Component Of Vascular Basement Membrane Research Articles

Retraction Note: Inhibition of Tumor Angiogenesis by Tumstatin: Insights into Signaling Mechanisms and Implications in Cancer Regression

Growing tumors develop additional new blood vessels to meet the demand for adequate nutrients and oxygen, a process called angiogenesis. Cancer is a highly complex disease promoted by excess angiogenesis; interfering with this process poses for an attractive approach for controlling tumor growth. This hypothesis led to the identification of endogenous angiogenesis inhibitors generated from type IV collagen, a major component of vascular basement membrane (VBM). Type IV collagen and the angiogenesis inhibitors derived from it are involved in complex roles, than just the molecular construction of basement membranes. Protease degradation of collagens in VBM occurs in various physiological and pathological conditions and produces several peptides. Some of these peptides are occupied in the regulation of functions conflicting from those of their original integral molecules. Tumstatin (α3(IV)NC1), a proteolytic C-terminal non-collagenous (NC1) domain from type IV collagen α3 chain has been highlighted recently because of its potential role in anti-angiogenesis, however its biological actions are not limited to these processes. α3(IV)NC1 inhibits proliferation by promoting endothelial cell apoptosis and suppresses diverse tumor angiogenesis, thus making it a potential candidate for future cancer therapy. The present review surveys the physiological functions of type IV collagen and discovery of α3(IV)NC1 as an antiangiogenic protein with a comprehensive overview of the knowledge gained by us towards understanding its signaling mechanisms.

Cell signaling associated with internalization of 67 kDa laminin receptor (67LR) by soluble laminin and its implication for protection against neurodegenerative diseases.

Cell signaling associated with internalization of 67 kDa laminin receptor (67LR) by soluble laminin and its implication for protection against neurodegenerative diseases.

Bilateral carotid artery stenosis causes unexpected early changes in brain extracellular matrix and blood-brain barrier integrity in mice.

Bilateral carotid artery stenosis (BCAS) is one experimental model of vascular dementia thought to preferentially impact brain white matter. Indeed, few studies report hippocampal and cortical pathology prior to 30 days post-stenosis; though it is unclear whether those studies examined regions outside the white matter. Since changes in the blood-brain barrier (BBB) permeability precede more overt brain pathology in various diseases, we hypothesized that changes within the BBB and/or BBB-associated extracellular matrix (ECM) could occur earlier after BCAS in the hippocampus, cortex and striatum and be a precursor of longer term pathology. Here, C57Bl/6 mice underwent BCAS or sham surgeries and changes in the BBB and ECM were analyzed by collagen IV (vascular basement membrane component), α5 integrin (marker of endothelial activation), claudin-5 and occludin (tight junction proteins), Evans blue (permeability marker), Ki-67 (cell proliferation marker), and GFAP and CD11b (glial cell markers) immunohistochemistry after 14 days. Significant changes in markers of cerebrovascular integrity and glial activation were detected, not only in the striatum, but also in the hippocampus and cortex. In conclusion, this study demonstrates for the first time that changes in the BBB/ECM occur shortly after BCAS and within multiple brain regions and suggests such changes might underlie the gradual development of BCAS non-white matter pathology.

Abstract TP434: Mouse Bilateral Carotid Artery Stenosis Leads to Unexpected Early Changes in Blood-Brain Barrier Integrity

Bilateral carotid artery stenosis (BCAS) is one experimental model of vascular dementia that is thought to preferentially impact brain white matter. Indeed, it is generally accepted that hippocampal and cortical pathology is not observed prior to 30 days post-injury. Since changes in the blood-brain barrier (BBB) permeability are known to precede more overt brain pathology in a variety of diseases, we hypothesized that BBB changes could occur earlier after BCAS in the hippocampus, striatum and cortex and be a precursor of longer term pathology in these regions. In our study, 3 month old male C57/Bl6 mice underwent BCAS with 0.18 mm coils or sham surgery control and changes in BBB were analyzed by collagen IV (vascular basement membrane component), claudin-5 and occludin (tight junction proteins), Evan’s blue (permeability marker), and Ki-67 (marker of cell proliferation) immunohistochemistry, protein and RNA expression levels after 3, 7, 14, or 21 days. Surprisingly, significant changes in markers of cerebrovascular integrity were detected within 7 days compared to sham animals, not only in the striatum but also in the hippocampus. Increased astrocyte and microglia activation was also observed in these regions and TUNEL staining also indicates cell death in the hippocampus within 7 days. While few changes were observed in the cortex, some of the animals did experience cortical ischemic infarcts within 14 days. In conclusion, this study demonstrates for the first time that changes in the BBB occur shortly after BCAS in multiple regions throughout the brain and suggests that such changes might underlie the gradual development of BCAS non-white matter pathology.

Abstract WP426: Early Non-white Matter Changes in Cerebrovascular Integrity in Mouse Brain Following Bilateral Carotid Artery Stenosis

Bilateral carotid artery stenosis (BCAS) is an experimental model of vascular dementia which leads to white matter lesions and cognitive dysfunction in mice. Unfortunately, with time the white matter pathology worsens and spreads to the hippocampus and cortex. While some variability in the temporal and spatial distribution of brain injury may result from inter-mouse strain differences in cerebrovascular anatomy, coil size employed to constrict the carotids and surgical technique, it is generally accepted that hippocampal, striatal and cortical pathology is not significantly present prior to 30 days. However, as changes in cerebrovascular integrity, i.e. blood-brain barrier (BBB) permeability, are known to precede more overt brain pathology in stroke, we hypothesized that BBB changes could occur earlier after BCAS in the hippocampus, striatum and cortex and be a precursor of longer term pathology in these regions. In our study, 3 month old male C57/Bl6 mice underwent BCAS with 0.18 mm coils or sham surgery control and cerebrovascular integrity was analyzed by collagen IV (vascular basement membrane component), tomato-lectin (marker of endothelial cells) and Ki-67 (marker of cell proliferation) immunohistochemistry after 7, 14, or 21 days (n=4 animals per group per day). By day 14 we noted that collagen IV staining density was significantly less in the hippocampus compared to sham controls. Surprisingly, both collagen IV and tomato-lectin staining pattern indicate blood vessel disruption in not only the hippocampus but the striatum as well. Expression of Ki-67 increased in both of these regions, and further co-labeling studies will shed light on cell specificity. Similar differences were noted at all days tested, with few changes observed in the cortex. In conclusion, this study demonstrates for the first time that changes in cerebrovascular integrity occur earlier than expected after BCAS and suggests that such changes might underlie the gradual development of BCAS non-white matter pathology.

Perlecan Domain V Is Neuroprotective and Affords Functional Improvement in a Photothrombotic Stroke Model in Young and Aged Mice

With the failure of so many pre-clinical stroke studies to translate into the clinic, there is a need to find new therapeutics to minimize the extent of cellular damage and aid in functional recovery. Domain V (DV), the c-terminal protein fragment of the vascular basement membrane component, perlecan, was recently shown to afford significant protection in multiple transient middle cerebral artery occlusion stroke models. We sought here to determine whether DV might have similar therapeutic properties in a focal photothrombosis stroke model in both young and aged mice. Young (3-month old) and aged (24-month old) mice underwent photothrombotic stroke to the motor cortex and were then treated with DV or phosphate buffered saline vehicle at different initial time points up to 7days. Stroke volume was analyzed histologically using cresyl violet and functional recovery assessed behaviorally on both the grid-walking and cylinder tasks. In young mice, DV administration resulted in a significant decrease in infarct volume when treatment started 3 or 6h post-stroke. In aged mice, DV administration was only protective when started 3h post-stroke. In addition to a decrease in the area of infarction, DV treatment was effective in significantly decreasing the number of foot-faults on the grid-walking task and improving use of the stroke-affected limb in the cylinder task in both young and aged. Previously, we have shown that DV can alter the expression profile of various astroglial markers. Consistent with our previous finding, treatment groups that showed therapeutic potential in both young and aged mice also showed an elevation in glial fibrillary acidic protein (GFAP) expression in peri-infarct regions. We conclude that DV is neuroprotective and affords significant improvements in functional recovery in both young and aged mice after focal ischemia. These data also highlight a therapeutic time-window shift that is narrower in aged compared with young mice and is associated with an elevation in GFAP expression and heightened astrogliosis.

Ang-2 upregulation correlates with increased levels of MMP-9, VEGF, EPO and TGFβ1 in diabetic eyes undergoing vitrectomy

Angiogenesis in diabetic retinopathy (DR) is a multifactorial process regulated by hypoxia-induced growth factors and inflammatory cytokines. In addition to the angiogenic switch, the proteolytic processing and altered synthesis of the extracellular matrix are critical steps in this disease. This study was performed to evaluate the levels of matrix metalloproteinase-2 and matrix metalloproteinase-9 (MMP-2 and MMP-9), angiopoietin-1 and angiopoietin-2 (Ang-1 and Ang-2), vascular endothelial growth factor (VEGF), erythropoietin (EPO) and transforming growth factor-β1 (totalTGFβ1) in the vitreous of diabetic eyes undergoing vitrectomy compared with control eyes operated because of macular hole or pucker. Prospective consecutive controlled observational study performed in the unit of vitreoretinal surgery in Finland during the years 2006-2008. Vitreous samples were collected before the start of the conventional 3-ppp vitrectomy. Vitreous MMP-2 and MMP-9, Ang-1 and Ang-2, VEGF, EPO and TGFβ1 concentrations were measured from 69 patients with Type 1 or 2 diabetes and 40 controls. Comparison of eyes with DR with controls revealed that the mean vitreous concentrations of proMMP-2 (p = 0.0015), totalMMP-2 (p = 0.0011), proMMP-9 (p = 0.00001), totalMMP-9 (p < 0.00001), Ang-2 (p < 0.00001), VEGF (p < 0.00001), EPO (p < 0.00001) and totalTGFβ1 (p = 0.000026) were significantly higher in the former group. A multivariate logistic regression analysis suggested intravitreal Ang-2 concentration being the key marker of PDR (p = 0.00025) (OR = 1507.9). The main new finding is that the intravitreal concentrations of Ang-2 correlated significantly with MMP-9, VEGF, EPO and TGFβ1 levels in diabetic eyes undergoing vitrectomy. Thus, these factors could promote retinal angiogenesis synergistically.

Type IV collagen induces expression of thrombospondin‐1 that is mediated by integrin α1β1 in astrocytes

Following brain injury, thrombospondin-1 (TSP-1) is involved in angiogenesis and synaptic recovery. In this study, we used a cold injury-model and found that TSP-1 mRNA was markedly upregulated after brain injury. Immunohistochemistry showed that TSP-1 was upregulated in both the core of the lesion and in the perilesional area of injured brain tissue. Numerous astrocytes immunopositive for glial fibrillary acidic protein (GFAP) were found in the perilesional area, and TSP-1 was also expressed in almost all astrocytes surrounding blood vessels at 4 days after injury. Next, we examined the influence of vascular basement membrane components on TSP-1 expression. When astrocytes were cultured on type IV collagen, TSP-1 was significantly upregulated compared with the expression when cells were grown on laminin, fibronectin, or poly-L-lysine. This increase occurred exclusively when astrocytes were grown on the native form of type IV collagen but not on the heat-denatured form or the non-collagenous 1 domain. Further, integrin alpha1 and beta1 mRNAs were upregulated concomitantly with GFAP mRNA, and integrin alpha1 protein was localized to the endfeet of astrocytes that surrounded blood vessels in the injured brain. Using function-blocking antibodies, we found that the effect of type IV collagen was attributed to integrin alpha1beta1 in primary astrocytes. Collectively, our results suggest that vascular basement membrane components substantially impact gene expression in astrocytes during brain tissue repair.

RETRACTED ARTICLE: Inhibition of Tumor Angiogenesis by Tumstatin: Insights into Signaling Mechanisms and Implications in Cancer Regression

Growing tumors develop additional new blood vessels to meet the demand for adequate nutrients and oxygen, a process called angiogenesis. Cancer is a highly complex disease promoted by excess angiogenesis; interfering with this process poses for an attractive approach for controlling tumor growth. This hypothesis led to the identification of endogenous angiogenesis inhibitors generated from type IV collagen, a major component of vascular basement membrane (VBM). Type IV collagen and the angiogenesis inhibitors derived from it are involved in complex roles, than just the molecular construction of basement membranes. Protease degradation of collagens in VBM occurs in various physiological and pathological conditions and produces several peptides. Some of these peptides are occupied in the regulation of functions conflicting from those of their original integral molecules. Tumstatin (α3(IV)NC1), a proteolytic C-terminal non-collagenous (NC1) domain from type IV collagen α3 chain has been highlighted recently because of its potential role in anti-angiogenesis, however its biological actions are not limited to these processes. α3(IV)NC1 inhibits proliferation by promoting endothelial cell apoptosis and suppresses diverse tumor angiogenesis, thus making it a potential candidate for future cancer therapy. The present review surveys the physiological functions of type IV collagen and discovery of α3(IV)NC1 as an antiangiogenic protein with a comprehensive overview of the knowledge gained by us towards understanding its signaling mechanisms.

Vascular Basement Membrane Components in Angiogenesis — An Act of Balance

Angiogenesis is crucial in the progression of a number of pathological conditions, such as diabetic retinopathy, rheumatoid arthritis, psoriasis, and cancer. In contrast to vessels in healthy tissues, the vasculature in these pathologies is highly unstable, constantly dissolving and renewing. Characteristically, vessels in pathologies have discontinuous basement membrane (BM) coverage. The consequences of shifts in BM density and composition are still relatively unknown. Several studies have illustrated that partial loss of the vascular BM during development results in the widening of vessels. This has been suggested to be a result of reduced mechanical resistance to the force inflicted by the blood pressure. However, recent data indicate that depletion of BM laminins (LMs) leads to enlarged vessels even in the absence of cardiac activity and blood pressure. A key question is whether single BM components or fragments thereof play distinct roles in the angiogenic process, or if it is the balance between the different components of the BM that guides the morphology of the new vessel.

Inhibition of laminin-8 in vivo using a novel poly(malic acid)-based carrier reduces glioma angiogenesis

We have previously shown that laminin-8, a vascular basement membrane component, was overexpressed in human glioblastomas multiforme and their adjacent tissues compared to normal brain. Increased laminin-8 correlated with shorter glioblastoma recurrence time and poor patient survival making it a potential marker for glioblastoma diagnostics and prediction of disease outcome. However, laminin-8 therapeutic potential was unknown because the technology of blocking the expression of multi-chain complex proteins was not yet developed. To inhibit the expression of laminin-8 constituents in glioblastoma in vitro and in vivo, we used Polycefin, a bioconjugate drug delivery system based on slime-mold Physarum polycephalum-derived poly(malic acid). It carries an attached transferrin receptor antibody to target tumor cells and to deliver two conjugated morpholino antisense oligonucleotides against laminin-8 alpha4 and beta1 chains. Polycefin efficiently inhibited the expression of both laminin-8 chains by cultured glioblastoma cells. Intracranial Polycefin treatment of human U87MG glioblastoma-bearing nude rats reduced incorporation of both tumor-derived laminin-8 chains into vascular basement membranes. Polycefin was thus able to simultaneously inhibit the expression of two different chains of a complex protein. The treatment also significantly reduced tumor microvessel density (p < 0.001) and area (p < 0.001) and increased animal survival (p < 0.0004). These data suggest that laminin-8 may be important for glioblastoma angiogenesis. Polycefin, a versatile nanoscale drug delivery system, was suitable for in vivo delivery of two antisense oligonucleotides to brain tumor cells causing a reduction of glioblastoma angiogenesis and an increase of animal survival. This system may hold promise for future clinical applications.

Matrix metalloproteinases in the process of invasion and metastasis of breast cancer

Metastatic cascade in malignant tumors, including breast cancer, starts with localized invasion of the host tissue. This process, requiring that tumor cells separate from each other, includes loss of homotypic and heterotypic cell adhesion and cell-cell contact inhibition, acquisition of motility, exacerbated by "epithelial-to-mesenchymal transition", and production of proteolytic enzymes which degrade basal membrane and extracellular matrix. In this sense, aside from urokinase type plasminogen activator, increased expression and activity of matrix metalloproteinases (MMPs) is one of the earliest and most sustained events in tumor progression, playing a role in angiogenesis, invasion and metastasis. MMPs are a family of 23 zinc metalloproteinases, secreted as latent pro-enzymes, activated by proteolytic cleavage, and inhibited by the tissue inhibitors of metalloproteinases. The most commonly connected MMPs with the processes of metastasis are MMP-2 (gelatinase A) and MMP-9 (gelatinase B), due to their ability to degrade collagen type IV, major component of vascular basement membrane. MMP-2 and MMP-9 are also required for the switch to the "angiogenic phenotype" during tumor progression and activation of dormant tumor cells. The association of the increase in serum MMP-2 and MMP-9 activity and clinical stage suggests the usefulness of these parameters as markers in the follow-up and prognosis of breast cancer patients. The concept of "stromal-directed therapy" of cancer, with MMP-inhibitors directed against MMPs as targets, is based on the observed MMP up-regulation in tumors.

Endostatin binds biglycan and LDL and interferes with LDL retention to the subendothelial matrix during atherosclerosis

Retention of lipoproteins to proteoglycans in the subendothelial matrix (SEM) is an early event in atherosclerosis. We recently reported that collagen XVIII and its proteolytically released fragment endostatin (ES) are differentially depleted in blood vessels affected by atherosclerosis. Loss of collagen XVIII/ES in atherosclerosis-prone mice enhanced plaque neovascularization and increased the vascular permeability to lipids by distinct mechanisms. Impaired endothelial barrier function increased the influx of lipoproteins across the endothelium; however, we hypothesized that enhanced retention might be a second mechanism leading to the increased lipid content in atheromas lacking collagen XVIII. We now demonstrate a novel property of ES that binds both the matrix proteoglycan biglycan and LDL and interferes with LDL retention to biglycan and to SEM. A peptide encompassing the alpha coil in the ES crystal structure mediates the major blocking effect of ES on LDL retention. ES inhibits the macrophage uptake of biglycan-associated LDL indirectly by interfering with LDL retention to biglycan, but it has no direct effect on the macrophage uptake of native or modified lipoproteins. Thus, loss of ES in advanced atheromas enhances lipoprotein retention in SEM. Our data reveal a third protective role of this vascular basement membrane component during atherosclerosis.

Basement membranes: structure, assembly and role in tumour angiogenesis.

In recent years, the basement membrane (BM)--a specialized form of extracellular matrix (ECM)--has been recognized as an important regulator of cell behaviour, rather than just a structural feature of tissues. The BM mediates tissue compartmentalization and sends signals to epithelial cells about the external microenvironment. The BM is also an important structural and functional component of blood vessels, constituting an extracellular microenvironment sensor for endothelial cells and pericytes. Vascular BM components have recently been found to be involved in the regulation of tumour angiogenesis, making them attractive candidate targets for potential cancer therapies.

Extracellular Matrix-derived Peptide Binds to αvβ3 Integrin and Inhibits Angiogenesis

Angiogenesis is associated with several pathological disorders as well as with normal physiological maintenance. Components of vascular basement membrane are speculated to regulate angiogenesis in both positive and negative manner. Recently, we reported that tumstatin (the NC1 domain of alpha 3 chain of type IV collagen) and its deletion mutant tum-5 possess anti-angiogenic activity. In the present study, we confirm that the anti-angiogenic activity of tumstatin and tum-5 is independent of disulfide bond requirement. This property of tum-5 allowed us to use overlapping synthetic peptide strategy to identify peptide sequence(s) which possess anti-angiogenic activity. Among these peptides, only the T3 peptide (69-88 amino acids) and T7 peptide (74-98 amino acids) inhibited proliferation and induced apoptosis specifically in endothelial cells. The peptides, similar to tumstatin and the tum-5 domain, bind and function via alpha(v)beta(3) in an RGD-independent manner. Restoration of a disulfide bond between two cysteines within the peptide did not alter the anti-angiogenic activity. Additionally, these studies show that tumstatin peptides can inhibit proliferation of endothelial cells in the presence of vitronectin, fibronectin, and collagen I. Anti-angiogenic effect of the peptides was further confirmed in vivo using a Matrigel plug assay in C57BL/6 mice. Collectively, these experiments suggest that the anti-angiogenic activity of tumstatin is localized to a 25-amino acid region of tumstatin and it is independent of disulfide bond linkage. Structural features and potency of the tumstatin peptide make it highly feasible as a potential anti-cancer drug.

Identification of the Anti-angiogenic Site within Vascular Basement Membrane-derived Tumstatin

Components of vascular basement membrane are involved in regulating angiogenesis. Recently, tumstatin (the NC1 domain of alpha3 chain of type IV collagen) was identified as possessing anti-angiogenic activity. In the present study, the anti-angiogenic activity of tumstatin was localized to the putative 54-132-amino acid Tum-5 domain, and the activity mediated by alpha(v)beta(3) integrin interaction in an RGD-independent manner. The recombinant Tum-5 produced in Escherichia coli and Pichia Pastoris specifically inhibited proliferation and caused apoptosis of endothelial cells with no significant effect on nonendothelial cells. Tum-5 also inhibited tube formation of endothelial cells on Matrigel and induced G1 endothelial cell cycle arrest. Moreover, anti-angiogenic effect of Tum-5 was also examined in vivo using both a Matrigel plug assay in C57BL/6 mice and human prostate cancer (PC-3) xenografts in nude mice. The in vivo results demonstrate that Tum-5 at 1 mg/kg significantly inhibited growth of PC-3 tumors in association with a decrease in CD31 positive vasculature. These in vivo studies also show that, at molar equivalents, human Tum-5 is at least 10-fold more active than human endostatin. In addition, these studies for the first time suggest that through the action of endogenous inhibitors, alpha(v)beta(3) integrin may also function as a negative regulator of angiogenesis. Taken together, these findings demonstrate that Tum-5, a domain derived from tumstatin, is an effective inhibitor of tumor-associated angiogenesis and a promising candidate for the treatment of cancer.

Distinct Antitumor Properties of a Type IV Collagen Domain Derived from Basement Membrane

Vascular basement membrane is an important structural component of blood vessels. During angiogenesis this membrane undergoes many alterations and these changes are speculated to influence the formation of new capillaries. Type IV collagen is a major component of vascular basement membrane, and recently we identified a fragment of type IV collagen alpha2 chain with specific anti-angiogenic properties (Kamphaus, G. D., Colorado, P. C., Panka, D. J., Hopfer, H., Ramchandran, R., Torre, A., Maeshima, Y., Mier, J. W., Sukhatme, V. P., and Kalluri, R. (2000) J. Biol. Chem. 275, 1209-1215). In the present study we characterize two different antitumor activities associated with the noncollagenous 1 (NC1) domain of the alpha3 chain of type IV collagen. This domain was previously discovered to possess a C-terminal peptide sequence (amino acids 185-203) that inhibits melanoma cell proliferation (Han, J., Ohno, N., Pasco, S., Monboisse, J. C., Borel, J. P., and Kefalides, N. A. (1997) J. Biol. Chem. 272, 20395-20401). In the present study, we identify the anti-angiogenic capacity of this domain using several in vitro and in vivo assays. The alpha3(IV)NC1 inhibited in vivo neovascularization in matrigel plug assays and suppressed tumor growth of human renal cell carcinoma (786-O) and prostate carcinoma (PC-3) in mouse xenograft models associated with in vivo endothelial cell-specific apoptosis. The anti-angiogenic activity was localized to amino acids 54-132 using deletion mutagenesis. This anti-angiogenic region is separate from the 185-203 amino acid region responsible for the antitumor cell activity. Additionally, our experiments indicate that the antitumor cell activity is not realized until the peptide region is exposed by truncation of the alpha3(IV)NC1 domain, a requirement not essential for the anti-angiogenic activity of this domain. Collectively, these results effectively highlight the distinct and unique antitumor properties of the alpha3(IV)NC1 domain and the potential use of this molecule for inhibition of tumor growth.

Role of vascular basement membrane components in diabetic microangiopathy.

The complications of diabetic microangiopathy have been well documented clinically for many years; however, the specific cellular mechanisms that lead to the dysfunction of small vessels in diabetes are unknown. Histopathological studies on diabetic microangiopathy have established thickened vascular basement membrane as one of the first and foremost structural abnormalities. Evidence suggests that this fundamental structural lesion develops, at least in part, from excess accumulation of basement membrane material in the vessel walls. Several vascular basement membrane components have been identified whose expression is up-regulated in diabetes. Enzymes responsible for the degradation of basement membrane components have also been reported to exhibit reduced activity. Strategies are being developed to regulate the abnormal accumulation of extracellular matrix (ECM) components in diabetic microangiopathy. In experimental diabetes, aldose reductase inhibitors have been found to be effective in preventing vascular basement membrane thickening when applied soon after the onset of hyperhexosemia. Clinical trials have been initiated with inhibitors of protein kinase C, an enzyme that up-regulates the synthesis of ECM components in diabetes. Currently, gene therapy strategies are also being developed to inhibit specific gene expression responsible for excess ECM synthesis in diabetes. Recent studies in the authors' laboratory have shown the applicability and efficacy of antisense oligonucleotides toward reducing vascular basement membrane component synthesis. Several gene regulatory approaches are currently being developed to modulate and prevent vascular basement membrane component synthesis. Such strategies may help identify key events that underlie the complex developmental stages of diabetic microangiopathy.

Reduced vascular basement-membrane immunostaining in mucinous tumours of the ovary.

Tumour vasculature is heterogeneous, exhibiting a range of vessel densities and the vascular basement membrane (VBM) of tumour blood vessels may be fragmented or absent. Increased microvessel density (MVD) has been reported in mucinous ovarian tumours as compared with other histologic sub-types. We hypothesized that VBM immunostaining differs between regions of the ovarian tumour vasculature and between ovarian tumour types exhibiting different MVD. Serial sections from 56 ovarian tumours were immunostained using antibodies to the VBM components collagen IV, heparan sulphate proteoglycan and laminin, and the endothelial cell marker CD31. Regions of high and average MVD were selected, and the number of vessels positive for each VBM component were counted and expressed as a percentage of the number of CD31-positive vessels. The percentage of VBM-positive vessels did not differ between the high and average MVD regions of borderline or malignant, mucinous and serous tumours. The percentage of VBM-positive vessels in mucinous tumours was less than that observed in malignant and borderline serous tumours and benign tumours (p < 0.02). Possible explanations for these findings are (i) that VBM turnover is similar throughout the vasculature; (ii) that the VBM is present both during angiogenesis and in the newly formed vessels of high MVD regions; or (iii) that an alternative angiogenesis mechanism is utilized in different ovarian tumour types, or even between different regions of the same tumour.

Circulating levels of 7 S domain of type IV collagen and atrial natriuretic peptide in normotensive type 2 diabetic patients with or without retinopathy.

Thickening of the basement membrane and other structural alterations of the vascular walls occur frequently in patients with diabetes. The vascular response to atrial natriuretic peptide (ANP) is also altered in these patients. Abnormal vascular response in diabetes may be due to alteration of vascular physicochemical properties induced by accumulation of components of vascular basement membrane. The aim of this study was to evaluate the relationship between circulating levels of the 7 S domain of type IV collagen (7 S-collagen), and ANP in normotensive type 2 diabetic patients with or without retinopathy. Forty-one normotensive type 2 diabetic patients (n = 19 with and n = 22 without retinopathy) and 18 age-matched control subjects participated in the study. Serum 7 S-collagen and plasma ANP levels were measured by radioimmunoassays. Serum 7 S-collagen (4.4 +/- 0.1 vs 3.5 +/- 0.1 ng/ml; p < 0.01) levels and plasma ANP (20.8 +/- 1.0 vs 15.5 +/- 1.0 pg/ml; p < 0.01) were significantly higher in diabetic patients than in normal subjects. Serum 7 S-collagen increased significantly in diabetic patients without retinopathy compared with normal subjects (4.1 +/- 0.1 vs 3.5 +/- 0.1 ng/ml; p < 0.01). Diabetic patients with retinopathy showed significantly higher circulating concentrations of 7 S-collagen (4.6 +/- 0.1 vs 4.1 +/- 0.1 ng/ml; p < 0.01) and ANP (22.9 +/- 1.4 vs 18.9 +/- 1.3 pg/ml; p < 0.05) than those without retinopathy. There was a significant and positive correlation (r = 0.51, p < 0.01) between the circulating levels of 7 S-collagen and ANP in all patients. The results of this investigation showed that increased circulating levels of ANP correlate with the abnormal metabolism of the vascular basement membrane observed in diabetic patients with microangiopathy.