Lofaro Francesco Demetrio, Boraldi Federica, Garcia-Fernandez Maria, Estrella Lara, Valdivielso Pedro, Quaglino Daniela
Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy.
Department of Human Physiology, Biomedical Research Institute of Málaga, University of Malaga, Málaga, Spain.
Front Cell Dev Biol. 2020 Dec 17;8:610266. doi: 10.3389/fcell.2020.610266. eCollection 2020.
(PXE) is a genetic disease considered as a paradigm of ectopic mineralization disorders, being characterized by multisystem clinical manifestations due to progressive calcification of skin, eyes, and the cardiovascular system, resembling an age-related phenotype. Although fibroblasts do not express the pathogenic gene, nevertheless these cells are still under investigation because they regulate connective tissue homeostasis, generating the "arena" where cells and extracellular matrix components can promote pathologic calcification and where activation of pro-osteogenic factors can be associated to pathways involving mitochondrial metabolism. The aim of the present study was to integrate structural and bioenergenetic features to deeply investigate mitochondria from control and from PXE fibroblasts cultured in standard conditions and to explore the role of mitochondria in the development of the PXE fibroblasts' pathologic phenotype. Proteomic, biochemical, and morphological data provide new evidence that in basal culture conditions (1) the protein profile of PXE mitochondria reveals a number of differentially expressed proteins, suggesting changes in redox balance, oxidative phosphorylation, and calcium homeostasis in addition to modified structure and organization, (2) measure of oxygen consumption indicates that the PXE mitochondria have a low ability to cope with a sudden increased need for ATP oxidative phosphorylation, (3) mitochondrial membranes are highly polarized in PXE fibroblasts, and this condition contributes to increased reactive oxygen species levels, (4) ultrastructural alterations in PXE mitochondria are associated with functional changes, and (5) PXE fibroblasts exhibit a more abundant, branched, and interconnected mitochondrial network compared to control cells, indicating that fusion prevail over fission events. In summary, the present study demonstrates that mitochondria are modified in PXE fibroblasts. Since mitochondria are key players in the development of the aging process, fibroblasts cultured from aged individuals or aged are more prone to calcify, and in PXE, calcified tissues remind features of premature aging syndromes; it can be hypothesized that mitochondria represent a common link contributing to the development of ectopic calcification in aging and in diseases. Therefore, ameliorating mitochondrial functions and cell metabolism could open new strategies to positively regulate a number of signaling pathways associated to pathologic calcification.
假性黄色瘤弹性纤维增生症（PXE）是一种遗传性疾病，被视为异位矿化障碍的范例，其特征是由于皮肤、眼睛和心血管系统的进行性钙化而出现多系统临床表现，类似于与年龄相关的表型。尽管成纤维细胞不表达致病基因，但这些细胞仍在研究中，因为它们调节结缔组织稳态，产生细胞和细胞外基质成分可促进病理性钙化的“场所”，并且促骨生成因子的激活可能与涉及线粒体代谢的途径相关。本研究的目的是整合结构和生物能量学特征，深入研究在标准条件下培养的对照和成纤维细胞的线粒体，并探讨线粒体在成纤维细胞病理表型发展中的作用。蛋白质组学、生化和形态学数据提供了新的证据，表明在基础培养条件下：（1）成纤维细胞线粒体的蛋白质谱显示出许多差异表达的蛋白质，这表明除了结构和组织改变外，氧化还原平衡、氧化磷酸化和钙稳态也发生了变化；（2）氧气消耗的测量表明，成纤维细胞线粒体应对ATP氧化磷酸化突然增加需求的能力较低；（3）成纤维细胞线粒体膜高度极化，这种情况导致活性氧水平升高；（4）成纤维细胞线粒体的超微结构改变与功能变化相关；（5）与对照细胞相比，成纤维细胞表现出更丰富、分支更多且相互连接的线粒体网络，表明融合胜过裂变事件。总之，本研究表明成纤维细胞中的线粒体发生了改变。由于线粒体是衰老过程发展的关键因素，从老年个体或老年人培养的成纤维细胞更容易钙化，并且在PXE中，钙化组织具有早衰综合征的特征；可以推测线粒体是导致衰老和疾病中异位钙化发展的共同环节。因此，改善线粒体功能和细胞代谢可能为积极调节与病理性钙化相关的许多信号通路开辟新策略。
