Lipids to the top of hair biology

Little attention has been given to the impact of lipid metabolism on hair follicle biology and pathology. Three recent papers (one in the current issue) describe a major effect of altered lipid metabolism on hair growth. A direct link was made to at least one form of cicatricial alopecia, but the role lipids play in other follicular pathologies, such as the acneiform conditions, are inadequately explored and must be tested.

Overexpression of Hr links excessive induction of Wnt signaling to Marie Unna hereditary hypotrichosis

Marie Unna hereditary hypotrichosis (MUHH) is a rare autosomal dominant hair disorder. Through the study of a mouse model, we identified a mutation in the 5'-untranslated region of the hairless (HR) gene in patients with MUHH in a Caucasian family. The corresponding mutation, named 'hairpoor', was found in mutant mice that were generated through N-ethyl-N-nitrosourea mutagenesis. Hairpoor mouse mutants display partial hair loss at an early age and progress to near alopecia, which resembles the MUHH phenotype. This mutation conferred overexpression of HR through translational derepression and, in turn, decreased the expression of Sfrp2, an inhibitor of the Wnt signaling pathway. This study indicates that the gain in function of HR also results in alopecia, as seen with the loss of function of HR, via abnormal upregulation of the Wnt signaling pathway.

The mesenchymal component of hair follicle neogenesis: background, methods and molecular characterization

Hair follicle morphogenesis and regeneration occur by an extensive and collaborative crosstalk between epithelial and mesenchymal skin components. A series of pioneering studies, which revealed an indispensable role of follicular dermal papilla and dermal sheath cells in this crosstalk, has led workers in the field to study in detail the anatomical distribution, functional properties, and molecular signature of the trichogenic dermal cells. The purpose of this paper was to provide a practical summary of the development and recent advances in the study of trichogenic dermal cells. Following a short review of the relevant literature, the methods for isolating and culturing these cells are summarized. Next, the bioassays, both in vivo and in vitro, that enable the evaluation of trichogenic properties of tested dermal cells are described in detail. A list of trichogenic molecular markers identified by those assays is also provided. Finally, this methods review is completed by defining some of the major questions needing resolution.

What is the biological basis of pattern formation of skin lesions?

Pattern recognition is at the heart of clinical dermatology and dermatopathology. Yet, while every practitioner of the art of dermatological diagnosis recognizes the supreme value of diagnostic cues provided by defined patterns of 'efflorescences', few contemplate on the biological basis of pattern formation in and of skin lesions. Vice versa, developmental and theoretical biologists, who would be best prepared to study skin lesion patterns, are lamentably slow to discover this field as a uniquely instructive testing ground for probing theoretical concepts on pattern generation in the human system. As a result, we have at best scraped the surface of understanding the biological basis of pattern formation of skin lesions, and widely open questions dominate over definitive answer. As a symmetry-breaking force, pattern formation represents one of the most fundamental principles that nature enlists for system organization. Thus, the peculiar and often characteristic arrangements that skin lesions display provide a unique opportunity to reflect upon--and to experimentally dissect--the powerful organizing principles at the crossroads of developmental, skin and theoretical biology, genetics, and clinical dermatology that underlie these--increasingly less enigmatic--phenomena. The current 'Controversies' feature offers a range of different perspectives on how pattern formation of skin lesions can be approached. With this, we hope to encourage more systematic interdisciplinary research efforts geared at unraveling the many unsolved, yet utterly fascinating mysteries of dermatological pattern formation. In short: never a dull pattern!

Bioengineering the hair follicle: fringe benefits of stem cell technology

Recent advances in epithelial stem cell biology have resulted in the isolation of hair follicle stem cells, which generate hair follicles when injected into immunodeficient mice. These isolated hair follicle epithelial stem cells must be combined with 'inductive' dermal cells to produce new hair follicles. The advent of techniques for cultivating inductive dermal cells and competent epithelial stem cells creates the opportunity to bioengineer hair follicles for the treatment of hair loss.

Molecular insights into the hair follicle and its pathology: a review of recent developments

In the last few years by means of the elucidation of the human genome and the acquisition of powerful investigative tools we have begun to understand the molecular basis of hair follicle growth control. In this article I will describe some of the salient recent contributions to the field and review the implications these findings have had on our understanding of mechanisms in dermatology and dermatopathology.

Anaplastic neoplasms arising from basal cellcarcinoma xenotransplants into SCID-beige mice

BACKGROUND

An animal model for the study of basal cell carcinoma (BCC) is required to better understand its biology. Several attempts to grow BCC in immuno-incompetent animals have been only modestly successful.

METHODS

To test the ability of BCC to grow in a mouse with complete and severe immuno-incompetence, 14 individual BCC were transplanted into the subcutaneous tissue of 18 SCID-beige mice (T, B and natural killer cell deficient). Light microscopy and immunophenotypic analyses were performed on primary BCC and first and seventh passage tumors.

RESULTS

Transplantation of three BCC yielded rapidly growing anaplastic tumors for a tumor take of 18% (3/18). SCID-beige mice without tumor growth had mostly scars or epidermoid cysts at the transplant sites. The three patients whose BCC gave rise to the anaplastic tumors were significantly older than those without tumor growth (87 vs. 64, p = 0.001), but they did not differ with respect to BCC type or general health. These three anaplastic tumors were histologically and immunophenotypically similar, being composed of dyscohesive, pleomorphic cells that expressed vimentin and smooth muscle actin. In the first passage mice these tumors were locally invasive, tumor-forming nodules associated with an expansion of donor inflammatory cells (T and B lymphocytes and plasma cells), rare remnants of BCC epithelium and epidermoid cysts. By the seventh passage, the tumors were homogenous and metastasized widely throughout the mice. Changing transplantation location to the dermis to wound environment or supplementing the tumor with BCC-derived fibroblasts did not alter the phenotype or growth rate in SCID-beige mice. Anaplastic tumors also grew easily in SCID mice (T and B cell deficient). However, transplantation of the anaplastic tumors into normal mice (CB-17) or less severely immunodeficient mice (NCr and Balb/c: T and natural killer cell deficient) did not allow for growth. Furthermore, tumor growth could not be maintained in vitro.

CONCLUSION

Empirically, these data suggest that BCC has the potential to become an aggressive metastatic neoplasm, given the right immune and stromal environment. Moreover, a functional B lymphocyte system appears to prevent this growth. As human lymphocytes also engraft in SCID-beige mice, the original host immune response could be responsible for the lack of tumor growth in the majority of xenografts. Furthermore, the anaplastic and metastatic phenotype of these BCC derived neoplasms may be the experimental equivalent of metastatic BCC and BCC associated with carcinosarcoma.

Insights from the asebia mouse: a molecular sebaceous gland defect leading to cicatricial alopecia

The primary cicatricial alopecias have proven to be challenging for the clinician, dermatopathologist and the researcher--let alone the patient. If we are to improve our diagnostic and therapeutic tools for these very difficult disorders, we will need greater insight into their etiology. Recent work with the mouse mutant, asebia, provides a model for cicatricial alopecia. In this model the pathology--perifollicular inflammation, sebaceous gland "destruction", hair shaft granuloma, and cicatricial follicle drop-out--results from the mutation of one very important sebaceous gland gene. In the absence of this gene, the sebaceous gland is hypoplastic and normal sebum production is minimal to absent. In this paper the relevance of this mutant to human alopecias is discussed and the point emphasized that the pathogenesis of some forms of human cicatricial alopecia could involve the sebaceous gland.

A comprehensive guide for the accurate classification of murine hair follicles in distinct hair cycle stages

Numerous strains of mice with defined mutations display pronounced abnormalities of hair follicle cycling, even in the absence of overt alterations of the skin and hair phenotype; however, in order to recognize even subtle, hair cycle-related abnormalities, it is critically important to be able to determine accurately and classify the major stages of the normal murine hair cycle. In this comprehensive guide, we present pragmatic basic and auxiliary criteria for recognizing key stages of hair follicle growth (anagen), regression (catagen) and quiescence (telogen) in C57BL/6NCrlBR mice, which are largely based on previous work from other authors. For each stage, a schematic drawing and representative micrographs are provided in order to illustrate these criteria. The basic criteria can be employed for all mouse strains and require only routine histochemical techniques. The auxiliary criteria depend on the immunohistochemical analysis of three markers (interleukin-1 receptor type I, transforming growth factor-beta receptor type II, and neural cell-adhesion molecule), which allow a refined analysis of anatomical hair follicle compartments during all hair cycle stages. In contrast to prior staging systems, we suggest dividing anagen III into three distinct substages, based on morphologic differences, onset and progression of melanogenesis, and the position of the dermal papilla in the subcutis. The computer-generated schematic representations of each stage are presented with the aim of standardizing reports on follicular gene and protein expression patterns. This guide should become a useful tool when screening new mouse mutants or mice treated with pharmaceuticals for discrete morphologic abnormalities of hair follicle cycling in a highly reproducible, easily applicable, and quantifiable manner.

Scd3--a novel gene of the stearoyl-CoA desaturase family with restricted expression in skin

Stearoyl-coenzyme A (CoA) desaturase (SCD) is a key enzyme involved in the conversion of saturated fatty acids into monounsaturated fatty acids. Previously, two members of this gene family, namely, Scd1 and Scd2, have been reported. Here we report the identification and characterization of a novel member of this family, Scd3, whose expression is restricted to mouse skin, specifically to the sebaceous gland. The Scd3 gene codes for a transcript of approximately 4.9 kb with an open reading frame that results in a 359-amino-acid protein. Scd3 shares 91 and 88% identity in the protein-coding region with Scd1 and Scd2, respectively, and maps to mouse chromosome 19 in very close proximity to Scd1 and Scd2. Unlike Scd1, Scd3 expression is higher in male mouse skin than in female mouse skin. The promoter sequence of Scd3 reveals similarity with Scd1 in the proximal region but also possesses several distinctive features including the polyunsaturated fatty acid-response element. Scd3 is expressed in the skin of young asebia mutant mice (Scd1(ab2J)/Scd1(ab2J)) in the absence of Scd1. Scd3 expression changes during the mouse hair cycle but not as dramatically as Scd1. The tissue-specific and sex-dependent expression of Scd3 suggests the presence of gene- and hormonal-specific control mechanisms.

Controls of hair follicle cycling

Nearly 50 years ago, Chase published a review of hair cycling in which he detailed hair growth in the mouse and integrated hair biology with the biology of his day. In this review we have used Chase as our model and tried to put the adult hair follicle growth cycle in perspective. We have tried to sketch the adult hair follicle cycle, as we know it today and what needs to be known. Above all, we hope that this work will serve as an introduction to basic biologists who are looking for a defined biological system that illustrates many of the challenges of modern biology: cell differentiation, epithelial-mesenchymal interactions, stem cell biology, pattern formation, apoptosis, cell and organ growth cycles, and pigmentation. The most important theme in studying the cycling hair follicle is that the follicle is a regenerating system. By traversing the phases of the cycle (growth, regression, resting, shedding, then growth again), the follicle demonstrates the unusual ability to completely regenerate itself. The basis for this regeneration rests in the unique follicular epithelial and mesenchymal components and their interactions. Recently, some of the molecular signals making up these interactions have been defined. They involve gene families also found in other regenerating systems such as fibroblast growth factor, transforming growth factor-beta, Wnt pathway, Sonic hedgehog, neurotrophins, and homeobox. For the immediate future, our challenge is to define the molecular basis for hair follicle growth control, to regenerate a mature hair follicle in vitro from defined populations, and to offer real solutions to our patients' problems.

What controls hair follicle cycling?

Despite more than a hundred years of professional hair research, and substantial recent progress in unravelling the molecular controls of hair follicle morphogenesis, the chronobiological control system that cyclically drives the hair follicle through dramatic remodelling processes between phases of growth (anagen), regression (catagen), and relative resting (telogen) have remained disappointingly obscure. In view of the vast literature that has become available over the past decades on numerous genetic, biochemical, cellular and pharmacological aspects of hair growth follicle control under physiological and pathological conditions, it is astounding how comparatively few researchers in the field have published theoretical concepts that explore how hair follicle cycling might be controlled. Since this question is at the very heart of basic and clinically applied hair biology, it deserves a much more systematic and serious public exploration, which the following contributions are designed to stimulate.

Androgen-induced delay of hair growth in the golden Syrian hamster

The golden Syrian hamster flank organ has been used to study the stimulatory effect of androgens on sebaceous glands and hair. Androgens cause the sebaceous glands and hair follicles in this organ to grow. We have made the novel observation that exogenously administered androgen, testosterone propionate (TP), suppresses hair growth in the area surrounding the flank organ. When given in a time-release (systemic) subcutaneous dosage form (pellet), 25 mg TP inhibited the regrowth of clipped hair in peri-flank organ skin for up to 21 days; however, by 28 days hair grew back to the same extent as in controls. The peak serum level of testosterone in TP-treated animals occurred at 14 days, and declined thereafter. When two separate TP pellets (25 mg/pellet) were administered 14 days apart in order to maintain high serum levels for 28 days, the amount of hair regrowth after 35 days was identical to animals receiving a single TP pellet or placebo. This suggests that the systemic level of testosterone was not the only factor in hair regulation. Hair growing within the flank organ appeared to be unaffected by TP administration. In the golden Syrian hamster, androgen, as in humans, can exert stimulatory and inhibitory effects on hair growth depending on the body site. We conclude that this animal model could serve as a useful system to investigate the mechanisms responsible for the opposing effects of androgen on hair growth.

Laboratory assessment of hair follicle growth

This article reviews the methods currently used to assess hair growth properties of a compound. The methods exploit in vivo, in vitro and ex vivo methodology. The challenge for the field remains to develop a purely in vitro system which reflects in detail the in vivo state.

Differential subtraction display: a unified approach for isolation of cDNAs from differentially expressed genes

We have developed a novel efficient approach, termed differential subtraction display, for the identification of differentially expressed genes. Several critical parameters for the reproducibility and enhanced sensitivity of display, as well as steps to reduce the number of false positive cDNA species, have been defined. These include- (a) use of standardized oligo(dT)-primed cDNA pools rather than total RNA as the starting material for differential display, (b) critical role of optimal cDNA input for each distinct class of primers, (c) phenomena of primer dominance and interference, and (d) design of a novel set of enhanced specificity anchor primers. Introduction of an efficient subtractive hybridization step prior to cloning of cDNA species enriches the bona fide cDNA species that are either exclusively present in one sample (+/-) or show altered expression (up-/down-regulation) in RNA samples from two different tissues or cell types. This approach, in comparison to differential display, has several advantages in terms of reproducibility and enhanced sensitivity of display coupled to the cloning of enriched bona fide cDNA species corresponding to differentially expressed RNAs.

Expression of two Ig family adhesion molecules in the murine hair cycle: DCC in the bulge epithelia and NCAM in the follicular papilla

The hair cycle involves remodeling of cells and of cell groups into a complex follicular structure. During skin appendage development, adhesion molecules such as neural cell adhesion molecule (NCAM) and deleted in colon carcinoma (DC) participate in the formation of cell groups. NCAM has been found to be expressed in the mesenchyme during mouse hair follicle induction. DCC expression has been observed in the epithelial cells of the developing feather. We postulate that these two molecules may also define cell groups in the cycling hair follicle. Here we report their spatio-temporal expression patterns during the depilation-induced murine hair cycle. NCAM expression was also examined in positive and negative hair-inductive follicular papilla cell lines. Throughout the hair cycle, DCC expression was confined to the basal keratinocytes of the epidermis and the epithelial portion of the hair follicle. During mid-anagen, two types of deleted in colon carcinoma staining were observed. One was a cell surface pattern seen in the epithelial cells in the bulge region where the follicular stem cells reside. The other was a diffuse cytoplasmic staining pattern in the transient hair follicle epithelia located below the bulge region. Prominent NCAM staining was observed in the follicular papilla throughout the hair cycle and was accompanied by weak staining of the matrix epithelia. NCAM expression correlated with hair induction by a follicular papilla cell line. The results suggest that DCC and NCAM define the permanent cell groups of the hair follicle and that NCAM is important for hair induction.

Fibroblast-dependent induction of a murine skin lesion similar to human nevus sebaceus of Jadassohn

Using a nude mouse grafting model, we have demonstrated that normal-haired skin is regenerated in a graft containing hair buds and dissociated dermis. Altering the dermal component leads to changes typical of the human nevus sebaceus of Jadassohn (NSJ). The murine lesion is characterized by sebaceous gland hyperplasia, abortive hair follicles, and epidermal hyperplasia. The development of the NSJ-like lesion is independent of the epidermal component but dependent on a specific dermal fibroblast combination, namely, a hair-inductive follicular papilla fibroblast cell line plus BALB/c 3T3 fibroblasts. Non-hair-inductive follicular papilla cell lines in combination with BALB/c 3T3 fibroblasts are unable to induce the NSJ-like structure, indicating that hair-inductive signals play a central role in its pathogenesis. BALB/c 3T3 fibroblasts in combination with total cells from dissociated neonatal dermis produce abortive hair follicles, but the sebaceous gland hyperplasia is suppressed, suggesting the presence of suppressive endogenous dermal factors. The data suggest that (a) pilosebaceous induction is a multistep process and (b) the pathogenesis of NSJ involves perturbation of a complex array of inductive mesenchymal (dermal) signals. This paper describes the first animal model of NSJ and provides evidence that development of the human lesion could depend entirely on aberrant dermal cells.

Hair follicle growth controls

Research in hair biology has embarked in the pursuit for molecules that control hair growth. Many molecules already have been associated with the controls of hair patterning, hair maturation, and hair cycling and differentiation. Knowing how these molecules work gives us the tools for understanding and treating patients with hair disorders.

Fibroblast-dependent induction of a murine skin lesion with similarity to human common blue nevus

In an attempt to define epithelial-mesenchymal interactions in skin appendage formation, we have been studying a nude mouse grafting model that permits the combination of heterotypic and heterochronic epithelial and mesenchymal cells. In this study using neonatal hair bud cells combined with various mesenchymal cell preparations, we show that one can regenerate near-complete skin with intact epidermal and dermal layers plus mature hair follicles. It was determined that the character of the resulting regenerated skin could be manipulated as a function of the specific mesenchymal component. Lack of dermal cells resulted in a scar, whereas inclusion of a suspension of dissociated total dermal cells resulted in near-complete skin regeneration, and in the presence of follicular papilla fibroblasts (both hair-inductive and non-hair-inductive) or NIH3T3 fibroblasts, the reconstitution had similarity to the common blue nevus. The results indicate that 1) a stimulant of human common blue nevus can be produced in an animal model, 2) the underlying disorder of the lesion in mice appears to be entirely dermal in origin, arising independent of the epidermal component, and 3) complex dermal cell interactions involving lesion-initiative and lesion-suppressive activities underlie the pathogenesis. This experimental system will serve as a valuable tool in elucidating cutaneous dermal-epidermal signals in normal skin as well as the alteration of these signals in malformations such as the hamartoma described here.

Changes in expression of apoptosis-associated genes in skin mark early catagen

Programmed cell death is central to hair biology, as the hair follicle undergoes cycles of growth (anagen), regression (catagen), and rest (telogen). During catagen, the hair follicle shortens via a pathway of programmed cell death and apoptosis. The molecular mechanisms involved in this process have not been elucidated yet. Using reverse transcriptase-polymerase chain reaction, we examined in this study the expression in total skin, throughout one hair cycle, of a series of regulatory genes associated with apoptosis. We show that gene expression within skin is hair-cycle-dependent. Transforming growth factor-beta was expressed immediately before catagen; therefore, it might be involved in the early signaling of this process. Tumor necrosis factor-beta was expressed during catagen and might be involved in follicular apoptosis. Several proto-oncogenes and transcription factors have been described in the regulation of apoptosis in other systems. Here we show that the transcript levels of c-myc, c-myb, and c-jun changed immediately before or during early catagen and thus could be involved in the signaling or regulation of catagen. Levels of p53 remained constant throughout anagen and catagen, suggesting that p53 is not involved in the developmentally induced apoptosis of the hair follicle. The variable expression throughout the hair cycle of the genes described demonstrates the dynamic changes of the skin and underscores the importance of studying the complete hair cycle when characterizing any molecule in skin.

Transection level dictates the pattern of hair follicle sheath growth in vitro

Using a newly developed in vitro sheep hair culture system, we found that the pattern of sheath growth is a function of the level at which the follicle is transected. Two patterns are observed. The type 1 pattern, which occurs after the follicle is transected below the sebaceous gland, shows an equal elongation of the sheath and shaft. The type 2 pattern, which occurs when the follicle is cultured either after transection above the sebaceous gland or with an intact attached epidermis, is characterized by growth of hair shaft clean of sheath. These growth patterns, dictated by the transection level, are observed in both sheep and human follicles, are not dependent on the presence of the sebaceous gland itself, and are not influenced by the presence of co-cultured epidermis or infundibulum. Thymidine autoradiography demonstrates that transecting follicles beneath the sebaceous gland leads to an increase in DNA synthesis of the cells in the external root sheath, but does not alter DNA synthesis of the cells in the follicle matrix. Besides the obvious implications to wound closure, these findings indicate that the sebaceous gland demarcates a significant region of the follicle which influences sheath-shaft interactions and that the sheath and the shaft constitute coordinated cell populations which nevertheless respond distinctly to proliferative signals.

Expression of the bcl-2 protooncogene in the cycling adult mouse hair follicle

The hair follicle undergoes a cycle of growing, regressing, and resting phases (anagen, catagen, telogen, respectively). As the follicle enters catagen, the cells of the lower, cycling portion undergo a process of controlled cell death (apoptosis). Understanding the mechanism of apoptosis in the follicle should give insight into one of the control steps of hair cycling. In this study we sought the expression of bcl-2, a protooncogene associated with apoptosis control, in the cycling follicle of the adult mouse. Using a monoclonal antibody to the mouse protein we immunolocalized bcl-2 gene product in the cycling pelage follicle of the C57/B6 adult mouse. The protein was expressed in the follicular papilla (a non-cycling portion of the follicle) throughout the cycle-including telogen. The cycling follicular epithelium, however, showed positive antibody staining in anagen, which decreased in catagen and disappeared in telogen. In anagen the cells of the bulb, bulge, and basal layer of the outer root sheath expressed the bcl-2 protein. Understanding the action of this apoptosis-inhibiting molecule should serve to elucidate the dynamics of follicular cycling.

Molecules of the cycling hair follicle--a tabulated review

In this review we tabulated molecules which have been experimentally identified to be associated with, or play a role in, hair follicle growth. While compiling these data we were impressed by the fact that this field is only now beginning to be developed in terms of molecular analysis. Ironically, hair was used in some of the earliest molecular approaches to biologic structure (e.g. Astbury and Street, 1931), but the field did not develop from there. From our review we have come to the following conclusions. (1) As indicated by the growing number of reports dealing with follicle-associated molecules in the past 3 years, the field of hair biology has entered a new molecular era. (2) In many reported hair biology studies not enough emphasis has been placed on the fact that the follicle is a dynamic structure. All too often a study is limited to follicles of one particular phase of the cycle or one phase of development. Students in the field have to be more sensitive to the remarkable changes that this deceptively simple structure can undergo during its cycle. (3) Although we have not been able to find any molecules unique to the follicle, some of the structural molecules come close to an ideal tool. It is our impression that even more specific molecule tags will be found. Whether this requires a subtraction library approach or gene mapping of specific mutants is not yet clear. It would appear that the large, diverse family of intermediate filament-associated proteins will prove to be an excellent source of unique follicle-labeling molecules. (4) There is an acute need for molecules which distinguish the phases of the cycle, e.g. telogen from early anagen. Telogen is by far the most difficult phase to identify morphologically since the earliest phase of anagen and the latest phase of catagen may appear structurally like telogen. That these phases are functionally distinguishable must imply a molecular difference. As the number of recognized hair follicle-associated molecules and their interactions increase, it will be essential to assemble libraries of highly specific RNA and antibody probes for localization and mapping studies. We recognize that this review, as written, is imperfect. It is particularly deficient in making any effort towards identifying unifying principles of structure and function. We look forward to returning to this subject within 3 years.(ABSTRACT TRUNCATED AT 400 WORDS)

Isolation and culture of follicular papillae from murine vibrissae: an introductory approach

The recent successes in culturing follicular papilla cells have afforded a rapid advance in our understanding of hair biology. Although the experimental manipulation of the papilla is briefly described in the original reports, a detailed description for workers starting in the field is not yet available. In this report we give a brief review of hair biology relevant to the papilla, and illustrate the method we have found successful for isolating and growing papilla cells.

Homeobox genes and the patterning of skin diseases

Fundamental to our understanding of skin diseases and their presentation is an understanding of the pattern of their development. When we have established the molecular basis of their development we will be in a much better position to control and treat such diseases. The homeobox genes are a family of regulatory proteins that influence pattern formation at many levels. Their presence in skin implicates them in this important role. It seems highly likely that they will be shown to be fundamental to the development of the patterns used in diagnosing skin diseases.

Glucocorticoid effect on hair growth initiation: a reconsideration

It has been demonstrated by various workers in the past that glucocorticosteroids block hair growth. Using the mouse model for studying hair growth induction we reexamined the effect of topically applied steroids on hair growth to establish at what stage the steroid block acts. In accord with studies by others, we found that these steroids block hair growth at the point of anagen initiation, but that once the steroid applications are stopped, hair growth starts. Since steroid withdrawal alone did not induce hair growth, it is clear that these steroids do not block, either spontaneous or manipulated, hair growth induction, but they do block, the apparent next step, i.e., hair formation. Moreover, since hair growth could be induced even while the animals were being treated with the steroid, the induction step appears independent of the steroid block. These studies and those of others lead us to conclude that these steroids block the expression of hair-forming genes, but do not interfere with the signal(s) that initiates those genes. This system appears to be ideal for identifying the signals (perhaps, genes) responsible for initiating hair growth.

Ectodermal dysplasias associated with clefting: significance of scalp dermatitis

Several clinical syndromes are characterized by ectodermal dysplasia (ED) in association with clefting of the lip and/or palate. The three most commonly recognized entities are (1) the EEC syndrome (ectodermal dysplasia, ectrodactyly, cleft lip/palate); (2) the Rapp-Hodgkin syndrome with ectodermal dysplasia, cleft lip/palate, and mid facial hypoplasia; and (3) the Hay-Wells or AEC syndrome (ankyloblepharon, ectodermal defects, cleft lip/palate). The clinical characteristics of these entities as well as several less common syndromes are reviewed and summarized. The presence of scalp dermatitis in patients with the AEC syndrome and less often the Rapp-Hodgkin syndrome is emphasized.

Vitronectin: effects on keratinocyte motility and inhibition of collagen-induced motility

Epibolin, a plasma protein, was initially purified on the basis of its ability to enhance spreading of keratinocytes. It is now known that epibolin is identical to serum spreading factor, S protein, and vitronectin, and the current name for the protein is vitronectin. Studies of vitronectin on cultured keratinocytes showed that it caused spreading and epiboly but not cellular adhesion to the substratum. In studies with other types of cells, vitronectin increased migration of several types of cells in a Boyden chamber. Because some agents that enhance spreading and adhesion, such as collagen and fibronectin, also increase motility, we tested whether vitronectin increased motility of keratinocytes. By photographing and quantitating motility of keratinocytes plated on a bed of colloidal gold particles, we determined that vitronectin increased local movement of keratinocytes in a concentration-dependent fashion, resulting in clearing of gold particles in a circular pattern around the cells, but did not cause the production of tracks found in cultures plated on collagen or fibronectin. The small increases in clearing of the gold particles that occurred in the presence of vitronectin were abolished by antibody to vitronectin. Furthermore, the marked increase in motility produced by type I collagen was significantly reduced when the keratinocytes were treated with vitronectin. Antibody to vitronectin also abrogated the vitronectin-induced reduction in collagen-stimulated motility, confirming that this action was specific for vitronectin. Serum, which contains vitronectin, stimulated motility in a fashion identical to purified vitronectin, but serum lacking vitronectin was inactive. These studies show that vitronectin causes a localized increase in movement associated with spreading resulting in a halo around individual cells, that vitronectin does not enhance directional motility of keratinocytes in this assay but in contrast antagonizes such motility produced by collagen, and that vitronectin is the factor in serum responsible for this effect. The findings with vitronectin and collagen show that these agents stimulate different types of motility. The roles in wound healing of agents stimulating different types of motility are unclear and require further study.

The epidermal pentapeptide pyroGlu-Glu-Asp-Ser-GlyOH inhibits murine hair growth in vivo and in vitro

Tissue growth may be controlled by negative feedback mechanisms. Recently, a pentapeptide, pyroGlu-Glu-Asp-Ser-GlyOH ('epidermal pentapeptide', EPP), which slows the growth of mouse epidermis in vivo and of mouse keratinocytes in vitro, was isolated from mouse epidermis. Since inhibitory molecules like EPP might be part of the feedback systems underlying hair growth control, we assessed the effect of synthesized EPP on the growth of hair follicles, using rodent in vivo and in vitro assays. We report for the first time that intraperitoneally injected EPP (30 nmol/animal/day over 6 days) significantly slows the growth of hair follicles in plucking-induced anagen skin of C57 B1-6 mice (as assessed by microscopic morphometry). Using an in vitro organ culture assay, EPP inhibits the incorporation of 3H-thymidine into mouse pelage anagen follicles. That this epidermal-derived peptide affects hair growth raises the possibility that hair growth may be regulated by an inhibition/disinhibition mechanism under participation of EPP-like molecules and that the epidermis may play a role in the control of hair growth.

Epithelial growth by rat vibrissae follicles in vitro requires mesenchymal contact via native extracellular matrix

An in vitro assay utilizing the rat vibrissa anagen follicle as a model for studying the epithelial-mesenchymal interactions (EMI) in hair growth is described. Through selective disruption of the epithelial-mesenchymal interface, we investigate whether the specialized extracellular matrix (ECM) of the dermal papilla and basement membrane zone (BMZ) serves a crucial function in hair follicle EMI. Epithelial bulbs incubated intact within their follicular sheaths incorporate thymidine primarily into cells of the hair matrix and outer root sheath, as shown by autoradiography. However, after removal of its mesenchymal associations (dermal papilla and extrabulbar connective tissue), the epithelial bulb showed no incorporation. Neither externally added collagen (type I or IV) nor the basement membrane components in Matrigel could substitute for the growth supporting influence of native surrounding stroma. Mechanical separation of the bulb from the dermal papilla in the basement membrane zone inhibited thymidine incorporation by the epithelium even though mesenchyme was still in close proximity. Enzymatic digestion of the dermal papilla ECM and the basal lamina by Dispase, a fibronectinase and type IV collagenase, also inhibited bulb growth without evidence of cytotoxicity. These experiments suggest that direct epithelial to mesenchymal contact is required for the support of follicular epithelial growth in vitro and that specific ECM components, possibly fibronectin and/or type IV collagen, rather than diffusable factors alone, play a crucial role in the mechanism of hair follicle EMI. The in vitro system described here provides an alternative to developmental EMI models and may serve as a valuable tool for studying EMI in the adult mammalian organism.

Telogen skin contains an inhibitor of hair growth

We have investigated whether C57B1-6 mouse skin with all its follicles in the telogen stage of the hair cycle contains a hair-growth inhibitory activity, as opposed to skin with anagen follicles. Crude aqueous extracts of whole telogen mouse skin (TE), anagen skin (AE) or vehicle alone (V) were injected intraperitoneally into mice in which anagen had previously been induced by plucking of telogen hair follicles. Injection of TE, but not AE or V, significantly retarded the development of anagen follicles, as measured by macroscopic and quantitative microscopic hair growth parameters (skin pigmentation and thickness, appearance of trichohyaline granules) and the incorporation of tritiated thymidine into mouse skin from animals previously treated with either TE or V (skin organ culture). This inhibitory activity seemed to be localized to the epidermis and was also present in rat epidermis. We suggest that this apparently non-species-specific inhibitor present in telogen skin may play a role in regulating the hair cycle in rodents.

Nevomelanocytic proliferations in association with cutaneous malignant melanoma: a multivariate analysis

Two hundred forty-eight cases of melanoma accessioned from 1984 through 1985 were independently reviewed by a panel of dermatopathologists for the presence of nevomelanocytic proliferations in histologic contiguity with melanoma. One hundred ninety-seven cases remained in the sample for analysis after cases with insufficient histologic material and those diagnosed without primary melanoma were excluded. We found that 32.5% of melanomas (95% confidence interval, 25.9% to 39.7%) were associated with a benign or dysplastic nevus in histologic contiguity. Melanoma type and anatomic location were significant predictors of contiguous nevomelanocytic proliferations when considered alone. After adjustment, however, only melanoma type significantly predicted the presence of a contiguous histologic evidence of a precursor nevus than was nodular melanoma (odds ratio, 11.1; 95% confidence interval, 1.4 to 86.6) and were almost 22 times more likely to be associated with a nevus than was lentigo maligna melanoma (odds ratio, 21.45; 95% confidence interval, 2.8 to 162.4). This evidence supports the concept of the heterogeneity of melanoma histogenesis.

Angiogenic properties of normal and psoriatic skin associate with epidermis, not dermis

Psoriasis is a chronic inflammatory and proliferative epidermal skin disease associated with prominent new vessels in the dermis. Heretofore, unresolved was the question which skin element causes stimulation of vessel formation in this lesion: the epidermis, the dermis, vessels themselves, inflammatory cells, and so forth. It has been argued that the dermis by means of its vessels is responsible for the rapid and prominent epidermal growth and that psoriasis is simply a dermal-induced epidermal disease. Recognizing that vascular proliferations do not occur in the absence of an angiogenic stimulus we asked where in psoriatic skin is that angiogenic element found. By using the rabbit cornea angiogenic assay, the vessel-stimulating properties of epidermis and dermis (separated after cold trypsinization overnight), collected from psoriatic-plaque skin and normal skin both nonpsoriatic and psoriatic patients, were measured. The corneas were examined on days 2, 4, 8, 10, and 12 and graded from 1 to 5+ for vessel growth. Psoriatic plaque epidermis revealed a 4 to 5+ stimulus (8 of 12 corneas). Epidermis from normal subjects or from nonlesional psoriatic patient skin also revealed a 4 to 5+ stimulus (3 of 5 and 5 of 8, respectively). In no case was the dermal implant from normal (7 implants) or psoriatic patients (3 implants of lesional skin) angiogenic. The angiogenic activity of epidermis is stable to freezing and boiling. This study indicates that the vessel-stimulating properties of psoriatic and nonpsoriatic skin are associated with the epidermis and that the developing psoriatic lesion may involve complex epidermal to dermal as well as dermal to epidermal signals.

Dispase, a neutral protease from Bacillus polymyxa, is a powerful fibronectinase and type IV collagenase

Dispase, a neutral protease isolated from culture filtrates of Bacillus polymyxa, has proven to be a rapid, effective, but gentle agent for separating intact epidermis from the dermis and intact epithelial sheets in culture from the substratum. In both cases it effects separation by cleaving the basement membrane zone region while preserving the viability of the epithelial cells. Because it is not known what or where in the basement membrane zone Dispase cleaves, we set up studies to define its substrate specificity. Using purified basement membrane components and sodium dodecyl sulfate-polyacrylamide gel electrophoresis we show that Dispase cleaves fibronectin and type IV collagen, but not laminin, type V collagen, serum albumin, or transferrin. The action of Dispase on collagen appears to be selective for type IV collagen in that several stable degradation products are formed, whereas the enzyme degrades type I collagen only minimally. In newborn human skin, as seen by electron microscopy, Dispase removes the lamina densa, rich in type IV collagen, but preserves the anchoring fibrils (structures known to contain type VII collagen) and the epidermal cells. Because its action is so selective, it suggests that Dispase can serve as a powerful tool for dissecting epithelial-mesenchymal interactions.

The induction of anagen hair growth in telogen mouse skin by cyclosporine A administration

One clinical complication of immunosuppressive cyclosporine A (CsA) therapy is the stimulation of hair growth. Since few pharmacologic agents cause hypertrichosis, CsA appears particularly interesting for investigating the mechanisms which control normal hair formation. Previous investigators have shown that CsA affects the hair growth of the laboratory rat, several genetic variants of mice, as well as humans, and they have concluded that CsA influences keratinization predominantly. Using a well-defined in vivo assay which measures the induction of hair follicle growth, we report here that CsA induces resting (telogen) follicles to enter active growth (anagen) in normal laboratory mice (C57 B1-6), i.e., animals with a normal hair cycle. The experiments indicate that the rate of anagen induction is dependent on the dose, time course, and method of administration and that it may be mediated via a direct action of CsA on the skin and its appendages. These studies suggest that understanding the molecular mechanisms of CsA action on hair growth will help elucidate the mechanisms of normal anagen induction.

Malignant blue nevus. Case report and literature review

A well-documented case of malignant blue nevus is presented, along with an in-depth review of the literature. Malignant blue nevus is a rare form of malignant melanoma. A cellular blue nevus is the precursor lesion. The scalp is the most common site. The tumor often presents clinically as a progressively enlarging or multinodular blue-black lesion. The histologic pattern is fascicular dense collections of pigmented, pleomorphic spindle cells. Because of marked regional histologic variation within a malignant blue nevus, however, sampling error can cause delay in recognition of malignancy. A high clinical index of suspicion and appropriate biopsy technique are necessary to reach an early diagnosis. The most common site of metastasis of a malignant blue nevus is the lymph node. The phenomenon of benign lymph node nevus cell metastasis, which may occur with benign blue nevi, must be differentiated from a true malignant metastasis of a malignant blue nevus.

Calcinosis cutis following extravasation of calcium chloride

A 27-year-old woman with hypoparathyroidism developed multiple firm white-yellow papules along the path of an infiltrated calcium chloride intravenous infusion. A biopsy specimen obtained ten days after the extravasation revealed an urticarial reaction. A subsequent biopsy specimen, obtained 25 days after the extravasation, showed diffuse dermal calcification, confirmed by roentgenographic analysis, with incipient transepidermal elimination. A biopsy specimen obtained 40 days after the extravasation was consistent with an elimination reaction. An increase in mast cells was not noted. Electron microscopy showed mineral deposits along collagen fibrils without significant collagenous degeneration. In this report we describe a complication of intravenous calcium chloride infusion.

The angiogenic properties of the rat vibrissa hair follicle associate with the bulb

As the hair follicle is one of the most rapidly growing tissues in the body, it must be nourished by a rich blood supply. Histological studies have indicated that the number of vessels about a growing follicle exceeds that about a resting follicle, so we postulated that the hair follicle might provide its own angiogenic stimulus during certain phases of its growth. Reported here are experiments testing the angiogenic properties of the growing (anagen) hair follicle. Using the rabbit corneal pocket angiogenesis assay and cycled anagen rat vibrissae hair follicles, we found that the mesenchymal dermal papilla had no angiogenic properties, but the anagen bulb was angiogenic. These findings suggest a mechanism for the cycling of hair follicles and an example of normal epithelium to mesenchyme interactions.