Department of Orthopaedics, Affiliated Hospital of Qingdao University, Qingdao, China.
Department of Anesthesia, Affiliated Hospital of Qingdao University, Qingdao, China.
Exp Cell Res. 2020 Apr 15;389(2):111930. doi: 10.1016/j.yexcr.2020.111930. Epub 2020 Feb 27.
Tissue inhibitor of metalloproteinase 1 (TIMP1) has various biological activities including the regulation of cell growth and differentiation. However, its role in bone homeostasis and remodeling remains poorly understood. In this study, we investigate the effects of TIMP1 on osteoblast and osteoclast activity at both cellular and molecular level using siRNA-mediated knockdown technique. Our results show that knockdown of TIMP1 stimulates proliferation and survival, but decreases apoptosis in osteoblastic MC3T3-E1 cells, suggesting that TIMP1 inhibits cell growth. TIMP1 also dampens differentiation of committed osteoblasts, as well as osteoblastogenesis of bone marrow-derived mesenchymal stem cells (BMSCs). We further show that the modulation of TIMP1 on osteoblast activity is independent of its MMP inhibition. Importantly, we uncover that TIMP1 suppresses osteoblast growth and differentiation by targeting the AKT pathway, and this is associated with TIMP1-mediated induction of PTEN via its binding to the cell surface receptor CD44. Therefore, our results highlight a novel TIMP1/CD44/PTEN/AKT signaling nexus that functions as a suppressor of osteoblast activity. Moreover, we show that TIMP1 also inhibits osteoclast differentiation in osteoclast precursor RAW 264.7 cells by targeting the AKT. In conclusion, our results demonstrate that TIMP1 can act as a suppressor of growth and differentiation of osteoblasts and differentiation of osteoclasts through the negative regulation of the AKT pathway. We propose that TIMP1 may serve as a potential target for low bone mass-related skeletal diseases, such as osteoporosis.
金属蛋白酶组织抑制剂 1（TIMP1）具有多种生物学活性，包括调节细胞生长和分化。然而，其在骨稳态和重塑中的作用仍知之甚少。在这项研究中，我们使用 siRNA 介导的敲低技术研究了 TIMP1 在成骨细胞和破骨细胞活性方面的细胞和分子水平的作用。我们的结果表明，TIMP1 的敲低可刺激成骨细胞 MC3T3-E1 细胞的增殖和存活，但减少其凋亡，表明 TIMP1 抑制细胞生长。TIMP1 还抑制了成骨细胞的分化，以及骨髓间充质干细胞（BMSCs）的成骨细胞形成。我们进一步表明，TIMP1 对成骨细胞活性的调节与其 MMP 抑制作用无关。重要的是，我们发现 TIMP1 通过靶向 AKT 通路抑制成骨细胞的生长和分化，这与 TIMP1 通过与其细胞表面受体 CD44 结合诱导 PTEN 有关。因此，我们的结果强调了一种新型的 TIMP1/CD44/PTEN/AKT 信号轴，作为成骨细胞活性的抑制因子。此外，我们还表明 TIMP1 通过靶向 AKT 也抑制破骨细胞前体细胞 RAW 264.7 细胞的分化。总之，我们的研究结果表明，TIMP1 可以通过负调控 AKT 通路作为成骨细胞生长和分化以及破骨细胞分化的抑制剂。我们提出，TIMP1 可能成为与低骨量相关骨骼疾病（如骨质疏松症）相关的潜在治疗靶点。
