SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Stem cell reports

184

Human embryonic stem cell (hESC)-derived pancreatic progenitor cells effectively reverse hyperglycemia in rodent models of type 1 diabetes, but their capacity to treat type 2 diabetes has not been reported. An immunodeficient model of type 2 diabetes was generated by high-fat diet (HFD) feeding in SCID-beige mice. Exposure to HFDs did not impact the maturation of macroencapsulated pancreatic progenitor cells into glucose-responsive insulin-secreting cells following transplantation, and the cell therapy improved glucose tolerance in HFD-fed transplant recipients after 24 weeks. However, since diet-induced hyperglycemia and obesity were not fully ameliorated by transplantation alone, a second cohort of HFD-fed mice was treated with pancreatic progenitor cells combined with one of three antidiabetic drugs. All combination therapies rapidly improved body weight and co-treatment with either sitagliptin or metformin improved hyperglycemia after only 12 weeks. Therefore, a stem cell-based therapy may be effective for treating type 2 diabetes, particularly in combination with antidiabetic drugs.

Concepts: Insulin, Diabetes mellitus type 2, Diabetes mellitus, Stem cell, Obesity, Embryonic stem cell, Sulfonylurea, Metformin

168

Reprogramming of differentiated cells into induced pluripotent stem cells has been recently achieved in vivo in mice. Telomeres are essential for chromosomal stability and determine organismal life span as well as cancer growth. Here, we study whether tissue dedifferentiation induced by in vivo reprogramming involves changes at telomeres. We find telomerase-dependent telomere elongation in the reprogrammed areas. Notably, we found highly upregulated expression of the TRF1 telomere protein in the reprogrammed areas, which was independent of telomere length. Moreover, TRF1 inhibition reduced in vivo reprogramming efficiency. Importantly, we extend the finding of TRF1 upregulation to pathological tissue dedifferentiation associated with neoplasias, in particular during pancreatic acinar-to-ductal metaplasia, a process that involves transdifferentiation of adult acinar cells into ductal-like cells due to K-Ras oncogene expression. These findings place telomeres as important players in cellular plasticity both during in vivo reprogramming and in pathological conditions associated with increased plasticity, such as cancer.

Concepts: DNA, Gene, Gene expression, Cancer, Developmental biology, Stem cell, Cellular differentiation, Telomere

166

The rigorous characterization of distinct induced pluripotent stem cells (iPSC) derived from multiple reprogramming technologies, somatic sources, and donors is required to understand potential sources of variability and downstream potential. To achieve this goal, the Progenitor Cell Biology Consortium performed comprehensive experimental and genomic analyses of 58 iPSC from ten laboratories generated using a variety of reprogramming genes, vectors, and cells. Associated global molecular characterization studies identified functionally informative correlations in gene expression, DNA methylation, and/or copy-number variation among key developmental and oncogenic regulators as a result of donor, sex, line stability, reprogramming technology, and cell of origin. Furthermore, X-chromosome inactivation in PSC produced highly correlated differences in teratoma-lineage staining and regulator expression upon differentiation. All experimental results, and raw, processed, and metadata from these analyses, including powerful tools, are interactively accessible from a new online portal at https://www.synapse.org to serve as a reusable resource for the stem cell community.

Concepts: DNA, Gene, Genetics, Gene expression, Cell, Developmental biology, Stem cell, Cell biology

153

Stem cell-derived somatic cells represent an unlimited resource for basic and translational science. Although promising, there are significant hurdles that must be overcome. Our focus is on the generation of the major cell type of the human liver, the hepatocyte. Current protocols produce variable populations of hepatocytes that are the product of using undefined components in the differentiation process. This serves as a significant barrier to scale-up and application. To tackle this issue, we designed a defined differentiation process using recombinant laminin substrates to provide instruction. We demonstrate efficient hepatocyte specification, cell organization, and significant improvements in cell function and phenotype. This is driven in part by the suppression of unfavorable gene regulatory networks that control cell proliferation and migration, pluripotent stem cell self-renewal, and fibroblast and colon specification. We believe that this represents a significant advance, moving stem cell-based hepatocytes closer toward biomedical application.

Concepts: DNA, Developmental biology, Stem cell, Cell biology, Liver, Cellular differentiation, Glycogen, Hepatocyte

153

Fibrodysplasia ossificans progressiva (FOP) is a rare disease characterized by progressive ossification of soft tissues, for which there is no effective treatment. Mutations in the bone morphogenetic protein (BMP) type I receptor activin receptor-like kinase 2 (ACVR1/ALK2) are the main cause of FOP. We generated human induced pluripotent stem cells (hiPSCs) from FOP patients with the ALK2 R206H mutation. The mutant ALK2 gene changed differentiation efficiencies of hiPSCs into FOP bone-forming progenitors: endothelial cells (ECs) and pericytes. ECs from FOP hiPSCs showed reduced expression of vascular endothelial growth factor receptor 2 and could transform into mesenchymal cells through endothelial-mesenchymal transition. Increased mineralization of pericytes from FOP hiPSCs could be partly inhibited by the ALK2 kinase inhibitor LDN-212854. Thus, differentiated FOP hiPSCs recapitulate some aspects of the disease phenotype in vitro, and they could be instrumental in further elucidating underlying mechanisms of FOP and development of therapeutic drug candidates.

Concepts: DNA, Gene, Developmental biology, Stem cell, Stem cells, Cellular differentiation, Induced pluripotent stem cell, Fibrodysplasia ossificans progressiva

147

The temporal order of DNA replication is regulated during development and is highly correlated with gene expression, histone modifications and 3D genome architecture. We tracked changes in replication timing, gene expression, and chromatin conformation capture (Hi-C) A/B compartments over the first two cell cycles during differentiation of human embryonic stem cells to definitive endoderm. Remarkably, transcriptional programs were irreversibly reprogrammed within the first cell cycle and were largely but not universally coordinated with replication timing changes. Moreover, changes in A/B compartment and several histone modifications that normally correlate strongly with replication timing showed weak correlation during the early cell cycles of differentiation but showed increased alignment in later differentiation stages and in terminally differentiated cell lines. Thus, epigenetic cell fate transitions during early differentiation can occur despite dynamic and discordant changes in otherwise highly correlated genomic properties.

132

Understanding how epithelial progenitors within exocrine glands establish specific cell lineages and form complex functional secretory units is vital for organ regeneration. Here we identify the transcription factor Sox10 as essential for both the maintenance and differentiation of epithelial KIT+FGFR2b+ progenitors into secretory units, containing acinar, myoepithelial, and intercalated duct cells. The KIT/FGFR2b-Sox10 axis marks the earliest multi-potent and tissue-specific progenitors of exocrine glands. Genetic deletion of epithelial Sox10 leads to loss of secretory units, which reduces organ size and function, but the ductal tree is retained. Intriguingly, the remaining duct progenitors do not compensate for loss of Sox10 and lack plasticity to properly form secretory units. However, overexpression of Sox10 in these ductal progenitors enhances their plasticity toward KIT+ progenitors and induces differentiation into secretory units. Therefore, Sox10 controls plasticity and multi-potency of epithelial KIT+ cells in secretory organs, such as mammary, lacrimal, and salivary glands.

131

Hemophilia A (HA) is caused by genetic mutations in the blood coagulation factor VIII (FVIII) gene. Genome-editing approaches can be used to target the mutated site itself in patient-derived induced pluripotent stem cells (iPSCs). However, these approaches can be hampered by difficulty in preparing thousands of editing platforms for each corresponding variant found in HA patients. Here, we report a universal approach to correct the various mutations in HA patient iPSCs by the targeted insertion of the FVIII gene into the human H11 site via CRISPR/Cas9. We derived corrected clones from two types of patient iPSCs with frequencies of up to 64% and 66%, respectively, without detectable unwanted off-target mutations. Moreover, we demonstrated that endothelial cells differentiated from the corrected iPSCs successfully secreted functional protein. This strategy may provide a universal therapeutic method for correcting all genetic variants found in HA patients.

131

Inflammatory responses are known to facilitate tissue recovery following injury. However, the precise mechanisms that enhance lung alveolar regeneration remain unclear. Here, using an organoid-based screening assay, we find that interleukin-1 (IL-1) and tumor necrosis factor α (TNFα) enhance the proliferation of AEC2s while maintaining their differentiation capacity. Furthermore, we find that expression of IL-1β and TNFα are induced in the AEC2 niche following influenza-induced injury in vivo, and lineage tracing analysis revealed that surviving AEC2s around the damaged area contribute to alveolar regeneration. Through genetic and pharmacological modulation of multiple components of the IL-1-nuclear factor κB (NF-κB) signaling axis, we show that cell-intrinsic as well as stromal mediated IL-1 signaling are essential for AEC2 mediated lung regeneration. Taken together, we propose that the IL-1/TNFα-NF-κB signaling axis functions as a component of an inflammation-associated niche to regulate proliferation of surviving AEC2s and promote lung regeneration.

122

The blood-brain barrier (BBB) is composed of four cell populations, brain endothelial cells (BECs), pericytes, neurons, and astrocytes. Its role is to precisely regulate the microenvironment of the brain through selective substance crossing. Here we generated an in vitro model of the BBB by differentiating human induced pluripotent stem cells (hiPSCs) into all four populations. When the four hiPSC-derived populations were co-cultured, endothelial cells (ECs) were endowed with features consistent with BECs, including a high expression of nutrient transporters (CAT3, MFSD2A) and efflux transporters (ABCA1, BCRP, PGP, MRP5), and strong barrier function based on tight junctions. Neuron-derived Dll1, which activates Notch signaling in ECs, was essential for the BEC specification. We performed in vitro BBB permeability tests and assessed ten clinical drugs by nanoLC-MS/MS, finding a good correlation with the BBB permeability reported in previous cases. This technology should be useful for research on human BBB physiology, pathology, and drug development.

Concepts: Neuron, Brain, Developmental biology, Stem cell, Stem cells, Cell biology, Induced pluripotent stem cell, Blood-brain barrier