(H-297) UNDERSTANDING THE CORRELATION BETWEEN AORTIC VALVE PIGMENTATION, MELANIN PRODUCTION AND ELASTIN FIBER ABUNDANCE

Introduction::
The aortic valve (AoV) is a complex structure responsible for blood flow from the left ventricle to the aorta during systole while, preventing backflow into the left ventricle when the heart rests during diastole. Elastin-based fibers store elastic energy during diastolic closure and aid in recoil during opening. Alterations to elastin can lead to valve disease. Previous studies report a correlation between melanocytic pigmentation in aortic valve leaflet and elastic fiber alignment and abundance. However, the involvement of melanocytes in elastogenesis is unknown. An incomplete understanding of elastin generation has hindered therapeutic efforts. This study aimed to establish a correlation between the presence of pigment, expression of melanocytic phenotypic markers, and elastic fiber abundance in AoV leaflets.




Materials and Methods::
Three mouse models with different levels of AoV leaflet pigmentation-Wildtype (C57BL/6J), Albino(B6(Cg)-Tyrc-2J/J) and Kit Heterozygous –were used. AoV leaflets from these mice were extracted, and fluorescence staining for elastic fibers was performed using the AF633 probe. Quantitative assessments of elastin fiber were done using a customized Matlab script. The expression of melanocytic markers (Tyr and DCT) was analyzed using RT-qPCR.




Results, Conclusions, and Discussions::
We observed elastic fibers radially aligned within the ventricularis layer (proximal to the left ventricle) of the AoV leaflet with a change toward a circumferential alignment toward the fibrosa layer (proximal to the aorta). Among the WT mice, all three leaflets (left, right and non-coronary) were pigmented approximately 56% of the time (WT1, n=43), whereas the left coronary leaflets lacked pigmentation approximately 44% of the time (WT2, n=43). We observed the pigmented WT1 mice exhibited statistically higher abundance of elastic fibers compared to the non-pigmented Albino and KH mice. However, the difference in elastic fiber abundance between the fully pigmented WT1 and the partially pigmented WT2 was not statically significant. Although we observed trending differences in elastic fiber abundance within the leaflets in each mouse model, the differences did not reach statistical significance. Interestingly, WT2 AoV leaflets exhibited significantly higher expression of melanocytic markers.









Our data demonstrate that neither the abundance of pigmentation nor presence/absence of melanocytic markers is sufficient to explain the elastin phenotype despite the differences in elastic fiber abundance due to the genetic alterations in melanocytic populations. Additionally, our results suggest additional mechanisms contribute to elastogenesis beyond pigmentation or melanocytic gene expression. Further studies are needed to understand the role of melanocytic populations in elastogenesis during AoV development. A thorough understanding of the developmental changes in the AoV and their relationship to elastogenesis may help to elucidate the pathogenesis of aortic valve disorders and pave a way for new diagnostic and therapeutic strategies.




Acknowledgements (Optional): : I would like to express my sincere gratitude to my advisor Dr.Hutcheson, Dr. Lidia kos, and my mentor Daniel Chaparro for their constant support, guidance, and encouragement.and my sponsor Fulbright (Fulbright Nepal) for funding my studies at Florida International University.


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