Tissue Engineering Research Group, Dept. of Anatomy, Royal College of Surgeons in Ireland (RCSI), Dublin, Ireland; Trinity Centre for Bioengineering, Trinity College Dublin (TCD), Dublin 2, Ireland; Advanced Materials and Bioengineering Research (AMBER) Centre, RCSI & TCD, Ireland.
Stem Cells. 2013 Nov;31(11):2420-31. doi: 10.1002/stem.1482.
Skeletogenesis is initiated during fetal development and persists through adult life as either a remodeling process in response to homeostatic regulation or as a regenerative process in response to physical injury. Mesenchymal stem cells (MSCs) play a crucial role providing progenitor cells from which osteoblasts, bone matrix forming cells are differentiated. The mechanical environment plays an important role in regulating stem cell differentiation into osteoblasts, however, the mechanisms by which MSCs respond to mechanical stimuli are yet to be fully elucidated. To increase understanding of MSC mechanotransuction and osteogenic differentiation, this study aimed to identify novel, mechanically augmented genes and pathways with pro-osteogenic functionality. Using collagen glycoaminoglycan scaffolds as mimics of native extracellular matrix, to create a 3D environment more representative of that found in bone, MSC-seeded constructs were mechanically stimulated in a flow-perfusion bioreactor. Global gene expression profiling techniques were used to identify potential candidates warranting further investigation. Of these, placental growth factor (PGF) was selected and expression levels were shown to strongly correlate to both the magnitude and duration of mechanical stimulation. We demonstrated that PGF gene expression was modulated through an actin polymerization-mediated mechanism. The functional role of PGF in modulating MSC osteogenic differentiation was interrogated, and we showed a concentration-dependent response whereby low concentrations exhibited the strongest pro-osteogenic effect. Furthermore, pre-osteoclast migration and differentiation, as well as endothelial cell tubule formation also maintained concentration-dependent responses to PGF, suggesting a potential role for PGF in bone resorption and angiogenesis, processes key to bone remodeling and fracture repair.
成骨发生始于胎儿发育时期，并在成年后持续存在，既可以作为对体内平衡调节的重塑过程，也可以作为对物理损伤的再生过程。间充质干细胞（MSCs）在提供祖细胞方面发挥着至关重要的作用，这些祖细胞分化为成骨细胞和骨基质形成细胞。机械环境在调节干细胞向成骨细胞分化方面起着重要作用，然而，MSCs 如何响应机械刺激的机制尚未完全阐明。为了增加对 MSC 机械转导和成骨分化的理解，本研究旨在确定具有促成骨功能的新的、机械增强的基因和途径。本研究使用胶原糖胺聚糖支架作为天然细胞外基质的模拟物，构建更具代表性的 3D 环境，将 MSC 接种构建体在流动灌注生物反应器中进行机械刺激。使用全基因表达谱技术来鉴定有进一步研究价值的潜在候选基因。在这些候选基因中，胎盘生长因子（PGF）被选中，其表达水平与机械刺激的幅度和持续时间强烈相关。我们证明 PGF 基因表达受到肌动蛋白聚合介导的机制调节。研究了 PGF 在调节 MSC 成骨分化中的功能作用，我们发现了一种浓度依赖性反应，其中低浓度表现出最强的促成骨作用。此外，破骨细胞前迁移和分化以及内皮细胞管形成也对 PGF 表现出浓度依赖性反应，这表明 PGF 在骨吸收和血管生成中可能具有潜在作用，这些过程是骨重塑和骨折修复的关键。
