Research Center for Experimental Orthopaedics, Heidelberg University Hospital, Heidelberg, Germany.
Clinic for Orthopaedics and Trauma Surgery, Heidelberg University Hospital, Heidelberg, Germany.
Cell Mol Life Sci. 2019 Oct;76(19):3875-3889. doi: 10.1007/s00018-019-03099-0. Epub 2019 Apr 12.
Re-directing mesenchymal stromal cell (MSC) chondrogenesis towards a non-hypertrophic articular chondrocyte-(AC)-like phenotype is important for improving articular cartilage neogenesis to enhance clinical cartilage repair strategies. This study is the first to demonstrate that high levels of non-canonical WNT5A followed by WNT11 and LEF1 discriminated MSC chondrogenesis from AC re-differentiation. Moreover, β-catenin seemed incompletely silenced in differentiating MSCs, which altogether suggested a role for WNT signaling in hypertrophic MSC differentiation. WNT inhibition with the small molecule IWP-2 supported MSC chondrogenesis according to elevated proteoglycan deposition and reduced the characteristic upregulation of BMP4, BMP7 and their target ID1, as well as IHH and its target GLI1 observed during endochondral differentiation. Along with the pro-hypertrophic transcription factor MEF2C, multiple hypertrophic downstream targets including IBSP and alkaline phosphatase activity were reduced by IWP-2, demonstrating that WNT activity drives BMP and hedgehog upregulation, and MSC hypertrophy. WNT inhibition almost matched the strong anti-hypertrophic capacity of pulsed parathyroid hormone-related protein application, and both outperformed suppression of BMP signaling with dorsomorphin, which also reduced cartilage matrix deposition. Yet, hypertrophic marker expression under IWP-2 remained above AC level, and in vivo mineralization and ectopic bone formation were reduced but not eliminated. Overall, the strong anti-hypertrophic effects of IWP-2 involved inhibition but not silencing of pro-hypertrophic BMP and IHH pathways, and more advanced silencing of WNT activity as well as combined application of IHH or BMP antagonists should next be considered to install articular cartilage neogenesis from human MSCs.
重定向间充质基质细胞（MSC）向非肥大性关节软骨细胞（AC）样表型的软骨生成对于增强临床软骨修复策略中的关节软骨新生至关重要。这项研究首次表明，高水平的非经典 WNT5A 随后是 WNT11 和 LEF1 将 MSC 软骨生成与 AC 再分化区分开来。此外，在分化的 MSC 中β-连环蛋白似乎没有完全沉默，这表明 WNT 信号在 MSC 肥大分化中起作用。小分子 IWP-2 的 WNT 抑制作用支持 MSC 软骨生成，表现为糖胺聚糖沉积增加，BMP4、BMP7 及其靶基因 ID1 以及 IHH 和其靶基因 GLI1 的特征性上调减少，这些都是在软骨内分化过程中观察到的。与促肥大转录因子 MEF2C 一起，包括 IBSP 和碱性磷酸酶活性在内的多个肥大下游靶基因被 IWP-2 减少，表明 WNT 活性驱动 BMP 和 hedgehog 的上调以及 MSC 的肥大。WNT 抑制几乎与脉冲甲状旁腺激素相关蛋白应用的强抗肥大能力相匹配，并且优于用 Dorsomorphin 抑制 BMP 信号，后者也减少了软骨基质沉积。然而，在 IWP-2 下，肥大标志物的表达仍高于 AC 水平，体内矿化和异位骨形成减少但未消除。总体而言，IWP-2 的强抗肥大作用涉及对促肥大 BMP 和 IHH 途径的抑制而不是沉默，并且应进一步考虑更先进的 WNT 活性沉默以及 IHH 或 BMP 拮抗剂的联合应用，以从人 MSC 中安装关节软骨新生。
