Mouse mutations as animal models and biomedical tools for dermatological research

In this overview, we describe the advantages, disadvantages, and specific skin and hair abnormalities in spontaneous mouse mutations, as well as sources of information about models generally applicable to skin diseases. These inbred mouse mutations are used directly to evaluate the genetic bases of mammalian skin diseases and indirectly to study the effects of grafting human tissues onto congenitally immunodeficient mice. Such inbred immuno-deficient mice are productively used to study neoplasia and autoimmune diseases; to produce gene products in transfected human cells and to reconstitute the mouse immune system with human cells. The advantages of using inbred mouse mutants dramatically changed when the ability to produce transgenic mice with induced mutations that increase, nullify, or alter the expression of specific genes was created. Combining the best features of spontaneous and induced mouse mutations provides powerful tools to analyze the developmental biology and the diseases of mammalian skin and hair.

Remission of severe epidermolysis bullosa acquisita induced by extracorporeal photochemotherapy

We report a patient with severe epidermolysis bullosa acquisita (EBA) whose disease was refractory to conventional treatments. New bullae continued to develop over greater than 50% of his body surface area despite therapy. His course was complicated by hyperglycaemia, sepsis, hypoxia caused by pulmonary Aspergillus infection and an idiopathic cardiomyopathy. His EBA resolved after treatment with extracorporeal photochemotherapy (ECP). Hence, ECP may be effective in the treatment of severe EBA which has failed to respond to standard treatment regimens.

Brown recluse spider envenomation of the eyelid: an animal model

The authors developed a rabbit model of the brown recluse (BR) spider envenomation of the human eyelid. The spider bite causes cutaneous necrosis and systemic toxicity in human eyelids, possibly leading to disseminated intravascular coagulation, hemolysis, and death. The treatment has been controversial. The animal model evaluated the effects of single- and combined-agent therapy in four phases: venom dose response, time course, therapeutic effectiveness (steroid vs. dapsone vs. antivenom), and optimal therapy (steroid and dapsone; steroid and antivenom; and dapsone and antivenom combination groups). The combination dapsone and antivenom treatment group was the optimal animal regimen, although not completely effective in eliminating microscopic necrosis. The authors also report dramatic clinical improvement in human inflammatory response with dapsone therapy and recommend immediate dapsone therapy combined with specific BR venom, if available, in humans.

Cutaneous ultrastructural features of the flaky skin (fsn) mouse mutation

An autosomal recessive genetic disease with clinical and histopathological skin features resembling human psoriasis vulgaris occurs naturally in flaky skin mice (fsn/fsn). Affected mice are normal at birth, except for a hypochromic anemia. Subsequently, they develop hyperkeratotic plaques and acanthosis with elongation of rete ridges. Scanning electron microscopic examination revealed a greatly thickened epidermis, a sparsity of hairs and scale accumulations on the epidermal surface. Hair shafts had conspicuous pits, striations, and exophytic protrusions. Nails were bent at a 90 degrees angle with surface irregularities and accumulations of scale at the nail base. Transmission electron microscopic examination showed increased epidermal thickness, mitochondrial aberrations, and intraepidermal invasion by neutrophils. Keratohyalin abnormalities were detected using immunocytochemical staining for profilaggrin. At the dermal-epidermal junction, numerous macrophages and mast cells were seen in close proximity to focal dissolutions of the basement membrane. A high density of collagen fibers and cellular infiltrates were evident in the papillary dermis. This constellation of ultrastructural aberrations is typically found in psoriasis vulgaris and supports the theory that the flaky skin mouse mutation is a naturally occurring analog to one variety of human psoriasis vulgaris.

Cutaneous manifestations of Prototheca infections

The genus Prototheca comprises several species, the most prevalent of which is Prototheca wickerhamii. These achlorophyllic algae are found in the slime flux of trees and in freshwater environs. Cutaneous infection with these microbes was first reported 30 years ago. Subsequent case reports have described other manifestations including systemic disease. Asymptomatic and stationary cutaneous plaques may be seen in otherwise healthy patients. Susceptibility to infection is ill defined but may involve an inability of neutrophils to effectively eradicate phagocytosed organisms. Characteristic morula are seen histologically. Antifungal medications are the most effective therapy.

Depletion of cells of the B lineage in the bone marrow of zinc-deficient mice

Though lymphopenia is often noted in malnourished humans and rodents, little is known about the effects of suboptimal nutriture on lymphopoietic processes. Focusing primarily on cells of the B lineage in the marrow of young adult mice, a moderate degree of zinc deficiency (MZD) caused a 43% decline in the proportion of nucleated cells bearing B220 with a 91% decline noted among more severely zinc deficient mice (SZD). Early B cells (B220+Ig-) were highly sensitive to the deficiency, being barely detectable in SZD mice and reduced by almost 60% in MZD mice. Immature B cells (B220+IgM+IgD-) were similarly affected, declining 35% to 80% depending on the degree of the deficiency. In MZD mice, mature B cells (IgM+IgD+) exhibited moderate losses, being somewhat resistant. A more profound loss in this population was noted for SZD mice. Flow cytometric (FACS) scatter profiles indicated that zinc deficiency caused a sharp decline in the proportion of small nucleated cells which in the marrow are thought to contain a high proportion of developing lymphoid cells. There was a concomitant increase in large granular cells that paralleled a substantial increase in the proportion of nucleated cells bearing Mac-1 for both MZD and SZD mice. Given the dramatic depletion of cells of the B lineage in the marrow created by a deficiency in zinc, it is probable that disruptions in lymphopoietic processes in the marrow play a key role in the resulting lymphopenia observed in many types of malnutrition.

The effect of substitutions at position three on the binding and bioactivity of proctolin in locust hindgut and oviduct

A number of proctolin analogs modified at position three were analyzed for their relative binding affinities and biological activity on locust hindgut and oviduct. A decrease in chain length at this position (from Leu, Ile to Val) or an increase in hydrophobicity alone (Glu) or combined with a decrease in chain length (Val, Ser, Thr and Asp) decreased bioactivity but not necessarily binding. (Ser3)-proctolin had a higher affinity than proctolin for both hindgut and oviduct membranes but was less biologically active than proctolin in both tissues. Several other analogs bound with a similar affinity to proctolin but were significantly less biologically active, particularly on locust oviduct. These results suggest that the position three leucine of proctolin is more important for bioactivity than for binding in both oviduct and hindgut. The data also suggest the presence of two proctolin receptor subtypes on oviduct but not on hindgut membranes. Position three proctolin analogs may be useful in more precisely distinguishing these subtypes.

Possible roles for glucocorticoids and apoptosis in the suppression of lymphopoiesis during zinc deficiency: a review

Thymic atrophy and lymphopenia are immunological hallmarks of many forms of malnutrition including deficiencies in zinc. Extreme thymic atrophy (70-80%) along with a 50% loss of splenocytes in mice maintained on a zinc deficient diet (ZD) for 30 days suggested that the deficiency might be altering lymphopoiesis or the production of new lymphocytes by the bone marrow. As shown herein, mice who were marginally zinc deficient being 72-75% the body weight of adequately fed controls, exhibited a 50% decline in pre B-cells and a 25% decline in immature B-cells. The mature B-cells of the marrow appeared fairly resistant to effects of suboptimal zinc intake. Interesting, this pattern was similar to results obtained by treating bone marrow cells with levels of glucocorticoids analogous to those found in nutritionally deficient rodents. Furthermore, these same concentrations of steroids were shown to induce significant levels of apoptosis or cell death among pre and immature B-cells which accounted for their declining numbers subsequent to exposure to glucocorticoid. In order to better ascertain the potential role of glucocorticoids generated during zinc deficiency on lymphopoietic processes, adrenalectomies were performed in an attempt to remove glucocorticoids from the equation. Subsequently, adrenalectomized and sham operated mice were placed on a ZD or zinc adequate diet (ZA). Levels of steroids at the time of sacrifice were elevated six fold in non-adrenalectomized ZD mice compared to ZD adrenalectomized mice. Removal of the adrenal gland protected the thymus of ZD mice from atrophy and also provided substantial protection of lymphopoietic processes.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of apoptotic events in pure and heterogeneous populations of cells using the flow cytometer

The rapid and highly quantitative nature of flow cytometric cell cycle analysis for determining the proportion of apoptotic cells in a population makes it the method of choice for a variety of studies requiring quantitative information about cell death. Furthermore, by employing multiparameter analysis including phenotypic labeling, FACS makes it possible to study apoptosis in specific subsets of cells within a heterogeneous population. Live sorting of cells in the apoptotic region offers the possibility of studying the effects of this form of cell death on key biochemical functions of the cell. Nonetheless, further modification of the fixing-staining methods presented here will be needed to make FACS useful for analysis of apoptosis in human cells.

Chemical skin carcinogenesis is prevented in mice by the induced expression of a TGF-beta related transgene

Skin papillomas and squamous cell carcinomas (SCCs) are induced in mice by tumor initiation with a carcinogen followed by tumor promotion with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). These usually arise from preneoplastic lesions characterized by epidermal proliferation and hyperplasia, dermal edema, and inflammation. To evaluate the role of polypeptide growth factors in chemically induced skin carcinogenesis, we used transgenic mice carrying the cDNA for a TGF-beta related molecule, bone morphogenetic protein-4 (BMP-4), under the control of the regulatory elements of the cytokeratin IV* gene in a skin carcinogenesis protocol. Control non-transgenic littermates and BMP-4 transgenic mice were treated with a single dose of a carcinogen, N-methyl-N'-nitrosoguanidine (MNNG), and biweekly with the tumor promoter TPA for 9 months. In control littermates TPA induced epidermal hyperproliferation, atypia with "dark" cells, and dermal inflammation, resulting in papillomas and SCCs in 13 of 26 animals tested. In BMP-4 transgenic mice, TPA treatment induced the expression of the BMP-4 transgene in interfollicular epidermis but only minimal epidermal thickening, hyperproliferation, and inflammation were noted after the initial dose of TPA. Furthermore, the mitotic indices in transgenic epidermis after 9 months of TPA treatment were significantly lower than the corresponding indices from untreated transgenic epidermis. Consequently, none of the 22 transgenic animals tested developed papillomas or SCCs. In conclusion, we have shown that the TPA induced expression of the BMP-4 transgene blocks proliferation and inflammation in skin, steps that are critical to the subsequent formation of papillomas and SCCs and we characterized an inducible promotersystem which expresses polypeptides in interfollicular epidermis after exogenous stimulation.

Flow cytometric analysis of the effects of in vitro exposure to vomitoxin (deoxynivalenol) on apoptosis in murine T, B and IgA+ cells

The immunotoxic effects of the trichothecene vomitoxin (VT or deoxynivalenol) and other trichothecenes may be mediated by direct interaction with lymphocytes. In this study, flow cytometric cell cycle analysis was used in conjunction with phenotypic staining by specific fluorescein isothiocyanate antibody conjugates to assess the in vitro effects of VT and another protein synthesis inhibitor, cycloheximide (CHX), on apoptosis in specific T- and B-cell subsets within thymus, spleen and Peyer's patch (PP) cultures. Both VT and CHX markedly inhibited T-cell apoptosis in dexamethasone (9 alpha-fluoro-16 alpha-methylprednisolone)-induced (DEX+) cells isolated from thymus, spleen and PP. Apoptosis-associated internucleosomal DNA fragmentation in whole thymus cell lysates as measured by gel electrophoresis was qualitatively consistent with flow cytometry among the various treatment groups. VT and CHX induced apoptosis in untreated (DEX-) T, B. and IgA+ cells from spleen and PP, whereas the effects of VT and CHX on DEX-induced apoptosis in B and IgA+ cells from these sources were negligible. These findings indicate that VT could either inhibit or enhance programmed cell death in a concentration-dependent manner and that this was dependent on lymphocyte subset, tissue source and glucocorticoid induction.

Protein tyrosyl phosphatase-1B is expressed by normal human epidermis, keratinocytes, and A-431 cells and dephosphorylates substrates of the epidermal growth factor receptor

In the epidermis tyrosine kinases such as those found in the epidermal growth factor receptor (EGF-R) phosphorylate regulatory molecules on tyrosine and play an important role in controlling epidermal growth. Phosphotyrosyl phosphatases (PTPase) that dephosphorylate EGF-R and other proteins phosphorylated on tyrosine must also play an important role in controlling epidermal growth. The presence and metabolism of one such PTPase, PTP-1B, was detected and studied in human skin using biochemical, immunochemical, and molecular biologic methods. The message for PTP-1B was expressed in human epidermis, in keratinocytes cultured from human epidermis, and in human keratinocyte cell lines. The 49-kDa but not the 37-kDa form of PTP-1B was identified in membranes prepared from these cells and tissues by immunodetection on Western blots. Nearly all of the labeled proteins identified by gel electrophoresis of an A-431 particulate fraction phosphorylated with [gamma-32P] ATP in the presence of epidermal growth factor are substrates for PTP-1B because their labeling decreased after incubation with a catalytically active and purified PTP-1B fusion protein. Immunohistochemical methods were used to show that PTP-1B was primarily localized to the basal cell layers in normal thick epidermis. The presence of PTP-1B in intact human epidermis suggests that this molecule is not an artifact limited to cultured cells but is an important molecule in the in vivo regulation of epidermal functions.

Exfoliative dermatitis

Exfoliative dermatitis or erythroderma is a clinical syndrome characterized by widespread erythema, fine or large scales, and desquamation of a significant portion of the body surface. Appropriate management of the patient during the acute phase of erythroderma requires a firm understanding of the pathophysiology and consequences of this clinical syndrome.

Potential role for focal adhesion kinase in migrating and proliferating keratinocytes near epidermal wounds and in culture

In normal, differentiating skin, hemidesmosomes make the stable attachment of basal epidermal keratinocytes to the dermis by linking the cytoplasmic keratin intermediate filaments to components of the basal lamina. In contrast, laterally migrating and proliferating basal keratinocytes in culture and presumably in repairing wounds use focal adhesions to form dynamic attachments to the dermis by linking actin microfilaments to the extracellular matrix. Focal adhesion kinase (FAK), a non-receptor protein tyrosine kinase concentrated along with phosphotyrosine-containing proteins in the focal adhesions of some cultured cells, is activated in vitro when cells attach, form focal adhesions, and spread. This report finds that FAK is activated, as determined from its increased phosphotyrosine content and from its increased labeling with [gamma-32P]ATP, in immunoprecipitates from human cultured keratinocytes attached and spreading on fibronectin compared to those attached but not spreading on polylysine. Furthermore, immunofluorescence shows that both FAK and phosphotyrosine are concentrated in the focal adhesions of cultured keratinocytes attached and spreading on extracellular matrix components known to facilitate cellular migration (fibronectin, collagens I or IV, and epiligrin). Finally, immunohistochemistry localizes FAK to the epidermal-dermal junction in repairing partial thickness burn wounds. FAK is found at the epidermal-dermal junction at sites and times which coincide with actively migrating or rapidly proliferating basal keratinocytes, suggesting that this distribution represents FAK concentrated and activated in adhesions analogous to the focal adhesions seen in cultured cells. Hence, FAK appears to have an important in vivo role in the reepithelialization of human wounds.

Alopecia areata in aging C3H/HeJ mice

A disease closely resembling human alopecia areata was found in a large production colony of C3H/HeJ mice that had no evidence of thyroid dysfunction or an infectious etiology. Alopecia developed diffusely or in circular areas on the dorsal surface. Histologically, the changes in this non-scarring alopecia were limited to anagen follicles that were surrounded by mononuclear cells. This infiltrate, composed primarily of cytotoxic (CD8+) and helper (CD4+) T cells, was associated with follicular and hair shaft dystrophy. This infiltrate was markedly reduced by intralesional injection of triamcinolone acetonide with subsequent hair regrowth in the affected site. Pedigree tracing of affected C3H/HeJ mice suggests that this non-scarring alopecia may be an inherited disease. Breeding results of normal haired mice with alopecia areata mice or between alopecia areata mice suggests that this is a complex polygenic disease with a female predominance at younger ages. Female mice developed the disease earlier than male mice (3-5 versus > 6 months), with equal numbers affected by 18 months of age. The relative incidence of alopecia areata in one production colony of C3H/HeJ mice was 0.25% for female and 0.035% for male mice, but selective breeding has raised the frequency to nearly 20%. The frequency in an aging colony selectively bred for inflammatory bowel disease reached 4.7%, with equal sex distribution, for mice over 18 months of age, suggesting that this might be a common aging change in C3H/HeJ mice. This C3H/HeJ mouse disease may prove to be a valuable animal model to study specific subtypes of human alopecia areata.