Multiple cell types including melanocytes contribute to elastogenesis in the developing murine aortic valve

Elastic fibers are crucial for aortic valve (AoV) function and are generated and maintained by valvular interstitial cells (VICs). VICs exhibit diverse phenotypes, yet the specific subpopulation responsible for producing and regulating elastic fibers remains unclear. This gap in knowledge is significant, given that elastin (Eln) abnormalities lead to congenital AoV defects and initiate AoV diseases. This study characterizes the timing of Eln expression in murine AoV, revealing it peaks during late embryogenesis and early postnatal stages, decreasing in adulthood. Spatial transcriptomics and RT-qPCR indicate that Eln expression correlates with genes associated to elastogenesis, including Acta2, a smooth muscle cell marker. While Eln expression is not exclusive to a single VIC subpopulation, RNAscope and immunofluorescence demonstrate a population of Eln-expressing VICs that co-express alpha smooth muscle actin and melanocytic markers. As previously reported in adult mice, we show a relationship between AoV pigment and elastic fiber patterning during early postnatal stages and further show that melanocytes may play a critical role in elastogenesis. In summary, Eln is expressed in the AoV during early postnatal stages by cells co-expressing markers of various types, highlighting the complexity of VICs phenotypes and their role in elastic fiber regulation.