Center for Craniofacial Stem Cell Research and Regeneration, Department of Orthodontics, Peking University School and Hospital of Stomatology, National Engineering Laboratory for Digital and Material Technology of Stomatology, Beijing Key Laboratory of Digital Stomatology , Beijing 100081, P. R. China.
ACS Appl Mater Interfaces. 2016 Jun 29;8(25):15958-66. doi: 10.1021/acsami.6b04951. Epub 2016 Jun 17.
The interplay between stem cells and their extracellular microenvironment is of critical importance to the stem cell-based therapeutics in regenerative medicine. Mineralized collagen is the main component of bone extracellular matrix, but the effect of interfacial properties of mineralized collagen on subsequent cellular behaviors is unclear. This study examined the role of surface chemistry of nanoscale mineralized collagen on human periodontal ligament stem cell (hPDLSC) fate decisions. The intrafibrillarly mineralized collagen (IMC), fabricated by a biomimetic bottom-up approach, showed a bonelike hierarchy with nanohydroxyapatites (HAs) periodically embedded within fibrils. The infrared spectrum of the IMC showed the presence of phosphate, carbonate, amide I and II bands; and infrared mapping displayed uniform and higher spatial distribution of mineralization in the IMC. However, the distribution of the phosphate group differed far from that of the amide I group in the extrafibrillarly mineralized collagen (EMC), in which flowerlike HA clusters randomly depositing around the surface of the fibrils. Moreover, a large quantity of extrafibrillar HAs covered up the C═O stretch and N-H in-plane bend, resulting in substantial reduction of amide I and II bands. Cell experiments demonstrated that the hPDLSCs seeded on the IMC exhibited a highly branched, osteoblast-like polygonal shape with extended pseudopodia and thick stress fiber formation; while cells on the EMC displayed a spindle shape with less branch points and thin actin fibril formation. Furthermore, the biocompatibility of EMC was much lower than that of IMC. Interestingly, even without osteogenic induction, mRNA levels of major osteogenic differentiation genes were highly expressed in the IMC during cultivation time. These data suggest that the IMC with a similar nanotopography and surface chemistry to natural mineralized collagen directs hPDLSCs toward osteoblast differentiation, providing a promising scaffold in bone tissue regeneration.
干细胞及其细胞外微环境的相互作用对再生医学中的基于干细胞的治疗至关重要。矿化胶原是骨细胞外基质的主要成分，但矿化胶原的界面特性对随后的细胞行为的影响尚不清楚。本研究探讨了纳米矿化胶原表面化学对人牙周膜干细胞（hPDLSC）命运决定的作用。通过仿生自下而上的方法制备的纤维内矿化胶原（IMC）具有类骨的层次结构，其中周期性地嵌入纳米羟基磷灰石（HAs）。IMC 的红外光谱显示存在磷酸盐、碳酸盐、酰胺 I 和 II 带；红外图谱显示矿化在 IMC 中具有均匀且更高的空间分布。然而，在纤维外矿化胶原（EMC）中，矿化磷酸盐的分布与纤维外酰胺 I 组的分布差异很大，其中花状 HA 簇随机沉积在纤维表面周围。此外，大量的纤维外 HAs 覆盖了 C═O 伸展和 N-H 面内弯曲，导致酰胺 I 和 II 带的大幅度减少。细胞实验表明，接种在 IMC 上的 hPDLSCs 表现出高度分支的、成骨细胞样的多边形形状，具有延伸的伪足和厚的应力纤维形成；而在 EMC 上的细胞则呈梭形，分支点较少，肌动蛋白纤维形成较薄。此外，EMC 的生物相容性远低于 IMC。有趣的是，即使没有成骨诱导，在培养过程中，IMC 中主要成骨分化基因的 mRNA 水平也高度表达。这些数据表明，具有类似于天然矿化胶原的纳米形貌和表面化学的 IMC 可引导 hPDLSCs 向成骨细胞分化，为骨组织再生提供了一种有前途的支架。
