Department of Endodontics, Prosthodontics, and Operative Dentistry, Biomaterials and Tissue Engineering Division, University of Maryland Dental School, Baltimore, Maryland 21201, USA.
Tissue Eng Part A. 2011 Nov;17(21-22):2603-13. doi: 10.1089/ten.tea.2011.0048. Epub 2011 Jul 11.
Calcium phosphate cement (CPC) can fill complex-shaped bone defects and set in situ to form a scaffold with intimate adaptation to neighboring bone. The objectives of this study were to determine (1) the effects of fiber length and alginate microbead volume fraction on CPC mechanical properties, and (2) the effect of cell seeding density of human umbilical cord mesenchymal stem cells (hUCMSCs) on their proliferation and osteodifferentiation on CPC. Adding microbeads to CPC degraded the strength. However, increasing the fiber length improved the mechanical properties. Strength and elastic modulus of CPC-microbead-fiber scaffold matched those reported for cancellous bone. When the cell seeding density was increased from 50k to 300k, the cell viability, osteodifferentiation, and bone mineral synthesis also increased. When the seeding density was further increased to 500k, the osteodifferentiation and mineralization decreased. Hence, the 300k seeding density was optimal for CPC-microbead-fiber under the specified conditions. At day 8, alkaline phosphatase (ALP) gene expression of hUCMSCs with seeding density of 300k was threefold the ALP at 150k, and 200-fold the ALP at 50k. At day 14, osteocalcin and runt-related transcription factor 2 with cell seeding density of 300k was fourfold those at 50k. At day 14, mineralization by hUCMSCs at seeding density of 300k was 5-fold the mineralization at 150k, and 25-fold that at 50k. In conclusion, the effect of stem cell seeding density on CPC was determined for the first time. At low cell densities, cell viability and mineralization increased with seeding density. However, a higher seeding density was not necessarily better, and an optimal seeding density on CPC resulted in the best osteodifferentiation and mineralization. The stem cell-seeded CPC-fiber scaffold with excellent osteodifferentiation and mineralization is promising for orthopedic and craniofacial applications.
磷酸钙水泥 (CPC) 可填充复杂形状的骨缺损，并原位凝固形成与邻近骨紧密适应的支架。本研究的目的是确定：(1)纤维长度和藻酸钠微球体积分数对 CPC 力学性能的影响，以及 (2)人脐带间充质干细胞 (hUCMSCs) 的细胞接种密度对 CPC 上细胞增殖和成骨分化的影响。向 CPC 中添加微球会降低其强度。然而，增加纤维长度可改善其力学性能。CPC-微球-纤维支架的强度和弹性模量与松质骨报道的值相匹配。当细胞接种密度从 50k 增加到 300k 时，细胞活力、成骨分化和骨矿合成也随之增加。当接种密度进一步增加到 500k 时，成骨分化和矿化减少。因此，在所规定的条件下，CPC-微球-纤维的 300k 接种密度最佳。在第 8 天，接种密度为 300k 的 hUCMSCs 的碱性磷酸酶 (ALP) 基因表达是接种密度为 150k 的 3 倍，是接种密度为 50k 的 200 倍。在第 14 天，接种密度为 300k 的 hUCMSCs 的骨钙素和 runt 相关转录因子 2 是接种密度为 50k 的 4 倍。在第 14 天，接种密度为 300k 的 hUCMSCs 的矿化是接种密度为 150k 的 5 倍，是接种密度为 50k 的 25 倍。总之，首次确定了干细胞接种密度对 CPC 的影响。在低细胞密度下，细胞活力和矿化随接种密度的增加而增加。然而，较高的接种密度不一定更好，CPC 上的最佳接种密度可导致最佳的成骨分化和矿化。具有优异成骨分化和矿化的干细胞接种 CPC 纤维支架有望用于骨科和颅面应用。
