Valproic acid (VPA), a histone deacetylase (HDAC) inhibitor is a widely used anticonvulsant drug. VPA is also under clinical evaluation to be employed in anticancer therapy, as an antithrombotic agent or a molecule to be used in the stem cells expansion protocols. Since endothelial colony forming cells (ECFC) has been identified as the human postnatal vasculogenic cells involved in thrombotic disorders and serve as a promising source of immature cell for vascular repair, objectives of the present study were to determine how VPA contributes to ECFC commitment and their angiogenic properties. We examined the effect of VPA on ECFC obtained from cord blood by evaluating colony number, proliferation, migration and their sprouting ability in vitro, as well as their in vivo vasculogenic properties. VPA inhibited endothelial differentiation potential from of cord blood derived stem cells associated with decreased proliferation and sprouting activity of cultured ECFC. VPA treatment significantly decreased the vessel-forming ability of ECFC transplanted together with mesenchymal stem cells (MSC) in Matrigel implants in nude mice model. Surprisingly, a microscopic evaluation revealed that VPA induces marked morphological changes from a cobblestone-like EC morphology to enlarged spindle shaped morphology of ECFC. RT-qPCR and a CD31/CD90 flow cytometry analysis confirmed a phenotypic switch of VPA-treated ECFC to mesenchymal-like phenotype. In conclusion, the pan-HDAC inhibitor VPA described for expansion of hematopoietic stem cells and very small embryonic like stem cells cannot be successfully employed for differentiation of endothelial lineage committed ECFC into functional endothelial cells. Our data also suggest that VPA based therapeutics may induce endothelial dysfunction associated with fibrosis that might induce thrombosis recurrence or venous insufficiency.

中文翻译：

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丙戊酸减少内皮细胞集落形成细胞分化并诱导内皮细胞向间充质样转变过程。

丙戊酸（VPA）是一种组蛋白脱乙酰基酶（HDAC）抑制剂，是一种广泛使用的抗惊厥药。VPA也正在临床评估中，以用作抗血栓形成剂或干细胞扩增方案中使用的分子，用于抗癌治疗。由于内皮集落形成细胞（ECFC）已被确定为参与血栓形成疾病的人类产后血管生成细胞，并且是有希望的未成熟细胞用于血管修复的来源，因此本研究的目标是确定VPA如何促进ECFC的承诺及其血管生成特性。我们通过评估菌落数，增殖，迁移及其在体外的发芽能力以及其体内血管生成特性，研究了VPA对从脐带血获得的ECFC的影响。VPA抑制了脐血来源干细胞的内皮分化潜能，与培养的ECFC的增殖和发芽活性降低相关。VPA处理显着降低了裸鼠模型中Matrigel植入物中与间充质干细胞（MSC）一起移植的ECFC的血管形成能力。出乎意料的是，显微镜评估显示，VPA诱导了从鹅卵石样EC形态到ECFC扩大的纺锤形形态的明显形态变化。RT-qPCR和CD31 / CD90流式细胞仪分析证实了VPA处理的ECFC向间充质样表型的表型转换。结论，用于扩增造血干细胞和非常小的胚胎样干细胞的泛HDAC抑制剂VPA无法成功地用于将内皮谱系定型ECFC分化为功能性内皮细胞。我们的数据还表明，基于VPA的疗法可能会诱发与纤维化相关的内皮功能障碍，从而可能导致血栓形成复发或静脉供血不足。