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Description
The pathophysiology of neurodegenerative diseases, such as Alzheimer’s disease (AD), remain difficult to ascertain in part because animal models fail to fully recapitulate the complex pathophysiology of these diseases. In vitro models of neurodegenerative diseases generated with patient derived human induced pluripotent stem cells (hiPSCs) and human embryonic stem cells (hESCs) could provide new insight into disease mechanisms. Although protocols to differentiate hiPSCs and hESCs to neurons have been established, standard practice relies on two dimensional (2D) cell culture systems, which do not accurately mimic the complexity and architecture of the in vivo brain microenvironment.
I have developed protocols to generate 3D cultures of neurons from hiPSCs and hESCs, to provide more accurate models of AD. In the first protocol, hiPSC-derived neural progenitor cells (hNPCs) are plated in a suspension of Matrigel™ prior to terminal differentiation of neurons. In the second protocol, hiPSCs are forced into aggregates called embryoid bodies (EBs) in suspension culture and subsequently directed to the neural lineage through dual SMAD inhibition. Culture conditions are then changed to expand putative hNPC populations and finally differentiated to neuronal spheroids through activation of the tyrosine kinase pathway. The gene expression profiles of the 3D hiPSC-derived neural cultures were compared to fetal brain RNA. Our analysis has revealed that 3D neuronal cultures express high levels of mature pan-neuronal markers (e.g. MAP2, β3T) and neural transmitter subtype specific markers. The 3D neuronal spheroids also showed signs of neural patterning, similar to that observed during embryonic development. These 3D culture systems should provide a platform to probe disease mechanisms of AD and enable to generation of more advanced therapeutics.
I have developed protocols to generate 3D cultures of neurons from hiPSCs and hESCs, to provide more accurate models of AD. In the first protocol, hiPSC-derived neural progenitor cells (hNPCs) are plated in a suspension of Matrigel™ prior to terminal differentiation of neurons. In the second protocol, hiPSCs are forced into aggregates called embryoid bodies (EBs) in suspension culture and subsequently directed to the neural lineage through dual SMAD inhibition. Culture conditions are then changed to expand putative hNPC populations and finally differentiated to neuronal spheroids through activation of the tyrosine kinase pathway. The gene expression profiles of the 3D hiPSC-derived neural cultures were compared to fetal brain RNA. Our analysis has revealed that 3D neuronal cultures express high levels of mature pan-neuronal markers (e.g. MAP2, β3T) and neural transmitter subtype specific markers. The 3D neuronal spheroids also showed signs of neural patterning, similar to that observed during embryonic development. These 3D culture systems should provide a platform to probe disease mechanisms of AD and enable to generation of more advanced therapeutics.
ContributorsPetty, Francis (Author) / Brafman, David (Thesis advisor) / Stabenfeldt, Sarah (Committee member) / Nikkhah, Mehdi (Committee member) / Arizona State University (Publisher)
Created2016
Description
Background: College freshmen are exposed to a variety of environmental and social factors that can alter changes to health habits and encourage weight gain. Weight-related conversations had with friends may be related to self-perception of weight and alterations to health behaviors, but this association has yet to be assessed in the college population.
Objective: This study aims to examine the relationship between friend advice about weight management, self-perception of weight, and alterations to weight change intentions, physical activity, and eating habits in college freshmen over time.
Methods: College freshmen from ASU with complete data for three time points (n=321) were found to be predominantly female (72.2%) and non-white (53.2%) with a mean age of 17.5±41. Complete data included responses for items included in analysis which were related to friend encouragement about weigh management, self-perception of weight, physical activity, eating behaviors, and weight change intentions. A longitudinal multivariate mediation analysis using negative binomial regression adjusted for sociodemographics and clustering by dorm was used to assess the relationship between 1) friend encouragement about weight management at time 1 and behavioral outcomes at time 3, 2) friend encouragement about weight management at time 1 and self-perception of weight at time 2, and 3) self-perception of weight at time 2 and behavioral outcomes at time 3.
Results: A small proportion of population perceived friend encouragement about weight loss (18.3%) and weight gain (14.4%) at time 1. Half the population (50.9%) had the self-perception of overweight at time 2. At time 3, more than half (54.3%) of individuals performed at least 60 minutes of MVPA and consumed at least ½ a serving of sugar-sweetened beverages each day, while nearly half (48.6%) consumed at least 2 servings of fruits and vegetables each day. Males perceived more friend encouragement to gain weight (27.4%; p<0.01), but more females had the self-perception of overweight (54%; p=0.04) and were attempting to lose weight (59.3%; p<0.01). Individuals who perceived friend encouragement to lose weight at time 1 had a 14.8% greater prevalence (p<0.001) of overweight perception of time two, and a 9.6% and 6.9%; decreased prevalence (p<0.001) of weight change and weight loss intentions (p=0.023) at time three respectively. Individuals who perceived friend encouragement to gain weight had a 34.9% decreased prevalence of (p<0.001) of self-perception of overweight at time 1. In individuals with the self-perception of overweight at time 2, there was a 18.1% increased prevalence (p<0.001) of consuming at least ½ a serving of sugar-sweetened beverages/day and an increased prevalence of 22.8% and 24.0% for weight change intentions and weight loss intentions at time 3 (p<0.001).
Conclusion: These findings suggest that there was not a mediation effect of self-perception of overweight in the relationship between friend encouragement about weight management and behavioral outcomes in the current sample. However, the increased prevalence of overweight perception in individuals who perceived friend encouragement about weight management may inform future interventions to focus on how weight-related conversations with friends is related to overweight perception. More research about the relationship between weight-related conversations had with friends, self-perception of weight, and health behaviors is needed to confirm these findings.
Objective: This study aims to examine the relationship between friend advice about weight management, self-perception of weight, and alterations to weight change intentions, physical activity, and eating habits in college freshmen over time.
Methods: College freshmen from ASU with complete data for three time points (n=321) were found to be predominantly female (72.2%) and non-white (53.2%) with a mean age of 17.5±41. Complete data included responses for items included in analysis which were related to friend encouragement about weigh management, self-perception of weight, physical activity, eating behaviors, and weight change intentions. A longitudinal multivariate mediation analysis using negative binomial regression adjusted for sociodemographics and clustering by dorm was used to assess the relationship between 1) friend encouragement about weight management at time 1 and behavioral outcomes at time 3, 2) friend encouragement about weight management at time 1 and self-perception of weight at time 2, and 3) self-perception of weight at time 2 and behavioral outcomes at time 3.
Results: A small proportion of population perceived friend encouragement about weight loss (18.3%) and weight gain (14.4%) at time 1. Half the population (50.9%) had the self-perception of overweight at time 2. At time 3, more than half (54.3%) of individuals performed at least 60 minutes of MVPA and consumed at least ½ a serving of sugar-sweetened beverages each day, while nearly half (48.6%) consumed at least 2 servings of fruits and vegetables each day. Males perceived more friend encouragement to gain weight (27.4%; p<0.01), but more females had the self-perception of overweight (54%; p=0.04) and were attempting to lose weight (59.3%; p<0.01). Individuals who perceived friend encouragement to lose weight at time 1 had a 14.8% greater prevalence (p<0.001) of overweight perception of time two, and a 9.6% and 6.9%; decreased prevalence (p<0.001) of weight change and weight loss intentions (p=0.023) at time three respectively. Individuals who perceived friend encouragement to gain weight had a 34.9% decreased prevalence of (p<0.001) of self-perception of overweight at time 1. In individuals with the self-perception of overweight at time 2, there was a 18.1% increased prevalence (p<0.001) of consuming at least ½ a serving of sugar-sweetened beverages/day and an increased prevalence of 22.8% and 24.0% for weight change intentions and weight loss intentions at time 3 (p<0.001).
Conclusion: These findings suggest that there was not a mediation effect of self-perception of overweight in the relationship between friend encouragement about weight management and behavioral outcomes in the current sample. However, the increased prevalence of overweight perception in individuals who perceived friend encouragement about weight management may inform future interventions to focus on how weight-related conversations with friends is related to overweight perception. More research about the relationship between weight-related conversations had with friends, self-perception of weight, and health behaviors is needed to confirm these findings.
ContributorsThibodeau, Tristan (Author) / Bruening, Meg (Thesis advisor) / Ohri-Vachaspati, Punam (Committee member) / Huberty, Jennifer (Committee member) / Arizona State University (Publisher)
Created2016
Description
Synthetic biology is a novel method that reengineers functional parts of natural genes of interest to build new biomolecular devices able to express as designed. There is increasing interest in synthetic biology due to wide potential applications in various fields such as clinics and fuel production. However, there are still many challenges in synthetic biology. For example, many natural biological processes are poorly understood, and these could be more thoroughly studied through model synthetic gene networks. Additionally, since synthetic biology applications may have numerous design constraints, more inducer systems should be developed to satisfy different requirements for genetic design.
This thesis covers two topics. First, I attempt to generate stochastic resonance (SR) in a biological system. Synthetic bistable systems were chosen because the inducer range in which they exhibit bistability can satisfy one of the three requirements of SR: a weak periodic force is unable to make the transition between states happen. I synthesized several different bistable systems, including toggle switches and self-activators, to select systems matching another requirement: the system has a clear threshold between the two energy states. Their bistability was verified and characterized. At the same time, I attempted to figure out the third requirement for SR – an effective noise serving as the stochastic force – through one of the most widespread toggles, the mutual inhibition toggle, in both yeast and E. coli. A mathematic model for SR was written and adjusted.
Secondly, I began work on designing a new genetic system capable of responding to pulsed magnetic fields. The operators responding to pulsed magnetic stimuli in the rpoH promoter were extracted and reorganized. Different versions of the rpoH promoter were generated and tested, and their varying responsiveness to magnetic fields was recorded. In order to improve efficiency and produce better operators, a directed evolution method was applied with the help of a CRISPR-dCas9 nicking system. The best performing promoters thus far show a five-fold difference in gene expression between trials with and without the magnetic field.
This thesis covers two topics. First, I attempt to generate stochastic resonance (SR) in a biological system. Synthetic bistable systems were chosen because the inducer range in which they exhibit bistability can satisfy one of the three requirements of SR: a weak periodic force is unable to make the transition between states happen. I synthesized several different bistable systems, including toggle switches and self-activators, to select systems matching another requirement: the system has a clear threshold between the two energy states. Their bistability was verified and characterized. At the same time, I attempted to figure out the third requirement for SR – an effective noise serving as the stochastic force – through one of the most widespread toggles, the mutual inhibition toggle, in both yeast and E. coli. A mathematic model for SR was written and adjusted.
Secondly, I began work on designing a new genetic system capable of responding to pulsed magnetic fields. The operators responding to pulsed magnetic stimuli in the rpoH promoter were extracted and reorganized. Different versions of the rpoH promoter were generated and tested, and their varying responsiveness to magnetic fields was recorded. In order to improve efficiency and produce better operators, a directed evolution method was applied with the help of a CRISPR-dCas9 nicking system. The best performing promoters thus far show a five-fold difference in gene expression between trials with and without the magnetic field.
ContributorsHu, Hao (Author) / Wang, Xiao (Thesis advisor) / Stabenfeldt, Sarah (Committee member) / Brafman, David (Committee member) / Arizona State University (Publisher)
Created2016
Description
The production, characterization, and antioxidant capacity of the carotenoid fucoxanthin from the marine diatom Odontella aurita were investigated. The results showed that low light and nitrogen-replete culture medium enhanced the biosynthesis of fucoxanthin. The maximum biomass concentration of 6.36 g L-1 and maximum fucoxanthin concentration of 18.47 mg g-1 were obtained in cultures grown in a bubble column photobioreactor (Ø 3.0 cm inner diameter), resulting in a fucoxanthin volumetric productivity of 7.96 mg L-1 day-1. A slight reduction in biomass production was observed in the scaling up of O. aurita culture in a flat plate photobioreactor, yet yielded a comparable fucoxanthin volumetric productivity. A rapid method was developed for extraction and purification of fucoxanthin. The purified fucoxanthin was identified as all-trans-fucoxanthin, which exhibited strong antioxidant properties, with the effective concentration for 50% scavenging (EC50) of 1,1-dihpenyl-2-picrylhydrazyl (DPPH) radical and 2,2′-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) radical being 0.14 and 0.03 mg mL-1, respectively. Our results suggested that O. aurita can be a natural source of fucoxanthin for human health and nutrition.
ContributorsXia, Song (Author) / Wang, Ke (Author) / Wan, Linglin (Author) / Li, Aifen (Author) / Hu, Qiang (Author) / Zhang, Chengwu (Author) / Julie Ann Wrigley Global Institute of Sustainability (Contributor)
Created2013-07-23
Description
In the decade since Yamanaka and colleagues described methods to reprogram somatic cells into a pluripotent state, human induced pluripotent stem cells (hiPSCs) have demonstrated tremendous promise in numerous disease modeling, drug discovery, and regenerative medicine applications. More recently, the development and refinement of advanced gene transduction and editing technologies have further accelerated the potential of hiPSCs. In this review, we discuss the various gene editing technologies that are being implemented with hiPSCs. Specifically, we describe the emergence of technologies including zinc-finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 that can be used to edit the genome at precise locations, and discuss the strengths and weaknesses of each of these technologies. In addition, we present the current applications of these technologies in elucidating the mechanisms of human development and disease, developing novel and effective therapeutic molecules, and engineering cell-based therapies. Finally, we discuss the emerging technological advances in targeted gene editing methods.
ContributorsBrookhouser, Nicholas (Author) / Raman, Sreedevi (Author) / Potts, Chris (Author) / Brafman, David (Author) / Ira A. Fulton Schools of Engineering (Contributor)
Created2017-02-06
Description
Traumatic brain injury (TBI) may result in numerous pathologies that cannot currently be mitigated by clinical interventions. Stem cell therapies are widely researched to address TBI-related pathologies with limited success in pre-clinical models due to limitations in transplant survival rates. To address this issue, the use of tissue engineered scaffolds as a delivery mechanism has been explored to improve survival and engraftment rates. Previous work with hyaluronic acid \u2014 laminin (HA-Lm) gels found high viability and engraftment rates of mouse fetal derived neural progenitor/stem cells (NPSCs) cultured on the gel. Furthermore, NPSCs exposed to the HA-Lm gels exhibit increased expression of CXCR4, a critical surface receptor that promotes cell migration. We hypothesized that culturing hNPCs on the HA-Lm gel would increase CXCR4 expression, and thus enhance their ability to migrate into sites of tissue damage. In order to test this hypothesis, we designed gel scaffolds with mechanical properties that were optimized to match that of the natural extracellular matrix. A live/dead assay showed that hNPCs preferred the gel with this optimized formulation, compared to a stiffer gel that was used in the CXCR4 expression experiment. We found that there may be increased CXCR4 expression of hNPCs plated on the HA-Lm gel after 24 hours, indicating that HA-Lm gels may provide a valuable scaffold to support viability and migration of hNPCs to the injury site. Future studies aimed at verifying increased CXCR4 expression of hNPCs cultured on HA-Lm gels are necessary to determine if HA-Lm gels can provide a beneficial scaffold for stem cell engraftment therapy for treating TBI.
ContributorsHemphill, Kathryn Elizabeth (Author) / Stabenfeldt, Sarah (Thesis director) / Brafman, David (Committee member) / Harrington Bioengineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Current culturing methods allow for human neural progenitor cells to be differentiated into neurons for use in diagnostic tools and disease modeling. An issue arises in the relatively low number of cells that can be successfully expanded and differentiated using these current methods, making the progress of research dependent on these cultures as a large number of cells are needed to conduct relevant assays. This project focuses on the expansion and differentiation of human neural progenitor cells cultured on microcarriers and within a rotating bioreactor system as a way to increase the total number of cells generated. Additionally, cryopreservation and the characteristics of these neurons post thaw is being investigated to create a way for long term storage, as well as, a method for standardizing cell lines between multiple experiments at different time points. The experiments covered in this study are aimed to compare the characteristics of differentiated human neurons, both demented and non-demented cell lines between pre-cryopreservation, freshly differentiated neurons and post-cryopreservation neurons. The assays conducted include immunofluorescence, calcium imaging, quantitative polymerase chain reaction, flow cytometry and ELISA data looking at Alzheimer’s disease traits. With the data collected within this study, the use of bioreactors, in addition to, cryopreservation of human neurons for long term storage can be better implemented into human neural progenitor cell research. Both of these aspects will increase the output of these cultures and potentially remove the bottleneck currently found within human neural disease modeling.
ContributorsHenson, Tanner Jay (Author) / Brafman, David (Thesis director) / Kodibagkar, Vikram (Committee member) / School of Life Sciences (Contributor) / Harrington Bioengineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Objectives: To explore the feasibility and effects of using a meditation mobile app 10-minutes a day for 4-weeks to reduce burnout (primary outcome), improve mindfulness, reduce stress, and depression in physician assistant (PA) students compared to a wait-list control.
Methods: This study was a randomized, wait-list, control trial with assessments at baseline and post-intervention (week 4). Participants were asked to meditate using Calm for 10 minutes per day. A p value ≤0.05 was considered statistically significant.
Results: The majority of participants (n=19) stated using Calm helped them cope with the stress of PA school. The intervention group participated in meditation for an average of 76 minutes/week. There were significant differences in all outcomes for the intervention group (all p ≤0.06). There was a significant interaction between group and time factors in emotional exhaustion (p=.016) and depersonalization (p=.025).
Conclusions: Calm is a feasible way to reduce burnout in PA students. Our findings provide information that can be applied to the design of future studies.
Methods: This study was a randomized, wait-list, control trial with assessments at baseline and post-intervention (week 4). Participants were asked to meditate using Calm for 10 minutes per day. A p value ≤0.05 was considered statistically significant.
Results: The majority of participants (n=19) stated using Calm helped them cope with the stress of PA school. The intervention group participated in meditation for an average of 76 minutes/week. There were significant differences in all outcomes for the intervention group (all p ≤0.06). There was a significant interaction between group and time factors in emotional exhaustion (p=.016) and depersonalization (p=.025).
Conclusions: Calm is a feasible way to reduce burnout in PA students. Our findings provide information that can be applied to the design of future studies.
ContributorsWorth, Taylor Nicole (Author) / Huberty, Jennifer (Thesis director) / Will, Kristen (Committee member) / Puzia, Megan (Committee member) / College of Health Solutions (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05