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Biomedical subjects

P Fleckman

Publications and source records attributed to P Fleckman.

At least 19 recordsLinked to original sources
PubMed2001

Regulated expression of human filaggrin in keratinocytes results in cytoskeletal disruption, loss of cell-cell adhesion, and cell cycle arrest.

Filaggrin is an intermediate filament (IF)-associated protein that aggregates keratin IFs in vitro and is thought to perform a similar function during the terminal differentiation of epidermal keratinocytes. To further explore the role of filaggrin in the cytoskeletal rearrangement that accompanies epidermal differentiation, we generated keratinocyte cell lines that express human filaggrin using a tetracycline-inducible promoter system. Filaggrin expression resulted in reduced keratinocyte proliferation and caused an alteration in cell cycle distribution consistent with a post-G1 phase arrest. Keratin filament distribution was disrupted in filaggrin-expressing lines, while the organization of actin microfilaments and microtubules was more mildly affected. Evidence for direct interaction of filaggrin and keratin IFs was seen by overlay assays of GFP-filaggrin with keratin proteins in vitro and by filamentous filaggrin distribution in cells with low levels of expression. Cells expressing moderate to high levels of filaggrin showed a rounded cell morphology, loss of cell-cell adhesion, and compacted cytoplasm. There was also partial or complete loss of the desmosomal proteins desmoplakin, plakoglobin, and desmogleins from cell-cell borders, while the distribution of the adherens junction protein E-cadherin was not affected. No alterations in keratin cytoskeleton, desmosomal protein distribution, or cell shape were observed in control cell lines expressing beta-galactosidase. Filaggrin altered the cell shape and disrupted the actin filament distribution in IF-deficient SW13 cells, demonstrating that filaggrin can affect cell morphology independent of the presence of a cytoplasmic IF network. These studies demonstrate that filaggrin, in addition to its known effects on IF organization, can affect the distribution of other cytoskeletal elements including actin microfilaments, which can occur in the absence of a cytoplasmic IF network. Further, filaggrin can disrupt the distribution of desmosome proteins, suggesting an additional role(s) for this protein in the cytoskeletal and desmosomal reorganization that occurs at the granular to cornified cell transition during terminal differentiation of epidermal keratinocytes.

Adherens Junctions↗
PubMed2001

Surgical anatomy of the nail unit.

Surgical procedures in the nail unit require intimate knowledge of the gross and microscopic anatomy of the distal digit in order to obtain accurate diagnostic information and achieve the desired results with minimal impact on appearance and function. This review of the surgical anatomy of the nail unit discusses normal anatomy with an emphasis on those aspects necessary to perform surgery with minimal residual impact.

Humans↗
PubMed2001

Histopathology of the nail.

Patients are often very concerned about the diagnosis and treatment of an unsightly nail problem. Nail biopsy findings can enhance the accuracy of clinical diagnosis, just as skin biopsy is often crucial to the diagnosis of skin disease. In addition, nail biopsy may be necessary for the early detection of a malignant tumor. A skillfully performed adequate nail biopsy, handled and processed and interpreted properly, can be an important part of a dermatologist's armamentarium in providing excellent comprehensive patient care.

Biopsy↗
PubMed2000

Inducible expression of filaggrin increases keratinocyte susceptibility to apoptotic cell death.

Filaggrin is an intermediate filament associated protein that aids the packing of keratin filaments during terminal differentiation of keratinocytes. Premature aggregation of keratin filaments is prevented by filaggrin expression as the inactive precursor, profilaggrin, which is localized in keratohyalin granules in vivo. We have previously shown that filaggrin constructs, when transiently transfected into epithelial cells, lead to a collapsed keratin cytoskeletal network and dysmorphic nuclei with features of apoptosis. The apparent transfection rate is low with filaggrin constructs, supporting their disruptive role but hindering further study. To bypass this problem, we generated stable keratinocyte cell lines that express mature human filaggrin using a tetracycline-inducible promoter system. We found that cell lines expressing filaggrin, but not control cell lines, exhibited increased sensitivity to multiple apoptotic stimuli as measured by morphologic and biochemical criteria. None of the cell lines showed an increase in endogenous expression of filaggrin in response to the same stimuli. Filaggrin expression alone was insufficient to induce apoptosis in these keratinocyte cell lines. We conclude that filaggrin, due to its keratin binding ability, primes cells for apoptosis. Because filaggrin is expressed at a level of the epidermis where keratinocytes are in transition between the nucleated granular and the anucleate cornified layers, we hypothesize that filaggrin aids in the terminal differentiation process by facilitating apoptotic machinery.

Animals↗
PubMed2000

Loss of normal profilaggrin and filaggrin in flaky tail (ft/ft) mice: an animal model for the filaggrin-deficient skin disease ichthyosis vulgaris.

Flaky tail (gene symbol ft) is an autosomal recessive mutation in mice that results in a dry, flaky skin, and annular tail and paw constrictions in the neonatal period. Previous studies demonstrated that the ft mutation maps to the central region of mouse chromosome 3, in the vicinity of the epidermal differentiation complex, a gene locus that includes many nonkeratin genes expressed in epidermis. In this study we report a detailed characterization of the flaky tail mouse. Affected homozygous ft/ft mice exhibit large, disorganized scales on tail and paw skin, marked attenuation of the epidermal granular layer, mild acanthosis, and orthokeratotic hyperkeratosis. Biochemical analysis demonstrated that ft/ft mice lacked normal high molecular profilaggrin (approximately 500 kDa), and instead expressed a lower molecular weight form of profilaggrin (220 kDa) that is not proteolytically processed to profilaggrin intermediates or filaggrin. Mutant mice lacked the large, irregular F-type keratohyalin granules that contain profilaggrin, and filaggrin was absent from the cornified layers of ft/ft epidermis. The expression of epidermal keratins was unchanged, whereas the cornified envelope proteins involucrin and loricrin were increased in ft/ft epidermis. Cultured ft/ft keratinocytes also synthesized reduced amounts of profilaggrin mRNA and protein, demonstrating that the defect in profilaggrin expression is intrinsic to epidermal cells. These findings demonstrate that flaky tail mice express an abnormal profilaggrin polypeptide that does not form normal keratohyalin F-granules and is not proteolytically processed to filaggrin. We propose that the absence of filaggrin, and in particular the hygroscopic, filaggrin-derived amino acids that are thought to function in epidermal hydration, underlies the dry, scaly skin characteristic of ft/ft mice. This animal model provides a tool for understanding the role of filaggrin in normal epidermal function and may provide insight into the molecular basis of the filaggrin-deficient human skin disorder ichthyosis vulgaris. J Invest Dermatol 115:1072-1081 2000

Animals↗
PubMed2000

A large-scale North American study of fungal isolates from nails: the frequency of onychomycosis, fungal distribution, and antifungal susceptibility patterns.

BACKGROUND: Onychomycosis, a fungal infection of the nail bed, is responsible for up to 50% of nail disorders. Although several surveys have been conducted in different parts of the world, there have been no multicenter epidemiologic surveys of onychomycosis in North America. OBJECTIVE: A 12-center study was undertaken to (1) determine the frequency of onychomycosis, (2) identify organisms recovered from the nails, and (3) determine the antifungal susceptibility of isolates. METHODS: A total of 1832 subjects participated in this study and completed a comprehensive questionnaire, and nail clippings were collected for potassium hydroxide examination and culturing. RESULTS: The frequency of onychomycosis, as defined by the presence of septate hyphae on direct microscopy and/or the recovery of a dermatophyte, was found to be 13.8%. In general, the dermatophyte isolates were susceptible to the antifungals tested. CONCLUSION: Because of the limited number of large-scale studies, the baseline incidence is not firmly established. However, the higher frequency of onychomycosis in this study may confirm the suspected increase in incidence of disease in North America.

Adolescent↗
PubMed2000

Ciclopirox nail lacquer topical solution 8% in the treatment of toenail onychomycosis.

BACKGROUND: Onychomycosis is a relatively common condition affecting toenails more than fingernails. It is caused predominantly by dermatophytes. Onychomycosis can cause pain and discomfort and has the potential to be a source of morbidity. OBJECTIVE: We evaluated the efficacy and safety of ciclopirox nail lacquer solution 8% used to treat onychomycosis of the toe in the United States and in centers worldwide. METHODS: Two identically designed, double-blind, vehicle controlled, parallel group multicenter studies were performed in the United States to evaluate the use of ciclopirox nail lacquer to treat mild to moderate toe onychomycosis caused by dermatophytes. In the first study, 223 patients were randomized to treatment (ciclopirox group: 112, vehicle group: 111), and in the second study, 237 subjects were randomized (ciclopirox group: 119, vehicle group: 118). Before randomization, patients were to have clinical features of onychomycosis in at least one great toe with positive light microscopic examination and a positive dermatophyte culture. The test material was applied daily for a period of 48 weeks to all toenails and affected fingernails, covering the entire nail plate and approximately 5 mm of surrounding skin. At baseline, subjects had between 20% to 65% area of target nail involved. Physician's assessments were carried out every 4 weeks, and mycologic evaluation and photographic planimetry using standardized photographs were performed every 12 weeks during the 48 weeks of treatment. In studies conducted outside the United States, patients were also to have clinical, microscopic, and culture evidence of onychomycosis. However, these studies included some patients infected with nondermatophyte organisms (eg, Candida species), and the area of nail involvement was generally greater than observed in the US studies. Treatment regimens also varied in the non-US studies with lacquer applications that were sometimes less frequent than the once daily treatment used in the US studies (eg, alternate day or twice weekly). In addition, the typical duration of treatment was 6 months in the non-US studies as compared with 48 weeks in the United States. Outcome measures were similar to those used in the US trials, although a non-photographic planimetric method was used to quantify disease extent. RESULTS: Data from the pivotal US trials have demonstrated that ciclopirox nail lacquer 8% topical solution is significantly more effective than placebo in the treatment of onychomycosis caused by Trichophyton rubrum, and of mild to moderate toe onychomycosis without lunula involvement. At the end of the 48-week treatment period, the mycologic cure rate (negative culture and negative light microscopy) in study I was 29% vs 11% in the ciclopirox and vehicle groups, respectively. Similarly, the mycologic cure rate for study II was 36% vs 9%, respectively. In the non-US studies, the mycologic cure rates ranged from 46.7% to 85.7%. In addition, ciclopirox nail lacquer has demonstrated a broad spectrum of activity with efficacy against Candida species and some nondermatophytes in non-US studies. Ciclopirox nail lacquer is considered extremely safe regarding causally related treatment emergent adverse-effects (TEAEs), with most TFAEs transient and localized to the site of action (eg, erythema and application site reaction). In the US studies, TFAEs were generally mild and cleared while the patient continued to use the nail lacquer. CONCLUSIONS: Studies conducted worldwide demonstrate the efficacy of ciclopirox nail lacquer for the treatment of finger and toe onychomycosis. Both controlled and open-label studies confirm the excellent safety profile of this topical therapy. Thus, the nail lacquer provides a treatment choice with a favorable benefit-to-risk ratio. With its novel mechanism of action and its topical route of administration, ciclopirox nail lacquer offers an innovative approach to the treatment of this often difficult-to-manage disease

Administration, Topical↗
PubMed1999

The impact of onychomycosis on quality of life: development of an international onychomycosis-specific questionnaire to measure patient quality of life.

BACKGROUND: Onychomycosis is a widespread refractory disease deleteriously affecting quality of life via social stigma and disrupting daily activities. Many physicians perceive onychomycosis as a cosmetic rather than a medical problem. OBJECTIVE: Our purpose was to develop a questionnaire-based instrument to quantify the impact of onychomycosis on patients' quality of life. METHODS: The questionnaire was developed and validated in a multinational cross-sectional study. Completed questionnaires from 532 patients were analyzed: 284 toenail, 248 fingernail (onychomycosis or paronychia). RESULTS: The degree of quality of life impairment from onychomycosis varied by country studied, possibly reflecting cross-national health perception differences. Longer duration of disease, greater involvement of individual nails, and greater number of nails involved were associated with more serious adverse effects. Many physicians underestimated the associated degree of pain. CONCLUSION: The study confirms that onychomycosis physically and psychologically affects patients' lives. The questionnaire may be a valuable tool in evaluating the effect of therapeutic agents on quality of life of patients with onychomycosis.

Cross-Sectional Studies↗
PubMed1999

Trichodysplasia spinulosa--a newly described folliculocentric viral infection in an immunocompromised host.

This is a case report of an immunocompromised individual who presented with progressive alopecia, friable follicular spinous processes, and erythematous, indurated papules. Examination of skin biopsies using light microscopy and immunohistochemistry revealed pathologic changes of the follicular inner root sheath epithelium with dystrophic trichohyaline granules. Electron microscopy of thin sections of tissue revealed intracellular viral particles with a size and appearance consistent with those in the Papovaviridae family. Electron microscopy of negatively stained extract from a homogenized lesion also demonstrated icosahedral viruses with papovavirus morphology. We believe this is a previously unreported folliculocentric viral infection in an immunosuppressed human host and have termed this entity "trichodysplasia spinulosa".

Adult↗
PubMed1999

The calcium-activated neutral protease calpain I is present in normal foetal skin and is decreased in neonatal harlequin ichthyosis.

Calcium concentration is a critical factor for epidermal differentiation and is implicated in the expression and post-translational modification of numerous proteins in suprabasal cells of the epidermis. Calpains (calcium-activated neutral proteases) are believed to participate in signal transduction via highly regulated cytoplasmic protease activity. Here we investigate the expression of calpain I in normal human skin development and in neonatal harlequin ichthyosis (HI), a disorder of altered epidermal differentiation, especially the transition from the granular to the fully differentiated cornified layer. Calpain I was detected in developing foetal epidermis at 54 days estimated gestational age in the basal layer and the periderm of the developing foetal epidermis. By 125 days, calpain I was also detected in the granular layer. This pattern was maintained in newborn skin, but expression was significantly weaker in HI biopsies (n = 7). Reduced expression of calpain was specific to HI and was not observed in other skin diseases. Calpain was also normally expressed in the outer root sheath of hair follicles, in sebaceous glands and in sweat ducts and glands. Immunoblots of epidermal and keratinocyte extracts showed that the 78-kDa and 76-kDa active forms were generated via limited proteolysis of the 80-kDa inactive subunit; however, all forms were diminished in HI, consistent with findings in tissue sections. Our results show that calpain is present throughout the epidermis and is expressed from the early stages of development. These findings implicate calcium-mediated signalling events in the alteration of differentiation that occurs in HI.

Biomarkers↗
PubMed1999

Long-term culture of murine epidermal keratinocytes.

The production of transgenic and null mice with skin abnormalities makes it increasingly important to establish cultures of mouse epidermal keratinocytes for in vitro studies. This requires that each cell line be derived from a single mouse and that the cells be carried for multiple passages. Freezing the cells would also be advantageous by allowing comparison of keratinocytes from several mouse lines at the same time. Mouse keratinocytes, however, have been exceedingly difficult to grow as primary cultures, and subculturing these cells has been virtually impossible until now. We describe a gentle dissociation method and a highly supplemented fibroblast conditioned medium that allows us to grow and subculture total mouse keratinocytes for up to 19 subcultures, allowing an increase in cell number of greater than 10 logs. Epidermal keratinocytes from newborn mice were grown on collagen IV coated dishes in murine fibroblast conditioned medium with 0.06 mM calcium and added growth factors. The cells could be passaged, frozen as viable stocks, and induced to differentiate. Morphologically the cultured keratinocytes demonstrated a pattern characteristic of basal cells. Stratified cultures which made mouse keratin 1 and profilaggrin through passage 10 were induced by purging the monolayer cultures of growth factors, then adding medium with 0.15 mM calcium; expression of mouse keratin 1 and profilaggrin was lost by passage 15. The methods explained in detail here should be of great interest to investigators who are now trying to analyze skin phenotypes and expression of markers of epidermal differentiation of their transgenic or knockout mice.

Animals↗
PubMed1999

Tumor necrosis factor-alpha and interleukin-1alpha decrease the adherence of Streptococcus pyogenes to cultured keratinocytes.

We hypothesized that the primary epidermal cytokines, tumor necrosis factor (TNF)-alpha and interleukin (IL)-1alpha, which are produced after skin injury, modulate bacterial adherence and the initiation of group A streptococcal skin infections. Streptococcus pyogenes binds preferentially to highly differentiated keratinocytes in vitro, simulating the superficial human skin infection, impetigo, and providing a model system for testing this hypothesis. Exposure of keratinocytes to 10 ng/mL TNF-alpha for 20 h decreased adherence to undifferentiated and differentiated keratinocytes by 33% and 38%, respectively. Treatment with 1 ng/mL IL-1alpha decreased adherence to undifferentiated and differentiated keratinocytes by 23% and 18%, respectively. Exposure to both cytokines simultaneously produced an additive 50% reduction in adherence. These data suggest that TNF-alpha and IL-1alpha may play a role in cutaneous host defense by impeding streptococcal adherence and decreasing its ability to form a nidus of infection in the skin.

Bacterial Adhesion↗
PubMed1999

Role of keratinocyte injury in adherence of Streptococcus pyogenes.

Keratinocytes injured acutely by UVB light or lipopolysaccharide were used to test the hypothesis that keratinocyte injury promotes bacterial adherence and the development of group A streptococcal skin infections. Injury did not affect adherence to undifferentiated and differentiated keratinocytes, but keratinocyte differentiation promoted adherence four- to fivefold.

Bacterial Adhesion↗
PubMed1998

Differentiation of cultured keratinocytes promotes the adherence of Streptococcus pyogenes.

Based on a consideration of the histopathology of nonbullous impetigo that shows localization of Streptococcus pyogenes to highly differentiated, subcorneal keratinocytes, we hypothesized that adherence of an impetigo strain of S. pyogenes would be promoted by terminal differentiation of keratinocytes. An assay was developed in which S. pyogenes adhered via pilus-like projections from the cell wall to the surface of cultured human keratinocytes in a time- and inoculum-dependent manner suggestive of a receptor-mediated process. Terminal differentiation of keratinocytes was induced by increasing the calcium concentration in the growth medium, and was confirmed by morphologic analysis using electron microscopy. Adherence of S. pyogenes was three and fourfold greater to keratinocytes differentiated in 1.0 and 1.5 mM calcium, respectively, compared with undifferentiated keratinocytes in 0.15 mM calcium. The presence of calcium during the adherence assay further enhanced adherence nearly twofold. Adherence occurred preferentially to sites of contact between adjacent keratinocytes, suggesting that the keratinocyte receptor may be a molecule involved in cell-to-cell adhesion. In contrast, nonpathogenic Streptococcus gordonii adhered poorly to keratinocytes regardless of their state of terminal differentiation, and adherence of a pharyngeal strain of S. pyogenes was twofold greater to undifferentiated than differentiated keratinocytes. This is the first report of in vitro adherence of S. pyogenes to keratinocytes in a manner that emulates human impetigo. Adherence of only the impetigo strain, and not the pharyngeal strain of S. pyogenes or the nonpathogenic S. gorgonii isolate, was promoted by keratinocyte differentiation. This result provides a model system for investigating the molecular pathogenesis of streptococcal skin infections.

Bacterial Adhesion↗
PubMed1998

Reduced stability and bi-allelic, coequal expression of profilaggrin mRNA in keratinocytes cultured from subjects with ichthyosis vulgaris.

Ichthyosis vulgaris (IV) is an inherited scaling skin disorder in which expression of profilaggrin is reduced. Previous studies have indicated that the reduction is caused by defective post-transcriptional control of gene expression. Here we present evidence that profilaggrin mRNA in keratinocytes cultured from subjects with IV is intrinsically unstable and has a shorter half-life compared with that in normal cells. When IV-affected keratinocytes were treated with the protein synthesis inhibitor cycloheximide, the steady-state level of profilaggrin mRNA was increased due to stabilization of the transcript. In addition, the number of filaggrin repeats within the profilaggrin gene was studied. The number of filaggrin repeats (10-12) in individuals with IV did not differ from that of unaffected subjects. Expression of the gene was bi-allelic and coequal in both control and affected individuals. Our results suggest a model in which a labile ribonuclease and a stabilizing factor may modulate the profilaggrin mRNA steady-state level in normal cells, whereas the stabilizing factor may be absent or functionally inactive in IV-affected keratinocytes.

Alleles↗