Expression and role of long non-coding RNA H19 in aortic valve development and disease
Vander Roest, Mark
Aortic valve disease, including developmental defects and late-stage fibrocalcific remodeling, is a major global health burden. There is no pharmaceutical treatment for valve disease, and options for valve replacement are limited. Many factors, including the NOTCH1 signaling pathway and mechanical stimulation, have been identified as shared regulators of valve development and disease, though obvious mutations or alterations in the NOTCH1 family are not found in the majority of instances of valve disease. Long non-coding RNA H19 has recently been shown to act as a repressor of NOTCH1 in aortic valve disease and is highly expressed during embryonic development, suggesting a possible role in this process as well. Furthermore, expression of H19 is tightly controlled by genetic imprint, and loss of this imprint can result in dramatic dysregulation of H19 expression, leading to NOTCH1 repression and valve disease in the absence of known mutation. Therefore, H19 was investigated as regulator of valve development and disease using mechanically stimulated induced pluripotent stem cell differentiation to endothelial cells as an in vitro developmental model and using a cohort of aged, apparently healthy mice to investigate H19 as an initiating factor of valve disease in the absence of disease-driving mutation or injury. H19 was found to be upregulated by mechanical strain during endothelial differentiation, as were markers of endothelial cell identity. Strain-differentiated endothelial cells have higher tube formation capacity in a Matrigel angiogenesis assay, and this effect was traced to upregulation of H19 using an H19 overexpression model in human umbilical vein endothelial cells. Loss-of-imprint and dysregulation of H19 was not observed in mature murine aortic valves, suggesting that this is not a likely method of disease initiation or that species specific differences exist between mice and humans. These findings have implications for our understanding of valve disease and development of better therapeutic treatment of valve disease, including development of a tissue engineered heart valve.