Division of Vascular Medicine, Swiss Cardiovascular Center, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse, CH-3010 Bern, Switzerland.
Atherosclerosis. 2010 Jul;211(1):103-9. doi: 10.1016/j.atherosclerosis.2010.02.022. Epub 2010 Feb 24.
Endothelial progenitor cells (EPC) play a fundamental role in tissue regeneration and vascular repair. Current research suggests that EPC are more resistant to oxidative stress as compared to differentiated endothelial cells. Here we hypothesized that EPC not only possess the ability to protect themselves against oxidative stress but also confer this protection upon differentiated endothelial cells by release of paracrine factors. To test this hypothesis, HUVEC incubated with conditioned medium obtained from early EPC cultures (EPC-CM) were exposed to H2O2 to assess the accumulation of intracellular ROS, extent of apoptosis and endothelial cell functionality. Under oxidative stress conditions HUVEC treated with EPC-CM exhibited substantially lower levels of intracellular oxidative stress (0.2+/-0.02 vs. 0.4+/-0.03 relative fluorescence units, p<0.05) compared to control medium. Moreover, the incubation with EPC-CM elevated the expression level of antioxidant enzymes in HUVEC (catalase: 2.6+/-0.4; copper/zinc superoxide dismutase (Cu/ZnSOD): 1.6+/-0.1; manganese superoxide dismutase (MnSOD): 1.4+/-0.1-fold increase compared to control, all p<0.05). Furthermore, EPC-CM had the distinct potential to reverse the functional impairment of HUVEC as measured by their capability to form tubular structures in vitro. Finally, incubation of HUVEC with EPC-CM resulted in a significant reduction of apoptosis (0.34+/-0.01 vs. 1.52+/-0.12 relative fluorescence units, p<0.01) accompanied by an increased expression ratio of the anti/pro-apoptotic factors Bcl-2/Bax to 2.9+/-0.7-fold (compared to control, p<0.05). Most importantly, neutralization of selected cytokines such as VEGF, HGF, IL-8 and MMP-9 did not significantly reverse the cyto-protective effect of EPC-CM (p>0.05), suggesting that soluble factors secreted by EPC, possibly via broad synergistic actions, exert strong cyto-protective properties on differentiated endothelium through modulation of intracellular antioxidant defensive mechanisms and pro-survival signals.
内皮祖细胞（EPC）在组织再生和血管修复中起着至关重要的作用。目前的研究表明，EPC 比分化的内皮细胞更能抵抗氧化应激。在这里，我们假设 EPC 不仅具有保护自身免受氧化应激的能力，而且还可以通过释放旁分泌因子将这种保护作用赋予分化的内皮细胞。为了验证这一假设，我们将 HUVEC 与早期 EPC 培养物获得的条件培养基（EPC-CM）孵育，然后用 H2O2 处理这些细胞，以评估细胞内 ROS 的积累、细胞凋亡的程度和内皮细胞的功能。在氧化应激条件下，与对照培养基相比，用 EPC-CM 处理的 HUVEC 细胞内氧化应激水平显著降低（0.2+/-0.02 与 0.4+/-0.03 相对荧光单位，p<0.05）。此外，EPC-CM 孵育可提高 HUVEC 中抗氧化酶的表达水平（过氧化氢酶：2.6+/-0.4；铜/锌超氧化物歧化酶（Cu/ZnSOD）：1.6+/-0.1；锰超氧化物歧化酶（MnSOD）：与对照组相比，增加了 1.4+/-0.1 倍，均 p<0.05）。此外，EPC-CM 具有明显逆转 HUVEC 功能障碍的潜力，这可通过其在体外形成管状结构的能力来衡量。最后，EPC-CM 孵育可显著降低 HUVEC 的细胞凋亡（0.34+/-0.01 与 1.52+/-0.12 相对荧光单位，p<0.01），同时增加抗/促凋亡因子 Bcl-2/Bax 的表达比值至 2.9+/-0.7 倍（与对照组相比，p<0.05）。最重要的是，中和选定的细胞因子（如 VEGF、HGF、IL-8 和 MMP-9）并不能显著逆转 EPC-CM 的细胞保护作用（p>0.05），这表明 EPC 分泌的可溶性因子可能通过广泛的协同作用，通过调节细胞内抗氧化防御机制和生存信号，对分化的内皮细胞发挥强大的细胞保护作用。
