Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742, USA.
Acta Biomater. 2011 Mar;7(3):1249-64. doi: 10.1016/j.actbio.2010.11.007. Epub 2010 Nov 11.
Incorporation of hydroxyapatite (HA) within a degradable polymeric scaffold may provide a favorable synthetic microenvironment that more closely mimics natural bone tissue physiology. Both incorporation of HA nanoparticles and alterations of the paracrine cell-cell signaling distance may affect the intercellular signaling mechanism and facilitate enhanced osteogenic signal expression among the implanted cell population. In this study we investigate the effect of the incorporation of HA nanoparticles into poly(propylene fumarate) (PPF) scaffolds on the surface properties of composite scaffolds and early osteogenic growth factor gene expression in relation to initial cell seeding density. The results of surface characterization indicated that HA addition improved the surface properties of PPF/HA composite scaffolds by increasing the roughness, hydrophilicity, protein adsorption, and initial cell attachment. Rat bone marrow stromal cells (BMSCs), which were CD34-, CD45-, CD29+, and CD90+, were cultured on three-dimensional (3-D) macroporous PPF/HA scaffolds at two different initial cell seeding densities (0.33 and 1.00 million cells per scaffold) for 8 days. The results demonstrated that endogenous osteogenic signal expression profiles, including bone morphogenetic protein-2, fibroblast growth factor-2, and transforming growth factor-β1, as well as the transcriptional factor Runx2, were affected by both HA amount and initial cell seeding density. Up-regulated expression of osteogenic growth factor genes was related to subsequent osteoblastic differentiation of rat BMSCs on 3-D scaffolds, as characterized by alkaline phosphatase activity, osteocalcin mRNA expression, and calcium deposition. Thus, the PPF/HA composite scaffold construction parameters, including amount of HA incorporated and initial cell seeding density, may be utilized to induce the osteoblastic differentiation of transplanted rat BMSCs.
将羟基磷灰石 (HA) 掺入可降解聚合物支架中可能提供一种有利的合成微环境，更接近模拟天然骨组织生理学。HA 纳米粒子的掺入和旁分泌细胞-细胞信号距离的改变都可能影响细胞间信号机制，并促进植入细胞群体中增强的成骨信号表达。在这项研究中，我们研究了将 HA 纳米粒子掺入聚（反丁烯二酸）（PPF）支架中对复合支架表面性能和早期成骨生长因子基因表达的影响，与初始细胞接种密度有关。表面特性的结果表明，HA 的加入通过增加粗糙度、亲水性、蛋白质吸附和初始细胞附着来改善 PPF/HA 复合材料支架的表面性能。CD34-、CD45-、CD29+和 CD90+的大鼠骨髓基质细胞（BMSCs）在两种不同的初始细胞接种密度（每个支架 0.33 和 1.00 百万个细胞）下在三维（3-D）大孔 PPF/HA 支架上培养 8 天。结果表明，内源性成骨信号表达谱，包括骨形态发生蛋白-2、成纤维细胞生长因子-2 和转化生长因子-β1，以及转录因子 Runx2，受到 HA 量和初始细胞接种密度的影响。成骨生长因子基因的上调表达与大鼠 BMSCs 在 3-D 支架上随后的成骨细胞分化有关，其特征是碱性磷酸酶活性、骨钙素 mRNA 表达和钙沉积。因此，包括掺入的 HA 量和初始细胞接种密度在内的 PPF/HA 复合支架构建参数可用于诱导移植大鼠 BMSCs 的成骨细胞分化。
