Interdisciplinary Stem Cell Institute, Leonard M. Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
Proc Natl Acad Sci U S A. 2013 Feb 19;110(8):2834-9. doi: 10.1073/pnas.1220185110. Epub 2013 Jan 3.
Although nitric oxide (NO) signaling promotes differentiation and maturation of endothelial progenitor cells, its role in the differentiation of mesenchymal stem cells (MSCs) into endothelial cells remains controversial. We tested the role of NO signaling in MSCs derived from WT mice and mice homozygous for a deletion of S-nitrosoglutathione reductase (GSNOR(-/-)), a denitrosylase that regulates S-nitrosylation. GSNOR(-/-) MSCs exhibited markedly diminished capacity for vasculogenesis in an in vitro Matrigel tube-forming assay and in vivo relative to WT MSCs. This decrease was associated with down-regulation of the PDGF receptorα (PDGFRα) in GSNOR(-/-) MSCs, a receptor essential for VEGF-A action in MSCs. Pharmacologic inhibition of NO synthase with L-N(G)-nitroarginine methyl ester (L-NAME) and stimulation of growth hormone-releasing hormone receptor (GHRHR) with GHRH agonists augmented VEGF-A production and normalized tube formation in GSNOR(-/-) MSCs, whereas NO donors or PDGFR antagonist reduced tube formation ∼50% by murine and human MSCs. The antagonist also blocked the rescue of tube formation in GSNOR(-/-) MSCs by L-NAME or the GHRH agonists JI-38, MR-409, and MR-356. Therefore, GSNOR(-/-) MSCs have a deficient capacity for endothelial differentiation due to downregulation of PDGFRα related to NO/GSNOR imbalance. These findings unravel important aspects of modulation of MSCs by VEGF-A activation of the PDGFR and illustrate a paradoxical inhibitory role of S-nitrosylation signaling in MSC vasculogenesis. Accordingly, disease states characterized by NO deficiency may trigger MSC-mediated vasculogenesis. These findings have important implications for therapeutic application of GHRH agonists to ischemic disorders.
尽管一氧化氮 (NO) 信号促进内皮祖细胞的分化和成熟，但它在间充质干细胞 (MSCs) 分化为内皮细胞中的作用仍存在争议。我们测试了 NO 信号在来自 WT 小鼠和 S-亚硝基谷胱甘肽还原酶 (GSNOR(-/-)) 纯合缺失小鼠的 MSCs 中的作用，GSNOR(-/-) 是一种调节 S-亚硝基化的脱亚硝酶。与 WT MSCs 相比，GSNOR(-/-)MSCs 在体外 Matrigel 管形成测定和体内的血管生成能力明显降低。这种减少与 GSNOR(-/-)MSCs 中 PDGF 受体α (PDGFRα) 的下调有关，PDGFRα 是 VEGF-A 在 MSCs 中作用所必需的受体。用 L-N(G)-硝基精氨酸甲酯 (L-NAME) 抑制一氧化氮合酶和用生长激素释放激素受体 (GHRHR) 激动剂刺激 GHRHR 可增加 VEGF-A 的产生并使 GSNOR(-/-)MSCs 的管形成正常化，而 NO 供体或 PDGFR 拮抗剂使小鼠和人类 MSCs 的管形成减少约 50%。该拮抗剂还阻断了 L-NAME 或 GHRHR 激动剂 JI-38、MR-409 和 MR-356 对 GSNOR(-/-)MSCs 管形成的挽救作用。因此，GSNOR(-/-)MSCs 由于与 NO/GSNOR 失衡相关的 PDGFRα 下调而内皮分化能力不足。这些发现揭示了 VEGF-A 激活 PDGFR 对 MSCs 调节的重要方面，并说明了 S-亚硝基化信号在 MSC 血管生成中的矛盾抑制作用。因此，NO 缺乏症的疾病状态可能会引发 MSC 介导的血管生成。这些发现对生长激素释放激素激动剂治疗缺血性疾病具有重要意义。
