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SummaryThe climbing genusGouania(Rhamnaceae) is revised in western Malesia. Five species are recognised for the Philippines and Sundaland using morphological evidence, including a new species from the Philippines:Gouania longipedunculata. A taxonomic treatment, including a preliminary IUCN conservation status assessment, is presented for each species.

Primary cicatricial alopecias (PCAs) are a group of skin diseases in which there is progressive and permanent destruction of hair follicles followed by replacement with fibrous tissue. Unfortunately, by the time patients seek clinical evaluation of their hair loss, the skin is already inflamed and/or scarred, so there is little hope for a return to their normal hair growth pattern. Clinical and basic science investigations are now focusing on three forms of human PCA: lichen planopilaris (LPP), frontal fibrosing alopecia (FFA) and central centrifugal cicatricial alopecia (CCCA). Transcriptome, lipidome and other new technologies are providing new insight into the pathogenesis of some of these diseases that are being validated and further investigated using spontaneous and genetically engineered mouse models.

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.

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.

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.

Androgenetic alopecia In men, or male pattern baldness, is recognized increasingly as a physically and psychologically harmful medical condition that can be managed effectively by generalist clinicians. This article discusses the clinical manifestations, epidemiology, physical and psychosocial importance, pathophysiology, diagnosis, and management of androgenetic alopecia in men. Androgenetic alopecia affects at least half of white men by the age of 50 years. Although androgenetic alopecia does not appear to cause direct physical harm, hair loss can result in physical harm because hair protects against sunburn, cold, mechanical injury, and ultraviolet light. Hair loss also can psychologically affect the balding individual and can Influence others' perceptions of him. A progressive condition, male pattern baldness is known to depend on the presence of the androgen dihydrotestosterone and on a genetic predisposition for this condition, but its pathophysiology has not been elucidated fully. Pharmacotherapy, hair transplantation, and cosmetic aids have been used to manage male pattern baldness. Two US Food and Drug Administration-approved hair-loss pharmacotherapies-the potassium channel opener minoxidil and the dihydrotestosterone synthesis inhibitor finasteride--are safe and effective for controlling male pattern baldness with long-term daily use. Regardless of which treatment modality is chosen for male pattern baldness, defining and addressing the patient's expectations regarding therapy are paramount in determining outcome.

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.

Background: Primary cicatricial alopecias encompass a group of disorders characterized by permanent destruction of the hair follicle. The varied clinical features and differences in terminology have led to difficulties in defining consistent clinicopathologic correlation. Objective: We sought clinicopathologic correlation of 6 clinically distinct primary cicatricial alopecias: lichen planopilaris, frontal fibrosing alopecia, pseudopelade (Brocq), central centrifugal alopecia, folliculitis decalvans, and tufted folliculitis. Methods: We conducted prospective and blinded histopathologic evaluation of clinically typical primary cicatricial alopecias. Biopsy specimens were taken from early affected scalp lesions and paired with samples from clinically unaffected areas in the same patient. Results: The lymphocytic and neutrophilic groups were readily distinguished histologically. However, within the two groups clinically distinct primary cicatricial alopecias could not be distinguished with current histopathologic techniques. Conclusion: A descriptive, standardized histopathologic reporting of follicular architecture, type, location, and extent of the inflammatory infiltrate, and presence or absence of sebaceous glands, may be of greatest value in guiding the treatment of patients with primary cicatricial alopecias. ( J Am Acad Dermatol 2005;52:637-43.)

Plucked (pk) is an autosomal recessive mouse mutation with a hair phenotype that arose spontaneously in the DBA/2J strain. Histological studies indicate that adult pk mutant mice lose truncal hair because of the scarring of follicles due to an apparent obstruction of the outward movement of the hair shaft within the follicular canal. We mapped the pk mutant phenotype to a 1.1 cM region of chromosome 18 (between 6.6 and 7.7 cM from the centromere) using 370 backcross progeny. Within this region, among others, are genes for desmosome cadherins. Desmosome cadherins are interesting candidates because of their critical roles for cell–cell adhesion in epidermal function. Northern Blot analysis of wild-type and pk mutant mice indicates that expression of both desmoglein 1 (Dsg1) and desmoglein 3 (Dsg3) is up-regulated in the skin of mutant pk mice.

The 2011 Cicatricial Alopecia Symposium* was attended by approximately 90 members of the scientific community representing academia, industry, and government. The program was held over 2 days and included three keynote talks and six sessions: (i) Bench: “Mechanisms of inflammation”; (ii) Bedside: “Disease Presentation and Epidemiology”; (iii) Bench: “Nuclear Receptors and Lipids in Skin and Hair Disease”; (iv) Bedside: “Current and Emerging Therapies for Cicatricial Alopecia”; (v) Identifying Translational Opportunities in Cicatricial Alopecia; and (vi) Stem cells, Cicatricial Alopecia, and Hair Follicle Regeneration. In addition to major talks by invited speakers, the meeting included short talks selected from submitted abstracts, followed by panel discussions. The symposium culminated in a workshop composed of small discussion groups, each focusing on specific research questions and priorities.

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.

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.

Summary The asebia (ab) mutation in the mouse is an autosomal recessive trait with hypoplastic sebaceous glands. As a first step toward cloning the ab gene, we report here the genetic mapping of the ab locus with respect to Chromosome 19 microsatellite markers. 644 backcross progeny were generated by mating (CAST/EiJ × DBA/1LacJ- ab 2J /ab 2J ) F 1 heterozygous females and parental ab 2J /ab 2J mutant males. Our results located the ab gene to an interval of 1.6 cM on mouse Chromosome 19 defined by flanking markers D19Mit11 and D19Mit53/D19Mit27 , and identified a tightly linked polymorphic marker, D19Mit67, that co-segregates with the mutation in the backcross progeny examined. This places ab locus 4 cM distal to its present position as indicated in Mouse Genome Database at The Jackson Laboratory. We have also mapped a yeast artificial chromosome (YAC) contig in this locus interval which suggests the ab interval to be less than one megabase of DNA.

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.

A critical step in the synthesis of unsaturated fatty acids is catalysed by stearoyl-CoA desaturase (Scd). To determine the regulation of human Scd, we characterized the gene and its transcripts. Screening a human keratinocyte cDNA library and analysis of 3ʹ-RACE (rapid amplification of cDNA ends) products from various tissues yielded a 5.2 kb cDNA encoding a 359 amino acid protein with a calculated molecular mass of 41.5 kDa. Analysis of 3ʹ-RACE products suggested that alternative usage of polyadenylation sites generates two transcripts of 3.9 and 5.2 kb, a result consistent with Northern analysis. Southern analysis demonstrated the existance of two SCD loci in the human genome. Chromosomal mapping localized one locus to chromosome 10, and the second locus to chromosome 17. Characterization of genomic clones isolated from chromosome-specific libraries revealed that only the locus on chromosome 10 contained introns. Sequence analysis of the intron-less locus displayed multiple nucleotide insertions and deletions, as well as in-frame stop codons. Reverse transcriptase-PCR analysis performed with primers specific to the intron-less locus failed to produce a PCR product from brain, liver and skin RNA, indicating that the locus on chromosome 17 is most likely a transcriptionally inactive, fully processed pseudogene. These results suggest strongly that there is one structural SCD gene in the human genome, and that it generates two transcripts by use of alternative polyadenyation sites. Although the primary sequence and intron-exon structure of SCD is phylogenetically conserved, divergence between rodent and human is seen in the number of SCD genes and in the generation of alternative transcripts, suggesting a species-specific component of SCD regulation and function.

From Duke University Medical Center, Durhama; University of Minnesota, Minneapolisb; Pontefract General Infirmaryc; University of California at San Franciscod; Northwest Cutaneous Research Specialists, Portlande; The University of British Columbia, Vancouverf; and Johnson & Johnson, Skin Biology Research Center, Skillman.g Reprint requests: Elise A. Olsen, MD, Professor of Medicine, Duke University Medical Center, Box 3294, Durham, NC 27710. J Am Acad Dermatol 1999;40:242-6. *Developed from the Alopecia Areata Consensus meeting sponsored by the National Alopecia Areata Foundation at the First Tricontinental Meeting of the Hair Research Societies, Brussels, Belgium, Oct 8, 1995. Participants are listed at the end of the guidelines. Copyright © 1999 by the American Academy of Dermatology, Inc. 0190-9622/99/$8.00 + 0 16/1/95940 I. PURPOSE To establish criteria for selecting and assessing subjects for both clinical and laboratory studies of alopecia areata, thereby facilitating collaboration, comparison of data, and the sharing of patient-derived tissue II. DEFINITION OF ALOPECIA AREATA Alopecia areata is a dermatologic disease characterized in its limited form by circumscribed round or oval patches of alopecia with well-demarcated borders between normal and affected scalp. There is no scale or induration of the scalp and no loss of follicular markings. Disease extent may progress from this limited form to complete loss of hair on the scalp and/or body. III. INCLUSION CRITERIA These guidelines apply only to terminal hair loss or growth on the scalp. These guidelines focus on the major forms of alopecia areata (patchy alopecia areata, alopecia totalis, and alopecia universalis) and their expression on the scalp. The terms alopecia totalis and alopecia universalis imply 100% scalp hair loss. Areas of hair loss other than on the scalp may be assessed and documented in the data collected on each patient. (See Section IV. B) IV. CRITERIA FOR MEASURING EXTENT OF INVOLVEMENT Those data items in boldface type should be filled out in toto. Those data items not in bold are optional and can be filled out as desired by the investigator. A. The proportion of scalp involvement is determined by dividing the scalp into 4 quadrants and estimating the percentage of the scalp surface that all the alopecic areas would occupy if placed together. The following groups will be used: S: Scalp hair loss _____S0 = No hair loss _____S4 = 76%-99% hair loss _____S1 = ≤ 25% hair loss _____a = 76%-95% hair loss _____S2 = 26%-50% hair loss _____b = 96%-99% hair loss _____S3 = 51%-75% hair loss _____S5 = 100% hair loss B. Other areas of alopecia or involvement by alopecia areata may be noted: B: Body hair loss _____B0 = No body hair loss _____B2 = 100% body (excluding scalp) hair loss _____B1 = Some body hair loss N: Nail involvement _____N0 = No nail involvement _____N1 = Some nail involvement _____a. Twenty-nail dystrophy/trachyonychia (must be all 20 nails) SPECIAL ARTICLE

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.

Programmed cell death is central to hair biology, as the hair follicle undergoes cycles of growth (anagen), regression (catagen), and rest (teIogen). 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 tins 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-β was expressed immediately before catagen; therefore, it might be involved in the early signaling of this process. Tumor necrosis factor-β 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.

Insig-1 and Insig-2, two closely related proteins, are essential for feedback inhibition of cholesterol biosynthesis. Here, we characterized a line of epidermal-specific, Insig-double knockout (Epi-Insig-DKO) mice lacking both Insigs in epidermis. At birth, Epi-Insig-DKO mice were indistinguishable from control littermates, but thereafter they failed to thrive and died before 6 weeks of age. By 14 days of age, 100% of Epi-Insig-DKO mice exhibited defects in hair growth along with other skin abnormalities, including hyperkeratosis. Hair follicles in Epi-Insig-DKO mice developed normally through postnatal day 7, but they failed to progress to later stages and thus exhibited defects in postnatal hair cycling. Insig deficiency caused a marked buildup of cholesterol precursors in skin associated with a marked increase in 3-hydroxy-3-methylglutaryl coenzyme A reductase protein. Topical treatment of Epi-Insig-DKO mice with simvastatin, an inhibitor of reductase, reduced sterol precursors in skin and corrected the hair and skin defects. We conclude that Insig deficiency in skin causes accumulation of cholesterol precursors, and this impairs normal hair development. These findings have implications for several human genetic diseases in which mutations in cholesterol biosynthetic enzymes lead to accumulation of sterol precursors and multiple cutaneous abnormalities.

Considered here is the rationale for cellular engineering of the hair follicle: the cells needed the mechanisms of hair regeneration from dissociated cells, current successes, immediate challenges, and future vision. As evidenced by its growth cycle, the hair follicle has the ability to regenerate. This is the property and the opportunity for the cellular engineer to reconstruct hair follicles where needed. The field has demonstrated great success with laboratory mammals. Translating that success to human adult cells, and thus the clinic, is the current challenge to our mechanistic understanding and application.

We have refined the position of asebia locus by genotyping DNA from more than 600 backcross mice derived from asebia mouse and a genetically unrelated strain. One of the candidate genes in the locus is stearoyl-CoA desaturase (SCD). Previously two members of this gene family, namely SCD1 and SCD2, have been described. We have found, for the first time, that these SCD genes are expressed in skin. Moreover, we have identified a third species of SCD in the mouse skin. The most prominent SCD species is SCD1 in the mouse skin. The implications of this gene family to skin are discussed.

Hair follicle regeneration involves epithelial-mesenchymal interactions (EMIs) of follicular epithelial and dermal papilla (DP) cells. Co-grafting of those cellular components from mice allows complete hair reconstitution. However, regeneration of human hair in a similar manner has not been reported. Here, we investigated the possibility of cell-based hair generation from human cells. We found that DP-enriched cells (DPE) are more critical than epidermal cells in murine hair reconstitution on a cell number basis, and that murine DPE are also competent for hair regeneration with rat epidermal cells. Co-grafting of human keratinocytes derived from neonatal foreskins with murine DPE produced hair follicle-like structures consisting of multiple epidermal cell layers with a well-keratinized innermost region. Those structures expressed hair follicle-specific markers including hair keratin, and markers expressed during developmental stages. However, the lack of regular hair structures indicates abnormal folliculogenesis. Similar hair follicle-like structures were also generated with cultured human keratinocytes after the first passage, or with keratinocytes derived from adult foreskins, demonstrating that epidermal cells even at a mature stage can differentiate in response to inductive signals from DP cells. This study emphasizes the importance of EMI in follicular generation and the differentiation potential of epidermal keratinocytes.

Pattern recognition is at the heart of clinical dermatology and dermato- pathology. 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 sym- metry-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 clin- ical 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 encour- age more systematic interdisciplinary research efforts geared at unraveling the many unsolved, yet utterly fascinating mysteries of dermatological pattern forma- tion. In short: never a dull pattern!

On 17 October 2005, a research colloquium* was held on the National Institutes of Health campus to review the primary cicatricial alopecias (CICALs) — their etiology, their pathogenesis, and directions for future research. In this rare, but important, group of inflammatory hair disorders, the hair follicle and its sebaceous gland are replaced by fibrous tissue, leading to permanent destruction of the pilosebaceous unit. The cause and pathogenesis of these diseases are unknown. Although treatments may arrest signs and symptoms of the CICALs, they do not usually influence the underlying disease process and may not arrest progression of the disease. Participants came from around the world. The meeting was organized into major topics: Clinical and Histological Presentation of CICAL in Humans and Animal Models; Pilosebaceous Apparatus Growth and Structure; Mechanisms; and, finally, Hypotheses and Research Directions. S. Katz, director of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (Bethesda, MD), opened the meeting with comments underscoring the paucity of epidemiological, clinical, and laboratory studies of these follicular diseases and the therapeutic challenge they present. P. Mirmirani (Case Western Reserve University, Cleveland, OH) the meeting organizer, put a challenge to the attendees to consider, in light of the colloquium’s presentations and discussions, (1) what mechanistic directions might be indicated at this time, and (2) what steps should be taken to improve our understanding and therapy. The clinical and histological characteristics of the CICALs were reviewed by V. Price (University of California, San Francisco). The CICALs have been divided into lymphocytic and neutrophilic subtypes based on pathological changes. Price emphasized that the nosology is difficult because the histological findings do not distinguish the various clinical forms beyond separating the predominantly lymphocytic group from the predominantly neutrophilic group. As a rough guide to therapy, the former is treated with immunomodulating agents and the latter with antimicrobials; however, even the response to treatment is not always predicted by the histology. The concept that the CICALs may be a final common pathway for a number of different processes was raised. Not only is it unclear whether the follicle injury is due to intrinsic or extrinsic factors, but it is also unclear whether the fibrosing events are primary or secondary to inflammation. Knowledge of these rare disorders is further confounded by geographic and racial factors that influence epidemiology. The importance of estimating the true incidence of CICAL was noted. Barriers to achieving this include a lack of the expertise necessary to make an accurate diagnosis and the poor clinicopathological correlation. Price stressed the need to distinguish clinical variants with specific chemokines, and molecular markers gleaned from microarray-based approaches. J.T. Headington (University of Michigan, Ann Arbor, retired) presented an overview of mechanistic, nosological, and clinical aspects of these diseases. He indicated that pathogenic mechanisms in CICALs involve a common pathway that leads to irreversible damage of both the hair matrix and the follicular stem cells, resulting in generic “cirrhosis” of the scalp. He questioned how and why lymphocytes or neutrophils effect destruction of follicular units and whether these infiltrates are just late, secondary responses to some other event. A comprehensive review of animal models — spontaneous and induced — that manifest CICAL was presented by J. Sundberg (The Jackson Laboratory, Bar Harbor, ME). He pointed out the numerous examples of correlation between mouse and human hair disorders. Two mouse models with mutations of genes expressed in the sebaceous gland, the stearyl-coenzyme A desaturase gene and gasdermin 3 (a transcription factor), exhibit histological changes mirroring those in human lymphocytic CICALs. These studies implicate the sebaceous gland as the first injury site in the pathogenesis of mouse CICAL. CICAL in C57BL/6 substrains shows progressive hair loss over the dorsum with changes reminiscent of central centrifugal CICAL. This appears to be a complex polygenic disorder influenced by diet and environment. An unresolved issue is how to manipulate mouse skin to mimic potential extrinsic factors that may be related to development of CICAL (for example, heat and chemical injury). The role of cutaneous stem cells in the evolution of CICALs was presented by G. Cotsarelis (University of Pennsylvania, Philadelphia). Reviewing over a decade of work on the follicular stem cell, Cotsarelis pointed out that epidermal stem cells and hair follicle stem cells are distinct populations. Recent studies using lineage analysis

Hair follicle formation and cycling involve extensive and continuous interactions between epithelial and mesenchymal components. A system for rapidly and reproducibly generating hair follicles from dissociated epithelial and mesenchymal cells is described here. The system serves both as a tool for measuring the trichogenic property of cells and as a tool for studying the mechanisms that dissociated cells use to assemble an organ. In this system, hair follicles develop when dissociated cells, isolated from newborn mouse skin, are injected into adult mouse truncal skin. This morphogenetic process involves the aggregation of epithelial cells to form clusters that are sculpted by apoptosis to generate "infundibular cysts". From the "infundibular cysts", hair germs form centrifugally followed by follicular buds and then pegs that grow asymmetrically to differentiate into cycling mature pilosebaceous structures. Marker studies correlate the molecular differentiation of these follicles with in situ systems. This study suggests that the earliest phase of a developing epithelial-mesenchymal system--even from dissociated cell preparations--requires an epithelial platform.

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.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.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.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.

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-β, 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.

A spontaneous, autosomal, recessive mouse mutation exhibiting mild scaly skin, progressive scarring alopecia, slightly runted growth, and photophobia arose at The Jackson Laboratory in 1993 in the inbred mouse strain DBA/1LacJ. Because this mutant mouse showed genetic, anatomical, and laboratory similarities to the asebia mutation, crosses were done between the new mutant and mice carrying the asebia-J allele. Because the F1 offspring were affected, indicating the two mutants were allelic, the new mutation was named asebia-2J. Careful histological analysis of skin development of mice homozygous and heterozygous for either asebia-J or asebia-2J revealed that both types of mutant mice are very similar regardless of their background. Notable histopathological features of mice homozygous for either allele included extreme sebaceous gland hypoplasia, abnormally long anagen follicles, retained inner root sheath, hair fiber perforation of the anagen follicle base, and progressive follicular replacement by scarring. In this article we present a new pathogenetic hypothesis based on the importance of the sebaceous gland in hair fiber sheath dissociation: in the absence of a functional sebaceous gland the hair follicle is destroyed. The cutaneous pathology of this mutant mouse underscores the importance of the sebaceous gland to follicular biology and presents an animal model for studying the human scarring alopecias, which characteristically begin with sebaceous gland ablation.

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.

A major challenge to the study of hair follicle growth is an appropriate assay system. Because equine mane follicles are large and noncurved, enabling easy dissection; are readily accessible from a single defined source; and possess a long anagen growth phase, we initiated a study of them in culture. As in our previous studies of human and sheep follicles (Dev Biol 165:469, 1994), we found in this system that transection level dictates the pattern of follicle growth in vitro: follicles transected below the sebaceous gland show a type 1 growth pattern (the shaft grows out with an adherent sheath), while nontransected follicles show a type 2 growth pattern (a naked shaft grows out lacking a sheath). In the present study, we searched for compounds that might influence type 1 or type 2 patterns of growth. We found that 13-cis retinoic acid induced, in a concentration-dependent fashion, a type 1-like pattern of growth under conditions for which a type 2 pattern was expected. All-trans-retinoic acid, SR11237 (a synthetic retinoid X receptor-specific ligand), and meta-carboxy-TTNPB (and inactive synthetic retinoid) did not have these properties. We hypothesize that sheath growth?processing is mediated by the follicle at the level of the sebaceous gland, or by the sebaceous gland itself, and that persistence of the follicle sheath about the outgrowing shaft in vitro (i) in the physical absence of the sebaceous portion of the follicle, or (ii) in the presence of 13-cis-retinoic acid, is due to the reduced expression of a factor that regulates important shaft sheath interactions.

Cicatricial alopecia is an enigmatic group of hair disorders linked by the potential permanent loss of scalp hair follicles in involved areas. Progress in our understanding and treatment of these disorders has been stymied by the lack of clear diagnostic criteria for the current terms used to describe the various hair loss entities. Since all of these conditions evolve as the hair is destroyed or replaced, diagnosis is further made difficult by a lack of clinical and pathologic “snapshots” over the evolution of each disorder. Without some acceptance of general clinical and histological presentations in the early, mid and late stage of these disorders, one cannot begin to explore ways to make the diagnosis at a very early stage before significant follicular destraction has occurred (making the clinical diagnosis obvious) and when the damage is potentially repairable or progression preventable.

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.

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. At that time with the increased investigative activity dedicated to this system we would hope to be able to reorganize the presentation towards a mechanistic overview: to begin to describe in detail where in each layer the molecule is found, when it is expressed, what function it serves in its site of location, and its role in follicular dynamics.

Summary 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.

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.

Background: The diagnostic criteria for the histopathologic recognition of the dysplastic nevus are defined, but difficult to apply in practice. However, the use of skin biopsy is on the increase to search for this nevus because of a possible role in melanomagenesis. Objective: The aim was to determine the degree of observer reproducibility in the detection of histologic nevomelanocytic dysplasia as measured across multiple observers and to test whether each observer was precise over a wide sample population, A second aim was to gain some measure of the threshold a person has for such lesions. Methods: Histologic specimens from 50 coded nevomelanocytic tumors, which included a group of dysplastic nevi, were independently read by five observers in a blinded fashion. At study completion, the same 50 cases were read again by a melanoma reference pathologist and results analyzed by Cohen's k to assess agreement and interobserver variation. Results: Corrected rates of agreement for dysplastic nevi ranged from 0.32 to 0.71. Conclusion: Continued study and experience are required for precision and reproducibility in the histologic recognition of dysplastic nevi.

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.

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.