No description available.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 154-192).

Articular cartilage is an extraordinary tissue, allowing frictionless movements of articulated joints, and acting as a load-bearing cushion to protect joints from damage. Breakdown of articular cartilage may result in crippling diseases such as osteoarthritis (OA) and, since articular cartilage has a limited repair capacity, a greater understanding of the mechanisms of joint homeostasis and its response to injury are of great clinical need. In this project the hypothesis that endogenous mesenchymal stem cells (MSCs) may contribute to the healing process of a full-thickness articular cartilage defect was investigated by combining a mouse model of joint surface injury and repair with a nucleoside analogue labelling scheme in DBA/1 mice. Following injury, proliferative responses of nucleoside analogue-retaining cells were detected between 4 and 12 days post injury (dpi) in both the bone marrow and the synovial membrane of the knee joint. Phenotypic analysis of these label-retaining cells using immunofluorescence staining revealed an MSC-compatible phenotype (CD44+, CD105+, CD146+, PDGFRα+ and p75NGFR+), with differences observed between the two tissues in expression of CD105 and CD146. The response of the label-retaining cells to the injury was associated with early activation of Notch signalling (4 dpi), followed by BMP signalling at 8 dpi and TGF-β at 12 dpi. Conversely, canonical Wnt signalling, which was active in uninjured knee joints and in injured knee joints up to 8 dpi, was attenuated at 12 dpi. The contribution of nerve growth factor (NGF), known as a pain mediator in OA, to the repair process was then investigated in vitro. NGF was released by both cartilage explants and femoral head cultures following injury. Using a Transwell-based cell migration assay, NGF was revealed to have a chemotactic effect on human bone marrow derived MSCs, but not synovial membrane derived MSCs. High-density micromass cultures also revealed NGF had a potent stimulatory effect on the chondrogenic differentiation of mesenchymal cells. The data presented here demonstrate a contribution of endogenous MSCs to the repair of articular cartilage in vivo and suggest a possible new therapeutic strategy: stimulation of in vivo recruitment of MSCs by modulating signalling pathways activated during the healing process. Furthermore, a novel role for NGF as a factor involved in migration and the chondrogenic differentiation of MSCs is suggested.

Nerve autografts are widely used clinically to repair nerve grafts. However, nerve grafts have many limitations, such as, availability of donor nerve grafts, and loss of function at donor site. To overcome these problems, we have used a tissue engineering approach to design three-dimensional (3D) agarose scaffolds containing gradients of laminin-1 (LN-1) and nerve growth factor (NGF) to mimic in vivo conditions to promote nerve regeneration in rats. To determine the effect of LN-1 gradients on neurite extension in vitro, dorsal root ganglia (DRG) from chick embryos were cultured in 3D hydrogels. A gradient of LN-1 molecules in agarose gels was made by diffusion technique. LN-1 was then immobilized to the agarose hydrogels using a photo-crosslinker, Sulfo-SANPAH (Sulfosuccinimidyl-6-[4-azido-2-nitrophenylamino] hexanoate). Anisotropic scaffolds with three different slopes of LN-1 gradients were used. Isotropic scaffolds with uniform concentrations of LN-1, at various levels, were used as a positive control. DRG cultured in anisotropic scaffolds with optimal slope of LN-1 gradient extended neurites twice as fast as DRG in optimal concentration in isotropic scaffolds. Also, in the anisotropic scaffolds the faster growing neurites were aligned along the direction of LN-1 gradient. To promote nerve regeneration in vivo, tubular polysulfone guidance channels containing agarose hydrogels with gradients of LN-1 and NGF (anisotropic scaffolds) were used to bridge 20-mm nerve gaps in rats. Nerve autografts were used as positive controls and isotropic scaffolds, with uniform concentration of LN-1 and NGF, were used as negative controls. After 4-months, the rats were sacrificed and nerve histology was done to test for nerve regeneration. Only anisotropic scaffolds and nerve autografts contained evidence of axonal regeneration. Both groups had similar numbers of myelinated axons and similar axonal-diameter distribution. However, nerve graft group performed better in functional outcome as measured by relative gastrocnemius muscle weight (RGMW) and electrophysiology. Optimization of performance of anisotropic scaffolds by varying the LN-1 and NGF concentration gradients might lead to development of scaffolds that can perform as well as nerve auotgrafts for nerve regeneration over long nerve gaps.

No description available.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 134-172). Also available in electronic version. Access restricted to campus users.

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Paediatrics / Master / Master of Philosophy

Η περιφερική αρτηριοπάθεια αποτελεί μία νόσο με αυξημένη επίπτωση στις σύγχρονες χώρες. Οι τρόποι αντιμετώπισής της ποικίλουν, ωστόσο, ένα μεγάλο ποσοστό ασθενών δεν μπορεί να αντιμετωπιστεί με τις υπάρχουσες συμβατικές θεραπείες, είτε χειρουργικές, είτε συντηρητικές. Η αγγειογένεση αποτελεί έναν πολλά υποσχόμενο τρόπο αντιμετώπισης. Επιτελείται ευρεία έρευνα με χρησιμοποίηση μιας μεγάλης ποικιλίας ουσιών και κυττάρων με στόχο την επίτευξη θεραπευτικής αγγειογένεσης που θα βελτιώσει την κλινική εικόνα των ασθενών με περιφερική αρτηριοπάθεια. Ο νευρικός αυξητικός παράγοντας (NGF) υπάρχουν αναφορές ότι έχει σημαντικό ρόλο στη φυσιολογική και παθολογική αγγειογένεση. Βασισμένοι σε αυτές τις παρατηρήσεις, υποθέσαμε ότι ο NGF μπορεί να επάγει το σχηματισμό λειτουργικών αιμοφόρων αγγείων σε μοντέλο ισχαιμίας οπισθίων άκρων κονίκλου. Η ισχαιμία στα οπίσθια άκρα προκλήθηκε σε 34 κονίκλους με αμφοτερόπλευρο εμβολισμό της μηριαίας αρτηρίας. Την 7η, 14η και 20η ημέρα μετά τον εμβολισμό χορηγήθηκε NGF ενδομυϊκά σε ένα από τα δύο ισχαιμικά άκρα και εγχύθηκε μάρτυρας στο άλλο άκρο. Την 40η ημέρα, τα νεοσχηματισμένα παράπλευρα αγγεία διαμέτρου μεγαλύτερης των 500μm ποσοτικοποιήθηκαν με διαωτιαία ενδοαρτηριακή αφαιρετική αγγειογραφία. Πραγματοποιήθηκε, επίσης, in vivo δυναμική αξονική τομογραφία αιμάτωσης σε αμφότερα τα άκρα ώστε να διερευνηθεί η αιμοδυναμική ανάρρωση των ισχαιμικών ιστών. Η λειτουργική εκτίμηση της αιμάτωσης των άκρων έδειξε στατιστικά σημαντική αύξηση της αιματικής ροής και του όγκου αίματος στα άκρα που χορηγήθηκε NGF. Ωστόσο, η αύξηση των παράπλευρων αγγείων δεν ήταν ανιχνεύσιμη αγγειογραφικά, κάτι που υποδηλώνει ότι ο NGF ενίσχυσε τη δημιουργία τριχοειδικού δικτύου αλλά όχι την αρτηριογένεση. Ο συνδυασμός του NGF είτε με αναστολέα του TrkA είτε με αναστολέα του VEGFR-2, κατήργησε την αιμοδυναμική ανάρρωση που προκάλεσε ο NGF. Αυτό δείχνει εξάρτηση της αγγειογενετικής δράσης του NGF τόσο από το δικό του υποδοχέα άμεσα, όσο και από τον υποδοχέα του VEGF έμμεσα. Τα ανωτέρω ευρήματα προσφέρουν νέους ορίζοντες στην κατανόηση της δράσης του NGF στο σχηματισμό νέων αγγείων και στις πιθανές εφαρμογές του στη θεραπευτική αγγειογένεση. / Nerve growth factor (NGF) has been reported to play an important role in physiological and pathological angiogenesis. Based on these observations, we hypothesized that NGF may induce the formation of functional blood vessels in a hindlimb ischemic rabbit model. Hindlimb ischemia was induced in 34 rabbits bilaterally by endovascular embolization of femoral arteries. On the 7th, 14th, and 20th postembolization days, NGF was injected intramuscularly, in 1 ischemic limb, and vehicle was injected in the contralateral control limb. On the 40th day, newly developed collateral vessels (diameter .500 mm) were quantified by transauricular intraarterial subtraction angiography. Perfusion analysis of an in vivo dynamic computed tomography study was performed to the limbs to investigate the hemodynamic recovery of the distal ischemic tissues. Functional estimation of limb perfusion showed a statistically significant increase of blood flow and blood volume for NGF. However, the increase of the collateral vessels was not detectable angiographically, providing evidence for the existence of a NGF-stimulated capillary angiogenic network but not increase of arteriogenesis. The combination of NGF with either tropomyosin-related kinase type A or vascular endothelial growth factor receptor 2 antagonists abolished the NGF-induced hemodynamic recovery. These findings provide new insights into understanding the involvement of NGF in vascular formation and its applications in therapeutic angiogenesis.

Bibliography : leaves 141-165. / xiv, 174, [8] leaves, [8] leves of plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Aims to determine if the gene expression of NGF (NGFmRNA) is enhanced in blood vessels that display hypernoradrenergic innervation in the SHR. / Thesis (Ph.D.)--University of Adelaide, Dept. of Clinical and Experimental Pharmacology, 1992