Biophotonics LaboratoryDepartment of Electrical EngineeringUniversity of Wisconsin-Milwaukee Milwaukee WI 53201 USA.
Department of Pathology and Laboratory MedicineMedical College of Wisconsin Milwaukee WI 53226 USA.
IEEE J Transl Eng Health Med. 2021 Aug 16;9:1800407. doi: 10.1109/JTEHM.2021.3104966. eCollection 2021.
Mitochondrial [Formula: see text]-oxidation of fatty acids is the primary energy source for the heart and carried out by Hydroxy Acyl-CoA Dehydrogenase (HADH) encoded trifunctional protein. Mutations in the genes encoding mitochondrial proteins result in functionally defective protein complexes that contribute to energy deficiencies, excessive reactive oxygen species (ROS) production, and accumulation of damaged mitochondria. We hypothesize that a dramatic alternation in redox state and associated mitochondrial dysfunction is the underlying cause of Fatty Acid Oxidation (FAO) deficiency mutant, resulting in heart failure. Mitochondrial co-enzymes, NADH and FAD, are autofluorescent metabolic indices of cells when imaged, yield a quantitative assessment of the cells' redox status and, in turn, that of the tissue and organ.
We utilized an optical cryo-imager to quantitively evaluate the three-dimensional distribution of mitochondrial redox state in newborn rats' hearts and kidneys. Redox ratio (RR) assessment shows that mitochondrial dysfunction is extreme and could contribute to severe heart problems and eventual heart failure in the mutants.
Three-dimensional redox ratio (NADH/FAD) rendering, and the volumetric mean value calculations confirmed significantly decreased cardiac RR in mutants by 31.90% and 12.32%, in renal mitochondrial RR compared to wild-type control. Further, histological assessment of newborn heart myocardial tissue indicated no significant difference in myocardial tissue architecture in both control and severe (HADHA) conditions.
These results demonstrate that optical imaging can accurately estimate the redox state changes in newborn rat organs. It is also apparent that the FAO mutant's heart tissue with a low redox ratio is probably more vulnerable to cumulative damages than kidneys and fails prematurely, contributing to sudden death.
脂肪酸的线粒体 [Formula: see text]-氧化是心脏的主要能量来源，由编码三功能蛋白的羟酰基辅酶 A 脱氢酶 (HADH) 进行。编码线粒体蛋白的基因突变导致功能缺陷的蛋白复合物，导致能量不足、过量活性氧 (ROS) 产生和受损线粒体积累。我们假设氧化还原状态的剧烈改变和相关的线粒体功能障碍是导致脂肪酸氧化 (FAO) 缺陷突变体的根本原因，导致心力衰竭。线粒体辅酶 NADH 和 FAD 是细胞的自发荧光代谢指标，在成像时可对细胞的氧化还原状态进行定量评估，并进而对组织和器官的氧化还原状态进行评估。
我们利用光学冷冻成像仪定量评估新生大鼠心脏和肾脏中线粒体氧化还原状态的三维分布。氧化还原比 (RR) 评估表明，线粒体功能障碍非常严重，可能导致突变体严重的心脏问题和最终心力衰竭。
三维氧化还原比 (NADH/FAD) 渲染和体积平均值计算证实，与野生型对照相比，突变体心脏的 RR 降低了 31.90%，肾脏的 RR 降低了 12.32%。此外，对新生心脏心肌组织的组织学评估表明，在控制和严重 (HADHA) 条件下，心肌组织结构没有明显差异。
这些结果表明，光学成像可以准确估计新生大鼠器官的氧化还原状态变化。显然，氧化还原比低的 FAO 突变体心脏组织可能比肾脏更容易受到累积损伤，并过早衰竭，导致突然死亡。
