RESUMO
Galectins are multifunctional effectors in cellular homeostasis and dysregulation. Oxidation of human galectin-1 (Gal-1) with its six sulfhydryls produces a disulfide-bridged oxidized form that lacks normal lectin activity yet gains new glycan-independent functionality. Nevertheless, the mechanistic details as to how Gal-1 oxidation occurs remain unclear. Here, we used 15N and 13C HSQC NMR spectroscopy to gain structural insight into the CuSO4-mediated path of Gal-1 oxidation and identified a minimum two-stage conversion process. During the first phase, disulfide bridges form slowly between C16-C88 and/or C42-C66 to produce a partially oxidized, conformationally flexible intermediate that retains the ability to bind lactose. Site-directed mutagenesis of C16 to S16 impedes the onset of this overall slow process. During the second phase, increased motional dynamics of the intermediate enable the relatively distant C2 and C130 residues to form the third and final disulfide bond, leading to an unfolded state and consequent dimer dissociation. This fully oxidized end state loses the ability to bind lactose, as shown by the hemagglutination assay. Consistent with this model, we observed that the Gal-1 C2S mutant maintains intermediate-state structural features with a free sulfhydryl group at C130. Incubation with dithiothreitol reduces all disulfide bonds and allows the lectin to revert to its native state. Thus, the sequential, non-random formation of three disulfide bridges in Gal-1 in an oxidative environment acts as a molecular switch for fundamental changes to its functionality. These data inspire detailed bioactivity analysis of the structurally defined oxidized intermediate in, e.g., acute and chronic inflammation.
Assuntos
Cisteína , Galectina 1 , Oxirredução , Galectina 1/metabolismo , Galectina 1/química , Galectina 1/genética , Humanos , Cisteína/metabolismo , Cisteína/química , Dissulfetos/metabolismo , Dissulfetos/química , Dobramento de Proteína , Desdobramento de Proteína , Modelos Moleculares , Lactose/metabolismo , Lactose/química , Mutagênese Sítio-DirigidaRESUMO
Wild-type lectins have distinct types of modular design. As a step to explain the physiological importance of their special status, hypothesis-driven protein engineering is used to generate variants. Concerning adhesion/growth-regulatory galectins, non-covalently associated homodimers are commonly encountered in vertebrates. The homodimeric galectin-7 (Gal-7) is a multifunctional context-dependent modulator. Since the possibility of conversion from the homodimer to hybrids with other galectin domains, i.e. from Gal-1 and Gal-3, has recently been discovered, we designed Gal-7-based constructs, i.e. stable (covalently linked) homo- and heterodimers. They were produced and purified by affinity chromatography, and the sugar-binding activity of each lectin unit proven by calorimetry. Inspection of profiles of binding of labeled galectins to an array-like platform with various cell types, i.e. sections of murine epididymis and jejunum, and impact on neuroblastoma cell proliferation revealed no major difference between natural and artificial (stable) homodimers. When analyzing heterodimers, acquisition of altered properties was seen. Remarkably, binding properties and activity as effector can depend on the order of arrangement of lectin domains (from N- to C-termini) and on the linker length. After dissociation of the homodimer, the Gal-7 domain can build new functionally active hybrids with other partners. This study provides a clear direction for research on defining the full range of Gal-7 functionality and offers the perspective of testing applications for engineered heterodimers.
Assuntos
Galectinas/metabolismo , Engenharia de Proteínas , Linhagem Celular Tumoral , Galectinas/análise , Galectinas/isolamento & purificação , Humanos , Espectrometria de MassasRESUMO
Human macrophage galactose-type lectin (hMGL, HML, CD301, CLEC10A), a C-type lectin expressed by dendritic cells and macrophages, is a receptor for N-acetylgalactosamine α-linked to serine/threonine residues (Tn antigen, CD175) and its α2,6-sialylated derivative (sTn, CD175s). Because these two epitopes are among malignant cell glycan displays, particularly when presented by mucin-1 (MUC1), assessing the influence of the site and frequency of glycosylation on lectin recognition will identify determinants governing this interplay. Thus, chemical synthesis of the tandem-repeat O-glycan acceptor region of MUC1 and site-specific threonine glycosylation in all permutations were carried out. Isothermal titration calorimetry (ITC) analysis of the binding of hMGL to this library of MUC1 glycopeptides revealed an enthalpy-driven process and an affinity enhancement of an order of magnitude with an increasing glycan count from 6-8 µM for monoglycosylated peptides to 0.6 µM for triglycosylated peptide. ITC measurements performed in D2O permitted further exploration of the solvation dynamics during binding. A shift in enthalpy-entropy compensation and contact position-specific effects with the likely involvement of the peptide surroundings were detected. KinITC analysis revealed a prolonged lifetime of the lectin-glycan complex with increasing glycan valency and with a change in the solvent to D2O.
Assuntos
Lectinas Tipo C/química , Mucina-1/química , Sequência de Aminoácidos , Antígenos Glicosídicos Associados a Tumores/química , Antígenos Glicosídicos Associados a Tumores/metabolismo , Calorimetria/métodos , Epitopos/metabolismo , Galactose , Glicopeptídeos/química , Glicopeptídeos/metabolismo , Glicosilação , Humanos , Lectinas Tipo C/metabolismo , Macrófagos/metabolismo , Mucina-1/metabolismo , Ligação ProteicaRESUMO
Having identified glycans of cellular glycoconjugates as versatile molecular messages, their recognition by sugar receptors (lectins) is a fundamental mechanism within the flow of biological information. This type of molecular interplay is increasingly revealed to be involved in a wide range of (patho)physiological processes. To do so, it is a vital prerequisite that a lectin (and its expression) can develop more than a single skill, that is the general ability to bind glycans. By studying the example of vertebrate galectins as a model, a total of five relevant characteristics is disclosed: i) access to intra- and extracellular sites, ii) fine-tuned gene regulation (with evidence for co-regulation of counterreceptors) including the existence of variants due to alternative splicing or single nucleotide polymorphisms, iii) specificity to distinct glycans from the glycome with different molecular meaning, iv) binding capacity also to peptide motifs at different sites on the protein and v) diversity of modular architecture. They combine to endow these lectins with the capacity to serve as multi-purpose tools. Underscoring the arising broad-scale significance of tissue lectins, their numbers in terms of known families and group members have steadily grown by respective research that therefore unveiled a well-stocked toolbox. The generation of a network of (ga)lectins by evolutionary diversification affords the opportunity for additive/synergistic or antagonistic interplay in situ, an emerging aspect of (ga)lectin functionality. It warrants close scrutiny. The realization of the enormous potential of combinatorial permutations using the five listed features gives further efforts to understand the rules of functional glycomics/lectinomics a clear direction.
Assuntos
Galectinas , Animais , Sítios de Ligação , Evolução Biológica , Diferenciação Celular , Galactose/metabolismo , Galectina 1/metabolismo , Galectina 3/metabolismo , Galectinas/biossíntese , Galectinas/química , Galectinas/metabolismo , Regulação da Expressão Gênica , Glicoconjugados , Humanos , Ligantes , Peptídeos/metabolismo , Polissacarídeos , Receptores de Superfície CelularRESUMO
The emerging multifunctionality of galectins by specific protein-glycan/protein interactions explains the interest to determine their expression during embryogenesis. Complete network analysis of all seven chicken galectins (CGs) is presented in the course of differentiation of eye lens that originates from a single type of progenitor cell. It answers the questions on levels of expression and individual patterns of distribution. A qualitative difference occurs in the CG-1A/B paralogue pair, underscoring conspicuous divergence. Considering different cell phenotypes, lens fiber and also epithelial cells can both express the same CG, with developmental upregulation for CG-3 and CG-8. Except for expression of the lens-specific CG (C-GRIFIN), no other CG appeared to be controlled by the transcription factors L-Maf and Pax6. Studying presence and nature of binding partners for CGs, we tested labeled galectins in histochemistry and in ligand blotting. Mass spectrometric (glyco)protein identification after affinity chromatography prominently yielded four types of crystallins, N-CAM, and, in the cases of CG-3 and CG-8, N-cadherin. Should such pairing be functional in situ, it may be involved in tightly packing intracellular lens proteins and forming membrane contact as well as in gaining plasticity and stability of adhesion processes. The expression of CGs throughout embryogenesis is postulated to give meaning to spatiotemporal alterations in the local glycome.
Assuntos
Cristalinas/metabolismo , Galectinas/metabolismo , Cristalino/embriologia , Animais , Western Blotting , Embrião de Galinha , Cromatografia de Afinidade , Galectinas/genética , Regulação da Expressão Gênica no Desenvolvimento , Cristalino/metabolismo , Ligantes , Fatores de Transcrição Maf/metabolismo , Microscopia de Fluorescência , Fator de Transcrição PAX6/metabolismo , Regiões Promotoras Genéticas , Ligação Proteica , Reação em Cadeia da Polimerase em Tempo Real , Células-Tronco/metabolismoRESUMO
Glycan-lectin recognition is assumed to elicit its broad range of (patho)physiological functions via a combination of specific contact formation with generation of complexes of distinct signal-triggering topology on biomembranes. Faced with the challenge to understand why evolution has led to three particular modes of modular architecture for adhesion/growth-regulatory galectins in vertebrates, here we introduce protein engineering to enable design switches. The impact of changes is measured in assays on cell growth and on bridging fully synthetic nanovesicles (glycodendrimersomes) with a chemically programmable surface. Using the example of homodimeric galectin-1 and monomeric galectin-3, the mutual design conversion caused qualitative differences, i.e., from bridging effector to antagonist/from antagonist to growth inhibitor and vice versa. In addition to attaining proof-of-principle evidence for the hypothesis that chimera-type galectin-3 design makes functional antagonism possible, we underscore the value of versatile surface programming with a derivative of the pan-galectin ligand lactose. Aggregation assays with N,N'-diacetyllactosamine establishing a parasite-like surface signature revealed marked selectivity among the family of galectins and bridging potency of homodimers. These findings provide fundamental insights into design-functionality relationships of galectins. Moreover, our strategy generates the tools to identify biofunctional lattice formation on biomembranes and galectin-reagents with therapeutic potential.
Assuntos
Galectina 1/química , Galectina 3/química , Glicoconjugados/química , Polissacarídeos/química , Amino Açúcares/química , Amino Açúcares/metabolismo , Sítios de Ligação , Proteínas Sanguíneas , Adesão Celular/genética , Proliferação de Células/genética , Galectina 1/genética , Galectina 3/genética , Galectinas , Humanos , Lactose/química , Ligantes , Nanopartículas/química , Polissacarídeos/genéticaRESUMO
Tissue lectins appear to be involved in a broad range of physiological processes, as reflected for the members of the family of galectins by referring to them as adhesion/growth-regulatory effectors. In order to clarify the significance of galectin presence, key challenges are to define their binding partners and the profile of localization. Having identified the chicken galectin-related interfiber protein (C-GRIFIN) as lens-specific protein present in the main body of adult lens, we here report its interaction with lens proteins in ligand blotting. The assumption for pairing with α-, ß- and δ-crystallins was ascertained by mass spectrometric detection of their presence in eluted fractions obtained by affinity chromatography. Biochemical and immunohistochemical monitoring revealed protein presence from about 3-day-old embryos onwards, mostly in the cytoplasm of elongated posterior cells, later in secondary lens fiber cells. On the level of gene expression, its promoter was activated by transcription factor L-Maf alone and together with Pax6 like a crystallin gene, substantiating C-GRIFIN's status as lens-specific galectin. Using this combined strategy for counterreceptor and expression profiling by bio- and histochemical methods including light, electron and fluorescence microscopy, respective monitoring in lens development can now be taken to the level of the complete galectin family.
Assuntos
Galinhas/genética , Proteínas do Olho/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Cristalino/embriologia , Cristalino/metabolismo , Fator de Transcrição PAX6/metabolismo , Animais , Sequência de Bases , Sítios de Ligação , Cromatografia de Afinidade , Proteínas do Olho/genética , Genes Reporter , Cristalino/ultraestrutura , Ligantes , Fatores de Transcrição Maf , Espectrometria de Massas , Ligação ProteicaRESUMO
The delineation of the physiological significance of protein (lectin)-glycan recognition and the structural analysis of individual lectins have directed our attention to studying them in combination. In this report, we tested the hypothesis of hybrid formation by using binary mixtures of homodimeric galectin-1 and -7 as well as a proteolytically truncated version of chimera-type galectin-3. Initial supportive evidence is provided by affinity chromatography using resin-presented galectin-7. Intriguingly, the extent of cell binding by cross-linking of surface counter-receptor increased significantly for monomeric galectin-3 form by the presence of galectin-1 or -7. Pulsed-field gradient NMR (nuclear magnetic resonance) diffusion measurements on these galectin mixtures indicated formation of heterodimers as opposed to larger oligomers. 15N-1H heteronuclear single quantum coherence NMR spectroscopy and molecular dynamics simulations allowed us to delineate how different galectins interact in the heterodimer. The possibility of domain exchange between galectins introduces a new concept for understanding the spectrum of their functionality, particularly when these effector molecules are spatially and temporally co-expressed as found in vivo.
Assuntos
Galectinas/metabolismo , Multimerização Proteica , Sítios de Ligação , Proteínas Sanguíneas , Moléculas de Adesão Celular/metabolismo , Moléculas de Adesão Celular/fisiologia , Proliferação de Células/fisiologia , Galectina 1/química , Galectina 1/metabolismo , Galectina 3/química , Galectina 3/metabolismo , Galectinas/química , Galectinas/fisiologia , Humanos , Multimerização Proteica/fisiologia , Proteínas/metabolismo , Células Tumorais CultivadasRESUMO
Chemical and biological tools are harnessed to investigate the impact of spatial factors for functional pairing of human lectins with counterreceptors. The homodimeric adhesion/growth-regulatory galectin-1 and a set of covalently linked homo-oligomers from di- to tetramers serve as proof-of-principle test cases. Glycodendrimersomes provide a versatile and sensitive diagnostic platform to reveal thresholds for ligand density and protein concentration in aggregation assays (trans-activity), irrespective of linker length between lectin domains. Monitoring the affinity of cell binding and ensuing tumor growth inhibition reveal the linker length to be a bidirectional switch for cis-activity. The discovery that two aspects of lectin functionality (trans- versus cis-activity) respond non-uniformly to a structural change underscores the power of combining synthetic and biological tools to advance understanding of the sugar functionality of the cell surface.
Assuntos
Lectinas/química , Polissacarídeos/química , Açúcares/química , Membrana Celular/química , HumanosRESUMO
Tissue lectins are emerging (patho)physiological effectors with broad significance. The capacity of adhesion/growth-regulatory galectins to form functional complexes with distinct cellular glycoconjugates is based on molecular selection of matching partners. Engineering of variants by changing the topological display of carbohydrate recognition domains (CRDs) provides tools to understand the inherent specificity of the functional pairing. We here illustrate its practical implementation in the case of human tandem-repeat-type galectin-8 (Gal-8). It is termed Gal-8 (NC) due to presence of two different CRDs at the N- and C-terminal positions. Gal-8N exhibits exceptionally high affinity for 3'-sialylated/sulfated ß-galactosides. This protein is turned into a new homodimer, i.e., Gal-8 (NN), by engineering. The product maintained activity for lactose-inhibitable binding of glycans and glycoproteins. Preferential association with 3'-sialylated/sulfated (and 6-sulfated) ß-galactosides was seen by glycan-array analysis when compared to the wild-type protein, which also strongly bound to ABH-type epitopes. Agglutination of erythrocytes documented functional bivalency. This result substantiates the potential for comparative functional studies between the variant and natural Gal-8 (NC)/Gal-8N.
Assuntos
Galectinas/química , Glicoconjugados/química , Animais , Sítios de Ligação , Células CHO , Cricetulus , Galactosídeos/química , Humanos , Polissacarídeos/química , Ligação Proteica , Conformação Proteica , Multimerização Proteica , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Sequências de Repetição em Tandem , Termodinâmica , Aderências TeciduaisRESUMO
OBJECTIVE: Preterm brain injury is a major cause of disability in later life, and may result in motor, cognitive and behavioural impairment for which no treatment is currently available. The aetiology is considered as multifactorial, and one underlying key player is inflammation leading to white and grey matter injury. Extracellular vesicles secreted by mesenchymal stem/stromal cells (MSC-EVs) have shown therapeutic potential in regenerative medicine. Here, we investigated the effects of MSC-EV treatment on brain microstructure and maturation, inflammatory processes and long-time outcome in a rodent model of inflammation-induced brain injury. METHODS: 3-Day-old Wistar rats (P3) were intraperitoneally injected with 0.25mg/kg lipopolysaccharide or saline and treated with two repetitive doses of 1×108 cell equivalents of MSC-EVs per kg bodyweight. Cellular degeneration and reactive gliosis at P5 and myelination at P11 were evaluated by immunohistochemistry and western blot. Long-term cognitive and motor function was assessed by behavioural testing. Diffusion tensor imaging at P125 evaluated long-term microstructural white matter alterations. RESULTS: MSC-EV treatment significantly ameliorated inflammation-induced neuronal cellular degeneration reduced microgliosis and prevented reactive astrogliosis. Short-term myelination deficits and long-term microstructural abnormalities of the white matter were restored by MSC-EV administration. Morphological effects of MSC-EV treatment resulted in improved long-lasting cognitive functions INTERPRETATION: MSC-EVs ameliorate inflammation-induced cellular damage in a rat model of preterm brain injury. MSC-EVs may serve as a novel therapeutic option by prevention of neuronal cell death, restoration of white matter microstructure, reduction of gliosis and long-term functional improvement.
Assuntos
Lesões Encefálicas/metabolismo , Encefalite/metabolismo , Células-Tronco Mesenquimais/citologia , Substância Branca/efeitos dos fármacos , Animais , Cognição/fisiologia , Modelos Animais de Doenças , Vesículas Extracelulares/metabolismo , Transplante de Células-Tronco Mesenquimais/métodos , Ratos WistarRESUMO
UNLABELLED: Preterm neonates are susceptible to perinatal hypoxic-ischemic brain injury, for which no treatment is available. In a preclinical animal model of hypoxic-ischemic brain injury in ovine fetuses, we have demonstrated the neuroprotective potential of systemically administered mesenchymal stromal cells (MSCs). The mechanism of MSC treatment is unclear but suggested to be paracrine, through secretion of extracellular vesicles (EVs). Therefore, we investigated in this study the protective effects of mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) in a preclinical model of preterm hypoxic-ischemic brain injury. Ovine fetuses were subjected to global hypoxia-ischemia by transient umbilical cord occlusion, followed by in utero intravenous administration of MSC-EVs. The therapeutic effects of MSC-EV administration were assessed by analysis of electrophysiological parameters and histology of the brain. Systemic administration of MSC-EVs improved brain function by reducing the total number and duration of seizures, and by preserving baroreceptor reflex sensitivity. These functional protections were accompanied by a tendency to prevent hypomyelination. Cerebral inflammation remained unaffected by the MSC-EV treatment. Our data demonstrate that MSC-EV treatment might provide a novel strategy to reduce the neurological sequelae following hypoxic-ischemic injury of the preterm brain. Our study results suggest that a cell-free preparation comprising neuroprotective MSC-EVs could substitute MSCs in the treatment of preterm neonates with hypoxic-ischemic brain injury, thereby circumventing the potential risks of systemic administration of living cells. SIGNIFICANCE: Bone marrow-derived mesenchymal stromal cells (MSCs) show promise in treating hypoxic-ischemic injury of the preterm brain. Study results suggest administration of extracellular vesicles, rather than intact MSCs, is sufficient to exert therapeutic effects and avoids potential concerns associated with administration of living cells. The therapeutic efficacy of systemically administered mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) on hypoxia-ischemia-induced injury was assessed in the preterm ovine brain. Impaired function and structural injury of the fetal brain was improved following global hypoxia-ischemia. A cell-free preparation of MSC-EVs could substitute for the cellular counterpart in the treatment of preterm neonates with hypoxic-ischemic brain injury. This may open new clinical applications for "off-the-shelf" interventions with MSC-EVs.
Assuntos
Terapia Baseada em Transplante de Células e Tecidos , Hipóxia-Isquemia Encefálica/terapia , Inflamação/terapia , Células-Tronco Mesenquimais/metabolismo , Animais , Encéfalo/fisiopatologia , Lesões Encefálicas/fisiopatologia , Lesões Encefálicas/terapia , Proliferação de Células , Modelos Animais de Doenças , Vesículas Extracelulares/metabolismo , Feto , Humanos , Hipóxia-Isquemia Encefálica/fisiopatologia , Inflamação/fisiopatologia , Células-Tronco Mesenquimais/citologia , OvinosRESUMO
UNLABELLED: Although the initial concepts of stem cell therapy aimed at replacing lost tissue, more recent evidence has suggested that stem and progenitor cells alike promote postischemic neurological recovery by secreted factors that restore the injured brain's capacity to reshape. Specifically, extracellular vesicles (EVs) derived from stem cells such as exosomes have recently been suggested to mediate restorative stem cell effects. In order to define whether EVs indeed improve postischemic neurological impairment and brain remodeling, we systematically compared the effects of mesenchymal stem cell (MSC)-derived EVs (MSC-EVs) with MSCs that were i.v. delivered to mice on days 1, 3, and 5 (MSC-EVs) or on day 1 (MSCs) after focal cerebral ischemia in C57BL6 mice. For as long as 28 days after stroke, motor coordination deficits, histological brain injury, immune responses in the peripheral blood and brain, and cerebral angiogenesis and neurogenesis were analyzed. Improved neurological impairment and long-term neuroprotection associated with enhanced angioneurogenesis were noticed in stroke mice receiving EVs from two different bone marrow-derived MSC lineages. MSC-EV administration closely resembled responses to MSCs and persisted throughout the observation period. Although cerebral immune cell infiltration was not affected by MSC-EVs, postischemic immunosuppression (i.e., B-cell, natural killer cell, and T-cell lymphopenia) was attenuated in the peripheral blood at 6 days after ischemia, providing an appropriate external milieu for successful brain remodeling. Because MSC-EVs have recently been shown to be apparently safe in humans, the present study provides clinically relevant evidence warranting rapid proof-of-concept studies in stroke patients. SIGNIFICANCE: Transplantation of mesenchymal stem cells (MSCs) offers an interesting adjuvant approach next to thrombolysis for treatment of ischemic stroke. However, MSCs are not integrated into residing neural networks but act indirectly, inducing neuroprotection and promoting neuroregeneration. Although the mechanisms by which MSCs act are still elusive, recent evidence has suggested that extracellular vesicles (EVs) might be responsible for MSC-induced effects under physiological and pathological conditions. The present study has demonstrated that EVs are not inferior to MSCs in a rodent stroke model. EVs induce long-term neuroprotection, promote neuroregeneration and neurological recovery, and modulate peripheral post-stroke immune responses. Also, because EVs are well-tolerated in humans, as previously reported, the administration of EVs under clinical settings might set the path for a novel and innovative therapeutic stroke concept without the putative side effects attached to stem cell transplantation.
Assuntos
Vesículas Extracelulares/transplante , Infarto da Artéria Cerebral Média/terapia , Células-Tronco Mesenquimais/ultraestrutura , Regeneração Nervosa , Animais , Ataxia/etiologia , Ataxia/prevenção & controle , Encéfalo/imunologia , Encéfalo/patologia , Movimento Celular , Meios de Cultivo Condicionados , Modelos Animais de Doenças , Infarto da Artéria Cerebral Média/complicações , Infarto da Artéria Cerebral Média/imunologia , Infarto da Artéria Cerebral Média/fisiopatologia , Ativação Linfocitária , Contagem de Linfócitos , Masculino , Transplante de Células-Tronco Mesenquimais , Camundongos , Camundongos Endogâmicos C57BL , Células Mieloides/imunologia , Células Mieloides/patologia , Especificidade de Órgãos , Distribuição Aleatória , Teste de Desempenho do Rota-RodRESUMO
Hematopoietic stem and progenitor cells (HSPCs) can self-renew and create committed progenitors, a process supposed to involve asymmetric cell divisions (ACDs). Previously, we had linked the kinetics of CD133 expression with ACDs but failed to detect asymmetric segregation of classical CD133 epitopes on fixed, mitotic HSPCs. Now, by using a novel anti-CD133 antibody (HC7), we confirmed the occurrence of asymmetric CD133 segregation on paraformaldehyde-fixed and living HSPCs. After showing that HC7 binding does not recognizably affect biological features of human HSPCs, we studied ACDs in different HSPC subtypes and determined the developmental potential of arising daughter cells at the single-cell level. Approximately 70% of the HSPCs of the multipotent progenitor (MPP) fraction studied performed ACDs, and about 25% generated lymphoid-primed multipotent progenitor (LMPP) as wells as erythromyeloid progenitor (EMP) daughter cells. Since MPPs hardly created daughter cells maintaining MPP characteristics, our data suggest that under conventional culture conditions, ACDs are lineage instructive rather than self-renewing.
Assuntos
Divisão Celular Assimétrica , Diferenciação Celular , Células-Tronco Hematopoéticas/citologia , Células Progenitoras Linfoides/citologia , Células Progenitoras Mieloides/citologia , Animais , Antígenos de Superfície/metabolismo , Adesão Celular , Linhagem da Célula , Movimento Celular , Células Cultivadas , Ensaio de Unidades Formadoras de Colônias , Células Precursoras Eritroides/citologia , Células Precursoras Eritroides/metabolismo , Hematopoese , Transplante de Células-Tronco Hematopoéticas , Células-Tronco Hematopoéticas/metabolismo , Xenoenxertos , Humanos , Imunofenotipagem , Células Progenitoras Linfoides/metabolismo , Camundongos , Células Progenitoras Mieloides/metabolismo , FenótipoRESUMO
Novel therapeutic concepts against cerebral ischemia focus on cell-based therapies in order to overcome some of the side effects of thrombolytic therapy. However, cell-based therapies are hampered because of restricted understanding regarding optimal cell transplantation routes and due to low survival rates of grafted cells. We therefore transplanted adult green fluorescence protein positive neural precursor cells (NPCs) either intravenously (systemic) or intrastriatally (intracerebrally) 6 hours after stroke in mice. To enhance survival of NPCs, cells were in vitro protein-transduced with TAT-heat shock protein 70 (Hsp70) before transplantation followed by a systematic analysis of brain injury and underlying mechanisms depending on cell delivery routes. Transduction of NPCs with TAT-Hsp70 resulted in increased intracerebral numbers of grafted NPCs after intracerebral but not after systemic transplantation. Whereas systemic delivery of either native or transduced NPCs yielded sustained neuroprotection and induced neurological recovery, only TAT-Hsp70-transduced NPCs prevented secondary neuronal degeneration after intracerebral delivery that was associated with enhanced functional outcome. Furthermore, intracerebral transplantation of TAT-Hsp70-transduced NPCs enhanced postischemic neurogenesis and induced sustained high levels of brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, and vascular endothelial growth factor in vivo. Neuroprotection after intracerebral cell delivery correlated with the amount of surviving NPCs. On the contrary, systemic delivery of NPCs mediated acute neuroprotection via stabilization of the blood-brain-barrier, concomitant with reduced activation of matrix metalloprotease 9 and decreased formation of reactive oxygen species. Our findings imply two different mechanisms of action of intracerebrally and systemically transplanted NPCs, indicating that systemic NPC delivery might be more feasible for translational stroke concepts, lacking a need of in vitro manipulation of NPCs to induce long-term neuroprotection.
Assuntos
Isquemia Encefálica/terapia , Proteínas de Choque Térmico HSP70/genética , Células-Tronco Neurais/fisiologia , Células-Tronco Neurais/transplante , Acidente Vascular Cerebral/terapia , Animais , Isquemia Encefálica/metabolismo , Isquemia Encefálica/cirurgia , Diferenciação Celular/fisiologia , Modelos Animais de Doenças , Técnicas de Transferência de Genes , Proteínas de Choque Térmico HSP70/biossíntese , Proteínas de Choque Térmico HSP70/metabolismo , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Transplante de Células-Tronco/métodos , Acidente Vascular Cerebral/genética , Acidente Vascular Cerebral/metabolismo , Acidente Vascular Cerebral/cirurgia , Transdução GenéticaRESUMO
Freshly isolated human hematopoietic stem and progenitor cells (HSPCs) are small and round cells which upon cultivation adopt a polarized morphology and redistribute certain cell surface antigens. To functionally dissect this polarization process, we addressed impacts of protein synthesis, HSPC trafficking, cytoskeleton organization or lipid raft integrity on the establishment and maintenance of the cell polarity of human HSPCs. Effects on the morphology, sub-cellular distribution of lipid raft-associated molecular polarization markers (Flotillin-1, Flotillin-2, ICAM-3) and in vitro migration capabilities of treated cells were studied. We could distinguish two levels of cellular polarization, a molecular and a morphological level. Our data suggest that protein synthesis, lipid raft integrity and enzymatic activities of PI3K and aPKC are required to organize the molecular cell polarity. The morphological cell polarization process, however, also depends on actin polymerization and rho-GTPase activities. In summary, our data qualify HSPC polarization processes as new pharmaceutical target to interfere with migratory and with homing capabilities of HSPCs.
Assuntos
Movimento Celular/fisiologia , Células-Tronco Hematopoéticas/citologia , Células-Tronco Hematopoéticas/metabolismo , Microdomínios da Membrana/metabolismo , Células-Tronco/citologia , Células-Tronco/metabolismo , Animais , Moléculas de Adesão Celular/metabolismo , Polaridade Celular/fisiologia , Humanos , Immunoblotting , Camundongos , Camundongos Endogâmicos NODRESUMO
Exosomes are small membrane vesicles, which eukaryotic cells secrete into their extracellular environment. They are formed as intraluminal vesicles by inward budding of the limiting membrane into the lumen of late endosomes. Upon fusion of thus arising multivesicular bodies with the plasma membrane, these vesicles are released as exosomes and enter body fluids such as blood plasma, urine and saliva. Containing certain combinations of lipids, adhesion and intercellular signaling molecules as well as RNAs, exosomes participate in intercellular communication processes. Depending on their origin, exosomes can modulate immune-regulatory processes, set up tumor escape mechanisms and mediate regenerative or degenerative processes, amongst others. In summary, exosomes are molecular complex intercellular signaling organelles with multiple functions, which appear as promising new tools for the clinical diagnostics and potentially for novel therapeutic strategies.
Assuntos
Comunicação Celular/fisiologia , Exossomos/fisiologia , Animais , Transporte Biológico , Membrana Celular/fisiologia , HumanosRESUMO
Exosomes from three different cell types (HEK 293T, ECFC, MSC) were characterised by scanning electron microscopy (SEM), dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). The diameter was around 110 nm for the three cell types. The stability of exosomes was examined during storage at -20°C, 4°C, and 37°C. The size of the exosomes decreased at 4°C and 37°C, indicating a structural change or degradation. Multiple freezing to -20°C and thawing did not affect the exosome size. Multiple ultracentrifugation also did not change the exosome size.
Assuntos
Células Endoteliais/citologia , Exossomos/ultraestrutura , Células-Tronco Mesenquimais/citologia , Nanopartículas/ultraestrutura , Nanotecnologia/métodos , Coloides , Células HEK293 , Humanos , Microscopia Eletrônica de Varredura , Tamanho da Partícula , TemperaturaRESUMO
Mesenchymal stem cells (MSCs) are multipotent progenitor cells with the capacity to differentiate into different tissue cell types such as chondrocytes, osteocytes, and adipocytes. In addition, they can home to damaged, in-flamed, and malignant tissues and display immunomodulatory properties. Since tissue-derived factors might modulate these properties, we decided to explore the impact of prototypic tissue-derived inflammatory cytokines such as TNF-alpha and IFN-gamma on immunomodulatory MSCs functions. To this end, we used primary bone marrow and cord blood-derived MSCs as well as an immortalized MSC line (V54/2) as model systems. We demonstrate that under unstimulated conditions, V54/2 cells constitutively express low levels of indoleamine 2,3-dioxygenase (IDO), exert an immunosuppressive effect on activated T-lymphocyte proliferation, secrete a distinct set of cytokines, and express a wide range of chemokine receptors. Upon stimulation, the proinflammatory cytokines IFN-gamma and TNF-alpha did not inhibit suppression of T-cell proliferation, although IDO expression was up-regulated by IFN-gamma. In contrast, TNF-alpha but not IFN-gamma amplified the cytokine production of V54/2 and primary MSCs. Interestingly, IFN-gamma was superior to TNF-alpha in up-regulating expression of chemokine receptors and migration of the V54/2 cell line, while TNF-alpha was the predominant regulator of migration in primary MSCs. Altogether, our data show that properties of MSCs depend on local environmental factors. In particular, we have shown that IFN-gamma and TNF-alpha differentially regulate cytokine expression and migration of MSCs.