Background
Cardiac fibroblasts (CFs) play a pivotal role in cardiac remodeling following obstructive myocardial infarction (MI-CAD). They are a crucial mediator in extracellular matrix remodeling, inflammation and fibrosis. However, their role in myocardial infarction with non-obstructive coronary arteries (MINOCA) is poorly understood. This condition accounts for up to 14% of all MI-CAD cases and is associated with diffuse micro-infarctions caused by various factors, such as coronary artery spasms and plaque erosion. MINOCA is associated with poor prognosis due to diagnostic challenges and the absence of targeted therapies. The current study aims to gather a comprehensive understanding of the differential responses of CFs to circulating signals in MINOCA versus MI-CAD, with the goal of revealing novel diagnostic biomarkers and therapeutic targets for this unique patient population.
Methods
Primary human CFs were exposed for up to 72 hours to 5% plasma obtained from female porcine models of acute MI-CAD or MINOCA (300 minutes post-infarction). MI-CAD was induced via transient balloon occlusion of the coronary artery, while MINOCA was modeled through intracoronary administration of autologous microthrombi. Control groups included plasma from healthy pigs, fetal calf serum (FCS) and Transforming Growth Factor β (TGFβ) as inflammatory phenotype control. Cellular responses were assessed in terms of proliferation (cell counts, Ki-67 immunofluorescence), apoptosis (Caspase 3/7 activity), myofibroblast differentiation (qRT-PCR) and cytokine secretion (ELISA).
Results
Plasma of neither MINOCA nor MI-CAD affected the proliferation of CFs compared to control conditions. Instead, a higher apoptosis was observed in MI-CAD-plasma treated CFs compared to MINOCA and controls at 24 h and 48 h but not at later time points. Expression of 96 mRNAs showed significant alterations across multiple mRNAs such as among others higher TGFβ, Connective Tissue Growth Factor (CTGF), Thrombospondin-1 (TSP-1) and TSP-2 expression in MI-CAD compared to MINOCA treatment. Contrarily, in MINOCA treatment, higher expression of Interleukin (IL) 1-α and Tissue Inhibitor of Metalloproteinases 2 (TIMP2) among others was observed. Secretion of IL-1β, IL-6 and IL-8 showed no differences between plasma treated groups. As for the porcine plasma itself, total TGFβ concentration was significantly increased in porcine plasma of MINOCA compared to MI-CAD animals.
Conclusion
Our data suggests that MINOCA is not only different to MI-CAD in clinical terms but also has distinct effects on CFs at the cellular level, showing significant differences in multiple aspects such as survival and expression patterns, but also cytokine content of the plasma itself differs. Overall, our research may enhance our understanding of MINOCA and contribute to the development of novel diagnostic and therapeutic strategies to mitigate myocardial damage and improve patient outcomes in this understudied disorder.
