目的以血小板内皮细胞黏附分子-1(Platelet endothelial cell adhesion molecule-1,PECAM-1)为标志,去除小鼠胚胎干细胞(Embryonic stem cells,ESCs)中残留未分化的细胞,以去除其致瘤性,为ESCs在研究中的安全应用提供思路。方法将小鼠R1胚胎干细胞株在撤去白血病抑制因子的培养基中悬浮培养6 d,体外自发分化形成类胚体,消化打散后,以PECAM-1为标志进行磁珠分选,得到阳性与阴性细胞群体,分别以2×106个/点注射入裸鼠背部皮下,6~8周后观察畸胎瘤形成情况,组织学分析瘤体构成。结果裸鼠背部成瘤结果显示,PECAM-1+细胞群注射8个点中7个成瘤,成瘤率87.5%;而PECAM-1-细胞群注射8个点中1个成瘤,成瘤率12.5%。PECAM-1+细胞群与PECAM-1-细胞群成瘤率具有统计学差异(P=0.01)。结论应用PECAM-1可去除体外分化过程中的残留未分化ESCs,并去除其致瘤性。

Objective To prevent teratoma formation by removal of the residual undifferentiated cells from differentiated mouse embryonic stem cells （mESCs） based on PECAM-1 expression, to hopefully promote the safe use of ESCs-based treatment in future. Methods Mouse R1 ESCs were cultured in suspension to form embryoid bodies （EBs） in the absence of leukemia inhibitory factor for 6 days. EBs were then digested into single cells and sorted by magnetic activated cell sorting （MACS） based on PECAM-1 expression. Total of 2×10^6 PECAM-1^＋ and PECAM-1^- cells were injected subcutaneously into nude mice respectively. Teratoma formation was measured after 6-8 weeks. Results Seven out of 8 injected points formed teratoma in the PECAM-1^＋ cells after 8 weeks of injection, with a tumor formation rate of 87.5%. While only 1 out of 8 injected points formed teratoma in the PECAM-1^- cells, with a tumor formation rate of 12.5%. A significantly difference was observed between PECAM-1 positive and negative cells （P=0.01）. Conclusion PECAM-1 is a specific marker for residual cells, which could be utilized to remove residual undifferentiated ESCs from in vitro differentiated ESCs, and eventually solve the tumorigenicity problem of ESCs.