Lichen amyloidosus: a consequence of scratching

BACKGROUND

Lichen amyloidosus (LA) is generally said to be a pruritic type of amyloidosis of unknown cause. Histopathologically, it is characterized by epidermal changes of lichen simplex chronicus and by deposits of amyloid in the papillary dermis that are derived from keratin peptides of necrotic keratinocytes. Chronic scratching is responsible for the development of lichen simplex chronicus and may lead to necrosis of individual keratinocytes.

OBJECTIVE

Our purpose was to evaluate whether chronic scratching may also be responsible for the formation of amyloid in LA.

METHODS

We studied patients with LA in regard to histopathologic findings, onset of pruritus, associated diseases, and response to treatment.

RESULTS

In most cases, pruritus had preceded the skin lesions. Eight of nine patients suffered from diseases other than LA that may be associated with pruritus. Histopathologically, amyloid was confined to areas that also showed signs of lichen simplex chronicus. Systemic treatment with sedating antihistamines and intense local treatment with corticosteroids were found to be effective.

CONCLUSION

LA is considered to be a variant of lichen simplex chronicus in which scratching leads to necrosis of keratinocytes and eventually to the formation of amyloid in the papillary dermis. Because chronic scratching seems to be the cause and not the result of the deposits of amyloid, treatment should be directed at the amelioration of pruritus.

Nitric oxide--a newly discovered chemical transmitter in human skin

Nitric oxide (NO) is synthesized by many cells in the body. Low concentrations of NO have homeostatic roles in the circulation and nervous system, whereas high concentrations are biocidal, cytocidal and have immunomodulatory roles. The place of NO in the skin has recently become the focus of much attention, and this review highlights studies on the part played by NO in health and disease.

Immunohistochemical distribution of cutaneous fatty acid-binding protein in human skin

Cutaneous fatty acid-binding protein (C-FABP) has been newly discovered from rat skin. The immunohistochemical study revealed that C-FABP is strongly expressed in rat epidermis. Recently, a highly homologous protein to rat C-FABP was found in psoriatic epidermis, which is termed psoriasis-associated fatty acid-binding protein (PA-FABP). In the present study, we investigated the expression of PA-FABP in normal and pathological human skin using immunohistochemical techniques. In normal skin, PA-FABP was expressed in basal and prickle cell layers, and more strongly in the granular cell layer. The expression pattern of PA-FABP was similar to that of C-FABP in rat skin. In psoriatic skin, PA-FABP was expressed in suprabasal layers and more strongly in more differentiated keratinocytes. In squamous cell carcinoma, PA-FABP showed very strong expression in squamous nests. These results indicate that PA-FABP is a human homologue of C-FABP. Moreover, it is suggested that C-FABP has important roles in the transport and metabolism of fatty acids in epidermis and that altered lipid metabolism may affect the proliferation and/or differentiation of keratinocyte.

Expression of bcl-2 antagonist bak in inflammatory and neoplastic skin diseases

Bak (bcl-2 homologous antagonist/killer) is a proapoptotic member of the ever-expanding bcl-2 gene family, a recently described category of oncogenes that is critical for the regulation of programmed cell death. We investigated the expression of bak in several inflammatory and neoplastic skin diseases in comparison with normal skin. Immunohistochemical analysis revealed positive bak staining in epidermal keratinocytes of normal skin, with the granular layer being stained slightly more strongly than the basal and spinous layers, and in psoriasis vulgaris, lichen planus, actinic keratosis, keratoacanthoma and squamous cell carcinoma. We demonstrated the expression of bak in the follicular infundibulum in contrast to the outer root sheath of the lower follicle, which showed only negative to weak bak expression. Seventeen of 20 basal cell carcinomas examined showed negative immunostaining for bak, and the remaining three basal cell carcinomas showed only partial weak positivity, mainly in the palisading layers of some tumour formations. Immunoblot analysis using cultured normal human epidermal keratinocytes revealed the presence of bak protein in both undifferentiated and differentiated keratinocytes. The results of our study suggest that the loss of bak expression, in conjunction with the previously reported overexpression of bcl-2, might contribute to the pathogenesis of basal cell carcinoma.

Cutaneous involvement in polyvinylpyrrolidone storage disease: a clinicopathologic study of five patients, including two patients with severe anemia

Polyvinylpyrrolidone (PVP), formerly a plasma expander, has continued to be inappropriately used in Taiwan for intravenous injection as a "blood tonic." Five cases of PVP storage disease with cutaneous involvement were studied. Two patients presented with cutaneous eruptions mimicking collagen vascular disease and chronic pigmented purpuric dermatosis. Two other cases were found incidentally: one was with a metastatic tumor and the other in a pemphigus lesion. The fifth case was seen in a blind skin biopsy specimen taken to exclude Niemann-Pick disease after hematologic examination of a bone marrow smear. The latter patient and the patient with a collagen vascularlike disease also had severe anemia and serious orthopedic and neurologic complications due to massive infiltration of PVP-containing cells in the bone marrow with destruction of the bone. Severe irreversible anemia due to PVP storage disease has not been reported before. Three patients admitted having a history of receiving intravenous injection of PVP. The samples obtained from two of them indeed contained 5% PVP as determined by chemical analysis. PVP storage disease can be diagnosed by its histopathologic features. The skin biopsy specimens all showed a variable number of characteristic blue-gray vacuolated cells around blood vessels and adnexal structures with positive tinctorial reactions to mucicarmine, colloidal iron, and alkaline Congo red and negative to periodic acid-Schiff (PAS) and alcian blue. The PVP storage cells were shown to be CD68+ macrophages. The presence of PVP in the skin induced little or no inflammatory reaction. Only the pelvic mass in one patient had a foreign body granuloma formation. Our study showed that systemic parenteral administration of PVP preparation could result in the accumulation of PVP storage cells in the skin, with or without clinical eruptions. The diagnosis of systemic PVP storage disease can be established by performing a skin biopsy for pathologic study. It is important for pathologists and clinicians to be aware of this iatrogenic storage disease to avoid misdiagnosis for hereditary storage disease, osteomyelitis, or signet-ring cell carcinoma. Serious hematologic and orthopedic complications can be caused by repeated massive intravenous injection of PVP. Therefore, PVP preparations should be strictly prohibited for systemic administration.

In situ expression and serum levels of tumor necrosis factor-alpha receptors in patients with early stages of systemic sclerosis

OBJECTIVE

Tumor necrosis factor-alpha (TNF-alpha) is an important cytokine in the early stage of systemic sclerosis (SSc), which is characterized by mononuclear cell infiltration and microvascular alterations. Most effects of TNF-alpha are mediated by its interaction with 2 types of TNF receptors and depend on their surface expression on individual cell subsets. Our purpose was to correlate the serum levels of soluble TNF receptors-TNF-RI(p55) and RII(p75)-with (1) their in situ expression and distribution in lesional skin and on peripheral blood mononuclear cells (PBMC), and (2) the clinical disease progression and inflammatory serum variables in patients with SSc.

METHODS

Serum samples of 32 patients with SSc and 36 healthy probands were examined by ELISA. We performed immunohistological stainings and in situ hybridization on cryostat sections of skin lesions, cytometric analysis on PBMC, and reverse transcriptase polymerase chain reactions using RNA from cultured skin fibroblasts in 17 of these 36 patients.

RESULTS

In contrast to healthy skin and chronic fibrotic SSc, TNF-RI is expressed on about 30% of mononuclear infiltrating cells in early skin lesions. Neither TNF-RI nor RII was detectable on fibroblasts by immunohistochemistry, but specific mRNA could be found on the transcriptional level. TNF-RII is found on most lymphocytes and on 30-50% of endothelial cells, especially in early SSc. Expression of both receptor types on PBMC in patients and controls was not significantly different. Serum levels of soluble TNF-RI and RII correlated well with their in situ expression and with clinical and laboratory signs of inflammation and disease progression in patients with SSc.

CONCLUSION

Our data provide evidence for a central role of the TNF-alpha/TNF-R system in the early pathological events of scleroderma with prominent inflammation and endothelial cell damage. Determination of TNF-R serum levels provides a useful diagnostic tool for characterization of the disease stage and progression, and to guide experimental therapy in patients with SSc.

Distinctive molecular abnormalities in benign and malignant skin lesions: studies by Raman spectroscopy

Near-infrared Fourier transform Raman spectroscopy is an analytical, nondestructive technique that provides information about the molecular structure of the investigated sample. The molecular structure of proteins and lipids differ between neoplastic and normal tissues and therefore Raman spectroscopy has been considered promising for the diagnosis of cancer. We aimed to compare the molecular structure of normal skin, benign and malignant skin lesions by the near-infrared Fourier transform Raman spectroscopy. Biopsies were obtained from the following skin lesions: skin tag, dermatofibroma, seborrhoeic keratosis, actinic keratosis, keratoacanthoma, basal cell carcinoma, squamous cell carcinoma, nevus intradermalis, nevus compositus, dysplastic nevus and lentigo maligna. Control skin was harvested from the vicinity of these lesions. In the Raman spectra, the secondary structure of the proteins was reflected by the amide vibrations of peptide bonds. The principal lipid vibrations were twisting and wagging (CH2) and CH stretching vibrations. Histologically distinguishable lesions showed specific combinations of band changes indicating alterations in the protein conformation and in the molecular structure of the lipids. Histogenetically related lesions (actinic keratosis and sqamous cell carcinoma) produced similar but not identical patterns of spectral changes. Because the examined skin lesions produced reproducible and unique spectra, we suggest that Raman spectroscopy will be useful for diagnosis of skin lesions.

Polyarthritis with cutaneous mucinosis and intrasynovial mucin deposits

We report the first case of cutaneous and articular mucinosis with presence of mucin deposits within the synovium in an HIV-positive patients. Presentation was asymmetric polyarthritis, and subcutaneous nodules developed two months later. Treatment was with hydroxychloroquine. The outcome of both the skin and joint lesions was favourable.

The dermal-epidermal junction

Recent insights into the structure and function of the dermal-epidermal junction have resulted from two converging lines of experimental evidence, namely, the study of inherited blistering disorders of the skin, in which mutations in genes encoding proteins of this region have been discovered, and the targeted ablation of the same genes in knockout mouse models. In addition to these studies, elegant analyses of the cell biology of the hemidesmosome/anchoring filament complex have revealed not only functionally important interactions between structural protein components, but also the role of certain of these proteins in mediating cell adhesion, migration, and signal transduction of messages from the extracellular matrix into the keratinocyte. Our current understanding of the dermal-epidermal junction forms a new model encapsulating the nature both of the hemidesmosomal attachment structures and of the interhemidesmosomal attachments that are mediated by differential cell type specific expression of proteins of the cutaneous adhesion zone.

IL-7 overexpression in transgenic mouse keratinocytes causes a lymphoproliferative skin disease dominated by intermediate TCR cells: evidence for a hierarchy in IL-7 responsiveness among cutaneous T cells

IL-7 is a keratinocyte-derived lymphocyte growth factor critical for the development of gammadelta T cells including murine dendritic epidermal T cells (DETC). We derived transgenic mice that overexpress IL-7 in basal keratinocytes under the control of the human K14 promoter. These K14/IL-7 mice develop dermal and epidermal T cell infiltrates associated with alopecia. This lymphoproliferative skin disease is substantially more severe in mice homozygous for the K14/IL-7 transgene. Conventional DETC expressing a Vgamma5 Vdelta1 TCR are rare or absent among the cutaneous T cells in these mice. The T cells in the skin infiltrates of young K14/IL-7 mice are predominantly gammadelta T cells that express intermediate levels of TCR, are negative for E-cadherin, often lack expression of CD2, and include cells that coexpress NK1.1. T cells expressing intermediate levels of a TCR-alphabeta are also present in transgenic skin, and progressively increase in number as the mice age. Phenotypically similar intermediate gammadelta and alphabeta T cell subsets also constitute the major lymphocyte populations recovered from organ culture of normal mouse skin in the presence of IL-7, suggesting that the T cells that accumulate in the epidermis of K14/IL-7 mice are derived from precursors normally resident in skin. We conclude that intermediate TCR cells, some of which coexpress NK1.1, can be selectively expanded in skin under the influence of IL-7 produced locally. Our results also suggest that features of the epidermal microenvironment besides keratinocyte-derived IL-7 account for the normal predominance of Vgamma5 Vdelta1 DETC in mouse epidermis.

Expression of bcl-6 protein in normal skin and epidermal neoplasms

Bcl-6 protein is a recently identified novel transcription factor whose deregulated expression is associated with diffuse large B cell lymphomas. It was recently shown by us that the protein is located in germinal center B cells and their neoplastic counterparts. In the present study, the expression of bcl-6 protein on normal epidermis, benign, and malignant tumors originating from epidermal cells, and squamous cell carcinoma (SCC) cell lines are investigated. With the use of immunohistochemistry, bcl-6 protein was shown to stain intensely on normal prickle cells, but none to only slightly on epidermal basal cells. Papillomas and keratoacanthomas copied their normal counterparts in the mode of expression. Various levels of expression were found on seborrheic keratoses, while the expression level on basal cell epitheliomas was low. Peculiarly, eccrine poromas and undifferentiated spindle-shaped basal cell epitheliomas were totally unstained. Squamous cell carcinomas showed a variety of expression levels, while two undifferentiated spindle-shaped carcinomas and one undifferentiated SCC cell line remained unstained. These results suggest that the expression of bcl-6 protein may be associated with morphological differentiation in normal and neoplastic epidermal cells.

Immunohistochemical studies of basement membrane proteins and proliferation and apoptosis markers in sulfur mustard induced cutaneous lesions in weanling pigs

Sulfur mustard (2,2-dichlorodiethyl sulfide, HD) is a chemical warfare agent that is a threat to both troops and civilians. The focus of HD research has been on intracellular adduct formation leading to apoptosis and/or necrosis in cutaneous lesions. However, there is work which suggests that HD may have a more direct effect on the basement membrane zone. Immunohistochemical staining to desmosomal proteins, cellular fibronectin, laminin 1, laminin 5, collagen IV, collagen VII, p53, Bcl-2, and PCNA was performed on weanling pig skin exposed to vesicating doses of HD, GB3, an antibody to laminin 5, showed a progressive decrease with loss of expression during the time period of clinical vesiculation. The other basement membrane proteins showed no change or inconsistent changes. PCNA, and p53 staining increased in the overlying epidermis in areas of vesiculation without significant necrosis. Bcl-2 positive cells were decreased or absent after exposure. This study implicates laminin 5 as the main basement membrane protein affected acutely by HD exposure. The patterns of staining of PCNA, Bcl-2, and p53 within the epidermis suggest that apoptosis and cellular necrosis both may play a role in cell death secondary to HD.

Aspects on the physiology of human skin: studies using particle probe analysis

The cellular part of the skin, the epidermis, is a very thin structure, approximately 120 microns thick, a fact which has hindered the exploration of the physiology of the epidermis in normal and pathological conditions. An additional complication is the fact that the epidermis contains layers of cells at different stages of differentiation. Therefore, conventional physiological capillary probes cannot, with any satisfactory precision, be located within a specified cell of a specified layer of the skin in vivo. Hence, alternative ways for the exploration of skin physiology have been sought for. In the past, analysis of the elemental content of skin was done was done as bulk measurements, and surprisingly wide ranges of elemental content were recorded. The width of these ranges was most certainly due to the sampling methods used rather than the sensitivity of the chosen method of analysis. Also, these older measurements did not discriminate between the different strata, and therefore the information provided little if any substance for a functional analysis of processes involved in normal and pathological differentiation of the epidermis. Particle probes, however, have been able to overcome such methodological problems. Over a period of 15 years we have studied normal human skin, normal-looking, paralesional skin from psoriatics, and skin from persons suffering from atopic dermatitis using PIXE analysis. In recent years, trace elements have been shown to work as secondary messengers or regulatory substances. As an example, calcium (Ca2+) has proven to be a very important signalling substance in a great variety of cellular systems. Studies with the transmission electron microscope (TEM) as well as histochemical methods have allowed an understanding of the role of Ca2+ in the differentiation process of the epidermis. Ca2+ has also been shown to play an important role in apoptosis (programmed cell death), which is currently a hot subject for the obvious reason that the final differentiation step between the stratum granulosum level and the stratum corneum represents a particular aspect of programmed cell death. The importance of the balance between calcium and zinc in apoptosis has been clearly demonstrated in a number of cellular systems, but we have still to clarify the validity of topical treatment with Zn ointments in different skin conditions. Substantial iron (Fe) losses via psoriatic lesions were demonstrated more than two decades ago, and these data were given new meaning when we found that a more discrete loss occurs in clinically normal-looking psoriatic skin. Obviously, such findings stress the importance of understanding the relation between the elemental content and normal and abnormal physiology. The ultimate goal of particle probe studies is to provide an understanding of the formation of a mature stratum corneum with a functional barrier reflected in physiological/biochemical mechanisms behind the properties of changed skin in patients afflicted with skin disorders of genetic or constitutional origin. This paper aims to give an overview of the state of the art in skin physiology made possible through the use of particle probes.

Three-dimensional cultures of keratinocytes and an application to in vitro-amyloid production of cutaneous amyloidosis

Some three-dimensional culture models of the skin were reviewed including our systems using a collagen dermal substitute and a matrix dermal substitute. No obvious junctional structures, such as hemidesmosomes and the lamina densa, were formed between the basal keratinocytes and the dermal substitutes, when the cytoplasmic membrane of the basal keratinocytes directly faced the collagenous materials. On the other hand, when the cytoplasmic membrane of the basal keratinocytes faced the preformed basement membrane, the type IV collagen film, or the extracellular matrix gel, an organized interaction occurred between the basal keratinocytes and the dermal substitute through hemidesmosomes and a rudimentary lamina densa. Keratinocyte differentiation in the suprabasal layers seemed to be closely related to such a basal cell differentiation. Our preliminary examination of the experimental amyloid production by the epidermal sheet from the lesional skin of patients with primary localized cutaneous amyloidosis suggested that the basal cells in the transplanted lesional epidermis produced amyloid fibrils in our in vitro culture model. This is another use of the three-dimensional culture models of the skin in addition to the application of the systems to wound treatment.

Microfibrillar elements of the dermal matrix

Connective tissue microfibrils are key structural elements of the dermal matrix which play major roles in establishing and maintaining the structural and mechanical integrity of this complex tissue. Type VI collagen microfibrils form extensive microfibrillar networks which intercalate between the major collagen fibrils and are juxtaposed to cellular basement membranes, blood vessels and other interstitial structures. Fibrillin microfibrils define the continuous elastic network of skin, and are present in dermis as microfibril bundles devoid of measureable elastin extending from the dermal-epithelial junction and as components of the thick elastic fibres present in the deep reticular dermis. Electron microscopic analyses have revealed both classes of microfibrils to have complex ultrastructures. The ability to isolate intact native microfibrils from skin has enabled a combination of high resolution and biochemical techniques to be applied to elucidate their structure:function relationships. These approaches have generated new information about their molecular organisation and physiological interactions in health and disease.

Roles of E- and P-cadherin in the human skin

The Ca(2+)-dependent cell-cell adhesion molecules, termed cadherins, are subdivided into several subclasses. E (epithelial)- and P (placental)-cadherins are involved in the selective adhesion of epidermal cells. E-cadherin is expressed on the cell surfaces of all epidermal layers and P-cadherin is expressed only on the surfaces of basal cells. Ultrastructural studies have shown that E-cadherin is distributed on the plasma membranes of keratinocytes with a condensation in the intercellular space of the desmosomes. During human skin development P-cadherin expression is spatiotemporally controlled and closely related to the segregation of basal layers as well as to the arrangement of epidermal cells into eccrine ducts. In human skin diseases E-cadherin expression is markedly reduced on the acantholytic cells of tissues in pemphigus and Darier's disease. Cell adhesion molecules are now considered to play a significant role in the cellular connections of cancer and metastatic cells. Reduced expression of E-cadherin on invasive neoplastic cells has been demonstrated for cancers of the stomach, liver, breast, and several other organs. This reduced or unstable expression of E- and P-cadherin is observed in squamous cell carcinoma, malignant melanoma, and Paget's disease, but cadherin expression is conserved in basal cell carcinoma. Keratinocytes cultured in high calcium produce much more intense immunofluorescence of intercellular E- and P-cadherin than those cells grown in low calcium. E-cadherins on the plasma membrane of the keratinocytes are shifted to desmosomes under physiological conditions, and therein may express an adhesion function in association with other desmosomal cadherins. Soluble E-cadherins in sera are elevated in various skin diseases including bullous pemphigoid, pemphigus vulgaris, and psoriasis, but not in patients with burns. Markedly high levels in soluble E-cadherin are demonstrated in patients with metastatic cancers.

Topography and biological role of integrins in human skin

We report the topography of integrins in the human epidermis and in cultured human keratinocytes. Both in situ and in vitro beta 1 integrins are exposed at the cell-cell adhesion interface while beta 4 is located on the basal membrane in contact with the basal lamina. Such defined sorting identifies discrete cell membrane domains that may be involved in defining, building up, and maintaining epithelial cell polarity. The distribution of integrins is deeply altered in hyperproliferative states like those occurring in several experimental conditions and in epidermal diseases.

Epidermal barrier in disorders of the skin

The water permeability barrier of the stratum corneum (SC) seems primarily to be regulated by the lamellarly arranged lipid bilayers between the corneocytes, which originate largely from polar lipid precursors provided by the cells of stratum granulosum via exocytosis of the lamellar body (LB) content. In particular, the structural organization of these intercellular lipid lamellae seems to be responsible for the very low water permeability of the intact skin, and these lipid-rich structures might also influence the desquamation process in the SC. The aim of this study was to obtain further insight into the distribution and organization of the epidermal lipids (EL) and the mechanism involved in desquamation and barrier function in normal human skin and scaling skin disorders. Biopsies of healthy human skin (n = 12), of inflammatory skin diseases (atopic dry skin (n = 9), psoriatic skin lesions [n = 2]), and of hereditary keratinization disorders (autosomal recessive ichthyoses congenita (n = 3), X-chromosomal ichthyosis (XCI) [n = 3]) were analyzed utilizing a special fixation protocol with ruthenium tetroxide (RuO4) postfixation. While the atopic dry skin revealed normal barrier structures, the psoriasis lesions were characterized by severe alteration of the lipid structures leading to an abnormal interaction with the desmosomal unit. While the intercellular domains in some of the studied keratinization disorders showed an impaired distribution of the EL (autosomal recessive ichthyoses), X-chromosomal ichthyosis showed normal lipid architecture. Dry and scaly skin disorders are therefore not always accompanied by an impairment of the water permeability barrier.

Effects of xerosis and ageing on epidermal proliferation and differentiation

The hallmarks of dry skin (xerosis) are scaliness and loss of elasticity. Decreased hydration and a disturbed lipid content of the stratum corneum are also well-known features. The frequency of dry skin increases with ageing. The aim of this study was to examine if these known features of dry skin are related to changes in epidermal proliferation and differentiation. In addition, age-related changes in normal and in dry skin were examined: 62 volunteers were divided by clinical grading and biophysical measurements into groups with young/normal, young/dry, aged/normal and aged/dry skin. Biopsy samples from the lower legs (most severe dryness) were examined by two-dimensional gel electrophoresis and by immunohistochemistry for epidermal proliferation, epidermal keratins and cornified envelope proteins. There was a slight increase in proliferation in both groups with dry skin compared with normal skin of the corresponding age. In aged/normal compared with young/normal skin there was a significant decrease in proliferation. However, epidermal proliferation was the same in aged/dry skin as in young/normal skin. For epidermal differentiation, an age-independent decrease of keratins K1 and K10 and an associated increase in the basal keratins K5 and K14 was detected in dry skin. There was also an age-independent premature expression of the cornified envelope protein involucrin. In contrast, loricrin expression was not influenced by dry skin conditions. In summary, epidermal proliferation was significantly decreased in aged/normal compared with young/normal skin. Dry skin showed significant changes in the epidermal expression of basal and differentiation-related keratins, and a premature expression of involucrin irrespective of age.

Folliculosebaceous cystic hamartoma with a neural component: an immunohistochemical study

We present a case of follicular cystic hamartoma, a distinctive cutaneous malformation characterized by marked overgrowth of folliculosebaceous units accompanied by appreciable mesenchymal alterations, including fibroplasia, increased vascular components, and numerous adipocytes. A conspicuous feature of our case is an aggregation of thick trespassing nerve bundles in the deep portion of the neoplasm. An immunohistochemical study revealed the nerve bundles were immunoreactive for the general neuronal marker protein gene product 9.5. The nerves, however, stained negatively with antibodies against neuropeptides such as calcitonin gene-related peptide, substance P, vasoactive intestinal polypeptide, and neuropeptide Y, all of which are known to be contained in normal cutaneous nerves. The presence of these aberrant nerve bundles devoid of the normal expression of neuropeptides supports the concept that folliculosebaceous cystic hamartoma is a true, tumor-like malformation characterized by abnormal overgrowth of normal components of the skin.

Transforming growth factor beta 1 and its latent form binding protein-1 associate with elastic fibres in human dermis: accumulation in actinic damage and absence in anetoderma

Latent transforming growth factor-beta 1 (TGF-beta 1) and its binding protein-1 (LTBP-1) are components of the extracellular matrix microfibrils of cultured human fibroblasts. Using immunohistochemistry we have studied the localization of TGF-beta 1 and LTBP-1 and compared their distribution with that of elastic fibres in the interstitial connective tissue matrix of the human dermis. Prominent LTBP-1 specific fibrillar staining co-localized with the elastic fibres in normal human skin. Co-distribution was also observed in a number of pathological states of the elastic fibres such as solar elastosis, solar keratosis and pseudoxanthoma elasticum. TGF-beta 1 had a staining pattern similar to that of LTBP-1 in solar elastosis and solar keratosis. No staining for LTBP-1 or TGF-beta 1 was found in dermis devoid of elastic fibres, as in anetoderma. LTBP-1 is released from the extracellular matrix of cultured human fibroblasts, epithelial and endothelial cells by proteases. Analogously, the immunoreactivity for LTBP-1 and TGF-beta 1 were also lost from the skin sections by elastase, and by trypsin, a protease pretreatment commonly used in immunohistochemistry. These results indicate that LTBP-1 is a component of the elastin-associated microfibrils of the interstitial connective tissue matrix of human skin. Furthermore, the small latent form of TGF-beta 1 is likely to associate with the extracellular matrix of human dermis via LTBP-1. The release of latent TGF-beta 1 from the matrix, as a consequence of proteolytic cleavage of LTBP-1, is a plausible extracellular mechanism for the regulation of TGF-beta 1 activation.