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- All Subjects: Stem Cells
- All Subjects: Synthetic Biology
- Creators: Brafman, David
- Creators: Ebrahimkhani, Mohammad
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
Description
Alzheimer’s Disease (AD) affects over 5 million individuals in the U.S. and has a direct cost estimated in excess of $200 billion per year. Broadly speaking, there are two forms of AD—early-onset, familial AD (FAD) and late-onset-sporadic AD (SAD). Animal models of AD, which rely on the overexpression of FAD-related mutations, have provided important insights into the disease. However, these models do not display important disease-related pathologies and have been limited in their ability to model the complex genetics associated with SAD.
Advances in cellular reprogramming, have enabled the generation of in vitro disease models that can be used to dissect disease mechanisms and evaluate potential therapeutics. To that end, efforts by many groups, including the Brafman laboratory, to generated patient-specific hiPSCs have demonstrated the promise of studying AD in a simplified and accessible system. However, neurons generated from these hiPSCs have shown some, but not all, of the early molecular and cellular hallmarks associated with the disease. Additionally, phenotypes and pathological hallmarks associated with later stages of the human disease have not been observed with current hiPSC-based systems. Further, disease relevant phenotypes in neurons generated from SAD hiPSCs have been highly variable or largely absent. Finally, the reprogramming process erases phenotypes associated with cellular aging and, as a result, iPSC-derived neurons more closely resemble fetal brain rather than adult brain.
It is well-established that in vivo cells reside within a complex 3-D microenvironment that plays a significant role in regulating cell behavior. Signaling and other cellular functions, such as gene expression and differentiation potential, differ in 3-D cultures compared with 2-D substrates. Nonetheless, previous studies using AD hiPSCs have relied on 2-D neuronal culture models that do not reflect the 3-D complexity of native brain tissue, and therefore, are unable to replicate all aspects of AD pathogenesis. Further, the reprogramming process erases cellular aging phenotypes. To address these limitations, this project aimed to develop bioengineering methods for the generation of 3-D organoid-based cultures that mimic in vivo cortical tissue, and to generate an inducible gene repression system to recapitulate cellular aging hallmarks.
Advances in cellular reprogramming, have enabled the generation of in vitro disease models that can be used to dissect disease mechanisms and evaluate potential therapeutics. To that end, efforts by many groups, including the Brafman laboratory, to generated patient-specific hiPSCs have demonstrated the promise of studying AD in a simplified and accessible system. However, neurons generated from these hiPSCs have shown some, but not all, of the early molecular and cellular hallmarks associated with the disease. Additionally, phenotypes and pathological hallmarks associated with later stages of the human disease have not been observed with current hiPSC-based systems. Further, disease relevant phenotypes in neurons generated from SAD hiPSCs have been highly variable or largely absent. Finally, the reprogramming process erases phenotypes associated with cellular aging and, as a result, iPSC-derived neurons more closely resemble fetal brain rather than adult brain.
It is well-established that in vivo cells reside within a complex 3-D microenvironment that plays a significant role in regulating cell behavior. Signaling and other cellular functions, such as gene expression and differentiation potential, differ in 3-D cultures compared with 2-D substrates. Nonetheless, previous studies using AD hiPSCs have relied on 2-D neuronal culture models that do not reflect the 3-D complexity of native brain tissue, and therefore, are unable to replicate all aspects of AD pathogenesis. Further, the reprogramming process erases cellular aging phenotypes. To address these limitations, this project aimed to develop bioengineering methods for the generation of 3-D organoid-based cultures that mimic in vivo cortical tissue, and to generate an inducible gene repression system to recapitulate cellular aging hallmarks.
ContributorsBounds, Lexi Rose (Author) / Brafman, David (Thesis director) / Wang, Xiao (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
This thesis explores and analyzes the emergence of for-profit stem cell clinics in the United States, specifically in the Phoenix metropolitan area. Stem cell therapy is an emerging field that has great potential in preventing or treating a number of diseases. Certain companies are currently researching the application of stem cells as therapeutics. At present the FDA has only approved one stem cell-based product; however, there are a number of companies currently offering stem cell therapies. In the past five years, most news articles discussing these companies offering stem cell treatments talk of clinics in other countries. Recently, there seems to be a number of stem cell clinics appearing in the United States. Using a web search engine, fourteen stem cell clinics were identified and analyzed in the Phoenix metropolitan area. Each clinic was analyzed by their four key characteristics: business operations, stem cell types, stem cell isolation methods, and their position with the FDA. Based off my analysis, most of the identified clinics are located in Scottsdale or Phoenix. Some of these clinics even share the same location as another medical practice. Each of the fourteen clinics treat more than one type of health condition. The stem clinics make use of four stem cell types and three different isolation methods to obtain the stem cells. The doctors running these clinics almost always treat health conditions outside of their expertise. Some of these clinics even claim they are not subject to FDA regulation.
ContributorsAmrelia, Divya Vikas (Author) / Brafman, David (Thesis director) / Frow, Emma (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Currently in synthetic biology only the Las, Lux, and Rhl quorum sensing pathways have been adapted for broad engineering use. Quorum sensing allows a means of cell to cell communication in which a designated sender cell produces quorum sensing molecules that modify gene expression of a designated receiver cell. While useful, these three quorum sensing pathways exhibit a nontrivial level of crosstalk, hindering robust engineering and leading to unexpected effects in a given design. To address the lack of orthogonality among these three quorum sensing pathways, previous scientists have attempted to perform directed evolution on components of the quorum sensing pathway. While a powerful tool, directed evolution is limited by the subspace that is defined by the protein. For this reason, we take an evolutionary biology approach to identify new orthogonal quorum sensing networks and test these networks for cross-talk with currently-used networks. By charting characteristics of acyl homoserine lactone (AHL) molecules used across quorum sensing pathways in nature, we have identified favorable candidate pathways likely to display orthogonality. These include Aub, Bja, Bra, Cer, Esa, Las, Lux, Rhl, Rpa, and Sin, which we have begun constructing and testing. Our synthetic circuits express GFP in response to a quorum sensing molecule, allowing quantitative measurement of orthogonality between pairs. By determining orthogonal quorum sensing pairs, we hope to identify and adapt novel quorum sensing pathways for robust use in higher-order genetic circuits.
ContributorsMuller, Ryan (Author) / Haynes, Karmella (Thesis director) / Wang, Xiao (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Department of Chemistry and Biochemistry (Contributor) / School of Life Sciences (Contributor)
Created2015-05
Description
the project led by Professor Emma Frow, researching of stem cell clinics focused on stem cell applications, adherence to FDA guidelines, and characterization of information available and physician credentials. Regenerative medicine clinics commonly offered stem cell therapy, but introduced platelet rich plasma (PRP) and prolotherapy as regenerative therapies.
PRP and Prolotherapy are individual treatments that were even suggested and used in combination with stem cell therapies. Prolotherapy predates PRP as a chemical irritant therapy originally used to sclerose tissues. Prolotherapy is meant to stimulate platelet derived growth factors release to improve tissue healing response. Prolotherapy shows negligible efficacy improvements over corticosteroids, but may have underlying side effects from being an irritant. PRP is a more modern therapy for improved healing. Speculations state initial use was in an open heart surgery to improve healing post-surgery. PRP is created via centrifugation of patient blood to isolate growth factors by removing serum and other biological components to increase platelet concentration. PRP is comparable to corticosteroid injections in efficacy, but as an autologous application, there are no side effects making it more advantageous. Growth factors induce healing response and reduce inflammation. Growth factors stimulate cell growth, proliferation, differentiation, and stimulate cellular response mechanism such as angiogenesis and mitogenesis. The growth factor stimulation of PRP and prolotherapy both assist stem cell proliferation. Additional research is needed to determine differential capacity to ensure multipotent stem cells regenerate the correct cell type from the increased differential capacity offered by growth factor recruitment. The application of combination therapy for stem cells is unsubstantiated and applications violate FDA ‘minimal manipulation’ guidelines.
PRP and Prolotherapy are individual treatments that were even suggested and used in combination with stem cell therapies. Prolotherapy predates PRP as a chemical irritant therapy originally used to sclerose tissues. Prolotherapy is meant to stimulate platelet derived growth factors release to improve tissue healing response. Prolotherapy shows negligible efficacy improvements over corticosteroids, but may have underlying side effects from being an irritant. PRP is a more modern therapy for improved healing. Speculations state initial use was in an open heart surgery to improve healing post-surgery. PRP is created via centrifugation of patient blood to isolate growth factors by removing serum and other biological components to increase platelet concentration. PRP is comparable to corticosteroid injections in efficacy, but as an autologous application, there are no side effects making it more advantageous. Growth factors induce healing response and reduce inflammation. Growth factors stimulate cell growth, proliferation, differentiation, and stimulate cellular response mechanism such as angiogenesis and mitogenesis. The growth factor stimulation of PRP and prolotherapy both assist stem cell proliferation. Additional research is needed to determine differential capacity to ensure multipotent stem cells regenerate the correct cell type from the increased differential capacity offered by growth factor recruitment. The application of combination therapy for stem cells is unsubstantiated and applications violate FDA ‘minimal manipulation’ guidelines.
ContributorsKrum, Logan (Author) / Frow, Emma (Thesis director) / Brafman, David (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Genetic manipulation of human cell lines has widespread applications in biomedical research ranging from disease modeling to therapeutic development. Human cells are generally difficult to genetically engineer, but exogenous nucleic acids can be expressed by viral, chemical, or nonchemical means. Chemical transfections are simpler in practice than both viral and nonchemical delivery of genetic material, but often suffer from cytotoxicity and low efficiency. Novel aminoglycoside antibiotic-derived lipopolymers have been synthesized to mediate transgene delivery to human cells. These polymers are comprised of either paromomycin or apramycin crosslinked with glycerol diglycidylether and derivatized with stearoyl chloride in varying molar ratios. In this work, three previously identified target lipopolymers were screened against a library of human embryonic and induced pluripotent stem cell lines. Cells were transfected with a plasmid encoding green fluorescent protein (GFP) and expression was quantified with flow cytometry 48 hours after transfection. Transfection efficiency was evaluated between three distinct lipopolymers and four lipopolymer:DNA mass ratios. GFP expression was compared to that of cells transfected with commercially available chemical gene delivery reagent controls\u2014JetPEI, Lipofectamine, and Fugene\u2014at their recommended reagent:DNA ratios. Improved transgene expression in stem cell lines allows for improved research methods. Human stem cell-derived neurons that have been genetically manipulated to express phenotypic characteristics of aging can be utilized to model neurodegenerative diseases, elucidating information about these diseases that would be inaccessible in unmanipulated tissue.
ContributorsMehta, Frea (Author) / Brafman, David (Thesis director) / Rege, Kaushal (Committee member) / Chemical Engineering Program (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Cholangiocytes, the epithelial cells of the bile duct, are the origin of cholangiopathies which often necessitate liver transplants. Current progress in generating functional biliary organoids show potential for modelling cholangiopathies and validating therapeutic drugs. Organoids by groups Ogawa et al. and Sampaziotis et al. utilize soluble molecule induction, OP9 co-culture, and three-dimensional culture to achieve self-organizing tissues which express mature cholangiocyte markers and show cholangiocyte functionality. This thesis describes our efforts to establish a standard for functional PSC-derived bile duct tissues. By directing cell fate and patterning through external cues alone, we were able to produce CK19+ALB+ hepatoblast-like cells. These soluble molecule-induced cells also expressed EpCAM and CEBPA, suggesting the presence of early liver epithelial cells. However, inconsistent results and high levels of cell death with soluble molecule induction in early stages of differentiation prompted the development of a combinatory differentiation method which utilized multiple differentiation tools. We opted to combine transcription-factor triggered differentiation with soluble molecule-mediated differentiation to produce early biliary cells with the potential to develop into mature cholangiocytes. By combining genetic engineering through the activation of doxycycline-inducible GATA6 switch and microbead-mediated CXCR4 separation, we generated patterned tissues which expressed early biliary markers, CD146, CK19, and SOX9. In the future, three-dimensional cell culture and OP9 co-culture could improve our current results by facilitating 3D cellular self-organization and promoting NOTCH signaling for cholangiocyte maturation. Next steps for this research include optimizing media formulations, tracking gene expression over time, and testing the functionality of generated tissues.
ContributorsGo, Suyen Chantal (Author) / Ebrahimkhani, Mohammad (Thesis director) / Kiani, Samira (Committee member) / Harrington Bioengineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Current research into live-cell dynamics, particularly those relating to chromatin structure and remodeling, are limited. The tools that are used to detect state changes in chromatin, such as Chromatin Immunoprecipitation and qPCR, require that the cell be killed off. This limits the ability of researchers to pinpoint changes in live cells over a longer period of time. As such, there is a need for a live-cell sensor that can detect chromatin state changes. The Chromometer is a transgenic chromatin state sensor designed to better understand human cell fate and the chromatin changes that occur. HOXD11.12, a DNA sequence that attracts repressive Polycomb group (PCG) proteins, was placed upstream of a core promoter-driven fluorescent reporter (AmCyan fluorescent protein, CFP) to link chromatin repression to a CFP signal. The transgene was stably inserted at an ectopic site in U2-OS (osteosarcoma) cells. Expression of CFP should reflect the epigenetic state at the HOXD locus, where several genes are regulated by Polycomb to control cell differentiation. U2-OS cells were transfected with the transgene and grown under selective pressure. Twelve colonies were identified as having integrated parts from the transgene into their genomes. PCR testing verified 2 cell lines that contain the complete transgene. Flow cytometry indicated mono-modal and bimodal populations in all transgenic cell colonies. Further research must be done to determine the effectiveness of this device as a sensor for live cell state change detection.
ContributorsBarclay, David (Co-author) / Simper, Jan (Co-author) / Haynes, Karmella (Thesis director) / Brafman, David (Committee member) / School of Life Sciences (Contributor) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Pinpoint control over endogenous gene expression in vivo has long been a fevered dream for clinicians and researchers alike. With the recent repurposing of programmable, RNA-guided DNA endonucleases from the CRISPR bacterial immune system, this dream is becoming a powerful reality. Engineered CRISPR based transcriptional regulators have enabled researchers to perturb endogenous gene expression in vivo, allowing for the therapeutic reprogramming of cell and tissue behavior. However, for this technology to be of maximal use, a variety of technological hurdles still need to be addressed. Here, we discuss recent advances and integrative strategies that can help pave the way towards a new class of transcriptional therapeutics.
ContributorsPandelakis, Matthew (Author) / Ebrahimkhani, Mohammad (Thesis director) / Kiani, Samira (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Cell fate is a complex and dynamic process with many genetic components. It has often been likened to “multistable” mathematical systems because of the numerous possible “stable” states, or cell types, that cells may end up in. Due to its complexity, understanding the process of cell fate and differentiation has proven challenging. A better understanding of cell differentiation has applications in regenerative stem cell therapies, disease pathologies, and gene regulatory networks.
A variety of different genes have been associated with cell fate. For example, the Nanog/Oct-4/Sox2 network forms the core interaction of a gene network that maintains stem cell pluripotency, and Oct-4 and Sox2 also play a role in the tissue types that stem cells eventually differentiate into. Using the CRISPR/cas9 based homology independent targeted integration (HITI) method developed by Suzuki et al., we can integrate fluorescent tags behind genes with reasonable efficiency via the non-homologous end joining (NHEJ) DNA repair pathway. With human embryonic kidney (HEK) 293T cells, which can be transfected with high efficiencies, we aim to create a three-parameter reporter cell line with fluorescent tags for three different genes related to cell fate. This cell line would provide several advantages for the study of cell fate, including the ability to quantitatively measure cell state, observe expression heterogeneity among a population of genetically identical cells, and easily monitor fluctuations in expression patterns.
The project is partially complete at this time. This report discusses progress thus far, as well as the challenges faced and the future steps for completing the reporter line.
A variety of different genes have been associated with cell fate. For example, the Nanog/Oct-4/Sox2 network forms the core interaction of a gene network that maintains stem cell pluripotency, and Oct-4 and Sox2 also play a role in the tissue types that stem cells eventually differentiate into. Using the CRISPR/cas9 based homology independent targeted integration (HITI) method developed by Suzuki et al., we can integrate fluorescent tags behind genes with reasonable efficiency via the non-homologous end joining (NHEJ) DNA repair pathway. With human embryonic kidney (HEK) 293T cells, which can be transfected with high efficiencies, we aim to create a three-parameter reporter cell line with fluorescent tags for three different genes related to cell fate. This cell line would provide several advantages for the study of cell fate, including the ability to quantitatively measure cell state, observe expression heterogeneity among a population of genetically identical cells, and easily monitor fluctuations in expression patterns.
The project is partially complete at this time. This report discusses progress thus far, as well as the challenges faced and the future steps for completing the reporter line.
ContributorsLoveday, Tristan Andre (Author) / Wang, Xiao (Thesis director) / Brafman, David (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05