Sonic Hedgehog Improves Redifferentiation of Dedifferentiated Chondrocytes for Articular Cartilage Repair

Sonic hedgehog (Shh) is involved in the induction of early cartilaginous differentiation of mesenchymal cells in the limb. We investigated whether Shh could promote redifferentiation of dedifferentiated chondrocytes and have a favorable effect on the regeneration of cartilage. Articular chondrocytes of rats were separated and cultured. The redifferentiation of dedifferentiated chondrocytes transfected with Shh was evaluated using monolayer and pellet culture system. The signaling molecules (Ptc 1, Gli 1 and Sox9) of the hedgehog pathway were investigated. A rat model of articular cartilage defect was used to evaluate cartilage repair after transplantation with dedifferentiated chondrocytes. After Shh gene transfer, the hedgehog pathway was upregulated in dedifferentiated chondrocytes. Real time-PCR and western blot analysis verified the stronger expression of Ptc1, Gli1 and Sox9 in Shh transfected cells. Shh upregulates the Shh signaling pathway and multiple cytokines (bone morphogenetic protein 2 and insulin-like growth factor 1) in dedifferentiated chondrocytes. After transplantation in the joint, histologic analysis of the regenerative tissues revealed that significantly better cartilage repair in rats transplanted with Shh transfected cells. These data suggest that Shh could induce redifferentiation of dedifferentiated chondrocytes through up-regulating Shh signaling pathway, and have considerable therapeutic potential in cartilage repair.

音猬因子（Sonic hedgehog，Shh）参与肢体间充质细胞的早期软骨分化诱导过程。
本研究旨在探讨Shh是否可促进去分化软骨细胞的再分化，并对软骨再生发挥有益作用。
我们分离并培养大鼠关节软骨细胞，采用单层及微团培养体系，对转染Shh的去分化软骨细胞的再分化情况进行评估；同时检测刺猬信号通路（hedgehog pathway）的关键信号分子Ptc1、Gli1及Sox9的表达水平。
我们还采用关节软骨缺损大鼠模型，评估去分化软骨细胞移植后的软骨修复效果。
Shh基因转染后，去分化软骨细胞内的刺猬信号通路被激活上调；实时定量PCR（Real time-PCR）与蛋白质印迹法（Western blot）分析证实，转染Shh的细胞中Ptc1、Gli1及Sox9的表达显著增强。
Shh可上调去分化软骨细胞内的刺猬信号通路及多种细胞因子：骨形态发生蛋白2（bone morphogenetic protein 2）与胰岛素样生长因子1（insulin-like growth factor 1）的表达。
关节腔内移植实验后，对再生组织的组织学分析表明，移植转染Shh细胞的大鼠软骨修复效果显著更优。
上述结果提示，Shh可通过上调刺猬信号通路诱导去分化软骨细胞再分化，在软骨修复领域具备可观的治疗应用潜力。