Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309-0424, USA.
Acta Biomater. 2011 Nov;7(11):3829-40. doi: 10.1016/j.actbio.2011.06.031. Epub 2011 Jun 26.
Biochemical and biomechanical cues are known to influence the differentiation of stem cells. Biomechanical cues arise from cellular interactions with their surrounding matrix and from applied forces. This study investigates the role of biomechanical cues in chondrogenic and osteogenic differentiation of human marrow stromal cells (hMSC) when encapsulated in synthetic hydrogels. Poly(ethylene glycol) hydrogels were fabricated with tethered cell adhesion moieties, RGD. Cell-laden hydrogels were subjected to 4 h daily intermittent dynamic compressive loading (0.3Hz, 15% amplitude strain) for up to 14 days and the cell response evaluated by gene expression and matrix deposition for chondrogenic and osteogenic markers. The three-dimensional hydrogel supported chondrogenesis and osteogenesis under free swelling conditions, as shown by the up-regulation of cartilage-related markers (SOX9, Col II, Col X, and aggrecan) and staining for type II collagen and aggrecan and osteogenically by up-regulation of ALP and staining for type I collagen and for mineralization. However, under dynamic loading the expression of cartilage-related markers SOX9, Col II, Col X, and aggrecan were down-regulated, along with reduced aggrecan staining and no positive staining for type II collagen. Additionally, the bone-related markers RUNX2, Col I, and ALP were down-regulated and positive staining for type I collagen and mineralization was reduced. In conclusion, the selected loading regime appears to have an inhibitory effect on chondrogenesis and osteogenesis of hMSC encapsulated in PEG-RGD hydrogels after 14 days in culture, potentially due to overloading of the differentiating hMSC before sufficient pericellular matrix is produced and/or due to large strains, particularly for osteogenically differentiating hMSC.
生物化学和生物力学线索已知会影响干细胞的分化。生物力学线索源于细胞与其周围基质的相互作用以及所施加的力。本研究探讨了在合成水凝胶中包封时，生物力学线索在人骨髓基质细胞（hMSC）的软骨和成骨分化中的作用。通过附着细胞黏附部分（RGD）制造聚乙二醇水凝胶。将细胞负载的水凝胶每天接受 4 小时的间歇动态压缩加载（0.3Hz，15%振幅应变），持续 14 天，并通过基因表达和软骨和成骨标志物的基质沉积来评估细胞反应。三维水凝胶在自由膨胀条件下支持软骨和成骨，如软骨相关标志物（SOX9、Col II、Col X 和聚集蛋白聚糖）的上调以及 II 型胶原和聚集蛋白聚糖的染色所示，以及通过碱性磷酸酶（ALP）的上调和 I 型胶原的染色以及矿化而成骨。然而，在动态加载下，软骨相关标志物 SOX9、Col II、Col X 和聚集蛋白聚糖的表达下调，聚集蛋白聚糖染色减少，且 II 型胶原无阳性染色。此外，骨相关标志物 runt 相关转录因子 2（RUNX2）、Col I 和 ALP 的表达下调，I 型胶原和矿化的阳性染色减少。总之，所选加载方案似乎对培养 14 天后包封在 PEG-RGD 水凝胶中的 hMSC 的软骨和成骨具有抑制作用，这可能是由于分化的 hMSC 在产生足够的细胞外基质之前受到过度负荷，和/或由于大应变，特别是对于成骨分化的 hMSC。
