Dissertation
Advancing in vitro models of adipogenesis: from improved organoids to immune-interactive platforms for toxicology
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2025
DOI: 10.25820/etd.008242
Abstract
Polychlorinated Biphenyls (PCBs) are a group of environmental toxicants, that despite being banned since 1979, are still ubiquitous within buildings and the environment today. Their benefits of being chemically inert, with high thermal, electrical, and acidic resistance lead to heavy use within building materials such as transformers, capacitors, caulks, and paints for the sake of improving longevity. These pollutants have since been linked to many detrimental health defects such as cancers, cardiovascular diseases, neurodegeneration, and metabolic syndromes such as obesity and type II diabetes. Despite being linked to metabolic syndrome, more work needs to be done to better understand the mechanism of which exposure leads to this pathology. With adipose tissue not only being a major player in the development of metabolic syndrome risk factors such as obesity but being the main storage site for lipophilic compounds such as PCBs, it is at the forefront of research for PCB toxicology. Despite this knowledge, more work needs to be done to highlight how PCB exposure drives metabolic syndrome pathology, requiring a deeper look into how resident cells such as stem cells, macrophages, and mature adipocytes respond to such insult. The goal of this thesis is not only to further develop adipose tissue models to better understand how these cells interact with each other, regulating the complex processes such as inflammation and metabolism, but also to identify how these toxicants influence each cell type alone and in combination by utilizing such models.
Chapter 1 reviews our current understanding of PCBs at large, their significance within human health, focusing on metabolic syndrome (MetS), the current understanding of major contributing risk factors towards MetS in relation to adipose tissue health, and how to model this important organ. First, going into depth on PCB environmental loads presented through mismanaged manufacturing, the current routes of exposure our population is experiencing today, and the many negative health impacts that are currently associated with PCB exposure. One such concerning scenario is the exposure school-aged kids are experiencing through the volatilization of toxicants from PCB-laden products. A major source being the legacy PCB mixture – Aroclor 1254 along with non-legacy sources that occur as byproducts in current-day manufacturing practices. Despite being strongly linked with many pathologies, our gap in knowledge of how exposure drives metabolic syndrome is highlighted and put at the forefront of importance to pursue further. The chapter then pivots to review our current understanding of a major risk factor of metabolic syndrome, obesity. Obesity can be split into two clinical presentations: metabolically healthy and metabolically unhealthy. The scope of this section is honed in on metabolically unhealthy obesity, highlighting how various cells within adipose tissue such as progenitor cells, immune cells, and mature adipocytes respond within normal, healthy adipose tissue, and how their behavior transitions towards a more inflamed, unregulated state within hypertrophic obesity. Focus is then brought towards current in vitro models of adipose tissue, the most important of which is modeling adipogenesis – the differentiation of resident stem cells towards a mature adipocyte state that is heavily impacted within obesity. While there have been many advances within the field, much more work is required to not only further achieve physiological relevance, but also to better model changes occurring during obesity.
Chapter 2 investigates the impacts of three common PCB mixtures, specifically Aroclor 1016, Aroclor 1254 and cabinet mixture, on resident adipose-derived stem cells within a traditional monolayer system. These cells are in charge of maintaining a proliferative niche, undergoing adipogenic differentiation, and immunomodulation within adipose tissue. We found that physiologically relevant concentrations of these PCB mixtures have both cytostatic and cytotoxic effects on this cellular niche. Cytostatic concentrations are capable of impairing immunomodulatory capabilities and differentiation capacities of stem cells, leading to a dysfunctional cellular niche. This highlights how these mixtures are capable of driving metabolic syndrome through impacting the proliferative and differentiation capacities of the progenitor niche.
Chapter 3 focuses on improving cellular models of adipogenesis – the differentiation of resident stem cells to functional, mature adipocytes. Traditional monolayer cultures fall short in not only differentiation efficiency, but also with producing functional adipocytes in terms of adipokine signaling, inflammatory levels, and lipid production. A focus is then brought to a scaffold-free 3D, spheroid model of adipogenesis, providing an in depth methodology of how to reproduce this model, while highlighting its improvements in fostering increased differentiation capacity, better adipokine signaling, and decreased inflammatory production. This method is also utilized to highlight human donor variability, as all studies were performed on primary, human-derived adipose stem cells.
Chapter 4 then utilizes the methodology created from Chapter 3, while incorporating an immune cell component that plays a large role in instigating healthy adipogenesis – macrophages. Adipose tissue undergoes a large transition in inflammatory states between healthy and obese presentations. Specifically, a lower composition of anti-inflammatory macrophages are present within healthy tissue, while obese tissue incorporates a higher composition of more pro-inflammatory macrophages. These ratios and macrophage phenotypes are used as conditions to model how increases in inflammation impacts adipogenesis and ultimate adipocyte functionality within the context of obesity. With the knowledge that PCB exposure drives inflammatory phenotypes of both pro- and anti-inflammatory macrophages, these models are then put to the test toxicologically, as direct PCB exposure has minimal impacts on adipogenesis within the improved, organoid model. Upon incorporating PCB exposure on both the stem cell and macrophage components, the toxicological impacts of PCBs are elucidated, highlighting how the increase in inflammation from exposure drives adipose tissue dysfunction in both health and obese levels of inflammation.
Overall, this work furthers adipose tissue model development, while highlighting the toxicological impacts of PCBs on adipose-resident stem cells, modulated indirectly through macrophage exposure. With this knowledge, alongside all the other work within Superfund Programs will hopefully prove impactful in policy change to mitigate PCB exposure within the environment.
Details
- Title: Subtitle
- Advancing in vitro models of adipogenesis: from improved organoids to immune-interactive platforms for toxicology
- Creators
- Jesse Noah Liszewski
- Contributors
- James Ankrum (Advisor)Edward Sander (Committee Member)Aloysius Klingelhutz (Committee Member)Kristan Worthington (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Biomedical Engineering
- Date degree season
- Autumn 2025
- DOI
- 10.25820/etd.008242
- Publisher
- University of Iowa
- Number of pages
- xvi, 170 pages
- Copyright
- Copyright 2025 Jesse Liszewski
- Grant note
This study was supported by NIH P42 ES013661 (JAA, AJK, HJL) and a pilot grant from the Environmental Health Research Center P30 ES005605 (AJK, JAA). RB is supported by the University of Iowa MSTP Grant, NIH T32 GM139776. We also acknowledge the University of Iowa Tissue Procurement Core which manages the University of Iowa Biobank (UIBB IRB#201103721) for services provided related to acquisition of study specimens. The TPC is supported by an award from NIH (NCI award number P30CA086862) and the University of Iowa Carver College of Medicine.
This work was supported by NIGMS R01GM145626 (ES, JA), NIH P42 ES013661 (J.A. and A.K.), and a Diabetes Action Research and Education Grant (J.A.).
- Language
- English
- Date submitted
- 12/09/2025
- Description illustrations
- Illustrations, graphs, charts, tables
- Description bibliographic
- Includes bibliographical references (pages 161-166).
- Public Abstract (ETD)
Polychlorinated Biphenyls (PCBs) are a persistent organic pollutant and forever chemical that has become unavoidable with human exposure. While these toxicants have been associated with the development of metabolic syndrome such as obesity and type II diabetes, more work needs to be performed to understand how exposure drives these diseases. Adipose tissue is not only the main storage site of these toxicants but is the main tissue that experiences stark changes throughout the progression of obesity. The goal of my research is to build better cellular models of adipose tissue while using the given models to better understand how PCBs drive obesity. First, I studied how PCBs impact adipose stem cells, those in charge of maintaining a healthy environment within fat tissue and filling in the roles left behind of dysfunctional fat cells. I found that PCBs impair their ability to turn into functional fat cells. Second, I improved upon the cellular models used previously to study PCBs through culturing them in a 3-dimensional format, while highlighting how different cells can behave depending on the donor. Lastly, I further built upon the 3-dimensional model by including an immune cell component, specifically macrophages, which have large impacts on tissue health. I then used this final model to study PCB exposure, finding that these toxicants mainly drive adipose tissue dysfunction through increasing inflammation on the macrophage niche.
- Academic Unit
- Roy J. Carver Department of Biomedical Engineering
- Record Identifier
- 9985134948602771
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