Identification of a novel flow-mediated gene expression signature in patients with bicuspid aortic valve

Abstract

Individuals with bicuspid aortic valve (BAV) are at significantly higher risk of developing serious aortic complications than individuals with tricuspid aortic valves (TAV). Studies have indicated an altered aortic blood flow in patients with BAV; however, the extent to which altered flow influences the pathological state of BAV aorta is unclear. In the present study, we dissected flow-mediated aortic gene expression in patients undergoing elective open heart surgery. A large collection of public microarray data sets were firstly screened for consistent co-expression with five well-characterized flow-regulated genes (query genes). Genes with co-expression probability of >0.5 were selected and further analysed in expression profiles (127 arrays) from ascending aorta of BAV and TAV patients. Forty-four genes satisfied two filtering criteria: a significant correlation with one or more of the query genes (R > 0.40) and differential expression between patients with BAV and TAV. No gene fulfilled the criteria in mammary artery (88 arrays), an artery not in direct contact with the valve. Fifty-five percent of the genes significantly altered between BAV and TAV patients showed differential expression between two identified flow regions in the rat aorta. A large proportion of the identified genes were related to angiogenesis and/or wound healing, with pro-angiogenesis genes downregulated and inhibitory genes upregulated in patients with BAV. Moreover, differential expression of ZFP36, GRP116 and PKD2 was confirmed using immunohistochemistry. Implementing a new strategy, we have demonstrated an angiostatic gene expression signature in patients with BAV, indicating impaired wound healing in these patients, potentially involved in BAV-associated aortopathy.

Fig. 1

Schematic illustration of data analysis workflow

Fig. 2

Immunostaining of GPR116 and PKD2 in non-dilated aorta of BAV and TAV patients. a, c GPR116 staining in BAV; b, d GPR116 staining in TAV; e, f vWF staining in BAV and TAV, respectively; g PKD2 staining in BAV; h PKD2 staining in TAV; i, j negative control. Scale bar = 100 μm

Fig. 3

Expression of query and non-query genes in uniform and disturbed flow pattern regions of rat aorta. Shown are PKD2 (a), GPR116 (b) and ZFP36 (c) mRNA expression. d Correlation between ZFP36 and TNF mRNA expression (n = 26). Gene expression was analysed by quantitative real-time PCR and normalized to TBP mRNA expression

Fig 4

Immunostaining of ZFP36 in non-dilated aorta of BAV (a, c) and TAV (b, d) patients. e, f vWF staining in BAV and TAV, respectively; g, h negative control. Scale bar = 100 μm