Reprogramming Media Research Articles

Human chemically-derived hepatic progenitors (hCdHs) as a source of liver organoid generation: Application in regenerative medicine, disease modeling, and toxicology testing

Background & aimsSeveral types of human stem cells from embryonic (ESCs) and induced pluripotent (iPSCs) to adult tissue-specific stem cells are commonly used to generate 3D liver organoids for modeling tissue physiology and disease. We have recently established a protocol for direct conversion of primary human hepatocytes (hPHs) from healthy donor livers into bipotent progenitor cells (hCdHs). Here we extended this culture system to generate hCdH-derived liver organoids for diverse biomedical applications. MethodsTo obtain hCdHs, hPHs were cultured in reprogramming medium containing A83-01 and CHIR99021 for 7 days. Liver organoids were established from hCdHs (hCdHOs) and human liver cells (hLOs) using the same donor livers for direct comparison, as well as from hiPSCs. Organoid properties were analyzed by standard in vitro assays. Molecular changes were determined by RT-qPCR and RNA-seq. Clinical relevance was evaluated by transplantation into FRG mice, modeling of alcohol-related liver disease (ARLD), and in vitro drug-toxicity tests. ResultshCdHs were clonally expanded as organoid cultures with low variability between starting hCdH lines. Similar to the hLOs, hCdHOs stably maintained stem cell phenotype based on accepted criteria. However, hCdHOs had an advantage over hLOs in terms of EpCAM expression, efficiency of organoid generation and capacity for directed hepatic differentiation as judged by molecular profiling, albumin secretion, glycogen accumulation, and CYP450 activities. Accordingly, FRG mice transplanted with hCdHOs survived longer than mice injected with hLOs. When exposed to ethanol, hCdHOs developed stronger ARLD phenotype than hLOs as evidenced by transcriptional profiling, lipid accumulation and mitochondrial dysfunction. In drug-induced injury assays in vitro, hCdHOs showed a similar or higher sensitivity response than hPHs. ConclusionhCdHOs provide a novel patient-specific stem cell-based platform for regenerative medicine, toxicology testing and modeling liver diseases.

Directly reprogrammed natural killer cells for cancer immunotherapy.

Efficacious and accessible sources of natural killer (NK) cells would widen their use as immunotherapeutics, particularly for solid cancers. Here, we show that human somatic cells can be directly reprogrammed into NK cells with a CD56brightCD16bright phenotype using pluripotency transcription factors and an optimized reprogramming medium. The directly reprogrammed NK cells have strong innate-adaptive immunomodulatory activity and are highly potent against a wide range of cancer cells, including difficult-to-treat solid cancers and cancer stem cells. Both directly reprogrammed NK cells bearing a cancer-specific chimeric antigen receptor and reprogrammed NK cells in combination with antibodies competent for antibody-dependent cell-mediated cytotoxicity led to selective anticancer effects with augmented potency. The direct reprogramming of human somatic cells into NK cells is amenable to the production of autologous and allogeneic NK cells, and will facilitate the design and testing of cancer immunotherapies and combination therapies.

The stemness of hepatocytes is maintained by high levels of lipopolysaccharide via YAP1 activation

BackgroundThe liver possesses a powerful regeneration ability, which is correlated with the stemness of hepatocytes in the portal vein (PV). However, the mechanism underlying the maintenance of hepatocyte stemness has not been elucidated. Here, we hypothesized that high levels of lipopolysaccharide from the portal vein might maintain the stemness of hepatocytes in the PV area.MethodsFirst, we examined the location of hepatic stem cells and the concentration of lipopolysaccharide (LPS) in the portal vein and inferior vena cava. Then, we assessed the effect of LPS on stemness maintenance in mice by using antibiotics to eliminate LPS and knocking out the LPS receptor, TLR4. In vitro, the effect of LPS on the stemness of hepatocytes was investigated by colony and sphere formation assays and assessment of pluripotent and stem cell marker expression. Furthermore, we studied the mechanism by which LPS regulates the stemness of hepatocytes. Finally, we ligated the portal vein branch to further verify the effect of LPS.ResultsWe found that a high level of LPS from the portal vein was correlated with the location of hepatic stem cells in the PV area, and elimination of LPS by antibiotics inhibited the expression of the stemness marker. LPS promoted colony and sphere formation and induced the upregulation of pluripotent and stem cell markers in AML12 cells. Furthermore, in the reprogramming medium, LPS facilitated the dedifferentiation of mature hepatocytes into hepatic progenitor-like cells, which exhibited a bipotent differentiation capacity in vivo and in vitro. Mechanistically, LPS bound TLR4 to regulate stemness of hepatocytes via the activation of YAP1 signaling, and blockade of YAP1 abolished the LPS-induced cell stemness and upregulation of pluripotent markers.ConclusionsOur study implies a correlation between LPS/TLR4/YAP1 signaling and cell stemness, and LPS was shown to be involved in stemness maintenance of hepatocytes in the PV area. LPS might be used to induce the dedifferentiation of mature hepatocytes into progenitor-like cells for repair of liver injury.

Generation of Hepatic Progenitor Cells from the Primary Hepatocytes of Nonhuman Primates Using Small Molecules.

Since primates have more biological similarities to humans than do other animals, they are a valuable resource in various field of research, including biomedicine, regenerative medicine, and drug discovery. However, there remain limitations to maintenance and expansion of primary hepatocytes derived from nonhuman primates. To overcome these limitations, we developed a novel culture system for primate cells. Primary hepatocytes from Macaca fascicularis (mf-PHs) were isolated from hepatectomized liver. To generate chemically derived hepatic progenitor cells (mf-CdHs), mf-PHs were cultured with reprogramming medium containing A83-01, CHIR99021, and hepatocyte growth factor (HGF). The bi-potent differentiation capacity of mf-CdHs into hepatocytes and biliary epithelial cells was confirmed by treatment with hepatic differentiation medium (HDM) and cholangiocytic differentiation medium (CDM), respectively. mf-PHs cultured with reprogramming medium showed rapid proliferation capacity in vitro and expressed progenitor-specific markers. Moreover, when cultured in HDM, these progenitor cells stably differentiated into hepatocyte-like cells expressing the mature hepatic markers. On the other hand, when cultured in CDM, the differentiated biliary epithelial cells expressed mature cholangiocyte characteristics. The results of the present study demonstrate that we successfully induced the formation of hepatic progenitor cells from mf-PHs by culturing them with a combination of small molecules, including growth factors. These results offer a means of expanding nonhuman primate hepatocytes without genetic manipulation for cellular resource, preclinical applications and regenerative medicine for the liver.

Highly efficient induced pluripotent stem cell reprogramming of cryopreserved lymphoblastoid cell lines.

Tissue culture based in-vitro experimental modeling of human inherited disorders provides insight into the cellular and molecular mechanisms involved and the underlying genetic component influencing the disease phenotype. The breakthrough development of induced pluripotent stem cell (iPSC) technology represents a quantum leap in experimental modeling of human diseases, providing investigators with a self-renewing and thus unlimited source of pluripotent cells for targeted differentiation into functionally relevant disease specific tissue/cell types. The existing rich bio-resource of Epstein-Barr virus (EBV) immortalized lymphoblastoid cell line (LCL) repositories generated from a wide array of patients in genetic and epidemiological studies worldwide, many of them with extensive genotypic, genomic and phenotypic data already existing, provides a great opportunity to reprogram iPSCs from any of these LCL donors in the context of their own genetic identity for disease modeling and disease gene identification. However, due to the low reprogramming efficiency and poor success rate of LCL to iPSC reprogramming, these LCL resources remain severely underused for this purpose. Here, we detailed step-by-step instructions to perform our highly efficient LCL-to-iPSC reprogramming protocol using EBNA1/OriP episomal plasmids encoding pluripotency transcription factors (i.e., OCT3/4, SOX2, KLF4, L-MYC, and LIN28), mouse p53DD (p53 carboxy-terminal dominant-negative fragment) and commercially available reprogramming media. We achieved a consistently high reprogramming efficiency and 100% success rate (> 200 reprogrammed iPSC lines) using this protocol.

CXCR2 Ligands and mTOR Activation Enhance Reprogramming of Human Somatic Cells to Pluripotent Stem Cells.

Induced pluripotent stem cell (iPSC) technology has great promise in regenerative medicine and disease modeling. In this study, we show that human placenta-derived cell conditioned medium stimulates chemokine (C-X-C motif) receptor 2 (CXCR2) in human somatic cells ectopically expressing the pluripotency-associated transcription factors Oct4, Sox2, Klf4, and cMyc (OSKM), leading to mechanistic target of rapamycin (mTOR) activation. This causes an increase in endogenous cMYC levels and a decrease in autophagy, thereby enhancing the reprogramming efficiency of human somatic cells into iPSCs. These findings were reproduced when human somatic cells after OSKM transduction were cultured in a widely used reprogramming medium (mTeSR) supplemented with CXCR2 ligands interleukin-8 and growth-related oncogene α or an mTOR activator (MHY1485). To our knowledge, this is the first report demonstrating that mTOR activation in human somatic cells with ectopic OSKM expression significantly enhances the production of iPSCs. Our results support the development of convenient protocols for iPSC generation and further our understanding of somatic cell reprogramming.

214 Different pluripotency maintenance supplements affect the reprogramming process and pluripotency state of bovine-induced pluripotent stem cells

After the emergence of induced cell reprogramming, achieved through the addition of Yamanaka transcription factors (Oct4, Sox2, Klf4, and cMyc; OSKM) to somatic cells, the number of studies regarding induction and maintenance of pluripotency has increased greatly. The success of bovine iPSCs (biPSCs) was first described by Summer et al. (2011 J. Anim. Sci. 89, 2708-2716; https://doi.org/10.2527/jas.2010-3666); however, investigations on the pluripotent state of biPSCs are still needed because different protocols and characterisation profiles have since been used. The aim of this study was to produce biPSC lines supplemented with different pluripotency maintenance agents to improve self-renewal and pluripotency maintenance. For that, bovine fetal (50 days) fibroblasts (3×104) were transduced with lentivirus harbouring mouse OSKM transcription factors. The cells were further cultured in reprogramming medium (Dulbecco's modified Eagle's medium/F12 KO and 20% KSR (knockout serum replacement)) supplemented with basic fibroblast growth factor (bFGF), leukemia inhibitory factor (LIF), bFGF+2i or LIF+2i (where 2i inhibitors are PD0325901 and CHIR99021). The capacity for cell reprogramming was analysed by colony formation and maintenance after manually and enzymatic passaging and alkaline phosphatase (AP) activity detection; additionally, pluripotency state was assessed by reverse transcription (RT)-PCR (pluripotency biomarkers: OCT4, NANOG, and SOX2; naïve state: STELLA, LIFr, and ESRRb; primed state: OTX2 and FGF5; and mouse (m)OSKM and invitro differentiation assay (embryoid body formation). Statistical analysis was performed using the JMP software (SAS Institute Inc.). All treatments were successful at generating colonies after 28 days of mOSKM transduction, with 32 colonies in bFGF (0.53% efficiency), 21 colonies in bFGF+2i (0.35% efficiency), 5 colonies in LIF (0.08% efficiency), and 3 colonies in LIF+2i (0.05% efficiency) treatments/groups. As an initial pluripotency test, all colonies were positive for AP activity at passage 3. The colonies were cultured for at least 25 passages (±200 days) except for those from the LIF+2i treatment, which were not able to remain viable after 15 passages. Gene expression analysis of the pluripotency (naïve and primed) biomarkers in biPSCs by RT-PCR revealed that colonies from the bFGF treatment were upregulated in NANOG, OCT4, (pluripotency biomarkers), and STELLA (naïve biomarker) (P<0.05) compared with bFGF+2i and LIF groups. There were no differences in expression of SOX2 (pluripotency biomarker gene) and naïve/primed biomarkers (OXT2, LIFr, and ESRRb) (P>0.05). Additionally, the relative abundance of mOSKM was not different between groups (P>0.05). For further pluripotency analysis, biPS colonies were tested for the invitro differentiation assay, and all colonies tested were able to form embryoid bodies. In conclusion, bovine fetal fibroblasts were successfully reprogrammed when using OSKM in all medium tested; however, LIF+2i treatment did not grow beyond 25 passages. Further tests should be performed to determine the pluripotency status of these biPSCs. We acknowledge FAPESP for funding (grant nos. 2012/50533-2, 2015/26816-5, and 2016/16841-2).

Retracted] Generation and characterization of induced pluripotent stem cells from guinea pig fetal fibroblasts.

The authors wish to retract their article entitled "Generation and characterization of induced pluripotent stem cells from guinea pig fetal fibroblasts" published in Molecular Medicine Reports15, 3690‑3698, 2017. Following the publication of this article, the authors noted that the description of the reprogramming method and cell cultured conditions in the article was inconsistent with the experimental facts, due to their oversight and personnel issues in terms of who performed the experimental work and who wrote up the paper. Some of the experimental approaches were wrongly described in the Materials and methods section. Namely, the feeder cells which were used in this reprogramming were mouse embryonic fibroblasts, not guinea fibroblast cells, as was reported; the reprogramming medium contained 15% knockout serum replacement; the culture medium contained 10% ESC qualified fetal bovine serum and 10% knockout serum replacement; and 293T cells were transfected using the Quick Shuttle‑293 system. Due to the authors' oversight, Figs2A and C, and Fig.3 on p.3,694 do not match with the textual description. In view of these serious errors, which the authors are not able to rectify, they have requested that this article be retracted from the publication. All the named authors agree to this retraction. The authors regret any inconvenience to the readers that this retraction will cause.

Generation of Human Primordial Germ Cell-like Cells at the Surface of Embryoid Bodies from Primed-pluripotency Induced Pluripotent Stem Cells.

Primordial germ cells (PGCs) are common precursors of all germline cells. In mouse embryos, a founding population of ~40 PGCs are induced from pluripotent epiblast cells by orchestrated exposures to cytokines, including bone morphogenetic protein 4 (Bmp4). In human embryos, the earliest PGCs have been identified on the endodermal wall of yolk sac around the end of the 3rd week of gestation, but little is known about the process of human PGC specification and their early development. To circumvent the technical and ethical barriers of studying human embryonic PGCs, surrogate cell culture models have been recently generated from pluripotent stem cells. Here, we describe a 13-day protocol for robust production of human PGC-Like Cells (hPGCLCs). Human induced pluripotent stem cells (hiPSCs) maintained in the primed pluripotency state are incubated in the 4i naïve reprogramming medium for 48 hours, dissociated to single cells, and packed into microwells. Prolonged maintenance of hiPSCs in the naïve pluripotency state causes significant chromosomal aberrations and should be avoided. hiPSCs in the microwells are maintained for an additional 24 hours in the 4i medium to form embryoid bodies (EBs), which are then cultured in low-adherence plasticware under a rocking condition in the hPGCLC induction medium containing a high concentration of recombinant human BMP4. EBs are further cultured for up to 8 days in the rocking, non-adherent condition to obtain maximum yields of hPGCLCs. By immunohistochemistry, hPGCLCs are readily detected as cells strongly expressing OCT4 in almost all EBs exclusively on their surface. When EBs are enzymatically dissociated and subjected to FACS enrichment, hPGCLCs can be collected as CD38+ cells with up to 40-45% yield.

Relevance of iPSC-derived human PGC-like cells at the surface of embryoid bodies to prechemotaxis migrating PGCs

Pluripotent stem cell-derived human primordial germ cell-like cells (hPGCLCs) provide important opportunities to study primordial germ cells (PGCs). We robustly produced CD38+ hPGCLCs [∼43% of FACS-sorted embryoid body (EB) cells] from primed-state induced pluripotent stem cells (iPSCs) after a 72-hour transient incubation in the four chemical inhibitors (4i)-naïve reprogramming medium and showed transcriptional consistency of our hPGCLCs with hPGCLCs generated in previous studies using various and distinct protocols. Both CD38+ hPGCLCs and CD38- EB cells significantly expressed PRDM1 and TFAP2C, although PRDM1 mRNA in CD38- cells lacked the 3'-UTR harboring miRNA binding sites regulating mRNA stability. Genes up-regulated in hPGCLCs were enriched for cell migration genes, and their promoters were enriched for the binding motifs of TFAP2 (which was identified in promoters of T, NANOS3, and SOX17) and the RREB-1 cell adhesion regulator. In EBs, hPGCLCs were identified exclusively in the outermost surface monolayer as dispersed cells or cell aggregates with strong and specific expression of POU5F1/OCT4 protein. Time-lapse live cell imaging revealed active migration of hPGCLCs on Matrigel. Whereas all hPGCLCs strongly expressed the CXCR4 chemotaxis receptor, its ligand CXCL12/SDF1 was not significantly expressed in the whole EBs. Exposure of hPGCLCs to CXCL12/SDF1 induced cell migration genes and antiapoptosis genes. Thus, our study shows that transcriptionally consistent hPGCLCs can be readily produced from hiPSCs after transition of their pluripotency from the primed state using various methods and that hPGCLCs resemble the early-stage PGCs randomly migrating in the midline region of human embryos before initiation of the CXCL12/SDF1-guided chemotaxis.

Selenium Augments microRNA Directed Reprogramming of Fibroblasts to Cardiomyocytes via Nanog.

We have recently shown that a combination of microRNAs, miR combo, can directly reprogram cardiac fibroblasts into functional cardiomyocytes in vitro and in vivo. However, direct reprogramming strategies are inefficient and slow. Moving towards the eventual goal of clinical application it is necessary to develop new methodologies to overcome these limitations. Here, we report the identification of a specific media composition, reprogramming media (RM), which augmented the effect of miR combo by 5–15-fold depending upon the cardiac marker tested. RM alone was sufficient to strongly induce cardiac gene and protein expression in neonatal tail-tip as well as cardiac fibroblasts. Expression of pluripotency markers Nanog, Oct4, Sox2, and Klf4 was significantly enhanced by RM, with miR combo augmenting the effect further. Knockdown of Nanog by siRNA inhibited the effect of RM on cardiac gene expression. Removal of insulin-transferrin-selenium completely inhibited the effect of reprogramming media upon cardiac gene expression and the addition of selenium to standard culture media recapitulated the effects of RM. Moreover, selenium enhanced the reprogramming efficiency of miR combo.

Utility of Lymphoblastoid Cell Lines for Induced Pluripotent Stem Cell Generation.

A large number of EBV immortalized LCLs have been generated and maintained in genetic/epidemiological studies as a perpetual source of DNA and as a surrogate in vitro cell model. Recent successes in reprograming LCLs into iPSCs have paved the way for generating more relevant in vitro disease models using this existing bioresource. However, the overall reprogramming efficiency and success rate remain poor and very little is known about the mechanistic changes that take place at the transcriptome and cellular functional level during LCL-to-iPSC reprogramming. Here, we report a new optimized LCL-to-iPSC reprogramming protocol using episomal plasmids encoding pluripotency transcription factors and mouse p53DD (p53 carboxy-terminal dominant-negative fragment) and commercially available reprogramming media. We achieved a consistently high reprogramming efficiency and 100% success rate using this optimized protocol. Further, we investigated the transcriptional changes in mRNA and miRNA levels, using FC-abs ≥ 2.0 and FDR ≤ 0.05 cutoffs; 5,228 mRNAs and 77 miRNAs were differentially expressed during LCL-to-iPSC reprogramming. The functional enrichment analysis of the upregulated genes and activation of human pluripotency pathways in the reprogrammed iPSCs showed that the generated iPSCs possess transcriptional and functional profiles very similar to those of human ESCs.

Generation of clinical-grade human induced pluripotent stem cells in Xeno-free conditions.

IntroductionHuman induced pluripotent stem cells (hiPSCs) are considered as one of the most promising seed cell sources in regenerative medicine. Now hiPSC-based clinical trials are underway. To ensure clinical safety, cells used in clinical trials or therapies should be generated under GMP conditions, and with Xeno-free culture media to avoid possible side effects like immune rejection that induced by the Xeno reagents. However, up to now there are no reports for hiPSC lines developed completely under GMP conditions using Xeno-free reagents.MethodsClinical-grade human foreskin fibroblast (HFF) cells used as feeder cells and parental cells of the clinical-grade hiPSCs were isolated from human foreskin tissues and cultured in Xeno-free media. Clinical-grade hiPSCs were derived by integration-free Sendai virus-based reprogramming kit in Xeno-free pluriton™ reprogramming medium or X medium. Neural cells and cardiomyocytes differentiation were conducted following a series of spatial and temporal specific signals induction according to the corresponding lineage development signals. Biological safety evaluation of the clinical-grade HFF cells and hiPSCs were conducted following the guidance of the “Pharmacopoeia of the People's Republic of China, Edition 2010, Volume III”.ResultsWe have successfully derived several integration-free clinical-grade hiPSC lines under GMP-controlled conditions and with Xeno-free reagents culture media in line with the current guidance of international and national evaluation criteria. As for the source of hiPSCs and feeder cells, biological safety evaluation of the HFF cells have been strictly reviewed by the National Institutes for Food and Drug Control (NIFDC). The hiPSC lines are pluripotent and have passed the safety evaluation. Moreover, one of the randomly selected hiPSC lines was capable of differentiating into functional neural cells and cardiomyocytes in Xeno-free culture media.ConclusionThe clinical-grade hiPSC lines therefore could be valuable sources for future hiPSC-based clinical trials or therapies and for drug screening.Electronic supplementary materialThe online version of this article (doi:10.1186/s13287-015-0206-y) contains supplementary material, which is available to authorized users.

Abstract 4073: Efficient conditional reprogramming of differentiated prostate cancer cells back to a stem cell-like state with increased aggressive properties

Abstract Androgen receptor- (AR-) expressing prostate cancer (PCa) cell lines can transdifferentiate to neuro-ectodermal cell lineages under androgen deprivation. We have proposed that this transdifferentiation is mediated by initial regression to an unstable cancer stem cell-like (CSCL) intermediate state and we have developed a serum- and androgen-free custom cell culture medium that now allows us to efficiently reprogram PCa cells to this CSCL state and expand them for characterization. Exposure of adherent cultures of parental LNCaP, VCaP, LAPC4 or CWR22rv1 cells to the reprogramming medium induced a rapid and efficient (>67%) morphological change of plated cells to smaller, rounded cells with large nuclei and prominent nucleoli that grow in 3-dimensions. Following transfer of the reprogrammed cells they, thereafter, grow as cell rosettes that will form larger spheroids. Analysis of changes in gene expression by microarray gene expression profiling or immunohistochemistry (IHC) showed a remarkable overexpression of stem cell genes in the reprogrammed cells and a change in cell surface CD protein expression that resembles neural stem cells. Reprogramming drastically reduced expression of AR RNA and protein in all cell lines. Once reprogrammed, the CSCLs have significantly higher tumor-initiating capacity based upon tumors formed from cell serial dilutions xenografted into intact or castrated male nude mice. In vitro, reprogrammed cells were significantly more resistant to the anti-androgen enzalutamide and to hypoxia compared to parentals. By placing CSCLs into specific differentiation mediums, we could differentiate them back into neural-, oligodendrocyte-, glia- or osteoblast-like cells based upon induced expression of lineage-specific RNAs/proteins or return them to prostate-like cells (that re-express AR) by supplementing them with serum and androgen. Reprogrammed cells have an EMT phenotype based on increased expression of EMT-related genes and significantly increased invasiveness in in vitro and in vivo models. Comparison of gene expression changes acquired by reprogrammed CSCLs amongst the different cell models revealed a shared set of 65 over-/under-expressed genes (≥1.8-fold) between them. Finally, we have found that growth of parental LNCaP cells in androgen-deprived or enzalutamide-supplemented (serum-containing) growth medium increased the population of cells bearing CSCL surface CD stem markers. In summary, our studies show that commonly used PCa cell lines have the ability to efficiently transition between a differentiated and a CSCL state in an appropriate microenvironment that is depleted of androgens. While in the CSCL state, these cells show increased invasiveness, increased resistance to hormonal therapeutics and a propensity to transdifferentiate to alternate cell lineages under appropriate stimulation. Citation Format: Josselin Caradec, Amy A. Lubik, Mannan Nouri, Na Li, Manuel Altimarano-Dimas, Jennifer Bishop, Mani Moniri, Down Cochrane, Martin Gleave, Ralph Buttyan. Efficient conditional reprogramming of differentiated prostate cancer cells back to a stem cell-like state with increased aggressive properties. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4073. doi:10.1158/1538-7445.AM2015-4073

Acquisition of pluripotency through continued environmental influence on OCT4-induced plastic human fibroblasts

The combination of OCT4 expression and short-term exposure to reprogramming media induces a state of transcriptional plasticity in human fibroblasts, capable of responding to changes in the extracellular environment that facilitate direct cell fate conversion toward lineage specific progenitors. Here we reveal that continued exposure of OCT4-induced plastic human fibroblasts to reprogramming media (RM) is sufficient to induce pluripotency. OCT4-derived induced pluripotent stem cell (iPSCOCT4) colonies emerged after prolonged culture in RM, and formed independently of lineage specific progenitors. Human iPSCOCT4 are morphologically indistinguishable from conventionally derived iPSCs and express core proteins involved in maintenance of pluripotency. iPSCOCT4 display in vivo functional pluripotency as measured by teratoma formation consisting of the three germ layers, and are capable of targeted in vitro differentiation. Our study indicates that acquisition of pluripotency is one of multiple cell fate choices that can be facilitated through environmental stimulation of OCT4-induced plasticity, and suggests the role of other reprogramming factors to induce pluripotency can be substituted by prolonged culture of plastic fibroblasts.

274. Expansion and Conversion of Patient-Derived Human Gallbladder Cells Into Insulin-Producing Pancreatic Endocrine-Like Type Cells

Islet transplantation is an efficacious therapeutic option for T1D, but, supply of donor pancreata does not meet the demand. Variable successes in generating glucose-responsive insulin-producing beta-like cells from pluripotent and differentiated cells have been reported. We report on genetic reprogramming of highly expandable patient-derived human gallbladder cells (GBCs) to produce insulin for autologous transplant. Using feeder-free and feeder-type culture methods, we expanded GBCs in vitro in the order of 10^8 total cells after 4 passages starting from 10^4 GBCs. Cultures can be maintained for at least 15 passages, albeit with slowdown in growth. Transcriptome profiling revealed GBCs to be deficient in factors important for beta-cell development, specification, and maintenance such as NEUROG3, MAFA, NKX6-1, NKX2-2, PAX4, PAX6, NEUROD1, INSM1, RFX6, GCK, and INS. MNX1 and PDX1 are moderately expressed in cultures but at significantly lower levels found in beta-cells. Viral transduction of PDX1, MAFA, and NEUROG3 (PNM) induced expression of INS at 1/10,000th compared to that of human islet cells. Transduced GBCs began to show morphological changes from a monolayer into 3D clusters as early as 2 days after transduction. Retinoic acid, GLP-1, FGF10, DAPT, T3, Alk5 inhibitor, and B27 in the reprogramming medium and the addition of PAX6 to PNM transduction highly improved both INS and NKX6-1 induction reaching 10% of islet cells. These reprogrammed GBCs also express high levels of NEUROD1, NKX2-2, RFX6, PAX4, MAFB, HOPX, SST, GHRL, CHGA, TMEM27, SYP, KCNJ11, and ABCC8 comparable to islet cells. Average transduction efficiency was 50% yielding 9% C-peptide+ cells by immunostaining. Cellular C-peptide content was equivalent to 0.3% of that of purified beta-cells. At best, we observed 5-fold increase in C-peptide concentration in response to high glucose. We further enriched for INS+ reprogrammed GBCs using a cell surface mAb (HPi1) shown to isolate human pancreatic islet cells. Immunolabeling showed that reprogramming significantly increased the percentage of Hpi1+ GBCs. RT-qPCR of Hpi1+ GBCs showed greater than 1000-fold enrichment in gene expression of INS, NKX6-1, and PCSK1 compared to Hpi1- cells. Likewise, we observed greater than 100-fold enrichment for NEUROD1, SST, GHRL, and RFX6. In addition, we saw significant increase in reprogramming efficiency by adding an isoxazole to the reprogramming medium resulting to 10-fold higher INS expression, 2.5-fold increase in the frequency of C-peptide+ cells, and significant drop in SST and GHRL expression. Reprogrammed GBCs can engraft, survive, and produce C-peptide for at least 2 weeks in under the kidney capsule, mammary fat pad, and dorsal subcutaneous fat in NSG mice. Transplant experiments in diabetic mice are ongoing. In summary, we have transdifferentiated patient-derived adult GBCs into beta-like cells ex vivo, thus showing that GBCs are potential replacement sources of autologous insulin-producing cells.

Inducing pluripotency in vitro: recent advances and highlights in induced pluripotent stem cells generation and pluripotency reprogramming.

Induced pluripotent stem cells (iPSCs) are considered patient-specific counterparts of embryonic stem cells as they originate from somatic cells after forced expression of pluripotency reprogramming factors Oct4, Sox2, Klf4 and c-Myc. iPSCs offer unprecedented opportunity for personalized cell therapies in regenerative medicine. In recent years, iPSC technology has undergone substantial improvement to overcome slow and inefficient reprogramming protocols, and to ensure clinical-grade iPSCs and their functional derivatives. Recent developments in iPSC technology include better reprogramming methods employing novel delivery systems such as non-integrating viral and non-viral vectors, and characterization of alternative reprogramming factors. Concurrently, small chemical molecules (inhibitors of specific signalling or epigenetic regulators) have become crucial to iPSC reprogramming; they have the ability to replace putative reprogramming factors and boost reprogramming processes. Moreover, common dietary supplements, such as vitamin C and antioxidants, when introduced into reprogramming media, have been found to improve genomic and epigenomic profiles of iPSCs. In this article, we review the most recent advances in the iPSC field and potent application of iPSCs, in terms of cell therapy and tissue engineering.

Molecular evidence for OCT4-induced plasticity in adult human fibroblasts required for direct cell fate conversion to lineage specific progenitors.

Here we characterize the molecular and biological requirements for OCT4 plasticity induction in human skin derived fibroblasts (hFibs) that allows direct conversion of cell fate without iPSC formation. Our results indicate that adult hFibs not only require OCT4 but also short-term exposure to reprogramming media (RM) to successfully undergo direct conversion to early hematopoietic and neural progenitor fates. RM was found to be essential in this process and allowed for unique changes in global gene expression specific to the combined effects of OCT4 and treatment with reprogramming media to establish a plastic state. This molecular state of hFib plasticity was distinct from transient expression of a full complement of iPSC reprogramming factors consistent with a lack in molecular hallmarks of iPSC formation. Human Fib-derived OCT4 plastic cells display elevated levels of developmentally related genes associated with multiple lineages, but not those associated with pluripotency. In response to changes in the extracellular environment, plastic OCT4-expressing hFibs further activate genes involved in hematopoietic as well as tripotent neural progenitor biology that allow cell fate conversion. Our study provides a working definition of hFib-induced plasticity using OCT4 and a deconvoluted system to elucidate the process of direct cell fate reprogramming.

Generation of rat-induced pluripotent stem cells: Reprogramming and culture medium

The rat represents an animal model highly attractive for studying pharmacology, physiology, aging, cardiovascular diseases, etc., that in many aspects is more adequate than the mouse model. Derivation of induced pluripotent stem cells from rats (riPS) opens the opportunity for gene targeting in specific rat strains, as well as for the development of new protocols for the treatment of different degenerative diseases. Here we report an improved protocol for riPS cell generation, which is based on lentivirus delivery of reprogramming factors with their subsequent excision from the genome, application of serum-free media and chemical inhibitors MEK and GSK. We compared various conditions for riPS cell derivation, analyzed the cell karyotype, and assessed the pluripotency of the established cells. These data may prompt further iPS cell-based gene targeting in rat, as well as the development of iPS-based cell therapy, using this animal model.