Induced pluripotent stem cells (iPSCs), reprogrammed from somatic cells with defined factors, hold great promise for regenerative medicine as the renewable source of autologous cells. Whereas it has ...been generally assumed that these autologous cells should be immune-tolerated by the recipient from whom the iPSCs are derived, their immunogenicity has not been vigorously examined. We show here that, whereas embryonic stem cells (ESCs) derived from inbred C57BL/6 (B6) mice can efficiently form teratomas in B6 mice without any evident immune rejection, the allogeneic ESCs from 129/SvJ mice fail to form teratomas in B6 mice due to rapid rejection by recipients. B6 mouse embryonic fibroblasts (MEFs) were reprogrammed into iPSCs by either retroviral approach (ViPSCs) or a novel episomal approach (EiPSCs) that causes no genomic integration. In contrast to B6 ESCs, teratomas formed by B6 ViPSCs were mostly immune-rejected by B6 recipients. In addition, the majority of teratomas formed by B6 EiPSCs were immunogenic in B6 mice with T cell infiltration, and apparent tissue damage and regression were observed in a small fraction of teratomas. Global gene expression analysis of teratomas formed by B6 ESCs and EiPSCs revealed a number of genes frequently overexpressed in teratomas derived from EiPSCs, and several such gene products were shown to contribute directly to the immunogenicity of the B6 EiPSC-derived cells in B6 mice. These findings indicate that, in contrast to derivatives of ESCs, abnormal gene expression in some cells differentiated from iPSCs can induce T-cell-dependent immune response in syngeneic recipients. Therefore, the immunogenicity of therapeutically valuable cells derived from patient-specific iPSCs should be evaluated before any clinic application of these autologous cells into the patients.
Fibrotic skin disease represents a major global healthcare burden, characterized by fibroblast hyperproliferation and excessive accumulation of extracellular matrix. Fibroblasts are found to be ...heterogeneous in multiple fibrotic diseases, but fibroblast heterogeneity in fibrotic skin diseases is not well characterized. In this study, we explore fibroblast heterogeneity in keloid, a paradigm of fibrotic skin diseases, by using single-cell RNA-seq. Our results indicate that keloid fibroblasts can be divided into 4 subpopulations: secretory-papillary, secretory-reticular, mesenchymal and pro-inflammatory. Interestingly, the percentage of mesenchymal fibroblast subpopulation is significantly increased in keloid compared to normal scar. Functional studies indicate that mesenchymal fibroblasts are crucial for collagen overexpression in keloid. Increased mesenchymal fibroblast subpopulation is also found in another fibrotic skin disease, scleroderma, suggesting this is a broad mechanism for skin fibrosis. These findings will help us better understand skin fibrotic pathogenesis, and provide potential targets for fibrotic disease therapies.
Dear Editor,
CRISPR-Cas9 （clustered regularly interspaced short palin- dromic repeats-CRISPR associated） systems have been harnessed for kinds of genome manipulation, including gene editing, ...transcription regulation, and chromosome loci imaging （Dominguez et al., 2016; Komor et al., 2017）. A typical engineered CRISPR-Cas9 system is composed of a Cas9 protein and a single guide RNA （sgRNA）, which could form a protein/RNA complex to recognize and cleave DNA sequence （Hsu et al., 2014; Wright et al., 2016）.
The coronavirus disease 2019 (COVID-19) pandemic is caused by infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is spread primary via respiratory droplets and ...infects the lungs. Currently widely used cell lines and animals are unable to accurately mimic human physiological conditions because of the abnormal status of cell lines (transformed or cancer cells) and species differences between animals and humans. Organoids are stem cell-derived selforganized three-dimensional culture in vitro and model the physiological conditions of natural organs. Here we showed that SARS-CoV-2 infected and extensively replicated in human embryonic stem cells (hESCs)-derived lung organoids, including airway and alveolar organoids which covered the complete infection and spread route for SARS-CoV-2 within lungs. The infected cells were ciliated, club, and alveolar type 2 (AT2) cells, which were sequentially located from the proximal to the distal airway and terminal alveoli, respectively. Additionally, RNA-seq revealed early cell response to virus infection including an unexpected downregulation of the metabolic processes, especially lipid metabolism, in addition to the well-known upregulation of immune response. Further, Remdesivir and a human neutralizing antibody potently inhibited SARS-CoV-2 replication in lung organoids. Therefore, human lung organoids can serve as a pathophysiological model to investigate the underlying mechanism of SARS-CoV-2 infection and to discover and test therapeutic drugs for COVID-19.
Human embryonic stem cells (hESCs) hold great promise for cell therapy as a source of diverse differentiated cell types. One key bottleneck to realizing such potential is allogenic immune rejection ...of hESC-derived cells by recipients. Here, we optimized humanized mice (Hu-mice) reconstituted with a functional human immune system that mounts a vigorous rejection of hESCs and their derivatives. We established knockin hESCs that constitutively express CTLA4-Ig and PD-L1 before and after differentiation, denoted CP hESCs. We then demonstrated that allogenic CP hESC-derived teratomas, fibroblasts, and cardiomyocytes are immune protected in Hu-mice, while cells derived from parental hESCs are effectively rejected. Expression of both CTLA4-Ig, which disrupts T cell costimulatory pathways, and PD-L1, which activates T cell inhibitory pathway, is required to confer immune protection, as neither was sufficient on their own. These findings are instrumental for developing a strategy to protect hESC-derived cells from allogenic immune responses without requiring systemic immune suppression.
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•Optimized Hu-mice for studying human immune responses to hESC-derived allografts•CTLA4-Ig/PD-L1 were knocked into hESCs and provided localized immune protection•Allografts from modified hESCs did not induce systemic immunosuppression•CTLA4-Ig and PD-L1 are both required for immune protection of allografts
A strategy for localized immune suppression developed by Rong et al. protects hESC-derived cells from an allogenic immune response in an optimized humanized mouse model, without inducing systemic immune suppression.
Genome-wide mapping of chromatin interactions at high resolution remains experimentally and computationally challenging. Here we used a low-input “easy Hi-C” protocol to map the 3D genome ...architecture in human neurogenesis and brain tissues and also demonstrated that a rigorous Hi-C bias-correction pipeline (HiCorr) can significantly improve the sensitivity and robustness of Hi-C loop identification at sub-TAD level, especially the enhancer-promoter (E-P) interactions. We used HiCorr to compare the high-resolution maps of chromatin interactions from 10 tissue or cell types with a focus on neurogenesis and brain tissues. We found that dynamic chromatin loops are better hallmarks for cellular differentiation than compartment switching. HiCorr allowed direct observation of cell-type- and differentiation-specific E-P aggregates spanning large neighborhoods, suggesting a mechanism that stabilizes enhancer contacts during development. Interestingly, we concluded that Hi-C loop outperforms eQTL in explaining neurological GWAS results, revealing a unique value of high-resolution 3D genome maps in elucidating the disease etiology.
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•HiCorr allows robust mapping of sub-TAD chromatin interactions with Hi-C•Low-input “easy Hi-C” protocol compatible with 50–100k cells•Enhancer loops and aggregates are better marks of cell identity than compartments•Chromatin loops outperform eQTLs in defining neurological GWAS target genes
Lu et al. developed a rigorous Hi-C bias-correction pipeline to significantly improve the robustness of high-resolution chromatin interaction maps. With a new low-input “easy Hi-C” protocol, they mapped chromatin interactions in neural samples, defined cell-type-specific enhancer loops and aggregates, and concluded that Hi-C outperforms eQTL in explaining GWAS results.
The regulation of the transcription factor sex-determining region Y-box transcription factor 9 (SOX9) in lung development has been described in mouse, but the same principles apply to human lung ...development is unknown due to a lack of appropriate experimental approaches and models.
Here, we used gene editing technology to inactivate SOX9 in human embryonic stem cells that were then induced to differentiate into lung organoids to investigate the role of SOX9 in human lung epithelium development.
Complete knockout of the transactivation domain of SOX9 by gene editing resulted in indels in both alleles of SOX9. SOX9
hESCs could be induced to differentiate into lung progenitor organoids. In vitro long-term expansion showed that SOX9 inactivation did not affect the differentiation of pulmonary epithelial cells, but promoted apoptosis and reduced proliferative capacity in the organoids. When lung progenitor organoids were transplanted under the kidney capsule of immunodeficient mice, expression of the club cell marker secretoglobin family 1A member 1 (SCGB1A1) was detected in SOX9
transplants but was absent in wild-type (WT) transplants. The maturation of goblet cells was also affected by SOX9 inactivation, as evidenced by the presence of mucin 5 AC (MUC5AC) in the cytoplasm of SOX9
grafts as compared to WT grafts in which most MUC5AC was secreted into the lumen. In vivo lung orthotopic transplantations showed that SOX9 inactivation had a limited effect on the differentiation of alveolar cells and lung regeneration in injured mice.
SOX9 modulates the proliferative capacity of lung epithelium but is not an indispensable transcription factor in the regulation of human lung epithelium development.
As the renewable source of all cell types in the body, human embryonic stem cells (hESCs) hold great promise for human cell therapy. However, one major bottleneck that hinders the clinic application ...of hESCs is that hESCs remaining with their differentiated derivatives pose cancer risk by forming teratomas after transplantation. NANOG is a critical pluripotency factor specifically expressed in hESCs but rarely in their differentiated derivatives. By introducing a hyperactive variant of herpes simplex virus thymidine kinase gene into the 3′-untranslated region of the endogenous NANOG gene of hESCs through homologous recombination, we developed a safe and highly scalable approach to efficiently eliminate the teratoma risk associated with hESCs without apparent negative impact on their differentiated cell types. As thymidine kinase is widely used in human gene therapy trials and is the therapeutic target of U. S. Food and Drug Administration-approved drugs, our strategy could be effectively applied to the clinic development of hESC-based human cell therapy.
Background: One of the major hurdles hindering the clinic development of hESC-based therapy is the teratoma risk.
Results: A genetic modification via homologous recombination can effectively eliminate hESCs without killing their derivatives.
Conclusion: A scalable and safe approach to eliminate the teratoma risk associated with hESCs.
Significance: Our approach improves the feasibility to develop hESCs into human cell therapy.
The use of immunotherapy has achieved great advances in the treatment of cancer. Macrophages play a pivotal role in the immune defense system, serving both as phagocytes (removal of pathogens and ...cancer cells) and as antigen‐presenting cells (activation of T cells). However, research regarding tumor immunotherapy is mainly focused on the adaptive immune system. The usefulness of innate immune cells (eg, macrophages) in the treatment of cancer has not been extensively investigated. Recent advances in synthetic biology and the increasing understanding of the cluster of differentiation 47/signal regulatory protein alpha (CD47/SIRPɑ) axis may provide new opportunities for the clinical application of engineered macrophages. The CD47/SIRPɑ axis is a major known pathway, repressing phagocytosis and activation of macrophages. In this article, we summarize the currently available evidence regarding the CD47/SIRPɑ axis, and immunotherapies based on blockage. In addition, we propose cell therapy strategies based on macrophage engineering.
The immunotherapy has achieved great progress in cancer treatment. In the article, we review current knowledge about cluster of differentiation 47/signal regulatory protein alpha (CD47/SIRPɑ) pathway and immunotherapies based on blocking CD47/SIRPɑ axis, and we also propose a cell therapy strategy to engineer macrophage to attack cancer cells in the future
The immune system of skin develops in stages in mice. However, the developmental dynamics of immune cells in human skin remains elusive. Here, we perform transcriptome profiling of CD45+ ...hematopoietic cells in human fetal skin at an estimated gestational age of 10–17 weeks by single-cell RNA sequencing. A total of 13 immune cell types are identified. Skin macrophages show dynamic heterogeneity over the course of skin development. A major shift in lymphoid cell developmental states occurs from the first to the second trimester that implies an in situ differentiation process. Gene expression analysis reveals a typical developmental program in immune cells in accordance with their functional maturation, possibly involving metabolic reprogramming. Finally, we identify transcription factors (TFs) that potentially regulate cellular transitions by comparing TFs and TF target gene networks. These findings provide detailed insight into how the immune system of the human skin is established during development.
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•Single-cell RNA sequencing reveals diverse immune cells in human fetal skin•Macrophages are heterogeneous and dynamic in fetal skin development•Innate lymphoid lineages gradually differentiate from early to mid-gestation•Skin immune cell development is associated with metabolic reprogramming
Xu et al. perform single-cell transcriptome profiling of immune cells in human fetal skin at early- to mid-gestation. They highlight the heterogeneity and dynamic developmental process of macrophages and innate lymphoid cells and reveal metabolic reprogramming and transcription factors (TFs) transition involved in cell differentiation in situ.
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