Abdominal aortic aneurysm (AAA) is a common disease among elderly people that, when surgical treatment is inapplicable, results in progressive expansion and rupture of the aorta with high mortality. Although nonsurgical treatment for AAA is much awaited, few options are available because its molecular pathogenesis remains elusive. Here, we identify JNK as a proximal signaling molecule in the pathogenesis of AAA. Human AAA tissue showed a high level of phosphorylated JNK. We show that JNK programs a gene expression pattern in different cell types that cooperatively enhances the degradation of the extracellular matrix while suppressing biosynthetic enzymes of the extracellular matrix. Selective inhibition of JNK in vivo not only prevented the development of AAA but also caused regression of established AAA in two mouse models. Thus, JNK promotes abnormal extracellular matrix metabolism in the tissue of AAA and may represent a therapeutic target.

It is well known that the implantation of bone marrow mononuclear cells (BM-MNCs) into ischemic hearts can induce angiogenesis and improve cardiac function after myocardial infarction, but the precise mechanisms of these actions are unclear. We hypothesize that the cytokines produced by BM-MNCs play a key role in this cell-based therapy. BM-MNCs from rats were cultured under normoxic or hypoxic (1% O2) conditions for 24 h, and then supernatants were collected for study. ELISA and Western blotting analysis showed that various cytokines, including VEGF, IL-1 beta, PDGF, and IGF-1, were produced from BM-MNCs, some of which were enhanced significantly under hypoxia stimulation. When compared with a control blank medium, the supernatants of BM-MNCs cultured under normoxic or hypoxic conditions inhibited apoptosis significantly and preserved the contractile capacity of isolated adult rat cardiomyocytes in vitro (P < 0.05). Using a rat model of acute myocardial infarction, we injected the supernatants of BM-MNCs or control medium intramyocardially on day 0 and then intraperitoneally on days 2, 4, and 6 after infarction. When compared with the control medium, the supernatants of BM-MNCs cultured under both normoxic or hypoxic conditions increased the microvessel density and decreased the fibrotic area in the infarcted myocardium significantly, contributing to remarkable improvement in cardiac function. Various cytokines were produced by BM-MNCs, and these cytokines contributed to functional improvement of the infarcted heart by directly preserving the contractile capacity of the myocardium, inhibiting apoptosis of cardiomyocytes, and inducing therapeutic angiogenesis of the infarcted heart.

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Background-Recent studies have shown that bone marrow-derived stem cells differentiate into the phenotype of cardiomyocytes in vivo and in vitro. We tried to regenerate infarcted myocardium by implanting ex vivo transforming growth factor (TGF)-␤-preprogrammed CD117 (c-kit)-positive (CD117 ϩ ) stem cells intramyocardially. Methods and Results-CD117ϩ cells were isolated from the bone marrow mononuclear cells of GFP-transgenic or normal C57/BL6 mice. The myogenic differentiation of CD117 ϩ cells was achieved by cultivation with TGF-␤. Using an acute myocardial infarction model, we also tried to regenerate infarcted myocardium by implanting untreated (newly isolated) or preprogrammed (24 hours of cultivation with 5 ng/mL TGF-␤ 1 ) CD117 ϩ cells intramyocardially. TGF-␤ increased the cellular expression of myosin, troponins, connexin-43, GATA-4, and NKx-2.5, which suggested that it induced the myogenic differentiation of CD117 ϩ cells. Compared with the effects of PBS injection only, the microvessel density in the infarcted myocardium was increased significantly 3 months after the implantation of either TGF-␤-preprogrammed or untreated CD117 ϩ cells. Moreover, many of the TGF-␤-preprogrammed CD117 ϩ cells were stained positively for myosin, whereas few of the untreated CD117 ϩ cells were. Histological analysis revealed newly regenerated myocardium in the left ventricular anterior wall after the implantation of TGF-␤-preprogrammed cells but not untreated cells. Furthermore, the left ventricular percent fraction shortening was significantly higher after the implantation of TGF-␤-preprogrammed cells than after the implantation of untreated CD117 ϩ cells. Conclusions-TGF-␤ conducted the myogenic differentiation of CD117ϩ stem cells by upregulating GATA-4 and NKx-2.5 expression. Therefore, the intramyocardial implantation of TGF-␤-preprogrammed CD117 ϩ cells effectively assisted the myocardial regeneration and induced therapeutic angiogenesis, contributing to functional cardiac regeneration. (Circulation. 2005;111:2438-2445.)

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