Current methods and challenges in the comprehensive characterization of human pluripotent stem cells

Homogeneous Differentiation of Functional Hepatocytes from Human Induced Pluripotent Stem Cells

Hepatocyte-like cells (HLCs) generated from human induced pluripotent stem cells (iPSCs) could provide an unlimited source of liver cells for regenerative medicine, disease modeling, drug screening, and toxicology studies. Here we describe a stepwise improved protocol that enables highly efficient, homogeneous, and reproducible differentiation of human iPSCs into functional hepatocytes through controlling all three stages of hepatocyte differentiation, starting from a single cell (non-colony) culture of iPSCs, through homogeneous definitive endoderm induction and highly efficient hepatic specification, and finally arriving at matured HLCs. The final population of cells exhibits morphology closely resembling that of primary human hepatocytes, and expresses specific hepatic markers as evidenced by immunocytochemical staining. More importantly, these HLCs demonstrate key functional characteristics of mature hepatocytes, including major serum protein (e.g., albumin, fibronectin, and alpha-1 antitrypsin) secretion, urea synthesis, glycogen storage, and inducible cytochrome P450 activity.

Rapid and Highly Efficient Isolation and Purification of Human Induced Pluripotent Stem Cells

Human induced pluripotent stem cells (iPSCs) hold great promise for biomedical applications. However, establishment of new iPSC lines still presents many challenges. Here we describe a simple yet highly efficient two-step protocol for the isolation and purification of human iPSC lines. The first step adapts iPSCs to single cell culture and passaging, promoting survival and self-renewal; the second step enables the isolation and purification of bona fide iPSCs from a mixed population using column-based positive selection of cells expressing pluripotency markers such as TRA-1-60. Both steps utilize commercially available reagents. Using this protocol, iPSCs can be purified from cell preparations containing differentiated or unreprogrammed cells, or even be isolated directly from reprogramming vessels. The protocol could be adopted for high throughput isolation and expansion of iPSC lines and facilitate the widespread use of iPSCs in future applications.

Generation and comprehensive characterization of induced pluripotent stem cells for translational research

Induced pluripotent stem cells (iPSCs) hold immense potential in disease modeling, drug discovery and regenerative medicine. Despite advances in reprogramming methods, generation of clinical-grade iPSCs remains a challenge. Reported here is the first off-the-shelf reprogramming kit, CTS CytoTune-iPS 2.1, specifically designed for clinical and translational research. Workflow gaps were identified, and methods developed were used to consistently generate iPSC from multiple cell types. Resulting clones were subjected to characterization that included confirmation of pluripotency, preservation of genomic integrity and authentication of cell banks via an array of molecular methods including high resolution microarray and next-generation sequencing. Development of integrated xeno-free workflows combined with comprehensive characterization offers generation of high-quality iPSCs that are suited for clinical and translational research.

Detailed Characterization of Human Induced Pluripotent Stem Cells Manufactured for Therapeutic Applications

We have recently described manufacturing of human induced pluripotent stem cells (iPSC) master cell banks (MCB) generated by a clinically compliant process using cord blood as a starting material (Baghbaderani et al. in Stem Cell Reports, 5(4), 647-659, 2015). In this manuscript, we describe the detailed characterization of the two iPSC clones generated using this process, including whole genome sequencing (WGS), microarray, and comparative genomic hybridization (aCGH) single nucleotide polymorphism (SNP) analysis. We compare their profiles with a proposed calibration material and with a reporter subclone and lines made by a similar process from different donors. We believe that iPSCs are likely to be used to make multiple clinical products. We further believe that the lines used as input material will be used at different sites and, given their immortal status, will be used for many years or even decades. Therefore, it will be important to develop assays to monitor the state of the cells and their drift in culture. We suggest that a detailed characterization of the initial status of the cells, a comparison with some calibration material and the development of reporter sublcones will help determine which set of tests will be most useful in monitoring the cells and establishing criteria for discarding a line.

Induced pluripotent stem cells from patients with focal cortical dysplasia and refractory epilepsy

Focal cortical dysplasia (FCD) is caused by numerous alterations, which can be divided into abnormalities of the cortical architecture and cytological variations; however, the exact etiology of FCD remains unknown. The generation of induced pluripotent stem cells (iPSCs) from the cells of patients with neurological diseases, and their subsequent tissue‑specific differentiation, serves as an invaluable source for testing and studying the initial development and subsequent progression of diseases associated with the central nervous system. A total of 2 patients demonstrating seizures refractory to drug treatment, characterized as FCD Type IIb, were enrolled in the present study. Fibroblasts were isolated from residual skin fragments obtained from surgical treatment and from brain samples obtained during surgical resection. iPSCs were generated following exposure of fibroblasts to viral vectors containing POU class 5 homeobox 1 (OCT4), sex determining region Y‑box 2 (SOX2), Kruppel‑like factor 4 and c‑MYC genes, and were characterized by immunohistochemical staining for the pluripotent markers homeobox protein NANOG, SOX2, OCT4, TRA1‑60 and TRA1‑81. The brain samples were tested with antibodies against protein kinase B (AKT), phosphorylated‑AKT, mechanistic target of rapamycin (mTOR) and phosphorylated‑mTOR. Analysis of the AKT/mTOR pathway revealed a statistically significant difference between the cerebral tissues of the two patients, which were of different ages (45 and 12 years old). Clones with the morphological features of embryonic cells were detected on the 13th day and were characterized following three subcultures. The positive staining characteristics of the embryonic cells confirmed the successful generation of iPSCs derived from the patients' fibroblasts. Therefore, the present study presents a method to obtain a useful cellular source that may help to understand embryonic brain development associated with FCD.