1 Institute of Tissue Regeneration Engineering (ITREN), Dankook University , Cheonan, South Korea .
Tissue Eng Part A. 2014 Jan;20(1-2):103-14. doi: 10.1089/ten.TEA.2013.0198. Epub 2013 Sep 21.
Three-dimensional matrices that encapsulate and deliver stem cells with defect-tuned formulations are promising for bone tissue engineering. In this study, we designed a novel stem cell delivery system composed of collagen and alginate as the core and shell, respectively. Mesenchymal stem cells (MSCs) were loaded into the collagen solution and then deposited directly into a fibrous structure while simultaneously sheathing with alginate using a newly designed core-shell nozzle. Alginate encapsulation was achieved by the crosslinking within an adjusted calcium-containing solution that effectively preserved the continuous fibrous structure of the inner cell-collagen part. The constructed hydrogel carriers showed a continuous fiber with a diameter of ~700-1000 μm for the core and 200-500 μm for the shell area, which was largely dependent on the alginate concentration (2%-5%) as well as the injection rate (20-80 mL/h). The water uptake capacity of the core-shell carriers was as high as 98%, which could act as a pore channel to supply nutrients and oxygen to the cells. Degradation of the scaffolds showed a weight loss of ~22% at 7 days and ~43% at 14 days, suggesting a possible role as a degradable tissue-engineered construct. The MSCs encapsulated within the collagen core showed excellent viability, exhibiting significant cellular proliferation up to 21 days with levels comparable to those observed in the pure collagen gel matrix used as a control. A live/dead cell assay also confirmed similar percentages of live cells within the core-shell carrier compared to those in the pure collagen gel, suggesting the carrier was cell compatible and was effective for maintaining a cell population. Cells allowed to differentiate under osteogenic conditions expressed high levels of bone-related genes, including osteocalcin, bone sialoprotein, and osteopontin. Further, when the core-shell fibrous carriers were implanted in a rat calvarium defect, the bone healing was significantly improved when the MSCs were encapsulated, and even more so after an osteogenic induction of MSCs before implantation. Based on these results, the newly designed core-shell collagen-alginate fibrous carrier is considered promising to enable the encapsulation of tissue cells and their delivery into damaged target tissues, including bone with defect-tunability for bone tissue engineering.
三维矩阵可以包裹和输送经过配方调整的干细胞，有望用于骨组织工程。在这项研究中，我们设计了一种新型的干细胞输送系统，由胶原蛋白和海藻酸钠分别作为核心和外壳组成。间充质干细胞（MSCs）被加载到胶原蛋白溶液中，然后直接沉积到纤维结构中，同时使用新设计的核壳喷嘴用海藻酸钠包裹。海藻酸钠的包封是通过在调整后的含钙溶液中交联实现的，该溶液有效地保留了内部细胞-胶原蛋白部分的连续纤维结构。构建的水凝胶载体显示出具有约 700-1000μm 直径的核心连续纤维和 200-500μm 直径的外壳区域，这主要取决于海藻酸钠浓度（2%-5%）以及注射速率（20-80mL/h）。核壳载体的吸水率高达 98%，可以作为孔道为细胞提供营养和氧气。支架的降解在第 7 天损失约 22%的重量，在第 14 天损失约 43%的重量，表明其可能作为可降解的组织工程构建物发挥作用。包裹在胶原蛋白核心内的 MSCs 表现出优异的活力，细胞增殖显著，在 21 天内达到与对照用纯胶原蛋白凝胶基质相当的水平。活/死细胞检测也证实了核壳载体内的活细胞百分比与纯胶原蛋白凝胶内的相似，表明载体对细胞具有相容性，并能有效维持细胞群体。在成骨条件下分化的细胞表达高水平的与骨相关的基因，包括骨钙素、骨涎蛋白和骨桥蛋白。此外，当核壳纤维载体被植入大鼠颅骨缺损时，当包裹 MSCs 时，骨愈合得到显著改善，并且在植入前对 MSCs 进行成骨诱导后更是如此。基于这些结果，新设计的核壳胶原蛋白-海藻酸钠纤维载体有望实现组织细胞的封装及其递送到受损靶组织，包括具有缺陷可调性的骨组织工程骨。
