Thesis (M.S.)--Universirt of Michigan, 1996. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 2002. / Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 2001. / Includes bibliographical references.

O estudo de biomateriais aplicados à cicatrização levou à modalidade do tratamento chamada de regeneração tecidual guiada (RTG). A RTG reconstitui novos tecidos usando membranas como barreira de proteção da área defeituosa, impedindo a invasão de outros tecidos, especialmente dos tecidos conjuntivos fibrosos. Em outras palavras, a RTG é uma forma de isolar o tecido ósseo do tecido mole, resultando dessa forma em uma ótima condição para a formação óssea. Atualmente, mais de 20 tipos diferentes de polímeros são usados em aplicações biomédicas, e entre eles está o colágeno, polímero ao qual, pela sua hidrólise parcial pode-se obter a gelatina. A gelatina é um polipeptídeo biodegradável, biocompatível, que apresenta anti-genicidade, plasticidade e elasticidade. A prata tem seu efeito antimicrobiano bem conhecido, com utilidade em diferentes campos da medicina, odontologia e biomateriais. Nesse contexto, este trabalho desenvolve e estuda o comportamento das membranas de gelatina e membranas de gelatina com prata para aplicações em RTG. As Membranas de gelatina foram obtidas com concentração de 4% em massa e as membranas de gelatina com prata foram obtidas nas concentrações de 0,01%, 0,05% e 0,1% da solução. Na etapa de reticulação, as membranas secas foram imersas em solução tampão de fosfato de sódio com concentrações de glutaraldeído (GTA) a 0,5%, 1% e 2%, 24 horas. O ensaio de intumescimento foi realizado em membranas reticuladas e não reticuladas, pesadas e imersas em solução tampão de fosfato pH 7,4 por períodos de 5 minutos, 15 minutos, 30 minutos, 1 hora, 3 horas, 22 horas e 24 horas e durante 8 semanas. Obteve-se membranas de gelatina com prata mediante a metodologia de adição da solução de Ag compravada pelas técnicas de DRX, FTIR, MEV e pelo teste de halo de inibição. As membranas reticuladas apresentaram menor valor de porcentagem de intumescimento quanto maior foi a concentração do agente reticulante, com exceção das amostras com concentração de 0,1M de prata. Além da atuação do GTA a prata também interfere no processo de intumescimento, aspecto e comportamento das membranas de gelatina. O efeito bactericida foi avaliado utilizando ensaio de cultura de bactérias - Teste de halo de inibição, onde as membranas de gelatina com Ag apresentaram efeito bacteriostático contra bactéria Gram positiva e Gram negativa. / The study of biomaterials applied to healing led to the treatment modality called guided tissue regeneration (GTR). The RTG reconstruct new tissue using the membranes as a barrier to protect the defective area, preventing the invasion of other tissues, especially connective tissue fibers. In other words, the RTG is a way of isolating the bone tissue of the soft tissue, thereby resulting in an excellent condition for bone formation. Currently, more than 20 different types of polymers are used in biomedical applications, and among them is the collagen polymer to which, by its partial hydrolysis can get the gelatin. Gelatin is a polypeptide biodegradable, which has antigenicity, plasticity and elasticity. Silver has antimicrobial effect well known, are useful in different fields of medicine, dentistry and biomaterials. In this context, this paper develops and studies the behavior of membranes of gelatin and gelatin silver membranes for applications in RTG. Membranes were obtained with gelatin concentration of 4% by weight and gelatin silver membranes were obtained at concentrations of 0.01%, 0.05% and 0.1% of the solution. In the crosslinking step, the dried membranes were immersed in sodium phosphate buffer to concentrations of glutaraldehyde (GTA) at 0.5%, 1% and 2% 24 hours. The swelling test was performed on crosslinked and uncrosslinked membranes, weighed and immersed in phosphate buffer pH 7.4 for a period of 5 minutes, 15 minutes, 30 minutes, 1 hour, 3 hours 22 hours and 24 hours, and for 8 weeks. Obtained gelatin membranes with silver by the method of adding the solution of Ag proven by XRD techniques, FTIR, SEM and the zone of inhibition test. The crosslinked membranes had lower percentage of swelling the higher the concentration of crosslinking agent, except for the samples with a concentration of 0.1 M silver. In addition to operating the GTA silver also interferes with the process of swelling, appearance and behavior of gelatin membranes. The bactericidal effect was evaluated by bacterial culture test - Test of inhibition zone, where the gelatin membrane with Ag Ag exhibited bacteriostatic effect exhibited against Gram positive and Gram negative.

Huang, Li. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 162-194). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

To correct, improve, and maintain tissues, and their functions, are common denominators in tissue engineering and reconstructive plastic surgery. This can be achieved by using autolo-gous tissues as in flaps or transplants. However, often autologous tissue is not useable. This is one of the reasons for the increasing interest among plastic surgeons for tissue engineering, and it has led to fruitful cross-fertilizations between the fields. Tissue engineering is defined as an interdisciplinary field that applies the principles of engineering and life sciences for development of biologic substitutes designed to maintain, restore, or improve tissue functions. These methods have already dramatically improved the possibilities to treat a number of medical conditions, and can arbitrarily be divided into two main principles: > Methods where autologous cells are cultured in vitro and transplanted by means of a cell suspension, a graft, or in a 3-D biodegradable matrix as carrier. > Methods where the tissue of interest is stimulated and given the right prerequisites to regenerate the tissue in vivo/situ with the assistance of implantation of specially designed materials, or application of substances that regulate cell functions - guided tissue regeneration. We have shown that human mammary epithelial cells and adipocytes could be isolated from tissue biopsies and that the cells kept their proliferative ability. When co-cultured in a 3-D matrix, patterns of ductal structures of epithelial cells embedded in clusters of adipocytes, mimicking the in vivo architecture of human breast tissue, were seen. This indicated that human autologous breast tissue can be regenerated in vitro. The adipose tissue is also generally used to correct soft tissue defects e.g. by autologous fat transplantation. Alas 30-70% of the transplanted fat is commonly resorbed. Preadipocytes are believed to be hardier and also able to replicate, and hence, are probably more useful for fat transplantation. We showed that by using cell culture techniques, significantly more pre-adipocytes could survive and proliferate in vitro compared to two clinically used techniques of fat graft handling. Theoretically, a biopsy of fat could generate enough preadipocytes to seed a biodegradable matrix that is implanted to correct a defect. The cells in the matrix will replicate at a rate that parallels the vascular development, the matrix subsequently degrades and the cell-matrix complex is replaced by regenerated, vascularized adipose tissue. We further evaluated different biodegradable scaffolds usable for tissue engineering of soft tissues. A macroporous gelatin sphere showed several appealing characteristics. A number of primary human ecto- and mesodermal cells were proven to thrive on the gelatin spheres when cultured in spinner flasks. As the spheres are biodegradable, it follows that the cells can be cultured and expanded on the same substrate that functions as a transplantation vehicle and scaffold for tissue engineering of soft tissues. To evaluate the in vivo behavior of cells and gelatin spheres, an animal study was performed where human fibroblasts and preadipocytes were cultured on the spheres and injected intra-dermally. Cell-seeded spheres were compared with injections of empty spheres and cell suspensions. The pre-seeded spheres showed a near complete regeneration of the soft tissues with neoangiogenesis. Some tissue regeneration was seen also in the ‘naked’ spheres but no effect was shown by cell injections. In a human pilot-study, intradermally injected spheres were compared with hyaluronan. Volume-stability was inferior to hyaluronan but a near complete regeneration of the dermis was proven, indicating that the volume-effect is permanent in contrast to hyaluronan which eventually will be resorbed. Further studies are needed to fully evaluate the effect of the macroporous gelatin spheres, with or without cellular pre-seeding, as a matrix for guided tissue regeneration. However, we believe that the prospect to use these spheres as an injectable, 3D, biodegradable matrix will greatly enhance our possibilities to regenerate tissues through guided tissue regeneration. / On the day of the defence date the status of article V was In Press.

Regenerative medicine is an interdisciplinary field which has advanced with the use of biotechnologies related to biomaterials, growth factors, and stem cells to replace or restore damaged cells, tissues, and organs. Among various therapeutic approaches, cell-based therapy is most challenging and exciting for both scientists and clinicians pursuing regenerative medicine. Specifically, stem cells, including mesenchymal stem cells and adipose-derived stem cells, are promising candidate cell types for cell-based therapy because they can differentiate into multiple cell types for tissue regeneration and stimulate other cells through neovascularization or paracrine signaling. Also, for effective treatment using stem cells, the tissue engineered constructs, such as bioactive degradable scaffolds, that provide the physical and chemical cues to guide their differentiation are incorporated with stem cells before implantation. Also, it was previously demonstrated that tissue-engineered matrices can promote tubulogenesis and differentiation of stem cells to vascular cell phenotypes. Hence, during tissue regeneration after stem cell therapy, there are numerous factors that need to be monitored. As a result, imaging-based stem cell tracking is essential to evaluate the distribution of stem cells as well as to monitor proliferation, differentiation, and interaction with the microenvironment. Therefore, there is a need for a stem cell imaging technique that is not only noninvasive, sensitive, and easy to operate, but also capable of quantitatively assessing stem cell behaviors in the long term with high spatial resolution. Therefore, the overall goal of this research is to demonstrate a novel imaging method capable of continuous in vitro assessment of stem cells as prepared with tissue engineered constructs and noninvasive longitudinal in vivo monitoring of stem cell behaviors and tissue regeneration after stem cell implantation. In order to accomplish this, gold nanoparticles are demonstrated as photoacoustic imaging contrasts to label stem cells. In addition, ultrasound and photoacoustic imaging was utilized to monitor stem cells and neovascularization in the injured rat tissue. Therefore, using these methods, tissue regeneration can be promoted and noninvasively monitored, resulting in a better understanding of the tissue repair mechanisms following tissue injury. / text

It has been suggested that some adult bone marrow cells (BMC) can localize to the injured tissues and develop tissue-specific characteristics including those of the pulmonary epithelium. In Chapter 2 we show that the combination of mild airway injury as a conditioning regimen to direct the site of BMC localization and transtracheal delivery of short-term cultured BMC enhances airway localization and adoption of an epithelial-like phenotype expressing Clara cell secretory protein (CCSP) and pro-surfactant protein-C. Bone marrow cells from transgenic mice expressing green fluorescent protein driven by the epithelial-specific cytokeratin-18 promoter were injected transtracheally into airway-injured wild-type recipients. BMC retention in the lung was observed to be at least 120 days following cell delivery with increasing transgene expression over time. The results indicate that targeted delivery of BMC can promote airway regeneration. Although bone marrow stem/progenitor cells can develop into lung epithelial cells, the specific subpopulation remains unknown. In Chapter 3 we identify a newly discovered population of murine and human BMC that express CCSP. These CCSP+ cells increase in the bone marrow and blood after airway injury and can be expanded in culture. CCSP+ cells are unique in that they express both hematopoietic and mesenchymal stromal cell markers and can give rise to various lung epithelial lineages in vitro. Importantly, bone marrow transplant of CCSP+ cells to CCSP knockout recipients confirms that bone marrow CCSP+ cells contribute to airway epithelium after airway injury. In Chapter 4 we enrich for a stem/progenitor cell population within the CCSP+ using the stem cell antigen (Sca)-1 as a marker. Here we identified a putative epithelial stem/progenitor cell that can be induced to differentiate into various lung epithelial cell lineages expressing markers exclusive to airway or alveolar epithelial cells when cultured under an air liquid interface. These cells also have self-renewal potential in vitro that can proliferate in vivo and repopulate the injured airway epithelium. This newly discovered epithelial-like cells may play a central role in the bone marrow contribution to lung repair and are exciting candidates for cell-based targeted therapy for treatment of lung diseases.

It has been suggested that some adult bone marrow cells (BMC) can localize to the injured tissues and develop tissue-specific characteristics including those of the pulmonary epithelium. In Chapter 2 we show that the combination of mild airway injury as a conditioning regimen to direct the site of BMC localization and transtracheal delivery of short-term cultured BMC enhances airway localization and adoption of an epithelial-like phenotype expressing Clara cell secretory protein (CCSP) and pro-surfactant protein-C. Bone marrow cells from transgenic mice expressing green fluorescent protein driven by the epithelial-specific cytokeratin-18 promoter were injected transtracheally into airway-injured wild-type recipients. BMC retention in the lung was observed to be at least 120 days following cell delivery with increasing transgene expression over time. The results indicate that targeted delivery of BMC can promote airway regeneration. Although bone marrow stem/progenitor cells can develop into lung epithelial cells, the specific subpopulation remains unknown. In Chapter 3 we identify a newly discovered population of murine and human BMC that express CCSP. These CCSP+ cells increase in the bone marrow and blood after airway injury and can be expanded in culture. CCSP+ cells are unique in that they express both hematopoietic and mesenchymal stromal cell markers and can give rise to various lung epithelial lineages in vitro. Importantly, bone marrow transplant of CCSP+ cells to CCSP knockout recipients confirms that bone marrow CCSP+ cells contribute to airway epithelium after airway injury. In Chapter 4 we enrich for a stem/progenitor cell population within the CCSP+ using the stem cell antigen (Sca)-1 as a marker. Here we identified a putative epithelial stem/progenitor cell that can be induced to differentiate into various lung epithelial cell lineages expressing markers exclusive to airway or alveolar epithelial cells when cultured under an air liquid interface. These cells also have self-renewal potential in vitro that can proliferate in vivo and repopulate the injured airway epithelium. This newly discovered epithelial-like cells may play a central role in the bone marrow contribution to lung repair and are exciting candidates for cell-based targeted therapy for treatment of lung diseases.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 205-223).