Giles Erica M, Godbout Charles, Chi Wendy, Glick Michael A, Lin Tony, Li Ru, Schemitsch Emil H, Nauth Aaron
Keenan Research Centre for Biomedical Science, St. Michael's Hospital, University of Toronto, 209 Victoria Street, Toronto, ON, M5B 1T8, Canada.
Department of Surgery, Western University, 268 Grosvenor Street, Room E3-116, London, ON, N6A 4V2, Canada.
Int Orthop. 2017 Nov;41(11):2337-2343. doi: 10.1007/s00264-017-3613-0. Epub 2017 Aug 24.
Treating fracture nonunion with endothelial progenitor cells (EPCs) is a promising approach. Nevertheless, the effect of different EPC-related cell populations remains unclear. In this study, we compared the therapeutic potential of early (E-EPCs) and late EPCs (L-EPCs).
Male Fischer 344 rats were used for cell isolation and in vivo experiments. Bone marrow-derived E-EPCs and L-EPCs were kept in culture for seven to ten days and four weeks, respectively. For each treatment group, we seeded one million cells on a gelatin scaffold before implantation in a segmental defect created in a rat femur; control animals received a cell-free scaffold. Bone healing was monitored via radiographs for up to ten weeks after surgery. In vitro, secretion of vascular endothelial growth factor (VEGF) and bone morphogenetic protein (BMP)-2 was quantified by ELISA for both cell populations. Tube formation assays were also performed.
Final radiographs showed complete (four out of five rats) or partial (one out of five rats) union with E-EPC treatment. In contrast, complete healing was achieved in only one of five animals after L-EPC implantation, while control treatment resulted in nonunion in all animals. In vitro, E-EPCs released more VEGF, but less BMP-2 than L-EPCs. In addition, L-EPCs formed longer and more mature tubules on basement membrane matrix than E-EPCs. However, co-culture with primary osteoblasts stimulated tubulogenesis of E-EPCs while inhibiting that of L-EPCs.
We demonstrated that bone marrow-derived E-EPCs are a better alternative than L-EPCs for treatment of nonunion. We hypothesize that the expression profile of E-EPCs and their adaptation to the local environment contribute to superior bone healing.
用内皮祖细胞（EPCs）治疗骨折不愈合是一种很有前景的方法。然而，不同EPC相关细胞群的作用仍不清楚。在本研究中，我们比较了早期EPCs（E-EPCs）和晚期EPCs（L-EPCs）的治疗潜力。
雄性Fischer 344大鼠用于细胞分离和体内实验。骨髓来源的E-EPCs和L-EPCs分别在培养中保存7至10天和4周。对于每个治疗组，我们在植入大鼠股骨节段性缺损前，将100万个细胞接种在明胶支架上；对照动物接受无细胞支架。术后通过X线片监测骨愈合情况，最长持续10周。在体外，通过酶联免疫吸附测定法（ELISA）对两种细胞群的血管内皮生长因子（VEGF）和骨形态发生蛋白（BMP）-2分泌进行定量。还进行了管形成试验。
最终X线片显示，E-EPC治疗组有完全愈合（5只大鼠中的4只）或部分愈合（5只大鼠中的1只）。相比之下，L-EPC植入后5只动物中只有1只实现了完全愈合，而对照治疗导致所有动物骨折不愈合。在体外，E-EPCs释放的VEGF比L-EPCs多，但BMP-2比L-EPCs少。此外，L-EPCs在基底膜基质上形成的小管比E-EPCs更长、更成熟。然而，与原代成骨细胞共培养可刺激E-EPCs的管形成，同时抑制L-EPCs的管形成。
我们证明，骨髓来源的E-EPCs在治疗骨折不愈合方面比L-EPCs是更好的选择。我们推测，E-EPCs的表达谱及其对局部环境的适应性有助于实现更好的骨愈合。
