Developmental changes in myocardial B cells mirror changes in B cells associated with different organs

Area of Science:

• Immunology
• Developmental Biology
• Cardiovascular Research

Background:

• The naive heart contains intravascular B cells interacting with cardiac microvasculature.
• The developmental timing and organ specificity of these myocardial B cells are currently unknown.

Purpose of the Study:

• To systematically analyze the appearance, phenotype, and organ specificity of B cells in the heart from embryonic life to adulthood.
• To investigate the dynamic changes in B cell subpopulations within the myocardium during development.

Main Methods:

• Isolation and flow cytometric analysis of B cells from the myocardium, lungs, liver, and spleen at various developmental stages.
• Histological analysis and intravital microscopy to assess B cell localization and interaction with microvasculature.
• Single-cell RNA sequencing (scRNAseq) to determine the transcriptional profile of myocardial B cells.

Main Results:

• Myocardial B cell phenotype exhibits dynamic changes, shifting from CD11b+ in neonates to CD11b-CD21+CD23+ in adults.
• Organ-associated B cells interacting with microvasculature are present in the lungs and liver, not exclusive to the heart.
• Dynamic changes in B cell subpopulations in the heart mirror those observed in other organs.
• scRNAseq reveals myocardial B cells are part of a broader population of organ-associated B cells with unique transcriptional signatures.

Conclusions:

• Myocardial B cells undergo significant developmental changes in phenotype.
• The presence and dynamics of B cells in the heart are not organ-specific, suggesting a broader developmental process.
• Myocardial B cells possess distinct transcriptional profiles, contributing to a more comprehensive understanding of organ-associated B cell populations and naive B cell dynamics during development.