Shanghai Institute of Cardiovascular Diseases, Zhongshan Hospital, Fudan University, Shanghai, China.
J Cell Mol Med. 2011 Oct;15(10):2245-61. doi: 10.1111/j.1582-4934.2010.01217.x.
Optimal timing of cell therapy for myocardial infarction (MI) appears during 5 to 14 days after the infarction. However, the potential mechanism requires further investigation. This work aimed to verify the hypothesis that myocardial stiffness within a propitious time frame might provide a most beneficial physical condition for cell lineage specification in favour of cardiac repair. Serum vascular endothelial growth factor (VEGF) levels and myocardial stiffness of MI mice were consecutively detected. Isolated bone marrow mononuclear cells (BMMNCs) were injected into infarction zone at distinct time-points and cardiac function were measured 2 months after infarction. Polyacrylamide gel substrates with varied stiffness were used to mechanically mimic the infarcted myocardium. BMMNCs were plated on the flexible culture substrates under different concentrations of VEGF. Endothelial progenitor lineage commitment of BMMNCs was verified by immunofluorescent technique and flow cytometry. Our results demonstrated that the optimal timing in terms of improvement of cardiac function occurred during 7 to 14 days after MI, which was consistent with maximized capillary density at this time domains, but not with peak VEGF concentration. Percentage of double-positive cells for DiI-labelled acetylated low-density lipoprotein uptake and fluorescein isothiocyanate (FITC)-UEA-1 (ulex europaeus agglutinin I lectin) binding had no significant differences among the tissue-like stiffness in high concentration VEGF. With the decrease of VEGF concentration, the benefit of 42 kPa stiffness, corresponding to infarcted myocardium at days 7 to 14, gradually occurred and peaked when it was removed from culture medium. Likewise, combined expressions of VEGFR2(+) , CD133(+) and CD45(-) remained the highest level on 42 kPa substrate in conditions of lower concentration VEGF. In conclusion, the optimal efficacy of BMMNCs therapy at 7 to 14 days after MI might result from non-VEGF dependent angiogenesis, and myocardial stiffness at this time domains was more suitable for endothelial progenitor lineage specification of BMMNCs. The results here highlight the need for greater attention to mechanical microenvironments in cell culture and cell therapy.
心肌梗死（MI）细胞治疗的最佳时机似乎在梗死发生后 5 至 14 天内。然而，其潜在机制仍需进一步研究。本研究旨在验证如下假说：即在适当的时间范围内，心肌硬度可能为细胞谱系特化提供最有益的物理条件，从而有利于心脏修复。连续检测 MI 小鼠的血清血管内皮生长因子（VEGF）水平和心肌硬度。在不同时间点将分离的骨髓单核细胞（BMMNC）注入梗死区，梗死 2 个月后测量心脏功能。使用不同硬度的聚丙烯酰胺凝胶底物来机械模拟梗死心肌。在不同浓度 VEGF 下，将 BMMNC 接种在柔性培养底物上。通过免疫荧光技术和流式细胞术验证 BMMNC 的内皮祖细胞谱系承诺。我们的结果表明，改善心脏功能的最佳时机发生在 MI 后 7 至 14 天，此时毛细血管密度最大，但 VEGF 浓度并非峰值。DiI 标记的乙酰低密度脂蛋白摄取和异硫氰酸荧光素（FITC）-UEA-1（荆豆凝集素 I 凝集素）结合的双阳性细胞百分比在高浓度 VEGF 下的组织样硬度之间无显著差异。随着 VEGF 浓度的降低，42kPa 硬度的益处逐渐出现，并在培养基中去除时达到峰值，这对应于梗死发生后 7 至 14 天的梗死心肌。同样，在较低浓度 VEGF 的条件下，VEGFR2(+)、CD133(+)和 CD45(-)的联合表达在 42kPa 基质上仍保持最高水平。总之，MI 后 7 至 14 天 BMMNC 治疗的最佳疗效可能源于非 VEGF 依赖性血管生成，而在此时间范围内的心肌硬度更适合 BMMNC 的内皮祖细胞谱系特化。这些结果强调了在细胞培养和细胞治疗中需要更加关注机械微环境。
