Department of Internal Medicine, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam-si, 13496, Republic of Korea.
Department of Orthopaedic Surgery, CHA Bundang Medical Center, CHA University School of Medicine, 59 Yatap-ro, Bundang-gu, Seongnam-si, 13496, South Korea.
Stem Cell Res Ther. 2021 Nov 25;12(1):589. doi: 10.1186/s13287-021-02656-4.
PTEN-induced kinase 1 (PINK1) is a serine/threonine-protein kinase in mitochondria that is critical for mitochondrial quality control. PINK1 triggers mitophagy, a selective autophagy of mitochondria, and is involved in mitochondrial regeneration. Although increments of mitochondrial biogenesis and activity are known to be crucial during differentiation, data regarding the specific role of PINK1 in osteogenic maturation and bone remodeling are limited.
We adopted an ovariectomy model in female wildtype and Pink1 mice. Ovariectomized mice were analyzed using micro-CT, H&E staining, Masson's trichrome staining. RT-PCR, western blot, immunofluorescence, alkaline phosphatase, and alizarin red staining were performed to assess the expression of PINK1 and osteogenic markers in silencing of PINK1 MC3T3-E1 cells. Clinical relevance of PINK1 expression levels was determined via qRT-PCR analysis in normal and osteoporosis patients.
A significant decrease in bone mass and collagen deposition was observed in the femurs of Pink1 mice after ovariectomy. Ex vivo, differentiation of osteoblasts was inhibited upon Pink1 downregulation, accompanied by impaired mitochondrial homeostasis, increased mitochondrial reactive oxygen species production, and defects in mitochondrial calcium handling. Furthermore, PINK1 expression was reduced in bones from patients with osteoporosis, which supports the practical role of PINK1 in human bone disease.
In this study, we demonstrated that activation of PINK1 is a requisite in osteoblasts during differentiation, which is related to mitochondrial quality control and low reactive oxygen species production. Enhancing PINK1 activity might be a possible treatment target in bone diseases as it can promote a healthy pool of functional mitochondria in osteoblasts.
PTEN 诱导的激酶 1（PINK1）是一种在线粒体中起关键作用的丝氨酸/苏氨酸蛋白激酶，对线粒体质量控制至关重要。PINK1 触发线粒体自噬，即线粒体的选择性自噬，并参与线粒体再生。虽然已知线粒体生物发生和活性的增加在分化过程中至关重要，但关于 PINK1 在成骨成熟和骨重塑中的具体作用的数据有限。
我们在雌性野生型和 Pink1 小鼠中采用卵巢切除术模型。通过 micro-CT、H&E 染色、Masson 三色染色分析卵巢切除术小鼠。进行 RT-PCR、western blot、免疫荧光、碱性磷酸酶和茜素红染色，以评估沉默 PINK1 的 MC3T3-E1 细胞中 PINK1 和成骨标志物的表达。通过 qRT-PCR 分析在正常和骨质疏松症患者中确定 PINK1 表达水平的临床相关性。
Pink1 小鼠卵巢切除后股骨骨量和胶原沉积明显减少。在体外，Pink1 下调抑制成骨细胞分化，伴随着线粒体稳态受损、线粒体活性氧产生增加和线粒体钙处理缺陷。此外，骨质疏松症患者骨骼中 PINK1 的表达减少，这支持了 PINK1 在人类骨骼疾病中的实际作用。
在这项研究中，我们证明了 PINK1 在成骨细胞分化过程中的激活是必需的，这与线粒体质量控制和低活性氧产生有关。增强 PINK1 活性可能是骨骼疾病的一种潜在治疗靶点，因为它可以促进成骨细胞中健康的功能性线粒体池。
