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At least 19 recordsLinked to original sources

PubMed1991

Characterization of a newt tenascin cDNA and localization of tenascin mRNA during newt limb regeneration by in situ hybridization.

We previously showed that tenascin, a large, extracellular matrix glycoprotein, exhibits a temporally and spatially restricted distribution during urodele limb regeneration. To further investigate the role of tenascin in regeneration, we cloned a newt tenascin cDNA, NvTN.1, that has 70% homology to the chicken tenascin sequence. A deduced amino acid sequence of NvTN.1 showed a modular structure unique to tenascin characterized by epidermal growth factor-like and fibronectin type III repeats. To determine the cellular origin of tenascin protein during limb regeneration, we localized tenascin transcripts by in situ hybridization using a riboprobe synthesized from NvTN.1. Transcripts could not be detected in normal limb tissues but first became detectable in the wound epithelium at 2 days and in the distal mesoderm at 5 days after amputation. These wound epithelial cells are probably the source of tenascin protein found within and immediately underneath the wound epithelium. At preblastema stages, hybridization was seen in cells associated with most of the distal mesodermal tissues but not in dermis. At blastema stages, essentially every mesenchymal cell contained tenascin transcripts. Thus, regardless of origin, blastemal mesenchymal cells may share a common regulatory mechanism that results in tenascin gene transcription. Finally, during redifferentiation stages of regeneration, tenascin gene transcription was associated with both differentiation and growth. The results show that initiation of tenascin gene expression is an early event in regeneration and continued tenascin gene transcription is associated with some of the important processes of regeneration, namely wound epithelial-mesenchymal interactions, dedifferentiation, initiation of cell cycling, blastema outgrowth, and cellular differentiation.

Amino Acid Sequence↗

PubMed1989

Two contrary functions of tenascin: dissection of the active sites by recombinant tenascin fragments.

A structural and functional model of tenascin was elaborated using recombinant parts of three alternatively spliced tenascin variants and anti-tenascin monoclonal antibodies. The fusion proteins were compared with intact tenascin for their functions and by electron microscopy. A strong cell binding site was localized within 104 amino acids. This fragment also contains the epitope of the monoclonal antibody anti-Tn68, which inhibits cell attachment to tenascin and binds near the tips of the six arms of tenascin. In contrast, constructs containing the 13 1/2 EGF-like repeats of tenascin showed an antiadhesive effect. The coexistence of the two contrary signals on the same molecule might be responsible for the versatile features of tenascin.

Amino Acid Sequence↗

PubMed1991

Complete primary structure of porcine tenascin. Detection of tenascin transcripts in adult submaxillary glands.

Tenascin is an extracellular matrix protein that is postulated to modulate tissue differentiation and cell migration during development. cDNA clones for tenascin were isolated from a cDNA library of adult porcine submaxillary glands. Three forms of tenascin clones were observed which varied with the number (8-10) of fibronectin type III (FN-III) domains. A major form consists of the N-terminal domain involved in the hexamer formation of tenascin subunits, 14 epidermal-growth-factor-like domains, nine FN-III domains, and the fibrinogen-like domain. A minor form with ten FN-III domains has never been described. Another striking feature is the lack of an RGD sequence that has been implicated to be crucial for cell adhesion, whereas RGD is present in both chicken and human tenascin sequences. In the adult, tenascin is expressed in very restricted tissues such as brain and chicken gizzard. A survey of tenascin transcripts in various adult rat normal tissues, including brain, revealed that the transcripts were detected only in submaxillary glands where tenascin expression has never been reported.

Amino Acid Sequence↗

PubMed1991

Amino acid sequence of mouse tenascin and differential expression of two tenascin isoforms during embryogenesis.

We have isolated cDNA clones for mouse tenascin and analyzed expression of tenascin mRNAs during embryonic development of the kidney and gut. The deduced amino acid sequence of the mouse tenascin cDNAs shows a modular structure of repeats similar to chicken and human tenascin. In mouse there are 14.5 cysteine-rich repeats with similarity to the EGF repeat, followed by several repeats with similarity to the type III repeat of fibronectin. A longer variant contains 13 fibronectin type III repeats, whereas a shorter splice variant of mouse tenascin lacks the 5 type III repeats that occur directly after the fifth repeat in the longer variant. Contrary to the chicken and human sequences, mouse tenascin does not contain an RGD sequence in the third type III repeat implicated in cell attachment, or in any other positions. In Northern hybridizations to RNA from primary embryonic fibroblasts, the cDNA clone M 20/1 detects two mRNAs with sizes close to 6 and 8 kb. This, and the other data presented here suggest that the two major mouse tenascin polypeptides arise through an alternative RNA splicing. The two major mRNAs are differentially expressed during development. The 8-kb mRNA is more prominent than the 6-kb mRNA throughout prenatal kidney development, but during postnatal development the ratio of the two mRNAs changes. A different expression pattern is seen in the developing gut where the 6-kb mRNA predominates during embryogenesis with the 8-kb mRNA appearing later. The mRNA data of the developing gut correspond with previous protein data, which showed that the shorter Mr 210,000 polypeptide predominates during earlier developmental stages and the larger Mr 260,000 polypeptide appears later in the embryonic gut (Aufderheide, E., and P. Ekblom. 1988. J. Cell Biol. 107:2341-2349).

Amino Acid Sequence↗

PubMed1992

Expression of tenascin mRNA in mesoderm during Xenopus laevis embryogenesis: the potential role of mesoderm patterning in tenascin regionalization.

In Xenopus embryos, the extracellular matrix (ECM) protein tenascin (TN) is expressed dorsally in a very restricted pattern. We have studied the spatial and temporal expression of TN mRNA in tailbud-stage embryos by RNAase protection and in situ hybridization using a cDNA probe for Xenopus TN obtained by PCR amplification. We report that TN transcripts are principally expressed in cells dispersed around the neural tube and notochord as well as in myotome and sclerotome cells. No TN mRNA could be detected in lateral plate mesoderm, but expression was detectable beneath tail fin epidermis. In a second series of experiments, we studied the expression of TN mRNA and protein in combinations between animal and vegetal stage-6 blastomeres and in stage-8 blastula animal caps treated with activin A or basic fibroblastic growth factor (b-FGF). Isolated animal cap tissue cultured alone differentiates into epidermis, which expresses neither TN protein nor TN mRNA. TN expression is, however, elicited in response to isolated dorsal vegetal blastomeres and in response to high concentrations of activin, both of which treatments lead to formation of muscle and/or notochord. Low concentrations of activin, and ventral vegetal blastomeres, treatments that induce mesoderm of ventral character, are poor inducers of TN. However, b-FGF, which also induces ventral mesoderm, elicits strong expression. These results indicate that TN regionalization is a complex process, dependent both on the pattern of differentiation of mesodermal tissues and on the agent with which they are induced. The data further show that "ventral mesoderm" induced by low concentrations of activin is distinct from that induced by b-FGF, and imply that activin induces ventral mesoderm of the trunk while b-FGF induces posterior mesoderm of the tailbud.

Animals↗

PubMed1991

Complex expression pattern of tenascin during innervation of the posterior limb buds of the developing chicken.

The histological localization of the extracellular matrix glycoprotein tenascin was studied during the formation of peripheral nerves in the developing chick hindlimb (embryonic stages 21.5 to 30) by light and electron microscopic immunological methods to obtain insights into the molecule's functional role in the pathway formation by motor and sensory nerves. At stages 21.5 and 23, nerve roots and plexus were surrounded by high tenascin-immunoreactivity, whereas the not yet innervated limb bud was not immunoreactive. During innervation of the limb bud at stages 24.5 and 25, tenascin was detectable at the limb bud base and restricted in its expression to the proximal nerve regions. The nerve tips did not contact areas of elevated tenascin-immunoreactivity. At stages 26 to 28 the dorsal and ventral trunks of the crural and sciatic nerves were surrounded by tenascin-immunoreactivity, which was localized between Schwann and mesenchymal cells. The tips of the growing nerve had now reached the tenascin-positive interface between bone and muscle anlagen. This interface was contacted tangentially rather than penetrated by the nerve tips. The medial and lateral femoral cutaneous nerves were surrounded by high and weak tenascin-immunoreactivity, respectively. In both nerves, tenascin-immunoreactivity was absent where the nerves branched extensively to innervate the skin. The cutaneous nerves diverging from the sciatic nerve were of very low tenascin-immunoreactivity or tenascin-negative at all developmental stages tested. At stages 29 and 30, muscle nerves, having just entered the tenascin-negative muscles, exhibited strong immunoreactivity, whereas the more proximally situated trunks of the sciatic nerve were weakly and discontinuously labeled, particularly at sites where smaller nerves were branching off. Since the cutaneous branches of the sciatic nerve were always of low tenascin-immunoreactivity, the question was raised whether tenascin expression in the sciatic nerve depended on the presence of motor axons. Spinal cords of stage 19 or 20 embryos were therefore removed and tenascin expression was investigated at stages 26 and 27. Some of the residual nerves were weakly tenascin-immunoreactive, whereas others were tenascin-negative. Our observations suggest that tenascin is not involved in the initial guidance of peripheral nerves to their targets. Rather, neuron-induced tenascin appears to stabilize the proximal nerve trunks during a transient time period, possibly by preventing axons and Schwann cells from intermingling with the surrounding mesenchyme, thus contributing to nerve fiber compaction. Conversely, nerve branching may be elicited by reduced levels of tenascin. Furthermore, tenascin may divert growth cones from the developing bone tissue and direct muscle afferents to their appropriate targets.

Animals↗

PubMed1992

Altered content and distribution of tenascin in colitis, colon adenoma, and colorectal carcinoma.

Tenascin is a fibroblast product and extracellular matrix protein probably excerting a fibronectin-antagonizing role. Tenascin is broadly distributed interstitially during embryogenesis but restricted to a small range of structures in normal adult tissues. Using tenascin antibodies and an indirect immunoperoxidase method, normal colon, colitis, colon adenomas, and colorectal carcinomas were examined for tissue distribution of tenascin. Normal mucosa displayed a sparce meshwork of microfibrillar tenascin in the lamina propria. The basement membrane was tenascin negative at the bottom of the crypt and developed into a positive band steadily broadening towards the mucosal surface. In colitis, this polarity was effaced; the basement membrane was a broad tenascin-positive band nearly throughout while interstitial tenascin was moderately increased. Loss of polarity in tenascin content of the basement membrane was a constant feature of adenomas, inconsistently paralleled by structural alterations in surface qualities and continuity of tenascin pattern of the basement membrane. These were most pronounced in carcinomas, where this interface was often discontinuous and had a rough surface; in addition, interstitial tenascin was considerably increased. In carcinomas, the rough surface aspect of the tenascin pattern of the basement membrane was correlated with presence of lymph node metastases (P = 0.04). It is concluded that alterations in tenascin pattern and content reflect complex disturbances in the interaction of inflamed/neoplastic colon epithelium and underlying matrix, leading to an organoid induction of tenascin in the inflammatory context and to induction together with structural abnormalities in neoplasia.

Adenoma↗

PubMed1992

Expression of tenascin in the developing and adult cerebellar cortex.

Since tenascin may influence neuronal cell development, we studied its expression pattern using immunocytochemistry, in situ hybridization, Northern blot analysis, and immunochemistry in the developing and adult mouse cerebellar cortex. Tenascin immunoreactivity was detectable in all layers of the developing cerebellar cortex. In the external granular layer, only the radially oriented processes of Golgi epithelial cells were immunoreactive, whereas the densely packed cell bodies were immunonegative. Tenascin was hardly detectable at contact sites between migrating granule cells and processes of Golgi epithelial cells. Axons of granule cells in the molecular layer were immunoreactive, whereas their cell bodies in the internal granular layer lacked detectable levels of tenascin. By in situ hybridization, only Golgi epithelial cells and astrocytes of the internal granular layer and prospective white matter, but not nerve cells, could be shown to synthesize detectable levels of tenascin mRNA in the developing mouse cerebellar cortex. Thus, tenascin in the cerebellar cortex seems to be a glia-derived molecule that becomes adsorbed to neuronal surfaces in a topographically restricted pattern in situ. Levels of tenascin protein and mRNA decreased significantly with increasing age. In the adult, tenascin immunoreactivity was weak and mainly restricted to the molecular layer and tenascin mRNA was confined to Golgi epithelial cells, indicative for a functional heterogeneity in differentiated cerebellar astrocytes. Quantitative immunoblot analysis revealed that the 225 and 240 kDa components of tenascin were developmentally downregulated at a faster rate than the 190 and 200 kDa components, corresponding to the faster downregulation of the 8 kilobase (kb) mRNA species compared to the 6 kb mRNA species as revealed by Northern blot analysis. These observations indicate a differentially regulated expression of the tenascin components. We hypothesize that glia-derived tenascin modifies the functional properties of nerve cell surfaces and that tenascin is involved in such different morphogenetic events as neurite growth and oligodendrocyte distribution.

Animals↗

PubMed1988

Immunocytochemical localisation of tenascin during the development of scleral papillae and scleral ossicles in the embryonic chick.

We have used a polyclonal antibody against tenascin (a 240 kDa extracellular matrix glycoprotein) and indirect immunofluorescence to investigate the distribution of tenascin in cryostat sections of the chick sclera during the six stages of scleral papilla development (Murray, 1943) and formation of membrane bone anlagen (mesenchymal condensations between 6-12 days of incubation - HH Stage 29-37). At Stages 1 and 2, when the papilla was a slight thickening in the conjunctival epithelium and mesenchymal condensation formation was initiated, tenascin was sparse in the sclera. At Stage 3, when the papilla had an epithelial mass intruding into the mesenchyme, there was an accumulation of tenascin fibrils along the subsurface of the papilla with fibrils extending from this region into the mesenchymal condensation. Interestingly, tenascin was sparse between papillae and between mesenchymal condensations. The Stage 4 papilla had a similar localisation of tenascin fibrils and in addition fine arborizing fibrils of tenascin were observed within the basal epithelia of the papilla adjacent to the epithelial-mesenchymal interface (which suggested that the fibrils infiltrated through the basement membrane region). The Stage 5 and 6 papillae had a column of vertical tenascin fibrils extending from the subsurface of the papilla to the interior mesenchyme corresponding exactly to the location of the mesenchymal condensation which was then forming the anlage of the ossicle in a flat bed about 100 microns from the conjunctival surface. The column of tenascin disappeared as the osteoid appeared in the ossicular bed on the 12th day of incubation but a dense accumulation of tenascin remained along the subsurface of the papilla. With the exception of tenascin fluorescence in the basal region of the Stage 4 papilla, tenascin fibrils were not observed in the other stages of papilla development in the epithelium covering areas between the mesenchymal condensation. This restricted distribution of tenascin may be important in the morphogenesis of scleral papillae and scleral ossicles.

Animals↗

PubMed1990

Comparison of the distribution patterns of tenascin and alkaline phosphatase in developing teeth, cartilage, and bone of rats and mice.

Tenascin is a glycoprotein of the extracellular matrix, which has been associated with differentiation of hard tissue forming cells. Alkaline phosphatase (AP) is involved in calcification, and it has also been suggested to function in cell differentiation. We have compared the distributions of tenascin and AP in the developing skull and teeth of embryonic and growing rats and mice. Tenascin was localized by immuno-Peroxidase and AP by enzyme histochemical staining of tissue sections. Both tenascin and AP were largely restricted to bone, cartilage, and teeth. In cartilage, tenascin was expressed in the perichondrium, whereas AP activity was detected only in the hypertrophic cartilage. In growing intramembranous bone, tenascin and AP were expressed in the periosteum and endosteum. AP activity was restricted to the inner layer of the periosteum, whereas tenascin expression extended to the more superficial layers. In bud-staged teeth tenascin but no AP activity was localized in the condensing mesenchymal cells around the epithelial bud. At the bell stage both tenascin and AP activity were localized in the cuspal mesenchyme, and the intensity of staining decreased towards the cervical region. In summary, tenascin was present at all sites of AP activity except in the epithelial cells of the enamel organ and the hypertrophic cartilage of the mandibular condyle. In mesenchymal tissues tenascin was more widely distributed than AP. It can be suggested that tenascin has functions at earlier stages of hard tissue formation than AP.

Alkaline Phosphatase↗

PubMed1989

The effect of tenascin and embryonic basal lamina on the behavior and morphology of neural crest cells in vitro.

We have investigated the morphology and migratory behavior of quail neural crest cells on isolated embryonic basal laminae or substrata coated with fibronectin or tenascin. Each of these substrata have been implicated in directing neural crest cell migration in situ. We also observed the altered behavior of cells in response to the addition of tenascin to the culture medium independent of its effect as a migratory substratum. On tenascin-coated substrata, the rate of neural crest cell migration from neural tube explants was significantly greater than on uncoated tissue culture plastic, on fibronectin-coated plastic, or on basal lamina isolated from embryonic chick retinae. Neural crest cells on tenascin were rounded and lacked lamellipodia, in contrast to the flattened cells seen on basal lamina and fibronectin-coated plastic. In contrast, when tenascin was added to the culture medium of neural crest cells migrating on isolated basal lamina, a significant reduction in the rate of cell migration was observed. To study the nature of this effect, we used human melanoma cells, which have a number of characteristics in common with quail neural crest cells though they would be expected to have a distinct family of integrin receptors. A dose-dependent reduction in the rate of translocation was observed when tenascin was added to the culture medium of the human melanoma cell line plated on isolated basal laminae, indicating that the inhibitory effect of tenascin bound to the quail neural crest surface is probably not solely the result of competitive inhibition by tenascin for the integrin receptor. Our results show that tenascin can be used as a migratory substratum by avian neural crest cells and that tenascin as a substratum can stimulate neural crest cell migration, probably by permitting rapid detachment. Tenascin in the medium, on the other hand, inhibits both the migration rates and spreading of motile cells on basal lamina because it binds only the cell surface and not the underlying basal lamina. Cell surface-bound tenascin may decrease cell-substratum interactions and thus weaken the tractional forces generated by migrating cells. This is in contrast to the action of fibronectin, which when added to the medium stimulates cell migration by binding both to neural crest cells and the basal lamina, thus providing a bridge between the motile cells and the substratum.

Animals↗

PubMed1988

Induction of tenascin in healing wounds.

The distribution of the extracellular matrix glycoprotein, tenascin, in normal skin and healing skin wounds in rats, has been investigated by immunohistochemistry. In normal skin, tenascin was sparsely distributed, predominantly in association with basement membranes. In wounds, there was a marked increase in the expression of tenascin at the wound edge in all levels of the skin. There was also particularly strong tenascin staining at the dermal-epidermal junction beneath migrating, proliferating epidermis. Tenascin was present throughout the matrix of the granulation tissue, which filled full-thickness wounds, but was not detectable in the scar after wound contraction was complete. The distribution of tenascin was spatially and temporally different from that of fibronectin, and tenascin appeared before laminin beneath migrating epidermis. Tenascin was not entirely codistributed with myofibroblasts, the contractile wound fibroblasts. In EM studies of wounds, tenascin was localized in the basal lamina at the dermal-epidermal junction, as well as in the extracellular matrix of the adjacent dermal stroma, where it was either distributed homogeneously or bound to the surface of collagen fibers. In cultured skin explants, in which epidermis migrated over the cut edge of the dermis, tenascin, but not fibronectin, appeared in the dermis underlying the migrating epithelium. This demonstrates that migrating, proliferating epidermis induces the production of tenascin. The results presented here suggest that tenascin is important in wound healing and is subject to quite different regulatory mechanisms than is fibronectin.

Animals↗

PubMed1991

Nerve-dependent and -independent tenascin expression in the developing chick limb bud.

The extracellular matrix protein, tenascin, appears in a restricted pattern during organ morphogenesis. Tenascin accumulates along developing peripheral nerves as they leave the spinal cord and enter the limb mesenchyme (Wehrle and Chiquet, Development 110, 401-415, 1990). Here we found that most but not all tenascin deposited along growing nerves is of glial origin. By in situ hybridization with a tenascin cDNA probe, we determined the site of tenascin mRNA accumulation both in normal and nerve-free limbs. In normal wing buds, tenascin mRNA was first detected within the developing limb nerves. Vinculin-positive glial precursor cells, which comigrate with the axons, are the likely source of this tenascin message. In nerveless wing grafts, tenascin was first expressed in tendon primordia in the absence, and thus independently, from innervation. In contrast to normal limbs, grafted wing buds neither contained vinculin-positive glial precursor cells, nor expressed tenascin in regions proximal to tendon primordia. In normal wing buds, tenascin deposited by tendon primordia transiently parallels and surrounds certain developing nerves. After the major nerve pattern is established, tenascin mRNA disappears from nerves in the upper limb, but is expressed in perichondrium and tendons. We propose that glial tenascin facilitates the penetration of axons into the limb bud and is important for nerve fasciculation. In some places, early tendon primordia might help to guide the migration of axons and glial precursor cells towards their target.

Animals↗

PubMed1991

The expression of tenascin by neural crest cells and glia.

The extracellular matrix glycoprotein tenascin is concentrated in both the embryo and adult in regions where cell motility is taking place. For example, during avian neural crest morphogenesis tenascin is concentrated in the rostral half of the sclerotome, precisely where the neural crest cells themselves are found. Previous in vitro studies indicated that somite cells were the source of this tenascin, implying a role for tenascin in directing the ventral migration of neural crest cells and thus the establishment of the periodic arrangement of the PNS. In this study, we have used a cDNA probe to identify the source of tenascin found along the pathways of the neural crest using in situ hybridization. In tissue sections, individual cells found along the neural crest migratory pathways, both before entering the somites and within the somites, are strongly labelled by the tenascin cDNA. In vitro neural crest cells are more strongly labelled with the tenascin probe than somite cells. Finally, western blotting has been used to identify tenascin in culture medium conditioned by neural crest cells. This indicates that neural crest cells themselves are the source of much of the tenascin found lining their migratory pathways, and that interactions with somite cells may not be needed to induce the expression of tenascin. We have also studied the distribution of tenascin mRNA in the developing spinal cord and spinal ganglia. At embryonic days 7 and 10, tenascin cDNA hybridizes within cells that appear to be migrating from the ependymal layer to the white matter, as well as within cells in the dorsal roots.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Differential distribution of tenascin in the normal, hyperplastic, and neoplastic breast.

We studied by immunohistochemistry the distribution of tenascin with the monoclonal antibody 100EB2, and compared it with that of laminin in breast tissue samples from fetal, adult resting, lactating, and aging parenchyma, variants of fibrocystic disease, fibroadenomas, cystosarcoma phylloides, and ductal and lobular carcinomas. Monoclonal antibodies were applied to cryosections by the avidin-biotin-complex method; selected samples were studied by double immunofluorescence, and by Western blot analysis. In adult resting and aging breasts, tenascin immunoreactivity was noted in the periductal and periacinar stromal regions as thin irregular bands; in the lactating breast, broader periductal bands were observed. In these samples, laminin immunoreactivity was a single continuous line around ducts, acini, and vessels. In fetal breasts, tenascin appeared as thick periductal bands, whereas laminin remained as a delicate single line. In FCD, tenascin increased around ducts showing hyperplasia, papillomas and apocrine metaplasia, whereas laminin retained its delicate linear pattern. Similar patterns were seen in fibroadenomas and cystosarcoma phylloides with variable tenascin reactivity in the stroma beyond the ducts. Tenascin immunoreactivity was markedly increased around ducts containing in situ carcinoma appearing as broad bands, whereas that of laminin showed a linear, frequently discontinuous appearance. Prominent stromal tenascin immunoreactivity was seen in infiltrating ductal and lobular carcinomas, whereas laminin was virtually absent save for scattered lines. The abundance of tenascin in the carcinomatous stroma contrasted with its scarcity in the non-neoplastic stromal regions. By Western blotting, both chains of tenascin with molecular weights 250,000 and 180,000 were shown in ductal and lobular carcinomas as well as in normal breast. Tenascin immunoreactivity was noted in the periepithelial stromal regions of adult resting and aging breast ducts and acini. The amount of tenascin was moderately enhanced in certain physiologic conditions (fetal growth, gestation), as well as hyperplasias, dysplasias (fibrocystic disease) and benign tumors, whereas it was markedly enhanced in intraductal and infiltrating carcinomas. During fetal mammary development, adult physiologic and pathologic hyperplasias, and in carcinomas, the increasing tenascin reactivity contrasted with the stable or decreasing laminin reactivity.

Adult↗

PubMed1992

Expression of human tenascin in synovitis and its regulation by interleukin-1.

OBJECTIVE: Tenascin is an extracellular matrix glycoprotein with effects on cell adhesion, cell migration, and lymphocyte activation. We proposed to identify the expression of human tenascin messenger RNA (mRNA) and protein in inflammatory synovitis and in normal synovium, and to identify potential regulatory cytokines. METHODS: Immunohistochemistry and in situ hybridization were used to identify the expression of tenascin in synovium. Northern blot analysis of RNA and both immunoblot analysis and enzyme-linked immunosorbent assay of proteins were used to identify tenascin in synovial cell cultures. RESULTS: Tenascin was found along the synovial lining layer and in perivascular areas of normal synovium. In inflammatory synovitis, tenascin protein and mRNA expression were shown to be increased in the synovial lining layer, in perivascular areas, in lymphoid aggregates, and in areas of fibrosis. Interleukin-1, a major mediator of tissue injury in inflammatory synovitis, induced tenascin expression and deposition in primary synovial fibroblast cultures. CONCLUSION: Tenascin mRNA and protein are increased in inflammatory synovitis, and interleukin-1 is an inducer of tenascin in synovial fibroblasts. This identifies a new pathway by which interleukin-1 alters the extracellular matrix composition in synovitis. Since tenascin has effects on lymphocyte activation and cell adhesion, the induction of tenascin in inflammatory synovitis may play a role in the pathophysiology of arthritis.

Cell Adhesion Molecules, Neuronal↗

PubMed1992

Localization and cellular source of the extracellular matrix protein tenascin in normal and fibrotic rat liver.

The distribution and the cellular source of the novel extracellular matrix glycoprotein tenascin were studied in normal and fibrotic rat liver. Cryostat sections of normal rat livers, livers of rats treated with intraperitoneal injections of CCl4 and 4-day-old and 8-day-old primary fat-storing cell cultures were stained for tenascin and desmin using an immunoperoxidase procedure or a double-label immunofluorescence technique. Fat-storing cell cultures were metabolically labeled with 3H-proline. Radiolabeled proteins were immunoprecipitated from the supernatant with antitenascin antiserum and subjected to polyacrylamide gel electrophoresis. In normal rat livers, tenascin was detected discontinuously along the sinusoids, whereas portal tracts were devoid of staining. In fibrotic rat livers, tenascin was preferentially expressed in areas of cell damage, in slender septa or at connective tissue-parenchymal interfaces. The middle region of broad septa was negative. Desmin-positive fat-storing cells accumulated in areas strongly immunoreactive for tenascin, and double-label immunofluorescence showed cells positive for both tenascin and desmin. In fat-storing cell cultures, both intracellular positivity for tenascin and staining of extracellular fibers were seen. Gel electrophoresis of immunoprecipitated proteins revealed two major and three minor bands with molecular weights consistent with tenascin. We conclude that tenascin is a component of the extracellular matrix of both normal and fibrotic rat livers. The strong expression of tenascin in areas of cell damage, in "early" septa or at septal-parenchymal interfaces, in contrast to its absence from the middle region of mature septa, suggests a role in early matrix organization. Fat-storing cells synthesize and secrete tenascin.

Animals↗

PubMedDate not supplied

Distribution and function of tenascin during cranial neural crest development in the chick.

Tenascin is a glycoprotein associated with the extracellular matrix and the surface of some cell types. Here, the distribution and possible function of tenascin have been examined along the pathways followed by cranial neural crest cells. During early stages of neural crest migration, tenascin was observed in a dense matrix surrounding premigratory cranial neural crest cells. Along the neural tube, tenascin immunoreactivity was observed in a dorsoventral gradient and was also noted under the ectoderm and around the notochord. During advanced neural crest migration, tenascin immunoreactivity colocalized with and appeared to be on the surface of migrating neural crest cells. At later stages, tenascin was present around the otic vesicles, retina, lens, and in an interstitial matrix in the region of the branchial arches. At the level of the occipital somites, tenascin immunoreactivity was observed around the neural tube, notochord, dermamyotome, and on the basal surface of the ectoderm. Tenascin was also observed in an interstitial matrix within the sclerotome. At early stages of vagal neural crest migration, immunoreactivity was uniform within the sclerotome, whereas at later stages tenascin colocalized with vagal neural crest cells within the rostral half of each sclerotome. The possible function of tenascin was tested by injecting antitenascin antibodies lateral to the mesencephalic neural tube. Two predominant defects were noted in injected embryos: 1) ectopic aggregates of cranial neural crest cells external to the neural tube and sometimes located on the apical side of the ectoderm; and 2) open and deformed neural tubes. Both the distribution and results of the perturbation experiment suggest that tenascin is required for proper cranial neural crest migration.

Animals↗