(P181) TARGETING CARDIAC FIBROSIS WITH METFORMIN IN PAI-1 DEFICIENCY: ADVANCING PERSONALIZED THERAPEUTICS

Background: Heart failure (HF) develops when pathological stresses chronically persist, often after a cardiovascular event. A lesser-known HF risk factor is a deficiency of a circulating protein called plasminogen activator inhibitor-1 (SERPINE-1/PAI-1). Specifically, individuals carrying a loss-of-function mutation in PAI-1 exhibit an increased cardiac fibrosis (CF) burden which can lead to HF. This observation is conserved in aged PAI-1 deficient mice with spontaneous CF, suggesting that effective prevention of the pro-fibrotic condition is required to minimize HF risk. Nevertheless, the mechanism underlying PAI-1 deficient mediated CF and its treatment options remain elusive.
Metformin has a strong safety record and is used primarily for its glucose-lowering efficacy. Importantly, metformin has a cardioprotective profile, improving cardiac dysfunction and reducing CF in pre-clinical HF models. Thus, we hypothesize that metformin treatment will improve cardiac function and reduce CF in PAI-1 deficient mice and that PAI-1 plays a critical role in modulating pathological cardiac fibrosis.

METHODS AND RESULTS: To investigate this, male and female PAI-1 deficient mice and littermate controls were treated with/without metformin (200 mg/kg/day) in their drinking water and subjected to a surgical induction of HF (descending aortic banding). Cardiac function was assessed using 2- and 4-dimensional echocardiography and molecular analysis was performed using high-throughput mRNA analysis to measure the expression of fibrosis-associated genes.
In male PAI-1 deficient mice post-surgical insult, left ventricular systolic function was impaired with a significantly reduced ejection fraction and disturbed longitudinal strain rate, but rescued by metformin treatment. Complementing the functional data, molecular analysis showed that fibrosis-related genes (ex., Tgfb1) were significantly down-regulated in metformin-treated males. Interestingly, in female mice, there was no change with metformin treatment in functional measurements, but fibrosis-related pathways were significantly down-regulated. Preliminary cell culture data revealed elevated levels of genes associated with fibrosis, Col1a1, Col3a1, and Tgfb1, in primary cardiac fibroblasts isolated from male PAI-1 deficient mice, compared to littermate controls.

Conclusion: Our findings provide mechanistic insights into using metformin as a therapy against CF in PAI-1 deficiency. Further, primary cardiac fibroblasts isolated from PAI-1-deficient mice display increased levels of fibrotic genes at a baseline measure providing critical data regarding the cellular mechanism of fibrosis development in PAI-1 deficiency. Future directions include protein expression analysis (ex., Tgfb1) using heart tissue from mice post-surgical insult and primary cardiac fibroblast isolation from female PAI-1-deficient mice accompanied by mRNA expression analysis (Col1a1, Col3a1, Tgfb1) to compare sexes.