Neutrophils Modulate Fibroblast Function and Promote Healing and Scar Formation after Murine Myocardial Infarction

Area of Science:

• Cardiovascular Biology
• Immunology
• Wound Healing Research

Background:

• Neutrophil recruitment to the heart post-myocardial infarction (MI) triggers inflammation and adverse left ventricular (LV) remodeling.
• Therapeutic inhibition of neutrophil infiltration in MI patients has yielded no benefits, indicating a complex role beyond inflammation.

Purpose of the Study:

• To investigate the specific effects of neutrophils on cardiac fibroblast function after MI.
• To elucidate the mechanisms by which neutrophils influence the cardiac healing process post-MI.

Main Methods:

• Co-incubation of isolated cardiac fibroblasts with neutrophils.
• Assessment of extracellular matrix protein production and collagen synthesis.
• Analysis of transforming growth factor (TGF)-ß1 expression in fibroblasts.

Main Results:

• Neutrophil co-incubation enhanced provisional extracellular matrix protein production by cardiac fibroblasts.
• Neutrophil presence reduced collagen synthesis compared to controls or mononuclear cell co-incubation.
• Neutrophils were essential for transiently up-regulating TGF-ß1 expression in fibroblasts, facilitating scar maturation.

Conclusions:

• Neutrophils are critical for both initiating and resolving inflammation after MI.
• They modulate cardiac fibroblast activity, influencing the transition from inflammation to repair and scar formation.
• Caution is advised when considering therapeutic strategies to inhibit neutrophil recruitment in MI patients.