The number of clinical procedures performed in the USA using bone graft substitutes was estimated at 1.1 million in 2010 and is projected to reach 1.3 million in 2015. This increasing demand for bone graft substitutes is a result of an ever-ageing population coupled with recent reports in the clinical literature of concerns regarding the safety of allograft and recombinant bone morphogenetic proteins such as rh- BMP-2 and the supply of autograft, which has led to an increased clinical interest in synthetic alternatives to allograft; autograft; and recombinant growth factors. One such synthetic material is silicate-substituted hydroxyapatite (SiCaP). Mechanical testing revealed SiCaP to have similar mechanical behaviour to morcellised cancellous bone. In computated spinal and hip models the simulated stresses in SiCaP were determined to be low when in situ, indicating a stressshielding effect from the implanted metalwork and surrounding bone. We also found an inverse relationship between porosity and Young's Modulus. Our results indicated that the strut-porosity of a material substrate should be increased to maximise the potential for formation of a precursor to bone-like apatite after implantation in osseous defects and further confirmed previous reports that betatricalcium phosphate is less bioactive than hydroxyapatite. We demonstrated a direct link between the amount of strut-porosity and the osteoinductivity of SiCaP. We learned that adding a resorbable carrier phase did not impair the osteoinductive potential of SiCaP, suggesting that osteoinductivity is not necessarily determined in the first 24-48 hours post implantation. Most notably from our studies we determined that the osteoinductivity of SiCaP correlated with its performance in orthotopic defects. Our research confirmed our hypothesis that modifying the micron-scale physical structure of a hierarchical porous SiCaP based biomaterial influences its functional performance in vitro and such modifications can be applied to improve its performance outcomes in ectopic and orthotopic treatment sites in vivo.

骨形態發生蛋白（BMPs）是調節小鼠發育中肢體的頂外胚層脊（AER）功能和趾間程序性細胞死亡（PCD）的分泌信號。然而這些信號的細胞內第二信使者的身份不明。本研究旨在分析Smad蛋白在受骨形態發生蛋白調節的頂外胚層（AER）功能和趾間程序性細胞死亡的功用和相互作用。 基因剔除骨形態發生蛋白信號元件，包括細胞內第二信使者和骨形態發生蛋白，會導致早期胚胎死亡。本研究採用Cre/loxP系統，選擇性地在小鼠發展中肢體的頂外胚層脊和腹側外胚層剔除Smad1和/或Smad5基因。 本研究採用Smad1和/或Smad5 floxed等位基因和En1[superscript Cre/]⁺ 敲等位基因。 / 單一選擇性地在發展中肢體的頂外胚層脊和腹側外胚層剔除Smad1或Smad5不會導致肢體畸形。然而，同時選擇性剔除Smad1/Smad5會導致帶子手指和腳趾(syndactyly)。帶子手指和腳趾的形成是因趾間程序性細胞死亡減少和趾間細胞異常增生。 Smad1/Smad5雙突變體的細胞跟踪實驗顯視腹側外胚層增厚和原在腹側的外胚層En1[superscript Cre/]⁺後裔細胞出現異位轉移到背側趾間位置。 在分子水平上，Fgf8在Smad1/Smad5雙突變體趾間外胚層的表達延長至胚胎發育的第十三天(E13)。這異位Fgf8表達可作為一個趾間的上皮細胞和間質細胞的生存信號。本研究結果表明，Smad1和Smad5在骨形態發生蛋白信號中擔當必需角色，它們充當頂外胚層脊和腹側外胚層細胞內骨形態發生蛋白信號的細胞內第二信使者，並互補對方的功用。頂外胚層脊和腹側外胚層的Smad1/Smad5信號調節趾間組織萎縮。因Smad1/Smad5雙突變體在趾間的程序性細胞死亡出現缺陷，它將會是一個研究程序性細胞死亡調節機制的重要模型。 / Bone morphogenetic proteins (BMPs) are secreted signals that regulate apical ectodermal ridge (AER) functions and interdigital programmed cell death (PCD) of developing mouse limb. However, the identities of the intracellular mediators of these signals are unknown. The present study aims at investigating the role and interaction of Smad proteins in BMPs-regulated AER functions in limb development. Inactivation of BMP signaling components, including intracellular mediators and BMP ligands, will lead to early embryonic lethality. To circumvent the problem, Cre/loxP system was employed to inactivate Smad1 and/or Smad5 selectively in AER and ventral ectoderm of developing mouse limb. Smad1 or/and Smad5 floxed alleles and an En1[superscript Cre/]⁺ knock-in allele was employed for the study. / Single inactivation of either Smad1 or Smad5 did not result in limb abnormalities. However, the Smad1/Smad5 double mutants exhibited syndactyly due to a reduction in interdigital PCD and an increase in interdigital cell proliferation. Cell tracing experiments in the Smad1/Smad5 double mutants showed that ventral ectoderm became thicker and the descendents of ventral En1[superscript Cre/]⁺ expressing ectodermal cells were located at dorsal interdigital regions. At the molecular level, Fgf8 expression was prolonged in the interdigital ectoderm of embryonic day (E) 13 Smad1/Smad5 double mutants, suggesting that the ectopic Fgf8 expression may serve as a survival signal for interdigital epithelial and mesenchymal cells. The result suggests that Smad1 and Smad5 are required and function redundantly as intra-cellular mediators for BMP signaling in the AER and ventral ectoderm. Smad1/Smad5 signaling in the AER and ventral ectoderm regulates interdigital tissue regression of developing limb. The mutants with defects in interdigital PCD could also serve as a valuable model for investigation of PCD regulation machinery. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Wong, Yuk Lau. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 121-133). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract of thesis in English --- p.i / Abstract of thesis in Chinese --- p.iii / Acknowledgements --- p.iv / Table of Contents --- p.v / List of Figures --- p.xii / List of Tables --- p.xv / List of Abbreviations --- p.xvi / Chapter Chapter 1 --- General Introduction / Chapter 1.1 --- Limb development: a General Overview --- p.1 / Chapter 1.2 --- Signaling centres and axis determination of developing limb buds --- p.8 / Chapter 1.2.1 --- Apical ectodermal ridge and proximal-distal axis --- p.8 / Chapter 1.2.2 --- The zone of polarizing activity and anterior-posterior axis --- p.8 / Chapter 1.2.3 --- Ectoderm and dorsal-ventral axis --- p.9 / Chapter 1.3 --- Programmed cell death in limb development --- p.10 / Chapter 1.3.1 --- Localization of programmed cell death in developing limb bud --- p.10 / Chapter 1.3.2 --- Functions of programmed cell death in limb development --- p.11 / Chapter 1.4 --- Regulation of programmed cell death in developing mouse limb --- p.12 / Chapter 1.4.1 --- Tissues of limb bud involved in regulation of programmed cell death-question to be answered --- p.12 / Chapter 1.4.2 --- Molecular regulation of programmed cell death in developing mouse limb --- p.12 / Chapter 1.4.3 --- Programmed cell death machinery --- p.14 / Chapter 1.5 --- BMPs signaling and limb development --- p.16 / Chapter 1.5.1 --- Functions of BMPs signaling in limb development --- p.16 / Chapter 1.5.2 --- BMPs signaling cascade --- p.17 / Chapter 1.5.3 --- BMPs signaling and programmed cell death --- p.20 / Chapter 1.5.4 --- Intra-cellular mediators of BMPs signaling in limb programmed cell death-question to be answered --- p.21 / Chapter 1.6 --- Scope of the Thesis --- p.22 / Chapter 1.6.1 --- Central aim of the project --- p.22 / Chapter 1.6.2 --- Specific objectives --- p.24 / Chapter Chapter 2 --- Syndactyly in mice lacking Smad1/Smad5 signaling in ventral ectoderm: Implication for its functions in limb development / Chapter 2.1 --- Confirmation of expression of En1[superscript Cre/]⁺ knock-in allele in AER and ventral ectoderm of developing limb bud --- p.27 / Chapter 2.1.1 --- Introduction --- p.27 / Chapter 2.1.2 --- Material --- p.28 / Chapter 2.1.2.1 --- Mouse lines --- p.28 / Chapter 2.1.2.2 --- Chemicals --- p.28 / Chapter 2.1.3 --- Breeding strategy and methodology --- p.28 / Chapter 2.1.4 --- Result --- p.30 / Chapter 2.1.5 --- Discussion --- p.30 / Chapter 2.2 --- En1[supercript Cre/]⁺ inactivation of the Smad1 and Smad5 conditional alleles in the AER and limb ventral ectoderm --- p.33 / Chapter 2.2.1 --- Introduction --- p.33 / Chapter 2.2.2 --- Material --- p.33 / Chapter 2.2.2.1 --- Mouse lines --- p.33 / Chapter 2.2.2.2 --- Antibodies and chemicals --- p.33 / Chapter 2.2.3 --- Methodology --- p.34 / Chapter 2.2.4 --- Results and discussion --- p.36 / Chapter 2.3 --- Single inactivation of Smad1 or Smad5 conditional null allele in the AER and ventral limb ectoderm does not result in observable limb abnormalities --- p.40 / Chapter 2.3.1 --- Introduction --- p.40 / Chapter 2.3.2 --- Material --- p.40 / Chapter 2.3.2.1 --- Mouse lines --- p.40 / Chapter 2.3.2.2 --- Chemicals --- p.41 / Chapter 2.3.3 --- Breeding strategy and methodology --- p.41 / Chapter 2.3.4 --- Results and discussion --- p.41 / Chapter 2.4 --- Inactivation of both Smad1/Smad5 signaling in the limb AER and ventral ectoderm results in interdigital tissue regression defects --- p.45 / Chapter 2.4.1 --- Introduction --- p.45 / Chapter 2.4.2 --- Material --- p.45 / Chapter 2.4.2.1 --- Mouse lines --- p.45 / Chapter 2.4.2.2 --- Chemicals --- p.45 / Chapter 2.4.3 --- Breeding strategies and methodology --- p.45 / Chapter 2.4.4 --- Results --- p.46 / Chapter 2.4.5 --- Discussion --- p.48 / Chapter 2.5 --- Smad1/Smad5 signaling in the limb AER and ventral ectoderm is required for regulating interdigital cell death and cell proliferation --- p.56 / Chapter 2.5.1 --- Introduction --- p.56 / Chapter 2.5.2 --- Material --- p.56 / Chapter 2.5.3 --- Methodology --- p.57 / Chapter 2.5.3.1 --- Cell death assays --- p.57 / Chapter 2.5.3.2 --- Cell proliferation assays --- p.58 / Chapter 2.5.3.3 --- Statistical analysis --- p.59 / Chapter 2.5.4 --- Result --- p.59 / Chapter 2.5.5 --- Discussion --- p.60 / Chapter 2.6 --- Fgf8 is up-regulated at the interdigital distal ectoderm and serves as survival signal for interdigital mesenchyme upon inactivation of the Smad1/Smad5 signaling in AER and ventral ectoderm --- p.66 / Chapter 2.6.1 --- Introduction --- p.66 / Chapter 2.6.2 --- Material --- p.66 / Chapter 2.6.2.1 --- Material for preparation of DIG-labeled RNA probe --- p.66 / Chapter 2.6.2.2 --- Materials for whole-mount and section in-situ hybridization --- p.67 / Chapter 2.6.3 --- Methodology --- p.67 / Chapter 2.6.3.1 --- Preparation of DIG-labeled RNA probe --- p.67 / Chapter 2.6.3.1.1 --- Transformation of DNA into competent cells --- p.67 / Chapter 2.6.3.1.2 --- Preparation of recombinant plasmid --- p.68 / Chapter 2.6.3.1.2.1 --- Birnboim and Doly method --- p.68 / Chapter 2.6.3.1.2.2 --- QIAGEN column method --- p.68 / Chapter 2.6.3.1.3 --- Preparation of linearized recombinant plasmid for riboprobe preparation --- p.70 / Chapter 2.6.3.1.4 --- Preparation of DIG-labelled riboprobes for in situ hybridization --- p.70 / Chapter 2.6.3.2 --- Whole-mount in situ hybridization --- p.72 / Chapter 2.6.3.3 --- Section in situ hybridization --- p.73 / Chapter 2.6.4 --- Results --- p.74 / Chapter 2.6.5 --- Discussion --- p.75 / Chapter 2.7 --- Mesenchymal BMP signals are not altered in the developing autopod of the Smad1/Smad5 mutants --- p.81 / Chapter 2.7.1 --- Introduction --- p.81 / Chapter 2.7.2 --- Material --- p.81 / Chapter 2.7.3 --- Methodology --- p.81 / Chapter 2.7.4 --- Result and discussion --- p.81 / Chapter 2.8 --- Inactivation of Smad1/Smad5 in AER and ventral ectoderm results in postaxial polydactyly --- p.87 / Chapter 2.8.1 --- Introduction --- p.87 / Chapter 2.8.2 --- Material --- p.87 / Chapter 2.8.3 --- Methodology --- p.87 / Chapter 2.8.4 --- Results and discussion --- p.88 / Chapter 2.9 --- Smad1/Smad5 inactivation in the limb ventral ectoderm resulted in ventral ectoderm thickening and ectopic En1-expressing cells and their descendents in the dorsal interdigital ectoderm --- p.91 / Chapter 2.9.1 --- Introduction --- p.91 / Chapter 2.9.2 --- Material p91 / Chapter 2.9.3 --- Methodology --- p.92 / Chapter 2.9.3.1 --- Breeding scheme --- p.92 / Chapter 2.9.3.2 --- X-gal stainin --- p.92 / Chapter 2.9.3.3 --- Immunofluorescence --- p.93 / Chapter 2.9.4 --- Results --- p.93 / Chapter 2.9.5 --- Discussion --- p.94 / Chapter 2.10 --- Inactivation of both Smad1 and Smad5 in ventral limb ectoderm does not cause defects in dorsal-ventral patterning --- p.99 / Chapter 2.10.1 --- Introduction --- p.99 / Chapter 2.10.2 --- Material --- p.99 / Chapter 2.10.3 --- Methodology --- p.99 / Chapter 2.10.1 --- Whole-mount in situ hybridization --- p.99 / Chapter 2.10.2 --- Histological analysis --- p.99 / Chapter 2.10.4 --- Results --- p.100 / Chapter 2.10.5 --- Discussion --- p.101 / Chapter 2.11 --- Contribution of present study --- p.104 / Chapter Chapter 3 --- Proteomic analysis on developing limbs of Smad1/Smad5 knock-out mutant: potential protein candidates that regulate cell death and cell proliferation / Chapter 3.1 --- Introduction --- p.106 / Chapter 3.2 --- Materials --- p.106 / Chapter 3.3 --- Methodology / Chapter 3.3.1 --- Protein sample preparation of limb --- p.107 / Chapter 3.3.2 --- Protein quantification --- p.107 / Chapter 3.3.3 --- 2D gel electrophoresis --- p.108 / Chapter 3.3.4 --- Image analysis --- p.109 / Chapter 3.3.5 --- In gel digestion and MALDI-TOF MS --- p.109 / Chapter 3.4 --- Results --- p.110 / Chapter 3.5 --- Discussion --- p.111 / Chapter Chapter 4 --- General Discussion and Future Direction / Chapter 4.1 --- The intracellular signaling components of BMP signaling --- p.115 / Chapter 4.2 --- The programmed cell death machinery in BMPs-regulated interdigital programmed cell death --- p.117 / Chapter 4.3 --- The possible involvement of reactive oxygen species in BMPs- regulated interdigital programmed cell death --- p.118 / Chapter 4.4 --- Interaction of BMP signaling and retinoic acid signaling --- p.119 / Chapter 4.5 --- Potential candidate genes regulated by Smad1/Smad5 signaling --- p.119 / Bibliography --- p.121 / Publication --- p.134

Thesis (M.S.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Adults with Intellectual Disability (ID) are at an elevated risk of osteoporosis based on lower peak bone mass and medical characteristics. However, there is little data as to how the medical characteristics affect screening or at what ages people are being screened. Methods: A secondary cross-sectional data analysis of was conducted of 4777 adults witl1 Intellectual Disability to determine characteristics associated with an elevated risk for osteoporosis and receipt of bone density screening. Hypotheses were that increasing age, use of antiseizure medication, living in a 24 hour residential setting, and receiving a flu vaccine increased the likelihood of screening. Bivariate analyses were initially performed, tl1en data were stratified by gender and logistic regressions were performed. Findings: 22.2% of the sample in this study received bone density screening. Bivariate odds ratios identified each of the hypothesized variables as significantly associated with receiving screening. Additionally, many of the covariates analyzed identified significant associations with receiving screening.Data were then stratified by gender and evaluated in a logistic regression. In men, increasing age, tl1e use of antiepileptic medication (adjusted odds ratio (OR) 1.5; 95% confidence interval (CI) 1.2-2.0), and receiving the flu vaccine (adjusted OR 1.5; 95% CI 1.2-2.0) were associated witl1 an increased likelihood of screening, controlling for confounding. Living in a 24 hour residential setting was not significantly associated with screening (adjusted OR 1.2; 95% CI 0.91-1.6). In women, increasing age, the use of antiepileptic medication (adjusted OR 1.5; 95% CI 1.2-1.9), receiving the flu vaccine (adjusted OR 1.4; 95% CI 1.1-1.8), and living in a 24 hour residential setting (adjusted OR 1.4; 95% CI 1.1 -1.8) were all significantly associated with receiving screening. A history of Down syndrome, noted to increase risk of osteoporosis, was associated with a decreased likehl1ood of screening (adjusted OR 0.67; 95% CI 0.4 7-0. 94) in women, although it was not a significant association in men. Conclusions: While most variables related to osteoporosis are associated with an increased likelihood of screening, screening rates among in adults witl1 ID were low. Additionally, men and women have differences in variables related to screening. Better education and improved awareness may increase rates. / 2031-01-02

Phosphate (Pi) is essential for healthy bone growth as well as normal fracture repair. Studies have shown that when animals are phosphate deficient normal fracture healing is interrupted. Although phosphate deficiency has been shown to impair fracture healing, it is unknown how different genetic factors interact with phosphate deficiency to disrupt healing. Furthermore, it is unknown if upon replenishing phosphate in the diet healing will be re-initiated or if the deficiencies will persist irreversibly to prolong the healing of the bones. To assess how genetic factors interact with phosphate deficiency, fractures were generated in three genetically distinct strains of mice that had previously been shown to have different patterns of endochondral bone formation. Phosphate deficiency was initiated two days prior to fracture and was then maintained for a 15 day period covering the normal duration of endochondral bone development. To assess if replenishing phosphate could rescue genetic expression of deficient healing, normal phosphate was re-introduced into the diet after 15 days of deficiency and bone healing was allowed to continue until 35 days post fracture. Messenger RNA expression for marker genes for cartilage and bone formation was assessed by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) analysis over this time course of healing. Structural properties, callus mineralization and cartilage contents were assessed by micro-computed tomography and contrast agent enhanced micro- computed tomography (CECT). Torsional mechanical testing was used to measure bone strength. To assess if replenishing phosphate could rescue mineralization and biomechanical properties of deficient healing, normal phosphate was re-introduced after 15 days of deficiency and bone healing was allowed to continue until 21 days post fracture. The biological assessment of fracture healing showed that all three genetic strains had impaired expression of both cartilage and bone associated genes during the period of phosphate deficiency. Once phosphate was returned to the diet, however, the osteogenesis genes showed a burst of late expression in all three strains. Interestingly, torsional testing of the bones showed that phosphate deficient/replenished groups were all stronger but also more brittle than the bones of control mice. Micro-computed tomography demonstrated that bone mineral density was slightly higher in the phosphate deficient mice but the bone mineral density standard deviation in the calluses were also higher indicating that the mineralization within the healing calluses was unevenly distributed in the phosphate deficient/replenished group. Lastly, contrast agent enhanced computed tomography data showed that the overall callus tissue mineral density was lower in phosphate deficient/replenished calluses due to the greater cartilage in the phosphate deficient/replenished calluses. These results suggest that the increase strength in the phosphate deficient/replenished calluses is due to the burst of expression in osteogenesis genes that led to the rapid mineralization of the fracture gap in order to compensate for fracture instability due to the phosphate restriction. They also show that a gross metabolic alteration supersedes all other aspects of genetic variably in endochondral development. Finally, they show that even though fracture healing may be greatly delayed by phosphate deficiency, replacement of phosphate after deficiency leads to rapid regain in function. Future studies need to be carried out to determine if longer time lengths of phosphate deficiency can be rescued upon reintroduction of phosphate.

The bones of the body vary in size and shape, but are fundamentally all composed of the same cell types: osteoblasts, osteoclasts, osteocytes, vascular cells, and sometimes marrow cells. Long bones are formed when mesenchymal stem cells (MSCs) give rise to chondrocytes i.e. cartilage cells, and osteoblasts i.e. bone cells. These develop to form layers of bone encasing a cartilagenous core which eventually becomes the marrow cavity. A recent study showed that deleting the Wilms’ tumour gene, Wt1, in adult mice causes a dramatic loss of bone and fat tissue, fat being another derivative of MSCs. This finding led me to ask whether Wt1 expression is involved in bone biology and whether it plays a functional role in the stem or progenitor populations. Wt1 is a transcription factor that acts as a mesodermal / mesenchymal regulator. It acts as a tumour suppressor gene with mutations leading to the eponymous paediatric kidney tumour. However, in adult cancers it has oncogene characteristics, being highly expressed in the tumours of tissues in which it is not normally present. It also plays a pivotal role in the epithelial to mesenchymal transition (EMT) and vice versa in developing heart and kidney, respectively. There is, however, no evidence of its involvement with EMT / MET in adults. Wt1 is expressed in various developing tissues and is particularly vital for kidney development. Due to its involvement as a regulator of EMT / MET during development and the phenotype observed following its deletion in vivo, we hypothesised that Wt1 is expressed in, and required for the function of mesenchymal stem or progenitor cells populations within the bone marrow. A Wt1-GFP knock in mouse was used to show that Wt1 expressing cells are found in the bone marrow, and also for the first time in the bone. The GFP population overlaps with a non-haematopoietic MSC population defined by 3 cell surface markers in the bone and marrow, as well as an osteoblast (OB) progenitor population. Using a tamoxifen inducible CreERT2 showed that Wt1 loss alters the proportion of GFP cells in the bone and marrow cells that overlap with these MSC and OB progenitor markers, but microarrays were needed to assess the functional effects of Wt1 deletion. Microarrays highlighted various pathways that were altered following the in vitro deletion of Wt1 in total bone and marrow culture, as well as the non-haematopoeitic GFP+ and GFP- populations. In bone cells, deleting Wt1 negatively affects various pathways related to MSCs and their derivatives, including collagen biosynthesis, cartilage development and muscle tissue development. Also negatively affected were Wnt signalling regulation and EMT regulation; this is the first time Wt1 has been shown to be involved in EMT in adult cells. These findings were validated using qRT-PCR to show the down regulation of various genes involved in each pathway, showing that as well as being expressed in these populations it is also playing a functional role. Ossification pathways were negatively altered in the cells not expressing Wt1 following the deletion of the gene suggesting that Wt1 may also be acting in a paracrine manner to play its role in bone homeostasis. As well as in adult tissues, Wt1 was found to be expressed during development in the limb tissue of e11.5 to e16.5 mice. Preliminary results show that Wt1 may also have a functional role during bone development, as loss of expression causes a reduction in the percentage of non-haematopoetic MSC cells in the e18.5 hindlimb. As well as this, preliminary lineage tracing experiments suggest that cells found at the bone surface are of Wt1+ origin. This thesis has also highlighted the importance of experimental conditions and controls, particularly for CFU-F assays. CreERT2, loxP sites, tamoxifen, oxygen tension levels, and gender all exert specific effects on colony formation, independent of Wt1 expression. In conclusion, these data identify Wt1 as a key player in bone development and homeostasis. The microarray results led to the conclusion that Wt1 has a functional role in several mesenchymal pathways and highlights various genes that are potential Wt1 targets and should be further investigated using ChIP-Seq methods.

Osteoarthritis (OA) is a debilitating disease that affects millions of people. It is characterized by the degeneration of articular cartilage, narrowing of the joint cavity, damage to the subchondral bone, loss of synovial fluid, and osteophyte formation. These symptoms can cause muscle weakness, decrease in range of motion at the joint, and pain. Pain is the symptom that is most frequently treated. However, pinpointing the exact origin and location that is causative to the pain can be difficult. Patients of OA commonly have areas of subchondral edema identified on an MRI as marrow bone lesions (BML). On a CT image, these BML are found to be areas of bone resorption within the subchondral bone of the affected joint called subchondral bone cysts (SBC). These cysts are hypothesized to be a source of pain in OA as well as progression of the disease. The synovial intrusion theory for cyst formation states that there is a physical connection made between the joint cavity and the SBC through which synovial fluid travels. The bony contusion theory describes micro cracks developing below the articular cartilage within the subchondral bone causing bone necrosis and SBC formation. This study was undertaken to investigate the histological presentation of the contents of the SBC and the surrounding area.Seven human femoral head samples, ranging from age 49-72 years old, from patients who received total hip arthroplasty due to OA were examined. Three areas were sectioned from each femoral head including an area containing a cyst, an area of primary compressive bone, and an area at the medial side of the femoral head. These sections were then stained for bone, cartilage, and nerves and examined histologically. Sclerotic bone was shown to surround each cyst cavity, while cysts were composed of a mixed connective tissue infiltrated with multiple blood vessels and potential nerve fibers. With further investigation of these structures, the location of the nerve fibers within the SBC could be a possible source of pain in OA and a target for future treatments and therapies. Within the femoral head, cysts were found to be both shallow and deep to the articular cartilage. Shallow cysts may support the synovial intrusion theory for cyst formation while deep cysts could support the bony contusion theory. In relation to articular cartilage, cysts were not only found below a degraded articular cartilage surface as expected but also below intact, less degraded cartilage. This in depth look at the cells and tissues present within and surrounding the cyst provides information to better understand the pathology of OA and possibly an alternative method for treating the disease.

This thesis presents an experimental study of a bovine vertebra using transmission and pulse-echo methods and a preliminary investigation to guide a screw insertion into a pedicle using TomoScan phased array unit. The results show the cancellous bone has higher attenuation than the cortical bone for 1.0-5.0 MHz. The optimal frequencies for imaging are found to be 3.5 and 5.0 MHz. When the sample is filled with water with the cancellous core removed, all reflections from the layers and screw are visible; however when the core is present, only reflections from the top cortex are identifiable. For the preliminary study, size and placement of the transducer array are important. When the ultrasound beam is normal to the pedicle surface, echoes from the pedicle layers and the steel bit are strong; otherwise, signals are weak and not even identifiable. Larger aperture size will enhance the signal-to-noise ratio but deteriorate lateral resolution.

Bone is a dynamic tissue that in some cases, due to fractures, infection or interruption of blood supply, does not repair completely, leading to bone loss; therefore it is necessary to recur to bone grafts. However, bone grafts (i.e.autografts) may require additional surgery and present risks associated with potential disease transmission from donor to recipient (i.e.allografts). The limitations of these grafts have encouraged the pursuit of engineered alternatives that are based on the synchronous interplay between biomaterials, biological macromolecules and cells. 3-D gelatin-based scaffolds were prepared and evaluated for their ability to promote osteogenesis. Three types of gelatin based scaffolds were prepared via the crosslinking of gelatin B with glutaraldehyde or EDC/NHS in the presence or absence of PLG . The porosity and pore size of the scaffolds were controlled by varying the freeze-drying temperature (-20°C and -80°C). To promote osteogenesis, human stromal MIAMI cells were incorporated in the scaffolds. Results demonstrated MIAMI cells grew and spread actively throughout gelatin and gelatin/PLG scaffolds after 14 days of incubation. The rate of osteogenic activity was confirmed through histochemical staining for alkaline phosphatase and calcium. Mineral deposition was increased in the gelatin scaffold as opposed to the gelatin/PLG scaffold after at day 35.

The purpose of this study was to develop a fibrin gel system capable of serving as a three dimensional scaffold for the chondrogenesis of rabbit bone marrow mesenchymal stem cells (BM-MSCs) and to examine the effect of two fibrinolytic inhibitors, aprotinin and aminohexanoic acid, on this system. Rabbit BM-MSCs were obtained from the tibias and femurs of New Zealand white rabbits. After chondrogenic potential of BM-MSCs was verified by pellet culture, 2 x 106 cells were pelleted and suspended in fibrinogen (80mg/ml) and then mixed with equal parts of thrombin (5 IU/ml). The specimen were then divided into four groups: aprotinin control (with aprotinin); aprotinin + transforming growth factor (TGF-beta) (with aprotinin and TGF-beta 1); amino control (with aminohexanoic acid); and amino+TGF-beta (with aminohexanoic acid and TGF- beta1). Each of these groups was further divided into three groups depending on the concentration of the inhibitor. Both of the aprotinin groups received 0.0875, 0.175, or 0.35 TIU/ml of aprotinin and both of the aminohexanoic acid groups were supplemented with 2, 4, or 8 mg/ml of aminohexanoic acid. The gels were harvested and analyzed at 7, 14, and 21 days. All of the aprotinin+TGF-beta groups exhibited a significantly higher aggrecan gene expression than control groups whereas only the amino+TGF-â group treated with 8mg/ml was significantly higher than those of the control groups. In addition, the 0.0875 and 0.175 TIU/ml aprotinin+TGF-beta groups exhibited significantly higher levels of expression than the 2 and 4 mg/ml amino+TGF-beta groups. There were no significant differences among the different concentrations of aprotinin or aminohexanoic acid with or without the treatment of TGF-beta. Similar trends were also seen when the glycosaminoglycan (GAG) content was measured and analyzed. These findings suggest that fibrin gels are a suitable environment for the chondrogenesis of BM-MSCs and that aprotinin in combination with TGF-beta1 is the optimal condition for stimulating BM-MSCs to differentiate into chondrocytes.

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: Michelle A. Provost-Craig, Dept. of Health, Nutrition, and Exercise Sciences. Includes bibliographical references.