Clarifying the Role of the Extracellular Matrix (ECM)

The ECM is comprised of molecules that surround adipocytes and regulate cell metabolism. Our lab has demonstrated that the adipose tissue ECM is altered in diabetes, and that the ECM contributes to adipocyte metabolic dysfunction. Our work continues to elucidate the mechanisms of ECM-adipocyte crosstalk and to develop methods to manipulate the ECM to improve adipocyte and systemic metabolism.

Bioengineering Artificial Matrices as a Therapeutic Vehicle in Diabetes

In collaboration with bioengineers, we are developing artificial matrices (bioscaffolds, hydrogels), in which we culture adipocytes. By manipulating the mechanical properties of these matrices, we can engineer healthier adipocytes that can be transplanted into mice with diabetes and obesity in an effort to cure these diseases.

Defining Preadipocyte Subpopulations Within Human Adipose Tissue

In addition to studying matrix–adipocyte interactions, we investigate the mechanisms by which the ECM interacts with adipose tissue stem cells, using single cell RNA sequencing to define preadipocyte and macrophage subpopulations within human adipose tissue in diabetes. Our objective is to understand metabolically beneficial and detrimental adipose tissue stem cells and macrophages in human adipose tissue. We are developing novel methods to isolate, extract and manipulate these cells in vitro to understand how they function–and how we can make them healthier.

Investigating Additional Cell–Cell and Cell–Matrix Interactions

Our laboratory conducts research into other cell types, including macrophages, several types of immune cells, adipocyte stem cells, and endothelial cells. We also utilize proteomics to study the composition of ECM in healthy and diseased adipose tissue. The aim of this work is to better understand how these cell types communicate with adipocytes and the extracellular matrix so that we can identify regulating mechanisms and engineer healthier adipose tissue.

Adipocyte-Cancer Crosstalk

Our lab has demonstrated that dysfunctional adipocytes and adipose tissue contribute to the development and growth of pancreatic cancer. We are studying crosstalk between pancreatic cancer cells and adipocytes in in vitro murine pancreatic cancer models with cancer researchers at U-M.

The O'Rourke Laboratory has advanced the understanding of adipose tissue biology and dysfunction and its role in metabolic disease and, more recently, cancer in many ways. Some our findings include:

• Implication of the ECM in adipose tissue dysfunction in the context of diabetes. Our work found that in tissue in 3D culture from patients without diabetes, the ECM prevents metabolic dysfunction with respect to glucose metabolism in adipocytes, while the ECM in tissue from patients with disease negatively impacts glucose metabolism. Our findings demonstrate that the ECM is a promising means to influence adipose tissue metabolism.
• Further work investigating ECM–cellular interactions in our 3D culture systems has implicated advanced glycation end products and Rho signaling as key players in regulating ECM–adipocyte metabolic crosstalk.
• Our research on the role of inflammation and fibrosis in adipose tissue has homed in on cell stress and hypoxia as triggers of inflammatory processes. More specifically, we have pinpointed p38 mitogen-activated protein kinase as an important regulator in hypoxia in adipose tissue.
• Our group was the first to report and define the role of the human adipose tissue natural killer (NK) cell phenotype, with upregulated NKG2D in the context of diabetes and obesity in a mouse model as well as in human tissue. We were the first to demonstrate, using a transgenic mouse model, that ablating the NK cells improved systemic insulin resistance, suggesting that NK cells might serve as a potential therapeutic target.
• In recent, collaborative work on pancreatic cancer cell–adipocyte crosstalk, we have found that adipocytes support the growth and spread of cancer cells. Additionally, we have identified glutamine as a potentially important mediator in these processes.

Our findings have the potential to advance how we treat obesity, diabetes and cancer, leading us toward truly personalized treatment approaches. Our overarching goal is to generate novel cell-based therapies, using autologous adipose stem cells and adipocytes delivered in engineered artificial matrices, for diabetes and other metabolic diseases.

We work closely with many basic scientists, surgeon-scientists and bioengineers. Current collaborations include investigations with:

• Carey Lumeng, MD, PhD, in the Department of Pediatrics and Communicable Diseases, University of Michigan, on adipose tissue biology.
• Andy Putnam, PhD, in the Department of Biomedical Engineering and Cardiovascular Medicine, University of Michigan, on matrix–adipocyte crosstalk with an emphasis on characterizing the mechanical properties of tissue.
• Claudia Loebel, PhD, in the Department of Materials Science and Engineering, University of Michigan, on the role of ECM in regulating protein synthesis in adipose tissue stem cells.
• Nadejda Bozadjieva-Kramer PhD, in the Department of Surgery, University of Michigan, on mechanisms of weight loss after bariatric surgery. 
• Tim Frankel, MD, in the Department of Surgery, University of Michigan, on adipocyte–pancreatic cancer crosstalk. 

We continue to explore the interactions between adipocytes and other cell types within adipose tissue and their role in regulating cellular function. In particular, we are interested in endothelial cells that give rise to blood vessel growth in adipose tissue. Evidence suggests these processes are also impaired in diabetes.

We are expanding our bioengineered matrices work to gain a greater understanding of the role of mechanical factors in addition to molecular interactions. Our observations to date suggest that mechanical properties of these matrices may have detrimental effects on adipocyte metabolism.