PDF(Pubmed)
Abstract：
Postmenopausal osteoporosis results from a pro-resorptive bone environment, which decreases bone mineral density causing increased fracture risk. Bone marrow derived mesenchymal stem/stromal cells (MSCs) secrete factors involved in bone homeostasis, but osteoporosis mediated changes to their secretions remain understudied. Herein, we examined the secretome of MSCs isolated from ovariectomized rats (OVX rMSCs), a model of post-menopausal osteoporosis, as a function of cell-cell interactions. Specifically, we controlled clustering of OVX and SHAM rMSCs by assembling them in granular hydrogels synthesized from poly(ethylene glycol) microgels with average diameters of ∼10, 100, and 200 µm. We directed both the sizes of rMSC clusters (single cells to ∼30 cells/cluster) and the percentages of cells within clusters (∼20-90%) by controlling the scaffold pore dimensions. Large clusters of OVX rMSCs had a pro-resorptive secretory profile, with increased concentrations of Activin A, CXCL1, CX3CL1, MCP-1, TIMP-1, and TNF-ɑ, compared to SHAM rMSCs. As this pro-resorptive bias was only observed in large cell clusters, we characterized the expression of several cadherins, mediators of cell-cell contacts. N-cadherin expression was elevated (∼4-fold) in OVX relative to SHAM rMSCs, in both cell clusters and single cells. Finally, TIMP-1 and MCP-1 secretion was only decreased in large cell clusters of OVX rMSCs when N-cadherin interactions were blocked, highlighting the dependence of OVX rMSC secretion of pro-resorptive cytokines on N-cadherin mediated cell-cell contacts. Further elucidation of the N-cadherin mediated osteoporotic MSC secretome may have implications for developing therapies for postmenopausal osteoporosis. STATEMENT OF SIGNIFICANCE: Postmenopausal osteoporosis is a prevalent bone disorder that affects tens of millions of women worldwide. This disease is characterized by severe bone loss resulting from a pro-resorptive bone marrow environment, where the rates of bone resorption outpace the rates of bone deposition. The paracrine factors secreted by bone marrow MSCs can influence cell types responsible for bone homeostasis, but the osteoporosis-mediated changes to MSC secretory properties remains understudied. In this study, we used PEG-based porous granular scaffolds to study the influence of cell clustering on the secretory properties of osteoporotic MSCs. We observed increased secretion of several pro-resorptive factors by osteoporotic MSCs in large clusters. Further, we explored the dependence of this altered secretion profile on N-cadherin mediated cell-cell contacts.
摘要：
绝经后骨质疏松症是由促进骨吸收的环境引起的，降低骨矿物质密度导致骨折风险增加。骨髓间充质干细胞/基质细胞（MSCs）分泌参与骨稳态的因子，但骨质疏松症介导的分泌物变化仍未得到充分研究。在这里，我们检查了从卵巢切除大鼠分离的MSCs（OVXrMSCs）的分泌组，绝经后骨质疏松症的模型，作为细胞间相互作用的功能。具体来说,我们通过将OVX和SHAMrMSCs组装在平均直径为~10、100和200μm的聚(乙二醇)微凝胶合成的颗粒水凝胶中来控制它们的聚集。我们通过控制支架孔尺寸来指导rMSC簇的大小（单细胞至〜30个细胞/簇）和簇内细胞的百分比（〜20-90％）。OVXrMSCs的大簇具有促吸收分泌谱，随着激活素A浓度的增加，CXCL1,CX3CL1,MCP-1,TIMP-1,TNF-α,与SHAMrMSCs相比。由于这种促吸收偏差仅在大细胞簇中观察到，我们表征了几种钙黏着蛋白的表达，细胞-细胞接触的介质。N-cadherin表达在OVX中相对于SHAMrMSCs升高（~4倍），在细胞簇和单细胞中。最后,当N-cadherin相互作用被阻断时，TIMP-1和MCP-1的分泌仅在OVXrMSCs的大细胞簇中减少，强调OVXrMSC分泌促吸收细胞因子对N-钙黏着蛋白介导的细胞-细胞接触的依赖性。进一步阐明N-钙粘蛋白介导的骨质疏松性MSC分泌组可能对开发绝经后骨质疏松症的疗法具有意义。重要性声明：绝经后骨质疏松症是一种普遍的骨骼疾病，影响全世界数千万女性。这种疾病的特征是由促进骨吸收的骨髓环境导致的严重骨丢失，其中骨吸收的速率超过骨沉积的速率。骨髓间充质干细胞分泌的旁分泌因子可以影响负责骨稳态的细胞类型，但骨质疏松介导的MSC分泌特性变化仍未得到充分研究.在这项研究中,我们使用基于PEG的多孔颗粒支架来研究细胞聚集对骨质疏松MSCs分泌特性的影响。我们观察到大量聚集的骨质疏松性MSCs分泌的几种促吸收因子增加。Further,我们探索了这种改变的分泌谱对N-cadherin介导的细胞间接触的依赖性。
