Novel Association of miR-451 with the Incidence of TEVG Stenosis in a Murine Model

The development of a tissue-engineered vascular graft (TEVG) holds great promise for advancing the field of cardiac surgery. Despite the successful translation of this technology, previous reports identify the primary mode of graft failure as stenosis secondary to intimal hyperplasia. MicroRNAs (miRNAs) regulate gene expression by interfering with mRNA function and recent research has suggested miRNA as a potential therapeutic target. The role of miRNAs in TEVGs during neotissue formation is currently unknown. In this study, we investigated if miRNAs regulate the inhibition of graft stenosis. Biodegradable PGA-P(LA/CL) scaffolds were implanted as inferior vena cava interposition grafts in a murine model (n=14). Mice were sacrificed 14 days following implantation and TEVGs were harvested for histological analysis and miRNA profiling using Affymetrix miRNA arrays. Graft diameters were measured histologically, and the largest grafts (patent group) and smallest grafts (stenosed group) were profiled (n=4 for each group). Cell population in each graft was analyzed with immunohistochemistry using antismooth muscle actin (SMA) and antimacrophage (F4/80) antibodies. The graft diameter was significantly greater in the patent group (0.63 +/- 0.06mm) than in the stenosed group (0.17 +/- 0.06mm) (p<0.01). Cell proliferation was significantly greater in the stenosed grafts than in patent grafts (p<0.01: SMA [187 +/- 11 vs. 77 +/- 8 cells] vs. p=0.025: F4/80 [245 +/- 23 vs. 187 +/- 11 cells]). MiRNA array of 1416 genes showed that in stenosed grafts, mir-451, mir-338, and mir-466 were downregulated and mir-154 was upregulated. Mir-451 exhibited the greatest difference in expression between stenosed and patent grafts by -3.1-fold. Significant negative correlation was found between the expression of mir-451 and cell proliferation (SMA: r=-0.86, p=0.003; F4/80: r=-0.89, p=0.001). Our data, along with previous evidence that mir-451 regulates tumor suppressor genes, suggest that downregulation of mir-451 promotes acute proliferation of macrophages and smooth muscle cells, thereby inducing TEVG stenosis. Adequate expression of mir-451 may be critical for improving TEVG patency.