Balb/c), abortion prone (CBA/J x DBA/2J) and stress-triggered abortions from DBA/2J-mated CBA/J mice. We show that survivin is over-expressed in abortion-prone mating on gestation day 7.5. This effect was also found in stress-exposed mice, whereas expression was low in normal pregnancy mice. The phosphorylated Stat-3 (p-Stat-3) was down regulated in high abortion mating compared with low abortion mating, CBA/J x Balb/c. The level of apoptosis was similar in the three groups studied. Our results suggest that high expression of survivin and low expression of p-Stat-3 are involved in pregnancy loss in mice.

After chemical, biological, or physical damage, growing (i.e. anagen) hair follicles develop abnormalities that are collectively called hair follicle dystrophy. Comparatively lower follicular damage induces the "dystrophic anagen" response pathway (=prolonged, dystrophic anagen, followed by severely retarded follicular recovery). More severe follicular damage induces the dystrophic catagen pathway (=immediate anagen termination, followed by a dystrophic, abnormally shortened telogen and maximally fast follicular recovery). In order to recognize these distinct damage response strategies of the hair follicle in a clinical or histopathological context, we have used the well-established C57BL/6J mouse model of cyclophosphamide-induced alopecia to define pragmatic classification criteria for hair follicle dystrophy (e.g., structure and pigmentation of the hair shaft, location, and volume of ectopic melanin granules, distension of follicular canal, number of TdT-mediated dUTP nick end labeling positive keratinocytes in the hair bulb; neural cell-adhesion molecule immunoreactivity and alkaline phosphatase activity as markers for the level of damage to the follicular papilla). These classification criteria for hair follicle dystrophy are useful not only in chemotherapy-induced alopecia models, but also in the screening of drug-treated or mutant mice in a highly standardized, accurate, sensitive, reproducible, easily applicable, and quantifiable manner.

Recently, we have revealed the existence of a "brain-hair follicle axis" in murine skin and have identified the neuropeptide substance P (SP) as a key mediator of stress-induced hair growth inhibition in vivo. Published evidence suggests that increased numbers of SP-immunoreactive sensory fibers, as seen in the dermis of stressed mice in anagen-catagen transition, are a result of transient high levels of nerve growth factor (NGF). Thus, we now aimed at dissecting the role of NGF in stress-triggered hair growth termination in our murine model. By real time PCR and immunohistochemistry, stress-exposed mice showed an up-regulation of NGF and its low-affinity receptor p75NTR; the NGF high-affinity receptor TrkA was moderately down-regulated. On neutralization of NGF, premature onset of catagen, apoptosis, and increased number/activation of perifollicular mast cells and antigen-presenting cells, which reflects the skin response to stress, was significantly abrogated. Stress or subcutaneous injection of recombinant NGF (to mimic stress) resulted in an increased percentage of SP(+) neurons in dorsal root ganglia, as measured by retrograde tracing. Taken together, these data suggest that NGF is a central element in the perifollicular neurogenic inflammation that develops during the murine skin response to stress and antagonizing NGF may be a promising therapeutic approach to counter the negative effect of stress on hair growth.

Estrogen receptor ligands are important modulators of skin physiology and are involved in the control of normal hair follicle cycling. Here, we have studied the effects of topically applied 17-beta-estradiol on pathologic hair follicle cycling as seen during chemotherapy-induced alopecia, one of the major unresolved problems of clinical oncology. For this study we employed a well-established murine model that mimics chemotherapy-induced alopecia in humans. For precisely quantifying the area of hair loss and hair regrowth in this model in vivo, we developed a simple planimetric assay (dotmatrix planimetry). We show that topical 17-beta-estradiol significantly alters the cycling response of murine follicles to cyclophosphamide, whereas the estrogen antagonist ICI 182.780 exerted no such effects. Initially, topical 17-beta-estradiol enhanced chemotherapy-induced alopecia significantly by forcing the follicles into the dystrophic catagen response pathway to hair follicle damage, whereas follicles treated by ICI 182.780 or vehicle shifted into the dystrophic anagen response pathway. Consequently, the regrowth of normally pigmented hair shafts after chemotherapy-induced alopecia was significantly accelerated in the 17-beta-estradiol treated group. Our data encourage one to explore topical estrogens as a potential stimulant for hair re-growth after chemotherapy-induced alopecia.

It has been much disputed whether or not stress can cause hair loss (telogen effluvium) in a clinically relevant manner. Despite the paramount psychosocial importance of hair in human society, this central, yet enigmatic and controversial problem of clinically applied stress research has not been systematically studied in appropriate animal models. We now show that psychoemotional stress indeed alters actual hair follicle (HF) cycling in vivo, ie, prematurely terminates the normal duration of active hair growth (anagen) in mice. Further, inflammatory events deleterious to the HF are present in the HF environment of stressed mice (perifollicular macrophage cluster, excessive mast cell activation). This provides the first solid pathophysiological mechanism for how stress may actually cause telogen effluvium, ie, by hair cycle manipulation and neuroimmunological events that combine to terminate anagen. Furthermore, we show that most of these hair growth-inhibitory effects of stress can be reproduced by the proteotypic stress-related neuropeptide substance P in nonstressed mice, and can be counteracted effectively by co-administration of a specific substance P receptor antagonist in stressed mice. This offers the first convincing rationale how stress-induced hair loss in men may be pharmacologically managed effectively.