Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland School of Dentistry, Baltimore, MD 21201, USA.
Tissue Eng Part A. 2012 Aug;18(15-16):1583-95. doi: 10.1089/ten.TEA.2011.0604. Epub 2012 May 14.
Stem cell-encapsulating microbeads could be mixed into a paste such as calcium phosphate cement (CPC), where the microbeads could protect the cells from the mixing and injection forces. After being placed, the microbeads could quickly degrade to release the cells throughout the scaffold, while creating macropores. The objectives of this study were to (1) construct alginate-fibrin microbeads encapsulating human umbilical cord mesenchymal stem cells (hUCMSCs) embedded in the surface of novel biofunctionalized CPC and (2) investigate microbead degradation, cell release, and osteodifferentiation on CPC. Hydrogel microbeads were fabricated that encapsulated hUCMSCs at 1×10(6) cells/mL. CPC was biofunctionalized with fibronectin (Fn) and Arg-Gly-Asp (RGD). Four scaffolds were tested: CPC control, CPC mixed with Fn, CPC mixed with RGD, and CPC grafted with RGD. The degradable microbeads released hUCMSCs at 7 days, which attached to CPC. Adding Fn or RGD to CPC greatly improved cell attachment. CPC grafted with RGD showed the fastest cell proliferation, with cell density being ninefold that on CPC control. The released hUCMSCs underwent osteodifferentiation. Alkaline phosphatase, osteocalcin, collagen 1, and runt-related transcription factor 2 (Runx2) gene expression increased by 10 to 30 fold at 7-21 days, compared with day 1. The released cells on CPC synthesized bone minerals, with the mineralization amount at 21 days being two orders of magnitude higher than that at 7 days. In conclusion, alginate-fibrin microbeads embedded in CPC surface were able to quickly release the hUCMSCs that attached to biofunctionalized CPC. Incorporating Fn and RGD into CPC greatly improved cell function, and CPC grafted with RGD had the fastest cell proliferation. The released cells on CPC differentiated into the osteogenic lineage and synthesized bone minerals. The new biofunctionalized CPC with hUCMSC-encapsulating microbeads is promising for bone regeneration applications.
干细胞包埋微球可以混合到糊剂中，如磷酸钙水泥（CPC）中，其中微球可以保护细胞免受混合和注射的影响。放置后，微球可以迅速降解，将细胞释放到整个支架中，同时形成大孔。本研究的目的是（1）构建包埋人脐带间充质干细胞（hUCMSCs）的藻酸盐-纤维蛋白微球，嵌入新型生物功能化 CPC 的表面，（2）研究微球降解、细胞释放和 CPC 上的成骨分化。制备了包封 1×10（6）个细胞/ml hUCMSC 的水凝胶微球。CPC 用纤维连接蛋白（Fn）和精氨酸-甘氨酸-天冬氨酸（RGD）进行生物功能化。测试了四种支架：CPC 对照、CPC 与 Fn 混合、CPC 与 RGD 混合和 RGD 接枝的 CPC。可降解微球在 7 天内释放 hUCMSCs，这些细胞附着在 CPC 上。向 CPC 中添加 Fn 或 RGD 可大大提高细胞附着。RGD 接枝的 CPC 表现出最快的细胞增殖，细胞密度是 CPC 对照的九倍。释放的 hUCMSCs 经历成骨分化。碱性磷酸酶、骨钙素、胶原 1 和 runt 相关转录因子 2（Runx2）基因表达在第 7-21 天增加了 10 到 30 倍，而在第 1 天则增加了 10 到 30 倍。释放到 CPC 上的细胞合成了骨矿物质，21 天时的矿化量比 7 天时高两个数量级。总之，嵌入 CPC 表面的藻酸盐-纤维蛋白微球能够快速释放附着在生物功能化 CPC 上的 hUCMSCs。将 Fn 和 RGD 掺入 CPC 中可极大地提高细胞功能，而 RGD 接枝的 CPC 具有最快的细胞增殖。CPC 上释放的细胞分化为成骨谱系并合成骨矿物质。具有 hUCMSC 包埋微球的新型生物功能化 CPC 有望用于骨再生应用。
