Feinberg Cardiovascular Research Institute, Northwestern University, Chicago, IL 60611, USA.
Circ Res. 2011 Sep 16;109(7):724-8. doi: 10.1161/CIRCRESAHA.111.253286. Epub 2011 Aug 11.
Transplantation of human CD34(+) stem cells to ischemic tissues has been associated with reduced angina, improved exercise time, and reduced amputation rates in phase 2 clinical trials and has been shown to induce neovascularization in preclinical models. Previous studies have suggested that paracrine factors secreted by these proangiogenic cells are responsible, at least in part, for the angiogenic effects induced by CD34(+) cell transplantation.
Our objective was to investigate the mechanism of CD34(+) stem cell-induced proangiogenic paracrine effects and to examine if exosomes, a component of paracrine secretion, are involved.
Exosomes collected from the conditioned media of mobilized human CD34(+) cells had the characteristic size (40 to 90 nm; determined by dynamic light scattering), cup-shaped morphology (electron microscopy), expressed exosome-marker proteins CD63, phosphatidylserine (flow cytometry) and TSG101 (immunoblotting), besides expressing CD34(+) cell lineage marker protein, CD34. In vitro, CD34(+) exosomes replicated the angiogenic activity of CD34(+) cells by increasing endothelial cell viability, proliferation, and tube formation on Matrigel. In vivo, the CD34(+) exosomes stimulated angiogenesis in Matrigel plug and corneal assays. Interestingly, exosomes from CD34(+) cells but not from CD34(+) cell-depleted mononuclear cells had angiogenic activity.
Our data demonstrate that human CD34(+) cells secrete exosomes that have independent angiogenic activity both in vitro and in vivo. CD34(+) exosomes may represent a significant component of the paracrine effect of progenitor cell transplantation for therapeutic angiogenesis.
将人 CD34(+) 干细胞移植到缺血组织中与减轻心绞痛、提高运动时间和降低 2 期临床试验中的截肢率有关，并已在临床前模型中显示出诱导新血管生成的作用。先前的研究表明，这些促血管生成细胞分泌的旁分泌因子至少部分负责 CD34(+)细胞移植诱导的血管生成作用。
我们的目的是研究 CD34(+) 干细胞诱导的促血管生成旁分泌作用的机制，并研究外泌体（旁分泌分泌的一部分）是否参与其中。
从动员的人 CD34(+) 细胞的条件培养基中收集的外泌体具有特征大小（40 至 90nm；通过动态光散射确定）、杯状形态（电子显微镜）、表达外泌体标志物蛋白 CD63、磷脂酰丝氨酸（流式细胞术）和 TSG101（免疫印迹），除了表达 CD34(+)细胞谱系标志物蛋白 CD34 外。在体外，CD34(+) 外泌体通过增加内皮细胞活力、增殖和在 Matrigel 上形成管来复制 CD34(+)细胞的血管生成活性。在体内，CD34(+) 外泌体刺激 Matrigel 塞和角膜测定中的血管生成。有趣的是，CD34(+) 细胞而非 CD34(+)细胞耗尽的单核细胞来源的外泌体具有血管生成活性。
我们的数据表明，人 CD34(+) 细胞分泌的外泌体具有独立的体外和体内血管生成活性。CD34(+) 外泌体可能代表祖细胞移植治疗性血管生成的旁分泌作用的重要组成部分。
