A role for T lymphocytes in mediating cardiac diastolic function.

Area of Science:

• Immunology
• Cardiology
• Biochemistry

Background:

• T helper (TH) lymphocytes differentiate into TH1 and TH2 subsets with distinct cytokine profiles and functions.
• The relationship between TH1/TH2 balance and cardiac fibroblast (CF) function, extracellular matrix (ECM) composition, and diastolic function remains unclear, especially in the absence of cardiac injury.

Purpose of the Study:

• To investigate the direct effects of selective TH1 and TH2 immune modulation on cardiac gene expression, ECM composition, and diastolic function in mice.
• To determine if T helper cell phenotypes influence cardiac fibroblast activity and extracellular matrix remodeling.

Main Methods:

• C57BL/J mice were treated with selective TH1 or TH2 inducers.
• Cardiac gene expression, ECM composition (collagen, cross-linking), and diastolic function (left ventricular stiffness) were assessed 12 weeks post-modulation.
• Coculturing experiments were performed using lymphocytes from treated mice and primary cardiac fibroblasts.

Main Results:

• TH1 induction significantly increased left ventricular stiffness and cardiac collagen content.
• TH2 induction significantly decreased left ventricular stiffness and cardiac collagen content, while increasing pro-matrix metalloproteinase (MMP)-9 and -13 gene expression.
• Lymphocytes directly modulated CF pro-collagen and pro-MMP gene expression and MMP activity.

Conclusions:

• The TH1/TH2 phenotype differentially regulates cardiac fibroblast function, ECM composition, and diastolic function.
• Modulation of TH lymphocyte subsets influences cardiac remodeling through effects on collagen and MMP pathways.
• Targeting TH lymphocyte function presents a potential therapeutic avenue for managing heart failure and post-myocardial infarction remodeling.