NUS Graduate School for Integrative Sciences and Engineering (NGS), National University of Singapore , Singapore, Singapore .
Stem Cells Dev. 2013 Sep 1;22(17):2347-55. doi: 10.1089/scd.2012.0415. Epub 2013 May 24.
Pericytes play a crucial role in angiogenesis and vascular maintenance. They can be readily identified in vivo and isolated as CD146(+)CD34(-) cells from various tissues. Whether these and other markers reliably identify pericytes in vitro is unclear. CD146(+)CD34(-) selected cells exhibit multilineage potential. Thus, their perivascular location might represent a stem cell niche. This has spurred assumptions that not only all pericytes are mesenchymal stromal cells (MSCs), but also that all MSCs can act as pericytes. Considering this hypothesis, we developed functional assays by confronting test cells with endothelial cultures based on matrigel assay, spheroid sprouting, and cord formation. We calibrated these assays first with commercial cell lines [CD146(+)CD34(-) placenta-derived pericytes (Pl-Prc), bone marrow (bm)MSCs and fibroblasts]. We then functionally compared the angiogenic abilities of CD146(+)CD34(-)selected bmMSCs with CD146(-) selected bmMSCs from fresh human bm aspirates. We show here that only CD146(+)CD34(-) selected Pl-Prc and CD146(+)CD34(-) selected bmMSCs maintain endothelial tubular networks on matrigel and improve endothelial sprout morphology. CD146(-) selected bmMSCs neither showed these abilities, nor did they attain pericyte function despite progressive CD146 expression once passaged. Thus, cell culture conditions appear to influence expression of this and other reported pericyte markers significantly without correlation to function. The newly developed assays, therefore, promise to close a gap in the in vitro identification of pericytes via function. Indeed, our functional data suggest that pericytes represent a subpopulation of MSCs in bm with a specialized role in vascular biology. However, these functions are not inherent to all MSCs.
周细胞在血管生成和血管维持中起着至关重要的作用。它们可以在体内被轻易识别，并从各种组织中分离为 CD146(+)CD34(-)细胞。然而，这些和其他标记物是否能可靠地识别体外的周细胞尚不清楚。CD146(+)CD34(-)选择的细胞具有多能性。因此，它们的血管周围位置可能代表了一个干细胞龛。这促使人们假设，不仅所有的周细胞都是间充质基质细胞（MSCs），而且所有的 MSCs 都可以作为周细胞发挥作用。考虑到这个假设，我们通过将测试细胞与基于基质胶测定、球体发芽和索形成的内皮细胞培养物进行对抗，开发了功能测定。我们首先用商业细胞系（CD146(+)CD34(-)胎盘来源的周细胞（Pl-Prc）、骨髓（bm）MSCs 和成纤维细胞）校准了这些测定。然后，我们从新鲜的人骨髓抽吸物中功能比较了 CD146(+)CD34(-)选择的 bmMSCs 与 CD146(-)选择的 bmMSCs 的血管生成能力。我们在这里表明，只有 CD146(+)CD34(-)选择的 Pl-Prc 和 CD146(+)CD34(-)选择的 bmMSCs 能够在基质胶上维持内皮管状网络，并改善内皮芽的形态。CD146(-)选择的 bmMSCs 既没有表现出这些能力，也没有获得周细胞功能，尽管在传代后 CD146 的表达逐渐增加。因此，细胞培养条件似乎对这种和其他报道的周细胞标记物的表达有显著影响，而与功能无关。因此，新开发的测定有望通过功能填补体外鉴定周细胞的空白。事实上，我们的功能数据表明，周细胞代表骨髓中 MSC 的一个亚群，在血管生物学中具有特殊作用。然而，这些功能并不是所有 MSCs 所固有的。
