Shen He, Lin Hang, Sun Aaron X, Song Saijie, Zhang Zhijun, Dai Jianwu, Tuan Rocky S
Center for Cellular and Molecular Engineering, Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA 15219, USA.
J Mater Chem B. 2018 Feb 14;6(6):908-917. doi: 10.1039/c7tb02172k. Epub 2018 Jan 23.
Graphene-based nanomaterials have been applied as biomaterials to enhance stem cell adhesion, growth and differentiation by serving as nanocarriers for growth factors or other small molecules. However, the direct effect of graphene oxide (GO) itself on stem cells, in the absence of exogenous differentiation inductive factors, has not been tested. In this study, we loaded GO nanosheets and human bone marrow-derived mesenchymal stem cells (hBMSC) into a photopolymerizable poly-d,l-lactic acid/polyethylene glycol (PDLLA) hydrogel, a robust chondrosupportive scaffold recently developed in our laboratory, and assessed hBMSC differentiation along the chondrogenic lineage without supplemental chondroinductive factors. We first examined the effect of GO incorporation on the mechanical properties of constructs, and observed that the GO-containing constructs (GO/PDLLA) exhibited enhanced compressive modulus in a GO concentration dependent manner. hBMSCs cultured in GO/PDLLA maintained high cell viability (>95%), indicating minimal cytotoxicity of GO. Importantly, compared to those encapsulated in PDLLA hydrogel, hBMSCs within GO/PDLLA showed significantly higher level of gene expression of the cartilage matrix genes, aggrecan and collagen type II, and produced more cartilage matrix. In addition, the pro-chondrogenesis effect of GO increased with increasing GO concentration. Immunohistochemical results suggested that GO-enhanced hBMSC chondrogenesis was correlated with enriched sequestration of insulin, a necessary supplement known to have pro-chondrogenesis effects on hBMSC. Taken together, these findings demonstrate the utility of using GO to improve the mechanical properties and chondrogenic differentiation state of MSC-laden, engineered hydrogel constructs, without the use of exogenous growth factors, thus representing a potentially promising, biologics-free approach for cartilage tissue engineering.
基于石墨烯的纳米材料已被用作生物材料，通过充当生长因子或其他小分子的纳米载体来增强干细胞的黏附、生长和分化。然而，在没有外源性分化诱导因子的情况下，氧化石墨烯（GO）本身对干细胞的直接影响尚未得到测试。在本研究中，我们将GO纳米片和人骨髓间充质干细胞（hBMSC）加载到一种可光聚合的聚-d，l-乳酸/聚乙二醇（PDLLA）水凝胶中，这是我们实验室最近开发的一种强大的软骨支持支架，并评估了在没有补充软骨诱导因子的情况下hBMSC沿软骨形成谱系的分化情况。我们首先研究了GO掺入对构建体力学性能的影响，观察到含GO的构建体（GO/PDLLA）以GO浓度依赖性方式表现出增强的压缩模量。在GO/PDLLA中培养的hBMSC保持高细胞活力（>95%），表明GO的细胞毒性最小。重要的是，与封装在PDLLA水凝胶中的hBMSC相比，GO/PDLLA中的hBMSC显示出软骨基质基因聚集蛋白聚糖和II型胶原蛋白的基因表达水平显著更高，并产生了更多的软骨基质。此外，GO的促软骨形成作用随着GO浓度的增加而增强。免疫组织化学结果表明，GO增强的hBMSC软骨形成与胰岛素的富集螯合相关，胰岛素是一种已知对hBMSC具有促软骨形成作用的必要补充剂。综上所述，这些发现证明了使用GO来改善负载MSC的工程水凝胶构建体的力学性能和软骨形成分化状态的效用，而无需使用外源性生长因子，因此代表了一种潜在的、无生物制剂的软骨组织工程方法。
