Abstract
We previously established human induced pluripotent stem (iPS) cells in two diabetic patients from different families with the mitochondrial A3243G mutation and isolated isogenic iPS cell clones with either undetectable or high levels of the mutation in both patients. In the present study, we analyzed the mitochondrial functions of two mutation-undetectable and two mutation-high clones in each patient through four methods to assess complex I activity, mitochondrial membrane potential, mitochondrial respiration, and mitochondrial ATP production. In the first patient, complex I activity, mitochondrial respiration, and mitochondrial ATP production were decreased in the mutation-high clones compared with the mutation-undetectable clones, and mitochondrial membrane potential was decreased in a mutation-high clone compared with a mutation-undetectable clone. In the second patient, complex I activity was decreased in one mutation-high clone compared with the other clones. The other parameters showed no differences in any clones. In addition, the complex I activity and mitochondrial respiration of the mutation-undetectable clones from both patients were located in the range of those of iPS cells from healthy subjects. The present study suggests that the mitochondrial function of the mutation-undetectable iPS cell clones obtained from two patients with the A3243G mutation is comparable to the control iPS cells.
Highlights
Like embryonic stem (ES) cells, human induced pluripotent stem cells, which are generated from somatic cells, possess pluripotency in all three germ layers; they are considered promising sources for cell-replacement therapy and useful tools for developing disease models or drug screening[1,2]
The complex I activity of the three induced pluripotent stem (iPS) cell lines (B71, W1217, and TIG10718) generated from healthy subjects and the ES cell line (KhES-119) were compared with that of the mutation-undetectable Mt iPS cell clones (Mt1-1low and Mt2-3low) and the complex I activity was comparable between the mutation-undetectable Mt iPS cell clones and the control pluripotent stem cells (PSCs) (Supplementary Fig. 1, n = 10–15)
The present study shows the following observations: (1) among the Mt1 iPS cell clones, the complex I activity, oxygen consumption rate (OCR) and mitochondrial ATP production were decreased in the mutation-high clones compared with the mutation-undetectable clones
Summary
Like embryonic stem (ES) cells, human induced pluripotent stem (iPS) cells, which are generated from somatic cells, possess pluripotency in all three germ layers; they are considered promising sources for cell-replacement therapy and useful tools for developing disease models or drug screening[1,2]. A major concern about cell replacement therapy is tumorigenicity[4], integration-free methods to generate iPS cells[5], in vivo tumorigenicity tests[6], and precise assessments of genome integrity[3] could prevent tumorigenesis Mitochondria contain their own genomes, known as mitochondrial DNA (mtDNA), and mtDNA mutations induce mitochondrial dysfunction, thereby causing mitochondrial diseases. Several studies have reported that mutation-undetectable iPS cells can be generated in the process of reprograming, probably led by bimodal segregation toward homoplasmy, from patients carrying mtDNA mutations, suggesting a common mechanism for mitochondrial diseases[13,14,15,16]. We analyzed the mitochondrial function of the Mt iPS cell clones, three control iPS cell lines from healthy subjects, and one ES cell line with regard to the following four parameters: complex I activity, mitochondrial membrane potential, oxygen consumption rate (OCR), and cytosolic ATP concentration
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