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BACKGROUND Humanized mouse models are still under development,and various protocols exist to improve human cell engraftment and function. METHODS Fourteen NOD/SCID/IL-2Rγnull (NSG) mice (4‒5 wk old) were conditioned with busulfan and injected with human umbilical cord blood (hUCB)-derived CD34(+) hematopoietic stem cells (HSC) via retro-orbital sinuses. The bone marrow (BM),spleen,and peripheral blood (PB) were analyzed 8 and 12 weeks after HSC transplantation. RESULTS Most of the NSG mice tolerated the regimen well. The percentage of hCD45(+) and CD19(+) cells rose significantly in a time-dependent manner. The median percentage of hCD45(+)cells in the BM was 55.5% at week 8,and 67.2% at week 12. The median percentage of hCD45(+) cells in the spleen at weeks 8 and 12 was 42% and 51%,respectively. The median percentage of hCD19(+) cells in BM at weeks 8 and 12 was 21.5% and 39%,respectively (P=0.04). Similarly,the median percentage of hCD19(+) cells in the spleen at weeks 8 and 12 was 10% and 24%,respectively (P=0.04). The percentage of hCD19(+) B cells in PB was 23% at week 12. At week 8,hCD3(+) T cells were barely detectable,while hCD7(+) was detected in the BM and spleen. The percentage of hCD3(+) T cells was 2‒3% at week 12 in the BM,spleen,and PB of humanized NSG mice. CONCLUSION We adopted a simplified protocol for establishing humanized NSG mice. We observed a higher engraftment rate of human CD45(+) cells than earlier studies without any significant toxicity. And human CD45(+) cell engraftment at week 8 was comparable to that of week 12. View Publication

Astrocytes are instrumental to major brain functions,including metabolic support,extracellular ion regulation,the shaping of excitatory signaling events and maintenance of synaptic glutamate homeostasis. Astrocyte dysfunction contributes to numerous developmental,psychiatric and neurodegenerative disorders. The generation of adult human fibroblast-derived induced pluripotent stem cells (iPSCs) has provided novel opportunities to study mechanisms of astrocyte dysfunction in human-derived cells. To overcome the difficulties of cell type heterogeneity during the differentiation process from iPSCs to astroglial cells (iPS astrocytes),we generated homogenous populations of iPS astrocytes using zinc-finger nuclease (ZFN) technology. Enhanced green fluorescent protein (eGFP) driven by the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter was inserted into the safe harbor adeno-associated virus integration site 1 (AAVS1) locus in disease and control-derived iPSCs. Astrocyte populations were enriched using Fluorescence Activated Cell Sorting (FACS) and after enrichment more than 99% of iPS astrocytes expressed mature astrocyte markers including GFAP,S100$\$,NFIA and ALDH1L1. In addition,mature pure GFP-iPS astrocytes exhibited a well-described functional astrocytic activity in vitro characterized by neuron-dependent regulation of glutamate transporters to regulate extracellular glutamate concentrations. Engraftment of GFP-iPS astrocytes into rat spinal cord grey matter confirmed in vivo cell survival and continued astrocytic maturation. In conclusion,the generation of GFAP::GFP-iPS astrocytes provides a powerful in vitro and in vivo tool for studying astrocyte biology and astrocyte-driven disease pathogenesis and therapy. View Publication

Differentiation of human pluripotent stem cells (hPSCs) into organ-specific subtypes offers an exciting avenue for the study of embryonic development and disease processes,for pharmacologic studies and as a potential resource for therapeutic transplant. To date,limited in vivo models exist for human intestine,all of which are dependent upon primary epithelial cultures or digested tissue from surgical biopsies that include mesenchymal cells transplanted on biodegradable scaffolds. Here,we generated human intestinal organoids (HIOs) produced in vitro from human embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs) that can engraft in vivo. These HIOs form mature human intestinal epithelium with intestinal stem cells contributing to the crypt-villus architecture and a laminated human mesenchyme,both supported by mouse vasculature ingrowth. In vivo transplantation resulted in marked expansion and maturation of the epithelium and mesenchyme,as demonstrated by differentiated intestinal cell lineages (enterocytes,goblet cells,Paneth cells,tuft cells and enteroendocrine cells),presence of functional brush-border enzymes (lactase,sucrase-isomaltase and dipeptidyl peptidase 4) and visible subepithelial and smooth muscle layers when compared with HIOs in vitro. Transplanted intestinal tissues demonstrated digestive functions as shown by permeability and peptide uptake studies. Furthermore,transplanted HIO-derived tissue was responsive to systemic signals from the host mouse following ileocecal resection,suggesting a role for circulating factors in the intestinal adaptive response. This model of the human small intestine may pave the way for studies of intestinal physiology,disease and translational studies. View Publication

The efficacy of donor HSCT is partly reduced as a result of slow post-transplantation immune recovery. In particular,T cell regeneration is generally delayed,resulting in high infection-related mortality in the first years post-transplantation. Adoptive transfer of in vitro-generated human T cell progenitors seems a promising approach to accelerate T cell recovery in immunocompromised patients. AA may enhance T cell proliferation and differentiation in a controlled,feeder-free environment containing Notch ligands and defined growth factors. Our experiments show a pivotal role for AA during human in vitro T cell development. The blocking of NOS diminished this effect,indicating a role for the citrulline/NO cycle. AA promotes the transition of proT1 to proT2 cells and of preT to DP T cells. Furthermore,the addition of AA to feeder cocultures resulted in development of DP and SP T cells,whereas without AA,a preT cell-stage arrest occurred. We conclude that neither DLL4-expressing feeder cells nor feeder cell conditioned media are required for generating DP T cells from CB and G-CSF-mobilized HSCs and that generation and proliferation of proT and DP T cells are greatly improved by AA. This technology could potentially be used to generate T cell progenitors for adoptive therapy. View Publication

BACKGROUND Whole-lung scaffolds can be created by perfusion decellularization of cadaveric donor lungs. The resulting matrices can then be recellularized to regenerate functional organs. This study evaluated the capacity of acellular lung scaffolds to support recellularization with lung progenitors derived from human induced pluripotent stem cells (iPSCs). METHODS Whole rat and human lungs were decellularized by constant-pressure perfusion with 0.1% sodium dodecyl sulfate solution. Resulting lung scaffolds were cryosectioned into slices or left intact. Human iPSCs were differentiated to definitive endoderm,anteriorized to a foregut fate,and then ventralized to a population expressing NK2 homeobox 1 (Nkx2.1). Cells were seeded onto slices and whole lungs,which were maintained under constant perfusion biomimetic culture. Lineage specification was assessed by quantitative polymerase chain reaction and immunofluorescent staining. Regenerated left lungs were transplanted in an orthotopic position. RESULTS Activin-A treatment,followed by transforming growth factor-$\$,induced differentiation of human iPSCs to anterior foregut endoderm as confirmed by forkhead box protein A2 (FOXA2),SRY (Sex Determining Region Y)-Box 17 (SOX17),and SOX2 expression. Cells cultured on decellularized lung slices demonstrated proliferation and lineage commitment after 5 days. Cells expressing Nkx2.1 were identified at 40% to 60% efficiency. Within whole-lung scaffolds and under perfusion culture,cells further upregulated Nkx2.1 expression. After orthotopic transplantation,grafts were perfused and ventilated by host vasculature and airways. CONCLUSIONS Decellularized lung matrix supports the culture and lineage commitment of human iPSC-derived lung progenitor cells. Whole-organ scaffolds and biomimetic culture enable coseeding of iPSC-derived endothelial and epithelial progenitors and enhance early lung fate. Orthotopic transplantation may enable further in vivo graft maturation. View Publication

Mesenchymal stem cells (MSCs) may be used as powerful tools for the repair and regeneration of damaged tissues. However,isolating tissue specific-derived MSCs may cause pain and increased infection rates in patients,and repetitive isolations may be required. To overcome these difficulties,we have examined alternative methods for MSC production. Here,we show that induced pluripotent stem cells (iPSCs) may be differentiated into mesenchymal stem cells (iMSCs) following exposure to SB431542. Purified iMSCs were administered to mdx mice to study skeletal muscle regeneration in a murine model of muscular dystrophy. Purified iMSCs displayed fibroblast-like morphology,formed three-dimensional spheroid structures,and expressed characteristic mesenchymal stem cell surface markers such as CD29,CD33,CD73,CD90,and CD105. Moreover,iMSCs were capable of differentiating into adipogenic,osteogenic,and chondrogenic lineages. Transplanting iMSC cells to tibialis anterior skeletal muscle tissue in mdx mice lowered oxidative damage as evidenced by a reduction in nitrotyrosine levels,and normal dystrophin expression levels were restored. This study demonstrates the therapeutic potential of purified iMSCs in skeletal muscle regeneration in mdx mice,and suggests that iPSCs are a viable alternate source for deriving MSCs as needed. textcopyright 2014 Elsevier Inc. View Publication

Teratoma formation,the standard in vivo pluripotency assay,is also frequently used as a tumorigenicity assay. A common concern in therapeutic stem cell applications is the tumorigenicity potential of a small number of cell impurities in the final product. Estimation of this small number is hampered by the inaccurate methodology of the tumorigenicity assay. Hence,a protocol for tumorigenicity assay that can deliver a defined number of cells,without error introduced by leakage or migration of cells is needed. In this study,we tested our modified transplantation method that allows for transplant of small numbers of pluripotent stem cells (PSCs) under the kidney capsule with minimal cell leakage. A glass capillary with a finely shaped tip and an attached mouth pipette was used to inject PSCs into the rodent kidney capsule. H9 embryonic and induced PSCs were tagged with Fluc and green fluorescence protein reporter genes and divided in different cell doses for transplantation. Bioluminescence imaging (BLI) on the day of surgery showed that the cell signal was confined to the kidney and signal intensity correlated with increasing transplant cell numbers. The overall cell leakage rate was 17% and the rodent survival rate was 96%. Teratoma formation was observed in rodents transplanted with cell numbers between 1 × 10(5)-2 × 10(6). We conclude that this modified procedure for transplanting PSCs under the kidney capsule allows for transplantation of a defined number of PSCs with significant reduction of error associated with cell leakage from the transplant site. View Publication

Recent clinical studies suggest that adoptive transfer of donor-derived natural killer (NK) cells may improve clinical outcome in hematological malignancies and some solid tumors by direct anti-tumor effects as well as by reduction of graft versus host disease (GVHD). NK cells have also been shown to enhance transplant engraftment during allogeneic hematopoietic stem cell transplantation (HSCT) for hematological malignancies. The limited ex vivo expansion potential of NK cells from peripheral blood (PB) or umbilical cord blood (UCB) has however restricted their therapeutic potential. Here we define methods to efficiently generate NK cells from donor-matched,full-term human placenta perfusate (termed Human Placenta-Derived Stem Cell,HPDSC) and UCB. Following isolation from cryopreserved donor-matched HPDSC and UCB units,CD56+CD3- placenta-derived NK cells,termed pNK cells,were expanded in culture for up to 3 weeks to yield an average of 1.2 billion cells per donor that were textgreater80% CD56+CD3-,comparable to doses previously utilized in clinical applications. Ex vivo-expanded pNK cells exhibited a marked increase in anti-tumor cytolytic activity coinciding with the significantly increased expression of NKG2D,NKp46,and NKp44 (p textless 0.001,p textless 0.001,and p textless 0.05,respectively). Strong cytolytic activity was observed against a wide range of tumor cell lines in vitro. pNK cells display a distinct microRNA (miRNA) expression profile,immunophenotype,and greater anti-tumor capacity in vitro compared to PB NK cells used in recent clinical trials. With further development,pNK may represent a novel and effective cellular immunotherapy for patients with high clinical needs and few other therapeutic options. View Publication

CREB-binding protein (CREBBP) is important for the cell-autonomous regulation of hematopoiesis,including the stem cell compartment. In the present study,we show that CREBBP plays an equally pivotal role in microenvironment-mediated regulation of hematopoiesis. We found that the BM microenvironment of Crebbp(+/-) mice was unable to properly maintain the immature stem cell and progenitor cell pools. Instead,it stimulates myeloid differentiation,which progresses into a myeloproliferation phenotype. Alterations in the BM microenvironment resulting from haploinsufficiency of Crebbp included a marked decrease in trabecular bone that was predominantly caused by increased osteoclastogenesis. Although CFU-fibroblast (CFU-F) and total osteoblast numbers were decreased,the bone formation rate was similar to that found in wild-type mice. At the molecular level,we found that the known hematopoietic modulators matrix metallopeptidase-9 (MMP9) and kit ligand (KITL) were decreased with heterozygous levels of Crebbp. Lastly,potentially important regulatory proteins,endothelial cell adhesion molecule 1 (ESAM1) and cadherin 5 (CDH5),were increased on Crebbp(+/-) endothelial cells. Our findings reveal that a full dose of Crebbp is essential in the BM microenvironment to maintain proper hematopoiesis and to prevent excessive myeloproliferation. View Publication