Significance of MEF2C and RUNX3 Regulation for Endochondral Differentiation of Human Mesenchymal Progenitor Cells
Significance of MEF2C and RUNX3 Regulation for Endochondral Differentiation of Human Mesenchymal Progenitor Cells
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DOI：
10.3389/fcell.2020.00081
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发表时间：
2020-03-04
影响因子：
5.5
通讯作者：
Richter, Wiltrud
中科院分区：
文献类型：
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作者：
Dreher, Simon, I;Fischer, Jennifer;Richter, Wiltrud
引导祖细胞在软骨发育与软骨内发育途径之间的发育仍然是软骨新生尚未实现的任务，而人类间充质祖细胞（MPC）软骨发生被认为是更好地理解软骨细胞肥大发育的有价值的模型。转录因子Runx 2、Runx 3和Mef 2c在小鼠发育过程中对软骨细胞肥大起着重要作用，但这些关键的命运决定因子对人MPC的软骨内发育的重要性知之甚少。本研究的目的是阐明MPC软骨形成过程中RUNX 2、RUNX 3和MEF 2C的调控、驱动其表达的途径以及受其调控影响的下游肥大靶点。RUNX 2、RUNX 3和MEF 2C基因表达在MPC的软骨形成过程中受到不同的调节，但在相同条件下分化非肥大关节软骨细胞时，RUNX 2、RUNX 3和MEF 2C基因表达仍然较低且不受调节。RUNX 3和MEF 2C mRNA和蛋白水平与肥大标志物上调平行升高，但令人惊讶的是，RUNX 2基因表达仅呈趋势变化，RUNX 2蛋白仍然检测不到。虽然RUNX 3表达由TGF-β和BMP信号转导驱动，但MEF 2C对WNT-、BMP-和Hedgehog-途径抑制有反应。当肥大减弱时，MEF 2C而不是RUNX 3水平与COL 10A 1、IHH和IBSP基因表达显著相关。在SAOS-2细胞中，IBSP是RUNX 3和MEF 2C的下游靶标，但不是RUNX 2，这强调了RUNX 3和MEF 2C刺激人细胞中成骨标志物表达的能力。总之，RUNX 3和MEF 2C似乎比RUNX 2更重要的人内软骨MPC软骨形成。改变软骨形成速度的途径（FGF、TGF-β、BMP）影响RUNX 2或RUNX 3，而改变肥大的途径（WNT、PTHrP/HH）主要调节MEF 2C。总之，降低MEF 2C水平是将人类软骨新生转向软骨细胞途径的新目标。
Guiding progenitor cell development between chondral versus endochondral pathways is still an unachieved task of cartilage neogenesis, and human mesenchymal progenitor cell (MPC) chondrogenesis is considered as a valuable model to better understand hypertrophic development of chondrocytes. Transcription factors Runx2, Runx3, and Mef2c play prominent roles for chondrocyte hypertrophy during mouse development, but little is known on the importance of these key fate-determining factors for endochondral development of human MPCs. The aim of this study was to unravel the regulation of RUNX2, RUNX3, and MEF2C during MPC chondrogenesis, the pathways driving their expression, and the downstream hypertrophic targets affected by their regulation. RUNX2, RUNX3, and MEF2C gene expression was differentially regulated during chondrogenesis of MPCs, but remained low and unregulated when non-hypertrophic articular chondrocytes were differentiated under the same conditions. RUNX3 and MEF2C mRNA and protein levels rose in parallel to hypertrophic marker upregulation, but surprisingly, RUNX2 gene expression changed only by trend and RUNX2 protein remained undetectable. While RUNX3 expression was driven by TGF-beta and BMP signaling, MEF2C responded to WNT-, BMP-, and Hedgehog-pathway inhibition. MEF2C but not RUNX3 levels correlated significantly with COL10A1, IHH, and IBSP gene expression when hypertrophy was attenuated. IBSP was a downstream target of RUNX3 and MEF2C but not RUNX2 in SAOS-2 cells, underlining the capacity of RUNX3 and MEF2C to stimulate osteogenic marker expression in human cells. Conclusively, RUNX3 and MEF2C appeared more important than RUNX2 for human endochondral MPC chondrogenesis. Pathways altering the speed of chondrogenesis (FGF, TGF-beta, BMP) affected RUNX2 or RUNX3, while pathways changing hypertrophy (WNT, PTHrP/HH) regulated mainly MEF2C. Taken together, reduction of MEF2C levels is a new goal to shift human cartilage neogenesis toward the chondral pathway.