Angiogenic Cell Therapy by Bone Marrow-Derived Monocyte-lineage Stem Cells

外周血(PB)来源的CD14~+单核细胞可转分化为内皮细胞(EC)系细胞，并有助于新生血管形成。我们研究了骨髓(BM)或外周血来源的CD34^-/CD14^+细胞是否参与了颈动脉球囊损伤后的再内皮化。人骨髓来源的CD34^-/CD14^+单核细胞系(BM-MLCs)，而不是外周血来源的CD34^-CD14^+单核细胞，表达与成熟EC相同的EC特异性标志物(Tie2，CD31，VE-cadherin，endoglin)。当BM-MLCs与血管内皮生长因子共同培养时，造血标志物显著减少，并诱导出新的EC特异性标志物(Flk和CD34)。将骨髓间充质干细胞移植到球囊损伤的裸鼠动脉内。BM-MLCs只有在体内或体外被MCP-1激活后，才能与损伤的内皮细胞黏附，失去造血标志物而分化为EC样细胞，并抑制新生内膜的增殖。外周血CD34^-/CD14^+单核细胞未观察到这种MCP依赖的黏附。再生的内皮细胞呈鹅卵石状，阻止染料渗出，诱导NO依赖的血管松弛。与PB来源的单核细胞相比，BM-MLCs在层流条件下对HUVEC的基础黏附活性和β-1-整合素的表达(基础形态和活性形态)显著增加。MCP-1通过激活β-1-整合素构象，显著增强BM-MLCs对HUVEC的黏附活性(2.8倍)。因此，骨髓间充质干细胞可以作为内皮祖细胞，以单核细胞趋化蛋白-1依赖的方式与受损内皮细胞黏附，导致内皮再内皮化，进而抑制内膜增生。这将为单核细胞趋化蛋白-1介导的生物学作用以及使用骨髓细胞治疗的血管再生策略打开一扇新的窗口。

Peripheral blood(PB)-derived CD14^+ monocytes were shown to trans-differentiate into endothelial cell(EC)-lineage cells and contribute to neovascularization. We investigated whether bone marrow(BM)- or PB-derived CD34^-/CD14^+ cells are involved in reendothelialization after carotid balloon injury. Human BM-derived CD34^-/CD14^+ monocyte-lineage cells (BM-MLCs), but not PB-derived CD34^-CD14^+ monocytes, expressed EC-specific markers (Tie2, CD31, VE-cadherin, Endoglin) to an extent identical to mature EC. When BM-MLCs were cultured with VEGF, hematopoietic markers were drastically decreased and new EC-specific markers (Flk and CD34) were induced. BM-MLCs were intra-arterially transplanted into balloon-injured arteries of athymic nude rats. Only when BM-MLCs were activated by MCP-1 in vivo or in vitro, they adhered onto injured endothelium, differentiated into EC-like cells by losing hematopoietic markers and inhibited neointimal hyperplasia. Such MCP-dependent adhesion was not observed in PB-derived CD34^-/CD14^+ monocytes. Regenerated endothelium exhibited cobble-stone appearance, blocked extravasation of dye and induced NO-dependent vasorelaxation. Basal adhesive activities on HUVEC under laminar flow and beta-1-integrin expression (basal and active forms) were significantly increased in BM-MLCs compared with PB-derived monocytes. MCP-1 markedly enhanced adhesive activity of BM-MLCs (2.8 fold) on HUVEC by activating beta-1-integrin conformation. Thus, BM-MLCs can function as EC progenitors and acquire the ability to adhere on injured endothelium in a MCP-1-dependent manner, leading to reendothelialization followed by inhibition of intimal hyperplasia. This will open a novel window to MCP-1-mediated biological actions as well as vascular regeneration strategies using BM cell therapy.