Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama 35294-2182, United States.
ACS Nano. 2011 Dec 27;5(12):9463-79. doi: 10.1021/nn203247m. Epub 2011 Nov 17.
Formation of the native bone extracellular matrix (ECM) provides an attractive template for bone tissue engineering. The structural support and biological complexity of bone ECM are provided within a composite microenvironment that consists of an organic fibrous network reinforced by inorganic hydroxyapatite (HA) nanoparticles. Recreating this biphasic assembly, a bone ECM analogous scaffold comprising self-assembling peptide amphiphile (PA) nanofibers and interspersed HA nanoparticles was investigated. PAs were endowed with biomolecular ligand signaling using a synthetically inscribed peptide sequence (i.e., RGDS) and integrated with HA nanoparticles to form a biphasic nanomatrix hydrogel. It was hypothesized the biphasic hydrogel would induce osteogenic differentiation of human mesenchymal stem cells (hMSCs) and improve bone healing as mediated by RGDS ligand signaling within PA nanofibers and embedded HA mineralization source. Viscoelastic stability of the biphasic PA hydrogels was evaluated with different weight concentrations of HA for improved gelation. After demonstrating initial viability, long-term cellularity and osteoinduction of encapsulated hMSCs in different PA hydrogels were studied in vitro. Temporal progression of osteogenic maturation was assessed by gene expression of key markers. A preliminary animal study demonstrated bone healing capacity of the biphasic PA nanomatrix under physiological conditions using a critical size femoral defect rat model. The combination of RGDS ligand signaling and HA nanoparticles within the biphasic PA nanomatrix hydrogel demonstrated the most effective osteoinduction and comparative bone healing response. Therefore, the biphasic PA nanomatrix establishes a well-organized scaffold with increased similarity to natural bone ECM with the prospect for improved bone tissue regeneration.
天然骨细胞外基质 (ECM) 的形成为骨组织工程提供了一个有吸引力的模板。骨 ECM 的结构支撑和生物复杂性存在于一个复合微环境中，该微环境由有机纤维网络增强的无机羟磷灰石 (HA) 纳米颗粒组成。为了重现这种两相组装，研究了一种由自组装肽两亲物 (PA) 纳米纤维和穿插的 HA 纳米颗粒组成的具有骨 ECM 类似支架的两相组装。通过使用合成刻写的肽序列（即 RGDS）赋予 PA 生物分子配体信号，并与 HA 纳米颗粒整合形成两相纳米基质水凝胶，从而赋予 PA 生物分子配体信号。假设两相水凝胶将通过 RGDS 配体信号在 PA 纳米纤维内诱导人间充质干细胞 (hMSC) 的成骨分化，并通过嵌入的 HA 矿化源改善骨愈合。通过不同重量浓度的 HA 来评估两相 PA 水凝胶的粘弹性稳定性，以改善凝胶化。在证明初始活力后，研究了不同 PA 水凝胶中封装的 hMSC 的长期细胞活力和成骨诱导。通过关键标记物的基因表达评估成骨成熟的时间进展。初步动物研究表明，在生理条件下，使用临界尺寸股骨缺损大鼠模型，两相 PA 纳米基质具有骨愈合能力。在两相 PA 纳米基质水凝胶中，RGDS 配体信号和 HA 纳米颗粒的组合表现出最有效的成骨诱导和可比的骨愈合反应。因此，两相 PA 纳米基质建立了一个具有更高相似性的组织有序支架天然骨 ECM，具有改善骨组织再生的前景。
