Assessment of Genetic Stability in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes by Using Droplet Digital PCR.

Unintended genetic modifications that occur during the differentiation and proliferation of human induced pluripotent stem cells (hiPSCs) can lead to tumorigenicity. This is a crucial concern in the development of stem cell-based therapies to ensure the safety and efficacy of the final product. Moreover, conventional genetic stability testing methods are limited by low sensitivity, which is an issue that remains unsolved. In this study, we assessed the genetic stability of hiPSCs and hiPSC-derived cardiomyocytes using various testing methods, including karyotyping, CytoScanHD chip analysis, whole-exome sequencing, and targeted sequencing. Two specific genetic mutations in KMT2C and BCOR were selected from the 17 gene variants identified by whole-exome and targeted sequencing methods, which were validated using droplet digital PCR. The applicability of this approach to stem cell-based therapeutic products was further demonstrated with associated validation according to the International Council for Harmonisation (ICH) guidelines, including specificity, precision, robustness, and limit of detection. Our droplet digital PCR results showed high sensitivity and accuracy for quantitatively detecting gene mutations, whereas conventional qPCR could not avoid false positives. In conclusion, droplet digital PCR is a highly sensitive and precise method for assessing the expression of mutations with tumorigenic potential for the development of stem cell-based therapeutics.

Effect of Xenogeneic Substances on the Glycan Profiles and Electrophysiological Properties of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Background and Objectives: Human induced pluripotent stem cell (hiPSC)-derived cardiomyocyte (CM) hold great promise as a cellular source of CM for cardiac function restoration in ischemic heart disease. However, the use of animal-derived xenogeneic substances during the biomanufacturing of hiPSC-CM can induce inadvertent immune responses or chronic inflammation, followed by tumorigenicity. In this study, we aimed to reveal the effects of xenogeneic substances on the functional properties and potential immunogenicity of hiPSC-CM during differentiation, demonstrating the quality and safety of hiPSC-based cell therapy. Methods and Results: We successfully generated hiPSC-CM in the presence and absence of xenogeneic substances (xeno-containing (XC) and xeno-free (XF) conditions, respectively), and compared their characteristics, including the contractile functions and glycan profiles. Compared to XC-hiPSC-CM, XF-hiPSC-CM showed early onset of myocyte contractile beating and maturation, with a high expression of cardiac lineage-specific genes (ACTC1, TNNT2, and RYR2) by using MEA and RT-qPCR. We quantified N-glycolylneuraminic acid (Neu5Gc), a xenogeneic sialic acid, in hiPSC-CM using an indirect enzyme-linked immunosorbent assay and liquid chromatography-multiple reaction monitoring- mass spectrometry. Neu5Gc was incorporated into the glycans of hiPSC-CM during xeno-containing differentiation, whereas it was barely detected in XF-hiPSC-CM. Conclusions: To the best of our knowledge, this is the first study to show that the electrophysiological function and glycan profiles of hiPSC-CM can be affected by the presence of xenogeneic substances during their differentiation and maturation. To ensure quality control and safety in hiPSC-based cell therapy, xenogeneic substances should be excluded from the biomanufacturing process.

MicroRNA-650 in a copy number-variable region regulates the production of interleukin 6 in human osteosarcoma cells.

Copy number variation is a well-known genetic variation. microRNAs (miRNAs/miRs) are non-coding RNAs that mediate gene expression by regulating target mRNAs. In the present study, copy number deletions encompassing miRNA coding regions were investigated to determine the association between the deletion of miRNA and its phenotypic effects. A total of 38 human miRNAs in copy number variants were identified and miR-650, which is functional in the human osteosarcoma MG-63 cell line, was selected. Overexpression of miR-650 decreased the expression of inhibitor of growth family member 4 (ING4) in the MG-63 cells and increased interleukin (IL)6 transcription, as well as IL6 secretion in IL1B-stimulated cells. Furthermore, miR-650 downregulated the amount of nuclear factor of κ light polypeptide gene enhancer in B cells inhibitor α and increased the transcriptional activity of nuclear factor (NF)κB. Downregulation of ING4 also increased the production of IL6, similar to miR-650 overexpression. Taken together, these data indicate that miR-650 plays a significant role in the production of IL6 by regulating ING4 expression and NFκB signaling in IL1B-stimulated MG-63 osteosarcoma cells.

Identification of differentially-expressed genes by DNA methylation in cervical cancer.

To identify novel cervical cancer-related genes that are regulated by DNA methylation, integrated analyses of genome-wide DNA methylation and RNA expression profiles were performed using the normal and tumor regions of tissues from four patients; two with cervical cancer and two with pre-invasive cancer. The present study identified 19 novel cervical cancer-related genes showing differential RNA expression by DNA methylation. A number of the identified genes were novel cervical cancer-related genes and their differential expression was confirmed in a publicly available database. Among the candidate genes, the epigenetic regulation and expression of three genes, CAMK2N1, ALDH1A3 and PPP1R3C, was validated in HeLa cells treated with a demethylating reagent using methylation-specific polymerase chain reaction (PCR) and quantitative PCR, respectively. From these results, the expression of the CAMK2N1, ALDH1A3 and PPP1R3C genes are were shown to be suppressed in cervical cancers by DNA methylation. These genes may be involved in the progression or initiation of cervical cancer.

Genome-wide copy number variation study reveals KCNIP1 as a modulator of insulin secretion.

Copy number variations (CNVs) have emerged as another important genetic marker in addition to SNP for understanding etiology of complex diseases. In light of this, we performed a genome-wide CNV study to identify type 2 diabetes (T2D)-associated CNV using an array comparative genomic hybridization from 3180 subjects for T2D cases (n=863) and controls (n=2,317). Thus, five CNV regions having a p-value threshold ≤0.05 were identified and evaluated by validation with quantitative PCR and comparison with previously reported CNV regions in the Database of Genomic Variants. Furthermore, we performed a functional experiment to assess the biological significance of a gene encompassing a CNV region. The inhibition of KCNIP1 led to increased insulin secretion in a glucose-dependent manner, but had no effect on insulin gene transcription as well as cell apoptosis. Taken together, these data indicate that KCNIP1 from CNV study might function as a T2D-susceptibility gene whose dysregulation alters insulin production.