From Department of Biomedical Sciences (B.C., S.-M.K., E.- J.L., S.R.L., S.-W.K., E.-J.C.), Division of Cardiology (S.L., D.- H.K., J.Y.J., J.-K.S.), and Division of Endocrinology and Metabolism, Department of Internal Medicine (K.-U.L.), Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
Circulation. 2017 May 16;135(20):1935-1950. doi: 10.1161/CIRCULATIONAHA.116.024270. Epub 2017 Feb 8.
Calcification of the aortic valve leads to increased leaflet stiffness and consequently to the development of calcific aortic valve disease. However, the underlying molecular and cellular mechanisms of calcification remain unclear. Here, we identified that dipeptidyl peptidase-4 (DPP-4, also known as CD26) increases valvular calcification and promotes calcific aortic valve disease progression.
We obtained the aortic valve tissues from humans and murine models (wild-type and endothelial nitric oxide synthase-deficient-mice) and cultured the valvular interstitial cells (VICs) and valvular endothelial cells from the cusps. We induced osteogenic differentiation in the primary cultured VICs and examined the effects of the DPP-4 inhibitor on the osteogenic changes in vitro and aortic valve calcification in endothelial nitric oxide synthase-deficient-mice. We also induced calcific aortic stenosis in male New Zealand rabbits (weight, 2.5-3.0 kg) by a cholesterol-enriched diet+vitamin D2 (25 000 IU, daily). Echocardiography was performed to assess the aortic valve area and the maximal and mean transaortic pressure gradients at baseline and 3-week intervals thereafter. After 12 weeks, we harvested the heart and evaluated the aortic valve tissue using immunohistochemistry.
We found that nitric oxide depletion in human valvular endothelial cells activates NF-κB in human VICs. Consequently, the NF-κB promotes DPP-4 expression, which then induces the osteogenic differentiation of VICs by limiting autocrine insulin-like growth factor-1 signaling. The inhibition of DPP-4 enzymatic activity blocked the osteogenic changes in VICs in vitro and reduced the aortic valve calcification in vivo in a mouse model. Sitagliptin administration in a rabbit calcific aortic valve disease model led to significant improvements in the rate of change in aortic valve area, transaortic peak velocity, and maximal and mean pressure gradients over 12 weeks. Immunohistochemistry staining confirmed the therapeutic effect of Sitagliptin in terms of reducing the calcium deposits in the rabbit aortic valve cusps. In rabbits receiving Sitagliptin, the plasma insulin-like growth factor-1 levels were significantly increased, in line with DPP-4 inhibition.
DPP-4-dependent insulin-like growth factor-1 inhibition in VICs contributes to aortic valve calcification, suggesting that DPP-4 could serve as a potential therapeutic target to inhibit calcific aortic valve disease progression.
主动脉瓣钙化导致瓣叶僵硬，进而导致钙化性主动脉瓣疾病的发展。然而，钙化的潜在分子和细胞机制仍不清楚。在这里，我们发现二肽基肽酶 4（DPP-4，也称为 CD26）可增加瓣膜钙化并促进钙化性主动脉瓣疾病的进展。
我们从人类和鼠模型（野生型和内皮型一氧化氮合酶缺陷型小鼠）中获得主动脉瓣组织，并培养瓣环间质细胞（VIC）和瓣环内皮细胞。我们在原代培养的 VIC 中诱导成骨分化，并在体外和内皮型一氧化氮合酶缺陷型小鼠中研究 DPP-4 抑制剂对成骨变化和主动脉瓣钙化的影响。我们还通过富含胆固醇的饮食+维生素 D2（25,000IU，每日）在雄性新西兰兔（体重 2.5-3.0kg）中诱导钙化性主动脉瓣狭窄。通过超声心动图在基线和此后每 3 周评估主动脉瓣面积以及最大和平均跨主动脉压力梯度。12 周后，我们收获心脏并使用免疫组织化学评估主动脉瓣组织。
我们发现，人瓣膜内皮细胞中的一氧化氮耗竭可在人 VIC 中激活 NF-κB。NF-κB 随后通过限制自分泌胰岛素样生长因子-1 信号转导来促进 VIC 的成骨分化。DPP-4 酶活性的抑制可阻止体外 VIC 的成骨变化，并减少体内小鼠模型的主动脉瓣钙化。在兔钙化性主动脉瓣疾病模型中给予西他列汀治疗可在 12 周内显著改善主动脉瓣面积、跨主动脉峰值速度以及最大和平均压力梯度的变化率。免疫组织化学染色证实了西他列汀在减少兔主动脉瓣瓣尖钙沉积方面的治疗效果。接受西他列汀治疗的兔子中，胰岛素样生长因子-1 水平显著升高，与 DPP-4 抑制一致。
VIC 中 DPP-4 依赖性胰岛素样生长因子-1 抑制可导致主动脉瓣钙化，提示 DPP-4 可作为抑制钙化性主动脉瓣疾病进展的潜在治疗靶点。
