Cardiac myxoma cells exhibit embryonic endocardial stem cell features

Area of Science:

• Cardiovascular Pathology
• Developmental Biology
• Cellular Biology

Background:

• The origin of cardiac myxoma, the most common heart tumor, is uncertain.
• Previous studies show heterogeneous results regarding myxoma cell characteristics.
• Current hypotheses suggest origin from primitive pluripotential cardiogenic cells.

Purpose of the Study:

• To investigate the expression of actin isoforms and early cardiac differentiation markers in cardiac myxomas.
• To explore the cellular origin and differentiation pathways of cardiac myxoma cells.
• To test the hypothesis of adult developmental remnants as the source of cardiac myxomas.

Main Methods:

• Immunohistochemistry and RT-PCR on 30 left atrial myxomas and 8 consecutive tumors.
• Confocal microscopy to analyze cell marker co-expression.
• In vitro culture of myxoma cells to assess phenotypic stability.

Main Results:

• Alpha-smooth muscle actin (alpha-SMA) was detected in all myxomas; alpha-cardiac actin was rare, and alpha-skeletal actin was absent.
• Vessel-like structures showed CD34 and alpha-SMA expression, with focal co-expression in myxoma cells.
• Transcripts for Sox9, Notch1, NFATc1, Smad6, and metalloproteinases were present, indicating early cardiac differentiation markers.

Conclusions:

• Cardiac myxoma cells exhibit phenotypic markers of embryonic endothelial-to-mesenchymal transformation.
• These findings support the hypothesis that cardiac myxomas may arise from adult developmental remnants.
• Myxoma cells demonstrate sustained phenotypic heterogeneity, including alpha-SMA expression and stress fiber formation in vitro.