Skin stem cell hypotheses and long term clone survival--explored using agent-based modelling.

Epithelial renewal in skin is achieved by the constant turnover and differentiation of keratinocytes. Three popular hypotheses have been proposed to explain basal keratinocyte regeneration and epidermal homeostasis: 1) asymmetric division (stem-transit amplifying cell); 2) populational asymmetry (progenitor cell with stochastic fate); and 3) populational asymmetry with stem cells. In this study, we investigated lineage dynamics using these hypotheses with a 3D agent-based model of the epidermis. The model simulated the growth and maintenance of the epidermis over three years. The offspring of each proliferative cell was traced. While all lineages were preserved in asymmetric division, the vast majority were lost when assuming populational asymmetry. The third hypothesis provided the most reliable mechanism for self-renewal by preserving genetic heterogeneity in quiescent stem cells, and also inherent mechanisms for skin ageing and the accumulation of genetic mutation.

Skin differences based on age and chronicity of ultraviolet exposure: results from a gene expression profiling study.

BACKGROUND: Skin ageing represents an inevitable physiological consequence of getting older but the impact on personal health and wellbeing can be significant, and therefore considerable efforts have been made to understand the biology and pathophysiology of skin ageing to try to identify new targets that might offer therapeutic intervention and prevention. OBJECTIVES: This study was designed to identify differences at the gene expression level between young and old, sun-exposed and sun-protected skin. METHODS: We generated transcriptomic data from young and old skin from sun-exposed and sun-protected sites (10 samples of each) using HG-U133 Plus 2.0 Affymetrix GeneChips. The data were analysed using hierarchical clustering, theme analysis and interaction mapping to identify regulated pathways, processes and potential targets for therapy. RESULTS: With 54,613 probe sets on the GeneChip, 2731 significant differences would be expected by chance (at P = 0·05), but we noted that 13,640 probe sets were significantly different comparing young arm skin vs. older arm skin (photoageing), and 7215 probe sets were significant for the young buttock vs. older buttock comparison (intrinsic ageing). In both types of ageing there was reduced expression of many genes implicated in lipid biosynthesis and epidermal differentiation with functional relevance to skin barrier integrity and maintenance. Increased expression of genes contributing to oxidative stress and decreased expression of antioxidant defences were also common to both types of ageing. Differences between intrinsic ageing and photoageing were mainly noted in extracellular matrix gene expression with reduced expression of interstitial collagen genes in intrinsic ageing and increased expression of elastic tissue genes in photoageing. CONCLUSIONS: Collectively, the data identified new biomarkers of aged skin, particularly involving abnormalities of proteases, matrix proteins and inflammation. These findings offer the prospect of new and more specific targets for therapeutic development based on an improved understanding of the biology of skin ageing.

Xenobiotic metabolism gene expression in the EpiDermin vitro 3D human epidermis model compared to human skin.

There is an urgent need to validate in vitro human skin models for use in safety testing. An important component of validation is characterizing the metabolizing capacity of these models. We report comparison of the expression of 139 genes encoding xenobiotic metabolizing enzymes in the EpiDerm model and human skin. In microarray analysis, the expression of 87% of the genes was consistent between the EpiDerm model and human skin indicating the presence of similar metabolic pathways suggesting commonality in function. Analysis of EpiDerm models constructed from four donors showed highly comparable expression of xenobiotic metabolizing genes demonstrating reproducibility of the model. Overall, the expression of Phase II enzymes appeared to be more pronounced in human skin and the EpiDerm model than that of Phase I enzymes, consistent with the role of skin in detoxification of xenobiotics. Though the basal expression of CYPs in particular was low in EpiDerm, significant induction of CYP1A1/1B1 activity was observed following treatment with 3-methylcholanthrene. These results indicate that the xenobiotic metabolizing capacity of the EpiDerm model appears to be representative of human skin. Models such as EpiDerm provide a valuable in vitro approach for evaluation of metabolism and toxicity of cutaneous exposures to xenobiotics.

Tg.AC genetically altered mouse: assay working group overview of available data.

In a Government/Industry/Academic partnership to evaluate alternative approaches to carcinogenicity testing, 21 pharmaceutical agents representing a variety of chemical and pharmacological classes and possessing known human and or rodent carcinogenic potential were selected for study in several rodent models. The studies from this partnership project, coordinated by the International Life Sciences Institute, provide additional data to better understand the models' limitations and sensitivity in identifying carcinogens. The results of these alternative model studies were reviewed by members of Assay Working Groups (AWG) composed of scientists from government and industry with expertise in toxicology, genetics, statistics, and pathology. The Tg.AC genetically manipulated mouse was one of the models selected for this project based on previous studies indicating that Tg.AC mice seem to respond to topical application of either mutagenic or nonmutagenic carcinogens with papilloma formation at the site of application. This communication describes the results and AWG interpretations of studies conducted on 14 chemicals administered by the topical and oral (gavage and/or diet) routes to Tg.AC genetically manipulated mice. Cyclosporin A, an immunosuppresant human carcinogen, ethinyl estradiol and diethylstilbestrol (human hormone carcinogens) and clofibrate, an hepatocarcinogenic peroxisome proliferator in rodents, were considered clearly positive in the topical studies. In the oral studies, ethinyl estradiol and diethylstilbestrol were negative, cyclosporin was considered equivocal, and results were not available for the clofibrate study. Of the 3 genotoxic human carcinogens (phenacetin, melphalan, and cyclophosphamide), phenacetin was negative by both the topical and oral routes. Melphalan and cyclophosphamide are, respectively, direct and indirect DNA alkylating agents and topical administration of both caused equivocal responses. With the exception of clofibrate, Tg.AC mice did not exhibit tumor responses to the rodent carcinogens that were putative human noncarcinogens, (di(2-ethylhexyl) phthalate, methapyraline HCl, phenobarbital Na, reserpine, sulfamethoxazole or WY-14643, or the nongenotoxic, noncarcinogen, sulfisoxazole) regardless of route of administration. Based on the observed responses in these studies, it was concluded by the AWG that the Tg.AC model was not overly sensitive and possesses utility as an adjunct to the battery of toxicity studies used to establish human carcinogenic risk.

The relationship between command hallucinations and violence.

OBJECTIVE: The purpose of this study was to describe the relationship between command hallucinations and violent behavior. METHODS: One hundred and three psychiatric inpatients completed measures of command hallucinations, other psychotic symptoms, violent behavior, and social desirability response biases. RESULTS: Thirty percent of the patients reported having had command hallucinations to harm others during the last year, and 22 percent of the patients reported they complied with such commands. Logistic regression analyses suggested that patients who experienced command hallucinations to harm others were more than twice as likely to be violent, even when the analysis controlled for demographic variables, history of substance abuse, and social desirability response biases. CONCLUSIONS: The results support the clinical utility of asking about command hallucinations when assessing the risk of violence in patients with major mental disorders.

The relationship between patients' gender and violence leading to staff injuries.

OBJECTIVE: Although recent research has found similar rates of violence by female and male patients who have serious mental disorders, it is less clear whether violence by female patients is as likely to result in injury as violence by male patients. This study examined the relationship between violent patients' gender and injury to staff members on an inpatient unit. METHODS: All injuries to staff caused by violent behavior by patients on a locked university-based short-term inpatient unit were identified in a search of institutional records from October 1988 to June 1999. We reviewed the medical charts of the 76 patients who injured staff members to compare their demographic and clinical characteristics with those of 314 patients hospitalized during the same period who did not injure staff. RESULTS: Nearly half of the injuries (45 percent) were caused by female patients. Moreover, the proportion of injuries caused by female and male patients was similar to the proportion of females and males in the comparison group. Multivariate logistic regression analysis showed that patients' gender was not associated with injury to staff, even when the analyses controlled for other correlates of violence such as history of violence, violent thought content expressed in the admission mental status examination, and history of noncompliance with medication. CONCLUSIONS: The findings suggest that injuries to staff members on a unit treating both men and women are as likely to be caused by violence by female patients as by male patients. When a female patient exhibits signs of an elevated risk of violence, the significance of that risk should not be discounted on the basis of her gender.

Resource document on mandatory outpatient treatment.

Mandatory outpatient treatment, or outpatient commitment, refers to court-ordered treatment for patients who suffer from severe mental illness and who are unlikely to be compliant with such treatment without a court order. Many states already have commitment statutes that permit mandatory outpatient treatment, and others are considering enacting new legislation or amending existing statutes. This Resource Document was prepared under the auspices of the American Psychiatric Association's Council on Psychiatry and Law to provide information to those who are drafting mandatory outpatient treatment legislation. It begins with a review of the history of mandatory outpatient treatment and recent empirical findings, followed by a detailed discussion of the salient issues in mandatory outpatient treatment. The document concludes with a statement of recommendations concerning key provisions in statutory schemes of mandatory outpatient treatment programs. This Resource Document endorses the view that mandatory outpatient treatment can be a useful intervention for a small subset of noncompliant patients with severe and chronic mental illness who go in and out of psychiatric hospitals through the so-called "revolving door."

Relevance of interrater agreement to violence risk assessment.

This study considered whether assessments of violence risk in which 2 clinicians reach similar conclusions are more accurate than the conclusions of either clinician alone when their assessments disagree. One hundred ten physicians and 44 nurses estimated the probability of physical assault of 478 patients admitted to a short-term locked psychiatric inpatient unit. The level of assessed risk showed a substantial correspondence with the likelihood of later violence when the physician and nurse ratings were highly concordant. As the extent of agreement between the physician and nurse ratings decreased, the strength of the association between the risk assessments and the occurrence of violence decreased accordingly.

Are the mentally ill dangerous?

The author reviews studies that address the question, "Are the mentally ill dangerous?" She points out that as psychiatrists, we have the responsibility of evaluating the mentally ill and making judgments about their dangerousness that may restrict their civil liberties. Therefore, the more practical question for us is: "Which mentally ill, under what circumstances, are dangerous?" She discusses data from her research group and others that show that short-term predictions of violence can be relatively accurate, that we are better at predicting violence for some patients than for others, that specific symptom patterns in the acute phase of illness are related to violent acts, that the most likely victims of violence by decompensating psychiatric patients are caretakers rather than strangers, and that a history of violence, co-morbid substance abuse, and treatment noncompliance are related to a higher risk of violence in psychiatric patients.

Ultraviolet B-induced squamous epithelial and melanocytic cell changes in a xenograft model of cancer development in human skin.

We previously demonstrated that precancers (actinic keratoses and dysplasias) and squamous cell carcinomas (SCCs) develop in one quarter of human neonatal foreskins grafted onto recombinase-activating gene-1-knockout mice treated once with 7,12-dimethylbenz[a]anthracene (DMBA) followed by chronic intermediate-range ultraviolet (UV) B light irradiation. The goals of this study were to determine if a longer UVB exposure followed by further observation would increase the number of precancers and invasive cancers and to evaluate whether this model results in changes in p53 expression and cell proliferation similar to those seen in sun-damaged normal skin, actinic keratoses, and SCCs. The treatment consisted of a single dose of DMBA followed by 500 J/m2 UVB radiation administered three times weekly for at least 5 mo. Histologic changes (cysts, hyperplasias, precancers, and/or invasive cancers) were seen in 24 of 25 treated xenografts but not in controls. Ten of 25 grafts (40%) had two or more histological changes, and two human SCCs developed. After seven or more months of UV exposure and a total time from DMBA treatment to killing of 12-18 mo, 83% (15 of 18) of specimens developed squamous precancer or SCC of human origin, and 44% (eight of 18) developed melanocytic hyperplasia or melanoma. The change from moderate dysplasias to SCC required longer UV exposure (median, 11 mo), and 5 mo more observation than did the development of mild dysplasias (median UV exposure, 7 mo; median DMBA to death time, 12 mo). There was a direct correlation between both p53 expression and cell proliferation and the degree of histologic alteration both in squamous epithelial and melanocytic cells.

Squamous cell hyperplastic foci: precursors of cutaneous papillomas induced in SENCAR mice by a two-stage carcinogenesis regimen.

We have conducted a series of experiments to characterize the lesions that are precursors of cutaneous papillomas in SENCAR mice initiated with 7,12-dimethylbenz(a)anthracene (DMBA) and promoted with 12-O-tetradecanoylphorbol-13-acetate (TPA). The first grossly detectable lesions at sites where papillomas subsequently developed were papules, slightly raised areas of skin ranging in diameter from 0.25 to approximately 1.5 mm. Papules were first detected in DMBA-initiated mice 21 days after the start of dosing with TPA. Of 78 DMBA/TPA-induced papules tracked during 15 weeks of TPA treatments, 68% progressed to papillomas, 9% persisted as papules, and 22% completely regressed. Histological evaluation of serial sections of 69 DMBA/TPA-induced papules revealed that they were focal hyperplastic lesions that we refer to as squamous cell hyperplastic foci (SCHF). These hyperproliferative lesions appeared to progress through two distinct stages. Stage I SCHF were characterized as regular hyperplastic foci involving the interfollicular epidermis and the outer root sheaths of 1 or more hair follicles down to the level of the sebaceous glands. Stage II SCHF were foci of irregular epithelial hyperplasia with increased fibrovascular stroma and involved from 3 to >10 hair follicles. Prominent dilated capillaries and inflammatory cell infiltrates were frequently associated with both stage I and II SCHF. Ha-ras gene codon 61 mutations were detected in 7 of 10 stage I SCHF and 13 of 14 stage II SCHF microdissected from histological sections and 7 of 7 of whole papules by mutation-specific PCR analysis. These data provide molecular evidence that SCHF are foci of initiated cells. Further study of these lesions may contribute to more fully defining the sequence of molecular and cellular changes necessary for tumorigenesis in mouse skin. SCHF may also have utility as early indicators of potential skin tumorigenicity in cancer bioassays.

Management of threats of violence under California's duty-to-protect statute.

OBJECTIVE: This is the first study to assess clinical practices under one of the new duty-to-protect statutes, some version of which has been passed in many states. In 1985, California enacted a statute enabling psychotherapists to limit their liability when a patient makes a serious threat of violence by 1) making reasonable efforts to warn the victim of the threat and 2) notifying local police. METHOD: The authors examined all duty-to-protect notifications over a 5-year period in San Francisco by reviewing police and court records. RESULTS: Police received only 337 notifications, typically made by nondoctoral staff members at public facilities such as psychiatric hospitals and crisis clinics. Patients most commonly directed their threats toward family members. Of the patients who made threats resulting in notifications, 51% had prior arrest records, and 14% had subsequent arrests. Only 52% of the patients who made threats were civilly committed. CONCLUSIONS: The findings suggest that 1) clinicians rarely discharge the duty to protect in the manner specified by the law, 2) many patients whose threats result in notifications have extensive involvement with the criminal justice system, and 3) family intervention may have clinical relevance in many duty-to-protect situations.

Characteristics of psychiatric inpatients who stalk, threaten, or harass hospital staff after discharge.

OBJECTIVE: The purpose of this study was to identify demographic and clinical characteristics of psychiatric inpatients who stalk, threaten, or harass hospital staff after discharge. METHOD: The authors retrospectively summarized the demographic and clinical characteristics of 17 inpatients who engaged in this type of behavior and a comparison group of 326 inpatients. RESULTS: The patients who stalked, threatened, or harassed staff after discharge were significantly more likely than the comparison patients to have a diagnosis of personality disorder and/or paranoid disorder, erotomanic subtype, and to have a history of physically assaultive or fear-inducing behavior. The data suggest that they were more likely to be male and never married and to have histories of multiple hospitalizations, suicidal or self-injurious behavior, and substance abuse or dependence. CONCLUSIONS: The findings reveal several risk factors that may be useful in identifying a subgroup of patients who pose a risk of directing aggressive behavior toward hospital staff after discharge.

A naturalistic study of clinical use of risperidone.

Follow-up data on 97 of the 101 patients at a university-based psychiatric hospital for whom risperidone had been prescribed between February 1994, when the medication was introduced, and October 1996 were reviewed an average of 102 weeks after the start of the medication. Only 28.9 percent of the patients were still on risperidone at follow-up. Patients who were maintained on risperidone were able to tolerate a higher dose with fewer side effects. The most common reasons for discontinuation were failure to achieve a therapeutic effect, noncompliance, and adverse side effects. The findings of this naturalistic study represent a cautionary consideration for the remarkable enthusiasm that surrounded the introduction of risperidone.

Comparison of the skin tumor-promoting potential of different organic peroxides in SENCAR mice.

The skin tumor-promoting activities of three organic peroxides were evaluated and compared to the activity of benzoyl peroxide, a well-characterized tumor promoter. Two of the compounds (di-t-butyl peroxide and dicumyl peroxide) were dialkyl peroxides and the other (di-m-chlorobenzoyl peroxide) was a diacyl peroxide. These compounds were selected based on a previous study in which we evaluated their capacity to induce epidermal hyperplasia, ornithine decarboxylase activity, and dark basal keratinocytes, which have been reliable short-term markers of tumor promotion. Dicumyl peroxide was a weak tumor promoter despite its high activity in inducing hyperplasia. Like benzoyl peroxide, di-m-chlorobenzoyl peroxide generally had intermediate activity as an inducer of short-term markers of tumor promotion and was a moderately effective tumor promoter. However, compared to benzoyl peroxide, di-m-chlorobenzoyl peroxide was more toxic to the skin, which may have limited its tumor-promoting activity. The final compound, di-t-butyl peroxide, which was essentially inactive in short-term assays, was also totally inactive in promoting papillomas or carcinomas in initiated skin. Tumor-promoting efficacy generally showed an inverse association with thermal stability for the compounds tested, suggesting that the rate of formation of free radicals is a key factor contributing to tumor promotion by organic peroxides. However, a number of other factors can potentially affect the activity of different organic peroxides as tumor promoters. Each compound evaluated had a different spectrum of activities, and these compounds should be useful for studying mechanisms of organic peroxide-induced tumor promotion.

Angiogenesis is an early event in the development of chemically induced skin tumors.

In this study we have analyzed the vascular response induced in the two-stage carcinogenesis model in SENCAR mice. The role of angiogenesis has not been explored in this model, which is the paradigm of multistage carcinogenesis and a model for neoplastic lesions derived from exophytic premalignant lesions (e.g. colon carcinoma, bladder papilloma). We investigated if angiogenesis is involved in the formation of papillomas and in the progression from papilloma to carcinoma. To this end we analyzed the vasculature of normal and hyperplastic skin, focal epidermal hyperplasias that are precursors of papillomas, papillomas at different stages and squamous cell carcinomas. We also analyzed the vascularization of papillomas induced in two strains of mice that differ in their susceptibility to malignant progression. We show here that angiogenesis is turned on in the earliest stages of papilloma formation. In late stages, regardless of state of progression, the predominant response is an increase in the size of blood vessels. Thus, in the SENCAR mouse model, representative of exophytic tumors, the angiogenesis switch is a very early event, probably mechanistically related to the development of the primarily exophytic lesions. Therefore, the density of blood vessels cannot be used as a predictor of malignant progression in this model.

The relationship between confidence and accuracy in clinical assessment of psychiatric patients' potential for violence.

The authors studied the relationship between confidence and accuracy in clinical assessments of psychiatric patients' short-term risk of violence. At the time of entry to the hospital, physicians (N = 78) estimated the probability that each of 317 patients would physically attack other people during the first week of psychiatric hospitalization. The clinicians also indicated the degree of confidence they had in their estimates of violence potential. Nurses rated the occurrence of inpatient physical assaults with the Overt Aggression Scale. The results showed that when clinicians had a high degree of confidence, their evaluations of risk of violence were strongly associated with whether or not patients became violent. At moderate levels of confidence, clinicians' risk estimates had a lower, but still substantial relationship with the later occurrence of violence. However, when clinicians had low confidence, their assessments of potential for violence had little relationship to whether or not the patients became violent. The findings suggest that the level of confidence that clinicians have in their evaluations is an important moderator of the predictive validity of their assessments of patients' potential for violence.

Evidence that initiated keratinocytes clonally expand into multiple existing hair follicles during papilloma histogenesis in SENCAR mouse skin.

We have previously shown that the precursors of cutaneous papillomas in SENCAR mice initiated with 7,12-dimethylbenz[a]anthracene and promoted with 12-O-tetradecanoylphorbol-13-acetate are focal hyperplastic lesions that we refer to as squamous cell hyperplastic foci (SCHF). Ha-ras gene codon 61 mutations were frequently found in SCHF, providing evidence that these lesions represent clones of initiated cells. We report here the pathogenesis of multiple hair follicle involvement in more advanced SCHF and describe the role of the hair follicle in papilloma histogenesis. Detailed histological evaluation of 83 SCHF and 25 early papillomas revealed a morphological continuum from the least developed SCHF, involving only one hair follicle, to advanced SCHF and early papillomas, which involved more than 10 hair follicles. These results provide evidence of the recruitment of additional hair follicles as SCHF progress. In advanced SCHF and early papillomas the bulk of the epithelial component in all cases consisted of several markedly hyperplastic adjacent hair follicles, whereas the involved interfollicular epidermis (IFE) was generally less hyperplastic. All of the hair follicles involved in SCHF appeared to have been preexisting, based on their pattern of spacing, that they were consistently normal appearing below the level of the sebaceous glands, and that they were in the same phase of the hair cycle as surrounding, uninvolved hair follicles. Also, no evidence of follicular neogenesis was observed in serially sectioned SCHF, and coalescence of smaller lesions was rare. To investigate whether the involvement of multiple hair follicles in SCHF was due to expansion of initiated cells into existing hair follicles or, possibly, to a paracrine mechanism, we analyzed different levels of three serially sectioned SCHF and one early papilloma for Ha-ras mutations. These analyses revealed cells with Ha-ras gene codon 61 mutations at multiple levels that involved different hair follicles. Overall, our results provide evidence that as initiated cells clonally expand, they spread across the IFE and populate the upper permanent portions of existing hair follicles. The abnormal proliferation of the infundibula of the hair follicles involved in SCHF appears to give rise to most of the epithelial component of papillomas.