Shared gene expression profiles in developing heart valves and osteoblast progenitor cells.

Area of Science:

• Cardiovascular Biology
• Developmental Biology
• Molecular Biology

Background:

• Atrioventricular (AV) valves develop from mesenchymal endocardial cushions into stratified structures with diverse extracellular matrix (ECM).
• Mature AV valves express osteogenesis-associated genes and are prone to calcification, suggesting shared regulatory pathways with bone progenitor cells.

Purpose of the Study:

• To define gene regulatory programs in valvulogenesis compared to osteoblast progenitors.
• To investigate shared gene expression profiles between developing heart valves and bone precursor cells.

Main Methods:

• Affymetrix gene expression profiling of murine embryonic day (E)12.5 AV endocardial cushions and E17.5 AV valves (mitral and tricuspid).
• Comparison of valve gene expression with preosteoblast MC3T3-E1 cells.

Main Results:

• MC3T3 cells showed greater similarity to E17.5 valves than E12.5 cushions, supporting shared gene expression in valve maturation and osteoblasts.
• Transcription factors like Twist1 were predominant in early cushions (E12.5).
• Valve maturation involved differential regulation of matrix metalloproteinases, their inhibitors, collagen genes, and enrichment of small leucine-rich proteoglycans (SLRPs) like Asporin.

Conclusions:

• Developing heart valves and osteoblast bone precursor cells share gene expression profiles.
• These shared pathways are active in normal valve development and homeostasis.
• Understanding these shared pathways may offer insights into the mechanisms of calcific valve disease.