Analyzing fibrin polymerization and crosslinking on macrophage function, obesity, and associated metabolic pathologies

Diet-induced obesity is characterized by a state of chronic inflammation and hypercoagulation, which increases the risk of cardiovascular disease, nonalcoholic fatty liver disease (NAFLD) and diabetes. Fibrin(ogen) is the primary structural component of blood clots, but previous studies identified extravascular fibrin(ogen) deposition in adipose tissue and liver of obese mice and human patients. These deposits colocalize with pro-inflammatory macrophages. Previous studies from our research team revealed that genetically modified Fibγ390-396A mice expressing a mutant form of fibrin(ogen) that lacks binding function for the αMβ2 leukocyte integrin receptor develop significantly reduced diet-induced obesity and associated pathologies. To address whether conversion of soluble fibrinogen to a crosslinked fibrin matrix is required to exacerbate metabolic disease, mice expressing fibrinogen that cannot be converted to fibrin (FibAEK) and mice deficient in the FXIII catalytic A subunit which prevents fibrin crosslinking (FXIII-) were challenged with high-fat diet. FibAEK mice were mildly protected from NAFLD and obesity, while FXIII- mice were only protected from NAFLD development. To begin to determine how different forms of fibrin(ogen) engage macrophages, immortalized human monocytes (THP-1 cells) were incubated with various molecular forms of fibrin(ogen). Gene expression and cell function were analyzed. THP-1 cells bound to wildtype (WT) fibrinogen more effectively than to fibrinogen γ390-396A. However, no differences in THP-1 binding were observed between monomeric fibrinogen and polymerized fibrin. Binding with any molecular forms of fibrin(ogen) did not induce the NF-κB pathway in macrophage-like murine cells (J774-Dual). Here, I have worked on the development of a preliminary in vitro platform for future studies to further elucidate the mechanisms by which fibrin(ogen) regulates macrophage effector function.Bachelor of Art