Zorlutuna Pinar, Builles Nicolas, Damour Odile, Elsheikh Ahmed, Hasirci Vasif
METU, BIOMAT, Department of Biological Sciences, Biotechnology Research Unit, Ankara 06531, Turkey.
Biomaterials. 2007 Aug;28(24):3489-96. doi: 10.1016/j.biomaterials.2007.04.013. Epub 2007 Apr 14.
In this paper the mechanical properties of micropatterned polyester films prepared to serve as tissue engineering scaffolds of cornea were examined. Films were prepared by solvent casting of blends of poly(l-lactide-co-d,l-lactide) and poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid), on a micropatterned silicon template. They were seeded with keratocytes or retinal pigment epithelial cells and subjected to tensile testing to assess the contribution of cells and the deposited extra-cellular matrix (ECM) to the mechanical properties of the scaffold. In all the tests, the films used were wet and the cells were not fixed. Cell-free scaffolds showed a gradual deterioration in strength upon incubation in the cell culture medium at 37 degrees C; the deterioration rate was highest in the first week and decreased significantly over the second and third weeks. The ultimate strength of the cell-free scaffolds decreased from 0.99 to 0.42N/mm after 21 days of incubation. Cell seeded scaffolds showed a more complicated mechanical strength profile. Their response was found to depend both on the extent of surface coverage and on the cell type. The results were examined after dividing the data into two groups of lower and higher stiffness. For keratocyte seeded scaffolds, the strength of the high stiffness groups continued to increase as the incubation period increased while the lower stiffness groups did not show a distinct change. For the keratocyte seeded scaffolds, tensile strength increased from 0.65N/mm on Day 7 to 0.73N/mm on Day 21. On the other hand, the scaffolds seeded with retinal pigment epithelial cells showed a gradual deterioration over time in both the higher and lower stiffness groups. For epithelial cell seeded scaffolds this was 0.98N/mm on Day 7 and decreased to 0.77N/mm on Day 21 still an improvement over the unseeded scaffolds. This most probably was a result of a lower rate of ECM secretion in comparison to keratocytes and the newly secreted ECM could not compensate for the influence of scaffold degradation on the mechanical properties. It could, therefore, be concluded that cell seeding plays a positive role in strengthening a tissue engineered construct, and cell type has a significant influence on the extent of this improvement.
本文研究了制备用作角膜组织工程支架的微图案化聚酯薄膜的力学性能。薄膜通过将聚（L-丙交酯-co-D，L-丙交酯）和聚（3-羟基丁酸-co-3-羟基戊酸）的共混物溶剂浇铸在微图案化的硅模板上制备而成。在薄膜上接种角膜细胞或视网膜色素上皮细胞，并进行拉伸测试，以评估细胞和沉积的细胞外基质（ECM）对支架力学性能的贡献。在所有测试中，使用的薄膜是湿润的，细胞未固定。无细胞支架在37℃的细胞培养基中孵育时强度逐渐下降；下降速率在第一周最高，在第二周和第三周显著降低。无细胞支架在孵育21天后的极限强度从0.99N/mm降至0.42N/mm。接种细胞的支架显示出更复杂的机械强度曲线。发现它们的响应既取决于表面覆盖程度，也取决于细胞类型。将数据分为两组较低和较高刚度后对结果进行了研究。对于接种角膜细胞的支架，高刚度组的强度随着孵育期的增加而持续增加，而低刚度组没有明显变化。对于接种角膜细胞的支架，拉伸强度从第7天的0.65N/mm增加到第21天的0.73N/mm。另一方面，接种视网膜色素上皮细胞的支架在高刚度组和低刚度组中均随时间逐渐退化。对于接种上皮细胞的支架，第7天为0.98N/mm，第21天降至0.77N/mm，仍比未接种的支架有所改善。这很可能是由于与角膜细胞相比ECM分泌速率较低，新分泌的ECM无法补偿支架降解对力学性能的影响。因此，可以得出结论，细胞接种在强化组织工程构建体方面发挥积极作用，并且细胞类型对这种改善的程度有显著影响。
