Ultrastructure and composition of connective tissue in hyalinosis cutis et mucosae skin

Ultrastructural aspects of the skin in lipoid proteinosis (Urbach-Wiethe disease)

Lipoid proteinosis is a rare autosomal recessive disease, characterized by hyaline deposits of PAS-positive material in tissues due to mutations in the ECM1 gene. This study evaluated the ultrastructure of the skin of a 6-year-old child affected by this condition. The light microscopy identified PAS-positive hyaline deposits, which were more intense in the papillary dermis. Scanning electron microscopy of the dermis showed a compact papillary dermis and fibrillar deposits in the middle dermis. Transmission electron microscopy clearly showed the deposition of fibrillar material in the dermis, forming clusters adherent to elastic fibers, between the collagen bundles and the collagen fibers, and also filling up the cytoplasm of dermal fibroblasts.

Molecular analysis of lipoid proteinosis: identification of a novel nonsense mutation in the ECM1 gene in a Pakistani family

Lipoid proteinosis is a rare autosomal recessive disease characterized by cutaneous and mucosal lesions and hoarseness appearing in early childhood that is caused by homozygous or compound heterozygous mutations in the ECM1 gene located on chromosome 1q21. The aim of the study was to investigate the molecular genetic defect underlying lipoid proteinosis in a consanguineous Pakistani family.

Basement membranes in development and disease

Basement membranes (BMs) are specializations of the extracellular matrix that act as key mediators of development and disease. Their sheet like protein matrices typically serve to separate epithelial or endothelial cell layers from underlying mesenchymal tissues, providing both a biophysical support to overlying tissue as well as a hub to promote and regulate cell-cell and cell-protein interactions. In the latter context, the BM is increasingly being recognized as a mediator of growth factor interactions during development. In this review, we discuss recent findings regarding the structure of the BM and its roles in mediating the normal development of the embryo, and we examine congenital diseases affecting the BM which impact embryonic development and health in later life.

Non-compensating roles between Nckalpha and Nckbeta in PDGF-BB signaling to promote human dermal fibroblast migration

Platelet-derived growth factor BB (PDGF-BB) is a Food and Drug Administration (FDA)-approved growth factor, acting as a mitogen and motogen of dermal fibroblasts (DFs), for skin wound healing. The two closely related SH2/SH3 adapter proteins, Nckalpha and Nckbeta, connect PDGF-BB signaling to the actin cytoskeleton and cell motility. The mechanism has not been fully understood. In this study, we investigated, side by side, the roles of Nckalpha and Nckbeta in PDGF-BB-stimulated DF migration. We found that cells expressing the PDGFRbeta-Y751F mutant (preventing Nckalpha binding) or PDGFRbeta-Y1009F mutant (preventing Nckbeta binding), DF cells isolated from Nckalpha- or Nckbeta-knockout mice, and primary human DF cells with RNA interference (RNAi) knockdown of the endogenous Nckalpha or Nckbeta all failed to migrate in response to PDGF-BB. Overexpression of the middle SH3 domain of Nckalpha or Nckbeta alone in human DFs also blocked PDGF-BB-induced cell migration. However, neither Nckalpha nor Nckbeta was required for the activation of the PDGF receptor, p21-activated protein kinase (Pak1), AKT, extracellular signal-regulated kinase (ERK) 1/2, or p38MAP by PDGF-BB. Although PDGF-BB stimulated the membrane translocation of both Nckalpha and Nckbeta, Nckalpha appeared to mediate Cdc42 signaling for filopodium formation, whereas Nckbeta mediated Rho signaling to induce stress fibers. Thus, this study has elucidated the independent roles and mechanisms of action of Nckalpha and Nckbeta in DF migration, which is critical for wound healing.

Interaction of extracellular matrix protein 1 with extracellular matrix components: ECM1 is a basement membrane protein of the skin

The extracellular matrix protein 1 (ECM1) is a secreted glycoprotein, which plays an important role in the structural and functional biology of the skin as demonstrated by the identification of loss-of-function mutations in ECM1 as cause of the genodermatosis lipoid proteinosis, characterized by reduplication of the skin basement membrane and hyalinization of the underlying dermis. To search for binding partner(s) of ECM1, we tested the in vitro binding activity of ECM1a, a major isoform of four ECM1 splice variants, to different skin extracellular matrix proteins (such as laminin 332, collagen type IV, and fibronectin) and polysaccharides (such as hyaluronan, heparin, and chondroitin sulfate A) with solid-phase binding assay. We demonstrated that ECM1a utilizes different regions to bind to a variety of extracellular matrix components. Ultrastructurally, ECM1 is a basement membrane protein in human skin and is part of network-like suprastructures containing perlecan, collagen type IV, and laminin 332 as constituents. Furthermore, ECM1a enhanced the binding of collagen IV to laminin 332 dose-dependently, showing its involvement in the dermal-epidermal junction and interstitial dermis and making the functional link to the pathophysiology of lipoid proteinosis. To our knowledge, this is previously unreported.

A failure of mucocutaneous lymphangiogenesis may underlie the clinical features of lipoid proteinosis

Lipoid proteinosis (LiP) (OMIM 247100) is a rare autosomal recessive disease caused by loss of function mutations in the extracellular matrix protein 1 gene, ECM1, on chromosome 1q21. LiP is characterized clinically by hoarseness in early infancy, followed by waxy papules and plaques on the face and body along with pox-like and acneiform scars. We studied a 20-year-old Japanese woman with LiP. She was born of consanguineous parents. Biopsy specimens obtained from a nodule on the elbow were used for histopathology, immunohistology and electron microscopy. Exons 6 and 7 of ECM1 were amplified by polymerase chain reaction (PCR) from genomic DNA from the proband, her parents, her brother and an unrelated person. PCR products were sequenced to detect the mutation. Histopathological examination revealed an irregular mass of calcium beneath deposits of a hyaline material in the dermis. Immunofluorescence double staining showed that the CD31-positive microvascular density was increased but that staining for the lymphatic-specific hyaluronan receptor LYVE-1 was drastically diminished in lesional compared with nonlesional skin of the patient and with normal skin. Electron microscopy revealed marked concentric reduplication of basal laminae not only around blood vessels but also around solitary dermal cells positive for Weibel-Palade bodies scattered in the hyaline material. Sequencing of the PCR products revealed a homozygous frameshift mutation, 507delT, in exon 6. This led to a premature stop codon 23 bp downstream. The results of immunopathological and ultrastructural characterization suggest that a failure of mucocutaneous lymphangiogenesis may underlie the clinical features of LiP. Identification of mutation 507delT in a Japanese patient with LiP further supports the thesis that this mutation represents a recurrent mutation in ECM1 in patients with LiP. To our knowledge, this case represents the first report of calcinosis cutis occurring in LiP.

Junctional basement membrane anomalies of skin and mucosa in lipoid proteinosis (hyalinosis cutis et mucosae)

BACKGROUND

Excessive basement membrane (BM) deposition in skin and mucosa is characteristic for lipoid proteinosis (LP; hyalinosis cutis et mucosae), an inherited disease caused by extracellular matrix protein 1 (ECM1) mutations. According to ultrastructure there are striking differences between junctional and microvascular BM.

OBJECTIVE

Distinct analysis of the junctional zone in epidermis and oral mucosa, contrasting concentric BM arrays in the microvasculature; evaluation of impact on epithelial histogenesis and differentiation, and specifically on adhesion structures to BM (hemidesmosomes).

METHODS

LP-epithelia were analyzed for alterations in differentiation, BM composition and texture, and hemidesmosomal components by indirect immunofluorescence (IIF), electron microscopy (EM), and immunoelectron microscopy (ImEM).

RESULTS

Most striking was the irregular deposition of collagen IV and VII, BM-laminin, and laminin-5 at the junctional zone, accompanied by lamellate or punctuated structures below BM (IIF), whereas integrin alpha6beta4 and bullous pemphigoid antigen-1 and -2 (BPAG-1/-2) were regularly aligned. Also integrins alpha2beta1 and alpha3beta1 remained restricted to the epidermal basal layer, while the tissue-specific differentiation markers keratin K1/10 (mucosa, additionally K4/13) appeared delayed indicating mild hyperplasia, further confirmed by focal K6/16 expression. Ultrastructure (EM) disclosed abundance of extended basal cell protrusions and junctional aberrations like exfoliating excessive BM material. Hemidesmosomes were complete, but ImEM indicated weakened interactions between their components (BPAG-1, -2, and HD1). Confirming IIF, collagen IV and VII, and laminin-5 appeared extensively scattered, the latter two probably remaining associated.

CONCLUSIONS

Subtle defects in anchorage assembly, spanning the entire BM zone, apparently compromise epithelial-matrix adhesion, which may provoke (mechanical stress-induced) erroneous BM repair.

Acral keratosis with eosinophilic dermal deposits: a distinctive clinicopatholgic entity or colloid milium redux?

AIMS

The differential diagnosis of acral keratoses is broad. Encompassing a variety of infectious, heritable and degenerative disorders, emphasis upon the clinical setting and histologic subtlety are often required to arrive at the correct diagnosis. Herein, we report on a series of adult patients who presented with agminated or solitary papules of the distal finger found on histologic examination to contain amorphous eosinophilic deposits.

RESULTS

The eosinophilic deposits were found in close proximity to the overlying epithelium and devoid of apoptotic keratinocytes, plasma cells, or vascular thickening reminiscent of amyloidosis or hyalinosis cutis. Special and immunostains yielded eosinophilic material that was elastin and Protein P negative. Despite a similar histomorphologic appearance to colloid milium, typical clinical features of this entity were not present.

CONCLUSION

The etiologic significance of this condition is unknown. Potential sources of the material and a discussion of the differential diagnosis follow.

Vascular anomalies in lipoid proteinosis (hyalinosis cutis et mucosae): basement membrane components and ultrastructure

BACKGROUND

In lipoid proteinosis (LP) vascular anomalies represent severe functional defects caused by excessive deposition of basement membrane (BM)-like matrix, particularly around small subepithelial blood vessels.

OBJECTIVE

Correlation of microvascular anomalies in morphology and ultrastructure with extracellular matrix composition and cell interactions for elucidating vascular involvement in LP-pathophysiology.

METHODS

Biopsies from non-related LP-patients were analyzed by indirect immunofluorescence (IIF), electron microscopy (EM), and immune-EM (ImEM).

RESULTS

In LP-skin and mucosa the thickened vessel walls stained strongly for the BM-components type IV collagen, laminin, perlecan, and nidogen (IIF). Integrin alpha6beta4 was regularly collocated with endothelial surface markers such as PECAM (CD31). Ultrastructure (EM) revealed highly ordered matrix deposits around microvessels, with frequently collapsed lumina, functionally compensated by increased vascular density (histology, IIF). Pericytes were trapped between these concentric BM-layers at varying distances towards the periphery (EM), contrasting their regularly close endothelial apposition. Periodic type IV collagen patterns (ImEM) corroborated the multiple BM-leaflet structure and the lack of a common 'fused' endothelial-pericyte BM, seen normally. Presumptive secretory vesicles, abundant in both cell types, implied an equal contribution to BM-synthesis, but also indicated partial loss of endothelial polarity.

CONCLUSIONS

In LP thickened vessel walls, composed of multiple BM, profoundly alter microvascular properties, also by interference with endothelial-pericyte interactions. The increased microvascular density reflects compensatory restoration for disabled function. Most remarkable was the exaggerated secretory activity (also at luminal surfaces) underlining the regulatory key role of extracellular matrix protein 1 (ECM1; mutated in LP) in export or turnover of all major BM-components.

Three-dimensional imaging reveals major changes in skin microvasculature in lipoid proteinosis and lichen sclerosus

BACKGROUND

Lipoid proteinosis is a rare autosomal recessive disorder characterized by deposition of hyaline-like material in several organs, including skin. Pathogenic mutations have been found in the extracellular matrix protein 1 gene (ECM1). Recent studies have disclosed that ECM1 is also a target antigen for autoantibodies in patients with the acquired disease, lichen sclerosus. Both conditions have been reported to show abnormalities in dermal blood vessels but these changes have not been fully assessed.

OBJECTIVE

The purpose of this study was to investigate the architecture of the cutaneous microvasculature in lipoid proteinosis and lichen sclerosus to better determine the role of ECM1 in the skin pathology observed in these disorders.

METHODS

Labeling of skin biopsies (lipoid proteinosis, lichen sclerosus and control skin) with antibodies to type IV collagen and laminin-1 and reconstruction of the dermal blood vessels using laser confocal microscopy and computer imaging.

RESULTS

In both lipoid proteinosis and lichen sclerosus there was reduplication of the basement membranes surrounding blood vessel walls. There were enlarged vessels in the mid and deep dermis that were orientated parallel to the dermal-epidermal junction. In addition, the normal capillary loop network in the dermal papillae, as well as the subcutaneous plexus and transverse connecting vessels were lacking in both disorders.

CONCLUSION

This study demonstrates that skin microvasculature is grossly altered when ECM1 is targeted by inherited mutations (lipoid proteinosis) or acquired autoantibodies (lichen sclerosus) and that this glycoprotein appears to have an important role in regulating blood vessel physiology and anatomy in the skin.

Extracellular matrix protein 1 (ECM1) is over-expressed in malignant epithelial tumors

The extracellular matrix protein 1 (ECM1) is a secreted protein that has been implicated with cell proliferation, angiogenesis and differentiation. In the present study, we used immunohistochemical staining to examine the expression of ECM1 in a panel of human tumors and found that it was closely correlated with some types of tumors including: invasive breast ductal carcinoma (83%), esophageal squamous carcinoma (73%), gastric cancer (88%) and colorectal cancer (78%). Significantly, ECM1expression was correlated with the metastatic properties of the tumors. Primary breast cancers that had formed metastases were 76% positive while those that had not metastasized were only 33% positive. ECM1 expression was also correlated with PCNA a marker for proliferation, but not with CD34, a marker for endothelial cells. These results indicate that ECM1 tends to be preferentially expressed by metastatic epithelial tumors.

Lipoid proteinosis: report of four siblings and brief review of the literature

Lipoid proteinosis (Urbach-Wiethe disease) is a rare autosomal recessive disorder associated with deposition of periodic acid-Schiff (PAS)-positive hyaline material in various tissues including skin, mucous membranes, and internal organs. A family is reported in which four siblings (two boys and two girls) born to nonconsanguineous parents had lipoid proteinosis. All had the characteristic hoarseness of voice and three had skin lesions. The diagnosis was confirmed by the presence of typical features on light and electron microscopy.

Lipoid proteinosis. A biochemical and ultrastructural investigation of two new cases

Lipoid proteinosis is a rare autosomal recessive disease characterized by cutaneous and visceral lesions, in which large amounts of amorphous material are constantly found in stroma. Morphological and biochemical studies indicate abnormal collagen production, but little attention has been paid to the lipid component of lesions. Microscopic and ultrastructural studies of skin, with special emphasis on fibroblasts, vessels, nerve endings and eccrine sweat glands, were conducted in two patients with lipoid proteinosis. Biochemical studies were undertaken in cultured fibroblasts. Evidence of lysosomal storage in epithelial cells of eccrine sweat glands and in dermal histiocytes, very similar to that found in some metabolic disorders, particularly Farber disease, was found in both cases. Our findings suggest that two alterations might coexist in lipoid proteinosis, one characterized by impaired normal collagen production and the other related to a metabolic defect which may lead to accumulation of ceramide or more complex lipids.

Cutaneous deposition diseases. Part I

The cutaneous deposition disorders are a group of unrelated conditions characterized by the presence of either endogenous or exogenous substances within the dermis or the subcutis. Part I of this two-part series will focus on metabolic processes involved in the endogenous deposition in the various forms of amyloidosis, porphyria, colloid milium, and lipoid proteinosis. We will also review the clinical, histologic, biochemical, and ultrastructural findings relevant to each disorder. Basic mechanisms of pathogenesis, diagnostic modalities, and treatment options are also discussed.

Lipoid proteinosis in three children

We report on three children with lipoid proteinosis, an autosomal recessive disorder characterized by the deposition of hyaline-like material in the skin, mucous membranes and other tissues. All cases had characteristic hoarseness. Other symptoms observed were infiltrated whitish plaques and pock-like scars on the face, papules on the palpebral margins, and infiltrates in the mucous membranes of the lower lip and tongue. Two of the children were siblings whose parents were first cousins.

Hyalinosis cutis et mucosae. Review with a case report

Hyalinosis cutis et mucosae (lipoid proteinosis) is a rare disorder characterized by hyaline and lipid deposits in the skin and mucous membrane of the oral cavity, upper respiratory tract, and internal organs. It usually appears in infancy with hoarseness. This disorder is particularly interesting because of its rarity and wide range of clinical manifestations. We report a case that demonstrated manifestations of lipoid proteinosis.

Lipoid proteinosis: case report

A 20-month-old Kuwaiti girl had manifestations of lipoid proteinosis, a rare autosomal recessive disorder seen more commonly in Caucasians. This condition is diagnosed based on clinical, histopathologic, and ultrastructural criteria. Its biochemical and genetic aspects are still poorly understood.

Lipoid proteinosis

Lipoid proteinosis (Urbach-Wiethe disease) is a rare, recessively inherited disorder that is characterized by the deposition of hyaline-like material in the skin, oral cavity, and other tissues. It usually appears in infancy with hoarseness. We report a case of lipoid proteinosis in a 10-year-old boy that demonstrates the characteristic clinical, histologic, and ultramicroscopic features of this disease.

Characterization of the changes in matrix molecules at the dermoepidermal junction in lupus erythematosus

Electron microscopy has revealed that the deposition of immunoglobulin in the skin of lupus erythematosus (LE) patients occurs on and below the basal lamina of the basement membrane (BM). The composition of the BM is now to some extent known, and antibodies have been developed against several of its individual components. In this study, we attempt to elucidate the status of some matrix molecules in the dermoepidermal junction in LE. Lesional and nonlesional skin from LE patients was examined using immunofluorescence microscopy with monoclonal and polyclonal antibodies against 6 matrix molecules. Immuno-electron microscopy using monoclonal antibodies was used to discern changes in type IV and type VII collagen. By immuno-fluorescence microscopy, type IV collagen, type VII collagen, and fibronectin were altered in lesional skin. There was a statistically significant correlation between the presence of immunoglobulin and alteration of type IV collagen and type VII collagen in lesional skin. The alterations in type IV and type VII collagens were confirmed on immuno-electron microscopy which showed fragmentation of staining of both antigenic components, particularly type IV collagen.

Lipoid proteinosis--new immunopathological observations

Lipoid proteinosis is described in a family of Scottish descent. Chromosome studies performed on five members were normal. Direct immunofluorescence studies performed on skin with anti-collagen antibodies showed an abnormal distribution of collagen within the skin. No abnormality was detected in DNA extracted from lymphocytes taken from five family members, when probed with gene probes to collagen types alpha 1 (I), alpha 2 (I), alpha 1 (III) and alpha 2 (V).

Lipoid proteinosis: Clinical genetic, and pathological study of a Saudi Arabian family

We present the morphological features and clinical progression of lipoid proteinosis observed in six patients from a Saudi family. The index case presented with hoarseness and characteristic skin lesions. Some of the patients had photosentivity with milia and hypertrichosis. The diagnosis of lipoid proteinosis was confirmed by histopathology and by the findings of normal blood porphyrin levels. The condition is inherited as an autosomal recessive disorderm and consanguinity was an important factor. The rarity of this condition and the common occurrence of close-relative intermarriages in Saudi Arabia prompted this report, which we believe is the first and largest family with lipoid proteinosis possessing an established Arabian ancestry.

Lipoid proteinosis: case report

Lipoid proteinosis is a rare autosomal recessive condition affecting the majority of organ systems, but predominantly involving skin and mucous membranes. The mucocutaneous infiltration due to accumulation of a hyaline material is positive for both sudanophil and periodic acid-Schiff reagents. This was illustrated in a 14-year-old girl with parental consanguinity, who had classic manifestations.

Extracellular matrix of the skin: 50 years of progress

The extracellular connective tissue matrix of the skin is a complex aggregate of distinct collagenous and non-collagenous components. Optimal quantities and delicate interactions of these components are necessary to maintain normal physiologic properties of skin. This overview summarizes the progress made in understanding the normal biology and biochemistry of the extracellular matrix, and will highlight cutaneous diseases with underlying molecular defects in the structure and expression of extracellular matrix components.

Expression of basement membrane zone genes coding for type IV procollagen and laminin by human skin fibroblasts in vitro: elevated alpha 1 (IV) collagen mRNA levels in lipoid proteinosis

Basement membrane zone gene expression by fibroblast cultures established from adult human skin was examined by molecular hybridizations with human sequence-specific cDNAs corresponding to pro-alpha 1 (IV) chain of type IV collagen and B2 chain of laminin. Northern transfer analysis of poly(A)+RNA isolated from fibroblast cultures clearly revealed the presence of specific mRNA transcripts, indicating the expression of the genes coding for pro-alpha 1 (IV) and laminin B2 polypeptides. Quantitative estimates of the relative levels of these mRNAs coding for basement membrane zone components indicated that they are of relatively low abundance in control fibroblasts, as compared with mRNAs coding for fibronectin or pro-alpha 1 (I) chain of type I procollagen. In fibroblast cultures established from the lesional skin of a 32-year-old patient with lipoid proteinosis, the levels of mRNA coding for pro-alpha 1 (IV) polypeptides were increased approximately 4.5-fold, as compared with age- and passage-matched control cultures. This increase was selective in that the levels of fibronectin, pro-alpha 1 (I), and beta-actin mRNAs were unaltered in the same cultures. The increase in pro-alpha 1 (IV) mRNA level was also uncoordinate with the expression of the laminin B2 chain gene, which was unaltered in lipoid proteinosis. The selective increase in pro-alpha 1 (IV) mRNA may have relevance to the accumulation of this basement membrane component in the skin in lipoid proteinosis.

Lipoid proteinosis: ultrastructural and biochemical studies

Lipoid proteinosis, a rare autosomal recessive disease, is histologically characterized by deposition of hyalinlike material in the dermis. In this study the pathologic processes of lipoid proteinosis were evaluated by ultrastructural and biochemical analysis of skin and cultured fibroblasts from a patient with classic features of the disease. Transmission electron microscopy revealed the presence of hyalinlike material with a granular appearance interspersed between collagen fibers. Immediately surrounding the blood vessel walls, there was reduplication of basal laminae in an "onionskin" arrangement. The fibroblastic cells in the affected dermis contained peculiar cytoplasmic inclusions. Biochemical studies with the cultured fibroblasts showed that the total synthesis of extracellular matrix components, as detected by the synthesis of radioactive hydroxyproline or the incorporation of 35SO4(2-) and [3H]glucosamine into macromolecules, was not altered in lipoid proteinosis. However, the relative expression of type I and type III procollagen genes, as detected by molecular hybridizations with pro-alpha 1(I) and pro-alpha 1(III) procollagen complementary deoxyribonucleic acid probes, was markedly altered in cultured fibroblasts. Specifically, the type I procollagen messenger ribonucleic acid (mRNA) levels were significantly reduced, resulting in a decreased type I/III procollagen mRNA ratio. Furthermore, the replicative capacity of lipoid proteinosis fibroblasts, as detected by the incorporation of radioactive thymidine, was reduced. Thus the skin fibroblasts from lipoid proteinosis demonstrate ultrastructural changes, as well as alterations in their phenotypic characteristics, and these changes may have relevance to the pathologic processes of this systemic disease affecting the skin and other organs.

Collagen types I, III, and V in human embryonic and fetal skin

The dermis of human skin develops embryonically from lateral plate mesoderm and is established in an adult-like pattern by the end of the first trimester of gestation. In this study the structure, biochemistry, and immunocytochemistry of collagenous matrix in embryonic and fetal dermis during the period of 5 to 26 weeks of gestation was investigated. The dermis at five weeks contains fine, individual collagen fibrils draped over the surfaces of mesenchymal cells. With increasing age, collagen matrix increases in abundance in the extracellular space. The size of fibril diameters increases, and greater numbers of fibrils associate into fiber bundles. By 15 weeks, papillary and reticular regions are recognized. Larger-diameter fibrils, larger fibers, denser accumulations of collagen, and fewer cells distinguish the deeper reticular region from the finer, more cellular papillary region located beneath the epidermis. The distribution of collagen types I, III, and V were studied at the light microscope level by immunoperoxidase staining and at the ultrastructural level by transmission (TEM) and scanning electron microscopy (SEM) with immunogold labeling. By immunoperoxidase, types I and III were found to be evenly distributed, regardless of fetal age, throughout the dermal and subdermal connective tissue with an intensification of staining at the dermal-epidermal junction (DEJ). Staining for types III and V collagen was concentrated around blood vessels. Type V collagen was also localized in basal and periderm cells of the epidermis. By immuno-SEM, types I and III were found associated with collagen fibrils, and type V was localized to dermal cell surfaces and to a more limited extent with fibrils. The results of biochemical analyses for relative amounts of types I, III, and V collagen in fetal skin extracts were consistent with immunoperoxidase data. Type I collagen was 70-75%, type III collagen was 18-21%, and type V was 6-8% of the total of these collagens at all gestational ages tested, compared to 85-90% type I, 8-11% type III, and 2-4% type V in adult skin. The enrichment of both types III and V collagen in fetal skin may reflect in part the proportion of vessel- and nerve-associated collagen versus dermal fibrillar collagen. The accumulation of dermal fibrillar collagen with increasing age would enhance the estimated proportion of type I collagen, even though the ratios of type III to I in dermal collagen fibrils may be similar at all ages.

Lipoid proteinosis: an inherited disorder of collagen metabolism?

The dermal collagen of a patient with lipoid proteinosis was investigated by immunohistochemistry and biochemical analysis. The affected skin was found to contain significantly less collagen per unit dry weight than normal dermis but showed elevated levels of type 3 collagen with respect to type I. Purification of collagen types from affected skin after pepsin digestion showed no novel forms, but a doubling in the yield of type 5 collagen. These results correlated well with those of immunohistochemistry which showed a patchy, diffuse, widely distributed type 3 collagen and an increase in types 4 and 5 collagens associated with 'onion skin' endothelial basement membrane thickening. Estimation of collagen cross-links showed an abnormal pattern with a preponderance of the keto-imine form not normally associated with skin. These results strongly suggest that lipoid proteinosis involves a primary perturbation of collagen metabolism.

Basement membrane proteins, interstitial collagens, and fibronectin in neurofibroma

The distribution and nature of extracellular matrix proteins in neurofibroma tissue was studied by indirect immunofluorescence, immunoelectron microscopy, immunoblotting, and rotary shadowing. The most striking feature was an extensive network of basement membranes localized mainly around Schwann cells and small blood vessels. The major components, collagen IV, laminin, and nidogen, were mainly deposited in the lamina densa. Some laminin and nidogen could be extracted with 0.5 M NaCl and were shown by electrophoresis to have the characteristic chain and fragment patterns described previously for these proteins isolated from the mouse Engelbreth-Holm-Swarm (EHS) sarcoma. Fragments of collagen IV and collagen VI were solubilized by limited proteolytic digestion and identified after rotary shadowing. The more remote interstitial regions of the tumor contained cross-striated collagen fibrils which were composed of collagen III (diameter, 20-30 nm) or collagen I (diameter, 40-50 nm). Collagen fibrils thicker than 80 nm were not found. The interstitial regions also contained collagen VI as a fine filamentous network near cells and between collagen fibrils. Deposits of fibronectin were rather small and showed a scattered distribution. The data indicate that Schwann cells contribute considerably to matrix production in neurofibroma which may therefore be a suitable model for studying basement membranes of neuroectodermal origin.