Genetic and epigenetic instability in human pluripotent stem cells

Stem Cells and Organ Transplantation: Resetting Our Biological Clocks

The human body has only a limited ability to repair itself. Illness, injury, and aging can overwhelm its built-in capability to replace dysfunctional, damaged, or destroyed tissues. We can at best only partly regenerate our organs and cannot grow back a whole limb.

Successful Generation of Human Induced Pluripotent Stem Cell Lines from Blood Samples Held at Room Temperature for up to 48 hr

The collection sites of human primary tissue samples and the receiving laboratories, where the human induced pluripotent stem cells (hIPSCs) are derived, are often not on the same site. Thus, the stability of samples prior to derivation constrains the distance between the collection site and the receiving laboratory. To investigate sample stability, we collected blood and held it at room temperature for 5, 24, or 48 hr before isolating peripheral blood mononuclear cells (PBMCs) and reprogramming into IPSCs. Additionally, PBMC samples at 5- and 48-hr time points were frozen in liquid nitrogen for 4 months and reprogrammed into IPSCs. hIPSC lines derived from all time points were pluripotent, displayed no marked difference in chromosomal aberration rates, and differentiated into three germ layers. Reprogramming efficiency at 24- and 48-hr time points was 3- and 10-fold lower, respectively, than at 5 hr; the freeze-thaw process of PBMCs resulted in no obvious change in reprogramming efficiency.

Multipotent stromal cells derived from common marmoset Callithrix jacchus within alginate 3D environment: Effect of cryopreservation procedures

Multipotent stromal cells derived from the common marmoset monkey Callithrix jacchus (cjMSCs) possess high phylogenetic similarity to humans, with a great potential for preclinical studies in the field of regenerative medicine. Safe and effective long-term storage of cells is of great significance to clinical and research applications. Encapsulation of such cell types within alginate beads that can mimic an extra-cellular matrix and provide a supportive environment for cells during cryopreservation, has several advantages over freezing of cells in suspension. In this study we have analysed the effect of dimethyl sulfoxide (Me2SO, 2.5-10%, v/v) and pre-freeze loading time of alginate encapsulated cjMSCs in Me2SO (0-45 min) on the viability and metabolic activity of the cells after freezing using a slow cooling rate (-1°C/min). It was found that these parameters affect the stability and homogeneity of alginate beads after thawing. Moreover, the cjMSCs can be frozen in alginate beads with lower Me2SO concentration of 7.5% after 30 min of loading, while retaining high cryopreservation outcome. We demonstrated the maximum viability, membrane integrity and metabolic activity of the cells under optimized, less cytotoxic conditions. The results of this study are another step forward towards the application of cryopreservation for the long-term storage and subsequent applications of transplants in cell-based therapies.

Genomic instability of human embryonic stem cell lines using different passaging culture methods

Background

Human embryonic stem cells exhibit genomic instability that can be related to culture duration or to the passaging methods used for cell dissociation. In order to study the impact of cell dissociation techniques on human embryonic stem cells genomic instability, we cultured H1 and H9 human embryonic stem cells lines using mechanical/manual or enzymatic/collagenase-IV dissociation methods. Genomic instability was evaluated at early (<p60) and late (>p60) passages by using oligonucleotide based array-comparative genomic hybridization 105 K with a mean resolution of 50 Kb.

Results

DNA variations were mainly located on subtelomeric and pericentromeric regions with sizes <100 Kb. In this study, 9 recurrent genomic variations were acquired during culture including the well known duplication 20q11.21. When comparing cell dissociation methods, we found no significant differences between DNA variations number and size, DNA gain or DNA loss frequencies, homozygous loss frequencies and no significant difference on the content of genes involved in development, cell cycle tumorigenesis and syndrome disease. In addition, we have never found any malignant tissue in 4 different teratoma representative of the two independent stem cell lines.

Conclusions

These results show that the occurrence of genomic instability in human embryonic stem cells is similar using mechanical or collagenase IV-based enzymatic cell culture dissociation methods. All the observed genomic variations have no impact on the development of malignancy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-015-0133-8) contains supplementary material, which is available to authorized users.

Xenogeneic-free defined conditions for derivation and expansion of human embryonic stem cells with mesenchymal stem cells

The potential applications of human embryonic stem cells (hESCs) in regenerative medicine and developmental research have made stem cell biology one of the most fascinating and rapidly expanding fields of biomedicine. The first clinical trial of hESCs in humans has begun, and the field of stem cell therapy has just entered a new era. Here, we report seven hESC lines (SEES-1, -2, -3, -4, -5, -6, and -7). Four of them were derived and maintained on irradiated human mesenchymal stem cells (hMSCs) grown in xenogeneic-free defined media and substrate. Xenogeneic-free hMSCs isolated from the subcutaneous tissue of extra fingers from individuals with polydactyly showed appropriate potentials as feeder layers in the pluripotency and growth of hESCs. In this report, we describe a comprehensive characterization of these newly derived SEES cell lines. In addition, we developed a scalable culture system for hESCs having high biological safety by using gamma-irradiated serum replacement and pharmaceutical-grade recombinant basic fibroblast growth factor (bFGF, also known as trafermin). This is first report describing the maintenance of hESC pluripotency using pharmaceutical-grade human recombinant bFGF (trafermin) and gamma-irradiated serum replacement. Our defined medium system provides a path to scalability in Good Manufacturing Practice (GMP) settings for the generation of clinically relevant cell types from pluripotent cells for therapeutic applications.

Partial regeneration and reconstruction of the rat uterus through recellularization of a decellularized uterine matrix

Despite dramatic progress in infertility treatments and assisted reproduction, no effective therapies exist for complete loss of uterine structure and/or function. For such patients, genetic motherhood is possible only through gestational surrogacy or uterine transplantation. However, many ethical, social, technical and safety challenges accompany such approaches. A theoretical alternative is to generate a bioartificial uterus, which requires engineering of uterine architecture and appropriate cellular constituents. Here, rat uteri decellularization by aortic perfusion with detergents produced an underlying extracellular matrix together with an acellular, perfusable vascular architecture. Uterine-like tissues were then regenerated and maintained in vitro for up to 10 d through decellularized uterine matrix (DUM) reseeding with adult and neonatal rat uterine cells and rat mesenchymal stem cells followed by aortic perfusion in a bioreactor. Furthermore, DUM placement onto a partially excised uterus yielded recellularization and regeneration of uterine tissues and achievement of pregnancy nearly comparable to the intact uterus. These results suggest that DUM could be used for uterine regeneration, and provides insights into treatments for uterine factor infertility.

Stem cells for brain repair in neonatal hypoxia-ischemia

Neonatal hypoxic-ischemic insults are a significant cause of pediatric encephalopathy, developmental delays, and spastic cerebral palsy. Although the developing brain's plasticity allows for remarkable self-repair, severe disruption of normal myelination and cortical development upon neonatal brain injury are likely to generate life-persisting sensory-motor and cognitive deficits in the growing child. Currently, no treatments are available that can address the long-term consequences. Thus, regenerative medicine appears as a promising avenue to help restore normal developmental processes in affected infants. Stem cell therapy has proven effective in promoting functional recovery in animal models of neonatal hypoxic-ischemic injury and therefore represents a hopeful therapy for this unmet medical condition. Neural stem cells derived from pluripotent stem cells or fetal tissues as well as umbilical cord blood and mesenchymal stem cells have all shown initial success in improving functional outcomes. However, much still remains to be understood about how those stem cells can safely be administered to infants and what their repair mechanisms in the brain are. In this review, we discuss updated research into pathophysiological mechanisms of neonatal brain injury, the types of stem cell therapies currently being tested in this context, and the potential mechanisms through which exogenous stem cells might interact with and influence the developing brain.

Mesenchymal derivatives of genetically unstable human embryonic stem cells are maintained unstable but undergo senescence in culture as do bone marrow-derived mesenchymal stem cells

Recurrent chromosomal alterations have been repeatedly reported in cultured human embryonic stem cells (hESCs). The effects of these alterations on the capability of pluripotent cells to differentiate and on growth potential of their specific differentiated derivatives remain unclear. Here, we report that the hESC lines HUES-7 and -9 carrying multiple chromosomal alterations produce in vitro mesenchymal stem cells (MSCs) that show progressive growth arrest and enter senescence after 15 and 16 passages, respectively. There was no difference in their proliferative potential when compared with bone marrow-derived MSCs. Array comparative genomic hybridization analysis (aCGH) of hESCs and their mesenchymal derivatives revealed no significant differences in chromosomal alterations, suggesting that genetically altered hESCs are not selected out during differentiation. Our findings indicate that genetically unstable hESCs maintain their capacity to differentiate in vitro into MSCs, which exhibit an in vitro growth pattern of normal MSCs and not that of transformed cells.

Gain of 20q11.21 in human embryonic stem cells improves cell survival by increased expression of Bcl-xL

Gain of 20q11.21 is a chromosomal abnormality that is recurrently found in human pluripotent stem cells and cancers, strongly suggesting that this mutation confers a proliferative or survival advantage to these cells. In this work we studied three human embryonic stem cell (hESC) lines that acquired a gain of 20q11.21 during in vitro culture. The study of the mRNA gene expression levels of the loci located in the common region of duplication showed that HM13, ID1, BCL2L1, KIF3B and the immature form of the micro-RNA miR-1825 were up-regulated in mutant cells. ID1 and BCL2L1 were further studied as potential drivers of the phenotype of hESC with a 20q11.21 gain. We found no increase in the protein levels of ID1, nor the downstream effects expected from over-expression of this gene. On the other hand, hESC with a gain of 20q11.21 had on average a 3-fold increase of Bcl-xL (the anti-apoptotic isoform of BCL2L1) protein levels. The mutant hESC underwent 2- to 3-fold less apoptosis upon loss of cell-to-cell contact and were ∼2-fold more efficient in forming colonies from a single cell. The key role of BCL2L1 in this mutation was further confirmed by transgenic over-expression of BCL2L1 in the wild-type cells, leading to apoptosis-resistant cells, and BCL2L1-knock-down in the mutant hESC, resulting in a restoration of the wild-type phenotype. This resistance to apoptosis supposes a significant advantage for the mutant cells, explaining the high frequency of gains of 20q11.21 in human pluripotent stem cells.

Technological progress and challenges towards cGMP manufacturing of human pluripotent stem cells based therapeutic products for allogeneic and autologous cell therapies

Recent technological advances in the generation, characterization, and bioprocessing of human pluripotent stem cells (hPSCs) have created new hope for their use as a source for production of cell-based therapeutic products. To date, a few clinical trials that have used therapeutic cells derived from hESCs have been approved by the Food and Drug Administration (FDA), but numerous new hPSC-based cell therapy products are under various stages of development in cell therapy-specialized companies and their future market is estimated to be very promising. However, the multitude of critical challenges regarding different aspects of hPSC-based therapeutic product manufacturing and their therapies have made progress for the introduction of new products and clinical applications very slow. These challenges include scientific, technological, clinical, policy, and financial aspects. The technological aspects of manufacturing hPSC-based therapeutic products for allogeneic and autologous cell therapies according to good manufacturing practice (cGMP) quality requirements is one of the most important challenging and emerging topics in the development of new hPSCs for clinical use. In this review, we describe main critical challenges and highlight a series of technological advances in all aspects of hPSC-based therapeutic product manufacturing including clinical grade cell line development, large-scale banking, upstream processing, downstream processing, and quality assessment of final cell therapeutic products that have brought hPSCs closer to clinical application and commercial cGMP manufacturing.

Stress cycles in stem cells/iPSCs development: implications for tissue repair

Stem cells have become a major topic, both publicly and scientifically, owing to their potential to cure diseases and repair damaged tissues. Particular attention has been given to the so-called "induced pluripotent stem cells" (iPSCs) in which somatic cells are induced by the expression of transcription factor encoding transgenes-a methodology first established by Takahashi and Yamanaka (Cell 126:663-676, 2006)-to acquire pluripotent state. This methodology has captured researchers' imagination as a potential procedure to obtain patient-specific therapies while also solving both the problem of transplant rejection and the ethical concerns often raised regarding the use of embryonic stem cells in regenerative medicine. The study of the biology of stem cells/iPSCs, in recent years, has uncovered some fundamental weaknesses that undermine their potential use in transplantation therapies.