An α-d-Galactosyl-binding Lectin from Bandeirae simplicifolia Seeds

Isolectin B4 (IB4)-conjugated streptavidin for the selective knockdown of proteins in IB4-positive (+) nociceptors

In vivo analysis of protein function in nociceptor subpopulations using antisense oligonucleotides and short interfering RNAs is limited by their non-selective cellular uptake. To address the need for selective transfection methods, we covalently linked isolectin B4 (IB4) to streptavidin and analyzed whether it could be used to study protein function in IB4(+)-nociceptors. Rats treated intrathecally with IB4-conjugated streptavidin complexed with biotinylated antisense oligonucleotides for protein kinase C epsilon (PKCε) mRNA were found to have: a) less PKCε in dorsal root ganglia (DRG), b) reduced PKCε expression in IB4(+) but not IB4(-) DRG neurons, and c) fewer transcripts of the PKCε gene in the DRG. This knockdown in PKCε expression in IB4(+) DRG neurons is sufficient to reverse hyperalgesic priming, a rodent model of chronic pain that is dependent on PKCε in IB4(+)-nociceptors. These results establish that IB4-streptavidin can be used to study protein function in a defined subpopulation of nociceptive C-fiber afferents.

Isolectin B4 (IB4)-conjugated streptavidin for the selective knockdown of proteins in IB4-positive (+) nociceptors

In vivo analysis of protein function in nociceptor subpopulations using antisense oligonucleotides and short interfering RNAs is limited by their non-selective cellular uptake. To address the need for selective transfection methods, we covalently linked isolectin B4 (IB4) to streptavidin and analyzed whether it could be used to study protein function in IB4(+)-nociceptors. Rats treated intrathecally with IB4-conjugated streptavidin complexed with biotinylated antisense oligonucleotides for protein kinase C epsilon (PKCε) mRNA were found to have: (a) less PKCε in dorsal root ganglia (DRG), (b) reduced PKCε expression in IB4(+) but not IB4(-) DRG neurons, and (c) fewer transcripts of the PKCε gene in the DRG. This knockdown in PKCε expression in IB4(+) DRG neurons is sufficient to reverse hyperalgesic priming, a rodent model of chronic pain that is dependent on PKCε in IB4(+)-nociceptors. These results establish that IB4-streptavidin can be used to study protein function in a defined subpopulation of nociceptive C-fiber afferents.

Characterization of sheep erythrocyte glycosphingolipids recognized by human anti-Forssman antibodies

The FORS histo-blood group system is the most recently discovered carbohydrate-based human blood group system. FORS is a rare blood group system, and most individuals have naturally occurring anti-FORS1 antibodies in plasma. Screening for anti-FORS1 antibodies is often done by hemagglutination assays using FORS1-expressing sheep erythrocytes, since FORS1-positive human erythrocytes are most often not available. Here, we have characterized the non-acid glycosphingolipids from sheep erythrocytes and isolated subfractions, with mass spectrometry, binding of antibodies and lectins, and by enzymatic hydrolysis. This demonstrated the presence of Forssman and Galili pentaosylceramides, and a Galili heptaosylceramide. Two complex glycosphingolipids recognized by human anti-FORS1 antibodies were characterized as a Forssman neolacto hybrid hexaosylceramide (GalNAcα3GalNAcβ3Galβ4GlcNAcβ3Galβ4Glcβ1Cer) and a Forssman Galili hybrid heptaosylceramide (GalNAcα3GalNAcβ3Galα3Galβ4GlcNAcβ3Galβ4Glcβ1Cer). These are novel glycosphingolipid structures, and to our knowledge, the first case of an elongated Galili antigen. Thus, the anti-Forssman antibodies in human serum bind not only to the classical Forssman pentaosylceramide (GalNAcα3GalNAcβ3Galα4Galβ4Glcβ1Cer), but also when the GalNAcα3GalNAcβ3 sequence is presented on a neolacto core chain and even on a Galili carbohydrate sequence.

Plant lectins and their usage in preparing targeted nanovaccines for cancer immunotherapy

Plant lectins, a natural source of glycans with a therapeutic potential may lead to the discovery of new targeted therapies. Glycans extracted from plant lectins are known to act as ligands for C-type lectin receptors (CLRs) that are primarily present on immune cells. Plant-derived glycosylated lectins offer diversity in their N-linked oligosaccharide structures that can serve as a unique source of homogenous and heterogenous glycans. Among the plant lectins-derived glycan motifs, Man₉GlcNAc₂Asn exhibits high-affinity interactions with CLRs that may resemble glycan motifs of pathogens. Thus, such glycan domains when presented along with antigens complexed with a nanocarrier of choice may bewilder the immune cells and direct antigen cross-presentation - a cytotoxic T lymphocyte immune response mediated by CD8⁺ T cells. Glycan structure analysis has attracted considerable interest as glycans are looked upon as better therapeutic alternatives than monoclonal antibodies due to their cost-effectiveness, reduced toxicity and side effects, and high specificity. Furthermore, this approach will be useful to understand whether the multivalent glycan presentation on the surface of nanocarriers can overcome the low-affinity lectin-ligand interaction and thereby modulation of CLR-dependent immune response. Besides this, understanding how the heterogeneity of glycan structure impacts the antigen cross-presentation is pivotal to develop alternative targeted therapies. In the present review, we discuss the findings on structural analysis of glycans from natural lectins performed using GlycanBuilder2 - a software tool based on a thorough literature review of natural lectins. Additionally, we discuss how multiple parameters like the orientation of glycan ligands, ligand density, simultaneous targeting of multiple CLRs and design of antigen delivery nanocarriers may influence the CLR targeting efficacy. Integrating this information will eventually set the ground for new generation immunotherapeutic vaccine design for the treatment of various human malignancies.

Advances in Tools to Determine the Glycan-Binding Specificities of Lectins and Antibodies

Proteins that bind carbohydrate structures can serve as tools to quantify or localize specific glycans in biological specimens. Such proteins, including lectins and glycan-binding antibodies, are particularly valuable if accurate information is available about the glycans that a protein binds. Glycan arrays have been transformational for uncovering rich information about the nuances and complexities of glycan-binding specificity. A challenge, however, has been the analysis of the data. Because protein-glycan interactions are so complex, simplistic modes of analyzing the data and describing glycan-binding specificities have proven inadequate in many cases. This review surveys the methods for handling high-content data on protein-glycan interactions. We contrast the approaches that have been demonstrated and provide an overview of the resources that are available. We also give an outlook on the promising experimental technologies for generating new insights into protein-glycan interactions, as well as a perspective on the limitations that currently face the field.

Inclusion of homologous DNA in nuclease-mediated gene targeting facilitates a higher incidence of bi-allelically modified cells

BACKGROUND

Recent advancements in gene editing techniques have increased in number and utility. These techniques are an attractive alternative to conventional gene targeting methods via homologous recombination due to the ease of use and the high efficiency of gene editing. We have previously produced cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH) knockout (KO) pigs in a Minnesota miniature pig genetic background. These pigs were generated using zinc-finger nucleases (ZFNs) in combination with donor DNA containing a total homology length of 1600 bp (800-bp homology on each arm). Our next aim was to introduce the targeted disruption of alpha-1,3-galactosyltransferase (GGTA1) in the CMAH KO genetic background and evaluate the effect of donor DNA homology length on meganuclease-mediated gene targeting.

METHODS

Zinc-finger nucleases from a previous CMAH KO experiment were used as a proof of concept to identify a correlation between the length of donor DNA homology and targeting efficiency. Based on those results, experiments were designed to use transcription activator-like effector nucleases (TALENs) to generate bi-allelically modified GGTA1 cells using donor DNAs carrying various lengths of homology. Donor DNA was designed to symmetrically flank the predicted cleavage sites in CMAH and GGTA1 for both ZFN and TALEN cleavage sites, respectively. For both genes, the length of total homology ranged from 60 to 1799 bp. Sialyltransferase gene expression profiles were evaluated in CMAH and GGTA1 double KO pig cells and were compared to wild-type and CMAH KO cells.

RESULTS

Introduction of donor DNA with ZFNs demonstrated that small amounts of homology (60 bp) could facilitate homology-directed repair during ZFN-mediated targeting of CMAH; however, donor DNA with longer amounts of homology resulted in a higher frequency of homology-directed repair. For the GGTA1 KO experiments that used TALENs and donor DNA, donor DNA alone did not result in detectable bi-allelic conversion of GGTA1. As the length of donor DNA increased, the bi-allelic disruption of GGTA1 increased from 0.5% (TALENs alone, no donor DNA present) to a maximum of 3% (TALENs and donor DNA with total homology of 1799 bp). Inclusion of homologous donor DNA in TALEN-mediated gene targeting facilitated a higher incidence of bi-allelically modified cells. Using the generated cells, we were able to demonstrate the lack of GGTA1 expression and the decrease in gene expression sialyltransferase-related genes.

CONCLUSIONS

The approach of using donor DNA in conjunction with a meganuclease can be used to increase the efficiency of gene targeting. The gene editing methods can be applied to other genes as well as other mammalian systems. Additionally, gene expression analysis further confirms that the CMAH/GGTA1 double KO pigs can be a valuable source for the study of pig-to-human xenotransplantation.

Purification and partial characterization of a ribosome-inactivating protein from the latex of Euphorbia trigona Miller with cytotoxic activity toward human cancer cell lines

BACKGROUND

The objective of this study is to investigate the cytotoxic activity of three isolectins purified from the latex of Euphorbia trigona Miller.

HYPOTHESIS

Among lectins are the ribosome-inactivating proteins (RIPs), which are potent inhibitors of protein synthesis in cells and in cell-free systems.

RESULTS

Three isolectins, ETR1, ETR2 and ETR3, were purified by anion exchange chromatography. Both ETR1 and ETR3 yielded a single band on SDS-PAGE under reducing conditions, corresponding to a molecular weight of 32 g mol(-1), while ETR2 yielded two bands corresponding to 31 and 33 g mol(-1). When non-reducing conditions were used molecular weight decreased, indicating the presence of intrachain disulfide bonds. Size-exclusion chromatography revealed proteins of apparent molecular weight of 59-63 g mol(-1), suggesting a dimeric nature, with subunits not being held together by disulfide linkage. ETR1, ETR2 and ETR3 hemagglutinated human, sheep and rat erythrocytes and this hemagglutination was specifically inhibited by galactose and its derivatives. The lectins studied were thermostable up to 60 °C and their observed activity was maintained across pH range 5-12. These lectins, from the latex of Euphorbia trigona, are potent inhibitors of eukaryotic protein synthesis in a cell-free system. Flow cytometry analysis revealed the antiproliferative activity of them toward A549, HeLa, H116, HL-60 cell lines.

CONCLUSION

Euphorbia trigona isolectins are RIPs with cytotoxic activity toward human cancer cell lines.

Neuronally produced versican V2 renders C-fiber nociceptors IB4 -positive

A subpopulation of nociceptors, the glial cell line-derived neurotrophic factor (GDNF)-dependent, non-peptidergic C-fibers, expresses a cell-surface glycoconjugate that can be selectively labeled with isolectin B4 (IB4 ), a homotetrameric plant lectin from Griffonia simplicifolia. We show that versican is an IB4 -binding molecule in rat dorsal root ganglion neurons. Using reverse transcriptase polymerase chain reaction (RT-PCR), in situ hybridization and immunofluorescence experiments on rat lumbar dorsal root ganglion, we provide the first demonstration that versican is produced by neurons. In addition, by probing Western blots with splice variant-specific antibodies we show that the IB4 -binding versican contains only the glycosaminoglycan alpha domain. Our data support V2 as the versican isoform that renders this subpopulation of nociceptors IB4 -positive (+). A subset of nociceptors, the GDNF-dependent non-peptidergic C-fibers can be characterized by its reactivity for isolectin B4 (IB4), a plant lectin from Griffonia simplicifolia. We have previously demonstrated that versican V2 binds IB4 in a Ca2 + -dependent manner. However, given that versican is thought to be the product of glial cells, it was questionable whether versican V2 can be accountable for the IB4-reactivity of this subset of nociceptors. The results presented here prove - for the first time - a neuronal origin of versican and suggest that versican V2 is the molecule that renders GDNF-dependent non-peptidergic C-fibers IB4-positive.

Automatic quantification of angiogenesis in 2D sections: a precise and timesaving approach

INTRODUCTION

The standardized characterization of angiogenesis is crucial in the field of tissue engineering as sufficient blood supply is the limiting factor of mass transfer. However, reliable algorithms that provide a straight forward and observer-independent assessment of new vessel formation are still lacking. We propose an automatic observer-independent quantitative method (including downloadable source code) to analyze vascularization using two-dimensional microscopic images of histological cross-sections and advanced postprocessing, based on a 'positive- and negative-experts' model and a (corrected) nearest neighbour classification, in a vascularized tissue engineering model.

MATERIALS AND METHODS

An established angioinductive rat arteriovenous loop model was used to compare the new automatic analysis with a common 2D method and a μCT algorithm. Angiogenesis was observed at three different time points (5, 10 and 15 days).

RESULTS

In line with previous results, formation of functional new vessels that arose from the venous graft was evident within the three-dimensional construct and a significant (p < 0.05) increase in vessel count and area was observed over time. The proposed automatic analysis obtained precise values for vessel count and vessel area that were similar to the manually gained data. The algorithm further provided vectorized parameterization of the newly formed vessels for advanced statistical analysis. Compared to the μCT-based three-dimensional analyses, the presented two-dimensional algorithm was superior in terms of small vessel detection as well as cost and time efficiency.

CONCLUSIONS

The quantitative evaluation method, using microscopic images of stained histological sections, 'positive- and negative-experts'-based vessel segmentation, and nearest neighbour classification, provides a user-independent and precise but also time- and cost-effective tool for the analysis of vascularized constructs. Our algorithm, which is freely available to the public, outperforms previous approaches especially in terms of unambiguous vessel classification and statistical analyses.

Structural analysis and binding properties of isoforms of tarin, the GNA-related lectin from Colocasia esculenta

The lectins, a class of proteins that occur widely in animals, plants, fungi, lichens and microorganisms, are known for their ability to specifically bind to carbohydrates. Plant lectins can be classified into 12 families including the Galanthus nivalis agglutinin (GNA)-related lectin superfamily, which is widespread among monocotyledonous plants and binds specifically to mannose, a behavior that confers remarkable anti-tumor, anti-viral and insecticidal properties on these proteins. The present study characterized a mitogenic lectin from this family, called tarin, which was purified from the crude extract from taro (Colocasia esculenta). The results showed that tarin is a glycoprotein with 2-3% carbohydrate content, composed of least 10 isoforms with pIs ranging from 5.5 to 9.5. The intact protein is a heterotetramer of 47kDa composed of two non-identical and non-covalently associated polypeptides, with small subunits of 11.9kDa and large subunits of 12.6kDa. The tarin structure is stable and recovers or maintains its functional structure following treatments at different temperatures and pH. Tarin showed a complex carbohydrate specificity, binding with high affinity to high-mannose and complex N-glycans. Many of these ligands can be found in viruses, tumor cells and insects, as well as in hematopoietic progenitor cells. Chemical modifications confirmed that both conserved and non-conserved amino acids participate in this interaction. This study determined the structural and ligand binding characteristics of a GNA-related lectin that can be exploited for several different purposes, particularly as a proliferative therapeutic molecule that is able to enhance the immunological response.

PNA-encoded synthesis (PES) of a 10 000-member hetero-glycoconjugate library and microarray analysis of diverse lectins

Identification of selective and synthetically tractable ligands to glycan-binding proteins is important in glycoscience. Carbohydrate arrays have had a tremendous impact on profiling glycan-binding proteins and as analytical tools. We report a highly miniaturized synthetic format to access nucleic-acid-encoded hetero-glycoconjugate libraries with an unprecedented diversity in the combinations of glycans, linkers, and capping groups. Novel information about plant and bacterial lectin specificity was obtained by microarray profiling, and we show that a ligand identified on the array can be converted to a high-affinity soluble ligand by straightforward chemistry.

Hsp70-Hsp40 chaperone complex functions in controlling polarized growth by repressing Hsf1-driven heat stress-associated transcription

How the molecular mechanisms of stress response are integrated at the cellular level remains obscure. Here we show that the cellular polarity machinery in the fission yeast Schizosaccharomyces pombe undergoes dynamic adaptation to thermal stress resulting in a period of decreased Cdc42 activity and altered, monopolar growth. Cells where the heat stress-associated transcription was genetically upregulated exhibit similar growth patterning in the absence of temperature insults. We identify the Ssa2-Mas5/Hsp70-Hsp40 chaperone complex as repressor of the heat shock transcription factor Hsf1. Cells lacking this chaperone activity constitutively activate the heat-stress-associated transcriptional program. Interestingly, they also exhibit intermittent monopolar growth within a physiological temperature range and are unable to adapt to heat stress. We propose that by negatively regulating the heat stress-associated transcription, the Ssa2-Mas5 chaperone system could optimize cellular growth under different temperature regiments.

Heat stress, caused by fluctuations in ambient temperature, occurs frequently in nature. How organisms adapt and maintain regular patterns of growth over a range of environmental conditions remain poorly understood. Our work in the simple unicellular yeast Schizosaccharomyces pombe suggests that the heat stress-associated transcription must be repressed by the evolutionary conserved Hsp70-Hsp40 chaperone complex to allow cells to adapt the polarized growth machinery to elevated temperature.

Composition of fibrin glues significantly influences axial vascularization and degradation in isolation chamber model

In this study, different fibrin sealants with varying concentrations of the fibrin components were evaluated in terms of matrix degradation and vascularization in the arteriovenous loop (AVL) model of the rat. An AVL was placed in a Teflon isolation chamber filled with 500 μl fibrin gel. The matrix was composed of commercially available fibrin gels, namely Beriplast (Behring GmbH, Marburg, Germany) (group A), Evicel (Omrix Biopharmaceuticals S.A., Somerville, New Jersey, USA) (group B), Tisseel VH S/D (Baxter, Vienna, Austria) with a thrombin concentration of 4 IU/ml and a fibrinogen concentration of 80 mg/ml [Tisseel S F80 (Baxter), group C] and with an fibrinogen concentration of 20 mg/ml [Tisseel S F20 (Baxter), group D]. After 2 and 4 weeks, five constructs per group and time point were investigated using micro-computed tomography, and histological and morphometrical analysis techniques. The aprotinin, factor XIII and thrombin concentration did not affect the degree of clot degradation. An inverse relationship was found between fibrin matrix degradation and sprouting of blood vessels. By reducing the fibrinogen concentration in group D, a significantly decreased construct weight and an increased generation of vascularized connective tissue were detected. There was an inverse relationship between matrix degradation and vascularization detectable. Fibrinogen as the major matrix component showed a significant impact on the matrix properties. Alteration of fibrin gel properties might optimize formation of blood vessels.

Magnetic glyco-nanoparticles: a tool to detect, differentiate, and unlock the glyco-codes of cancer via magnetic resonance imaging

Within cancer, there is a large wealth of diversity, complexity, and information that nature has engineered rendering it challenging to identify reliable detection methods. Therefore, the development of simple and effective techniques to delineate the fine characteristics of cancer cells can have great potential impacts on cancer diagnosis and treatment. Herein, we report a magnetic glyco-nanoparticle (MGNP) based nanosensor system bearing carbohydrates as the ligands, not only to detect and differentiate cancer cells but also to quantitatively profile their carbohydrate binding abilities by magnetic resonance imaging (MRI). Using an array of MGNPs, a range of cells including closely related isogenic tumor cells, cells with different metastatic potential and malignant vs normal cells can be readily distinguished based on their respective "MRI signatures". Furthermore, the information obtained from such studies helped guide the establishment of strongly binding MGNPs as antiadhesive agents against tumors. As the interactions between glyco-conjugates and endogenous lectins present on cancer cell surface are crucial for cancer development and metastasis, the ability to characterize and unlock the glyco-code of individual cell lines can facilitate both the understanding of the roles of carbohydrates as well as the expansion of diagnostic and therapeutic tools for cancer.

Prenatal stress alters microglial development and distribution in postnatal rat brain

Stress affects microglial function and viability during adulthood and early postnatal life; however, it is unknown whether stress to the pregnant dam might alter offspring microglia. The effects of prenatal stress on microglial development and distribution in the postnatal brain were studied using Wistar rats. Prenatal stress consisting of 20 min of forced swimming occurred on embryonic days 10-20. On postnatal days 1 and 10, stressed and control pups were killed. Microglia were identified using Griffonia simplicifolia lectin and quantified in the whole encephalon. In addition, plasma corticosterone was measured in dams at embryonic day 20, and in pups on postnatal days 1 and 10. At postnatal day 1, there was an increase in number of ramified microglia in the parietal, entorhinal and frontal cortices, septum, basal ganglia, thalamus, medulla oblongata and internal capsule in the stressed pups as compared to controls, but also there was a reduction of amoeboid microglia and the total number of microglia in the corpus callosum. By postnatal day 10, there were no differences in the morphologic type or the distribution of microglia between the prenatal stress and control groups, except in the corpus callosum; where prenatal stress decreased the number of ramified microglia. The stress procedure was effective in producing plasma rise in corticosterone levels of pregnant rats at embryonic day 20 when compared to same age controls. Prenatal stress reduced the number of immature microglia and promoted an accelerated microglial differentiation into a ramified form. These findings may be related to an increase in plasma corticosterone in the pregnant dam.

Dose-finding study of fibrin gel-immobilized vascular endothelial growth factor 165 and basic fibroblast growth factor in the arteriovenous loop rat model

The angiogenic effects of different concentrations of vascular endothelial growth factor (VEGF) 165 and basic fibroblast growth factor (bFGF) immobilized in a fibrin-based drug-delivery system were quantitatively assessed in the arteriovenous (AV) loop model. An AV loop was created in the medial thigh of 60 rats. The loop was placed in a Teflon isolation chamber and embedded in 500 microL of fibrin gel loaded with VEGF and bFGF in four different concentrations (no growth factor, 100 ng/mL of VEGF, 25 ng/mL of VEGF and bFGF, 100 ng/mL pf VEGF and bFGF). The explantation intervals were 1, 2, and 4 weeks after the initial operation for all groups. Specimens were investigated using (micro-CT) and histological and morphometrical techniques. After 2 weeks, the cross-section area and construct weight were significantly lower with the use of 100 ng/mL of VEGF and bFGF. Micro-CT and histology showed significantly greater vascular density and number of vessels of the constructs at 2 and 4 weeks when 100 ng/mL of VEGF165 and bFGF were applied than in the growth factor-free specimens. The angioinductive effects were dose-dependent, with best results when using 100 ng/mL of VEGF165 and bFGF. The greater tissue formation was accompanied by faster resorption of the fibrin matrix.

Measurement of monovalent and polyvalent carbohydrate-lectin binding by back-scattering interferometry

Carbohydrate-protein binding is important to many areas of biochemistry. Here, backscattering interferometry (BSI) has been shown to be a convenient and sensitive method for obtaining quantitative information about the strengths and selectivities of such interactions. The surfaces of glass microfluidic channels were covalently modified with extravidin, to which biotinylated lectins were subsequently attached by incubation and washing. The binding of unmodified carbohydrates to the resulting avidin-immobilized lectins was monitored by BSI. Dose-response curves that were generated within several minutes and were highly reproducible in multiple wash/measure cycles provided adsorption coefficients that showed mannose to bind to concanavalin A (conA) with 3.7 times greater affinity than glucose consistent with literature values. Galactose was observed to bind selectively and with similar affinity to the lectin BS-1. The avidities of polyvalent sugar-coated virus particles for immobilized conA were much higher than monovalent glycans, with increases of 60-200 fold per glycan when arrayed on the exterior surface of cowpea mosaic virus or bacteriophage Qbeta. Sugar-functionalized PAMAM dendrimers showed size-dependent adsorption, which was consistent with the expected density of lectins on the surface. The sensitivity of BSI matches or exceeds that of surface plasmon resonance and quartz crystal microbalance techniques, and is sensitive to the number of binding events, rather than changes in mass. The operational simplicity and generality of BSI, along with the near-native conditions under which the target binding proteins are immobilized, make BSI an attractive method for the quantitative characterization of the binding functions of lectins and other proteins.

Griffonia simplicifolia isolectin B4 identifies a specific subpopulation of angiogenic blood vessels following contusive spinal cord injury in the adult mouse

After traumatic spinal cord injury (SCI), disruption and plasticity of the microvasculature within injured spinal tissue contribute to the pathological cascades associated with the evolution of both primary and secondary injury. Conversely, preserved vascular function most likely results in tissue sparing and subsequent functional recovery. It has been difficult to identify subclasses of damaged or regenerating blood vessels at the cellular level. Here, adult mice received a single intravenous injection of the Griffonia simplicifolia isolectin B4 (IB4) at 1-28 days following a moderate thoracic (T9) contusion. Vascular binding of IB4 was maximally observed 7 days following injury, a time associated with multiple pathologic aspects of the intrinsic adaptive angiogenesis, with numbers of IB4 vascular profiles decreasing by 21 days postinjury. Quantitative assessment of IB4 binding shows that it occurs within the evolving lesion epicenter, with affected vessels expressing a temporally specific dysfunctional tight junctional phenotype as assessed by occludin, claudin-5, and ZO-1 immunoreactivities. Taken together, these results demonstrate that intravascular lectin delivery following SCI is a useful approach not only for observing the functional status of neovascular formation but also for definitively identifying specific subpopulations of reactive spinal microvascular elements.

Development of a new mouse model of branch retinal vein occlusion and retinal neovascularization

PURPOSE

Retinal neovascularization (NV) is associated with various disorders, such as retinal vein occlusion, diabetic retinopathy, and retinopathy of prematurity, and often causes severe loss of vision. To determine the mechanism of retinal NV and develop new therapy, we developed a mouse model using a photodynamic method.

METHODS

C57BL/6 mice were injected with rose bengal via the tail vein, and then selected venous points were photocoagulated.

RESULTS

All eyes demonstrated venous occlusion on day 1, and capillary nonperfusion areas were observed until day 3. Twenty of 33 eyes (60.6%) developed retinal NV on day 14, confirmed by fluorescein isothiocyanate-perfused retinal flat-mounts and immunochemical and histopathological analyses. Reverse transcriptase-polymerase chain reaction showed an increase in the expression of vascular endothelial growth factor at the retina on day 7.

CONCLUSIONS

Because of the simplicity, low cost, and feasibility of genetic manipulations, our model is believed to represent an advance in investigating molecular mechanisms and establishing therapy for retinal NV.

Capsaicin, transient receptor potential (TRP) protein subfamilies and the particular relationship between capsaicin receptors and small primary sensory neurons

A number of subfamilies of the capsaicin receptor, collectively called TRP, have been reported since the discovery of vanilloid receptor 1 (VR1). The term 'TRP' is derived from 'transient receptor potential', which means the transient and rapid defect of reaction following long stimulation with light in the photoreceptor cells of mutant Drosophila. The common features of TRP family members are the centrally situated six transmembrane domain, in which an ion channel is located, three to four ankirin repeats at the N-terminus and a TRP domain comprising 25 amino acids at the C-terminus. The TRP family members are present in animals, including invertebrates and vertebrates, and in the cells in various tissues in individual animals. During evolution, the original TRP seems to have acquired a wide variety of functions related to sensing the inner or outer environment (e.g. to sensing light (Drosophila), osmolarity, protons, temperature, ligands and mechanical force). In mammals, the TRPV subfamily is exclusively expressed in small- to medium-sized primary sensory neurons that also co-express some chemical markers (i.e. isolectin B4 (IB4), fluoride-resistant acid phosphatase (FRAP), the P2X3 purinoceptor (a receptor provoked by ATP-induced nociception) and Ret, a glial cell line-derived neurotrophic factor receptor). There is a paradox in that regardless of the marked or complete loss of noxious, small sensory neurons (polymodal nociceptors) in mice treated with capsaicin during the neonatal period, as well as in VR1 (TRPV1)-deficient knock-out mice, the responses to noxious heat are normal. Regarding the paradox in mice treated with capsaicin as neonates, our explanation is that although capsaicin probably reduces the number of a subgroup of small neurons (IB4-, VR1+), the remaining IB4+ (VR1-) neurons can sense noxious heat normally. One working hypothesis is that mice lacking TRPV1/2 can sense noxious heat under normal conditions, presumably via another still unknown pathway, and TRPV1 has been suggested to be involved in noxious heat transduction under pathological conditions, such as inflammation and tissue injury. Further studies will be required to clarify these complexities. Mice treated with capsaicin as neonates would provide a model to investigate the above paradoxes, as would TRPV1-knock-out mice, although different mechanisms may be operating in the two models.

Purification and characterization of an N-acetyl-D-galactosamine-specific lectin from seeds of chickpea (Cicer arietinum L.)

A novel lectin (CAA-II) was isolated and purified from the seeds of Cicer arietinum by ammonium sulphate fractionation and affinity chromatography on an N-acetyl-D-galactosamine-linked agarose column. The lectin is composed of four identical subunits of 30 kDa and the molecular mass of the native lectin was estimated to be 120 kDa by gel filtration chromatography and confirmed by mass spectrometry. The lectin showed agglutination activity against rabbit erythrocytes (trypsin-treated and untreated) as well as against human erythrocytes. Haemagglutination inhibition assays showed that the lectin is a galactose-specific protein having a high affinity for N-acetyl-D-galactosamine. The molecular weight, haemagglutination pattern, carbohydrate specificity and N-terminal amino acid sequence indicated that the lectin is clearly distinct from the previously reported chickpea lectin CAA-I.

The galactophilic lectin (PA-IL, gene LecA) from Pseudomonas aeruginosa. Its binding requirements and the localization of lectin receptors in various mouse tissues

The opportunistic pathogen Pseudomonas aeruginosa contains lectins of which one of them, PA-IL (gene lecA), shows preference for alpha-galactosylated glycans. The bacterial lectin is probably important in the carbohydrate-mediated adhesion of the microorganism to endothelia and epithelia and thereby the lectin facilitates entering and damaging of the cells. The requirements for the interaction between PA-IL and the carbohydrate epitopes to which the bacterial lectin may bind were here studied using alpha-galactosylated neoglycoproteins that were immobilized on Microtiter plates. It is concluded that the carbohydrate recognizing site of the lectin can have a binding requirement of only one saccharide. Lectin histochemistry was performed on sections from wild type mice and from knock-out mice, which lack function of the alpha1,3-galactosyltransferase gene. All assays with the P. aeruginosa lectin were compared with the results obtained using an isolectin from the legume shrub Griffonia simplicifolia: the GSI-B4 isolectin, which is highly specific for glycans terminating in Galalpha1-R. In the wild-type mice, lectin histochemistry showed a strong capillary reaction in heart, kidney and adrenal gland while none of the two lectins were able to detect capillaries in the pancreas. This could indicate a differential glycosylation with respect to endothelial cell Galalpha epitopes among different organs. Further, since no PA-IL binding to the endothelial cells in the KO mouse was observed, it seems that, in the mouse, the Pseudomonas lectin adheres to the Galalpha1-3Galbeta1-4GlcNAc carbohydrate on endothelial cells in most organs and tissues. Finally, lectin staining of the basement membrane of the acini in the exocrine pancreas suggests the presence of Galalpha1-3Gal epitopes in WT mice basement membranes that are not detected by the P. aeruginosa lectin.

Coffee carbohydrates

This review summarises recent advances in the chemistry, physiology and molecular properties of coffee carbohydrates with a particular focus on the cell wall polysaccharides. The results of detailed chemical studies have demonstrated novel structural features of both the galactomannans and the arabinogalactan polysaccharides of the green and roasted coffee bean. For the first time immunological probes based on monoclonal antibodies for specific polysaccharide epitopes were used to reveal the patterns of distribution of the galactomannans, arabinogalactans and pectic polysaccharides in the coffee bean cell wall. Finally, the results of physiological and molecular studies are presented which emphasise the growing awareness of the potential role the metabolic status of the green bean may play in final coffee beverage quality.

Clinical significance of T1-weighted MR images following transient cerebral ischemia

To try to determine the cause of hyperintensity of T1-weighted MR images that occurred on and after day 7 following transient cerebral ischemia, dynamic changes in T1-weighted images and histology of rats subjected to 20 min of 4-vessel occlusion were observed. T1-weighted images showed no remarkable alteration on days 1 and 3, although high signal intensity in the striatal region, in which the T1 value was significantly lower than the values on days 1 and 3, was observed on day 7. High signal intensity in T1-weighted images indicates low T1 values. Histological observation revealed accumulation of microglia in the striatal region on day 7 by lectin staining. There was a tight correlation between T1 values and number of lectin-positive cells. Microglia had stout processes and hypertrophic cell bodies on day 7, resembling lipid-laden phagocytes. Sudan black B staining showed the presence of many fatty droplets in the striatal region on day 7. Furthermore, double staining with lectin and Sudan black B revealed the presence of fatty droplets in bodies of lectin-positive cells on day 7. These results suggest that hyperintensity of T1-weighted images on day 7 following transient ischemia and reperfusion indicates accumulation and phagocytic activation of microglia. T1-weighted images seem to represent the progression of non-reversible tissue injury after transient ischemia and reperfusion.

A tuber lectin from Arisaema helleborifolium Schott with anti-insect activity against melon fruit fly, Bactrocera cucurbitae (Coquillett) and anti-cancer effect on human cancer cell lines

An anti-insect and anti-cancer lectin has been isolated from Arisaema helleborifolium Schott by affinity chromatography using asialofetuin-linked amino activated silica beads. The bound A. helleborifolium lectin (AHL) was eluted with 100mM glycine-HCl buffer, pH 2.5. It gave a single band on SDS-PAGE, pH 8.3, and PAGE, pH 4.5. However, multiple bands were obtained in PAGE at pH 8.3 and isoelectric focusing. The lectin was a homotetramer having subunit molecular mass 13.4kDa while its native molecular mass was 52kDa. It was a glycoprotein with 3.40% carbohydrate and was stable up to 60 degrees C for 30min. It showed anti-insect activity towards second instar larvae of Bactrocera cucurbitae (Coquillett) with LC(50) value of 16.4microg/ml. Larvae fed on artificial diet containing sub-lethal dose of AHL showed a significant decrease in acid phosphatase and alkaline phosphatase activity while esterase activity markedly increased as compared to larvae fed on diet without lectin. AHL was also found to inhibit in vitro proliferation of some well established human cancer cell lines viz HOP-62 (95%), HCT-15 (92%), HEP-2 (66%), HT-29 (68%), PC-3 (39.4%), and A-549 (20.7%).

Neonatal Porcine Sertoli Cells Inhibit Human Natural Antibody-Mediated Lysis1

Sertoli cells protect cotransplanted cells from allogeneic and xenogeneic rejection. Additionally, neonatal porcine Sertoli cells (NPSCs) survive long-term as xenografts in nonimmunosuppressed rodents. This has led to the hypothesis that NPSCs could be used to prevent cellular rejection in clinical transplantation, thereby eliminating the need for chronic immunosuppression. Prior to transplantation of NPSCs in humans it is necessary to determine whether they are also protected from humoral-mediated xenograft rejection. The presence of Gal alpha(1,3)Gal beta(1,4)GlcNAc-R (alphaGal epitope) as well as binding of human immunoglobulin G (IgG) and IgM to NPSCs was examined by immunocytochemical and fluorescence-activated cell sorter analysis. alphaGal was detected on 88.5% +/- 3.0% of NPSCs. Consistent with this, 71.7% +/- 1.0% and 65.4% +/- 5.2% of NPSCs were bound by IgG and IgM, respectively. When cultured NPSCs underwent an in vitro cytotoxicity assay by incubation with human AB serum plus complement, no increase in cellular lysis was observed, while controls--porcine aorta endothelial cells--were shown to contain > 60% dead cells. Finally, activation of the complement cascade was examined by immunohistochemistry. C3 and C4 were deposited on the surface of the NPSC membrane, indicating activation of complement. Although the complement cascade was activated, the membrane attack complex (MAC) was not formed. These data demonstrate that despite expression of alphaGal, binding of xenoreactive antibodies, and the activation of complement, NPSCs survive human antibody and complement-mediated lysis by preventing MAC formation. This suggests that NPSCs may be able to survive humoral-mediated rejection in a clinical situation.

Endothelial Cells Derived from Pigs Lacking Gal??(1,3)Gal: No Reduction of Human Leukocyte Adhesion and Natural Killer Cell Cytotoxicity

BACKGROUND

The expression of galactose-alpha(1,3)galactose (Gal) on porcine cells represents a major barrier to xenotransplantation. The generation of Gal-/- pigs to overcome this barrier redirected the focus of research to other rejection mechanisms, including cellular immunity. The present in vitro study investigated (1) the adhesive interactions between human leukocyte subsets and primary endothelial cells derived from inbred Gal-/- and Gal+/+ pigs, and (2) the susceptibility of such Gal-/- porcine endothelial cells to human natural killer (NK) cell cytotoxicity.

METHODS

Primary porcine aortic endothelial cells (PAEC) were isolated from Gal-/- (PAEC-Gal-/-) and Gal (PAEC-Gal+/+) pigs. Human peripheral blood mononuclear cells (PBMC), polymorphonuclear neutrophils (PMN), and NK cells were isolated from healthy volunteers and tested in functional adhesion and cytotoxicity assays.

RESULTS

Adhesion of human PBMC, PMN, or purified NK cells on PAEC-Gal-/- cells was not different from that on PAEC-Gal+/+ cells. Comparing the different leukocyte subsets of PBMC, a preferential adhesion of NK and B cells on both PAEC-Gal-/- and PAEC-Gal+/+ was detected. Tumor-necrosis factor-alpha stimulation of PAEC-Gal-/- and PAEC-Gal+/+ induced an increase of CD62E and CD106 expression and increased cellular adhesion, in particular, of PMN. The lack of Gal-/- expression on PAEC-Gal cells did not prevent xenogeneic human NK-cell cytotoxicity mediated by freshly isolated or interleukin-2-activated NK cells.

CONCLUSIONS

Neither human leukocyte adhesion nor xenogeneic NK-cell cytotoxicity against PAEC are impaired by the lack of Gal, indicating that Gal is not a dominant target of cellular rejection.

Identification of versican as an isolectin B4-binding glycoprotein from mammalian spinal cord tissue

Nociceptors are specialized nerve fibers that transmit noxious pain stimuli to the dorsal horn of the spinal cord. A subset of nociceptors, the nonpeptidergic C-fibers, is characterized by its reactivity for the plant isolectin B4 (IB4) from Griffonia simplicifolia. The molecular nature of the IB4-reactive glycoconjugate, although used as a neuroanatomical marker for more than a decade, has remained unknown. We here present data which strongly suggest that a splice variant of the extracellular matrix proteoglycan versican is the IB4-reactive glycoconjugate associated with these nociceptors. We isolated (by subcellular fractionation and IB4 affinity chromatography) a glycoconjugate from porcine spinal cord tissue that migrated in SDS/PAGE as a single distinct protein band at an apparent molecular mass of > 250 kDa. By using MALDI-TOF/TOF MS, we identified this glycoconjugate unambiguously as a V2-like variant of versican. Moreover, we demonstrate that the IB4-reactive glycoconjugate and the versican variant can be co-released from spinal cord membranes by hyaluronidase, and that the IB4-reactive glycoconjugate and the versican variant can be co-precipitated by an anti-versican immunoglobulin and perfectly co-migrate in SDS/PAGE. Our findings shed new light on the role of the extracellular matrix, which is thought to be involved in plastic changes underlying pain-related phenomena such as hyperalgesia and allodynia.

Application of antibodies for the identification of polysaccharide gum additives in processed foods

Anti-carbohydrate antibodies with specificities for polysaccharide gums were isolated from the serum of rabbits that were immunized with a solution of the gums and Freund's complete adjuvant. The primary objective was to test an immunological method for the detection of the polysaccharide gums as additives to processed foods. Analysis involved the extraction of food with phosphate buffer and the testing of the extract for a reaction with anti-gum antibodies by the agar diffusion method. Reaction by a specific gum with the homologous antibodies establishes the presence of the gum in the food. The method is a novel application of antibodies. The antibody method is highly specific for a gum and thus possesses advantages over other methods of analysis for polysaccharide gums as additives in processed foods.

Lack of Galactose-α-1,3-Galactose Expression on Porcine Endothelial Cells Prevents Complement-Induced Lysis but Not Direct Xenogeneic NK Cytotoxicity

The galactose-alpha-1,3-galactose (alphaGal) carbohydrate epitope is expressed on porcine, but not human cells, and therefore represents a major target for preformed human anti-pig natural Abs (NAb). Based on results from pig-to-primate animal models, NAb binding to porcine endothelial cells will likely induce complement activation, lysis, and hyperacute rejection in pig-to-human xenotransplantation. Human NK cells may also contribute to innate immune responses against xenografts, either by direct recognition of activating molecules on target cells or by FcgammaRIII-mediated xenogeneic Ab-dependent cellular cytotoxicity (ADCC). The present study addressed the question as to whether the lack of alphaGal protects porcine endothelial cells from NAb/complement-induced lysis, direct xenogeneic NK lysis, NAb-dependent ADCC, and adhesion of human NK cells under shear stress. Homologous recombination, panning, and limiting dilution cloning were used to generate an alphaGal-negative porcine endothelial cell line, PED2*3.51. NAb/complement-induced xenogeneic lysis of PED2*3.51 was reduced by an average of 86% compared with the alphaGal-positive phenotype. PED2*3.51 resisted NK cell-mediated ADCC with a reduction of lysis ranging from 30 to 70%. However, direct xenogeneic lysis of PED2*3.51, mediated either by freshly isolated or IL-2-activated human NK cells or the NK cell line NK92, was not reduced. Furthermore, adhesion of IL-2-activated human NK cells did not rely on alphaGal expression. In conclusion, removal of alphaGal leads to a clear reduction in complement-induced lysis and ADCC, but does not resolve adhesion of NK cells and direct anti-porcine NK cytotoxicity, indicating that alphaGal is not a dominant target for direct human NK cytotoxicity against porcine cells.

Facile preparation of the alpha-Gal-recognizing Griffonia simplicifolia I-B4 isolectin

The B4 isolectin from Griffonia simplicifolia is of great utility as a reagent for the identification of alpha-D-galactopyranosyl end groups. Its separation from isolectins containing A subunits has been greatly improved by a simple, rapid procedure using a column of N-acetylgalactosamine coupled to vinyl sulfone-activated Sepharose 4B to selectively retain the A subunit-containing isolectins. The procedure has the advantages over previous affinity procedures of speed (the isolation of B4 isolectin can be achieved in one day), simplicity, and high degree of resolution of the B4 isolectin.

Presence of Gal-alpha1,3Gal epitope on xenogeneic lines: implications for cellular gene therapy based on the encapsulation technology

Exposure to human serum induces the lysis of xenogeneic cells through natural antibodies and complement activation. The carbohydrate Galactose-alpha1,3-Galactose (Gal-alpha1,3-Gal) epitope, has been shown to be the principal antigenic determinant on target cells. This reaction is, therefore, particularly important for xenogeneic cell-based therapy. As a first step toward the evaluation of the impact of this phenomenon for encapsulated xenogeneic cells, we have evaluated the presence of the Gal-alpha1,3Gal epitope on two cell lines currently being used for the systemic delivery of protein in the periphery or the treatment of neurodegenerative diseases. In the second part of the study, we have tested and compared human serum and cerebrospinal fluid (CSF) for the presence of xenoreactive natural antibodies (XNAs) and their potential impact on the survival of xenogeneic cells. Fluorescence-activated cell sorting analysis indicated that baby hamster kidney (BHK) cells expressed low levels of the alpha-Gal epitope, whereas mouse myoblast C2C12 cells were extensively stained with the specific IB4-lectin. There was a direct correlation between serum killing and the level of Gal-alpha1,3-Gal epitope expression on these cells. Importantly, we showed that CSF did not lyse BHK and C2C12 cells as determined by cytotoxic crossmatch assays. The reaction was specific as the addition of soluble Gal-alpha1,3-Gal sugar to human serum effectively reduced cell killing, and the overproduction of alpha-1,3-galactosyltransferase in BHK cells significantly increased inactivation by human serum. To interfere with this antibody-antigen reaction and develop cell lines particularly suitable for cell-based therapy, we either selected C2C12 clones expressing low levels of Gal-alpha1,3-Gal or high levels of alpha-1,2-fucosyltransferase. These cells were found to be resistant to complement-mediated cytolysis. These strategies may, therefore, protect encapsulated xenogeneic cells transplanted in the periphery or the central nervous system even in an unlikely event of a blood-brain barrier breakage and the post-transplantation development of an antibody response.

Restricted expression of shiga toxin binding sites on mucosal epithelium of mouse distal colon

Shiga toxins (Stx) are some of the major virulence factors of enterohemorrhagic Escherichia coli strains such as serotype O157:H7. To explore how Stx might initially gain access to the bloodstream from sites of infection, frozen sections of mouse colon were immunohistochemically examined for binding sites for recombinant binding subunits (Stx1B). Binding sites were selectively expressed on the epithelium in the distal half of the mouse colon, whereas the proximal half did not exhibit any binding sites. In agreement with this observation, we also demonstrated the distal-part-restricted distribution of glycolipids that bind to Stx1B in the mouse colon. For comparison, the binding sites of several control lectins were also examined. Selective binding to the distal part of the colon was not seen with any other control lectins, including Griffonia simplicifolia lectin-I isolectin B4 (GS-I-B4), which shares alpha-galactose specificity with Stx1B. Partial overlapping of the specificities of Stx1B and GS-I-B4 was seen by assay with globotriose-conjugated multivalent ligands. The results indicate that Stx1B is stricter in the recognition of carbohydrate determinants than GS-I-B4 when examined with biological ligands.

Delayed rejection of porcine cartilage is averted by transgenic expression of alpha1,2-fucosyltransferase

The use of xenogeneic cells or tissues for tissue engineering applications may lead to advances in biomedical research. Hyperacute and delayed rejection are immunologic hurdles that must be addressed to achieve xenograft survival in the pig-to-primate setting. Expression of human alpha1,2-fucosyltransferase (HT) in the donor cell or tissue protects from hyperacute rejection (HAR) by reducing expression of Galalpha1,3-Gal epitope, the major xenoantigen recognized by human natural antibodies. We hypothesized that Galalpha1,3-Gal antigen contributes to delayed tissue rejection. To test this hypothesis, we transplanted control or HT-transgenic engineered porcine cartilage s.c. into alpha1,3-galactosyltransferase knockout (Gal KO) mice. Control porcine cartilage grafted in Gal KO mice was not susceptible to HAR but was rejected in several wk by a prominent cellular immune infiltrate and elevated antibody titers. In contrast, Gal KO mice receiving the HT engineered cartilage showed a markedly reduced anti-pig antibody response and no anti-Galalpha1,3-Gal-elicited antibody response. The HT implants had a mild cellular infiltrate that was confined to the graft periphery. Our study demonstrates that a marked reduction of Galalpha1,3-Gal antigen in HT-transgenic porcine cartilage confers resistance to a process of delayed rejection. Further development of tissue engineering applications that use genetically modified porcine tissues is encouraged.

Altered microvasculature is involved in remodeling processes in cardiomyopathic hamsters

The cardiomyopathic hamster (BIO TO2) is a well-established model of heart failure. Deterioration of cardiac function in BIO TO2 is attributed to a defect in delta-sarcoglycan, whereas cardiac dysfunction in delta-sarcoglycan knockout mice is caused by microvascular abnormalities. We examined the relation between cardiac function and the microvasculature, including angiogenic factors, in BIO TO2.

METHODS AND RESULTS

At the age of 5 weeks, percent fractional shortening (%FS) and positive rate of change in left ventricular pressure over time (dP/dt max) were lower in BIO TO2 than in age-matched F1B controls. Capillary density, capillary/myocyte (CM) ratio, capillary domain area (CDA), and myocyte density were similar between BIO TO2 and F1B controls. At the ages of 13 and 20 weeks, BIO had significantly lower capillary and myocyte densities and a significantly higher CM ratio and CDA. Myocyte density positively correlated with %FS and dP/dt max. There were no significant differences in mRNA expression for VEGF, Flt-1, angiopoietin-1, or angiopoietin-2 between BIO TO2 and F1B control.

CONCLUSION

Progressive myocyte loss is responsible for deterioration of cardiac function in BIO TO2. The impaired neovascularization may be involved in the progress of cardiac remodeling in cardiomyopathic hamsters.

Analysis of the distribution of binding sites for the plant lectin Bandeiraea simplicifolia I-isolectin B4 on primary sensory neurones in seven mammalian species

The purpose of the present study was to investigate the binding patterns of the plant lectin Bandeiraea simplicifolia I-isolectin B(4) (BSI-B(4)) to sensory neurones in seven mammalian species. The dorsal root ganglia and spinal cords of three rats, mice, guinea pigs, rabbits, flying foxes, cats, and marmoset monkeys were screened for BSI-B(4) using lectin histochemistry. BSI-B(4) binding was associated with the soma of predominantly small-diameter primary sensory neurones in the dorsal root ganglia and their axon terminals within laminae I and II of the superficial dorsal horn in all seven species. The similarities of lectin binding patterns in each of these species suggest that the glycoconjugate to which BSI-B(4) binds has a ubiquitous distribution in mammals, and supports the proposal that this lectin may preferentially bind to a subpopulation of sensory neurones with a similar functional role in each of these species.

Differentiation of proliferated NG2-positive glial progenitor cells in a remyelinating lesion

Cells that express the NG2 proteoglycan (NG2+ cells) constitute a large cell population in the adult mammalian central nervous system (CNS). They give rise to mature oligodendrocytes in culture and are thus considered to be oligodendrocyte progenitor cells (OPCs). They proliferate in response to a variety of insults to the CNS, but their ability to differentiate into oligodendrocytes in vivo has not been established. We used bromodeoxyuridine (BrdU) to trace the fate of NG2+ cells that proliferated in response to a chemically induced demyelinating lesion in the adult rat spinal cord. Cells that were proliferating 24 hr after lesioning were labeled by a single injection of BrdU, and their antigenic phenotype was examined at various times up to 28 days post-lesioning (28 dpl). Initially, at 2 dpl, NG2+/BrdU+ cells were found almost exclusively at the periphery of the lesion. At 7 dpl, the number of NG2+/BrdU+ cells increased in the lesion center and decreased from the surrounding areas. The number of NG2+/BrdU+ cells inside the lesion further decreased with time, concomitant with progression of remyelination and appearance of BrdU+ mature oligodendrocytes. Double labeling with (3)H-thymidine and BrdU combined with NG2 immunohistochemistry showed that some NG2+ cells in the lesion had undergone at least two rounds of cell division. These observations strongly suggest that NG2+/BrdU+ cells that appeared in response to the demyelinating insult gave rise to mature remyelinating oligodendrocytes, providing an in vivo evidence for the differentiation of NG2+ cells into oligodendrocytes.

Histological markers for endothelial cells in endogenous and transplanted rodent pancreatic islets

BACKGROUND/AIMS

To obtain a selective marker to identify endothelial cells is difficult, due to the heterogeneity of these cells. Most described markers perform well in some applications, but fail in others. The aim of this study was to identify a selective and specific marker for rodent microvascular endothelial cells, especially for use in studies on the vascular system of pancreatic islets.

METHODS

A biotin-labelled form of the lectin Bandeiraea or Griffonia simplicifolia in combination with a streptAB-Complex with alkaline phosphatase was used to stain endothelium in paraffin-embedded tissue sections from C57BL/6 mice, Sprague-Dawley or Wistar-Furth rats.

RESULTS

We were consistently able to selectively stain microvascular endothelial cells in lungs, small intestines, white and brown adipose tissue, pancreas and islets of Langerhans with the lectin Bandeiraea simplicifolia. Furthermore, we were able to visualise the vasculature in syngenically transplanted islets of Langerhans in Wistar-Furth rats and C57BL/6 mice. Attempts to stain rodent endothelial cells with antibodies against CD34, CD31, CD200, Ox43, von Willebrand factor and the lectin Ulex europaeus were not uniformly successful.

CONCLUSION

The lectin Bandeiraea simplicifolia is a versatile marker for rodent endothelial cells, and may be used to study revascularisation after transplantation of pancreatic islet in rodents.

Human NK cell-mediated cytotoxicity triggered by CD86 and Gal alpha 1,3-Gal is inhibited in genetically modified porcine cells

Delayed xenograft rejection is a major hurdle that needs to be addressed to prolong graft survival in pig-to-primate xenotransplantation. NK cell activation has been implicated in delayed xenograft rejection. Both Ab-dependent and independent mechanisms are responsible for the high susceptibility of porcine cells to human NK cell-mediated cytotoxicity. Previous reports demonstrated a role of Galalpha1,3-Gal Ag in triggering the Ab-independent responses. We hypothesize that expression of CD80 and/or CD86 on porcine cells may also play a role in NK cell activation as human NK cells express a variant of CD28. Our initial analysis showed that porcine endothelial cells and fibroblasts express CD86, but not CD80. Genetic engineering of these cells to express hCD152-hCD59, a chimeric molecule designed to block CD86 in cis, was accompanied by a reduction in susceptibility to human NK cell-mediated cytotoxicity. The use of a specific anti-porcine CD86-blocking Ab and the NK92 and YTS cell lines further confirmed the involvement of CD86 in triggering NK cell-mediated lysis of porcine cells. Maximal protection was achieved when hCD152-hCD59 was expressed in H transferase-transgenic cells, which show reduced Galalpha1,3-Gal expression. In this work, we describe two mechanisms of human NK cell-mediated rejection of porcine cells and demonstrate that genetically modified cells resist Ab-independent NK cell-mediated cytotoxicity.