Construction of perineuronal net-like structure by cortical neurons in culture

Perineuronal nets consisting of chondroitin sulfate proteoglycans and hyaluronic acid are associated with distinct neuronal populations in mammalian brain. Whether neurons or glia cells produce these surface-associated chondroitin sulfate proteoglycan perineuronal nets has remained in question. In the present study, we observed perineuronal net-like structure by rat cortical neurons in dissociated culture using Wisteria floribunda aggulutinin, hyaluronic acid binding protein, and the antibodies recognizing chondroitin sulfate proteoglycans. The double labeling experiments showed that perineuronal net-like structure labeled with Wisteria floribunda aggulutinin was observed often at parvalbumin-positive neurons in dissociated cortical culture without glia. Perineuronal net-like structure was not seen at the early stage of culture, but they became visible concomitantly with neuronal maturation after longer culture. High magnification observation further demonstrated that Wisteria floribunda aggulutinin labeling on cortical neurons was seen as numerous puncta along surface of somata and proximal dendrites, but not axons and synapses. Perineuronal net-like structure on cultured neurons was also visualized using chondroitin sulfate proteoglycan-specific antibodies and hyaluronic acid binding protein. Double labeling study demonstrated that perineuronal net-like structure in cultured cortical neurons was composed of chondroitin sulfate proteoglycans such as neurocan and phosphacan. The hyaluronidase treatment of live neurons abolished cellular labeling of hyaluronic acid binding protein and concomitantly diminished that of Wisteria floribunda aggulutinin. These results indicate that cultured cortical neurons are able to construct perineuronal net-like structure without glial cells.

Variable Adhesion Abilities and Overlapping Antigenic Properties in PlacentalPlasmodium falciparumIsolates

BACKGROUND

Pregnancy-associated malaria is characterized by selection and multiplication, in the placenta, of a distinct population of Plasmodium falciparum expressing particular variant surface antigens (VSAs) that adhere to chondroitin sulfate A (CSA).

METHODS

The adhesion of 40 freshly collected placental parasite isolates to bovine CSA and human placental low-sulfated chondroitin proteoglycans (CSPGs) was investigated. Plasma samples from 30 pregnant women were used to test, by flow cytometry, their recognition of and their adhesion-inhibition capacity toward 6 of these isolates.

RESULTS

Adhesion to CSA and CSPGs varied between isolates but was strongly correlated between receptors (P<.001). Adhesion of isolates to receptors strongly and negatively correlated with low birth weight (LBW) of the neonate (odds ratio [95% confidence interval], 5.2 [1.1-25.1]). In plasma samples from pregnant women, the level of specific immunoglobulin G against each placental isolate (anti-VSA(PAP)) strongly correlated with the level of anti-VSA(PAP) antibodies against all other isolates (P<.05) and increased with parity in all isolates (P<.01). Conversely, adhesion-inhibitory antibodies did not correlate with isolates or with the level of anti-VSA(PAP) antibodies.

CONCLUSION

The level of adhesion of placental parasites to chondroitin sulfate receptors is an important risk factor for LBW. Parasite heterogeneity suggests that they are composed of mixed adhesion phenotypes capable of inducing immune responses to a range of different and overlapping targets.

ADAMTS4 (aggrecanase-1) cleaves human brain versican V2 at Glu405-Gln406 to generate glial hyaluronate binding protein

Human brain tissue from cerebellum and hippocampus was obtained between 2 h and 24 h post mortem and, after extraction in the presence of proteinase inhibitors, proteoglycans were purified by anion-exchange chromatography. The versican component was characterized by Western analysis with antibodies to the N-terminal peptide (LF99), the N-terminal globular domain (12C5) and the two GAG (glycosaminoglycan) attachment regions (anti-GAG-alpha and anti-GAG-beta). The results indicated that versican V2 is the major variant in all brain samples, and that it exists as the full-length form and also as at least six C-terminally truncated forms. The major immunoreactive species present is a 64 kDa product, which we identified by biochemical and immunological analysis as the brain protein previously termed GHAP (glial hyaluronate binding protein) [Perides, Lane, Andrews, Dahl and Bignami (1989) J. Biol. Chem. 264, 5981-5987]. Immunological analysis of purified human GHAP using a new anti-neoepitope antiserum (JSCNIV) showed that its C-terminal sequence is NIVSFE(405), and digestion of human cerebellum proteoglycans with ADAMTS4 (aggrecanase-1, where ADAMTS, a disintegrin and metalloproteinase with thrombospondin-1-like motifs) indicated that GHAP is a product of cleavage of versican V0 or V2 at the Glu(405)-Gln(406) bond. Since human cerebellum extracts contained multiple forms of ADAMTS4 protein on Western analysis, these data suggest that one or more members of the 'aggrecanase' group of the ADAMTS family (ADAMTS 1, 4, 5 and 9) are responsible for turnover of versican V2 in the adult human brain.

Use of a novel double-sandwich enzyme-linked immunosorbent assay method for assaying chondroitin sulfate proteoglycans that bear 3-nitrotyrosine core protein modifications, a previously unrecognized proteoglycan modification in hydrocephalus

3-Nitrotyrosine is a useful marker for nitric oxide-mediated tissue injury. However, which proteins are preferred peroxynitrite modification targets is unclear. Chondroitin sulfate proteoglycans (CSPGs) abnormally accumulate in cerebrospinal fluid of human neonates with hydrocephalus and may be a target for peroxynitrite modification. We examined (1). whether CSPG core protein can be modified by peroxynitrite in vitro; (2). to what degree in comparison to bovine serum albumin (BSA), the most commonly used nitrated protein standard; (3). whether nitrated CSPGs can be measured directly in biological samples; and (4). whether nitrated proteoglycan concentrations in cerebrospinal fluid correlate with disease. In vitro nitration of bovine aggrecan was performed by exposure to different peroxynitrite concentrations, and 3-nitrotyrosine products were measured. Bovine serum albumin (BSA) nitration was also performed in comparison. A larger percentage of tyrosine residues were nitrated in aggrecan than in BSA under all conditions tested. An enzyme-linked immunosorbent assay (ELISA) for 3-nitrotyrosine consistently overestimated aggrecan nitration when nitrated BSA was used as the standard. This is important as most current assays of nitration in biological samples use nitrated BSA as the standard. Therefore, if nitrated CPSGs were a substantial portion of the nitrated proteins in a sample, total nitrated protein content would be overestimated. Aggrecan retained its function of binding hyaluronic acid despite substantial nitration. A double-sandwich ELISA was developed for nitrated CSPGs in biological samples, using nitrated aggrecan as standard. [Nitrated CSPG] was found to be significantly elevated in preterm hydrocephalus cerebrospinal fluid (P<0.02), but correlated poorly with cerebrospinal fluid [nitric oxide] (P>0.069), suggesting that nitrated CSPG and NO levels may be independant markers of tissue injury. Peroxynitrite-mediated protein tyrosine nitration is a previously unrecognized modification of CSPGs, and may reflect level of brain injury in hydrocephalus.

Cohesin component dynamics during meiotic prophase I in mammalian oocytes

Cohesins are chromosomal proteins that form complexes involved in the maintenance of sister chromatid cohesion during division of somatic and germ cells. Three meiosis-specific cohesin subunits have been reported in mammals, REC8, STAG3 and SMC1 beta; their expression in mouse spermatocytes has also been described. Here we studied the localization of different meiotic and mitotic cohesin components during prophase I in human and murine female germ cells. In normal and atretic human fetal oocytes, from leptotene to diplotene stages, REC8 and STAG3 colocalize in fibers. In murine oocytes, SMC1beta, SMC3 and STAG3 are localized along fibers that correspond first to the chromosome axis and then to the synaptonemal complex in pachytene. Mitotic cohesin subunit RAD21 is also found in fibers that decorate the SC during prophase I in mouse oocytes, suggesting a role for this cohesin in mammalian sister chromatid cohesion in female meiosis. We observed that, unlike human oocytes, murine synaptonemal complex protein SYCP3 localizes to nucleoli throughout prophase I stages, and centromeres cluster in discrete locations from leptotene to dictyate. At difference from meiosis in male mice, the cohesin axis is progressively lost during the first week after birth in females with a parallel destruction of the axial elements at dictyate arrest, demonstrating sexual dimorphism in sister chromatid cohesion in meiosis.

Experimental immunity to the G1 domain of the proteoglycan versican induces spondylitis and sacroiliitis, of a kind seen in human spondylarthropathies

OBJECTIVE

Experimental immunity to the G1 domain of the cartilage proteoglycan (PG) aggrecan (AG1) leads to the development of spondylitis as well as polyarthritis in BALB/c mice. The PG versican contains a structurally similar G1 domain (VG1). This study was conducted to determine whether immunity to VG1 would elicit similar pathology in these mice.

METHODS

Recombinant natively folded VG1 and AG1 were prepared. BALB/c mice received either a series of 5 injections of human VG1 or AG1, or no protein. Polyarthritis was determined clinically, and spondylitis and sacroiliitis histologically. Immunohistochemistry of rat tissues was used to study the localization of versican. Enzyme-linked immunosorbent assays were employed to study humoral immunity to the recombinant proteins as well as to overlapping synthetic peptides covering all these human G1 domains and mouse homologs. Affinity-purified antibodies to human AG1 and VG1 were isolated from sera of hyperimmunized mice. T lymphocyte proliferation assays were performed using recombinant human proteins. T cell lines reactive with specific immunodominant T cell epitopes in human AG1 and VG1 were isolated. Synthetic peptides encoding sequences in these human proteins and in corresponding mouse proteins were used in these analyses. Guanidinium chloride extracts of mouse spines were also used in Western blots to study antibody cross-reactivity.

RESULTS

Immunity to recombinant VG1 did not result in clinical polyarthritis. There was, however, clear evidence that VG1, like AG1, could induce spondylitis in the lumbar spine and sacroiliitis. Accumulation of mononuclear cells was observed in spinal ligaments adjacent to the intervertebral disc, in the intervertebral disc, and in the sacroiliac joints, the same sites where versican is localized. In contrast to AG1-immunized mice, in which T cells reactive with human AG1 cross-reacted with mouse AG1, there was no evidence in VG1-immunized mice that T cell immunity to human VG1 was cross-reactive with a mouse synthetic peptide that contained the sequence corresponding to the single immunodominant T cell sequence recognized in human VG1. Antibodies to specific sequences in human VG1 did, however, cross-react with human AG1 and with corresponding peptide sequences in mouse versican and aggrecan and with mouse proteins containing VG1 and AG1, present in mouse spine extracts. Similarly, antibodies to human AG1 cross-reacted with human VG1 and with extracted mouse VG1 and AG1 and synthetic peptides containing mouse sequences that corresponded to the reactive human epitopes in AG1 and VG1.

CONCLUSION

These observations suggest that humoral immunity to human VG1 is involved in the induction of experimental spondylitis and sacroiliitis in BALB/c mice. This humoral immunity is cross-reactive with mouse versican and aggrecan but is not associated with polyarthritis, probably because of the lack of cross-reactive T cell immunity and the absence of detectable versican in articular cartilage limbs. Induction of polyarthritis by bovine or human aggrecan requires the involvement of immunity mediated by T lymphocytes that are cross-reactive to a mouse aggrecan epitope. Together these observations suggest that humoral immunity to versican as well as immunity to aggrecan may be of importance in the development of the spinal pathology characteristic of spondylarthropathies.

Proteoglycans of Wharton's jelly

Wharton's jelly (WJ) is a myxomatous substance surrounding the blood vessels of the umbilical cord. Proteoglycans (PGs) of Wharton's jelly have not been studied to date therefore it was decided to explore proteoglycan composition of this tissue. Proteoglycans were subjected to dissociative extraction with 4M guanidine hydrochloride containing Triton X-100 and protease inhibitors, purified by Q-Sepharose anion-exchange chromatography and lyophilised. They were analysed by gel filtration and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) before and after treatment with chondroitinase ABC. It was found that 1g of Wharton's jelly contains 2.43+/-0.63mg (n=10) of sulphated glycosaminoglycans (GAGs), reflecting the presence of proteoglycans. The proteoglycans were mainly substituted with chondroitin/dermatan sulphate (DS) chains. The predominant proteoglycan fraction included small proteoglycans with core proteins of 45 and 47kD, immunologically related to decorin (45 and 47kD) and biglycan (45kD). The expression of decorin core proteins was much higher than that of biglycan. Larger proteoglycans (core proteins of 90, 110, 220 and 260kD) were found in lower amounts. The most abundant of them (core protein of 260kD) was immunologically related to versican. Perlecan was not identified in Wharton's jelly. The study shows that Wharton's jelly contains mainly small chondroitin/dermatan sulphate proteoglycans, with decorin strongly predominating over biglycan. We suggest that an intensive expression of decorin is associated with very high content of its ligand, collagen.

Monoclonal antibody 4C4-mAb specifically recognizes keratan sulphate proteoglycan on human embryonal carcinoma cells

Germ cell tumours, the most common solid cancers in young males, display pluripotentiality for embryonal and somatic differentiation. Specific surface antigens are useful in the study of cellular differentiation and for clinical diagnosis. A mouse monoclonal antibody (4C4-mAb) has been developed against a human embryonal carcinoma (EC) cell line (NCR-G3) isolated from a combined form of testicular germ cell tumour. On immunohistological and immuno-electron microscopic examination, the 4C4 antigen (4C4) was detected on the surface of NCR-G3 and gold particles were exclusively detected on the microvilli of the cells. In both formalin-fixed paraffin wax sections and touch-smear specimens, 4C4 was detected specifically in EC, while the antigen was not expressed in other types of germ cell tumour or in the other solid tumours tested. Tunicamycin diminished the antigenicity of NCR-G3 cells. In biochemical studies, 4C4 was found in a high molecular weight region ranging from 1 x 10(6) to 1 x 10(7) kD, which disappeared after periodate treatment. The density of 4C4 was 1.5 g/cm(3) after equilibrium centrifugation. These results imply that 4C4 is a proteoglycan. Furthermore, endo- and exo-glycosidase treatment revealed that 4C4 is a keratan sulphate proteoglycan that contains sialyl and fucosyl moieties. With EC-specific and formalin-resistant characteristics, 4C4 may be a specific marker for diagnosing EC among a variety of germ cell tumours.

Increased expression of the putative axon growth-repulsive extracellular matrix molecule, keratan sulphate proteoglycan, following traumatic injury of the adult rat spinal cord

Keratan sulphate proteoglycan (KSPG) is a developmentally regulated barrier molecule, directing axonal growth during central nervous system (CNS) formation. The possible re-expression and functional significance of KSPG in preventing axon regeneration following spinal cord injury (SCI) is poorly understood. In the present investigation, the spatio-temporal expression of KSPG was studied following experimental SCI. There was no indication of sparing of axons at the lesion epicentre following severe compression injury. By 7 days post operation (p.o.) a diffuse increase of KSPG immunoreactivity (KSPG-IR) was observed in the parenchyma surrounding the lesion. This was followed by a delayed (21-28 days p.o.) and largely heterogeneous increase of KSPG-IR in the lesion epicentre, which revealed both cellular and extracellular matrix-like distribution patterns. Although no re-growth of anterogradely labelled corticospinal axons was observed, many 200-kDa neurofilament (NF)-positive axons could be detected growing into the connective tissue scar. This phase of spontaneous axonal re-growth was closely associated with a framework of glial cells (including Schwann cells from damaged local spinal nerve roots) that had migrated into the lesion site. The spontaneous nerve fibre re-growth could be detected in both KSPG-rich and KSPG-poor territories. The present data suggest that the lesion-induced up-regulation of KSPG-IR may have contributed to the lack of corticospinal axon re-growth. However, the lack of any direct spatio-temporal correlation between the distribution of raised KSPG-IR and spontaneous NF-positive axonal regeneration suggests that at least some populations of axons can resist the putative inhibitory effects of this extracellular matrix molecule.

Immunological studies of sheep brain keratan sulphate proteoglycans

Recently, we reported the isolation and partial characterization of keratan sulphate (KS) from sheep brain. In this study, a panel of monoclonal antibodies (Mab) recognizing epitopes within KS chains and core proteins of KS-containing proteoglycans were used to detect, by immunoblotting, antigenically related molecules extracted from cerebrum, cerebellum and brainstem, respectively. Although the intensity of labelling varied with each of the antibodies, the brain KSPGs were recognized by all the monoclonals used, confirming the presence of KS side chains, which react with the Mabs: 5-D-4, EFG-11, EFG-4, I22, as also the presence of KSPGs related to phosphacan-KS (3H1 proteoglycan). Extracts of all the three brain areas could bind both anti-KS and anti-core protein Mabs, as also anti-HNK-1 monoclonal antibody. Binding was sensitive to keratanases degradation in the cerebrum and brainstem except cerebellum where the presence of a large molecular size hybrid CS/KSPG bearing KS chains partially resistant to keratanases was identified. This population reacts only with 5-D-4, EFG-11 and EFG-4 antibodies. Furthermore, the presence of HNK-1 epitope in CSPGs was detected in the cerebellum and brainstem. In contrast, in the cerebrum the coexistence of HNK-1 epitope and KS in KSPGs was identified. These data suggest that the KSs of sheep brain are part of proteoglycans containing protein and KS antigenic sites related to those of corneal and cartilage KSPG, as also of the brain proteoglycan phosphacan-KS.

Animal models of ankylosing spondylitis

The pathology of ankylosing spondylitis (AS) and related spondyloarthropathies (SpA) characteristically involve a sacroiliitis and inflammation of the intervertebral discs (IVD) in the lumbar spine, and an enthesitis at sites of ligamentous insertions into bone. The proteoglycans aggrecan and versican are large molecules that aggregate with hyaluronic via a globular 1 domain. These domains share significant homology at the level of B and T cell epitope recognition. Both proteoglycans are present in the intervertebral disc and hyaline cartilages of the sacroiliac joint, as well as in entheses. Whereas aggrecan is most concentrated in the nucleus of the IVD and in articular cartilages and endplates, versican is generally absent from these tissues except in the sacroiliac joint, but is concentrated in ligaments and the annulus. Immunity to these molecules in BALB/c mice results in an AS-like pathology, including sacroiliitis, enthesitis, and discitis. The pathology of AS is closely associated with the expression of the class I molecule human leukocyte antigen-B27. Rats bearing this transgene develop an AS-like pathology, as well as other various signs of autoimmunity. Ankylosing spondylitis is characterized by an ankylosing pathology whereby bone formation in the annulus leads to intervertebral fusion. Mice bearing the ank/ank defect gene develop a bony ankylosis of the spine like that seen in advanced AS and related SpA. These three animal models provide insight into the pathogenesis of SpA, and opportunities to investigate their pathology in relationship to human disease where investigation of the pathobiology is very difficult, because of restricted access to involved tissues.

Chondroitin sulfate proteoglycan phosphacan/RPTPbeta in the hypothalamic magnocellular nuclei

The hypothalamo-neurohypophysial system synthesizes and releases arginine vasopressin (AVP) and oxytocin (OXT) with physiological stimulation. In the present study, we investigated localization of a chondroitin sulfate proteoglycan (CSPG), phosphacan/RPTPbeta, in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of adult rats at both the light and electron microscopic levels. Immunohistochemical analyses demonstrated stronger phosphacan/RPTPbeta immunoreactivity within the SON and PVN compared with adjacent hypothalamic areas. Double labeling experiments showed phosphacan/RPTPbeta immunoreactivity constituting punctate networks to surround the somata and dendrites of AVP- and OXT-secreting magnocellular neurons. Electron microscopic examination further revealed strong phosphacan/RPTPbeta immunoreactivity at extracellular membrane surface of some axons, somata, and dendrites of the SON, but not of synaptic junctions. Interestingly, phosphacan/RPTPbeta immunoreactivity was also observed at extracellular surface membrane between astrocytic processes and neurons rather than between magnocellular neurons. The present results indicate the high expression of the CSPG, phosphacan/RPTPbeta at the extracellular space in the hypothalamic AVP- and OXT-secreting magnocellular neurons.

Biochemical properties of a keratan sulphate/chondroitin sulphate proteoglycan expressed in primate pluripotent stem cells

We previously identified a pericellular matrix keratan sulphate/chondroitin sulphate proteoglycan present on the surface of human embryonal carcinoma stem cells, cells whose differentiation mimics early development. Antibodies reactive with various epitopes on this molecule define a cluster of differentiation markers for primate pluripotent stem cells. We describe the purification of a form of this molecule which is secreted or shed into the culture medium. Biochemical analysis of the secreted form of this molecule shows that the monomeric form, whilst containing keratan sulphate, resembles mucins in its structure and its modification with O-linked carbohydrate. Immunofluorescence and immunoblotting data show that monkey and human pluripotent stem cells react with antibodies directed against epitopes on either carbohydrate side chains or the protein core of the molecule.

Autoimmune lymphoproliferative syndromes (ALPS): models for the study of peripheral tolerance

Lymphocyte cell death is a key event in the homeostasis of the immune system. Lymphocytes can be induced to die because of exposure to toxic agents, because of cytokine withdrawal or because specific cell surface receptors are engaged by their ligands. A number of such receptors belonging to the TNF receptor have been described in the recent past. Among these, the role of the Fas ligand/receptor interaction in the induction of lymphocyte cell death has been enlightened by the study of natural mutants, first described in mouse strains, then in humans. This review discusses the main findings provided by murine studies and clinical observations.

Immunohistochemical localization of large chondroitin sulphate proteoglycan in porcine gingival epithelia

In this study, we report the immunohistochemical localization of versican in healthy porcine gingival epithelia. The monoclonal antibody (mAb), 5D5, specifically recognizes core proteins of large chondroitin sulphate proteoglycans such as versican, neurocan and brevican, but not the core protein of aggrecan. Because neurocan and brevican appear to be specific to nervous tissue, the large chondroitin sulphate proteoglycans examined in this study is most likely versican. In the keratinized layer of the attached gingival epithelium, the basal and spinous cell surfaces showed intense staining for mAb 5D5. In the parakeratinized layer of the sulcus epithelium, the localization was restricted to the basal and lower spinous layers. In the junctional epithelium, intense staining was observed in one or two cell layers near the enamel surface. Immunoelectron microscopy revealed high-density depositions of 5D5 immunoreactivity on epithelial cell surfaces. At the enamel surface, 5D5 immunoreactivity was localized to the dental cuticle of the junctional epithelium but was not present in the internal basal lamina. These results suggest that versican, a large chondroitin sulphate proteoglycan, is involved in epithelial differentiation and downgrowth.

Inhibitory proteoglycan immunoreactivity is higher at the caudal than the rostral Schwann cell graft-transected spinal cord interface

To begin to evaluate the influence that proteoglycans may have on the success of Schwann cell (SC) transplants to induce axonal regrowth across a complete transection lesion and beyond, we determined the pattern of expression of inhibitory chondroitin sulfate proteoglycans (CSPGs) 3 weeks after transplantation into completely transected adult rat thoracic spinal cord. Using immunohistochemistry, we observed that: (1) CSPGs recognized by CS-56 antibody are present on astrocytes, fibroblasts, and SCs in the distal graft, and at lesion and cystic cavity borders; (2) CS-56 immunoreactivity (IR) is greater at the caudal SC graft-host cord interface than the rostral interface; (3) phosphacan-IR, also greater at the caudal interface, is associated with astrocytes, fibroblasts, as yet unidentified cells, and extracellular matrix; (4) neurocan-IR is present on astrocytes and as yet unidentified cells in grey and white matter; and (5) NG2-IR is associated with matrix near SC grafts, unidentified cells mainly in white matter, and lesion borders and cysts. Neither oligodendrocytes nor activated macrophages/microglia were immunostained. In sum, the CSPGs studied are increased at 3 weeks, especially at the caudal SC graft-cord interface, possibly contributing to an inhibitory molecular barrier that precludes regrowing descending axons from entering the caudal host cord.

Immunolocalization of keratan sulfate proteoglycan in rat calvaria

We investigate, by the immunogold method, the localization of keratan sulfate (KS) proteoglycan in rat calvaria in order to clarify the detailed process of intramembranous ossification. KS was localized in bone nodules corresponding to calcified nodules, close to the saggital suture of calvaria. The immunoreactivity decreased in fully calcified regions distant from the suture. Electron microscopic observation revealed that KS was distributed in and around matrix vesicles, among collagen fibrils at the initial crystal deposition stage, and then concentrated in bone nodules. According to the progress of mineralization, KS tended to be localized in the peripheral region of the nodules. In addition, these nodules came in contact with collagen fibrils which also showed KS-positive reactivity. In cell organelles of osteoblasts, KS was detected in the Golgi apparatus. These findings suggest that osteoblasts in intramembranous ossification sites actively synthesize KS. KS in the calcified nodules, as well as other glycosaminoglycans in osteoid, may play an important role in additional and/or collagenous calcification by trapping calcium ions through its negative charge.

Correlation of anti-idiotype network with survival following anti-G(D2) monoclonal antibody 3F8 therapy of stage 4 neuroblastoma

BACKGROUND

A transient human anti-mouse antibody response was associated with significantly longer survival [Cheung et al. (1998): J Clin Oncol 16:3053] following antibody 3F8 (Ab1) treatment. We postulate that the induction of an idiotype network which included anti-anti-idiotypic (Ab3) and anti-G(D2) (Ab3') responses is associated with tumor control.

PROCEDURE

Thirty-four patients with stage 4 neuroblastoma (NB) diagnosed at > 1 year of age were treated with anti-G(D2) monoclonal antibody 3F8 at the end of chemotherapy

RESULTS

Long-term progression-free survival and overall survival correlated significantly with Ab3' andAb3, but not with non-idiotypic antibody responses. Only one of six individual specificities showed significant correlations with patient survival.

CONCLUSIONS

As in vitro correlates of idiotype network initiated by Ab1 treatment, Ab3 and Ab3' may provide convenient biologic endpoints for monoclonal antibody therapy of advanced NB, and a rationale for choosing specific anti-idiotypic antibodies for vaccine development.

Further evidence for secretion of matrix metalloproteinase-1 by Meckel's chondrocytes during degradation of the extracellular matrix

We examined the possibility that chondrocytes in Meckel's cartilage might secrete matrix metalloproteinase-1 (MMP-1) during degradation of the extracellular matrix. Evidence for the secretion of MMP-1 was obtained by immunohistochemical staining and immunoelectron microscopy, in addition to general histochemical staining for proteoglycans. Not only staining with toluidine blue and alcian blue but also immunostaining for chondroitin sulfate proteoglycan (CSPG) revealed that levels of glycoproteins are rapidly reduced at the late stage of degradation. MMP-1 was detected continuously in cells from chondrocytes at the early stage to hypertrophic chondrocytes at the late stage. Immunoelectron microscopy revealed that the deposition of colloidal golds shifted from an intracellular localization in chondrocytes at the early stage to pericellular spaces at the late stage. The localization of tissue inhibitor of the metalloproteinase-1 (TIMP-1) at the early stage was similar to that of MMP-1, but the level of TIMP-1 decreased significantly in hypertrophic cartilage. These findings suggest that MMP-1 is present continuously in Meckel's chondrocytes but that the active form, which degrades the extracellular matrix, is the MMP-1 that accumulates in the pericellular spaces around hypertrophic chondrocytes.

Complex pattern of Th1 and Th2 activation with a preferential increase of autoreactive Th1 cells in BALB/c mice with proteoglycan (aggrecan)-induced arthritis

The central role of CD4+ T cells and the balance between T helper (Th) subpopulations in the pathogenesis of autoimmune diseases have been extensively studied. Proteoglycan (aggrecan)-induced arthritis (PGIA) is a murine model for rheumatoid arthritis (RA), which is characterized by a Th1 dominance at the onset of the disease. In addition to CD4+ T cells, antigen-presenting B cells and autoantibodies seem to play an important role in the development and regulation of PGIA. To identify proteoglycan-specific CD4+ T cell subsets and Th1- and Th2-supported antibody isotypes during the progression of PGIA, spleen cells of proteoglycan-immunized BALB/c mice were harvested at different times of immunization, and at different stages of the disease, and their cytokine production and antigen-specific antibody isotype profiles were determined by enzyme-linked immunospot (ELISPOT) assays. Both Th1 and Th2 cytokine-producing cells, with the predominance of IL-4/IL-5-secreting cells, were detected during the prearthritic stage, and a shift toward a Th1 dominance was observed at the time of onset of arthritis. Tissue homogenates of acutely inflamed joints contained significantly higher levels of interferon-gamma than IL-4. The prearthritic period and both the acute and chronic phases of joint inflammation were characterized by IgG1 dominance in the sera and this correlated with the number of IgG1-secreting B cells in the spleen. However, the ratio of autoreactive IgG1/IgG2a-secreting cells decreased in arthritic animals. These results indicate the activation and possible regulatory roles of both Th1 and Th2 subsets in the autoimmune process, with the necessity of a relative increase of autoreactive Th1 cells for the induction of joint inflammation.

Role of lumican in the corneal epithelium during wound healing

Lumican regulates collagenous matrix assembly as a keratan sulfate proteoglycan in the cornea and is also present in the connective tissues of other organs and embryonic corneal stroma as a glycoprotein. In normal unwounded cornea, lumican is expressed by stromal keratocytes. Our data show that injured mouse corneal epithelium ectopically and transiently expresses lumican during the early phase of wound healing, suggesting a potential lumican functionality unrelated to regulation of collagen fibrillogenesis, e. g. modulation of epithelial cell adhesion or migration. An anti-lumican antibody was found to retard corneal epithelial wound healing in cultured mouse eyes. Healing of a corneal epithelial injury in Lum(-/-) mice was significantly delayed compared with Lum(+/-) mice. These observations indicate that lumican expressed in injured epithelium may modulate cell behavior such as adhesion or migration, thus contributing to corneal epithelial wound healing.

Stromelysin-1 (MMP-3) in forming enamel and predentine in rat incisor-coordinated distribution with proteoglycans suggests a functional role

Stromelysin-1 (matrix metalloproteinase-3) or proteoglycanase was visualized by light and electron microscopy immunolabelling in the forming zone of rat incisors. In predentine, labelling was more dense at the transition zone between the inner proximal third and the two outer thirds. Odontoblast processes were also positively stained, mostly in predentine and to a lesser degree in dentine. The dentine-enamel junction was intensely labelled, whereas dentine and forming enamel were only faintly stained. Gold-antibodies complexes were seen inside secretory ameloblasts and odontoblasts in cytosolic locations. The distribution of stromelysin-1 was compared with the distribution of 2-B-6 epitope, an antibody recognizing chondroitin-4-sulphate/dermatan sulphate and which showed a decreasing gradient from the proximal zone to the distal part of predentine. In contrast, both 5-D-4, an anti-keratan sulphate antibody and an anti-lumican antibody displayed a reversed distribution, with an increase seen from the proximal and central thirds to the distal part of predentine. This coordinated distribution suggests that stromelysin-1 may have a functional role, being implicated in predentine in the degradation of chondroitin-4-sulphate/dermatan sulphate-containing proteoglycans, and consequently allowing keratan sulphate proteoglycan concentration to increase near the border where mineralization is initiated.

Immunohistochemical analysis of proteoglycan biosynthesis during early development of the chicken cornea

Antibodies to core proteins of chicken corneal keratan sulfate proteoglycan and chondroitin sulfate proteoglycan were prepared and purified by use of an affinity column. Using these antibodies and monoclonal antibody 5-D-4 to keratan sulfate (commercial), the localization of proteoglycans in developing corneas (Days 5 to 17 of embryonic age and 2 days after hatching) was determined immunohistochemically. Keratan sulfate proteoglycan antigen was not detected in cornea on Day 5, but it was detected uniformly over the whole stroma on Day 6, ca. 12 h after invasion of the primary stroma by mesenchymal cells. The absence of the antigen in cornea of Day 5 was confirmed by Western blotting of the corneal extract. Immunohistochemistry with 5-D-4 antibody revealed that the keratan sulfate chain was undersulfated in corneas of Days 6 to 7, because the staining was much weaker than that in cornea of Day 8. In addition, keratan sulfate proteoglycan antigen was detected uniformly over the whole stroma on Days 7 to 17 and 2 days after hatching, but not in the epithelial layer on Day 13 and after: because the epithelial layer was clearly not observed on photomicrographs until Day 13, it is not known whether keratan sulfate proteoglycan was synthesized by the epithelium during Days 6 to 12. In contrast, chondroitin sulfate proteoglycan antigen was detected in cornea on Day 5 and also, like keratan sulfate proteoglycan, uniformly over the whole stroma on Day 6 through 2 days after hatching. Furthermore, the chondroitin sulfate proteoglycan was not detected in the epithelial layer on Day 13 and after. These results show that keratan sulfate proteoglycan is synthesized by the stromal cells which invade the primary stroma between Day 5.5 and 6, while chondroitin sulfate proteoglycan is synthesized by epithelial and/or endothelial cells before the invasion, and also by the stromal cells after the invasion.

Complement resistance of tumor cells: basal and induced mechanisms

Clinical and experimental studies have suggested that complement may play a role in tumor cytotoxicity. However, the efficiency of complement-mediated tumor cell lysis is hampered by various protective mechanisms, which may be divided into two categories: basal and induced mechanisms. The basal mechanisms are spontaneously expressed in cells without a need for prior activation, whereas the induced mechanisms develop in cells subjected to stimulation with cytokines, hormones, drugs or with sublytic doses of complement and other pore-formers. Membrane-associated complement regulatory proteins, such as CD55 (DAF, Decay-Accelerating Factor), CD46 (MCP, Membrane Cofactor Protein), CD35 (CR1, Complement Receptor type 1) and CD59, which serve as an important mechanism of self protection and render autologous cells insensitive to the action of complement. appear to be over-expressed on certain tumors. Furthermore, tumor cells secrete several soluble complement inhibitors. Tumor cells may also express proteases that degrade complement proteins, such as C3, or ecto-protein kinases which can phosphorylate complement components, such as C9. Besides this basal resistance, nucleated cells resist, to some extent, complement damage by removing the membrane attack complexes (MAC) from their surface. Several biochemical pathways, including protein phosphorylation, activation of G-proteins and turnover of phosphoinositides have been implicated in resistance to complement. Calcium ion influx and activation of protein kinase C (PKC) and of mitogen-activated protein kinase (MAPK) have also been demonstrated to be associated with the complement-induced enhanced resistance to lysis. The complete elucidation of the molecular mechanisms involved in basal and induced tumor cell resistance will enable the development of strategies for interfering with these evasion mechanisms and the use of the cytotoxic complement system against tumor cells.

Involvement of sulfated proteoglycans in embryonic brain expansion at earliest stages of development in rat embryos

The expansive force generated by the positive pressure of the neural tube fluid confined inside the brain vesicles has been shown to be a key factor during the earliest stages of brain morphogenesis and development of chick embryos. In a previous study, we demonstrated the existence of an intracavity extracellular matrix rich in condroitin sulfate in this species, which could be involved in the regulation of the expansive process. In this report, scanning electron microscopy and immunohistochemistry show that, after neurulation, a similar extracellular matrix rich in chondroitin sulfate is present inside the brain vesicles of rat embryos during early enlargement of the brain anlage. In vitro treatment of rat embryos with beta-D-xyloside (a chemical compound which disrupts chondroitin sulfate synthesis) shows that changes in intralumen chondroitin sulfate concentration are accompanied by significant changes in brain anlage growth. These results support the hypothesis that intracerebral chondroitin sulfate plays a relevant role in the regulation of the expansive process of the brain anlage of rat embryos, and could represent a general mechanism in the early brain development of avian and mammalian embryos.