Musculoskeletal Integrity Program, Hospital for Special Surgery, New York, NY 10021, United States.
Int J Biochem Cell Biol. 2013 Aug;45(8):1813-20. doi: 10.1016/j.biocel.2013.05.034. Epub 2013 Jun 4.
Cysteine (C)-X-C chemokine receptor-4 (CXCR4) is the primary transmembrane receptor for stromal cell-derived factor-1 (SDF-1). We previously reported in mouse or human bone marrow-derived mesenchymal stromal stem cells (BMSCs) that deleting or antagonizing CXCR4 inhibits bone morphogenetic protein-2 (BMP2)-induced osteogenic differentiation. The goal of this study was to determine whether CXCR4-deficiency in BMSCs is an age-related effect in association with impaired osteogenic differentiation potency of aged BMSCs. Using BMSCs derived from C57BL/6J wild type mice at ages ranging from 3 to 23 months old, we detected decreased CXCR4 mRNA and protein expression as well as SDF-1 secretion with advancing aging. Moreover, CXCR4-deficient BMSCs from elderly vs. young mice exhibited impaired osteogenic differentiation in response to BMP2 stimulation or when cultured in dexamethasone (Dex)-containing osteogenic medium, evidenced by decreased alkaline phosphatase activity, osteocalcin synthesis, and calcium deposition (markers for immature and mature osteoblasts). Mechanistically, impaired BMP2- or Dex-osteoinduction in BMSCs of elderly mice was mediated by inhibited phosphorylation of intracellular R-Smads and Erk1/2 or Erk1/2 and p38 proteins, and decreased Runx2 and Osx expression (osteogenesis "master" regulators) were also detected. Furthermore, adenovirus-mediated repair of CXCR4 expression in BMSCs of elderly mice restored their osteogenic differentiation potentials to both BMP2 treatment and osteogenic medium. Collectively, our results demonstrate for the first time that CXCR4 expression in mouse BMSCs declines with aging, and this CXCR4-deficiency impairs osteogenic differentiation potency of aged BMSCs. These findings provide novel insights into mechanisms underlying age-related changes in BMSC-osteogenesis, and will potentiate CXCR4 as a therapeutic target to improve BMSC-based bone repair and regeneration in broad orthopedic situations.
半胱氨酸 (C)-X-C 趋化因子受体-4 (CXCR4) 是基质细胞衍生因子-1 (SDF-1) 的主要跨膜受体。我们之前在小鼠或人骨髓间充质基质干细胞 (BMSCs) 中报道，删除或拮抗 CXCR4 会抑制骨形态发生蛋白-2 (BMP2) 诱导的成骨分化。本研究的目的是确定 BMSCs 中 CXCR4 的缺失是否与老年 BMSCs 成骨分化能力受损有关，是一种与年龄相关的效应。使用源自 3 至 23 个月大的 C57BL/6J 野生型小鼠的 BMSCs，我们检测到随着年龄的增长，CXCR4 mRNA 和蛋白表达以及 SDF-1 分泌减少。此外，与年轻小鼠相比，来自老年小鼠的 CXCR4 缺陷型 BMSCs 在 BMP2 刺激或在含有地塞米松 (Dex) 的成骨培养基中培养时，成骨分化受损，表现为碱性磷酸酶活性、骨钙素合成和钙沉积减少（不成熟和成熟成骨细胞的标志物）。在机制上，老年小鼠 BMSCs 中 BMP2 或 Dex 成骨诱导受损是通过抑制细胞内 R-Smads 和 Erk1/2 或 Erk1/2 和 p38 蛋白的磷酸化以及 Runx2 和 Osx 表达（成骨“主”调节因子）来介导的。此外，在老年小鼠的 BMSCs 中，腺病毒介导的 CXCR4 表达修复恢复了它们对 BMP2 处理和成骨培养基的成骨分化潜能。总之，我们的研究结果首次表明，小鼠 BMSCs 中的 CXCR4 表达随年龄增长而下降，这种 CXCR4 缺失会损害老年 BMSCs 的成骨分化能力。这些发现为 BMSC 成骨过程中与年龄相关变化的机制提供了新的见解，并将 CXCR4 作为一种治疗靶点，以改善广泛骨科情况下基于 BMSC 的骨修复和再生。
