Binding of the NG2 proteoglycan to type VI collagen and other extracellular matrix molecules

Using extracellular matrix for regenerative medicine in the spinal cord

Regeneration within the mammalian central nervous system (CNS) is limited, and traumatic injury often leads to permanent functional motor and sensory loss. The lack of regeneration following spinal cord injury (SCI) is mainly caused by the presence of glial scarring, cystic cavitation and a hostile environment to axonal growth at the lesion site. The more prominent experimental treatment strategies focus mainly on drug and cell therapies, however recent interest in biomaterial-based strategies are increasing in number and breadth. Outside the spinal cord, approaches that utilize the extracellular matrix (ECM) to promote tissue repair show tremendous potential for various application including vascular, skin, bone, cartilage, liver, lung, heart and peripheral nerve tissue engineering (TE). Experimentally, it is unknown if these approaches can be successfully translated to the CNS, either alone or in combination with synthetic biomaterial scaffolds. In this review we outline the first attempts to apply the potential of ECM-based biomaterials and combining cell-derived ECM with synthetic scaffolds.

NG2/CSPG4-collagen type VI interplays putatively involved in the microenvironmental control of tumour engraftment and local expansion

In soft-tissue sarcoma patients, enhanced expression of NG2/CSPG4 proteoglycan in pre-surgical primary tumours predicts post-surgical metastasis formation and thereby stratifies patients into disease-free survivors and patients destined to succumb to the disease. Both primary and secondary sarcoma lesions also up-regulate collagen type VI, a putative extracellular matrix ligand of NG2, and this matrix alteration potentiates the prognostic impact of NG2. Enhanced constitutive levels of the proteoglycan in isolated sarcoma cells closely correlate with a superior engraftment capability and local growth in xenogenic settings. This apparent NG2-associated malignancy was also corroborated by the diverse tumorigenic behaviour in vitro and in vivo of immunoselected NG2-expressing and NG2-deficient cell subsets, by RNAi-mediated knock down of endogenous NG2, and by ectopic transduction of full-length or deletion constructs of NG2. Cells with modified expression of NG2 diverged in their interaction with purified Col VI, matrices supplemented with Col VI, and cell-free matrices isolated from wild-type and Col VI null fibroblasts. The combined use of dominant-negative NG2 mutant cells and purified domain fragments of the collagen allowed us to pinpoint the reciprocal binding sites within the two molecules and to assert the importance of this molecular interaction in the control of sarcoma cell adhesion and motility. The NG2-mediated binding to Col VI triggered activation of convergent cell survival- and cell adhesion/migration-promoting signal transduction pathways, implicating PI-3K as a common denominator. Thus, the findings point to an NG2-Col VI interplay as putatively involved in the regulation of the cancer cell-host microenvironment interactions sustaining sarcoma progression.

Novel frem1-related mouse phenotypes and evidence of genetic interactions with gata4 and slit3

The FRAS1-related extracellular matrix 1 (FREM1) gene encodes an extracellular matrix protein that plays a critical role in the development of multiple organ systems. In humans, recessive mutations in FREM1 cause eye defects, congenital diaphragmatic hernia, renal anomalies and anorectal malformations including anteriorly placed anus. A similar constellation of findings-microphthalmia, cryptophthalmos, congenital diaphragmatic hernia, renal agenesis and rectal prolapse-have been described in FREM1-deficient mice. In this paper, we identify a homozygous Frem1 missense mutation (c.1687A>T, p.Ile563Phe) in an N-ethyl-N-nitrosourea (ENU)-derived mouse strain, crf11, with microphthalmia, cryptophthalmos, renal agenesis and rectal prolapse. This mutation affects a highly conserved residue in FREM1's third CSPG domain. The p.Ile563Phe change is predicted to be deleterious and to cause decreased FREM1 protein stability. The crf11 allele also fails to complement the previously described eyes2 allele of Frem1 (p.Lys826*) providing further evidence that the crf11 phenotype is due to changes affecting Frem1 function. We then use mice bearing the crf11 and eyes2 alleles to identify lung lobulation defects and decreased anogenital distance in males as novel phenotypes associated with FREM1 deficiency in mice. Due to phenotypic overlaps between FREM1-deficient mice and mice that are deficient for the retinoic acid-responsive transcription factor GATA4 and the extracellular matrix protein SLIT3, we also perform experiments to look for in vivo genetic interactions between the genes that encode these proteins. These experiments reveal that Frem1 interacts genetically with Gata4 in the development of lung lobulation defects and with Slit3 in the development of renal agenesis. These results demonstrate that FREM1-deficient mice faithfully recapitulate many of the phenotypes seen in individuals with FREM1 deficiency and that variations in GATA4 and SLIT3 expression modulate some FREM1-related phenotypes in mice.

Proteoglycans and their roles in brain cancer

Glioblastoma, a malignant brain cancer, is characterized by abnormal activation of receptor tyrosine kinase signalling pathways and a poor prognosis. Extracellular proteoglycans, including heparan sulfate and chondroitin sulfate, play critical roles in the regulation of cell signalling and migration via interactions with extracellular ligands, growth factor receptors and extracellular matrix components, as well as intracellular enzymes and structural proteins. In cancer, proteoglycans help drive multiple oncogenic pathways in tumour cells and promote critical tumour-microenvironment interactions. In the present review, we summarize the evidence for proteoglycan function in gliomagenesis and examine the expression of proteoglycans and their modifying enzymes in human glioblastoma using data obtained from The Cancer Genome Atlas (http://cancergenome.nih.gov/). Furthermore, we demonstrate an association between specific proteoglycan alterations and changes in receptor tyrosine kinases. Based on these data, we propose a model in which proteoglycans and their modifying enzymes promote receptor tyrosine kinase signalling and progression in glioblastoma, and we suggest that cancer-associated proteoglycans are promising biomarkers for disease and therapeutic targets.

WARP interacts with collagen VI-containing microfibrils in the pericellular matrix of human chondrocytes

Collagen VI and WARP are extracellular structural macromolecules present in cartilage and associated with BM suprastructures in non-skeletal tissues. We have previously shown that in WARP-deficient mice, collagen VI is specifically reduced in regions of the peripheral nerve ECM where WARP is expressed, suggesting that both macromolecules are part of the same suprastructure. The object of this study was to conduct a detailed analysis of WARP-collagen VI interactions in vitro in cartilage, a tissue rich in WARP and collagen VI. Immunohistochemical analysis of mouse and human articular cartilage showed that WARP and collagen VI co-localize in the pericellular matrix of superficial zone articular chondrocytes. EM analysis on extracts of human articular cartilage showed that WARP associates closely with collagen VI-containing suprastructures. Additional evidence of an interaction is provided by immunogold EM and immunoblot analysis showing that WARP was present in collagen VI-containing networks isolated from cartilage. Further characterization were done by solid phase binding studies and reconstitution experiments using purified recombinant WARP and isolated collagen VI. Collagen VI binds to WARP with an apparent K(d) of approximately 22 nM and the binding site(s) for WARP resides within the triple helical domain since WARP binds to both intact collagen VI tetramers and pepsinized collagen VI. Together, these data confirm and extend our previous findings by demonstrating that WARP and collagen VI form high affinity associations in vivo in cartilage. We conclude that WARP is ideally placed to function as an adapter protein in the cartilage pericellular matrix.

CSPG4 as a target of antibody-based immunotherapy for malignant mesothelioma

PURPOSE

Malignant mesothelioma (MM) is an aggressive cancer, resistant to current therapies. Membrane chondroitin sulphate proteoglycan 4 (CSPG4), which has been successfully targeted in melanoma and breast cancer, was found highly expressed in MM, but not in normal mesothelium. Therefore, we explored CSPG4 as a suitable target for monoclonal antibody (mAb)-based immunotherapy for MM.

EXPERIMENTAL DESIGN

We assayed adhesion, motility, invasiveness, wound-healing, apoptosis, and anchorage-independent growth of MM cells on cell cultures. CSPG4 expression and signaling was studied by immunoblotting. The growth of MM severe combined immunodeficient (SCID) mice xenografts induced by PPM-Mill cells, engineered to express the luciferase reporter gene, was monitored by imaging, upon treatment with CSPG4 mAb TP41.2. Animal toxicity and survival were assayed in both tumor inhibition and therapeutic experiments.

RESULTS

CSPG4 was expressed on 6 out of 8 MM cell lines and in 25 out of 41 MM biopsies, with minimal expression in surrounding healthy cells. MM cell adhesion was mediated by CSPG4-dependent engagement of ECM. Cell adhesion was inhibited by mAb TP41.2 resulting in decreased phosphorylation of focal adhesion kinase (FAK) and AKT, reduced expression of cyclin D1 and apoptosis. Moreover, mAb TP41.2 significantly reduced MM cell motility, migration, and invasiveness, and inhibited MM growth in soft agar. In vivo, treatment with mAb TP41.2 prevented or inhibited the growth of MM xenografts in SCID mice, with a significant increase in animal survival.

CONCLUSION

These results establish the safety of CSPG4 mAb-based immunotherapy and suggest that CSPG4 mAb-based immunotherapy may represent a novel approach for the treatment of MM.

NG2-mediated Rho activation promotes amoeboid invasiveness of cancer cells

The aim of this study was to analyze the potential role of NG2 chondroitin sulfate proteoglycan in amoeboid morphology and invasiveness of cancer cells. In the highly metastatic amoeboid cell lines A3 and A375M2, siRNA-mediated down-regulation of NG2 induced an amoeboid-mesenchymal transition associated with decreased invasiveness in 3D collagen and inactivation of the GTPase Rho. Conversely, the expression of NG2 in mesenchymal sarcoma K2 cells as well as in A375M2 cells resulted in an enhanced amoeboid phenotype associated with increased invasiveness and elevated Rho-GTP levels. Remarkably, the amoeboid-mesenchymal transition in A375M2 cells triggered by NG2 down-regulation was associated with increased extracellular matrix-degrading ability, although this was not sufficient to compensate for the decreased invasive capability caused by down-regulated Rho/ROCK signaling. Conversely, in K2 cells with overexpression of NG2, the ability to degrade the extracellular matrix was greatly reduced. Taken together, we suggest that NG2-mediated activation of Rho leading to effective amoeboid invasiveness is a possible mechanism through which NG2 could contribute to tumor cell invasion and metastasis.

Roles of NG2 glial cells in diseases of the central nervous system

NG2 cells are a novel distinct class of central nervous system (CNS) glial cells, characterized by the expression of the chondroitin sulfate proteoglycan NG2. They have been detected in a variety of human CNS diseases. As morphological, physiological and biomolecular studies of NG2 cells have been conducted, their roles have been gradually revealed. Research on cellular and molecular mechanisms in the pathophysiological state was built on the preliminary findings of their physiological functions; and in turn, this helps to clarify their physiological roles and leads to the identification of novel therapeutic targets. This review summarizes recent findings regarding the potential roles of NG2 cells in traumatic brain injury, multiple sclerosis, glioma, epilepsy, Alzheimer's disease and electroconvulsive therapy for depression.

Antithetic roles of proteoglycans in cancer

Proteoglycans (PGs), a family of complex post-translationally sculptured macromolecules, are fundamental regulators of most normal and aberrant cellular functions. The unparalleled structural-functional diversity of PGs endows them with the ability to serve as critical mediators of the tumor cells' interaction with the host microenvironment, while directly contributing to the organization and dynamic remodeling of this milieu. Despite their indisputable importance during embryonic development and in the adult organism, and their frequent dysregulation in tumor lesions, their precise involvement in tumorigenesis awaits a more decisive demonstration. Particularly challenging is to ascertain to what extent selected PGs may catalyze tumor progression and to what extent they may inhibit it, implying antithetic functions of individual PGs. Integrated efforts are needed to consolidate the routine use of PGs in the clinical monitoring of cancer patients and to broaden the exploitation of these macromolecules as therapeutic targets. Several PGs have the required attributes to be contemplated as effective antigens for immunotherapeutic approaches, while the tangible results obtained in recent clinical trials targeting the NG2/CSPG4 transmembrane PG urge further development of PG-based cancer treatment modalities.

The role of LamininB2 (LanB2) during mesoderm differentiation in Drosophila

In Drosophila, four genes encode for laminin subunits and the formation of two laminin heterotrimers has been postulated. We report the identification of mutations in the Drosophila LamininB2 (LanB2) gene that encodes for the only laminin γ subunit and is found in both heterotrimers. We describe their effects on embryogenesis, in particular the differentiation of visceral tissues with respect to the ECM. Analysis of mesoderm endoderm interaction indicates disrupted basement membranes and defective endoderm migration, which finally interferes with visceral myotube stretching. Extracellular deposition of laminin is blocked due to the loss of the LanB2 subunit, resulting in an abnormal distribution of ECM components. Our data, concerning the different function of both trimers during organogenesis, suggest that these trimers might act in a cumulative way and probably at multiple steps during ECM assembly. We also observed genetic interactions with kon-tiki and thrombospondin, indicating a role for laminin during muscle attachment.

Type VI collagen deficiency induces osteopenia with distortion of osteoblastic cell morphology

Bone consists of type I collagen as a major protein with minor various matrix proteins. Type VI collagen is one of bone matrix proteins but its function is not known. We therefore examined the effects of type VI collagen deficiency on bone. 3D-μCT analysis revealed that type VI collagen deficiency reduced cancellous bone mass. Cortical bone mass was not affected. Type VI collagen deficiency distorted the shape of osteoblasts both in the cancellous bone and in the cambium layer of periosteal region. Furthermore, type VI collagen deficiency disorganized collagen arrangement. These data indicate that type VI collagen contributes to maintain bone mass.

ColVI myopathies: where do we stand, where do we go?

Collagen VI myopathies, caused by mutations in the genes encoding collagen type VI (ColVI), represent a clinical continuum with Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy (BM) at each end of the spectrum, and less well-defined intermediate phenotypes in between. ColVI myopathies also share common features with other disorders associated with prominent muscle contractures, making differential diagnosis difficult. This group of disorders, under-recognized for a long time, has aroused much interest over the past decade, with important advances made in understanding its molecular pathogenesis. Indeed, numerous mutations have now been reported in the COL6A1, COL6A2 and COL6A3 genes, a large proportion of which are de novo and exert dominant-negative effects. Genotype-phenotype correlations have also started to emerge, which reflect the various pathogenic mechanisms at play in these disorders: dominant de novo exon splicing that enables the synthesis and secretion of mutant tetramers and homozygous nonsense mutations that lead to premature termination of translation and complete loss of function are associated with early-onset, severe phenotypes. In this review, we present the current state of diagnosis and research in the field of ColVI myopathies. The past decade has provided significant advances, with the identification of altered cellular functions in animal models of ColVI myopathies and in patient samples. In particular, mitochondrial dysfunction and a defect in the autophagic clearance system of skeletal muscle have recently been reported, thereby opening potential therapeutic avenues.

The collagen VI-related myopathies: muscle meets its matrix

The collagen VI-related myopathy known as Ullrich congenital muscular dystrophy is an early-onset disease that combines substantial muscle weakness with striking joint laxity and progressive contractures. Patients might learn to walk in early childhood; however, this ability is subsequently lost, concomitant with the development of frequent nocturnal respiratory failure. Patients with intermediate phenotypes of collagen VI-related myopathy display a lesser degree of weakness and a longer period of ambulation than do individuals with Ullrich congenital muscular dystrophy, and the spectrum of disease finally encompasses mild Bethlem myopathy, in which ambulation persists into adulthood. Dominant and recessive autosomal mutations in the three major collagen VI genes-COL6A1, COL6A2, and COL6A3-can underlie this entire clinical spectrum, and result in deficient or dysfunctional microfibrillar collagen VI in the extracellular matrix of muscle and other connective tissues, such as skin and tendons. The potential effects on muscle include progressive dystrophic changes, fibrosis and evidence for increased apoptosis, which potentially open avenues for pharmacological intervention. Optimized respiratory management, including noninvasive nocturnal ventilation together with careful orthopedic management, are the current mainstays of treatment and have already led to a considerable improvement in life expectancy for children with Ullrich congenital muscular dystrophy.

Functional and clinical relevance of chondroitin sulfate proteoglycan 4

The lack of effective conventional therapies for the treatment of advanced stage melanoma has stimulated interest in the development of novel strategies for the management of patients with malignant melanoma. Among them, immunotherapy has attracted much attention because of the potential role played by immunological events in the clinical course of melanoma. For many years, T cell-based immunotherapy has been emphasized in part because of the disappointing results of the monoclonal antibody (mAb)-based clinical trials conducted in the early 1980s and in part because of the postulated major role played by T cells in tumor growth control. More recently, mAb-based therapies have gained in popularity given their clinical and commercial success for a variety of malignant diseases. As a result, there has been increased interest in identifying and characterizing antibody-defined melanoma antigens. Among them, the chondroitin sulfate proteoglycan 4 (CSPG4), also known as high molecular weight-melanoma associated antigen (HMW-MAA) or melanoma chondroitin sulfate proteoglycan (MCSP), has attracted much attention in recent years because of the growing experimental evidence that it fulfills two requirements for immunotherapy to be therapeutically effective: (1) targeting of cancer stem cells (CSC) and (2) development of combinatorial therapies to counteract the escape mechanisms driven by the genetic instability of tumor cells. With this in mind, in this chapter, we have reviewed recent information related to the distribution of CSPG4 on various types of tumors, including CSC, its expression on pericytes in the tumor microenvironment, its recognition by T cells, its role in cell biology as well as the potential mechanisms underlying the ability of CSPG4-specific immunity to control malignant cell growth.

The collagen VI-related myopathies Ullrich congenital muscular dystrophy and Bethlem myopathy

Mutations in the genes COL6A1, COL6A2, and COL6A3, coding for three α chains of collagen type VI, underlie a spectrum of myopathies, ranging from the severe congenital muscular dystrophy-type Ullrich (UCMD) to the milder Bethlem myopathy (BM), with disease manifestations of intermediate severity in between. UCMD is characterized by early-onset weakness, associated with pronounced distal joint hyperlaxity and the early onset or early progression of more proximal contractures. In the most severe cases ambulation is not achieved, or it may be achieved only for a limited period of time. BM may be of early or later onset, but is milder in its manifestations, typically allowing for ambulation well into adulthood, whereas typical joint contractures are frequently prominent. A genetic spectrum is emerging, with BM being caused mostly by dominantly acting mutations, although rarely recessive inheritance of BM is also possible, whereas both dominantly as well as recessively acting mutations underlie UCMD.

Identification of cell surface glycoprotein markers for glioblastoma-derived stem-like cells using a lectin microarray and LC-MS/MS approach

Despite progress in the treatment of glioblastoma, more than 95% of patients suffering from this disease still die within 2 years. Recent findings support the belief that cancer stem-like cells are responsible for tumor formation and ongoing growth. Here a method combining lectin microarray and LC-MS/MS was used to discover the cell surface glycoprotein markers of a glioblastoma-derived stem-like cell line. Lectin microarray analysis of cell surface glycans showed that two galactose-specific lectins Trichosanthes kirilowii agglutinin (TKA) and Peanut agglutinin (PNA) could distinguish the stem-like glioblastoma neurosphere culture from a traditional adherent glioblastoma cell line. Agarose-bound TKA and PNA were used to capture the glycoproteins from the two cell cultures, which were analyzed by LC-MS/MS. The glycoproteins were quantified by spectral counting, resulting in the identification of 12 and 11 potential glycoprotein markers from the TKA and PNA captured fractions respectively. Almost all of these proteins were membrane proteins. Differential expression was verified by Western blotting analysis of 6 interesting proteins, including the up-regulated Receptor-type tyrosine-protein phosphatase zeta, Tenascin-C, Chondroitin sulfate proteoglycan NG2, Podocalyxin-like protein 1 and CD90, and the down-regulated CD44. An improved understanding of these proteins may be important for earlier diagnosis and better therapeutic targeting of glioblastoma.

Pericyte deficiencies lead to aberrant tumor vascularizaton in the brain of the NG2 null mouse

Tightly regulated crosstalk between endothelial cells and pericytes is required for formation and maintenance of functional blood vessels. When the NG2 proteoglycan is absent from pericyte surfaces, vascularization of syngeneic tumors growing in the C57Bl/6 mouse brain is aberrant in several respects, resulting in retardation of tumor progression. In the NG2 null mouse brain, pericyte investment of the tumor vascular endothelium is reduced, causing deficiencies in both pericyte and endothelial cell maturation, as well as reduced basal lamina assembly. While part of this deficit may be due to the previously-identified role of NG2 in beta1 integrin-dependent periyte/endothelial cell crosstalk, the ablation of NG2 also appears responsible for loss of collagen VI anchorage, in turn leading to reduced collagen IV deposition. Poor functionality of tumor vessels in NG2 null brain is reflected by reduced vessel patency and increased vessel leakiness, resulting in large increases in tumor hypoxia. These findings demonstrate the importance of NG2-dependent pericyte/endothelial cell interaction in the development and maturation of tumor blood vessels, identifying NG2 as a potential target for anti-angiogenic cancer therapy.

Advanced osteoarthritis in humans is associated with altered collagen VI expression and upregulation of ER-stress markers Grp78 and bag-1

To test the hypothesis that a perturbation of endoplasmic reticulum (ER) function is involved in the pathogenesis of osteoarthritis (OA), articular cartilage was isolated from non-OA patients secondary to resection of osteo- or chondrosarcomas. Intra-joint samples of minimal and advanced osteoarthritic cartilage were isolated from patients undergoing total knee arthroplasty and scored for disease severity. Glucose-regulated protein-78 (grp78) and bcl-2-associated athanogene-1 (bag-1) were detected via immunofluorescence as markers of non-homeostatic ER function. Additionally, the expression of type VI collagen and its integrin receptor, NG2, was determined to examine cartilage matrix health and turnover. There was an upregulation of grp78 in advanced OA, and variable expression in minimal OA. Non-OA cartilage was consistently grp78 negative. The downstream regulator bag-1 was also upregulated in OA compared with normal cartilage. Collagen VI was mainly cell-associated in non-OA cartilage, with a more widespread distribution observed in OA cartilage along with increased intracellular staining intensity. The collagen VI integral membrane proteoglycan receptor NG2 was downregulated in advanced OA compared with its patient-matched minimally involved cartilage sample. These results suggest that chondrocytes exhibit ER stress during OA, in association with upregulation of a large secreted molecule, type VI collagen.

Developmental and osteoarthritic changes in Col6a1-knockout mice: biomechanics of type VI collagen in the cartilage pericellular matrix

OBJECTIVE

Chondrocytes, the sole cell type in articular cartilage, maintain the extracellular matrix (ECM) through a homeostatic balance of anabolic and catabolic activities that are influenced by genetic factors, soluble mediators, and biophysical factors such as mechanical stress. Chondrocytes are encapsulated by a narrow tissue region termed the "pericellular matrix" (PCM), which in normal cartilage is defined by the exclusive presence of type VI collagen. Because the PCM completely surrounds each cell, it has been hypothesized that it serves as a filter or transducer for biochemical and/or biomechanical signals from the cartilage ECM. The present study was undertaken to investigate whether lack of type VI collagen may affect the development and biomechanical function of the PCM and alter the mechanical environment of chondrocytes during joint loading.

METHODS

Col6a1(-/-) mice, which lack type VI collagen in their organs, were generated for use in these studies. At ages 1, 3, 6, and 11 months, bone mineral density (BMD) was measured, and osteoarthritic (OA) and developmental changes in the femoral head were evaluated histomorphometrically. Mechanical properties of articular cartilage from the hip joints of 1-month-old Col6a1(-/-), Col6a1(+/-), and Col6a1(+/+) mice were assessed using an electromechanical test system, and mechanical properties of the PCM were measured using the micropipette aspiration technique.

RESULTS

In Col6a1(-/-) and Col6a1(+/-) mice the PCM was structurally intact, but exhibited significantly reduced mechanical properties as compared with wild-type controls. With age, Col6a1(-/-) mice showed accelerated development of OA joint degeneration, as well as other musculoskeletal abnormalities such as delayed secondary ossification and reduced BMD.

CONCLUSION

These findings suggest that type VI collagen has an important role in regulating the physiology of the synovial joint and provide indirect evidence that alterations in the mechanical environment of chondrocytes, due to either loss of PCM properties or Col6a1(-/-)-derived joint laxity, can lead to progression of OA.

Exon skipping mutations in collagen VI are common and are predictive for severity and inheritance

Mutations in the genes encoding collagen VI (COL6A1, COL6A2, and COL6A3) cause Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD), two related conditions of differing severity. BM is a relatively mild dominantly inherited disorder characterized by proximal weakness and distal joint contractures. UCMD was originally regarded as an exclusively autosomal recessive condition causing severe muscle weakness with proximal joint contractures and distal hyperlaxity. We and others have subsequently modified this model when we described UCMD patients with heterozygous in-frame deletions acting in a dominant-negative way. Here we report 10 unrelated patients with a UCMD clinical phenotype and de novo dominant negative heterozygous splice mutations in COL6A1, COL6A2, and COL6A3 and contrast our findings with four UCMD patients with recessively acting splice mutations and two BM patients with heterozygous splice mutations. We find that the location of the skipped exon relative to the molecular structure of the collagen chain strongly correlates with the clinical phenotype. Analysis by immunohistochemical staining of muscle biopsies and dermal fibroblast cultures, as well as immunoprecipitation to study protein biosynthesis and assembly, suggests different mechanisms each for exon skipping mutations underlying dominant UCMD, dominant BM, and recessive UCMD. We provide further evidence that de novo dominant mutations in severe UCMD occur relatively frequently in all three collagen VI chains and offer biochemical insight into genotype-phenotype correlations within the collagen VI-related disorders by showing that severity of the phenotype depends on the ability of mutant chains to be incorporated in the multimeric structure of collagen VI.

A role for the NG2 proteoglycan in glioma progression

Many human gliomas carry markers characteristic of oligodendrocyte progenitor cells (such as Olig-2, PDGF alpha receptor and NG2 proteoglycan), suggesting these progenitors as the cells of origin for glioma initiation. This review considers the potential roles of the NG2 proteoglycan in glioma progression. NG2 is expressed not only by glioma cells and by oligodendrocyte progenitors, but also by pericytes associated with the tumor microvasculature. The proteoglycan may therefore promote tumor vascularization and recruitment of normal progenitors to the tumor mass, in addition to mediating expansion of the transformed cell population. Along with potentiating growth factor signaling and serving as a cell surface receptor for extracellular matrix components, NG2 also has the ability to mediate activation of beta-1 integrins. These molecular interactions allow the proteoglycan to contribute to critical processes such as cell proliferation, cell motility and cell survival.

Proteome analysis of matrix vesicles isolated from femurs of chicken embryo

Matrix vesicles (MVs) are extracellular organelles that initiate mineral formation, accumulating inorganic phosphate (P(i)) and calcium leading to the formation of hydroxyapatite (HA) crystals, the main mineral component of bones. MVs are produced during bone formation, as well as during the endochondral calcification of cartilage. MVs are released into the extracellular matrix from osseous cells such as osteoblasts and hypertrophic chondrocytes. In this report, using 1-D SDS-PAGE, in-gel tryptic digestion and an LC-MS-MS/MS protein identification protocol, we characterized the proteome of MVs isolated from chicken embryo (Gallus gallus) bones and cartilage. We identified 126 gene products, including proteins related to the extracellular matrix and ion transport, as well as enzymes, cytoskeletal, and regulatory proteins. Among the proteins recognized for the first time in MVs were aquaporin 1, annexin A1 (AnxA1), AnxA11, glycoprotein HT7, G(i) protein alpha2, and scavenger receptor type B. The pathways for targeting the identified proteins into MVs and their particular functions in the biomineralization process are discussed. Obtaining a knowledge of the functions and roles of these proteins during embryonic mineralization is a prerequisite for the overall understanding of the initial mineral formation mechanisms.

Adult bone marrow-derived mononuclear cells expressing chondroitinase AC transplanted into CNS injury sites promote local brain chondroitin sulphate degradation

Injury to the CNS of vertebrates leads to the formation of a glial scar and production of inhibitory molecules, including chondroitin sulphate proteoglycans. Various studies suggest that the sugar component of the proteoglycan is responsible for the inhibitory role of these compounds in axonal regeneration. By degrading chondroitin sulphate chains with specific enzymes, denominated chondroitinases, the inhibitory capacity of these proteoglycans is decreased. Chondroitinase administration involves frequent injections of the enzyme at the lesion site which constitutes a rather invasive method. We have produced a vector containing the gene for Flavobacterium heparinum chondroitinase AC for expression in adult bone marrow-derived cells which were then transplanted into an injury site in the CNS. The expression and secretion of active chondroitinase AC was observed in vitro using transfected Chinese hamster ovarian and gliosarcoma cells and in vivo by immunohistochemistry analysis which showed degraded chondroitin sulphate coinciding with the location of transfected bone marrow-derived cells. Immunolabelling of the axonal growth-associated protein GAP-43 was observed in vivo and coincided with the location of degraded chondroitin sulphate. We propose that bone marrow-derived mononuclear cells, transfected with our construct and transplanted into CNS, could be a potential tool for studying an alternative chondroitinase AC delivery method.

NG2 proteoglycan increases mesangial cell proliferation and extracellular matrix production

As a membrane-spanning protein, NG2 chondroitin sulfate proteoglycan interacts with molecules on both sides of plasma membrane. The present study explored the role of NG2 in the pathogenesis of diabetic nephropathy. In the normal kidneys, NG2 was observed predominantly in glomerular mesangium, Bowman's capsule and interstitial vessels. Both mRNA and protein expression in kidneys was significantly higher in strepozotocin-induced diabetic rats than that in normal rats. In the cultured rat mesangial cell line HBZY-1, overexpression of NG2 promoted mesangial cell proliferation and extracellular matrix (ECM) production, such as type VI collagen and laminin. Furthermore, target knockdown of NG2 resulted in decreased cell proliferation and ECM formation. The observations suggest that NG2 is up-regulated in diabetic nephropathy. It actively participates in the development and progression of glomerulosclerosis by stimulating proliferation of mesangial cells and deposition of ECM.

Differential phosphorylation of NG2 proteoglycan by ERK and PKCalpha helps balance cell proliferation and migration

Two distinct Thr phosphorylation events within the cytoplasmic domain of the NG2 proteoglycan help regulate the cellular balance between proliferation and motility. Protein kinase Calpha mediates the phosphorylation of NG2 at Thr2256, resulting in enhanced cell motility. Extracellular signal-regulated kinase phosphorylates NG2 at Thr2314, stimulating cell proliferation. The effects of NG2 phosphorylation on proliferation and motility are dependent on beta1-integrin activation. Differential cell surface localization of the two distinctly phosphorylated forms of NG2 may be the mechanism by which the NG2-beta1-integrin interaction promotes proliferation in one case and motility in the other. NG2 phosphorylated at Thr2314 colocalizes with beta1-integrin on microprotrusions from the apical cell surface. In contrast, NG2 phosphorylated at Thr2256 colocalizes with beta1-integrin on lamellipodia at the leading edges of cells. Thus, phosphorylation and the resulting site of NG2-integrin localization may determine the specific downstream effects of integrin signaling.

Ultrastructural localization of Fras1 in the sublamina densa of embryonic epithelial basement membranes

Fras1 is the first identified member of a protein family comprising Fras1 and the related extracellular matrix proteins Frem1, Frem2 and Frem3. Mutations in Fras1, Frem1 and Frem2 have been associated with the bleb phenotype in mouse, whereas mutations in the human orthologs FRAS1 and FREM2 have been implicated in the pathogenesis of the human Fraser syndrome. Bleb mutant mice are characterized by embryonic sub-epidermal blistering, unilateral or bilateral renal agenesis or dysgenesis, cutaneous syndactyly and fused eyelids. As revealed by immunofluorescence, Fras1 co-localizes with the markers of epithelial basement membranes and is ultrastructurally detected underneath the lamina densa of embryonic mouse epithelia. Since the loss of Fras1 mainly affects the cohesiveness of the embryonic skin basement membrane with its underlying mesenchyme, we compared here the ultrastructural localization of Fras1 in the dermal-epidermal junction and in the basement membrane of other embryonic epithelia that do not show any overt phenotype using preembedding immunocytochemistry. Fras1 immunoreactivity was detected in all epithelia examined, within the sublamina densa adjacent to stromal tissue, as clustered gold/silver enhanced depositions, usually attached to anchoring fibrils. Interestingly, clusters corresponding to Fras1 were frequently detected in close proximity to mesenchymal cells, indicating that Fras1 could serve as a direct link between the sublamina densa and mesenchyme. The localization of Fras1 is consistent with previous results indicating that Fras1 exerts its function below the lamina densa and that Fras1 displays the same localization pattern in all epithelial basement membranes.

The transmembrane protein Kon-tiki couples to Dgrip to mediate myotube targeting in Drosophila

Directed cell migration and target recognition are critical for the development of both the nervous and muscular systems. Molecular mechanisms that control these processes in the nervous system have been intensively studied, whereas those that act during muscle development are still largely uncharacterized. Here we identify a transmembrane protein, Kon-tiki (Kon), that mediates myotube target recognition in the Drosophila embryo. Kon is expressed in a specific subset of myotubes and is required autonomously for these myotubes to recognize their tendon cell targets and to establish a stable connection. Kon is enriched at myotube tips during targeting and signals through the intracellular adaptor Dgrip in a conserved molecular pathway. Forced overexpression of Kon stimulates muscle motility. We propose that Kon promotes directed myotube migration and transduces a target-derived signal that initiates the formation of a stable connection.

The expression of NG2 proteoglycan in the human intervertebral disc

STUDY DESIGN

Immunohistochemical and biochemical analyses of NG2 proteoglycan in the human intervertebral disc.

OBJECTIVE

To determine if the human intervertebral disc expresses NG2 proteoglycan.

SUMMARY OF BACKGROUND DATA

In the nervous system, NG2 has been reported to play an important role as an interactive extracellular matrix component and membrane receptor for growth factors. NG2 is also found in non-neuronal tissues, such as cartilage and bone; however, the expression of NG2 within the human intervertebral disc is unknown.

METHODS

NG2 expression in the intervertebral disc was examined through Western blotting, reverse transcriptase polymerase chain reaction, and immunohistochemistry. Confocal microscopy was used to assess the spatial association of NG2 with type VI collagen. To reveal changes in the content of NG2 with disc degeneration, Western blot analysis was used to assess the relative content of NG2 in human intervertebral disc tissues with varying degrees of degeneration.

RESULTS

NG2 was clearly identified in cells from both the anulus fibrosus and nucleus pulposus, and colocalized with both type VI collagen and beta-integrin, located in the inner area of the cell-associated matrix. Throughout the anterior and posterior regions of the disc tissues, most cells were confirmed to be NG2 positive. Cells expressed NG2 messenger ribonucleic acid, and Western blot confirmed the presence of the core protein of the NG2 protein, 250 kDa. A study comparing the different grades of disc degeneration showed that the content of NG2 was elevated in disc tissues in an advanced stage of degeneration compared to tissues in an early stage of degeneration.

CONCLUSIONS

Although the biologic role of NG2 remains to be elucidated, the colocalization of NG2 with type VI collagen in the pericellular area suggests that NG2 may play an important role in cell-matrix interactions. The high level of NG2 expression in advanced degeneration also suggests an important role of NG2 in the loss of disc integrity.

Matrix metalloproteinases and proteoglycans in axonal regeneration

After an injury to the adult mammalian central nervous system (CNS), a variety of growth-inhibitory molecules are upregulated. A glial scar forms at the site of injury and is composed of numerous molecular substances, including chondroitin sulfate proteoglycans (CSPGs). These proteoglycans inhibit axonal growth in vitro and in vivo. Matrix metalloproteinases (MMPs) can degrade the core protein of some CSPGs as well as other growth-inhibitory molecules such as Nogo and tenascin-C. MMPs have been shown to facilitate axonal regeneration in the adult mammalian peripheral nervous system (PNS). This review will focus on the various roles of proteoglycans and MMPs within the injured nervous system. First, we will present a general background on the injured central nervous system and explore the roles that proteoglycans play in the injured PNS and CNS. Second, we will discuss the various functions of MMPs within the injured PNS and CNS. Special attention will be paid to the possibility of how MMPs might modify the growth-inhibitory extracellular environment of the injured adult mammalian spinal cord and facilitate axonal regeneration in the CNS.

NG2 and Olig2 expression provides evidence for phenotypic deregulation of cultured central nervous system and peripheral nervous system neural precursor cells

Neural stem cells cultured with fibroblast growth factor 2 (FGF2)/epidermal growth factor (EGF) generate clonal expansions called neurospheres (NS), which are widely used for therapy in animal models. However, their cellular composition is still poorly defined. Here, we report that NS derived from several embryonic and adult central nervous system (CNS) regions are composed mainly of remarkable cells coexpressing radial glia markers (BLBP, RC2, GLAST), oligodendrogenic/neurogenic factors (Mash1, Olig2, Nkx2.2), and markers that in vivo are typical of the oligodendrocyte lineage (NG2, A2B5, PDGFR-alpha). On NS differentiation, the latter remain mostly expressed in neurons, together with Olig2 and Mash1. Using cytometry, we show that in growing NS the small population of multipotential self-renewing NS-forming cells are A2B5(+) and NG2(+). Additionally, we demonstrate that these NS-forming cells in the embryonic spinal cord were initially NG2(-) and rapidly acquired NG2 in vitro. NG2 and Olig2 were found to be rapidly induced by cell culture conditions in spinal cord neural precursor cells. Olig2 expression was also induced in astrocytes and embryonic peripheral nervous system (PNS) cells in culture after EGF/FGF treatment. These data provide new evidence for profound phenotypic modifications in CNS and PNS neural precursor cells induced by culture conditions.

Extracellular regulators of axonal growth in the adult central nervous system

Robust axonal growth is required during development to establish neuronal connectivity. However, stable fibre patterns are necessary to maintain adult mammalian central nervous system (CNS) function. After adult CNS injury, factors that maintain axonal stability limit the recovery of function. Extracellular molecules play an important role in preserving the stability of the adult CNS axons and in restricting recovery from pathological damage. Adult axonal growth inhibitors include a group of proteins on the oligodendrocyte, Nogo-A, myelin-associated glycoprotein, oligodendrocyte-myelin glycoprotein and ephrin-B3, which interact with axonal receptors, such as NgR1 and EphA4. Extracellular proteoglycans containing chondroitin sulphates also inhibit axonal sprouting in the adult CNS, particularly at the sites of astroglial scar formation. Therapeutic perturbations of these extracellular axonal growth inhibitors and their receptors or signalling mechanisms provide a degree of axonal sprouting and regeneration in the adult CNS. After CNS injury, such interventions support a partial return of neurological function.

Approaching theProteoglycome: Molecular Interactions of Proteoglycans and Their Functional Output

[Image: see text] Through their diverse core protein modules and glycan/glycosaminoglycan moieties, proteoglycans may engage in numerous cellular and molecular interactions which are dispensable during embryogenesis, are essential for the maintenance of a healthy state and are prone to modulation in pathological conditions. Proteoglycan interactions may involve binding to other structural components of the ECM, to cell surface receptors, to membrane-associated components, and to soluble signaling molecules, which through this interaction may become entrapped in the ECM or sequestered at the cell surface. Understanding of these multiple interplays is therefore of paramount importance and requires a detailed mapping through what we define as the proteoglycome.

Targeting pericytes diminishes neovascularization in orthotopic uveal melanoma in nerve/glial antigen 2 proteoglycan knockout mouse

In this investigation, we explored whether knockout of nerve/glial antigen 2 (NG2), a pericyte component, inhibited neovascularization and growth of uveal melanoma xenografts. For this, we used multichannel laser scanning confocal microscopy and quantitative image analysis. Orthotopic human uveal melanoma (OCM-1A) xenografts were induced in NG2 knockout and wild-type mice, which were immunosuppressed with cyclosporin A. Inhibition of pericytes through NG2 proteoglycan decreased neovascularization and tumor end volume, rendering pericytes and NG2 proteoglycan potential cellular and molecular therapeutic targets in uveal melanoma.

Collagen VI related muscle disorders

Mutations in the genes encoding collagen VI (COL6A1, COL6A2, and COL6A3) cause Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD), two conditions which were previously believed to be completely separate entities. BM is a relatively mild dominantly inherited disorder characterised by proximal weakness and distal joint contractures. UCMD was originally described as an autosomal recessive condition causing severe muscle weakness with proximal joint contractures and distal hyperlaxity. Here we review the clinical phenotypes of BM and UCMD and their diagnosis and management, and provide an overview of the current knowledge of the pathogenesis of collagen VI related disorders.

Collagen matrix in spinal cord injury

The fibrous scar that develops after central nervous system (CNS) injury is considered a major impediment for axonal regeneration. It consists of a dense collagen IV meshwork, which serves as a binding matrix for numerous other extracellular matrix components and inhibitory molecules like proteoglycans and semaphorins, but also growth-promoting factors. Inhibition of collagen matrix formation in brain and spinal cord lesions leads to axonal regeneration and functional recovery, although collagen IV per se is not inhibitory for axonal outgrowth. This review focuses on the molecular properties of the collagen IV matrix and its interactions with various molecules that are expressed after CNS lesion. Moreover, studies on collagen expression and matrix formation after injury of regenerating versus non-regenerating nervous systems are reviewed. Major differences in collagen deposition in the CNS and the peripheral nervous system (PNS) and differences in specific cell responses to extracellular matrix deposition in the lesion area are discussed. Therapeutic treatments aiming at suppression of fibrous scarring have been shown to promote axon regeneration in various lesion paradigms of the mammalian CNS.

Characterization of the secreted proteome of rat hepatocytes cultured in collagen sandwiches

Analysis of proteins in biological samples opens up the possibility of discovering new markers of toxicity. The liver is one of the primary targets of drug-induced toxicity, and it also secretes many plasma proteins, which can be measured clinically. Most of the plasma proteins produced by the liver are secreted by hepatocytes, but there is little information regarding the protein profile secreted by these cells. The purpose of this study was to analyze the secreted proteome of primary rat hepatocytes in a collagen gel sandwich configuration by a gel-LC-MS/MS procedure. We identified over 600 peptides corresponding to more than 200 proteins. The protein profile included over 50 plasma proteins, suggesting that the cultured hepatocytes secrete many of the proteins that they produce in vivo. Our data also suggests that the hepatocytes are actively remodeling their environment, since we identified several structural extracellular matrix proteins as well as some proteins known to be secreted specifically during liver regeneration. We also identified two proteins, alpha1-antitrypsin and alpha2-macroglobulin, whose secretions appear to be down-regulated in cells exposed to aflatoxin B1. It was noted that a 15 nM dose of aflatoxin B1 led to substantially diminished levels of these proteins and that day 6 of incubation was the ideal time point for medium collection. These data suggest that proteins in the conditioned medium of hepatocyte sandwich culture might lead to the discovery of biomarkers for drug-induced chemical toxicity.

The extracellular matrix environment in suture morphogenesis and growth

Sutures are the major bone growth sites of the craniofacial skeleton and form in response to developmental approximation of and interaction between two opposing osteogenic fronts. Premature obliteration of these craniofacial bone growth sites or craniosynostosis results in compensatory growth at other bone growth sites, with concomitant craniofacial dysmorphology. While much is now known about the growth and transcriptional factor regulation of suture formation and maintenance, little about the nature of the extracellular environment within sutures and their surrounding bones has been described. This review elucidates the nature of the sutural extracellular matrix and its role in mediating suture maintenance and growth through the regulation of cellular and biomechanical signaling.

Antibodies against the NG2 proteoglycan promote the regeneration of sensory axons within the dorsal columns of the spinal cord

The NG2 chondroitin sulfate proteoglycan inhibits axon growth in vitro. Levels of NG2 increase rapidly in the glial scars that form at sites of CNS injury, suggesting that NG2 may inhibit axon regeneration. To determine the functions of NG2, we infused mixtures of neutralizing or non-neutralizing anti-NG2 monoclonal antibodies into the dorsally transected adult rat spinal cord and analyzed the regeneration of ascending mechanosensory axons anatomically. At 1 week after injury, ascending sensory axons in control animals terminated caudal to the lesion within an area containing dense deposits of NG2 immunoreactivity. In animals treated with the neutralizing anti-NG2 antibodies, labeled axons penetrated the caudal border of the lesion and grew into and beyond the lesion center. The low intrinsic growth capacity of adult neurons may also limit the ability of damaged axons to regenerate. To enhance growth, we combined antibody treatment with a peripheral nerve conditioning lesion. After a conditioning lesion and treatment with control, non-neutralizing antibodies, many sensory axons grew into the lesion core. These axons did not grow past the rostral border of the lesion; rather, they grew along the dorsal surface of the spinal cord and within any remaining pieces of the dorsal roots. In contrast, combining a peripheral nerve conditioning lesion with neutralizing anti-NG2 antibodies resulted in sensory axon regeneration past the glial scar and into the white matter rostral to the injury site. The combinatorial approach used here that neutralizes extrinsic inhibition and increases intrinsic growth results in anatomically correct axon regeneration, a prerequisite for functional recovery.

The genetics of Fraser syndrome and the blebs mouse mutants

Fraser syndrome is a recessive multisystem disorder characterized by embryonic epidermal blistering, cryptophthalmos, syndactyly, renal defects and a range of other developmental abnormalities. More than 17 years ago, the family of four mapped mouse blebs mutants was proposed as models of this disorder, given their striking phenotypic overlaps. In the last few years, these loci have been cloned, uncovering a family of three large extracellular matrix proteins and an intracellular adapter protein which are required for normal epidermal adhesion early in development. The proteins have also been shown to play a crucial role in the development and homeostasis of the kidney. We review the cloning and characterization of these genes and explore the consequences of their loss.

NG2-expressing cells in the nervous system: role of the proteoglycan in migration and glial-neuron interaction

The NG2 glycoprotein is a type I membrane protein expressed in the developing and adult central nervous system (CNS) by subpopulations of glia including oligodendroglial precursor cells (OPCs), and in the developing CNS additionally by pericytes. In the mouse CNS, expression of NG2 protein is already observed at embryonic day 13 and peaks between postnatal days 8 and 12. NG2+ cells persist in grey and white matter in adult mouse brain: cells in the developing and adult brain show clear differences in migration, cell-cycle length and lineage restriction. Several groups have provided evidence that subpopulations of NG2+ cells can generate neurons in vivo. Neuronal stimulation in the developing and adult hippocampus leads to Ca2+ signals in apposing NG2+ glia, suggesting that these cells may modulate synaptic activity, and NG2+ cells often ensheath synapses. The structure of the protein with two N-terminal LamininG/Neurexin/Sex-hormone-binding globulin domains suggests a role in adhesion. The C-terminal PSD-95/DiscsLarge/Zona Occludens-1 (PDZ)-binding motif has been found to associate with several PDZ proteins including the Glutamate Receptor Interacting Protein GRIP: NG2 may thus act to position AMPA receptors on glia towards sites of neuronal glutamate release. Furthermore, the NG2 proteoglycan plays a role in cell migration and spreading and associates with actin-containing cytoskeletal structures.

Localization of extracellular matrix receptors on the chondrocyte primary cilium

A single primary cilium is found in chondrocytes and other connective tissue cells. We have previously shown that extracellular matrix (ECM) macromolecules such as collagen fibers closely associate with chondrocyte primary cilia, and their points of contact are characterized by electron-opaque plaques suggesting a direct link between the ECM and the cilium. This study examines the expression of receptors for ECM molecules on chondrocyte primary cilia. Embryonic chick sterna were fluorescently labeled with antibodies against alpha and beta integrins, NG2, CD44, and annexin V. Primary cilia were labeled using acetylated alpha-tubulin antibody. Expression of ECM receptors was examined on chondrocyte plasma membranes and their primary cilia using immunofluorescence and confocal microscopy. All receptors examined showed a punctate distribution on the plasma membrane. alpha2, alpha3, and beta1 integrins and NG2 were also present on primary cilia, whereas annexin V and CD44 were excluded. The number of receptor-positive cilia varied from 8/50 for NG2 to 43/50 for beta1 integrin. This is the first study to demonstrate the expression of integrins and NG2 on chondrocyte primary cilia. The data strongly suggest that chondrocyte primary cilia have the necessary machinery to act as mechanosensors, linking the ECM to cytoplasmic organelles responsible for matrix production and secretion.

Automated genomic sequence analysis of the three collagen VI genes: applications to Ullrich congenital muscular dystrophy and Bethlem myopathy

INTRODUCTION

Mutations in the genes encoding collagen VI (COL6A1, COL6A2, and COL6A3) cause Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD). BM is a relatively mild dominantly inherited disorder with proximal weakness and distal joint contractures. UCMD is an autosomal recessive condition causing severe muscle weakness with proximal joint contractures and distal hyperlaxity.

METHODS

We developed a method for rapid direct sequence analysis of all 107 coding exons of the COL6 genes using single condition amplification/internal primer (SCAIP) sequencing. We have sequenced all three COL6 genes from genomic DNA in 79 patients with UCMD or BM.

RESULTS

We found putative mutations in one of the COL6 genes in 62% of patients. This more than doubles the number of identified COL6 mutations. Most of these changes are consistent with straightforward autosomal dominant or recessive inheritance. However, some patients showed changes in more than one of the COL6 genes, and our results suggest that some UCMD patients may have dominantly acting mutations rather than recessive disease.

DISCUSSION

Our findings may explain some or all of the cases of UCMD that are unlinked to the COL6 loci under a recessive model. The large number of single nucleotide polymorphisms which we generated in the course of this work may be of importance in determining the major phenotypic variability seen in this group of disorders.

Targeting of pericytes diminishes neovascularization and lymphangiogenesis in prostate cancer

BACKGROUND

The walls of capillaries in prostate cancer are composed of endothelial cells, and pericytes. NG2 is a transmembrane proteoglycan on nascent pericytes with a functional role in neovascularization.

METHODS

The anti-angiogenic effect of hydron pellets containing NG2 neutralizing antibody was quantified in intracorneal PC-3 and LNCaP xenografts. TRAMP and TRAMP-C1 tumors grafted in NG2 knockout mice represented intrinsic pericyte targeting. TRAMP and TRAMP-C1 grafts were analyzed with confocal microscope for microvascular density (MVD) and lymphatic vascular density (LVD).

RESULTS

NG2 neutralizing antibody decreased corneal neovascularization in PC3 (P<0.0001), and LNCaP (P=0.0079) xenografts. Mean MVD in TRAMP and TRAMP-C1 tumors in NG2 knockout mice were 71% (P=0.0006) and 63% (P=0.0011) lower than wild type controls, respectively. Mean LVD in TRAMP and TRAMP-C1 tumors in NG2 knockout mice were 73% (P=0.0003) and 84% (P<0.0001) lower than wild type controls, respectively.

CONCLUSIONS

Targeting of pericyte-NG2 decreases neovascularization and lymphangiogenesis in prostate cancer significantly.

Altered expression of the MCSP/NG2 chondroitin sulfate proteoglycan in collagen VI deficiency

NG2, the rat homologue of the human melanoma chondroitin sulfate proteoglycan (MCSP), is a ligand for collagen VI (COL6). We have examined skeletal muscles of patients affected by Ullrich scleroatonic muscular dystrophy (UCMD), an inherited syndrome caused by COL6 genes mutations. A significant decrease of NG2 immunolabeling was found in UCMD myofibers, as well as in skeletal muscle and cornea of COL6 null-mice. In UCMD muscles, truncated NG2 core protein isoforms were detected. However, real-time RT-PCR analysis revealed marked increase in NG2 mRNA content in UCMD muscle compared to controls. We hypothesize that NG2 immunohistochemical and biochemical behavior may be compromised owing to the absence of its physiological ligand. MCSP/NG2 proteoglycan may be considered an important receptor mediating COL6-sarcolemma interactions, a relationship that is disrupted by the pathogenesis of UCMD muscle.

Contribution of bone marrow-derived pericyte precursor cells to corneal vasculogenesis

PURPOSE

Bone-marrow (BM)-derived hematopoietic precursor cells are thought to participate in the growth of blood vessels during postnatal vasculogenesis. In this investigation, multichannel laser scanning confocal microscopy and quantitative image analysis were used to study the fate of BM-derived hematopoietic precursor cells in corneal neovascularization.

METHODS

A BM-reconstituted mouse model was used in which the BM from enhanced green fluorescent protein (GFP)-positive mice was transplanted into C57BL/6 mice. Basic fibroblast growth factor (bFGF) was used to induce corneal neovascularization in mice. The vasculogenic potential of adult BM-derived cells and their progeny were tested in this in vivo model. Seventy-two histologic sections selected by systematic random sampling from four mice were immunostained and imaged with a confocal microscope and analyzed with image-analysis software.

RESULTS

BM-derived endothelial cells did not contribute to bFGF-induced neovascularization in the cornea. BM-derived periendothelial vascular mural cells (pericytes) were detected at sites of neovascularization, whereas endothelial cells of blood vessels originated from preexisting blood vessels in limbal capillaries. Fifty three percent of all neovascular pericytes originated from BM, and 47% of them originated from preexisting corneoscleral limbus capillaries. Ninety-six percent and 92% of BM-derived pericytes also expressed CD45 and CD11b, respectively, suggesting their hematopoietic origin from the BM.

CONCLUSIONS

Pericytes of new corneal vessels have a dual source: BM and preexisting limbal capillaries. These findings establish BM as a significant effector organ in corneal disorders associated with neovascularization.

A simple method for measuring interstitial fluid pressure in cancer tissues

A novel procedure using a polyurethane transducer-tipped catheter (Millar) is described that allows reliable measurement of interstitial fluid pressure (IFP) in cancer tissues. Before and after each use, the transducer is calibrated at 37 degrees C by a water column. After calibration, the transducer is passed through the lumen of a surgical needle. The sensor is kept in the lumen of the needle during penetration into the tumor. The sensor tip is then introduced into the center core of the tumor as the needle sleeve is withdrawn from the tumor surface. Our new technique is simple and provides IFPs equal to those provided by the well-established, wick-in-needle technique. Using our new technique, we compared IFP in skin melanoma grafts in NG2 knockout and wild-type mice. Knocking out NG2 proteoglycan on vasculogenic and angiogenic pericytes reduced interstitial fluid pressure in melanoma from +4.9 cm H2O to -0.4 cm H2O (P=0.0054 Mann-Whitney U test).