As graft source for lymphoma or leukemia treatment, hematopoietic stem and progenitor cells (HSPCs) have been the focus of translational medicine for decades. HSPCs are defined by their self-renewing capacity and their ability to give rise to all mature blood cells. They are found anchored to a specialized microenvironment in the bone marrow (BM) called the hematopoietic niche. HSPCs can be enriched by sorting them based on the presence of the surface antigen CD34 before clinical or tissue engineering use. As these cells represent a minority in most graft sources and the amount of applicable cells is limited, ex vivo expansion-cultures were established using cytokine cocktails or small molecules. However, in vitro culture of HSPCs as suspension-cultures result in heterogeneous cell populations with undefined cellular identities. In the BM niche, HSPCs are not exclusively maintained by cytokines but also by cell-matrix adhesions mediated by integrins (ITGs). Thus, β1 and β2 ITGs were found to promote initial contact of HSPCs with mesenchymal stromal cells (MSCs) and ITGβ3 expression was shown to be a marker for long-term repopulating HSPCs in vivo. Consequently, ex vivo remodeling of the BM niche using co-cultures of HSPCs and niche cells like MSCs came into spotlight and was proven to be a promising tool for stem cell expansion. However, in clinical and research applications, direct contact of two cell populations necessitates HSPC post-culture purification. To address these problems, we established a novel culture method for remodeling the BM extra cellular stroma in vitro wherein we used decellularized extracellular matrix (ECM) scaffolds derived from immortalized mesenchymal stromal cells (SCP-1). Such scaffolds were found to be highly reproducible and served as in vitro niche for HSPCs by being more effective for the expansion of CD34+ cells, compared to classical suspension cultures. ECMs were shown to consist of multiple proteins including fibronectins, collagens, and a major niche chemokine responsible for BM homing and retention of HSPCs in vivo, namely, stromal derived factor 1 (SDF-1). SDF-1 is known to be secreted by MSCs and is anchored to matrix proteins. This reveals that ECM scaffolds produced by SCP-1 cells are a naïve reconstructed microenvironment. When CD34+ cells were seeded, only around 20% of the cells adhered to the provided ECM scaffold. These cells recognized SDF-1 via C-X-C chemokine receptor type 4 (CXCR-4), as shown by laser scanning confocal microscopy. Thus, adhesive sides as they are present in the BM niche are provided. However, CD34+ cells isolated from G-CSF mobilized peripheral blood of healthy donors were found to be heterogenous with respect to adhesion capacity. Nonetheless, it was similar to HSPC co-cultures with SCP-1 cells as feeder layer. Therefore, we separated and analyzed two cell fractions, the adherent (AT-cells) and the non- adherent supernatant (SN-cells) cells. Other signals provided by the BM extracellular stroma to HSPCs are physical cues that control HSPC fate. HSPCs sense these physical features through focal contacts and accordingly remodel their morphological and biomechanical properties. Using real-time deformability cytometry (RT-DC) to uncover biomechanical phenotypes of freshly isolated HSPCs, SN-cells, AT-cells, and classical suspension cultured HSPCs in plastic culture dishes (PCD) were analyzed. We found freshly isolated cells to be less deformable and small. AT-cells displayed actin polymerization to stress fibers, and exhibited a stiffer mechanical phenotype compared to PCD-cultured or SN-cells. This might constitute the first hint of functional adaptation. Integrins are known to establish mechanosensing focal contacts. Thus, we analyzed ITG surface expression and identified ITGαIIb, ITGαV, and ITGβ3 to be enriched on AT-cells compared to freshly isolated cells or SN-cells. Active integrins need to form heterodimers consisting of one α- and one β subunit. Interestingly, the identified ITGs exclusively interact with each other to form RGD peptide receptors. RGD is a tripeptide consisting of the amino acids arginine, glycine, and aspartic acid and was identified as an adhesion sequence within fibronectin and other extracellular proteins. Consequently, we could confirm an important role for ITGαVβ3 in HSPC- ECM interaction with respect to adhesion and migration. However, we also identified ITGβ3 expression on a subset of CD34+ cells either freshly isolated or ECM cultured cells, as a marker for erythrocyte differentiation. These findings demonstrate that, in vitro, the ECM compartment acts as a regulator of HSPC fate and portray mechanical recognition as a potent driver of differentiation. In this context, targeted modulation of ECM scaffolds could enhance cell-ECM interactions and accelerate stem cell expansion or differentiation. These modulations could also provide further insights into HSPC-niche regulation. We demonstrate that ECMs derived from osteogenic differentiated SCP-1 cells increase HSPC expansion but do not lead to increased cell adhesion. As ECM adhesion preliminary alters HSPC function, we aimed at developing ECM scaffolds with increased adhesion capacity. Using lentiviral transduction, we generated a stable knock down of fibulin-1 in SCP-1 cells. Fibulin-1 is an ECM protein known to form anti-adhesion sites with fibronectin. However, we failed to increase adherent cell numbers or enhance HSPC expansion in the fibulin-1 knock down ECMs. Taken together, SCP-1 cell-derived ECM protein scaffolds provide an in vitro niche for HSPCs capable of stem cell expansion. Integrin mediated signaling altered the biomechanical and functional properties of HSPCs and hints at suspension cultures as being inappropriate to study the physiological aspects of HSPCs. Targeted modulation of ECM scaffolds could theoretically generate suitable ex vivo environments with the capacity to gain detailed insight into HSPC regulation within their niche. This will enhance the functionality of new biomaterials and will lead to improved regenerative therapies like BM transplantation.:List of contents I List of figures IV List of tables VI Abbreviations VII 1 Introduction 1 1.1 The stem cell microenvironment 3 1.1.1 The cellular endosteal bone marrow microenvironment 6 1.1.1.1 Mesenchymal stem/stromal cells 7 1.1.1.2 Hematopoietic stem and progenitor cells 8 1.1.2 Extracellular bone marrow microenvironment 10 1.1.2.1 Extracellular matrix 11 Chemokines and Cytokines 12 Cell adhesion to ECM 13 1.2 Native ex vivo ECM scaffolds 16 2 Aim of the study 19 3 Materials and methods 21 3.1 Materials 21 3.1.1 Chemicals and reagents 21 3.1.2 Kits 23 3.1.3 Media 24 3.1.4 Antibodies 24 3.1.5 Primers, sh-RNA sequences, and vectors 25 3.1.6 Equipment 26 3.1.7 Software 27 3.2 Methods 27 3.2.1 Cell preparation and culture 27 3.2.1.1 Mesenchymal stromal cells 27 3.2.1.2 Hematopoietic stem cells 28 3.2.1.3 Single cell picked clone 1 (SCP-1) cells 28 3.2.2 Generation of surface immobilized ECM preparations 29 3.2.2.1 Surface functionalization 29 3.2.2.2 ECM preparation 29 3.2.3 Flow cytometry and fluorescent activated cell sorting 30 3.2.4 Cell cycle analyses 30 3.2.5 Proliferation analyses 31 3.2.6 Colony forming unit cell assay (CFU-GEMM) 31 3.2.7 Migration assays 31 3.2.7.1 Transwell migration 31 3.2.7.2 Live cell migration 32 3.2.8 Confocal laser scanning microscopy 32 3.2.9 Real-time deformability cytometry (RT-DC) 32 3.2.10 Molecular biological methods 33 3.2.10.1 RNA isolation, reverse transcription, and PCR 33 3.2.10.2 Lentiviral shRNA transduction 34 3.2.10.3 Western blot 35 3.2.10.4 ELISA 36 3.2.11 Statistical analysis 37 4 Results 38 4.1 Extracellular matrix scaffolds for HSPCs 38 4.1.1 ECM properties 39 4.1.2 HSPC survival in ECM and PCD cultures 40 4.1.3 HSPC expansion in ECM and PCD cultures 41 4.2 HSPC morphological and mechanical adaptation to ECM 44 4.2.1 Actin polymerization and polarization 45 4.2.2 Biomechanical phenotype 46 4.3 Bioactive SDF-1 is incorporated in ECM scaffolds 49 4.3.1 CXCR4 polarization towards ECM 50 4.4 HSPC integrin expression and migration 52 4.4.1 Integrin surface expression on HSPC subsets 52 4.4.2 Focal contact formation 53 4.4.3 Integrin activation via ECM adhesion 55 4.4.4 Clonogenicity of ECM cultured HSPCs 57 4.4.5 HSPC migration when attached to ECM scaffolds 60 4.4.5.1 Reduced migratory behavior via ITGαVβ3 inhibition 61 4.4.5.2 SDF-1 induces migration but not adhesion 64 4.5 Targeted modulation of ECM scaffolds 65 4.5.1 Fibulin-1 knock down in SCP-1 cells 66 4.5.2 HSPC support of fibulin-1 reduced ECM scaffolds 70 5 Discussion 73 5.1 SCP-1 cells as a source for ECM scaffold production 74 5.2 Cell adhesion and focal contact formation 75 5.3 HSPC multilineage potential 78 5.4 ECM scaffold modulation 79 6 Summary 83 7 Zusammenfassung 86 Bibliography 89 Danksagung 108 Anlagen 110 Erklärung zur Eröffnung des Promotionsverfahrens [Formblatt 1.2.1] 110 Erklärung zur Einhaltung rechtlicher Vorschriften [Formblatt 1.1] 110

Artificial lipid bilayers formed on solid surface supports are widespread model systems to study physical, chemical, as well as biological aspects of cell membranes and fundamental interfacial interactions. The approach to use a thin polymer film representing a cushion for lipid bilayers prevents incorporated membrane proteins from pinning to the support and mimics the native environment of a lipid bilayer in certain aspects of the extracellular matrix and intracellular structures. A key component for cell anchorage to extracellular fibronectin is the transmembrane adhesion receptor alpha(5)beta(1) integrin. Its transport dynamics and clustering behavior plays a major role in the assembly of focal adhesions, which mediate mechanical forces and biochemical signals of cells with their surrounding. The system investigated herein is envisioned to use extrinsically controlled stimuli-responsive polymer cushions to tune the frictional drag between polymer cushion and mobile membranes with incorporated integrins to actively regulate lipid membrane characteristics. To attain this goal, a temperature- and pH-responsive polymer based on poly(N-isopropylacrylamide) copolymers containing varying amounts of carboxyl-group-terminated comonomers at different aliphatic spacer lengths (PNIPAAm-co-carboxyAAM) was surface-grafted to a poly(glycidyl methacrylate) anchorage layer. The swelling transitions were characterized using atomic force microscopy, ellipsometry and quartz crystal microbalance with dissipation monitoring (QCM-D) and found to be tunable over a wide range of temperature and pH. In agreement with the behavior of the polymers in solution, longer alkyl spacers decreased the phase transition temperature T(P) and higher contents of carboxylic acid terminated comonomers increased T(P) at alkaline conditions and decreased T(P) at acidic conditions. Remarkably, the point where the degree of carboxyl group deprotonation balances the T(P)-lowering effect of the alkyl spacer was distinctive for each alkyl spacer length. These findings illustrate how the local and global balance of hydrophilic and hydrophobic interactions along the copolymer chain allows to adjust the swelling transition to temperatures below, comparable, or above those observed for PNIPAAm homopolymers. Additionally, it could be shown that surface-grafting leads to a decrease in T(P) for PNIPAAm homopolymers (7°C) and copolymers (5°C - 10°C). The main reason is the increase in local polymer concentration of the swollen film constrained by dense surface anchorage in comparison to the behavior of dilute free chains in solution. In accordance with the Flory-Huggins theory, T(P) decreases with increasing concentration up to the critical concentration. Biological functionalization of the PNIPAAm-co-carboxyAAm thin films was demonstrated for the cell adhesion ligand peptide cRGD via carbodiimide chemistry to mimic extracellular binding sites for the cell adhesion receptors integrin. The outcome of QCM-D measurements of cRGD-functionalized surfaces showed a maintained stimuli-responsiveness with slight reduction in T(P). A drying/rehydration procedure of a 9:1 lipid mixture of the cationic lipid dioleoyl-trimethylammoniumpropane (DOTAP) and the zwitterionic dioleoyl-phosphatidylcholine (DOPC) was utilized to form lipid bilayer membranes on PNIPAAm-co-carboxyAAM cushions. Fluorescence recovery after photobleaching (FRAP) revealed that lipid mobility was distinctively higher (6.3 - 9.6) µm2 s-1 in comparison to solid glass support ((3.0 - 5.9) µm2 s-1). In contradiction to the initial expectations, modulation of temperature and pH led to poor variations in lipid mobility that did not correlate with the PNIPAAm cushion swelling state. The results suggested a weak coupling of the lipid bilayer with PNIPAAm polymer cushions that can be slightly tuned by electrostatic interactions. The transmembrane adhesion receptor alpha(5)beta(1) integrin was reconstituted into liposomes consisting of DOPC/sphingomyelin/cholesterol 2:2:1 for the formation of polymer cushioned bilayers. PNIPAAm- co-carboxyAAM and maleic acid (MA) copolymers were used as cushions, both with the option for cRGD functionalization. On the MA copolymer cushions, fusion of proteoliposomes resulted in supported bilayers with mobile lipids as confirmed by FRAP. However, incorporated integrins were immobile. In an attempt to explain this observation, the medium-sized cytoplasmic integrin domain was accounted to hamper the movement by steric interactions with the underlying polymer chains in conjunction with electrostatic interactions of the cationic cytoplasmic domain with the oppositely charged MA copolymer. On the PNIPAAm-co-carboxyAAM cushion only a drying/rehydration procedure lead to bilayer formation. However, again the integrins were immobile, presumably due to the harsh treatment during preparation. Nevertheless, the results of the investigated set of PNIPAAm copolymer films suggest their application as temperature- and pH-responsive switchable layers to control interfacial phenomena in bio-systems at different physiological conditions. The PNIPAAm-co-carboxyAAm cushioned bilayer system represents a promising step towards extrinsically controlled membrane – substrate interactions.

Cell adhesion to extracellular matrix proteins mediates resistance to radio- and chemotherapy by activating integrin signaling. In addition, mutual and cooperative interactions between integrin and growth factor receptor signaling contribute to the cellular radiation response. Here, we investigate to which extend the crosstalk between β1 integrins and growth factor receptor signaling determines the cellular radiation response of fibroblasts by assessing clonogenic survival and cell cycling. By utilizing growth factor signaling competent and either β1 integrin wildtype GD25β1A fibroblasts or β1 integrin mutant, signaling incompetent GD25β1B fibroblasts, we show basal clonogenic survival to depend on growth factor receptor but not integrin signaling. Our data further suggest the cooperation between β1 integrins and growth factor receptors to be critical for enhancing the radiation-induced G2/M cell cycle block leading to improved clonogenic radiation survival. By pharmacological inhibition of EGFR and PI3K, we additionally show that the essential contribution of EGFR signaling to radiogenic G2/M cell cycle arrest depends on the co-activation of the β1 integrin signaling axis, but occurs independent of PI3K. Taken together, elucidation of the signaling circuitry underlying the EGFR/β1 integrin crosstalk may support the development of advanced molecular targeted therapies for radiation oncology.

Introduction: Targeted pharmaceuticals for labelling with radio-isotopes for very specific imaging (and possibly later for targeted therapy) play a major role in Theranostics which is currently an important topic in Nuclear Medicine as well as personalised medicine. There was a need for a very specific lung cancer radiopharmaceutical that would specifically be uptaken in integrin 3 expression cells to image patients using a Positron Emission Tomography- Computed Tomography (PET-CT) scanner. Background and problem statement: Cold kits of c (RGDyK)–SCN-Bz-NOTA were kindly donated by Seoul National University (SNU) to help meet Steve Biko Hospital’s need for this type of imaging. These cold kits showed great results internationally in labelling with a 0.1 M 68Ge/68Ga generator (t1/2 of 68Ge and 68Ga are 270.8 days and 67.6 min, respectively). However the same cold kits failed to show reproducible radiolabeling with the 0.6 M generator manufactured under cGMP conditions at iThemba LABS, Cape Town and distributed by IDB Holland, the Netherlands. Materials and methods: There was therefore a need for producing an in-house NOTA-RGD kit that would enable production of clinical 68Ga-NOTA-RGD in high yields from the IDB Holland/iThemba LABS generator. Quality control included ITLC in citric acid to observe labelling efficiency as well as in sodium carbonate to evaluate colloid formation. HPLC was also performed at iThemba LABS as well as Necsa (South African Nuclear Energy Corporation). RGD was obtained from Futurechem, Korea. Kit mass integrity was determined by testing labelling efficiency of 10, 30 and 60 μg of RGD per cold kit. The RGD was buffered with sodium acetate trihydrate. The original kits were dried in a desiccator and in later studies only freeze dried. Manual labelling was also tested. The radiolabelled in-house kit’s ex vivo biodistribution in healthy versus tumour mice were examined by obtaining xenografts. The normal biodistribution was investigated in three vervet monkeys by doing PET-CT scans on a Siemens Biograph TP 40 slice scanner. Results: Cold kit formulation radiolabeling and purification methods were established successfully and SOPs (standard operating procedures) created. HPLC results showed highest radiochemical purity in 60 μg cold kit vials. 68Ga-NOTA-RGD showed increased uptake in tumours of tumour bearing mouse. The cold kit also showed normal distribution according to literature with fast blood clearance and excretion through kidneys into urine, therefore making it a suitable radiopharmaceutical for clinical studies. Conclusion: The in-house prepared cold kit with a 4 month shelf-life was successfully tested in mice and monkeys. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

Introduction: Targeted pharmaceuticals for labelling with radio-isotopes for very specific imaging (and possibly later for targeted therapy) play a major role in Theranostics which is currently an important topic in Nuclear Medicine as well as personalised medicine. There was a need for a very specific lung cancer radiopharmaceutical that would specifically be uptaken in integrin 3 expression cells to image patients using a Positron Emission Tomography- Computed Tomography (PET-CT) scanner. Background and problem statement: Cold kits of c (RGDyK)–SCN-Bz-NOTA were kindly donated by Seoul National University (SNU) to help meet Steve Biko Hospital’s need for this type of imaging. These cold kits showed great results internationally in labelling with a 0.1 M 68Ge/68Ga generator (t1/2 of 68Ge and 68Ga are 270.8 days and 67.6 min, respectively). However the same cold kits failed to show reproducible radiolabeling with the 0.6 M generator manufactured under cGMP conditions at iThemba LABS, Cape Town and distributed by IDB Holland, the Netherlands. Materials and methods: There was therefore a need for producing an in-house NOTA-RGD kit that would enable production of clinical 68Ga-NOTA-RGD in high yields from the IDB Holland/iThemba LABS generator. Quality control included ITLC in citric acid to observe labelling efficiency as well as in sodium carbonate to evaluate colloid formation. HPLC was also performed at iThemba LABS as well as Necsa (South African Nuclear Energy Corporation). RGD was obtained from Futurechem, Korea. Kit mass integrity was determined by testing labelling efficiency of 10, 30 and 60 μg of RGD per cold kit. The RGD was buffered with sodium acetate trihydrate. The original kits were dried in a desiccator and in later studies only freeze dried. Manual labelling was also tested. The radiolabelled in-house kit’s ex vivo biodistribution in healthy versus tumour mice were examined by obtaining xenografts. The normal biodistribution was investigated in three vervet monkeys by doing PET-CT scans on a Siemens Biograph TP 40 slice scanner. Results: Cold kit formulation radiolabeling and purification methods were established successfully and SOPs (standard operating procedures) created. HPLC results showed highest radiochemical purity in 60 μg cold kit vials. 68Ga-NOTA-RGD showed increased uptake in tumours of tumour bearing mouse. The cold kit also showed normal distribution according to literature with fast blood clearance and excretion through kidneys into urine, therefore making it a suitable radiopharmaceutical for clinical studies. Conclusion: The in-house prepared cold kit with a 4 month shelf-life was successfully tested in mice and monkeys. / MSc (Pharmaceutics), North-West University, Potchefstroom Campus, 2014

The neuropilin (Nrp) family consists of multifunctional cell surface receptors with critical roles in a number of different cell and tissue types. A core aspect of Nrp function is ligand-dependent cellular adhesion and migration, where it controls the multistep process of cellular motility through integration of ligand binding, receptor coupling and signaling via the coordinated action of its extracellular and intracellular domains. While Nrp regulates cellular adhesion and motility in the cardiovascular and nervous systems under physiological conditions, the emerging pathological role of Nrp in tumor cell migration and metastasis has been identified and provides motivation for continued efforts toward developing Nrp inhibitors. At the molecular level, the role of Nrp in adhesion and migration is intimately connected to the control of adhesive interactions and cytoskeletal reorganization. The adhesive “interactome” for Nrp draws much attention because of its lack of enzymatic activity and inability to transduce signals on its own. It is an active area of research and is still expanding dramatically. Nrp has been well defined as a co-receptor for vascular endothelial growth factor receptor (VEGFR)/vascular endothelial growth factor (VEGF) signaling through enhancing receptor-ligand interaction in angiogenesis. Here, we contribute to this concept through characterization in more biochemical detail about Nrp-1/VEGF physical interactions. VEGF has been shown to compete with Sema3 for binding to Nrp-1 b1 ligand binding pocket. This competition fine-tunes VEGF-induced angiogenesis. Our data provides a molecular mechanism for high affinity Sema3F binding to Nrp-1 in the b1 domain. As to the VEGFR-independent function, Nrp/integrin association has been demonstrated. The functional integration has been shown for Nrp/integrin in angiogenic sprouting. Both proteins are highly expressed in endothelial tip cells to mediate endothelial cell migration during angiogenesis and knockdown of either one in mice leads to embryonic lethality due to similar defects in vascular development. To identify the structure and function correlation, we characterized in more detail about Nrp-1/integrin physical interactions with biochemical and cell-based assays. Through an integrated approach of biochemical, molecular and cellular methods, we defined the direct physical interactions between Nrp-1 and integrins. We have also extended this work to demonstrate the functional importance and contribution of the interactions in integrin-mediated cell adhesion on extracellular matrix (ECM) in angiogenesis and platelet function during wound healing and provide a molecular basis for the integration of Nrps/integrins in cell migration, adhesion to ECM, breast cancer initiation and breast cancer stem cell fate determination.

Η πλειοτροπίνη (PTN) αποτελεί έναν αυξητικό παράγοντα με ποικίλες δράσεις και σημαντικό ρόλο στην ανάπτυξη όγκων και την αγγειογένεση. Διάφοροι υποδοχείς αλληλεπιδρούν με την ΡΤΝ και διαμεσολαβούν τις βιολογικές της δράσεις, όπως η Ν-συνδεκάνη, ο ALK (κινάση αναπλαστικού λεμφώματος) και ο RPTPβ/ζ (υποδοχέας με δράση φωσφατάσης τυροσίνης β/ζ). Η ερευνητική μας ομάδα έχει δείξει σε προηγούμενη μελέτη ότι η ικανότητα της PTN να επάγει κυτταρική μετανάστευση εξαρτάται από το σχηματισμό ενός λειτουργικού συμπλόκου που αποτελείται από τον RPTPβ/ζ και την ιντεγκρίνη ανβ3. Η πολυ-λειτουργική πρωτεΐνη νουκλεολίνη (NCL), η οποία υπερεκφράζεται στην επιφάνεια ενεργοποιημένων ενδοθηλιακών και καρκινικών κυττάρων και διαμεσολαβεί τις διεγερτικές δράσεις διαφόρων αγγειογενετικών παραγόντων, έχει επίσης προταθεί ως υποδοχέας χαμηλής συγγένειας για την ΡΤΝ, με άγνωστες όμως λειτουργίες. Στην παρούσα μελέτη δείξαμε, με τη χρήση μεθόδων ανοσοκατακρήμνισης-ανοσοαποτυπώματος, διπλού ανοσοφθορισμού και προσδιορισμού αλληλεπίδρασης λόγω εγγύτητας, ότι η PTN αλληλεπιδρά άμεσα με τη NCL. Η αλληλεπίδραση αυτή περιλαμβάνει πρόσδεση της αμινοτελικής περιοχής της ΡΤΝ (αμινοξέα: 16-24) στην κεντρική περιοχή της NCL (αμινοξέα: 308-645). Μείωση της έκφρασης της NCL με siRNA ή λειτουργική αναστολή της μεμβρανικής NCL από το πεπτίδιο 5(KPR)TASP ανέστειλε πλήρως την επαγόμενη από ΡΤΝ μετανάστευση ενδοθηλιακών κυττάρων. Με αφετηρία την παρατήρηση ότι ο εντοπισμός της NCL στην κυτταρική επιφάνεια ανιχνεύθηκε μόνο σε κύτταρα που εκφράζουν την ανβ3, και πραγματοποιώντας πειράματα ανοσοφθορισμού και βιοχημικές μελέτες σε κύτταρα με γενετικά τροποποιημένη έκφραση των υπό μελέτη μορίων, δείξαμε ότι ο εντοπισμός της NCL στην πλασματική μεμβράνη εξαρτάται από τη φωσφορυλίωση της β3 στην τυροσίνη 773 μέσω ενεργοποίησης του RPTPβ/ζ και της c-src. Καθοδικά της ανβ3, η PI3K συμμετέχει σε αυτή τη δράση. Ο VEGF165 που επίσης επάγει το μεμβρανικό εντοπισμό της NCL, δρα μέσω δέσμευσης στον RPTPβ/ζ και ενεργοποίησης του σηματοδοτικού μονοπατιού RPTPβ/ζ/c-src/ανβ3. Η περιοχή δέσμευσης στους υποδοχείς VEGFR-1 και VEGFR-2 ή η περιοχή δέσμευσης στην ηπαρίνη στο μόριο του VEGF165 δεν εμπλέκονται στον επαγόμενο από VEGF165 εντοπισμό της NCL στην κυτταρική μεμβράνη. Εκτός από την PI3K, στη δράση του VEGF165 καθοδικά της ανβ3 εμπλέκεται και η κινάση p38, η ενεργοποίηση της οποίας είναι ανεξάρτητη από τον RPTPβ/ζ και τη φωσφορυλίωση της β3 στις τυροσίνες 773 ή 785, και φαίνεται να ανήκει σε μονοπάτι που ενεργοποιείται παράλληλα και που παραμένει αδιευκρίνιστο. Μηχανιστικά, η NCL βρέθηκε να αλληλεπιδρά άμεσα με την ανβ3, τον RPTPβ/ζ, τον VEGF165 και τον VEGFR-2, αλλά επηρεάζει τον ενδοκυτταρικό εντοπισμό μόνο του RPTPβ/ζ και της PTN. Θετική συσχέτιση παρατηρήθηκε ως προς την έκφραση της μεμβρανικής NCL και της ανβ3 σε μικροσυστοιχίες ιστών προερχόμενων από ανθρώπινα γλοιοβλαστώματα. Τέλος, βρέθηκε ότι το μονοκλωνικό αντίσωμα anti-C23 και τα πεπτίδια που στοχεύουν τη μεμβρανική NCL, 5(KPR)TASP, ΗΒ-19 και Nucant 6L, ανέστειλλαν σημαντικά τη μετανάστευση κυττάρων που εκφράζουν ανβ3, ενώ είχαν μικρή ή καθόλου δράση στη μετανάστευση κυττάρων που δεν εκφράζουν ανβ3 ή υπερεκφράζουν μετάλλαγμα της β3 με αντικατάσταση της κυτταροπλασματικής τυροσίνης 773 σε φαινυλαλανίνη. Συνολικά, από τα αποτελέσματα της παρούσας διατριβής προκύπτει ότι η έκφραση της ανβ3 και η φωσφορυλίωση της β3 στην τυροσίνη 773 καθορίζουν τον εντοπισμό της NCL στην κυτταρική επιφάνεια, καθοδικά του σηματοδοτικού μονοπατιού RPTPβ/ζ/c-src που συμμετέχει στην κυτταρική μετανάστευση που επάγεται τόσο από την ΡΤΝ, όσο και από τον VEGF165. Επίσης, φαίνεται ότι η έκφραση της ανβ3 θα μπορούσε να χρησιμοποιηθεί ως βιοδείκτης για τη χρήση ανταγωνιστών της μεμβρανικής NCL ως αντικαρκινικών παραγόντων. / Pleiotrophin (PTN) is a growth factor that plays a significant role on tumor growth and angiogenesis. Several receptors interact with PTN and mediate its biological actions, such as N-syndecan, anaplastic lymphoma kinase (ALK) and receptor protein tyrosine phosphatase beta/zeta (RPTPβ/ζ). Our group has previously shown that the ability of PTN to stimulate migratory responses depends on the formation of a functional complex consisting of RPTPβ/ζ and integrin ανβ3. The multifunctional protein nucleolin (NCL), which is over-expressed on the surface of activated endothelial and tumor cells and mediates the stimulatory actions of several angiogenic factors, has been also suggested as a low affinity receptor for PTN, however with unknown functions. In the present study, by using immunoprecipitation/Western blot analyses, double immunofluorescence and proximity ligation assays, we showed that PTN directly interacts with NCL. This interaction involves binding of the amino-terminal domain of PTN (amino acids: 16-24) to the central domain of NCL (amino acids: 308-645). Down-regulation of NCL by siRNA or blockage of cell surface NCL by its ligand 5(KPR)TASP completely abolished PTN-induced endothelial cell migration. Based on the observation that cell surface NCL localization was detected only in cells expressing ανβ3 and by performing immunofluorescence and biochemical studies in cells with genetically altered expression of the studied molecules, we demonstrated that cell surface NCL localization depends on the phosphorylation of β3 at Tyr773 through RPTPβ/ζ and c-src activation. Down-stream of ανβ3, PI3K activity is required for cell surface NCL localization. VEGF165 that also induces cell surface NCL localization acts through binding to RPTPβ/ζ and activation of the RPTPβ/ζ/c-src/ανβ3 signaling pathway. The receptor or the heparin binding sites on the VEGF165 molecule do not seem to be involved in this VEGF165 action. Apart from PI3K, in VEGF165-induced cell surface NCL localization, p38 that lays down-stream of ανβ3, is also involved. Activation of p38 is independent of RPTPβ/ζ and β3 Tyr773 or Tyr785 phosphorylation, and seems to belong to a parallel signaling pathway that remains unclear. Mechanistically, NCL was found to directly interact with ανβ3, RPTPβ/ζ, VEGF165 and VEGFR-2, but only affects the intracellular localization of RPTPβ/ζ and PTN. Positive correlation of cell surface NCL and ανβ3 expression was observed in human glioblastoma tissue arrays. Finally, the monoclonal antibody anti-C23 and the peptides targeting cell surface NCL, 5(KPR)TASP, HB-19 and Nucant 6L, significantly inhibited migration of cells expressing ανβ3 in the presence of serum, while they had a minor or no effect on cells lacking ανβ3 or over-expressing mutant β3 with replacement of cytoplasmic tyrosine 773 to phenylalanine. Collectively, these data suggest that ανβ3 expression and β3 phosphorylation at Tyr773 downstream of the RPTPβ/ζ/c-src signaling cascade determines the cell surface localization of NCL, which is required for cell migration induced by both PTN and VEGF165. Moreover, expression of ανβ3 could be used as a biomarker for the use of cell surface NCL antagonists as anticancer agents.

Bordetella pertussis is an important human pathogen that causes an infection disease called whooping cough. This gram-negative bacterium produces an adenylate cyclase toxin (CyaA) that recognizes an integrin receptor CD11b/CD18 present on the surface of myeloid phagocytes and delivers an adenylate cyclase (AC) domain into the cell cytosol. This thesis deals with the endocytic machinery of CyaA and its potential use as a specific marker for endocytosis of the CD11b/CD18 receptor molecule. Detoxified mutant of CyaA, CyaA-AC- , that has the capacity to promote calcium influx as well the potassium efflux, was shown to trigger activation of the integrin receptor CD11b/CD18 followed with endocytic uptake by clathrin-dependent pathway. On the other side, the inactive mutant CyaA-KP-AC- that is unable to provoke integrin activation was endocytosed by clathrin-independent pathway. These results suggest that the various endocytic pathways of the CD11b/CD18 are determined by different conformational states of the receptor molecule.

Ao longo da vida reprodutiva dos machos adultos, espermatozoides são formados pelas células-tronco espermatogoniais (SSCs, do inglês spermatogonial stem cells) por um processo conhecido como espermatogênese. O cultivo in vitro de SSCs abriu novas possibilidades para a transgenia, no entanto os protocolos requerem a adição de fatores de crescimento, o que encarece a manutenção dessas células por um tempo prolongado, fazendo da criopreservação de SSCs uma alternativa para esse problema. O fenótipo molecular de células-tronco espermatogoniais tem sido objeto de estudo nas últimas décadas. Uma das moléculas mais estudadas como marcador na caracterização de espermatogônias é a alfa-6 integrina. Baseado nestas informações, a seguinte hipótese foi proposta: SSCs que apresentam maior expressão de alfa-6 integrina são mais eficientes para modificações genéticas e colonização de túbulos seminíferos. Para testar essa hipótese, as SSCs murinas foram dissociadas de testículos de camundongos com 8 a 11 dias de idade. Essas células foram cultivadas in vitro, caracterizadas quanto sua morfologia, congeladas e incubadas com anticorpo anti-alfa-6 integrina para a purificação das SSCs por separação celular ativada por fluorescência (FACS). Células testiculares foram geneticamente modificadas com a inserção do gene marcador LacZ e o transplante através dos ductos eferentes foi padronizado. As Células germinativas testiculares foram dissociadas e cultivadas in vitro, porém a viabilidade foi aquém da desejada, inviabilizando as etapas de transformação, transplante e posterior avaliação histológica. Usando o marcador molecular alfa-6 integrina foi possível separar populações de células germinativas testiculares por FACS e a expressão gênica de ITGα6, GFRα1, Oct-4 e Thy-1 foi detectada por RT-PCR quantitativo. Em conclusão, não foi possível comprovar a eficiência de transdução e colonização em túbulos seminíferos por células-tronco espermatogoniais selecionadas com alfa-6 integrina. / Throughout the reproductive life of adult males, spermatozoa are formed from spermatogonial stem cells (SSCs) by a process known as spermatogenesis. The in vitro culture of SSCs created new possibilities for transgenesis, however the protocols require addition of growth factors, which increases the maintenance costs of these cells for a prolonged time, making of the cryopreservation of SSCs an alternative for this problem. The molecular phenotype of spermatogonial stem cells have been target of studies in recent decades. One of the most studied marker molecule in the characterization of spermatogonia is integrin alpha-6. Based on these informations, the following hypothesis was proposed: SSCs that show increased expression of integrin alpha-6 are more efficient for genetic modification and colonization of seminiferous tubules. In order to test this hypotesis, murine SSCs were dissociated from testes of 8 to 11 days old mice. These cells were in vitro cultured, characterized based on its morphology, frozen and incubated with anti-integrin alpha-6 antibody for the purification of SSCs by activated cell sorting fluorescence (FACS). Testicular cells were genetically modified with the insertion of the marker gene LacZ and transplantation through the efferent ducts was standardized. The testicular germ cells were dissociated and in vitro cultured, however viability was below expected, precluding the steps of transformation, transplantation and subsequent histological evaluation. Using molecular marker integrin alpha-6 it was possible to separate testicular germ cell populations by FACS and gene expression of ITGα6, GFRα1, Oct-4 and Thy-1was detected by quantitative RT-PCR. In conclusion, it was not possible to prove the efficiency of transduction and colonization in the seminiferous tubules by spermatogonial stem cells selected with alpha 6 integrin.

Background: Inadequate foetal growth cannot be remedied postnatally, leading to severe consequences for neonatal and adult development. Furthermore, sexual dimorphism in placental development has been suggested in humans although this remains poorly investigated in the pig. Hypotheses: Intrauterine Growth Restriction (IUGR) occurs due to aberrant conceptus attachment, which leads to alterations in angiogenesis and vascularity of the feto-maternal interface. Altered gene expression and vascularity will be observed at the feto-maternal interface in male foetuses compared to female foetuses. Increased apoptosis and decreased proliferation will be observed in the feto-maternal interface associated with the lightest foetuses compared to the closest to mean litter weight (CTMLW) foetuses. Aims: This thesis aimed to investigate the association between foetal size and sex and: integrin signalling; apoptotic and proliferation pathways; umbilical arterial (UA) blood flow; and angiogenesis and vascularity at the feto-maternal interface. This was performed by the collection of placental and endometrial samples associated with conceptuses or foetuses of different size (lightest and CTMLW) and sex at gestational day (GD) 18, 30, 45, 60 and 90. Conclusion This thesis has presented novel findings of associations between foetal size and sex, and placental and endometrial integrin signalling, apoptosis and proliferation, and angiogenesis and vascularity. Currently, this is the first suggestion in the literature that foetal size, and more intriguingly foetal sex, may have a strong influence on the activity of the endometrium. The mechanisms behind these findings warrant further investigation. Switches in the direction of differences at the feto-maternal interface between foetuses of different size were observed throughout gestation, notably between GD45 and 60, highlighting the dynamic nature of the feto-maternal interface and suggesting this as a potential window that could be manipulated by the industry to attempt to rescue the postnatal phenotype of IUGR piglets.