2014 Vol. 5, No. 1

Cells derived from iPSC can be immunogenic—Yes or No?
Jiani Cao, Xiaoyan Li, Xiao Lu, Chao Zhang, Honghao Yu, Tongbiao Zhao
2014, 5(1): 1-3. doi: 10.1007/s13238-013-0003-2
The induced pluripotent stem cells (iPSCs), derived by ectopic expression of reprogramming factors in somatic cells, can potentially provide unlimited autologous cells for regenerative medicine. In theory, the autologous cells derived from patient iPSCs should be immune tolerant by the host without any immune rejections. However, our recent studies have found that even syngeneic iPSC-derived cells can be immunogenic in syngeneic hosts by using a teratoma transplantation model (Nature 474:212-215, 2011). Recently two research groups differentiated the iPSCs into different germ layers or cells, transplanted those cells to the syngeneic hosts, and evaluated the immunogenicity of those cells. Both of the two studies support our conclusions that some certain but not all tissues derived from iPSCs can be immunogenic, although they claimed either "negligible" or "lack of" immunogenicity in iPSC derivatives (Nature 494:100-104, 2013; Cell Stem Cell 12:407-412, 2013). To test the immunogenicity of clinically valuable cells differentiated from human iPSCs are emergently required for translation of iPSC technology to clinics.
Direct reprogramming of porcine fibroblasts to neural progenitor cells
Xiu-Ling Xu, Ji-Ping Yang, Li-Na Fu, Ruo-Tong Ren, Fei Yi, Keiichiro Suzuki, Kai Liu, Zhi-Chao Ding, Jing Qu, Wei-Qi Zhang, Ying Li, Ting-Ting Yuan, Guo-Hong Yuan, Li-Na Sui, Di Guan, Shun-Lei Duan, Hui-Ze Pan, Ping Wang, Xi-Ping Zhu, Nuria Montserrat, Ming Li, Rui-Jun Bai, Lin Liu, Juan Carlos Izpisua Belmonte, Guang-Hui Liu
2014, 5(1): 4-7. doi: 10.1007/s13238-013-0015-y
Telomere elongation in parthenogenetic stem cells
Yu Yin, Na Liu, Xiaoying Ye, Renpeng Guo, Jie Hao, Fang Wang, Lin Liu
2014, 5(1): 8-11. doi: 10.1007/s13238-013-0006-z
Inflammasomes in cancer: a double-edged sword
Ryan Kolb, Guang-Hui Liu, Ann M. Janowski, Fayyaz S. Sutterwala, Weizhou Zhang
2014, 5(1): 12-20. doi: 10.1007/s13238-013-0001-4
Chronic inflammatory responses have long been observed to be associated with various types of cancer and play decisive roles at different stages of cancer development. Inflammasomes, which are potent inducers of interleukin (IL)-1β and IL-18 during inflammation, are large protein complexes typically consisting of a Nod-like receptor (NLR), the adapter protein ASC, and Caspase-1. During malignant transformation or cancer therapy, the inflammasomes are postulated to become activated in response to danger signals arising from the tumors or from therapy-induced damage to the tumor or healthy tissue. The activation of inflammasomes plays diverse and sometimes contrasting roles in cancer promotion and therapy depending on the specific context. Here we summarize the role of different inflammasome complexes in cancer progression and therapy. Inflammasome components and pathways may provide novel targets to treat certain types of cancer; however, using such agents should be cautiously evaluated due to the complex roles that inflammasomes and proinflammatory cytokines play in immunity.
Micro-management of pluripotent stem cells
Wen-Ting Guo, Xi-Wen Wang, Yangming Wang
2014, 5(1): 36-47. doi: 10.1007/s13238-013-0014-z
Embryonic and induced pluripotent stem cells (ESCs and iPSCs) hold great promise for regenerative medicine. The therapeutic application of these cells requires an understanding of the molecular networks that regulate pluripotency, differentiation, and de-differentiation. Along with signaling pathways, transcription factors, and epigenetic regulators, microRNAs (miRNAs) are emerging as important regulators in the establishment and maintenance of pluripotency. These tiny RNAs control proliferation, survival, the cell cycle, and the pluripotency program of ESCs. In addition, they serve as barriers or factors to overcome barriers during the reprogramming process. Systematic screening for novel miRNAs that regulate the establishment and maintenance of pluripotent stem cells and further mechanistic investigations will not only shed new light on the biology of ESCs and iPSCs, but also help develop safe and efficient technologies to manipulate cell fate for regenerative medicine.
Research articles
Direct conversion of human fibroblasts into retinal pigment epithelium-like cells by defined factors
Kejing Zhang, Guang-Hui Liu, Fei Yi, Nuria Montserrat, Tomoaki Hishida, Concepcion Rodriguez Esteban, Juan Carlos Izpisua Belmonte
2014, 5(1): 48-58. doi: 10.1007/s13238-013-0011-2
The generation of functional retinal pigment epithelium (RPE) is of great therapeutic interest to the field of regenerative medicine and may provide possible cures for retinal degenerative diseases, including age-related macular degeneration (AMD). Although RPE cells can be produced from either embryonic stem cells or induced pluripotent stem cells, direct cell reprogramming driven by lineage-determining transcription factors provides an immediate route to their generation. By monitoring a human RPE specific Best1::GFP reporter, we report the conversion of human fibroblasts into RPE lineage using defined sets of transcription factors. We found that Best1::GFP positive cells formed colonies and exhibited morphological and molecular features of early stage RPE cells. Moreover, they were able to obtain pigmentation upon activation of Retinoic acid (RA) and Sonic Hedgehog (SHH) signaling pathways. Our study not only established an ideal platform to investigate the transcriptional network regulating the RPE cell fate determination, but also provided an alternative strategy to generate functional RPE cells that complement the use of pluripotent stem cells for disease modeling, drug screening, and cell therapy of retinal degeneration.
Global DNA methylation and transcriptional analyses of human ESC-derived cardiomyocytes
Ying Gu, Guang-Hui Liu, Nongluk Plongthongkum, Christopher Benner, Fei Yi, Jing Qu, Keiichiro Suzuki, Jiping Yang, Weiqi Zhang, Mo Li, Nuria Montserrat, Isaac Crespo, Antonio del Sol, Concepcion Rodriguez Esteban, Kun Zhang, Juan Carlos Izpisua Belmonte
2014, 5(1): 59-68. doi: 10.1007/s13238-013-0016-x
With defined culture protocol, human embryonic stem cells (hESCs) are able to generate cardiomyocytes in vitro, therefore providing a great model for human heart development, and holding great potential for cardiac disease therapies. In this study, we successfully generated a highly pure population of human cardiomyocytes (hCMs) (>95% cTnT+) from hESC line, which enabled us to identify and characterize an hCM-specific signature, at both the gene expression and DNA methylation levels. Gene functional association network and gene-disease network analyses of these hCM-enriched genes provide new insights into the mechanisms of hCM transcriptional regulation, and stand as an informative and rich resource for investigating cardiac gene functions and disease mechanisms. Moreover, we show that cardiac-structural genes and cardiac-transcription factors have distinct epigenetic mechanisms to regulate their gene expression, providing a better understanding of how the epigenetic machinery coordinates to regulate gene expression in different cell types.
Genetic approach to track neural cell fate decisions using human embryonic stem cells
Xuemei Fu, Zhili Rong, Shengyun Zhu, Xiaocheng Wang, Yang Xu, Blue B. Lake
2014, 5(1): 69-79. doi: 10.1007/s13238-013-0007-y
With their capability to undergo unlimited self-renewal and to differentiate into all cell types in the body, human embryonic stem cells (hESCs) hold great promise in human cell therapy. However, there are limited tools for easily identifying and isolating live hESC-derived cells. To track hESC-derived neural progenitor cells (NPCs), we applied homologous recombination to knock-in the mCherry gene into the Nestin locus of hESCs. This facilitated the genetic labeling of Nestin positive neural progenitor cells with mCherry. Our reporter system enables the visualization of neural induction from hESCs both in vitro (embryoid bodies) and in vivo (teratomas). This system also permits the identification of different neural subpopulations based on the intensity of our fluorescent reporter. In this context, a high level of mCherry expression showed enrichment for neural progenitors, while lower mCherry corresponded with more committed neural states. Combination of mCherry high expression with cell surface antigen staining enabled further enrichment of hESC-derived NPCs. These mCherry+ NPCs could be expanded in culture and their differentiation resulted in a down-regulation of mCherry consistent with the loss of Nestin expression. Therefore, we have developed a fluorescent reporter system that can be used to trace neural differentiation events of hESCs.
Gadd45a deletion aggravates hematopoietic stem cell dysfunction in ATM-deficient mice
Yulin Chen, Runan Yang, Peng Guo, Zhenyu Ju
2014, 5(1): 80-89. doi: 10.1007/s13238-013-0017-9
Ataxia telangiectasia mutated (ATM) kinase plays an essential role in the maintenance of genomic stability. ATM-deficient (ATM-/-) mice exhibit hematopoietic stem cell (HSC) dysfunction and a high incidence of lymphoma. Gadd45a controls cell cycle arrest, apoptosis and DNA repair, and is involved in the ATM-p53 mediated DNA damage response. However, the role of Gadd45a in regulating the functionality of ATM-/- HSCs is unknown. Here we report that Gadd45a deletion did not rescue the defects of T-cells and B-cells development in ATM-/- mice. Instead, ATM and Gadd45a double knockout (ATM-/- Gadd45a-/-) HSCs exhibited an aggravated defect in long-term self-renewal capacity compared to ATM-/- HSCs in HSC transplantation experiments. Further experiments revealed that the aggravated defect of ATM-/- Gadd45a-/- HSCs was due to a reduction of cell proliferation, associated with an accumulation of DNA damage and subsequent activation of DNA damage response including an up-regulation of p53-p21 signaling pathway. Additionally, ATM-/- Gadd45a-/- mice showed an increased incidence of hematopoietic malignancies, as well as an increased rate of metastasis than ATM-/- mice. In conclusion, Gadd45a deletion aggravated the DNA damage accumulation, which subsequently resulted in a further impaired self-renewal capacity and an increased malignant transformation in ATM-/- HSCs.