F Senger(1, 2), E Haas(1), A Remes(2), C Tannert(2), N Schmiedel(2), O Müller(2), C Kuhn(2), N Frey(1)

1. Department of Internal Medicine III, University Hospital Heidelberg, Germany; 2. Department of Internal Medicine III, University Hospital Kiel, and German Centre of Cardiovascular Research, Partner Site Hamburg/Kiel/Lübeck, Germany

Background
Autophagy dysregulation can have adverse effects on cardiac remodeling. FYCO1, a stimulator of autophagy, facilitates the transport of autophagosomes, thereby enhancing autophagic flux. This study investigates the in vivo impact of FYCO1 on myocardial healing through autophagy modulation.

Methods
FYCO1-Tg mice crossed with RFP-EGFP-LC3 reporter mice were used to analyze autophagic flux via confocal microscopy after permanent ligation of the left anterior descending artery. Autophagy activity was evaluated by Western blot. Macrophage infiltration and apoptosis were assessed by immunofluorescence microscopy, while Masson Trichrome staining detected fibrosis and infarct size. Cardiac function was determined by echocardiography.

Results
FYCO1-TGxRGFP mice displayed significantly enhanced autophagic flux post-MI, as shown by increased p62 (WT LAD: 2,9±0,4; TG LAD:4,0±0,5) and LC3 II (WT LAD: 1,6±0,2; TG LAD:14,0±1,4) protein levels. Confocal microscopy revealed an accumulation of autolysosomes in WT mice 30 days post-MI (WT autophagosomes: 1±0,4; WT autolysosomes: 38,6±3,8), contrasting with the sustained ratio of autophagosomes to autolysosomes in FYCO1-TGxRGFP mice (TG autophagosomes:43,3±5,1; TG autolysosomes: 73,5±12,4), implying the preservation of adequate autophagic flux. FYCO1 overexpression was associated with diminished macrophage infiltration into the infarct border zone and reduced induction of apoptosis, as demonstrated by caspase activity. Furthermore, FYCO1-TGxRGFP mice exhibited significantly reduced fibrosis (WT:19,6±1,8%; TG:10,6±1,6%) and infarct size in the left ventricle (WT:34,5 ±3,9%; TG:5,5±2%), accompanied by marked improvements in global heart function post-MI (EF WT: 32,7±3,2%; TG: 56,4±3,9%) compared to WT.

Conclusion
FYCO1 mitigates adverse consequences of ischemic injury through the induction of autophagy and a previously unrecognized role in modulating inflammation in response to myocardial infarction.