Tenascin-C expression in ultrastructurally defined angiogenic and vasculogenic lesions

Increased degradation of extracellular matrix structures of lacrimal glands implicated in the pathogenesis of Sjögren's syndrome

Lacrimal glands (LGs) of male non-obese diabetic (NOD) mice display many features of human LGs in patients afflicted with the autoimmune disease Sjögren's syndrome (SS), including the loss of secretory functions and a lymphocytic infiltration into the glands by 4 months of age. So far, research has mainly focused on the intracellular events that are involved in initiating LG dysfunction; however, the impact of SS on extracellular matrix (ECM) structures of the diseased LGs has not yet been determined. In this study we identified and compared LG ECM formation and integrity of age-matched male healthy (BALB/c) and diseased (NOD) mice. LG tissues were examined using routine histological, biochemical, immunohistochemical and gene expression analysis. Multiphoton imaging and second-harmonic generation (SHG) microscopy permitted the non-invasive analysis of major LG ECM structures including collagen- and elastin-containing fibers. Biochemical testing demonstrated a significant loss of collagen, glycosaminoglycans and desmosine in NOD LGs when compared to healthy BALB/c LGs. Immunohistochemical staining and gene expression analysis confirmed this disease-related alteration of LG ECM structures. Furthermore, laser-induced autofluorescence and SHG microscopy revealed dramatic changes in the structural organization of most collagenous and elastic fibers of the diseased LG tissues that were more pronounced than those displayed by histological analysis. Our results clearly show an enhanced degradation of ECM proteins accompanied by the severe disorganization and deformation of ECM structures of diseased LG tissues. These new insights into the involvement of ECM degradation in SS may lead to novel therapies for patients suffering from dry eye disease.

[Clinical and immunohistochemical findings of intra- and extraoral angiosarcomas]

PURPOSE

A clinico-pathologic study of typical symptoms of intra- and extraoral angiosarcomas and clinical course under therapy is presented as well as an analysis of the immunohistochemical differential diagnosis of the tumour specific formed spaces.

PATIENTS AND METHODS

Four male patients aged 63-78 years suffered from angiosarcomas of the maxillary sinus, the bucca (two patients) and the alveolar ridge of the lower jaw.

HISTOPATHOLOGY

For comparative analysis paraffin embedded tissue of the initial biopsies was available. The slides were stained with standardized H&E, PAS and Gömörri. For standardized immunohistochemistry following primary antibodies were applied: monoclonal antibodies to pancytoceratin clones AE1/AE3, alpha-smooth-muscle-actin clone 1A4, CD31 clone JC/70A, factor-VIII-related antigen clone F/86, Fli-1 (polyclonal, Zymed, USA), tenascin-C: BC4 (Prof. L. Zardi), oncofetal glucosylated fibronectin clone FDC6 (ACCR), laminin-5: D4B5. Detection using AP-ChemMate and Autostainer (Dako, Denmark).

RESULTS

While the benign appearance of the lesions resulted primarily in wrong diagnoses the histopathologic examination of the biopsies revealed the characteristic pattern of angiosarcomas. Wide surgical excision, radiotherapy and/or antiangiogenic chemotherapy could not prevent tumour progression and death within two and a half years after primary diagnosis. All angiosarcomas reacted partially positive for factor-VIII-related antigen and CD31. The tumour associated structural defect of vascular lamina with partial loss of pericytes/vascular smooth muscle cells was identified immunohistochemically by alpha-smooth-muscle-actin and for the first time by tenascin-C.

CONCLUSIONS

(1.) The variable presentation and the benign appearance of oral and perioral angiosarcomas may often delay diagnosis. Oral and perioral angiosarcomas show poor prognosis despite of multimodal therapy. (2.) Cytoceratin and laminin-5-positivity as typical epithelial antigens don't exclude angiosarcoma. Factor-VIII-related antigen, CD31 as well as Fli-1 identify angiosarcoma. (3.) alpha-smooth-muscle-actin and the loss of the tenascin-C-matrix indicate immunohistochemically the characteristic sarcomatous defect of differentiation.

Tenascin and microvessel stromal changes in patients with non-Hodgkin's lymphoma are isolated to the sites of disease and vary in correlation to disease activity

This study investigated stromal changes in expression of tenascin and vasculogenesis in lymphoma. Documenting the dynamic nature of the stromal changes in lymphoma in relation to response to therapy is helpful in planning new therapies directed at these targets. Two hundred and sixty one samples from 111 patients with varying types of non-Hodgkin's lymphoma were reviewed and examined using immunohistochemistry techniques. Samples were stained for factor VIII - related antigen for microvessel density (MVD) analysis and anti-tenascin antibody for qualitative assessment of the stromal expression. Multiple samples from the same patient were taken at the same point in time to assess whether stromal changes were limited to sites of disease. Multiple samples were examined over the course of a patient's illness to assess whether the stromal changes were modulated according to disease activity. There was a significant increase in tenascin expression and MVD in the sites of disease compared with uninvolved sites (p = 0.01 and p < 0.0001, respectively). In patients who responded to therapy, there was a decrease in the expression of tenascin (p = 0.0049) and MVD (p < 0.0001), and in those with disease progression there was an increase in the tenascin expression (p = 0.0050) and MVD (p < 0.0001). Our results suggest stromal changes are isolated to the sites of disease within patients, allowing targeted therapies to be developed. Further, stromal changes correlate with disease response over the course of the patient's disease. This new finding may have implications for the timing of anti-stromally directed therapies.

Molecular mechanisms of glioma cell migration and invasion

Gliomas are the most common intracranial tumors. In the US, approximately 15,000 patients die with glioblastoma per year (CBTRUS 2002). Despite modern diagnostics and treatments the median survival time does not exceed 15 months. However, it has long been observed that after surgical removal, tumors recur predominantly within 1 cm of the resection cavity. This is mainly due to the fact that at the time of surgery, cells from the bulk tumor have already invaded normal brain tissue. Decades ago Matsukado showed that more than 50% of untreated brain tumors had already reached the contralateral hemisphere (J Neurosurg 18: 636-644, 1961). Therefore one of the most important hallmarks of malignant gliomas is their invasive behavior. Dandy already recognized the highly invasive characteristics of this tumor type and performed hemispherectomy in patients with preoperative hemiplegia (J Am Med Assoc 90: 823-825, 1928). Despite his and others' heroic efforts, recurrence was detected as early as 3 months after surgery (Bell, LJ: J Neurosurg 6: 285-293, 1949), leading to the discontinuation of this radical approach. Diffuse gliomas remain a particularly challenging clinical management problem. Over the last 20 years no significant increase in survival of patients suffering from this disease has been achieved. Even drugs directed against newly identified targets like MMPs or angiogenesis-related targets fail to increase survival duration (Tonn, Goldbrunner: Acta Neurochir Suppl 88: 163-167, 2003) Furthermore, anti-angiogenic drugs have been shown to increase glioma invasiveness, finally leading to gliomatosis cerebri. (Lamszus et al.: Acta Neurochir Suppl 88: 169-177, 2003). In this review we focus on the main features which may underlie the invasive phenotype of human gliomas, and offer a biological basis for optimism towards therapeutic advances to come.

Tenascin-C expression and distribution in cultured human chondrocytes and chondrosarcoma cells

Tenascin-C (TNC) is an oligomeric glycoprotein of the extracellular matrix with several distinct isoforms variably expressed during embryogenesis, tumorogenesis, angiogenesis and wound healing. In the normal human adult, TNC is found in large concentrations in articular cartilage, suggesting tissue-specific function. The purpose of this study was to determine the specific in vitro TNC splicing patterns of articular chondrocytes and a human chondrosarcoma cell line. Cells were cultured in a three-dimensional bead system and TNC splice variant expression and distribution were examined with the use of Western blotting techniques, semi-quantitative reverse-transcription polymerase chain reaction and immunohistochemistry. At both the transcriptional and post-translational levels, the chondrocytes were found to express significantly higher levels of the smaller 220 kDa isoform (P < 0.01), which was predominantly incorporated into the matrix. The splicing pattern of the malignant cells was characterized by a higher proportion of the larger 320 kDa isoform which was extruded into the media. In vivo studies are necessary to verify the expression of the large TNC isoform in chondrosarcoma and the production and integration of the smaller isoform in normal chondroid matrix. In addition, elucidation of the biologic functions of the two major TNC isoforms may lead to the development of novel diagnostic and therapeutic approaches to chondrosarcoma.

Clinical impact and functional aspects of tenascin-C expression during glioma progression

The extracellular matrix protein tenascin-C is expressed in processes like embryogenesis and wound healing and in neoplasia. Tenascin-C expression in gliomas has been described previously; however, the relation to clinical data remains inconsistent. Generally, analysis of tenascin-C function is difficult due to different alternatively spliced isoforms. Our studies focus on changes in tenascin-C expression in human gliomas, correlating these changes with tumor progression and elucidating the functional role of the glioma cell-specific tenascin-C isoform pool. Eighty-six glioma tissues of different World Health Organization (WHO) grades were analyzed immunohistochemically for tenascin-C expression. The influence of the specific tenascin-C isoforms produced by glioblastoma cells on proliferation and migration was examined in vitro using blocking antibodies recognizing all isoforms. In general, tenascin-C expression increased with tumor malignancy. Perivascular staining of tenascin-C around tumor-supplying blood vessels was observed in all glioblastoma tissues, whereas in WHO II and III gliomas, perivascular tenascin-C staining appeared less frequently. The appearance of perivascular tenascin-C correlated significantly with a shorter disease-free time. Analysis of proliferation and migration in the presence of blocking antibodies revealed an inhibition of proliferation by around 30% in all 3 glioblastoma cell cultures, as well as a decrease in migration of 30.6-46.7%. Thus we conclude that the endogenous pool of tenascin-C isoforms in gliomas supports both tumor cell proliferation and tumor cell migration. In addition, our data on the perivascular staining of tenascin-C in WHO II and III gliomas and its correlation with a shorter disease-free time suggest that tenascin-C may be a new and potent prognostic marker for an earlier tumor recurrence.

Origin, differentiation, and maturation of human pulmonary veins

Recent studies on human embryonic and fetal lungs show that the pulmonary arteries form by vasculogenesis. Little is known of the early development of the pulmonary veins. Using immunohistochemical techniques and serial reconstruction, we studied 18 fetal and neonatal lungs. Sections were stained with antibodies specific for endothelium (CD31, von Willebrand factor) and smooth muscle (alpha and gamma smooth muscle actin, smooth muscle myosin, calponin, caldesmon, and desmin) and antibodies specific for the matrix glycoprotein tenascin, the receptor protein tyrosine kinase EphB4, and its ligand ephrinB2. Kiel University-raised antibody number 67 (Ki67) expression allowed qualitative assessment of cell replication. By 34 d gestation, there was continuity between the aortic sac, pulmonary arteries, capillaries, pulmonary veins, and atrium. The pulmonary veins formed by vasculogenesis in the mesenchyme surrounding the terminal buds during the pseudoglandular period and probably by angiogenesis in the canalicular and alveolar stages. EphB4 and ephrinB2 did not distinguish between presumptive venous and arterial endothelium as they do in mouse. All venous smooth muscle cells derived directly from the mesenchyme, gradually acquiring smooth muscle specific proteins from 56 d gestation. Thus, both pulmonary arteries and veins arise by vasculogenesis, but the origins of their smooth muscle cells and their cytoskeletal protein content are different.

Tenascin-C aptamers are generated using tumor cells and purified protein

Tenascin-C (TN-C) is an extracellular matrix protein that is overexpressed during tissue remodeling processes, including tumor growth. To identify an aptamer for testing as a tumor-selective ligand, SELEX (systematic evolution of ligands by exponential enrichment) procedures were performed using both TN-C and TN-C-expressing U251 glioblastoma cells. The different selection techniques yielded TN-C aptamers that are related in sequence. In addition, a crossover procedure that switched from tumor cell to purified protein selections was effective in isolating two high-affinity TN-C aptamers. When targeting tumor cells in vitro, the observed propensity of naive oligonucleotide pools to evolve TN-C aptamers may be due to the abundance of this protein. In vivo, TN-C abundance may also be well suited for aptamer accumulation in the tumor milieu. A size-minimized and nuclease-stabilized aptamer, TTA1, binds to the fibrinogen-like domain of TN-C with an equilibrium dissociation constant (K(d)) of 5 x 10(-9) m. At 13 kDa, this aptamer is intermediate in size between peptides and single chain antibody fragments, both of which are superior to antibodies for tumor targeting because of their smaller size. TTA1 defines a new class of ligands that are intended for targeted delivery of radioisotopes or chemical agents to diseased tissues.

Tenascin-C splice variant adhesive/anti-adhesive effects on chondrosarcoma cell attachment to fibronectin

Tenascin-C is an oligomeric glycoprotein of the extracellular matrix that has been found to have both adhesive and anti-adhesive properties for cells. Recent elucidation of the two major TNC splice variants (320 kDa and 220 kDa) has shed light on the possibility of varying functions of the molecule based on its splicing pattern. Tenascin-C is prominently expressed in embryogenesis and in pathologic conditions such as tumorogenesis and wound healing. Fibronectin is a prominent adhesive molecule of the extracellular matrix that is often co-localized with tenascin-C in these processes. We studied the chondrosarcoma cell line JJ012 with enzyme-linked immunoabsorbance assays, cell attachment assays and antibody-blocking assays to determine the adhesive/anti-adhesive properties of the two major tenascin-C splice variants with respect to fibronectin and their effect on chondrosarcoma cell attachment. We found that the small tenascin-C splice variant (220 kDa) binds to fibronectin, whereas the large tenascin-C splice variant (320 kDa) does not. In addition, the small tenascin-C splice variant was found to decrease adhesion for cells when bound to fibronectin, but contributed to adhesion when bound to plastic in fibronectin-coated wells. Antibody blocking experiments confirmed that both the small tenascin-C splice variant and fibronectin contribute to cell adhesion when bound to plastic. The large tenascin-C splice variant did not promote specific cell attachment. We hypothesize that the biologic activity of tenascin-C is dependent on the tissue-specific splicing pattern. The smaller tenascin-C isoform likely plays a structural and adhesive role, whereas the larger isoform, preferentially expressed in malignant tissue, likely plays a role in cell egress and metastasis.

Tenascin expression and angiogenesis in breast cancers

The expression and the distribution of tenascin as well as the extent of blood vessel formation (angiogenesis) were investigated in 70 invasive human breast carcinomas. Formalin-fixed, paraffin-embedded specimens were stained with monoclonal antibody against tenascin-C (DAKO and Biogenex). Anti-CD31 antibody (Biogenex), an acknowledged marker of stromal angiogenesis, was used to detect endothelial cells. Tenascin immunostaining was positive in the tumours around the persisting normal ducts, around tumour-cell nests, in the neostroma, in some tumour cells, and it was found in or around vascular channels. Tumour vascularity was assessed by quantitative vascular grading (Chalkley point count) and was related to the localization and intensity of tenascin immunoreactivity. 19 tumours (27.1%) were scored as low, 35 (50%) as medium, and 16 (22.9%) as having a high vascular grade. The positive correlation between the vascular grade and the tenascin immunopositivity in tumour stroma was observed. Our results suggest that tenascin expression may be associated with endothelial cell activation and may play an important role in tumour angiogenesis.

Elastase and matrix metalloproteinase inhibitors induce regression, and tenascin-C antisense prevents progression, of vascular disease

Increased expression of the glycoprotein tenascin-C (TN) is associated with progression of clinical and experimental pulmonary hypertension. In cultured smooth muscle cells (SMCs) TN is induced by matrix metalloproteinases (MMPs) and amplifies the proliferative response to growth factors. Conversely, suppression of TN leads to SMC apoptosis. We now report that hypertrophied rat pulmonary arteries in organ culture, which progressively thicken in association with cell proliferation and matrix accumulation, can be made to regress by inhibiting either serine elastases or MMPs. This effect is associated with reduced TN, suppression of SMC proliferation, and induction of apoptosis. Selective repression of TN by transfecting pulmonary arteries with antisense/ribozyme constructs also induces SMC apoptosis and arrests progressive vascular thickening but fails to induce regression. This failure is related to concomitant expansion of a SMC population, which produces an alternative cell survival alpha(v)beta(3) ligand, osteopontin (OPN), in response to pro-proliferative cues provided by a proteolytic environment. OPN rescues MMP inhibitor-induced SMC apoptosis, and alpha(v)beta(3) blockade induces apoptosis in hypertrophied arteries. Our data suggest that proteinase inhibition is a novel strategy to induce regression of vascular disease because this overcomes the pluripotentiality of SMC-matrix survival interactions and induces coordinated apoptosis and resorption of matrix.

Angiogenic histogenesis of stromal cells in hemangioblastoma: ultrastructural and immunohistochemical study

Controversy regarding the origin of characteristic stromal cells (SC) is responsible for the placement of hemangioblastoma as a single entity in the category of "tumors of uncertain histogenesis" in the current WHO classification of brain tumors. This subclassification of hemangioblastoma is, to a large extent, a consequence of a remarkable antigenic heterogeneity of SC demonstrated in many, often contradictory immunohistochemical studies. In contrast, most of the electron microscopic studies demonstrated a number of features indicating angiogenic nature of SC and, therefore, hemangioblastoma. This study reevaluated the histogenesis of SC, applying immunohistochemistry as well as electron microscopy and immunoelectron microscopy. Immunohistochemical studies confirmed most of the previous results indicating a very frequent expression of vimentin, S-100 protein, neuron-specific enolase, and cytokeratins. SC were less commonly immunoreactive for desmin, factor XIIIa, and Ricinus communis lectin receptors, and only occasionally for factor VIII and Ulex europeus lectin. They were negative for other markers of endothelial, neuronal, glial, neuroendocrine, and smooth muscle differentiation. Approximately 1% of SC showed Ki67 immunoreactivity, indicating their slight proliferative activity, consistent with the benign nature of the tumor. In contrast to the inconclusive results of the immunohistochemistry, electron microscopy demonstrated a clear relationship of SC to endothelial cells, smooth muscle cells, and pericytes. Occasional SC were found within the vascular lumina. SC often showed intracellular caveolae consistent with the formation of early capillary lumina. Moreover, occasional SC contained small Weibel-Palade bodies positive for factor VIII in immunoelectron microscopy. SC represent a heterogeneous population of abnormally differentiating mesenchymal cells of angiogenic lineage, with some morphological features of endothelium, pericytes, and smooth muscle cells. Occurrence of SC in hemangioblastoma could be related to a limited ability of angioformative stromal cells to develop an architecture of capillary lumina integrated with the vascular network of the tumor. Hemangioblastoma should be reclassified and included together with other vascular tumors of the central nervous system.

Basement membrane and growth factor gene expression in normal and diabetic human retinas

PURPOSE

Recently, we found abnormal accumulation of several extracellular matrix components in retinal basement membranes in human diabetic retinopathy (DR). Others have described increased levels of various growth factors within the vitreous of DR patients. This study examined mRNA levels of these extracellular matrix components and growth factors within human retinal tissues.

METHODS

Total retinal RNA was analyzed by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). RT-PCR products were identified by Southern blotting. Samples were normalized with respect to beta2-microglobulin cDNA. Twenty-one retinas were analyzed: 6 normal, 7 diabetic without DR and 8 diabetic with DR.

RESULTS

In diabetic retinas without DR, the expression levels of most genes were similar to normal. In DR retinas, tenascin-C mRNA expression increased compared to both normal and diabetics without DR. By RT-PCR and Northern blotting, mainly small tenascin-C mRNA isoforms were expressed, and some of them were elevated in DR retinas. Fibronectin mRNA was elevated in DR compared to normal retinas, possibly due to the overexpression of extradomain A-containing isoform (ED-A+, or cellular fibronectin). In DR retinas, gene expression of vascular endothelial growth factor and placenta growth factor was elevated compared to normal, although mRNA for these growth factors receptors (VEGFR-1/Flt-1 and VEGFR-2/KDR) did not change significantly. Transforming growth factor-beta1 mRNA also increased in DR retinas.

CONCLUSIONS

The data suggest that proliferative DR development may be associated with increased retinal expression of vascular endothelial growth factor, placenta growth factor and transforming growth factor-beta1 that possibly triggers the deposition of small tenascin-C isoforms in the blood vessel walls. Angiogenesis-stimulating tenascin-C may further promote diabetic retinal neovascularization.