Universiẗat, Diss., 2003--Jena.

Universiẗat, Diss., 2002--Essen.

Human adult mesenchymal stem cells (MSCs) derived from bone marrow have the capacity to self-renew and to differentiate into a variety of cells and tissues. They can leave their niche to migrate to remote tissues where they play a critical role in angiogenesis, wound repair and tissue regeneration. A major goal in adult stem cell research is to define how MSC fate is controlled by the pericellular extracellular matrix (ECM) and soluble factors that largely constitute their tissue-specific niches. Defining crucial regulatory signals that control the fate and function of MSCs in vitro will contribute to the development of therapeutic strategies to improve tissue regeneration. The objective of this study was to investigate the molecular relationships between cell-ECM integrin receptors and platelet-derived growth factor receptor (PDGFR) tyrosine kinases, which are crucial in modulating MSC expansion, recruitment, and differentiation towards a number of different cell lineages. This study reports that ECM-directed cross-talk between PDGFR-β and alpha5β1 integrin controls the migration of MSCs. Cell adhesion to fibronectin induced integrin alpha5β1-dependent phosphorylation of PDGFR-β in the absence of growth factor stimulation. Phosphorylated PDGFR-β co-immunoprecipitated with integrin alpha5 and co-localised with alpha5β1 in a transient tidemark of focal adhesions. Adhesion to fibronectin also strongly potentiated platelet-derived growth factor (PDGF)-BB-stimulated PDGFR-β phosphorylation, in an alpha5β1-dependent manner. PDGFR-β-activated phosphatidylinositol 3 ́-kinase (PI3-kinase) and Akt activity, actin reorganisation and cell migration were all regulated by fibronectin engagement of alpha5β1 integrin. This synergistic relationship between integrin alpha5β1 and PDGFR-β is a fundamental determinant of mesenchymal cell migration. Thus, fibronectin-rich matrices can prime PDGFR-β to recruit mesenchymal cells at sites of tissue remodelling.

No description available.

Eukaryotic cell chemotaxis, or directed cell migration in response to a chemoeffector gradient, plays a central role in many important biological process such as wound healing, cancer metastasis, and embryogenesis. In vivo, cells migrate on fibrous ECM, but chemotaxis studies are typically conducted on flat substrates which fail to recapitulate ECM or 3D gel environments with heterogeneous and poorly defined biophysical properties. To address these challenges, this thesis focused on developing a microfluidic assay device which utilizes a reductionist approach to study single cell chemotaxis on aligned, suspended ECM-mimicking nanofibers. The device is comprised of a network of microfluidic mixing channels which produce a temporally invariant, linear chemical gradient over nanofiber scaffolds in an observation channel. The microfluidic device design was guided by a numerical model and validated with experimental testing. This device was used to study mouse embryonic fibroblast NIH/3T3 response to platelet derived growth factor (PDGF) on flat polystyrene and suspended, polystyrene nanofibers with small (15 μm), and large (25 μm) spacing. Cell aspect ratio is lowest for flat polystyrene (spread morphology) and highest for large-spaced fibers (spindle morphology). Cells migrating on fibers begin to show a chemotaxis response to a PDGF gradient 10 times shallower than that required for chemotaxis response on a flat substrate. Furthermore, cells with spindle morphology maintain a robust and strong response over a broad range of chemoattractant concentration. These cells also had a 45% increase in speed and 26% increase in persistence over cells on flat polystyrene. The findings of this thesis suggest that 2D substrates may not be sufficient for studying physiologically relevant chemotaxis. / Master of Science

Oligodendrocytes derived in the laboratory from stem cells have been proposed as a treatment for acute and chronic injury to the central nervous system (CNS). Platelet-derived growth factor-receptor alpha (PDGFRÑ)w signaling is known to play an important role for regulation of oligodendrocyte progenitor cell numbers both during development and adulthood. Here, we analyze the effect of PDGFRÑ signaling on CNS stem cells derived from embryonic day 13.5 murine cortex and cultured in monolayer. Fetal and adult CNS stem cells express PDGFRÑ, and PDGF-AA treatment increases viability and proliferation of these cells. In the absence of insulin, this effect of PDGF-AA is very clear. Consistent with this result, PDGF-AA strongly stimulates glycolytic rate. PDGF-AA treatment rapidly induces morphological changes in the cells although the cells maintain expression of a wide range of precursor markers. We show that a brief exposure to PDGF-AA rapidly and efficiently induces oligodendrocytes from CNS stem cells. Our data suggest that phosphoinositide kinase-3 (PI3K)/Akt, mitogen-activated protein/extracellular signal-regulated kinase kinase/extracellular signal-related kinase (MEK/Erk), mammalian target of rapamycin (mTOR) regulate survival, proliferation, glycolytic rate, and oligodendrogliogenesis induced by PDGF-AA. By treating with PDGF-AA, progenitor cells directly from embryonic cortex can be expanded and differentiated into oligodendrocytes with high efficiency. Our results show that PDGF-AA promotes oligodendrocyte progenitor generation from CNS stem cells and supports their survival and proliferation. The derivation of oligodendrocytes demonstrated here may support the safe and effective use of stem cells in the development of new therapies targeting this cell type.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 106-135).

Thrombozyten enthalten und sezernieren eine Vielzahl von Wachstumfaktoren, deren Mitwirkung an der Knochenbildung und –regeneration als gesichert gilt. Platelet-rich plasma (PRP) enthält eine hohe Thrombozytenkonzentration und somit auch dementsprechend hohe Spiegel von Wachstumsfaktoren. Ziel dieser Arbeit war eine Evaluation des Einflusses von PRP auf die Qualität und Quantität der interkorporellen knöchernen Fusion im Rahmen der ventralen Spondylodese von Wirbelkörperverletzungen mit Cage-Implantaten und autologer Spongiosa. In einer prospektiven Studie wurden 15 Patienten mit traumatischer Fraktur der BWS oder LWS ventral mit einem Cage-Implantat und autologer Spongiosa stabilisiert. Indikationsabhängig wurden additiv dorsale Fixateur interne und/oder ventrale Plattensysteme implantiert. Intraoperativ erfolgte die Kombination der autologen Spongiosa mit PRP. Dieses wurde direkt perioperativ aus max. 110 ml venösem Eigenblut des Patienten mit dem kommerziell erhältlichen GPS™-System (Biomet Deutschland GmbH, Berlin) hergestellt. Als Kontrollgruppe fungiert ein zufällig ausgewähltes Kollektiv von 20 Patienten mit traumtischer BWS- oder LWS-Fraktur. Diese wurden ebenfalls ventral mit Cage und autologer Spongiosa sowie zusätzlichen Implantaten stabilisiert, jedoch ohne den Einsatz von PRP. Im Rahmen der Nachbehandlung wurden nach durchschnittlich 8,33 Monaten (PRP-Gruppe) und 12,5 Monaten (Kontrolle) Computertomographien der instrumentierten Wirbelsäulenregion im Knochenfenster angefertigt. Anhand dieser wurde der Fusionsfortschritt exemplarisch für den linkslateralen Auftragungsbereich von Spongiosa bzw. Spongiosa/PRP um den Cage qualtitativ und quantifizierend mittles Volumetrie und Densitometrie (HU) erfasst. Es zeigte sich qualtitaiv bei 20% der PRP-Gruppe sowie 30% der Kontrollgruppe keine oder nur minimale linkslaterale Verknöcherung. Jeweils 40% wurden als durchgehend fusioniert klassifiziert. Quantifizierend ergab sich für beide Gruppen ein nahezu identischer mittlerer Volumenanteil > +100 HU (56,5 bzw. 56,6%) am linkslateralen Gesamtvolumen. Der Volumenanteil > +500 HU beträgt in der Kontrollgruppe 23,57% in der PRP-Gruppe hingegen 29,33%. Die absolute Dichte der Teilvolumina zeigt einen signifikant höheren Durchschnitsswert in der PRP-Gruppe (639,7 HU zu 514,2 HU) sowie nicht signifikant höhere Werte im Teilvolumen > +500 HU (930,7 HU zu 846 HU). Aus den VAS-Scores konnte für den gewählten Nachuntersuchungzeitraum kein signifikanter Unterschied im subjektiven, patientenbezogenen Outcome festgestellt werden. Insgesamt zeigt sich ein Trend, demnach der Einsatz von PRP eine Verbesserung der autologen Spongiosaplastik und damit der Verknöcherung um den Cage ermöglicht. Der bei Etablierung des Konzepts thrombozytärer Wachtsumsfaktoren-konzentrate zur Verbesserung der Knochenheilung erhoffte deutliche, klinische Effekt bleibt jedoch aus. / The effects of PRP were monitored by performing a controlled cohort study of patients undergoing an anterior spinal fusion. One group was treated with the addition of PRP. The growth factors contained within the blood platelets are known to play an important role in the new formation of bone following fractures or the implantation of bone grafts. But the results following the use of platelet-rich plasma in spinal fusion are not yet published. The study involved a group of 15 patients, who had suffered an injury of the thoracic or lumbar spine and had undergone an anterior fusion using cages. They had received an additional posterior stabilisation and/or anterior implants as well as bone graft combined with PRP. A control group made up of 20 patients received a similar treatment, but without the addition of PRP. A CT-Scan was performed of all patients during follow-up examinations. The area on the left side of the cage, where the bone graft with or without PRP had been applied, was analysed and the patients were divided into three classes, depending upon the rate of fusion: Complete fusion, incomplete fusion and no/minimal ossification. In cases, which were classified as complete or incomplete ossification, an additional CT volumetry and densitometry was performed. The patient-referred outcome was documented using the VAS spinal score. In both groups 40% of the patients had reached a complete fusion in the CT-Scans. No or minimal fusion was documented in 20% of the PRP group and 30% of the control group. When measuring the density within the newly formed bone mass, both groups showed nearly identical percentages with a density of over 100 Hounsfield units (HU). The share of bone with a density of over+500 HU was 29.33% in the PRP group) and 23.57% in the control group. Within the partition of over +100 HU the absolute density was significantly higher in the PRP group (639.7 vs. 514.2 HU). Similar results could be shown within the partition of over +500 HU (930.7 vs. 846 HU). The VAS-Scores showed no significant differences between the two groups. The additional application of autologous PRP involves very little risk for the patients. The study implies, that the use of PRP provides a faster fusion and higher density values within the fusion mass. A clear advancement in spinal fusion in terms of a clinical benefit remains questionable.

Tang Yin Nei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves xv-xxv). / Abstracts in English and Chinese. / ACKNOWLEDGEMENT --- p.i / ABBREVIATIONS --- p.ii-iii / INDEX FOR FIGURES --- p.iv-v / INDEX FOR TABLES --- p.vi / ABSTRACT (Chinese and English) --- p.vii-xi / TABLE OF CONTENTS --- p.xii-xiv / Chapter CHAPTER I 226}0ؤ --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.2 / Chapter 1.2 --- Tendon / Chapter 1.2.1 --- Structure and function --- p.3 / Chapter 1.2.2 --- Tendon fibroblast --- p.6 / Chapter 1.2.3 --- Components of the extracellular matrix --- p.7 / Chapter 1.2.3.1 --- Collagen --- p.8 / Chapter 1.2.3.2 --- Proteoglycan --- p.9 / Chapter 1.2.3.3 --- Non-collagenous structural glycoprotein --- p.10 / Chapter 1.3 --- Inflammation disorders of tendon / Chapter 1.3.1 --- Inflammation --- p.11 / Chapter 1.3.2 --- Treatment --- p.12 / Chapter 1.3.2.1 --- Glucocorticoid as an anti-inflammatory agent --- p.12 / Chapter 1.3.2.2 --- Dexamethasone --- p.14 / Chapter 1.3.3 --- Clinical occurrence of tendon rupture --- p.15 / Chapter 1.3.4 --- Animal research related to glucocorticoids and tendon rupture --- p.18 / Chapter 1.4 --- Platelet-derived growth factor isoform B (PDGFBB) / Chapter 1.4.1 --- Structure and function --- p.21 / Chapter 1.4.2 --- PDGFbb effects on connective tissue --- p.22 / Chapter CHAPTER II 226}0ؤ --- AIM OF THE STUDY --- p.23 / Chapter 2.1 --- Limitations of the past researches --- p.24 / Chapter 2.2 --- Hypothesis of this study --- p.25 / Chapter 2.3 --- Objectives --- p.26 / Chapter 2.4 --- Long term significance --- p.26 / Chapter CHAPTER III 226}0ؤ --- METHODOLOGY --- p.27 / Chapter 3.1 --- Chemicals and materials used / Chapter 3.1.1 --- Chemicals --- p.28 / Chapter 3.1.2 --- Materials --- p.28 / Chapter 3.2 --- Specimen collection and preparation / Chapter 3.2.1 --- Collection --- p.29 / Chapter 3.2.2 --- Preparation and isolation --- p.30 / Chapter 3.2.3 --- Cell culture --- p.31 / Chapter 3.3 --- Reagent preparation / Chapter 3.3.1 --- Charcoal-stripped serum --- p.32 / Chapter 3.3.2 --- Phenol-red free DMEM --- p.33 / Chapter 3.3.3 --- MTT --- p.33 / Chapter 3.3.4 --- Dexamethasone --- p.34 / Chapter 3.3.5 --- PDGFbb --- p.34 / Chapter 3.3.6 --- Trypan blue --- p.35 / Chapter 3.3.7 --- TCA/Tannic acid --- p.35 / Chapter 3.3.8 --- Collagenase buffer --- p.35 / Chapter 3.4 --- Morphology / Chapter 3.4.1 --- Inverted phase contrast light microscopy --- p.36 / Chapter 3.4.2 --- Scanning electron microscopy --- p.36 / Chapter 3.5 --- Biological assays / Chapter 3.5.1 --- "MTT (3-[4,5-Dimethylthiazol-2-yl]2,5-diphenyltetrazolium bromide) assay" --- p.38 / Chapter 3.5.1.1 --- Correlation between MTT assay and trypan blue dye method --- p.38 / Chapter 3.5.1.2 --- Growth kinetics for tendon fibroblasts --- p.41 / Chapter 3.5.1.3 --- Cell viability --- p.43 / Chapter 3.5.2 --- Brdu (5-bromo-2'-deoxyuridine) assay --- p.44 / Chapter 3.5.3 --- Flow cytometry --- p.45 / Chapter 3.5.4 --- Apoptosis --- p.47 / Chapter 3.5.5 --- 3H-Proline incorporation assay --- p.48 / Chapter 3.5.6 --- 35Sulfate incorporation assay --- p.51 / Chapter 3.5.7 --- Immunocytochemistry (PDGF-β receptor) --- p.54 / Chapter 3.6 --- Statistical analysis / Chapter 3.6.1 --- Dose-response curve of dexamethasone on cell viability and proliferation --- p.55 / Chapter 3.6.2 --- Comparison among various treatments of fibroblasts --- p.55 / Chapter CHAPTER I´Vؤ --- RESULTS --- p.56 / Chapter 4.1 --- In vitro effect of dexamethasone on rat tendon fibroblasts / Chapter 4.1.1 --- Viable cell number between two sexes --- p.57 / Chapter 4.2 --- In vitro effect of dexamethasone and PDGFBB on human tendon fibroblasts / Chapter 4.2.1 --- Gross morphology --- p.58 / Chapter 4.2.2 --- Cell cycle --- p.60 / Chapter 4.2.3 --- Apoptosis --- p.61 / Chapter 4.2.4 --- Viable cell number / Chapter 4.2.4.1 --- Effect of dexamethasone --- p.62 / Chapter 4.2.4.2 --- Effect of PDGFBB --- p.63 / Chapter 4.2.5 --- Cell proliferation / Chapter 4.2.5.1 --- Effect of dexamethasone --- p.65 / Chapter 4.2.5.2 --- Effect of PDGFbb --- p.67 / Chapter 4.2.6 --- Collagen synthesis --- p.68 / Chapter 4.2.7 --- Proteoglycan synthesis --- p.72 / Chapter 4.2.8 --- PDGF-rβ expression --- p.74 / Chapter CHAPTER V 226}0ؤ --- DISCUSSION --- p.75 / Chapter 5.1 --- Dexamethasone and PDGFBB induced change of cell morphology --- p.77 / Chapter 5.2 --- Dexamethasone retarded cell growth of human tendon fibroblast --- p.80 / Chapter 5.3 --- Dexamethasone inhibited collagen synthesis --- p.82 / Chapter 5.4 --- Dexamethasone inhibited proteoglycan synthesis --- p.86 / Chapter 5.5 --- PDGFbb could counteract the inhibitory effects of dexamethasone --- p.88 / Chapter 5.6 --- Expression of PDGF-(3 receptor is regulated by dexamethasone and PDGFBB --- p.90 / Chapter 5.7 --- Limitations of this study / Chapter 5.7.1 --- Not enough sample to differentiate different between two sexes --- p.92 / Chapter 5.7.2 --- Small sample size and few assays --- p.92 / Chapter 5.7.3 --- Limitations of the cell culture model --- p.93 / Chapter 5.7.4 --- Difficult to further in vivo study on human --- p.93 / Chapter 5.8 --- Contributions of this study / Chapter 5.8.1 --- Improve the limitation of the past research --- p.94 / Chapter 5.8.1.1 --- Human tendon specimen --- p.94 / Chapter 5.8.1.2 --- In vitro system --- p.94 / Chapter 5.8.2 --- Understand the effect of dexmaethasone on human tendon fibroblasts --- p.95 / Chapter 5.8.3 --- Counteract the deleterious effects of dexamethasone by PDGFBB --- p.95 / Chapter CHAPTER VÍؤ --- CONCLUSION & FUTURE STUDY --- p.96 / Chapter 6.1 --- Conclusion --- p.97 / Chapter 6.2 --- Future study --- p.98 / Chapter 6.2.1 --- Study the balance between matrix synthesis and degradation --- p.98 / Chapter 6.2.2 --- Determine collagen typing --- p.99 / Chapter 6.2.3 --- Further explore the effect of glucocorticoid in organ culture model --- p.100 / Chapter 6.2.4 --- Investigate molecular mechanism of dexamethasone and PDGFBB --- p.100 / REFERENCES --- p.xv-xxv / APPENDIX --- p.xxvi

Platelet-derived microparticles, released as a result of platelet activation, promote coagulation through the surface exposure of phosphatidylserine, acting as the catalytic site for the conversion of prothrombin to thrombin by the activated coagulation factors X and V. Although elevated numbers of circulating platelet-derived microparticles can be detected in a number of clinical disorders, the methods for the detection of these microparticles are far from standardised. In addition, recent reports have also speculated that not all microparticles may expose phosphatidylserine, demonstrating that the binding of Annexin V, a phosphatidylserine-specific binding protein, is not detectable on a population of microparticles. The initial stage of this thesis was to establish a flow cytometric method for the detection and enumeration of microparticles based on their capacity to bind Annexin V and to utilise this assay to investigate a number of the issues that have limited assay standardisation. The assay could be performed on either stimulated or unstimulated plasma or whole blood samples. Interestingly, plasma microparticle counts were significantly higher than whole blood microparticle counts. The effects of centrifugation alone could not be attributed as the sole source of this discrepancy. The antigenic characteristics of platelet-derived microparticles were also investigated, with platelet-derived microparticles demonstrated to express the platelet glycoproteins CD31, CD41a, CD42a and CD61. Platelet-derived microparticles also expressed CD42b, and this expression was significantly decreased when compared to their progenitor platelets. The expression of the platelet activation markers CD62p, CD63, CD40L and PAC-1 was dependent upon the sample milieu, suggesting that the centrifugation conditions required to generate platelet-poor plasma may lead to artefactual increases in the expression of platelet activation markers. An investigation of the role of the GpIIb/IIIa complex on the formation of platelet-derived microparticles was also performed. A monoclonal antibody to the GpIIb/IIIa complex (Abciximab) significantly inhibited in vitro collagen-stimulated platelet-derived microparticle formation. Interestingly, platelets obtained from two subjects with impaired GpIIb/IIIa activation, demonstrated normal microparticle formation following collagen stimulation, suggesting that the presence of GpIIb/IIIa complex, but not its activation, is required for collagen-induced microparticle formation. A novel mechanism for microparticle formation was also investigated, with platelet-derived microparticles demonstrated to form in response to the sclerosing agents sodium-tetradecyl sulphate and polidocanol. Interestingly, the removal of plasma proteins by the washing of platelets left platelets more susceptible to sclerosant-induced microparticle formation, suggesting that plasma proteins may protect platelets from microparticle formation. The procoagulant activity of platelet-derived microparticles was also investigated using a novel coagulation assay (XACT) specific for the procoagulant phospholipid. An evaluation of this assay demonstrated a significant correlation between Annexin V binding microparticle counts and procoagulant activity in both whole blood and plasma samples. There was more procoagulant activity in whole blood samples than in plasma samples, suggesting that the procoagulant phospholipid activity was also associated with erythrocytes or leukocytes. To further investigate this phenomenon, a whole blood flow cytometric assay was developed to assess Annexin V binding to erythrocytes, leukocytes, platelets and microparticles. This assay demonstrated that a large proportion of Annexin V binding (51.0%) was associated with erythrocytes. Interestingly, a proportion of the Annexin V binding erythrocytes (24.5%) and leukocytes (78.8%) were also associated with platelet CD61 antigen, suggesting that they also bound a platelet or platelet-derived microparticle. The effect of sample anticoagulant on microparticle procoagulant activity was investigated. Microparticle counts were most stable in EDTA anticoagulated samples, but were stable in sodium citrate for up to 15 minutes following sample collection. The procoagulant activity of microparticles was significantly inhibited by EDTA in collagen-stimulated platelet-rich plasma samples, when compared to sodium citrate anticoagulated samples. Although the initial method used to investigate microparticles was based upon their ability to bind Annexin V, it was consistently observed that a large proportion of events in the size region of a microparticle were Annexin V negative. An investigation was therefore commenced into the procoagulant activity of microparticles based on their capacity to bind Annexin V. The presence of Annexin V negative microparticles was confirmed by flow cytometry and the proportion of microparticles that bound Annexin V was dependent upon type of agonist used to stimulate microparticle formation. Varying the assay constituents (calcium concentration / Annexin V concentration / buffer type) did not alter the proportion of Annexin V binding microparticles. When compared to Annexin V positive microparticles, Annexin V negative microparticles expressed significantly higher levels of CD42b on their surface, but possessed significantly decreased expressions of CD62p, and CD63. A significant correlation between the percentage of Annexin V binding and XACT procoagulant activity was found (p=0.03). Furthermore, Annexin V binding inhibited greater than 98% of procoagulant phospholipid activity, suggesting that Annexin V binding was a true reflection of procoagulant activity. Microparticles could be sorted using either a flow cytometric or magnetic sorting strategy. By electron microscopy, Annexin V negative events isolated following magnetic sorting were vesicular structures and not small platelets or the remnants of activated platelets. In summary, this thesis has demonstrated the ability of the flow cytometer and XACT assays to detect microparticles and their procoagulant activity. It has also shown that the use of Annexin V to detect microparticles may warrant further investigation.