Survey for the presence of a vitronectin-like protein in micro- and macroalgae and cyanobacteria.

Vitronectin (Vn) is a glycoprotein that serves a wide variety of roles in multicellular organisms. It was first identified in multicellular animals but has also been isolated from land plants and some algae, where it appears to serve as an extracellular adhesive molecule. In order to further elucidate presence and localization of a Vn-like protein and its potential role in algae, we surveyed different morphological regions of 24 species of macro- and microalgae and three species of cyanobacteria for the presence of a Vn-like protein. Vn-like proteins were not detected in any of the species of cyanobacteria, microalgae or Rhodophyta investigated. They were detected in several species of the Phaeophyceae and Chlorophyta where their localization was limited to the holdfast and rhizoids of these organisms, respectively. Detection of a Vn-like protein (between 0.0125 and 0.097 µg · µL-1 protein extract) was therefore limited to locations associated with substrate attachment.

A detection method in living plant cells for rapidly monitoring the response of plants to exogenous lanthanum.

The pollution of rare earth elements (REEs) in ecosystem is becoming more and more serious, so it is urgent to establish methods for monitoring the pollution of REEs. Monitoring environmental pollution via the response of plants to pollutants has become the most stable and accurate method compared with traditional methods, but scientists still need to find the primary response of plants to pollutants to improve the sensitivity and speed of this method. Based on the facts that the initiation of endocytosis is the primary cellular response of the plant leaf cells to REEs and the detection of endocytosis is complex and expensive, we constructed a detection method in living plant cells for rapidly monitoring the response of plants to exogenous lanthanum [La(III), a representative of REEs] by designing a new immuno-electrochemical method for detecting the content change in extracellular vitronectin-like protein (VN) that are closely related to endocytosis. Results showed that when 30 µM La(III) initiated a small amount of endocytosis, the content of extracellular VN increased by 5.46 times, but the structure and function of plasma membrane were not interfered by La(III); when 80 µM La(III) strongly initiated a large amount of endocytosis, the content of extracellular VN increased by 119 times, meanwhile, the structure and function of plasma membrane were damaged. In summary, the detection method can reflect the response of plants to La(III) via detecting the content change in extracellular VN, which provides an effective and convenient way to monitor the response of plants to exogenous REEs.

Serological comparative proteomics analysis of mitochondrial autoantibody-negative and -positive primary biliary cirrhosis.

Here, we investigated the pathogenesis of primary biliary cirrhosis (PBC) by using 2D-DIGE to analyze serological differences between anti-mitochondrial antibody (AMA)-positive and -negative PBC patients. The study comprised 30 patients with PBC; 20 AMA-positive and ten AMA-negative patients matched for age, sex, and pathological stage. A screening group (four AMA-positive and four AMA-negative patients) was used for 2D-DIGE. Protein spots that were differently abundant between the two groups were identified via dye intensity and MS. Nine candidate proteins were identified from these spots. Western blotting was used to verify two of the identified proteins, serum amyloid P-component (SAP) and vitronectin (VN). VN levels were significantly higher in the sera of AMA-negative PBC patients (p < 0.01), whereas no significant difference was found between the two groups for SAP. To our knowledge, this is the first study to use serological comparative proteomics to explore differences between AMA-positive and -negative PBC patients. VN levels were higher in AMA-negative PBC patients, and this finding could be related to the more severe bile duct destruction observed in this group.

Imaging mass spectrometry analysis of renal amyloidosis biopsies reveals protein co-localization with amyloid deposits.

Amyloidosis is a heterogeneous group of protein misfolding diseases characterized by deposition of amyloid proteins. The kidney is frequently affected, especially by immunoglobulin light chain (AL) and serum amyloid A (SAA) amyloidosis as the most common subgroups. Current diagnosis relies on histopathological examination, Congo red staining, or electron microscopy. Subtyping is done by immunohistochemistry; however, commercially available antibodies lack specificity. The purpose of this study was to identify and map amyloid proteins in formalin-fixed paraffin-embedded tissue sections using matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis in an integrated workflow. Renal amyloidosis and non-amyloidosis biopsies were processed for histological and MS analysis. Mass spectra corresponding to the congophilic areas were directly linked to the histological and MS images for correlation studies. Peptides for SAA and AL were detected by MALDI IMS associated to Congo red-positive areas. Sequence determination of amyloid peptides by LC-MS/MS analysis provided protein distribution and identification. Serum amyloid P component, apolipoprotein E, and vitronectin proteins were identified in both AA and AL amyloidosis, showing a strong correlation with Congo red-positive regions. Our findings highlight the utility of MALDI IMS as a new method to type amyloidosis in histopathological routine material and characterize amyloid-associated proteins that may provide insights into the pathogenetic process of amyloid formation.

Spike-in SILAC proteomic approach reveals the vitronectin as an early molecular signature of liver fibrosis in hepatitis C infections with hepatic iron overload.

Hepatitis C virus (HCV)-induced iron overload has been shown to promote liver fibrosis, steatosis, and hepatocellular carcinoma. The zonal-restricted histological distribution of pathological iron deposits has hampered the attempt to perform large-scale in vivo molecular investigations on the comorbidity between iron and HCV. Diagnostic and prognostic markers are not yet available to assess iron overload-induced liver fibrogenesis and progression in HCV infections. Here, by means of Spike-in SILAC proteomic approach, we first unveiled a specific membrane protein expression signature of HCV cell cultures in the presence of iron overload. Computational analysis of proteomic dataset highlighted the hepatocytic vitronectin expression as the most promising specific biomarker for iron-associated fibrogenesis in HCV infections. Next, the robustness of our in vitro findings was challenged in human liver biopsies by immunohistochemistry and yielded two major results: (i) hepatocytic vitronectin expression is associated to liver fibrogenesis in HCV-infected patients with iron overload; (ii) hepatic vitronectin expression was found to discriminate also the transition between mild to moderate fibrosis in HCV-infected patients without iron overload.

Variability of the paracrine-induced osteoclastogenesis by human breast cancer cell lines.

Breast cancer frequently metastasizes to the bone, often leading to the formation of osteolytic lesions. This work compares the paracrine-induced osteoclastogenesis mediated by four human breast cancer cell lines, the estrogen-receptor positive T47D and MCF-7 and the estrogen-negative SK-BR-3 and Hs-578T cell lines. Human osteoclast precursor cells were cultured in the presence of conditioned media from the breast cancer cell lines (10% and 20%), collected at different culture periods (48 h, 7 days, and 14 days). Cultures performed in the absence or the presence of M-CSF and RANKL served as negative and positive control, respectively. Results showed that the cell lines differentially expressed several osteoclastogenic genes. All cell lines exhibited a significant osteoclastogenic potential, evidenced by a high TRAP activity and number of osteoclastic cells, expression of several osteoclast-related genes, and, particularly, a high calcium phosphate resorption activity. Differences among the osteoclastogenic potential of the cell lines were noted. T47D and MCF-7 cell lines displayed the highest and the lowest osteoclastogenic response, respectively. Despite the variability observed, MEK and NF-κB signaling pathways, and, at a lesser extent, PGE2 production, seemed to have a central role on the observed osteoclastogenic response. In conclusion, the tested breast cancer cell lines exhibited a high osteoclastogenic potential, although with some variability on the cell response profile, a factor to be considered in the development of new therapeutic approaches for breast cancer-induced bone metastasis.

The effect of cyclic mechanical strain on the expression of adhesion-related genes by periodontal ligament cells in two-dimensional culture.

BACKGROUND AND OBJECTIVE: Cell adhesion plays important roles in maintaining the structural integrity of connective tissues and sensing changes in the biomechanical environment of cells. The objective of the present investigation was to extend our understanding of the effect of cyclic mechanical strain on the expression of adhesion-related genes by human periodontal ligament cells. MATERIAL AND METHODS: Cultured periodontal ligament cells were subjected to a cyclic in-plane tensile deformation of 12% for 5 s (0.2 Hz) every 90 s for 6-24 h in a Flexercell FX-4000 Strain Unit. The following parameters were measured: (i) cell viability by the MTT assay; (ii) caspase-3 and -7 activity; and (iii) the expression of 84 genes encoding adhesion-related molecules using real-time RT-PCR microarrays. RESULTS: Mechanical stress reduced the metabolic activity of deformed cells at 6 h, and caspase-3 and -7 activity at 6 and 12 h. Seventy-three genes were detected at critical threshold values < 35. Fifteen showed a significant change in relative expression: five cell adhesion molecules (ICAM1, ITGA3, ITGA6, ITGA8 and NCAM1), three collagen α-chains (COL6A1, COL8A1 and COL11A1), four MMPs (ADAMTS1, MMP8, MMP11 and MMP15), plus CTGF, SPP1 and VTN. Four genes were upregulated (ADAMTS1, CTGF, ICAM1 and SPP1) and 11 downregulated, with the range extending from a 1.76-fold induction of SPP1 at 12 h to a 2.49-fold downregulation of COL11A1 at 24 h. CONCLUSION: The study has identified several mechanoresponsive adhesion-related genes, and shown that onset of mechanical stress was followed by a transient reduction in overall cellular activity, including the expression of two apoptosis 'executioner' caspases.

Over-expression of vitronectin correlates with impaired survival in gastric cancers.

ABSTRACT: Over-expression of vitronectin (VN) is associated with tumorigenesis. The present study aimed to evaluate the prognostic value of VN expression in gastric cancer.The least absolute shrinkage and selection operator analysis was performed to screen the hub gene from The Cancer Genome Atlas gastric cancer patients with complete follow-up data, and 347 patients were finally included. Moreover, 102 patients were enrolled from the Affiliated Fuzhou First Hospital of Fujian Medical University. VN expression in paired gastric cancer and adjacent gastric normal tissues was detected using immunohistochemistry, and the clinicopathological significance of VN expression was evaluated. The prognostic significance of VN expression in gastric cancer patients was evaluated using by Kaplan-Meier method and Cox regression analysis and confirmed using Oncomine.VN was the prognosis relative gene which screened by The Cancer Genome Atlas dataset. Moreover, we identified the VN expression in an external dataset by immunohistochemistry. The result demonstrated that VN expression was remarkedly elevated in gastric cancer tissues (P < .001). High VN expression correlated with higher pathological Tumor-Node-Metastasis stage, and poorer survival outcomes. Cox regression analysis showed that VN expression was independently predictive of overall survival (OS) and disease-free survival (P = .004, P < .001, respectively). A prognostic risk score for OS was built based on VN expression. A meta-analysis from Oncomine datasets revealed that significantly lower VN mRNA levels in gastric cancer correlated with poorer OS.VN expression could be a prognostic marker of gastric cancer.

Initial formation of IGROV1 ovarian cancer multicellular aggregates involves vitronectin.

Ovarian cancer progression is frequently associated with the development of malignant ascites. Multicellular aggregates of carcinoma cells (spheroids) found within ascites are thought to be able to promote peritoneal carcinomatosis. We have previously demonstrated the involvement of the vitronectin/alphav integrin adhesive system in the dissemination of ovarian cancer cells and continue to investigate the influence of these molecules by studying their role(s) in spheroid behavior. The aim of this study was to generate ovarian cancer multicellular aggregates and to focus on the role of vitronectin and alphav integrins in their initiation. IGROV1 cancer cells cultured in the absence of adhesive substratum formed multicellular aggregates comparable to spheroids. After 21 days, a fraction of the cells within clusters remained viable and proliferated recurrently. Within the multicellular aggregates, vitronectin and alphav integrins were co-localized at intercellular sites, suggesting their involvement in cell-cell interactions. Initial formation of IGROV1 aggregates was inhibited using anti-vitronectin and anti-alphav integrin blocking antibodies or the cyclic peptide cRGDfV. Vitronectin expression persisted during cluster disaggregation on fibronectin. These results demonstrate the ability of IGROV1 cells to generate multicellular aggregates and point to a contributory role for the vitronectin/alphav integrin system in the initial step of this process. These events could represent a prerequisite for further dissemination.

Expression of extracellular matrix-proteins in perisellar connective tissue and dura mater.

PURPOSE: To describe the pattern of expression of extracellular matrix (ECM) proteins in perisellar connective tissue. METHODS: Dural and perisellar specimens from ten individuals were investigated immunohistochemically for collagens I to IV, tenascin, fibronectin, elastin, laminin, and vitronectin. FINDINGS: Collagen I and III and fibronectin were strongly expressed and collagen IV, tenascin, and vitronectin were moderately expressed in the boundaries of the sella and around the CS. In six of nine specimens from the anterior boundary of the sella, and in 11 of 19 samples from the lateral boundary of the sella (medial wall of CS), two different layers could be detected by the expression of different ECM proteins. None of the antigens generally allowed differentiation between two layers of the pituitary envelope. CONCLUSIONS: The pituitary boundary may consist of a single or a double layer, infrequently differentiated from each other by the expression of different ECM proteins.

Glomeruli of Dense Deposit Disease contain components of the alternative and terminal complement pathway.

Dense Deposit Disease (DDD), or membranoproliferative glomerulonephritis type II, is a rare renal disease characterized by dense deposits in the mesangium and along the glomerular basement membranes that can be seen by electron microscopy. Although these deposits contain complement factor C3, as determined by immunofluorescence microscopy, their precise composition remains unknown. To address this question, we used mass spectrometry to identify the proteins in laser microdissected glomeruli isolated from paraffin-embedded tissue of eight confirmed cases of DDD. Compared to glomeruli from five control patients, we found that all of the glomeruli from patients with DDD contain components of the alternative pathway and terminal complement complex. Factor C9 was uniformly present as well as the two fluid-phase regulators of terminal complement complex clusterin and vitronectin. In contrast, in nine patients with immune complex-mediated membranoproliferative glomerulonephritis, glomerular samples contained mainly immunoglobulins and complement factors C3 and C4. Our study shows that in addition to fluid-phase dysregulation of the alternative pathway, soluble components of the terminal complement complex contribute to glomerular lesions found in DDD.

Proteomic identification of differentially expressed proteins in aortic wall of patients with ruptured and nonruptured abdominal aortic aneurysms.

OBJECTIVE: To compare the basic proteomic composition of abdominal aortic aneurysm (AAA) wall tissue in patients with nonruptured and ruptured aneurysms. METHODS: A proteomic approach with two-dimensional gel electrophoresis (2D-PAGE) and mass spectrometry (MS) was used to identify differentially expressed proteins in AAA tissue from nine patients with nonruptured and eight patients with ruptured AAA. Computerized image analysis was used to detect protein spots. Differentially expressed protein spots were in-gel digested and identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Western blot analysis was used to confirm differential expression. RESULTS: Seven differentially expressed proteins were detected among 745 protein spots, selecting spots whose average relative volumes differed more than twofold between the nonruptured and the ruptured group. Four protein spots were up-regulated in the ruptured group, and three were down-regulated. Five of the spots were identified. Among the upregulated spots, No. 605 was identified as peroxiredoxin-2. The up-regulation was confirmed by Western blotting. No. 381 was identified as an actin fragment. Two spots, Nos. 719 and 499, could not be identified. Among the down-regulated protein spots, No. 130 contained two peptides; one reliably determined peptide, FEDGVLDPDYPR, is found in vitronectin. Another peptide, QIDNPDYK, was borderline significant and found in calreticulin. The down-regulation of vitronectin was confirmed by Western blotting. Spot Nos. 193 and 199 both contained peptides from albumin with actin also present in No. 199. CONCLUSION: The identified proteins suggest that the aortic wall of ruptured aneurysms responds to a stressful condition and that proteolytic degradation of the cytoskeleton and connective tissue may be part of the response.

Vitronectin and its receptors partly mediate adhesion of ovarian cancer cells to peritoneal mesothelium in vitro.

Epithelial ovarian cancer cells metastasize by implanting onto the peritoneal mesothelial surface of the abdominal cavity. Adhesive molecules that lead to this implantation remain unclear. The aim of our study was to focus on the role of vitronectin (Vn) and its receptors, alpha(v) integrins and urokinase plasminogen activator receptor (uPAR), in the interactions of ovarian adenocarcinoma cells (IGROV1 and SKOV3 cell lines) with mesothelial cells (MeT-5A cell line and primary cultures). For all cell lines, immunofluorescence staining disclosed the presence of Vn over the whole cell surface and in thin continuous deposits underlining the cell periphery. Recruitment of Vn receptors to cell-cell contact sites was also revealed. We developed two distinct methods for the evaluation of in vitro cell-cell adhesion using cocultures of the tumor and mesothelial cells. Both adhesion assays revealed a strong ability of ovarian cancer cells to adhere preferentially to mesothelial intercellular junctions. Adhesion of ovarian carcinoma cells to mesothelial cells was significantly inhibited using anti-Vn-, -alpha(v)-integrin- and -uPAR-blocking antibodies or cyclic peptide cRGDfV. These results evidence the ability of ovarian carcinoma cells to bind to peritoneal mesothelium in vitro and strongly suggest that Vn and its receptors contribute to this crucial event.

Collagen IV, laminin, fibronectin, vitronectin. Comparative study in basal cell carcinoma. Correlation between basement membrane molecules expression and invasive potential.

AIM: Basal cell carcinoma (BCC) is a malignant carcinoma arising by cells of epidermal basal layer and adnexal epithelium. It appears intimately connected with a stromale component that holds a relevant role for tumour's evolution. It occurs frequently on sun-exposed regions, and is considered as low potential for metastasis, whereas its local invasion, destruction and recurrence are well known. METHODS: Particularly formalin-fixed, paraffin-embedded tissue from 40 cases of BCC, 20 recurring and 20 not recurring, had been studied, with immunohistochemical techniques to value the distribution of intrinsic and extrinsic components of basal membrane. RESULTS: The immunohistochemical examination showed collagen IV and laminin continuous positivity in peripheral cells, seating around neoplastic nests of 62.5% not recurring BCC. The same antigens exhibited discontinuous positivity in cells with non distinguished borders, seating around nests of 85% micronodular recurring BCC. The valuation of fibronectin and vitronectin could have a more significant prognostic value. Fibronectin in fact appeared hyper-expressed in peritumoral stroma of 80% recurring BCC, vitronectin appeared less expressed than normally in peritumoral stroma of 95% recurring BCC. CONCLUSION: A correlation between basal membrane's break and carcinoma's recurrence has been noticed. This shows the utility of other prognostic factors helping the valuation of malignant progression.

[The range and potential contribution of irreversibly adsorbed proteins on the surface of artificial implants]. / Spektr i potentsial'naia rol' neobratimo adsorbirovannykh belkov na poverkhnosti iskusstvennykh implantiruemykh materialov.

Protein adsorption is the first stage of the interaction between prosthetic materials with tissues of the body. They undergo conformational changes depending on the chemical composition and the nanotopography surface. Adsorbed proteins induce adhesion and alter the functional state of migrating cells. Plasma samples from patients were incubated with such matrices as titanium, polypropylene or polyester with fluoropolymer coating meshes. Bound peptides were analyzed by electrophoresis. Qualitative analysis of the peptides extracted from the gel was performed by chromatography-mass spectrometry. Quantitative analysis was performed by the MRM method. More than 60 proteins were identified on the analyzed surfaces. Quantitative analysis showed preferential adsorption of vitronectin, albumin, fibrinogen a-chain, C1ѕ component of the complement system. Vitronectin had the maximum relative protein content. Since biocompatibility of the analyzed materials varies considerably this variability may be attributed to conformational changes occurring with vitronectin during its irreversible adsorption.

The nature and consequence of vitronectin interaction in the non-compromised contact lens wearing eye.

PURPOSE: The aim of this work was to investigate the locus and extent of vitronectin (Vn) deposition on ex vivo contact lenses and to determine the influence of wear modality together with surface and bulk characteristics of the lens material. METHODS: The quantity and location of Vn deposition on the surfaces of contact lens materials was investigated using a novel on-lens cell attachment assay technique. RESULTS: Vn mapping showed that deposition resulted from lens-corneal interaction rather than solely from the tear film. Higher cell counts on the posterior surface of the lenses were determined in comparison to the anterior surface. Overall gross Vn deposition was greater for high water content-low modulus materials (117±4 average cell count per field) than low water content-high modulus materials (88±6 average cell count per field). CONCLUSIONS: The role of Vn in plasmin regulation and upregulation is widely recognised. The findings in this paper suggest that the locus of Vn on the contact lens surface, which is affected by material properties such as modulus, is potentially an important factor in the generation of plasmin in the posterior tear film. Consequently, the potential for materials to affect Vn deposition will influence lens-induced inflammatory processes.

Rheumatic Heart Disease and Myxomatous Degeneration: Differences and Similarities of Valve Damage Resulting from Autoimmune Reactions and Matrix Disorganization.

Autoimmune inflammatory reactions leading to rheumatic fever (RF) and rheumatic heart disease (RHD) result from untreated Streptococcus pyogenes throat infections in individuals who exhibit genetic susceptibility. Immune effector mechanisms have been described that lead to heart tissue damage culminating in mitral and aortic valve dysfunctions. In myxomatous valve degeneration (MXD), the mitral valve is also damaged due to non-inflammatory mechanisms. Both diseases are characterized by structural valve disarray and a previous proteomic analysis of them has disclosed a distinct profile of matrix/structural proteins differentially expressed. Given their relevance in organizing valve tissue, we quantitatively evaluated the expression of vimentin, collagen VI, lumican, and vitronectin as well as performed immunohistochemical analysis of their distribution in valve tissue lesions of patients in both diseases. We identified abundant expression of two isoforms of vimentin (45 kDa, 42 kDa) with reduced expression of the full-size protein (54 kDa) in RHD valves. We also found increased vitronectin expression, reduced collagen VI expression and similar lumican expression between RHD and MXD valves. Immunohistochemical analysis indicated disrupted patterns of these proteins in myxomatous degeneration valves and disorganized distribution in rheumatic heart disease valves that correlated with clinical manifestations such as valve regurgitation or stenosis. Confocal microscopy analysis revealed a diverse pattern of distribution of collagen VI and lumican into RHD and MXD valves. Altogether, these results demonstrated distinct patterns of altered valve expression and tissue distribution/organization of structural/matrix proteins that play important pathophysiological roles in both valve diseases.

Degradation of distinct forms of multimeric vitronectin by human fibroblasts.

The plasma protein vitronectin is thought to be an important regulator of extravascular plasminogen activation. In previous studies we have shown that a disulfide stabilized multimeric form of vitronectin is endocytosed and degraded by fibroblast cells (T.S. Panetti, P.J. McKeown-Longo, J. Biol. Chem. 268 (1993) 11988-11993; P.J. McKeown-Longo, T.S. Panetti, in: K.T. Preissner, S. Rosenblatt, C. Kost, J. Wegerhoff, D.F. Mosher (Eds.), Biology of Vitronectins and their Receptors, Elsevier Science Publishers, Amsterdam, 1993, pp. 111-118). The preparation of multimeric vitronectin used in these earlier studies was in the form of high molecular weight disulfide-bonded aggregates which were stable in sodium dodecyl sulfate (SDS). To address the question of whether vitronectin needed to be in the form of disulfide stabilized multimers in order to be endocytosed, a multimeric vitronectin, which was not disulfide stabilized, was prepared from vitronectin that had been treated with reducing agent and alkylated with iodoacetamide. The resulting protein migrated as a 65/75 kDa protein on SDS gels in the absence of reducing agent, confirming that this form of vitronectin was no longer stabilized into disulfide-bonded aggregates. However, the protein was still multimeric when analyzed by native gels and could be converted to SDS stable multimers by cross-linking agents. This result demonstrated that reduced and alkylated vitronectin aggregates into multimeric forms which are not stable in SDS. Similar to disulfide stabilized multimers, alkylated multimers of vitronectin bound to sulfated proteoglycans in the extracellular matrix and were endocytosed and degraded. Degradation of both forms of vitronectin was inhibited with arginine-glycine-aspartic acid peptides, an anti-alphavbeta5 antibody and heparin. Chloroquine and wortmannin were also able to inhibit degradation of both forms of vitronectin, indicating that both multimeric forms were following the same endocytic and degradative pathway. These results suggest that the organization of vitronectin into a multimeric form which will be recognized for endocytosis does not require disulfide bond stabilization. This study further suggests that recognition of vitronectin for endocytosis is dependent upon its conversion from a monomeric to a multivalent form (C.E. Wilkins-Port, P.J. McKeown-Longo, Mol. Biol. Cell 8:S:64A (1997).

Partial rescue of the Hyp phenotype by osteoblast-targeted PHEX (phosphate-regulating gene with homologies to endopeptidases on the X chromosome) expression.

Inactivating mutations and/or deletions of PHEX/Phex (phosphate-regulating gene with homologies to endopeptidases on the X chromosome) are responsible for X-linked hypophosphatemic rickets in humans and in the murine homolog Hyp. The predominant osteoblastic expression of Phex has implicated a primary metabolic osteoblast defect in the pathophysiology of this disorder. By targeting PHEX expression to osteoblasts in the Hyp genetic background, we aimed to correct the corresponding biochemical and morphological abnormalities and obtain information on their pathogenetic mechanism. When transgene Phex expression, driven by a mouse pro-alpha1(I) collagen gene promoter, was crossed into the Hyp background, it improved the defective mineralization of bone and teeth but failed to correct the hypophosphatemia and altered vitamin D metabolism associated with the disorder. Ex vivo bone marrow cultures confirmed the amelioration in the Hyp-associated matrix mineralization defect after Phex expression. These findings suggest that while the Hyp bone and teeth abnormalities partially correct after PHEX gene transfer, additional factors and/or sites of PHEX expression are likely critical for the elaboration of the appropriate molecular signals that alter renal phosphate handling and vitamin D metabolism in this disorder.

Distribution of connective tissue proteins during development and neovascularization of the epicardium.

OBJECTIVE: The epicardium is the site of initial cardiac neovascularization and formation of the coronary circulatory system. Recent evidence indicates that vascular progenitor cells are influenced by the connective tissue proteins of their extracellular environment, yet little is known about the composition or function of the embryonic epicardial extracellular matrix (ECM). This study examines the distribution of ECM proteins during the migration, growth and maturation of epicardial cells and also during the development of the coronary vascular network. METHODS: Immunofluorescence microscopy was used to determine the distributions of vitronectin, fibronectin and a newly described fibrillin-like protein, the JB3 antigen, in the embryonic chicken heart. Immunoblot analysis was performed to compare the relative electrophoretic mobilities of the JB3 antigen and fibrillin-1. RESULTS: The data show that vitronectin and fibronectin are present at sites of initial migration of the epicardial cells. The expression of vitronectin (and also fibronectin) becomes more pronounced as the epicardium thickens, undergoes remodeling and differentiates. The JB3 antigen is prominently expressed in the coronary arteries, allowing visualization of their connection to the systemic circulation and to the heart muscle, as well as vessel wall formation and organization. Immunoblot analysis suggests that the JB3 antibody recognizes a fibrillin-like polypeptide that is distinct from fibrillin-1. CONCLUSIONS: The observed distributions of vitronectin and fibronectin are consistent with roles in migration of epicardial cells, in remodeling of the epicardium and as substratum components during blood vessel formation. The observed distribution of the JB3 antigen indicates a structural/organizational role in coronary arterial wall assembly and suggests that the JB3 antibody be considered an early marker for maturing coronary arteries.