Splenic Marginal Zone B Lymphocytes Regulate Cardiac Remodeling After Acute Myocardial Infarction in Mice

Area of Science:

• Cardiovascular Research
• Immunology
• Molecular Biology

Background:

• Mature B lymphocytes influence cardiac recovery following acute myocardial infarction (MI).
• Splenic marginal zone B (MZB) cells are distinct B cell populations with specific functions.
• MicroRNA-21 (miR21) and hypoxia-inducible factor-α (HIF-α) pathways regulate B cell functions.

Purpose of the Study:

• To investigate the specific role of MZB cells in post-ischemic cardiac injury.
• To elucidate the function of endogenous miR21/HIF-α signaling within MZB cells during cardiac repair.

Main Methods:

• Acute myocardial infarction (MI) induced in mice via coronary artery ligation.
• Cardiac function and remodeling assessed using echocardiography and immunohistochemistry.
• MZB cell-specific deletion of Notch signaling or Hif1a to evaluate their roles.

Main Results:

• MI increased miR21-dependent HIF-1α expression, particularly in splenic MZB cells.
• Deficiency or targeted deletion of miR21/HIF-1α in MZB cells improved cardiac function post-MI.
• miR21/HIF-1α signaling in MZB cells promoted CCL7 expression, increasing inflammatory monocyte infiltration and adverse cardiac remodeling.

Conclusions:

• The miR21/HIF-1α pathway in splenic MZB cells plays a critical role in cardiac dysfunction after MI.
• Targeting this pathway in MZB cells offers a potential therapeutic strategy for modulating cardiac function post-MI.