Fanyi Zeng

iPS cells produce viable mice through tetraploid complementation

Since the initial description of induced pluripotent stem (iPS) cells created by forced expression of four transcription factors in mouse fibroblasts, the technique has been used to generate embryonic stem (ES)-cell-like pluripotent cells from a variety of cell types in other species, including primates and rat. It has become a popular means to reprogram somatic genomes into an embryonic-like pluripotent state, and a preferred alternative to somatic-cell nuclear transfer and somatic-cell fusion with ES cells. However, iPS cell reprogramming remains slow and inefficient. Notably, no live animals have been produced by the most stringent tetraploid complementation assay, indicative of a failure to create fully pluripotent cells. Here we report the generation of several iPS cell lines that are capable of generating viable, fertile live-born progeny by tetraploid complementation. These iPS cells maintain a pluripotent potential that is very close to ES cells generated from in vivo or nuclear transfer embryos. We demonstrate the practicality of using iPS cells as useful tools for the characterization of cellular reprogramming and developmental potency, and confirm that iPS cells can attain true pluripotency that is similar to that of ES cells.

A Call for Standardized Naming and Reporting of Human ESC and iPSC Lines

Human embryonic and induced pluripotent stem cell lines are being generated at a rapid pace and now number in the thousands. We propose a standard nomenclature and suggest the use of a centralized database for all cell line names and a minimum set of information for reporting new derivations.

Viable Fertile Mice Generated from Fully Pluripotent iPS Cells Derived from Adult Somatic Cells

Previous studies demonstrated that induced pluripotent stem (iPS) cells could produce viable mice through tetraploid complementation, which was thought to be the most stringent test for pluripotency. However, these highly pluripotent iPS cells were previously reported to be generated from fibroblasts of embryonic origin. Achieving fully pluripotent iPS cells from multiple cell types, especially easily accessible adult tissues, will lead to a much greater clinical impact. We successfully generated high-pluripotency iPS cells from adult tail tip fibroblasts (TTF) that resulted in viable, full-term, fertile TTF-iPS animals with no obvious teratoma formation or other developmental abnormalities. Comparison of iPS cells from embryonic origin (MEF), progenitor cells (neural stem cells) or differentiated somatic cells (TTF) reveals that fully pluripotent developmental potential can be reached by each cell type, although with different induction efficiencies. This work provides the means for studying the mechanisms and regulation of direct reprogramming, and has encouraging implications for future clinical applications and therapeutic interventions.

Points to consider in the development of seed stocks of pluripotent stem cells for clinical applications: International Stem Cell Banking Initiative (ISCBI)

In 2009 the International Stem Cell Banking Initiative (ISCBI) contributors and the Ethics Working Party of the International Stem Cell Forum published a consensus on principles of best practice for the procurement, cell banking, testing and distribution of human embryonic stem cell (hESC) lines for research purposes [1], which was broadly also applicable to human induced pluripotent stem cell (hiPSC) lines. Here, we revisit this guidance to consider what the requirements would be for delivery of the early seed stocks of stem cell lines intended for clinical applications. The term ‘seed stock’ is used here to describe those cryopreserved stocks of cells established early in the passage history of a pluripotent stem cell line in the lab that derived the line or a stem cell bank, hereafter called the ‘repository’.

Mice generated from tetraploid complementation competent iPS cells show similar developmental features as those from ES cells but are prone to tumorigenesis.

Mice generated from tetraploid complementation competent iPS cells show similar developmental features as those from ES cells but are prone to tumorigenesis

Production of mice using iPS cells and tetraploid complementation.

Induced pluripotent stem cells (iPSCs) are considered to be an attractive alternative to embryonic stem cells (ESCs) and may provide great potential for clinical applications in regenerative medicine. Although possessing characteristics similar to ESCs, the true pluripotency of these newly studied iPSCs was not known because none of the previously developed iPSCs passed the tetraploid complementation assay, which is regarded as the most stringent test for pluripotency. We have recently shown that by modifying some of the culture conditions for inducing iPSCs, we were able to generate cell lines of high pluripotency, resulting in the production of live-born, fertile animals through tetraploid complementation. In this paper, we describe details of our methods of generating iPS cell lines and subsequently producing full-term live animals through the tetraploid complementation assay; the procedure can be completed within 2 months.

Efficient and rapid generation of induced pluripotent stem cells using an alternative culture medium

Efficient and rapid generation of induced pluripotent stem cells using an alternative culture medium

Identifiability and Privacy in Pluripotent Stem Cell Research

Data sharing is an essential element of research; however, recent scientific and social developments have challenged conventional methods for protecting privacy. Here we provide guidance for determining data sharing thresholds for human pluripotent stem cell research aimed at a wide range of stakeholders, including research consortia, biorepositories, policy-makers, and funders.

Establishment of customized mouse stem cell lines by sequential nuclear transfer

Therapeutic cloning, whereby embryonic stem cells (ESCs) are derived from nuclear transfer (NT) embryos, may play a major role in the new era of regenerative medicine. In this study we established forty nuclear transfer-ESC (NT-ESC) lines that were derived from NT embryos of different donor cell types or passages. We found that NT-ESCs were capable of forming embryoid bodies. In addition, NT-ESCs expressed pluripotency stem cell markers in vitro and could differentiate into embryonic tissues in vivo. NT embryos from early passage R1 donor cells were able to form full term developed pups, whereas those from late passage R1 ES donor cells lost the potential for reprogramming that is essential for live birth. We subsequently established sequential NT-R1-ESC lines that were developed from NT blastocyst of late passage R1 ESC donors. However, these NT-R1-ESC lines, when used as nuclear transfer donors at their early passages, failed to result in live pups. This indicates that the therapeutic cloning process using sequential NT-ESCs may not rescue the developmental deficiencies that resided in previous donor generations.

Publishing SNP genotypes of human embryonic stem cell lines: policy statement of the International Stem Cell Forum Ethics Working Party.

Novel methods and associated tools permitting individual identification in publicly accessible SNP databases have become a debatable issue. There is growing concern that current technical and ethical safeguards to protect the identities of donors could be insufficient. In the context of human embryonic stem cell research, there are no studies focusing on the probability that an hESC line donor could be identified by analyzing published SNP profiles and associated genotypic and phenotypic information. We present the International Stem Cell Forum (ISCF) Ethics Working Party’s Policy Statement on “Publishing SNP Genotypes of Human Embryonic Stem Cell Lines (hESC)”. The Statement prospectively addresses issues surrounding the publication of genotypic data and associated annotations of hESC lines in open access databases. It proposes a balanced approach between the goals of open science and data sharing with the respect for fundamental bioethical principles (autonomy, privacy, beneficence, justice and research merit and integrity).