Repair of bone defects is a major challenge in orthopaedic surgery. Current bone graft treatments, including autografts, allografts and xenografts, have many limitations making it necessary to develop a biomaterial to be a bone graft substitute. One such biomaterial is bioactive resorbable silica-calcium phosphate nanocomposite (SCPC). SCPC was processed using a 3D rapid prototyping technique and sintered at different temperatures to create porous scaffolds. SEM analyses and mercury intrusion porosimetry showed SCPC to be highly porous with micro- and nanopores. BET analysis indicated that SCPC had high surface area. Mechanical testing demonstrated that SCPC had a compressive strength similar to trabecular bone. Analysis of different thermal treatment temperatures indicated as the temperature was increased, the porosity decreased and the mechanical strength increased. When loaded with rhBMP-2 (SCPC-rhBMP-2), SCPC provided a sustained release profile of rhBMP-2 for 14 days. This was shown to be a greater release than hydroxyapatite (HA)-rhBMP-2. After immersion in SBF, ICP analyses showed the calcium concentration of SBF dropped drastically after one day of immersion. In conjunction, FTIR showed the formation of a hydroxyapatite layer on the SCPC surface and was confirmed by SEM. SCPC thermally treated at 850 ??C demonstrated the greatest dissolution/precipitation reactions when immersed in SBF. Processing the SCPC-rhBMP-2 hybrid using a rapid prototyping technique allowed for an exact replica of the rabbit ulna to be fabricated. This was implanted into a 10 mm segmental defect in the rabbit ulna. CT scans during the healing of the defect showed intimate union between SCPC-rhBMP-2 and the bone and about 65% healing of the defect after 4 weeks. Rabbits were euthanized after 12 and 16 weeks. Digital images show almost complete healing of the defect after 16 weeks. Torsional testing of the ulna after 12 weeks demonstrated restoration of maximum torque and angle at failure. Histological evaluation after 12 weeks showed the regenerated bone has all the morphological characteristics of mature bone. Through in-vitro and in-vivo testing, it can be recommended that the porous bioactive SCPC can serve as a successful delivery system for biological growth factors and serve as an alternative to autologous bone grafting.

The mammalian kidney and reproductive systems both derive from a common embryological origin, the intermediate mesoderm. Abnormal intermediate mesoderm development can result in congenital abnormalities of the urogenital system, yet the molecular mechanisms that govern intermediate mesoderm development are incompletely defined. The spatial and temporal expression of the proteins BMP2 and 4 and their receptor ALK3, in urogenital tissue, suggests a function for BMP-ALK3 signaling in the intermediate mesoderm. It was found that Alk3IM null kidneys display renal hypoplasia, associated with a decrease in kidney size and nephron number. The phenotype of renal hypoplasia in Alk3IM nulls was associated with early decreased number of developing nephron structures and secondary defects in branching morphogenesis. While neither apoptosis nor cell proliferation differed in metanephric mesenchyme cells in Alk3IM nulls, markers of renal progenitor cells were decreased in mutant animals. It was observed that Alk3 expression in the intermediate mesoderm also controls mesonephric tubule number. Alk3IM nulls had fewer mesonephric tubules and fewer derivative Leydig cells. The reduction in Leydig cells resulted in decreased levels in serum testosterone and defects in seminal vesicle formation and fertility. Alk3 expression was also required for normal development of the corpus epididymis. The morphological defects in nephrogenesis were associated with decreased phospho-p38 MAPK expression and in the testis with decreased Phospho-SMAD1/5/8. These results elucidated a requirement for Alk3 signaling in controlling progenitor cells derived from the intermediate mesoderm.

Atherosclerosis is an inflammatory disease, occurring preferentially in arterial regions with disturbed flow. We have shown that disturbed flow induces inflammation in endothelial cells (ECs) by producing bone morphogenic protein-4 (BMP4). Moreover, chronic BMP4 infusion induces endothelial dysfunction and systemic hypertension in mice. Here, we examined which BMP receptors (BMPR) mediate BMP4 action in ECs. Western blot, immunostaining and RT-PCR studies using human and bovine ECs, mouse aortas and human coronary arteries (HCA) showed that BMPRI (ALK2 and 6) and BMP-RII were expressed in ECs. As a functional test, ECs were treated with a BMPRII siRNA to knockdown expression. BMPRII knockdown blocked a well-known BMP4 response - smad1/5/8 phosphorylation, as expected. Unexpectedly, BMPRII knockdown itself significantly stimulated ICAM-1 and VCAM-1 expression and monocyte adhesion in a BMP4-independent manner. Inflammatory responses caused by BMPRII knockdown were blocked by inhibitors of NADPH oxidase and NFκ B. From these results, we hypothesized that BMP-RII knockdown in ECs would cause inflammation, which is a critical event in atherosclerosis initiation and progression. Genetic mutations of BMPRII have been linked to primary pulmonary hypertension. However, it is not known whether BMP-RII is regulated by atherosclerotic conditions and plays a role in non-pulmonary vessels causing inflammation and atherosclerosis. We examined BMPRII levels in HCA by immunostaining. While non-diseased arteries showed intense staining of BMPRII, the expression decreased as lesions became more advanced. BMPRII was virtually undetectable in the most advanced lesions. These findings suggested a potential link between pro-atherosclerotic conditions and BMP-RII levels. We tested this hypothesis by treating ECs with pro-inflammatory cytokines found in atheromas: TNFα decreased BMPRII by 2-fold. In contrast, statins increased BMPRII by 4-fold. In summary, we demonstrate for the first time that BMPRII can be down- or up-regulated by pro- or anti-atherogenic conditions, respectively, and it is dramatically decreased in HCA with advanced plaques. Moreover, BMPRII knockdown in ECs induces inflammation, a critical atherogenic step. We propose that focal inflammation initiated by disturbed flow, together with circulating pro-atherogenic risk factors, may lead to a vicious cycle of BMPRII down-regulation causing secondary inflammation and atheroma progression.

[Truncated abstract] Bone is a living tissue and is maintained by the coordinate action of osteoblasts and osteoclasts. The intercellular communication between these two cells is the quintessential mechanism in bone remodelling. Unfortunately, the importance of this interaction is often neglected and its significance is only realised when disruption of this “cross-talk” results in debilitating bone diseases. Additionally, the number of known proteins that are involved in this “cross-talk”, especially those that are osteoclast-derived, and act specifically on osteoblasts, is limited. This discrepancy leads to the question: Can osteoclasts directly control the growth and function of osteoblastic cells by expressing specific proteins that bind directly to osteoblasts? If so, is it possible to use these proteins to control and, possibly, treat bone disease? The objective of this thesis is to identify and characterise osteoclast-derived factors that can modulate bone homeostasis, as well as contribute to the intercellular communication between osteoblasts and osteoclasts ... Collectively, the data in this thesis culminates in one important conclusion: the identification of a novel paracrine secretory factor that has the potential to directly induce the formation of bone. These findings represent the first ever characterisation of a protein that allows the osteoclasts to directly control the growth and function of osteoblasts. Due to the potential function of ODOF to induce bone formation, this protein may be used therapeutically to treat bone disease.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2001. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 202-229). Also available in print.

Thesis (Ph.D. in Neuroscience) -- University of Colorado Denver, 2008. / Includes bibliographical references (leaves 112-120). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;

Thesis (Ph. D.)--Cornell University, May, 2009. / Vita. Includes bibliographical references (leaves 152-178).

Thesis (Ph. D.)-- University of Washington, 2005. / Includes bibliographical references (leaves 107-127).