CD44 和透明质酸促进了小鼠软骨细胞中骨形态发生蛋白 7 信号反应。
CD44 and hyaluronan promote the bone morphogenetic protein 7 signaling response in murine chondrocytes.
机构信息
East Carolina University, Brody School of Medicine, Greenville, North Carolina; Nankai University School of Medicine, Tianjin, China.
出版信息
Arthritis Rheumatol. 2014 Jun;66(6):1547-58. doi: 10.1002/art.38388.
OBJECTIVE
Cell-matrix interactions promote cartilage homeostasis. We previously found that Smad1, the transcriptional modulator of the canonical bone morphogenetic protein 7 (BMP-7) pathway, interacted with the cytoplasmic domain of CD44, the principal hyaluronan receptor on chondrocytes. To elucidate the physiologic function of CD44-Smad1 interactions, as well as the role of hyaluronan, we studied the response of chondrocytes isolated from CD44(-/-) and BALB/c (wild-type [WT]) mice to stimulation with BMP-7.
METHODS
In primary murine chondrocytes, CD44 expression was decreased by small interfering RNA (siRNA) transfection or was enhanced by plasmid transfection. Pericellular hyaluronan was removed by hyaluronidase treatment, or its endogenous synthesis was inhibited. Changes in response to BMP-7 stimulation were evaluated by Western blotting of Smad1 phosphorylation and aggrecan messenger RNA (mRNA) expression.
RESULTS
Chondrocytes from CD44(-/-) mice and WT mice transfected with CD44 siRNA were less responsive than untransfected chondrocytes from WT mice to BMP-7. CD44(-/-) mouse chondrocytes transfected with pCD44 showed increased sensitivity to BMP-7. Significant increases in aggrecan mRNA were observed in WT mouse chondrocytes in response to 10 ng/ml of BMP-7, whereas at least 100 ng/ml of BMP-7 was required for CD44(-/-) mouse chondrocytes. However, in chondrocytes from CD44(-/-) and WT mice, hyaluronidase treatment decreased cellular responses to BMP-7. Treatment of both bovine and murine chondrocytes with 4-methylumbelliferone to reduce the synthesis of endogenous hyaluronan confirmed that hyaluronan promoted BMP-7 signaling.
CONCLUSION
Taken together, these investigations into the mechanisms underlying BMP-7 signaling in chondrocytes revealed that while hyaluronan-dependent pericellular matrix is critical for BMP-7 signaling, the expression of CD44 promotes the cellular response to lower concentrations of BMP-7.
目的
细胞-基质相互作用促进软骨稳态。我们之前发现，经典骨形态发生蛋白 7（BMP-7）途径的转录调节剂 Smad1 与软骨细胞中主要透明质酸受体 CD44 的细胞质结构域相互作用。为了阐明 CD44-Smad1 相互作用的生理功能以及透明质酸的作用，我们研究了从 CD44(-/-)和 BALB/c（野生型[WT]）小鼠分离的软骨细胞对 BMP-7 刺激的反应。
方法
在原代鼠软骨细胞中，通过小干扰 RNA（siRNA）转染降低 CD44 表达，或通过质粒转染增强 CD44 表达。用透明质酸酶处理去除细胞外透明质酸，或抑制其内源性合成。通过 Western blot 检测 Smad1 磷酸化和聚集蛋白信使 RNA（mRNA）表达来评估对 BMP-7 刺激的反应变化。
结果
与 WT 小鼠未转染的软骨细胞相比，CD44(-/-)小鼠的软骨细胞和转染 CD44 siRNA 的 WT 小鼠的软骨细胞对 BMP-7 的反应性较低。转染 pCD44 的 CD44(-/-) 小鼠软骨细胞对 BMP-7 的敏感性增加。WT 小鼠软骨细胞对 10ng/ml 的 BMP-7 反应时，聚集蛋白 mRNA 显著增加，而 CD44(-/-) 小鼠软骨细胞至少需要 100ng/ml 的 BMP-7。然而，在 CD44(-/-)和 WT 小鼠的软骨细胞中，透明质酸酶处理降低了细胞对 BMP-7 的反应。用 4-甲基伞形酮处理牛和鼠软骨细胞以减少内源性透明质酸的合成，证实了透明质酸促进了 BMP-7 信号转导。
结论
综上所述，这些对软骨细胞中 BMP-7 信号转导机制的研究表明，虽然透明质酸依赖性细胞外基质对 BMP-7 信号转导至关重要，但 CD44 的表达促进了细胞对较低浓度 BMP-7 的反应。
Zotero 插件