The hematopoietic system supplies short-lived functional end cells of multiple lineages from a common pool of pluripotent stem cells throughout life. In man neoplastic transformation of these stem cells results in the development of the acute and chronic myeloid leukemias. An in vitro system where functional murine stem cells can be maintained for several months has recently become available. This system has been a powerful tool to analyze mechanisms regulating normal hematopoiesis and leukemogenesis in mice. The purpose of this work was to develop an analogous culture system applicable to human marrow and to evaluate its ability to support leukemic hematopoiesis. Long-term cultures were established with normal human marrow cells. In these, the more primitive progenitors were found to be almost exclusively located in the adherent layer for the duration of the culture (i.e., at least 2 months). A prerequisite for these studies was the development of a procedure for detaching adherent cells so that various colony-forming progenitors could be assayed in semi-solid media. The consistent finding of adherent layer-associated hematopoiesis suggests that cell-cell interactions between primitive hematopoietic cells and adherent layer elements may be essential for the maintenance of the former. Long-term cultures were also initiated with marrow from 11 CML patients and 13 AML patients (all untreated) and maintenance of normal and neoplastic progenitor cell populations assessed. A common finding was the rapid disappearance of neoplastic progenitor cells (recognized either by the presence of chromosomal abnormalities or by their abnormal differentiation capacity) in most cultures, even though cytogenetically normal precursors were often maintained. These differences between the behaviour of normal and neoplastic cells in long-term cultures may reflect changes at the stem cell level that are related to the acquisition of abnormal growth properties. In a minority of patients a different result was obtained. Clonal dominance persisted in vitro and normal hematopoiesis was not detected. Thus long-term cultures have also allowed differences in the behaviour of primitive neoplastic cells from different patients to be revealed. Future investigation of the basis for these differences may provide new insights into the biological heterogeneity that characterizes these disorders / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate

Orientador: Frederico Andrade e Silva / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-22T06:55:09Z (GMT). No. of bitstreams: 1 Cvijic_Gojko_D.pdf: 2099298 bytes, checksum: abafee052c159ac120d8c1fc520d05e2 (MD5) Previous issue date: 2013 / Resumo: O objetivo deste estudo foi comparar o nível de reabsorção óssea em implantes com superfícies física e quimicamente tratadas, carregados com coroas unitárias, inseridos em osso previamente enxertado. Foram avaliadas as imagens digitalizadas das radiografias periapicais de 20 implantes, sendo 10 com superfícies SLA® e 10 com superfícies SLActive® (Instituto Straumann®, Basel, Suíça). Coroas metalocerâmicas foram instaladas doze semanas após a colocação dos implantes no primeiro grupo (SLA) e seis semanas no segundo (SLActive). Radiografias periapicais foram realizadas imediatamente após a colocação das coroas (T0), e aos 3 (T1), 6 (T2) e 12 (T3) meses. Após a digitalização das radiografias, foi medido o Nível Médio de Reabsorção Óssea (NMRO) nos quatro períodos experimentais. Os resultados foram submetidos ao teste ANOVA e Dunnett revelando que o NMRO no grupo SLA variou entre 0,08mm±0,64 (T0) a 0,44mm±0,66 (T3). No grupo SLActive foi de -0,05mm±0,60 (T0) a -0,05mm± 0,41 (T3). A alteração do NMRO não teve valor significativo dentro de cada grupo, porém quando os resultados entre os grupos foram comparados, houve diferença estatística: 0,20mm±0,70 (SLA) e -0,04mm±0,44 (SLActive), (p<0,05). De acordo com metodologia empregada, NMRO no grupo SLActive não reduziu em função da carga mastigatória durante doze meses de avaliação / Abstract: The aim of this study was to compare the level of bone resorption on implants with physically and chemically treated surfaces, placed in grafted maxillae, and loaded with single crowns. The periapical radiographs of twenty implants, 10 with SLA® and 10 with SLActive® surface (Institut Straumann®, Basel, Switzerland), were digitalized and analyzed. The metaloceramic crowns were installed twelve weeks after placing the SLA implants and 6 weeks after SLActive implants. The periapical radiographs were done immediately after crown installing (T0), 3 (T1), 6 (T2) and 12 (T3) months, afterward. The digitalized images were used to analyze the Medium Level of Bone Resorption (MLBR) in four experimental periods (T0, T1, T2, T3). Using ANOVA and Dunnett tests, the results showed that MLBR varied between 0,08 mm ± 0,64 (T0) to 0,44 mm ± 0,66 (T3) in SLA group. Nevertheless, in SLActive group MLBR measured -0,05 mm ± 0,60 (T0) to -0,05 mm ± 0,41 (T3). The MLBR wasn't significant, however, comparing two groups the difference was significant: 0,20 mm ± 0,70 (SLA) and -0,04 mm ± 0,44 (SLActive) (p<0,05). According to used methodology, MLBR around SLActive implants did not reduce after loading, during the twelve months of evaluation / Doutorado / Protese Dental / Doutor em Clínica Odontológica

OBJECTIVES: This study aims to fabricate graded composite structures with different ceramic materials and explore the effect of the various ceramic materials on the microstructure, surface topography, crystal characterization, bioactivity, and mechanical properties of the ceramic scaffold. MATERIALS AND METHODS: Ceramic matrix specimens were prepared with a slip casting technique. After sintering, specimens were examined for their physical, chemical, and mechanical properties including microstructure, surface roughness, elemental composition, crystal characterization and biaxial flexural strength. Specimens from each group were immersed in a calcification solution and were evaluated for the deposition of calcium phosphate through microscopy, elemental analysis, and crystal characterization. RESULTS: Graded ceramic matrix materials were successfully fabricated using a slip-casting technique. Scanning electron microscopy revealed different surface topography as well as the deposition of calcium phosphate crystals on the specimen surface after immersion in calcification solution. Elemental composition and X-Ray Diffraction (XRD) spectra confirmed phase transformation in the composite specimen after sintering. Particle grain size significantly affected surface topography in terms of surface area roughness and topographical patterns. Moreover, the combination of alumina and bioactive glass improved mechanical properties compared to bioactive glass alone. CONCLUSIONS: 1. The ceramic matrix containing bioactive glass presented greater surface roughness compared to other ceramic matrix without bioactive glass. 2. Two crystal phases: tricalcium silicate (Ca3Si3O9) and calcium metasilicate (CaSiO3) were found in high temperature sintered bioactive glass. The combination of bioactive glass with alumina or hydroxyapatite presented another tricalcium silicate phase such as Ca3(SiO4)O. 3. The XRD analysis of the combination of alumina and hydroxyapatite detected two new phases including grossite (CaAl4O7) and calcium aluminophosphate (Ca9Al(PO4)7). 4. Ceramic matrix containing bioactive glass or hydroxyapatite presented greater deposition of calcium phosphate crystals while the combination of bioactive glass and hydroxyapatite showed the greatest amount of the precipitated crystals. 5. Alumina ceramic matrix showed the highest biaxial flexural strength while hydroxyapatite and bioactive glass presented low biaxial flexural strength. 6. The combination of alumina with hydroxyapatite or bioactive glass improved biaxial flexural strength. 7. The combination of hydroxyapatite with bioactive glass had lower biaxial flexural strength compared to a single-phase ceramic matrix.

archives@tulane.edu / Prostheses have enabled many people with bone injuries to achieve a quality of life that would be difficult without the advances in biomedical engineering and materials sciences. Exploration of alternatives to current methods of prosthetic bone development will result in more options from both the physician and patient perspective for the replacement of bone and the use of bone substitutes. Thus, new bone prostheses can be customized to a patient’s needs. To address rising healthcare costs, 3D printed bone substitutes are enabling affordable and customizable bone replacements. In this study, we designed a strong yet lightweight structural matrix to substitute bone grafts in cases of comminuted fracture of tibial bone. The artificial matrix is inspired by structural components called voxels that have been demonstrated to be feasible in the areas of aerospace for fixed and morphing wing flight. The basis of this voxel matrix is derived from units of hollow eight-sided faces formed from 12 connected struts. In this study, we have produced and simulated a lattice that can resemble natural bone performance. This bone facsimile has been evaluated using finite element analysis to suggest an optimal voxel density and beam width at which the internal structure has a high elastic modulus to relative density ratio for use as a scaffold during bone reconstruction. A lattice-based implant was designed and evaluated using finite-element analysis for osteosarcoma-afflicted long bones such as the tibia. This study should pave the way for bone implants made of strong but lightweight structures can help patients regain the faculties of natural bone. Ultimately, this structure would be constructed from biocompatible materials that provide nutrients for natural bone regeneration processes. With this, the structure would reabsorb completely into the healing bone, after providing a matrix upon which osteoblasts can form new bone. / 1 / Afsheen Sajjadi

Charles University, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical Technology Author: Jiří Doubek Supervisor: Dr. Georgios Paraskevopoulos, Ph.D. Title of Thesis: Calcium phosphate bone cements: Synthesis, characterization and drug release properties Non-healing bone traumas are currently a complication, which may disable a patient from active life for a long period. Due to the fact that bone mass consists mostly of hydroxyapatite, a derivative of calcium phosphate - calcium phosphate cement (CPC) - is studied as an injectable bone substitute. The cement's characteristics (low setting temperature, injectability, bioactivity, and resorbability) are very promising. Furthermore, the possibility to incorporate a drug in the formulation that would support the healing process opens a way for new therapeutic options. Firstly, the aim of this research was to synthesize a high-quality α-tricalcium phosphate (α-TCP) and characterize its properties. Subsequently, the prepared α-TCP was used for the preparation of an injectable and washout resistant cement paste. Finally, the properties of developed pure or ibuprofen-loaded cement were examined by X-ray diffraction, Raman spectra, compressive strength, scanning electron microscopy, and dissolution studies. The obtained data revealed that...

Thesis (M.Sc.D.)--Boston University School of Graduate Dentistry, 1972 (Orthodontics) / Bibliography included.

BACKGROUND: Alveolar bone resorption is more severe in type 2 diabetes-potentiated periodontitis. The key cells responsible for bone resorption are the osteoclast and their quantity and activity are regulated by the RANK/RANKL/OPG system. One of the major RANKL-expressing sources in diseased periodontal tissue are activated B and T lymphocytes, therefore it was hypothesized that type 2 diabetes up-regulates B cell RANKL function. OBJECTIVE: The aim of this study was to compare the effect of diabetes on the ability of B and T lymphocytes to stimulate osteoclast activity. MATERIALS AND METHODS: Metabolic status (diabetic vs normal) of mice were established using either a low-fat diet (LFD) or high-fat diet (HFD). Spleen lymphocytes were harvested and purified, then cultured in different combinations with adherent mouse leukemic monocyte/macrophage cell line cells over dentin-coated wells and observed for osteoclastic activity that breaks down the dentin-coating. The area of clearance was used to represent the level of activity. RESULTS: No difference in osteoclastic activity were noted between the two metabolic statuses, between B or T cells, between lymphocyte stimulated or not. CONCLUSION: The findings counters our hypothesis, and are inconsistent with the currently available evidence. Repeat of the experiment is warranted before valid conclusion can be drawn from the data.

Indiana University-Purdue University Indianapolis (IUPUI) / The Keap1-Nrf2 pathway regulates a wide range of cytoprotective genes, and has been found to serve a protective and beneficial role in many body systems. There is limited information available, however, about its role in bone homeostasis. While Nrf2 activation has been suggested as an effective method of increasing bone mass and quality, there have been conflicting reports which associate Keap1 deficiency with detrimental phenotypes. As Keap1 deletion is a common method of Nrf2 activation, further study should address the impacts of various methods of regulating Nrf2 expression. Also, little research has been conducted on the specific pathways by which Nrf2 activation improves bone quality. In this study, the effects of alterations to Nrf2 activation levels were explored in two specific and varied scenarios. In the first experiment, moderate Nrf2 activation was achieved via partial deletion of its sequestering protein, Keap1, in an aging mouse model. The hypothesis tested here is that moderate Nrf2 activation improves bone quality by affecting bone metabolism and response to mechanical loading. The results of this first experiment suggest a subtle, sex-specific effect of moderate Nrf2 activation in aging mice which improves specific indices of bone quality to varying degrees, but does not affect loading-induced bone formation. It is likely that the overwhelming phenotypic impacts associated with aging or the systemic effects of global Keap1 deficiency may increase the difficulty in parsing out significant effects that can be attributed solely to Nrf2 activation. In the second experiment, a cell-specific knockout of Nrf2 in the osteocytes was achieved using a Cre/Lox breeding system. The hypothesis tested here is that osteocyte-specific deletion of Nrf2 impairs bone quality by affecting bone metabolism and response to mechanical loading. The results of this experiment suggest an important role of Nrf2 in osteocyte function which improves certain indices of bone quality, which impacts male and female bones in different 7 ways, but did not significantly impact loading-induced bone formation. Further studies should modify the method of Nrf2 activation in an effort to refine the animal model, allowing the effects of Nrf2 to be isolated from the potential systemic effects of Keap1 deletion. Future studies should also utilize other conditional knockout models to elucidate the effects of Nrf2 in other specific cell types.

Indiana University-Purdue University Indianapolis (IUPUI) / The aging US population is experiencing a growing incidence of osteoporosis, characterized by increased fracture risk and low bone mass. In skeletal tissue, canonical Wnt signaling is a critical regulator of bone mass, and dysregulation of the Wnt pathway has been implicated in numerous skeletal displasias. Some components of the Wnt signaling pathway have a clear role in bone homeostasis, particularly in the response of bone to altered mechanical environment. Other pathway components are more poorly defined. One important intracellular signal transduction node in the Wnt cascade is β- catenin, which modulates gene expression and cell-cell junctions, among other functions. During periods of disuse, β-catenin is degraded, leading to inhibition of Wnt targets. Here, I characterize the role of β-catenin in bone during a disuse challenge, using a genetic mouse model expressing an inducible constitively-active mutant form of β- catenin in the osteocyte population. I hypothesize that prevention of β-catenin degradation during disuse will prevent the bone wasting effects of mechanodeprivation. As a second goal, I focus on upstream (membrane-bound) modulation of Wnt. Here, I investigate the low-density lipoprotein receptor-related receptor 4 (Lrp4), in the regulation of bone mass and mechanotransduction. I generated an Lrp4 knockin mouse model harboring a missense mutation found among human patients with abnormally high bone mass. I hypothesize that the mutation compromises sclerostin action on bone cells. Understanding how each of these components of the Wnt signaling pathway interact, may lead to novel therapeutic targets for treatment of bone diseases.

A thesis presented for the degree of Doctor of Medicine in the University of the Witwatersrand, Johannesburg / IT2018