Thesis (M.S.) --University of Texas Graduate School of Biomedical Sciences at San Antonio, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [118]-127).

Ulm, Univ., Diss., 2001.

Abstract Angiogenesis is essential for the replacement of cartilage by bone during skeletal growth and regeneration. Vascular endothelial growth factor-A (VEGF-A) is a key regulator of angiogenesis whereas endostatin, a potent inhibitor of endothelial cell proliferation and migration, is a natural antagonist of VEGF-A. The regulatory roles of these peptides in angiogenesis, bone formation and bone cells were investigated in this study. In the present work we studied the effects of VEGF-A, delivered with an adenoviral vector, on the recovery of bone drilling defects in rat femur. Our data confirm the important role of VEGF in bone healing and that adenoviral VEGF gene transfer may modify bone defect healing in a rodent model. We studied the effects of VEGF-A and endostatin on bone resorption activity. It was found that VEGF-A is a potent stimulator of bone resorption and osteoclast differentiation in vitro and endostatin can antagonize this stimulatory effect when acting directly on bone cells. This suggests that endostatin is indeed a regulator of bone resorption, but not a critical one. In the present study we induced ectopic bone formation in the hamstring muscles of adult mice. The effects of VEGF-A and endostatin in the ectopic bone formation assay were evaluated by the simultaneous delivery of both peptides with recombinant adenoviral vectors. It was found that endostatin retards the cartilage phase in endochondral ossification that subsequently reduces bone formation. We conclude that bone growth and healing, which share features with ectopic bone formation, may be regulated by endostatin. To confirm in vivo effects on bone formation we further investigated the effects of endostatin and VEGF-A on mouse pre-osteoblastic cells in vitro. Finally the effects of endostatin on bone were studied in transgenic mouse lines overexpressing endostatin, and mice lacking collagen XVIII.

Thesis (M.Ed.)--University of Waikato, 2007. / Title from PDF cover (viewed May 1, 2008) Includes bibliographical references (p. 124-133)

Kollagen Typ I, als wesentlicher Bestandteil der ECM, spielt eine entscheidende Rolle in der Wundheilung nach Myokardinfarkt. Zum einen ist eine ausreichende Narbenbildung zur Gewährleistung der Ventrikelstabilität notwendig, zum anderen führt eine überschießende Kollagensynthese mit interstitieller Fibrose des Myokards zu einer kontraktilen Dysfunktion des Ventrikels. Inwiefern sich eine Verminderung oder das Fehlen an Kollagen Typ I auf die Wundheilung und das Remodeling auswirkt, untersuchten wir am Modell der Osteogenesis Imperfecta Maus (OIM). 12-16 Wochen alte homozygote OIM Tiere, sowie heterozygote und homozygote Kontrollen, wurden einer Unterbindung der linken Koronararterie mit konsekutiven Myokardinfarkt (AMI) oder einer „Schein“- Infarzierung unterzogen. Echokardiographische Kontrollen der Ventrikelfunktion erfolgten am Tag vor, am Tag 1, Tag 8 und 8 Wochen nach AMI und „Schein“- Infarzierung, bevor wir die Tiere opferten. Das experimentelle Protokoll ex vivo zur Analyse der mechanischen Eigenschaften des Gewebes und des Kontraktionsverhaltens umfasste die Bestimmung der isometrischen Kraft und der Kraft- Frequenz- Beziehung. Außerdem wurden alle Herzen unabhängig vom Zeitpunkt des Todes histologisch aufgearbeitet 1. zur Infarktgrößenbestimmung, 2. zur immunhistologischen Bestimmung des Kollagengehalts und 3. zur Untersuchung der Todesursache bei vorzeitigem Tod. Vor Beginn der Studie fanden wir keine Unterschiede zwischen den OIM-/- und den Kontrollgruppen in ihrer Ventrikelfunktion. In der frühen Phase (Tag 3 bis 7) nach AMI war die Sterblichkeitsrate der OIM-/- aufgrund von Ventrikelrupturen signifikant erhöht verglichen mit den Kontrollen (54% OIM-/- vs. 13% WT). Wir konnten keine Abhängigkeit von der Infarktgrösse als ursächlichen Faktor auf das Entstehen einer Ruptur beobachten, da auch Tiere ohne makro- und mikroskopischen Nachweis eines Infarktes aus diesem Grund verstarben. Nach 8 Wochen präsentierten die OIM-/- eine signifikant niedrigere Dilatation des linken Ventrikels, sowie einen geringeren linksventrikulären Durchmesser verglichen mit den Kontrollgruppen. In den muskelphysiologischen Versuchen der isometrischen Kraftentwicklung konnte sowohl in der Infarkt- als auch in der Sham- Gruppe eine höhere maximale Kraft der OIM-/- verglichen mit den heterozygoten und homozygoten Kontrollen beobachtet werden. Zum Erreichen vergleichbarer Kraftniveaus war bei den homozygoten OIM eine signifikant grössere Vordehnung notwendig, was indirekt für eine höhere Gewebecompliance spricht. Der Kollagengehalt in der Infarktnarbe der OIM-/- war gegenüber den OIM+/- und WT Tieren signifkant erniedrigt. Keine Unterschiede in den drei Gruppen fanden sich in der Infarktgrössenentwicklung nach AMI. / Background: Collagen synthesis is an important process in early wound healing after myocardial infarction (MI). Interstitial fibrosis during chronic post infarction remodelling however is associated with impaired ventricular function. To assess the role of collagen I after MI we studied a mouse model of osteogenesis imperfecta (OI). Homozygous OI mice (OIM) lack pro-alpha 2 -(I) collagen, a defect that was previously shown to be associated with decreased chamber stiffness but normal left ventricular dimensions and systolic function. Methods: 12-16 weeks old homozygous, heterozygous OIM mice and wild type mice were subjected to a chronic myocardial infarction protocol or sham operation. Echocardiographic studies were performed before operation, on day 1, 8 and before sacrifice after 8 weeks. In a second group all animals were sacrificed on day 2. Collagen was quantified histologicaly and by real-time PCR. Matrixmetalloproteinase-9 (MMP-9) expression in infarct border zone 2 days after MI was assessed by ELISA. Results: As determined by echocardiography baseline functional and geometrical parameters were not different between genotypes. After MI but not after sham operation homozygous OIM mice showed a significantly increased mortality due to early ventricular rupture (54% oim/oim vs 13% wt/wt) between day 3 and 7. Occurrence of fatal rupture was independent of infarct size. Surviving OIM mice revealed significantly less ventricular dilation when compared with heterozygous after completing the 8 weeks period. Infarct size was not different between genotypes after 2 days or 8 weeks. OIM mice revealed increased ventricular diameter as determined by echocardiography on day 1. Homozygous OIM showed significantly less collagen I mRNA within the infarct area. MMP-9 expression in the infarct border zone was significantly higher in OIM animals 2 days after MI. Conclusion: In the present model of OI we observed a high mortality due to ventricular rupture after MI. Early ventricular dilation, less collagen I expression and increased MMP-9 activity within infarct area account for this fatal outcome after acute MI. The OIM mouse model demonstrates the importance collagen I for early myocardial wound healing as well as remodelling.

A instalação de implantes odontológicos requer a presença de substrato ósseo adequado para garantir estabilidade e equilíbrio biomecânico. A deficiência óssea requer procedimentos de enxertia para adequar o volume para a instalação de implantes, porém a utilização de enxertos autógenos causa aumento de morbidade ao paciente e o uso de material homógeno e xenógeno apresenta dúvidas quanto à reação autoimune, transmissão de doenças e ao grau de reabsorção do enxerto. Com o grande desenvolvimento científico e tecnológico dos biomateriais, os materiais cerâmicos, tornaram-se alternativas promissoras para a recomposição da estrutura óssea perdida. As cerâmicas à base de fosfato de cálcio como a hidroxiapatita (HA) e o beta- fosfato tricálcido (beta-TCP), são materiais que apresentam qualidades desejáveis no processo de neoformação óssea como, por exemplo, a biocompatibilidade, bioatividade e osteocondutividade. A proposta deste trabalho é desenvolver e estudar corpos de prova na forma de cúpula oca de hidroxiapatita preenchidos por coágulo, beta- TCP e composto vitamínico, para estudar a osteogênese supracortical, a partir do potencial osteocondutor da cúpula de HA. As cúpulas foram obtidas por prensagem isostática a 200 MPa e sinterização ao ar a 1100°C por 60 minutos. As caracterizações físico-químicas das matérias-primas e da cúpula de HA foram realizadas por difração de raios X, microscopia eletrônica de varredura e determinação da densidade. Na caracterização biológica, foram realizados o teste de citotoxicidade in vitro e ensaio in vivo. Foram designados 9 coelhos (raça Nova Zelândia), sendo instaladas 18 cúpulas, divididas em três grupos, de acordo com o preenchimento: controle, composto vitamínico e β-TCP em forma de pó. O período de reparação tecidual foi de 8 semanas, no qual foram aplicados marcadores de fluorescência. Após o período de cicatrização e eutanásia, as amostras foram incluídas em resina para a obtenção das lâminas e observadas em microscópio de fluorescência, para avaliar a quantidade de tecido ósseo neoformado, em microscópio de campo claro, para verificar as células presentes no tecido formado e por Espectroscopia de Energia Dispersiva, para análise química, da formação no interior das cúpulas. Como resultados, a cúpula de hidroxiapatita apresenta bom desempenho como arcabouço para neoformação óssea acima da cortical da tíbia de coelhos, pois manteve-se íntegra, com boa estabilidade e boa integração ao tecido ósseo, e principalmente pela neoformação óssea, demonstrando seu potencial osteocondutor. Em relação aos materiais de preenchimento, o beta-TCP apresenta maior valor de área de osso neoformado, em comparação com o coágulo. Nas cúpulas com preenchimento de composto vitamínico, não há formação de tecido ósseo pela não reabsorção do material. / The installation of dental implants requires the presence of adequate bone substrate to ensure stability and biomechanical balance. Deficiency requires bone grafting procedures to adjust the volume for implant placement, but the use of autogenous grafts cause increased morbidity to the patient and the use of homogenous and xenogenous materials has doubts about the autoimmune reaction, transmission of disease and the degree of resorption of the graft. With the great scientific and technological development of biomaterials, ceramic materials, have become promising alternatives for restoration of lost bone structure. The ceramics based on calcium phosphate such as hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP) are materials having desirable qualities in the process of bone formation, for example, biocompatibility, bioactivity and osteoconductivity. The purpose of this work is to develop and study the dome-shaped hydroxyapatite filled with blood clot, beta-TCP and vitamin compound, to study osteogenesis supracortical from the osteoconductive potential of the dome of HA. The domes were obtained by isostatic pressing at 200 MPa and sintered in air at 1100 ° C for 60 minutes. The physico-chemical characterization of raw materials and the dome of HA were performed by X-ray diffraction, scanning electron microscopy and density determination. In biological characterization were performed tests for in vitro cytotoxicity and tests in vivo. Were designated 9 rabbits (New Zeland), and installed 18 domes, divided into three groups, according to the filling: control, vitamin compound and β-TCP in powder form. The period of wound healing was 8 weeks, when a fluorescence marker was applied. After the healing period and euthanasia, the samples were embedded in resin to obtain the slides and observed under fluorescence microscope to evaluate the amount of newly formed bone tissue in bright field microscope to check the cells present in the tissue and by Energy Dispersive Spectroscopy for chemical analysis, inside the domes. As a result, the hydroxyapatite dome has good performance as scaffold for bone formation above the cortical tibia of rabbits, it remained intact, with good stability and good integration with bone tissue, especially bone formation, demonstrating osteoconductive potential. Regarding the filling materials, beta-TCP has a higher value of area of new bone formation compared to the clot. In the domes-filled vitamin compound, there is no formation of bone resorption by not material.

Orientador: Luana Marotta Reis de Vasconcellos / Coorientador: Adriano Gonçalves dos Reis / Banca: Marianne Spalding / Banca: Newton Soares da Silva / Banca: Alexandre Luiz Souto Borges / Banca: Jonatas Rafael de Oliveira / Resumo: Neste estudo foram caracterizadas superfícies de titânio (Ti) obtidas após utilização de diferentes temperaturas pela técnica de implantação iônica por imersão em plasma de oxigênio (O-IIIP), bem como correlacionado o efeito deste tratamento com a osteogênese e formação de biofilmes microbianos monotípicos. As amostras foram caracterizadas por meio de análises de química de superfície, rugosidade e textura da superfície, molhabilidade e resistência à corrosão. Além disso, análises de biocompatibilidade por meio de interação e viabilidade celular, conteúdo de proteína total, atividade de fosfatase alcalina e quantificação de nódulos de mineralização foram realizadas sobre a linhagem celular MG-63 (osteoblato humano). Análise de formação de biofilmes de Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus mutans e Candida albicans sobre as superfícies também foi realizada. Os dados foram estatisticamente analisados por teste ANOVA e Tukey (p<0,05, p<0,001 e p<0,0001). Os resultados das análises de química de superfície demonstraram um aumento proporcional da quantidade de O conforme aumento da temperatura utilizada na técnica de O-IIIP, verificando ainda a presença de TiO2 nos grupos tratados a 500ºC e 600ºC. Foi observado que, em escala nanométrica, houve um aumento significativo da rugosidade e da área superficial nas amostras tratadas com O-IIIP conforme aumento da temperatura utilizada, apresentando ainda, um aumento significativo da hidrofobicidade e resistência à ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this study, titanium surfaces were produced by the ion implantation technique, immersing samples in oxygen plasma (O-IIIP), at different temperatures. Therapeutic effects of the surface modification were evaluated for osteogenesis and formation of monotypic microbial biofilms. Roughness, texture, wettability, corrosion resistance and chemical composition of the samples were characterized. Moreover, biocompatibility of the produced materials was verified by cell interaction and viability, total protein content, alkaline phosphatase activity, and quantification of mineralization nodules assays were performed on MG-63 (human osteoblate) cells. Biofilm formation of Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus mutans and Candida albicans on surfaces was also evaluated. Data were statistically analyzed by ANOVA and Tukey test. A proportional intensification in the amount of oxygen was observed as the temperature used in the O-IIIP technique raised, also, TiO2 was observed in the groups treated at 500 ºC and 600 ºC. At nanoscale, there was a statistic increase in both roughness and surface area in samples treated with O-IIIP as a result of the increase of the temperature used. Hydrophobicity and corrosion resistance were also higher in samples treated with OIIIP. According to the performed biocompatibility analyzes, cell viability, total protein production, alkaline phosphatase activity and the formation of mineralized nodules were stimulated and increased in the group treated with O-IIIP at 600 ºC, compared to the other groups. In the assays performed with monotypic microbial biofilms, a statistic reduction of microorganisms was observed especially in the groups submitted to O-IIIP treatment at 500 ºC and 600 ºC. Therefore, we demonstrated here that O-IIIP technique was able to chemically and physically modify surfaces,... (Complete abstract click electronic access below) / Doutor

The goal of this study is to assess the osteogenic potential of two types of dental stem cell lines within a tissue engineering application. More specifically, the goal of this study is to find a readily abundant cell source with capacity to express an osteogenic phenotype. There are two parameters utilized to evaluate tissue engineering potential of cells: proliferation rate and differentiation potential. Briefly, proliferation rate is the speed at which cells divide and differentiation potential determines if cells are capable of committing towards specific lineages (e.g. osteogenic). These components are important, because if cells are not expanding at a specific rate and are not differentiating towards the lineage desired, the tissue engineered will not mirror the characteristics of native tissue. Therefore, both components are necessary for osteogenic tissue engineering applications. Several stem cell lines have been isolated from different sources (e.g. umbilical, bone marrow) and characterized for their proliferative capacity and their potency. Among these progenitor or stem cell lines, are those isolated from human dental tissue. Due to the similarities between teeth and bone, this specific cell line may be useful in osteogenic tissue engineering applications. In this study, stem cells extracted from human exfoliated deciduous teeth (SHEDs) and periodontal ligament stem cells (PERIOs), were evaluated and compared. Briefly, to evaluate the proliferation rate an ex-vivo expansion study was conducted. This experiment found that both SHEDs and PERIOs were proliferative lines with doubling times of 23 hours and 19 hours respectively. Subsequently, osteogenic differentiation of SHEDs and PERIOs was assessed utilizing a 3-D fibrin gel suspension treated with osteogenic media containing either dexamethasone (DEX) or Retinoic Acid (RA) for 28 days. At day 28, osteogenic markers for collagen 1 (Col1), osteocalcin (OCN), and alkaline phosphatase (ALP) were evaluated using qPCR. Results demonstrated both SHEDs and PERIOs exhibited significant (p<0.05) increases in osteogenic gene expression under the influences of DEX and RA. However the most significant increases were expressed by the SHEDs that received the DEX treatment. Additionally, the synergistic ability of TGF-beta 3 on the osteogenic differentiation of the stem cells was evaluated. Cells were cultured in a 3-D fibrin gel suspension and allowed to differentiate in DEX osteogenic media with and without the supplementation of TGF-beta 3 for 21 days. Using qPCR the cells were evaluated for expression of Col1, OCN, and ALP. In both the SHEDs and PERIOs, the samples treated with TGF-beta 3 the osteogenic gene expression increased in reference to the control, but had a hindering effect compared to cells treated in DEX without the TGF-beta 3. These results from this study suggested, SHED cells grown in 3-D fibrin gel suspension, may be better than PERIO cells for osteogenic tissue engineering applications when treated with DEX media without the supplementation of TGF-beta 3.

Η διπλωματική αυτή εργασία πραγματεύεται την προσομοίωση μιας ορθοπεδικής διάταξης οστεογένεσης, την τρισδιάστατη απεικόνιση αυτής από κατασκευαστικής άποψης καθώς και την πλήρη μελέτη της κίνησης αυτής με τον προγραμματισμό της ορθής και αντίστροφης κινηματικής. Πιο συγκεκριμένα η μελέτη που γίνεται αφορά το είδος πλατφόρμας Stewart και χρήση αυτής ως εξωτερικής συσκευής οστεογένεσης. Πρωτεύον μέλημά μας αποτελεί η περιγραφή του φαινομένου της οστεογένεσης και η κατανόηση της λειτουργίας και ανάπτυξης των οστών (Κεφάλαιο 2). Στη συνέχεια προβαίνουμε σε μια αναλυτική παρουσίαση των συσκευών οστεογένεσης που υπάρχουν στον χώρο με επιμέρους ανάλυση της λειτουργίας της κάθε μιας καταλήγοντας στην πλατφόρμα που θα μελετήσουμε (Κεφάλαιο 3). Ακολούθως, παρουσιάζουμε την κινηματική ανάλυση της πλατφόρμας Stewart τόσο την ορθή όσο και την ανάστροφη και επίσης γίνεται και μελέτη της δυναμικής ανάλυσης της διάταξης αυτής (Κεφάλαιο 4). Λαμβάνοντας υπόψη όλα τα προηγούμενα, είμαστε σε θέση να προχωρήσουμε στην προσομοίωση της πλατφόρμας Stewart , αρχίζοντας με τον προγραμματισμό των κινηματικών εξισώσεων, συνεχίζοντας με την προσομοίωση στο Simmechanics και τέλος δημιουργώντας την τρισδιάστατη απεικόνιση της διάταξης στο VRML toolbox του Matlab όπου φαίνεται η κίνηση της πλατφόρμας στον τρισδιάστατο χώρο (Κεφάλαιο 5). Τέλος, παρουσιάζονται τα συμπεράσματα και οι προοπτικές της εν λόγω εργασίας (Κεφάλαιο 6). / This thesis deals with the simulation of an orthopaedic device of osteogenesis, the 3d depiction concerning the constructional aspect as well as with the complete study of the movement with the planning of kinematics and inverse kinematics. More concretely the study concerns the category of a Stewart platform and the use of this platform as an exterior appliance for osteogenesis. Our first concern is the description of the phenomenon of osteogenesis and the comprehension of the operation and growth of bones (Chapter 2). Then we proceed in an analytic presentation of devices of osteogenesis that exist, with specific analysis of the operation of any kind that exists in the industrial field leading to the platform that we will study (Chapter 3). Following, we present the kinematical analysis of the Stewart platform as well as the study of the dynamic analysis of this fixator (Chapter 4). Taking into consideration all the above, we advance in the simulation of the Stewart platform, beginning with the planning of kinematical equations, continuing with the simulation in the Simmechanics and finally creating a 3d depiction of the device in the VRML toolbox of Matlab where we can watch the movement of the platform in the xyz space (Chapter 5). Finally, the conclusions and the prospects of this work are represented (Chapter 6).