Belinsky Glenn S, Sreekumar Bharath, Andrejecsk Jillian W, Saltzman W Mark, Gong Jingjing, Herzog Raimund I, Lin Samantha, Horsley Valerie, Carpenter Thomas O, Chung Chuhan
Department of Medicine, Yale University School of Medicine, New Haven, Connecticut, USA;
Department of Biomedical Engineering, Yale University, New Haven, Connecticut, USA;
FASEB J. 2016 Aug;30(8):2837-48. doi: 10.1096/fj.201500027R. Epub 2016 Apr 28.
Null mutations in for pigment epithelium-derived factor (PEDF), the protein product of the SERPINF1 gene, are the cause of osteogenesis imperfecta (OI) type VI. The PEDF-knockout (KO) mouse captures crucial elements of the human disease, including diminished bone mineralization and propensity to fracture. Our group and others have demonstrated that PEDF directs human mesenchymal stem cell (hMSC) commitment to the osteoblast lineage and modulates Wnt/β-catenin signaling, a major regulator of bone development; however, the ability of PEDF to restore bone mass in a mouse model of OI type VI has not been determined. In this study, PEDF delivery increased trabecular bone volume/total volume by 52% in 6-mo-old PEDF-KO mice but not in wild-type mice. In young (19-d-old) PEDF-KO mice, PEDF restoration increased bone volume fraction by 35% and enhanced biomechanical parameters of bone plasticity. A Wnt-green fluorescent protein reporter demonstrated dynamic changes in Wnt/β-catenin signaling characterized by early activation and marked suppression during terminal differentiation of hMSCs. Continuous Wnt3a exposure impeded mineralization of hMSCs, whereas the combination of Wnt3a and PEDF potentiated mineralization. Interrogation of the PEDF sequence identified a conserved motif found in other Wnt modulators, such as the dickkopf proteins. Mutation of a single amino acid on a 34-mer PEDF peptide increased mineralization of hMSC cultures compared with the native peptide sequence. These results indicate that PEDF counters Wnt signaling to allow for osteoblast differentiation and provides a mechanistic insight into how the PEDF null state results in OI type VI.-Belinsky, G. S., Sreekumar, B., Andrejecsk, J. W., Saltzman, W. M., Gong, J., Herzog, R. I., Lin, S., Horsley, V., Carpenter, T. O., Chung, C. Pigment epithelium-derived factor restoration increases bone mass and improves bone plasticity in a model of osteogenesis imperfecta type VI via Wnt3a blockade.
丝氨酸蛋白酶抑制剂家族F成员1（SERPINF1）基因的蛋白产物色素上皮衍生因子（PEDF）的无效突变是VI型成骨不全（OI）的病因。PEDF基因敲除（KO）小鼠体现了人类疾病的关键要素，包括骨矿化减少和骨折倾向。我们团队及其他研究者已证明，PEDF引导人间充质干细胞（hMSC）向成骨细胞谱系分化，并调节Wnt/β-连环蛋白信号通路，这是骨发育的主要调节因子；然而，PEDF在VI型OI小鼠模型中恢复骨量的能力尚未确定。在本研究中，给6月龄的PEDF-KO小鼠递送PEDF使小梁骨体积/总体积增加了52%，而野生型小鼠未出现此现象。在年轻（19日龄）的PEDF-KO小鼠中，恢复PEDF使骨体积分数增加了35%，并增强了骨可塑性的生物力学参数。一个Wnt绿色荧光蛋白报告基因显示了Wnt/β-连环蛋白信号通路的动态变化，其特征是在hMSC终末分化过程中早期激活和显著抑制。持续暴露于Wnt3a会阻碍hMSC的矿化，而Wnt3a和PEDF联合使用则会增强矿化。对PEDF序列的研究确定了一个在其他Wnt调节剂（如dickkopf蛋白）中发现的保守基序。与天然肽序列相比，34肽PEDF上单个氨基酸的突变增加了hMSC培养物的矿化。这些结果表明，PEDF对抗Wnt信号通路以促进成骨细胞分化，并为PEDF缺失状态导致VI型OI的机制提供了深入了解。-贝林斯基，G.S.，斯里库马尔，B.，安德烈耶茨克，J.W.，萨尔茨曼，W.M.，龚，J.，赫尔佐格，R.I.，林，S.，霍斯利，V.，卡彭特，T.O.，钟，C.色素上皮衍生因子的恢复通过阻断Wnt3a增加了VI型成骨不全模型中的骨量并改善了骨可塑性
