Detection Of Biomaterial In Vivo Microenvironment Ph E Ph And Its Effect On Bone Defect Regeneration Under Unbalanced Bone Remodling Condition

This dissertation, "Detection of Biomaterial in Vivo Microenvironment PH (μe-pH) and Its Effect on Bone Defect Regeneration Under Unbalanced Bone Remodling Condition" by Wenlong, Liu, 刘文龙, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: In scenario of osteoporotic fracture, significantly higher activity of osteoclasts than osteoblasts may lead to continuous loss of bone in fracture/defect site. The impaired bone regeneration efficiency is the major barrier that influences endosseous implants to get a better performance, and this substantially increases the risk of a second fracture, non-union and aseptic implant loosening. Currently, there are no clinically approved biomaterials specifically tailored for applications in osteoporotic bones, and it is a challenging topic for material scientists to design proper orthopaedic biomaterials with biological functions for osteoporotic patients. The key issue for developing such biomaterials is to re-establish normal bone regeneration at the fracture site. According to the literatures, acid-base equilibrium is one of the most important factors that influence behaviours of bone cells. Therefore, microenvironment pH (μe-pH), which is influenced by implants biodegradation, may play a crucial role in guiding the localized bone regeneration. We then propose to reconstruct the regeneration balance by controlling the μe-pH through the application of biodegradable materials. The aims of this study include: 1. Establish a method for in vivo μe-pH detection; 2. Evaluate the effect of μe-pH on early-stage bone regeneration process; 3. Reveal the mechanisms by examining osteoclasts behavior in response to the change of μe-pH. The measurement of in vivo μe-pH was realized by using the pH microelectrode. Alkaline biodegradable materials generated an in vivo μe-pH which was higher than the normal physiological value, in particular, at the initial stage. The preliminary results indicated that osteoclasts may play important roles in the early-stage of defect healing process. Therefore, in order to further study the osteoclasts behaviors in response to the elevated μe-pH in a bone marrow microenvironment, a boneimplant interaction mouse model and a borosilicate glass system (with μe-pH gradient) with same type of ions and similar composition were developed. Based on our in vitro data, osteoclasts differentiation and pit-formation activity were significantly suppressed when RANKL-stimulated RAW264.7 cells were cultured in different glasses extracts which were adjusted to higher pH conditions (pH 7.59-8.02). Furthermore, the abnormal osteoclastogenesis potential of bone marrow cells in mouse after hindlimb unloading treatment could also be balanced by the elevated culture media pH (pH 7.62-7.84). In vivo, significantly suppressed osteoclasts activity together with a thicker new bone on materials surface were observed for glasses with higher e-pHs. Further assessments by using RT-PCR and immunostaining indicated that the decreased activity of matrix-degrading proteases (e.g. cathepsin K) may be one of the reasons for the suppressed osteoclasts activity under higher μe-pH conditions. In conclusion, the impaired regeneration process under osteoporotic or immobilized conditions may be ameliorated by adjusting the materials to generate a weakly-alkaline microenvironment. And the e-pH is an important and accessible factor which should be taken into consideration in the development of orthopaedic biomaterials, in particular for repair of osteoporotic bone fracture /defect. Subjects:

This dissertation, "Detection of Biomaterial in Vivo Microenvironment PH (μe-pH) and Its Effect on Bone Defect Regeneration Under Unbalanced Bone Remodling Condition" by Wenlong, Liu, 刘文龙, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: In scenario of osteoporotic fracture, significantly higher activity of osteoclasts than osteoblasts may lead to continuous loss of bone in fracture/defect site. The impaired bone regeneration efficiency is the major barrier that influences endosseous implants to get a better performance, and this substantially increases the risk of a second fracture, non-union and aseptic implant loosening. Currently, there are no clinically approved biomaterials specifically tailored for applications in osteoporotic bones, and it is a challenging topic for material scientists to design proper orthopaedic biomaterials with biological functions for osteoporotic patients. The key issue for developing such biomaterials is to re-establish normal bone regeneration at the fracture site. According to the literatures, acid-base equilibrium is one of the most important factors that influence behaviours of bone cells. Therefore, microenvironment pH (μe-pH), which is influenced by implants biodegradation, may play a crucial role in guiding the localized bone regeneration. We then propose to reconstruct the regeneration balance by controlling the μe-pH through the application of biodegradable materials. The aims of this study include: 1. Establish a method for in vivo μe-pH detection; 2. Evaluate the effect of μe-pH on early-stage bone regeneration process; 3. Reveal the mechanisms by examining osteoclasts behavior in response to the change of μe-pH. The measurement of in vivo μe-pH was realized by using the pH microelectrode. Alkaline biodegradable materials generated an in vivo μe-pH which was higher than the normal physiological value, in particular, at the initial stage. The preliminary results indicated that osteoclasts may play important roles in the early-stage of defect healing process. Therefore, in order to further study the osteoclasts behaviors in response to the elevated μe-pH in a bone marrow microenvironment, a boneimplant interaction mouse model and a borosilicate glass system (with μe-pH gradient) with same type of ions and similar composition were developed. Based on our in vitro data, osteoclasts differentiation and pit-formation activity were significantly suppressed when RANKL-stimulated RAW264.7 cells were cultured in different glasses extracts which were adjusted to higher pH conditions (pH 7.59-8.02). Furthermore, the abnormal osteoclastogenesis potential of bone marrow cells in mouse after hindlimb unloading treatment could also be balanced by the elevated culture media pH (pH 7.62-7.84). In vivo, significantly suppressed osteoclasts activity together with a thicker new bone on materials surface were observed for glasses with higher e-pHs. Further assessments by using RT-PCR and immunostaining indicated that the decreased activity of matrix-degrading proteases (e.g. cathepsin K) may be one of the reasons for the suppressed osteoclasts activity under higher μe-pH conditions. In conclusion, the impaired regeneration process under osteoporotic or immobilized conditions may be ameliorated by adjusting the materials to generate a weakly-alkaline microenvironment. And the e-pH is an important and accessible factor which should be taken into consideration in the development of orthopaedic biomaterials, in particular for repair of osteoporotic bone fracture /defect. Subjects:

Biomaterials Effect on the Bone Microenvironment Practical resource on clinical bone regeneration from a variety of related interdisciplinary researchers Biomaterials Effect on the Bone Microenvironment focuses on the structure-activity relationship between bone biomaterials and microenvironment regulation, presenting a systematic exposition from all aspects of biomaterials regulated microenvironment in bone regeneration and covering design strategies, applications, and mechanisms of biomaterials that regulate bone microenvironment, along with the methods for manufacturing biomaterials and their clinical translation. The subject’s potential challenges and future development direction are discussed, and the design and initiative principle of tailored biomaterials with various features, including bioactive components and physicochemical property, are elucidated in depth. Numerous biomaterials, including natural and synthetic, are summarized and compared. Their advantages and features are also evaluated, particularly in bone microenvironmental regulation and bone generation. Moreover, the stimulation mechanism of the microenvironment to bone generation is discussed in detail, including mechanical-support effect, redox effect, pro-angiogenesis effect, inflammatory immune effect, and anti-aging effect. Biomaterials Effect on the Bone Microenvironment provides further coverage of sample topics such as: Role of bone microenvironment and its associated biomaterials in modulation bone diseases, reviewing the biomaterials used to regulate bone microenvironment Relationship between biological factors of various materials and physiological functions in bone microenvironment Application of the third generation of biomaterials, which would regenerate the bone to regulate bone microenvironment Emerging biological material manufacturing technology and mechanisms of novel biomaterial modulating microenvironment for bone regeneration Future outlook of bone tissue engineering along with the general process of bone remodeling and regeneration With comprehensive coverage of one of the most promising and valuable candidates for clinical bone regeneration, Biomaterials Effect on the Bone Microenvironment is an ideal resource for materials scientists, biotechnologists, biochemists, bioengineers, orthopedists, and clinical chemists who want to stay on the cutting edge of this rapidly evolving field.

Principles of Bone Regeneration is a timely publication that addresses the modern aspects of bone healing and repair. This exciting new volume details the convergence of the different experimental and clinical approaches designed for the study and treatment of bone healing in its diverse forms and under varying conditions. Bone healing is affected by a multitude of genetic, environmental, mechanical, cellular and endocrine variables which eventually lead to changes in gene expression that enhance the guided action of osteoblasts (and chondroblasts) to lay down bone that restores, or even improves, the skeletal load bearing capacity. Recent breakthroughs in understanding the regulatory aspects of bone formation and resorption, in both research and clinical arenas offer new modalities to induce, enhances and guide repair processes in bone for the benefit of millions of patients with conditions such as nonunion fractures, critical size defects, orthodontic tooth movement, periodontal bone loss, intraosseous implants and deformed bones.

This book presents a state-of-the-art review of the latest advances in developing calcium- phosphate bone cements and their applications. It covers the synthesis methods, characterization approaches, material modification and novel binders, as well as the fabrication technologies of calcium-phosphate-based biomaterials in regenerative medicine and their clinical applications. It also highlights methodologies for fabricating scaffolds, biofunctional surfaces/interfaces and subsequently modulating the host response to implantable/injectable materials, and integrates a series of discussions and insights into calcium-phosphate cements and constructs in bone regenerative medicine. As such, the book not only covers the fundamentals but also opens new avenues for meeting future challenges in research and clinical applications.

This book provides comprehensive coverage of smart biomaterials and their potential applications, a field that is developing at a very rapid pace. Because smart biomaterials are an emerging class of biomaterials that respond to small changes in external stimuli with large discontinuous changes in their physical properties, they have been designed to act as an “on–off” switch for, among others, bio separation, immunoanalysis, drug delivery technologies, gene therapy, diagnostics, bio sensors and artificial muscles. After an introduction to the topic and the history of smart biomaterials, the author gives the reader an in-depth look at the properties, mechanics, and characterization of smart biomaterials including hydrogels, particles, assemblies, surfaces, fibers and conjugates. Information on the wide range of applications for these materials follows, including drug delivery, tissue engineering, diagnostics, biosensors, bio separation and actuators. In addition, recent advances in shape memory biomaterials as active components of medical devices are also presented.

Histotechnology and histomorphometry are the major methodologies in bone and cartila- related research. Handbook of Histology Methods for Bone and Cartilage is an outgrowth of the editors’ own quest for information on bone and cartilage histology and histomorphometry. It is designed to be an experimental guide for personnel who work in the areas of basic and clinical bone and cartilage, orthopedic, or dental research. It is the first inclusive and organized reference book on histological and histomorphometrical techniques on bone and cartilage specimens. The topic has not previously been covered adequately by any existing books in the field. Handbook of Histology Methods for Bone and Cartilage has six major parts and is designed to be concise as well as inclusive, and more practical than theoretical. The text is simple and straightforward. Large numbers of tables, line drawings, and micro- or macro-photographs, are used to help readers better understand the content. Full bibliographies at the end of each chapter guide readers to more detailed information. A book of this length cannot discuss every method for bone and cartilage histology that has been used over the years, but it is hoped that major methods and their applications have been included.

The last decade has seen a tremendous advance in our understanding of bone biology. The genes responsible for the majority of rare inherited bone disorders have been identified and much progress has been made in the identification of genes in polygenic disorders such as Paget’s disease and complex multigene diseases such as osteoporosis. Transgenic technology has identified further genes, sometimes unexpectedly, with profound effects on bone. This wealth of new genetic information will undoubtedly lead to extensive cell biological studies to understand the mechanisms by which these gene products affect bone mass and bone strength. In Bone Research Protocols a catalogue of protocols has been assembled to perform such mechanistic studies. In the tradition of the Methods in Molecular Medicine series, the chapters are practical laboratory protocols that should enable the reader to carry out the techniques from scratch. To our knowledge this is the first time such a truly practical manual on well-established bone methods has been assembled, and this volume aims to be complementary to and follow on from the more theoretical Methods in Bone Biology, edited by Arnett and Henderson (1).