技术资料

Objective: Human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) constitute unique sources of pluripotent cells,although the molecular mechanisms involved in their differentiation into specific lineages are just beginning to be defined. Here we evaluated the ability of MEDII (medium conditioned by HepG2 cells,a human hepatocarcinoma cell line) to selectively enhance generation of mesodermal derivatives,including hematopoietic cells,from hESCs and hiPSCs. Materials and Methods: Test cells were exposed to MEDII prior to being placed in conditions that promote embryoid body (EB) formation. Hematopoietic activity was measured by clonogenic assays,flow cytometry,quantitative real-time polymerase chain reaction of specific transcript complementary DNAs and the ability of cells to repopulate sublethally irradiated nonobese diabetic/severe combined immunodeficient interleukin-2 receptor ??-chain-null mice for almost 1 year. Results: Exposure of both hESCs and hiPSCs to MEDII induced a rapid and preferential differentiation of hESCs into mesodermal elements. Subsequently produced EBs showed a further enhanced expression of transcripts characteristic of multiple mesodermal lineages,and a concurrent decrease in endodermal and ectodermal cell transcripts. Frequency of all types of clonogenic hematopoietic progenitors in subsequently derived EBs was also increased. In vivo assays of MEDII-treated hESC-derived EBs also showed they contained cells able to undertake low-level but longterm multilineage repopulation of primary and secondary nonobese diabetic/severe combined immunodeficient interleukin-2 receptor ??-chain-null mice. Conclusions: MEDII treatment of hESCs and hiPSCs alike selectively enhances their differentiation into mesodermal cells and allows subsequent generation of detectable levels of hematopoietic progenitors with in vitro and in vivo differentiating activity. ?? 2009 ISEH - Society for Hematology and Stem Cells. View Publication

Long-term in vitro culture of undifferentiated human embryonic stem cells (hESCs) traditionally requires a fibroblast feeder cell layer. Using feeder cells in hESC cultures is highly laborious and limits large-scale hESC production for potential application in regenerative medicine. Replacing feeder cells with defined human extracellular matrix (ECM) components or synthetic biomaterials would be ideal for large-scale production of clinical-grade hESCs. We tested and compared different feeder cell-free hESC culture methods based on different human ECM proteins,human and animal sera matrices,and a Matrigel matrix. Also selected biomaterials were tested for feeder cell-free propagation of undifferentiated hESCs. The matrices were tested together with conventional and modified hESC culture media,human foreskin fibroblast-conditioned culture medium,chemically defined medium,TeSR1,and modified TeSR1 media. The results showed the undefined,xenogeneic Matrigel to be a superior matrix for hESC culture compared with the purified human ECM proteins,serum matrices,and the biomaterials tested. A long-term,feeder cell-free culture system was successful on Matrigel in combination with mTeSR1 culture medium,but a xeno-free,fully defined,and reproducible feeder cell-free hESC culture method still remains to be developed. View Publication

Recently it has been demonstrated that CD30 expression was rather specific for transformed than for normal human ES cells and therefore CD30 maybe suggested as a potential marker for human ES cells bearing chromosomal abnormalities. Using immunohistochemistry and RT-PCR analysis we examined �?¡D30 expression in 10 hESCs lines with normal and abberant karyotypes. All hESC lines expressed CD30 antigen and RNA in undifferentiated state whether cell line beared chromosomal abnormalities or not. In contrast to previous notions our data demonstrate that CD30 could be considered as marker of undifferentiated hESCs without respect to karyotype changes. View Publication

Human embryonic stem (ES) cells can be maintained in an undifferentiated state if the culture medium is first conditioned on a layer of mouse embryonic fibroblast (MEF) feeder cells. Here we show that human ES cell proliferation is coordinated by MEF-secreted heparan sulfate proteoglycans (HSPG) in conditioned medium (CM). These HSPG and other heparinoids can stabilize basic fibroblast growth factor (FGF2) in unconditioned medium at levels comparable to those observed in CM. They also directly mediate binding of FGF2 to the human ES cell surface,and their removal from CM impairs proliferation. Finally,we have developed a purification scheme for MEF-secreted HSPG in CM. Using column chromatography,immunoblotting,and mass spectrometry-based proteomic analysis,we have identified multiple HSPG species in CM. The results demonstrate that HSPG are key signaling cofactors in CM-based human ES cell culture. View Publication

Sickle cell disease (SCD) is the most common human genetic disease which is caused by a single mutation of human β-globin (HBB) gene. The lack of long-term treatment makes the development of reliable cell and gene therapies highly desirable. Disease-specific patient-derived human induced pluripotent stem cells (hiPSCs) have great potential for developing novel cell and gene therapies. With the disease-causing mutations corrected in situ,patient-derived hiPSCs can restore normal cell functions and serve as a renewable autologous cell source for the treatment of genetic disorders. Here we successfully utilized transcription activator-like effector nucleases (TALENs),a recently emerged novel genome editing tool,to correct the SCD mutation in patient-derived hiPSCs. The TALENs we have engineered are highly specific and generate minimal off-target effects. In combination with piggyBac transposon,TALEN-mediated gene targeting leaves no residual ectopic sequences at the site of correction and the corrected hiPSCs retain full pluripotency and a normal karyotype. Our study demonstrates an important first step of using TALENs for the treatment of genetic diseases such as SCD,which represents a significant advance toward hiPSC-based cell and gene therapies. View Publication

INTRODUCTION: Ischemic stroke is a leading cause of death and disability,but treatment options are severely limited. Cell therapy offers an attractive strategy for regenerating lost tissues and enhancing the endogenous healing process. In this study,we investigated the use of human embryonic stem cell-derived neural precursors as a cell therapy in a murine stroke model.backslashnbackslashnMETHODS: Neural precursors were derived from human embryonic stem cells by using a fully adherent SMAD inhibition protocol employing small molecules. The efficiency of neural induction and the ability of these cells to further differentiate into neurons were assessed by using immunocytochemistry. Whole-cell patch-clamp recording was used to demonstrate the electrophysiological activity of human embryonic stem cell-derived neurons. Neural precursors were transplanted into the core and penumbra regions of a focal ischemic stroke in the barrel cortex of mice. Animals received injections of bromodeoxyuridine to track regeneration. Neural differentiation of the transplanted cells and regenerative markers were measured by using immunohistochemistry. The adhesive removal test was used to determine functional improvement after stroke and intervention.backslashnbackslashnRESULTS: After 11 days of neural induction by using the small-molecule protocol,over 95% of human embryonic stem-derived cells expressed at least one neural marker. Further in vitro differentiation yielded cells that stained for mature neuronal markers and exhibited high-amplitude,repetitive action potentials in response to depolarization. Neuronal differentiation also occurred after transplantation into the ischemic cortex. A greater level of bromodeoxyuridine co-localization with neurons was observed in the penumbra region of animals receiving cell transplantation. Transplantation also improved sensory recovery in transplant animals over that in control animals.backslashnbackslashnCONCLUSIONS: Human embryonic stem cell-derived neural precursors derived by using a highly efficient small-molecule SMAD inhibition protocol can differentiate into electrophysiologically functional neurons in vitro. These cells also differentiate into neurons in vivo,enhance regenerative activities,and improve sensory recovery after ischemic stroke. View Publication

Development of non-invasive and accurate methods to track cell fate after delivery will greatly expedite transition of embryonic stem (ES) cell therapy to the clinic. In this protocol,we describe the in vivo monitoring of stem cell survival,proliferation and migration using reporter genes. We established stable ES cell lines constitutively expressing double fusion (DF; enhanced green fluorescent protein and firefly luciferase) or triple fusion (TF; monomeric red fluorescent protein,firefly luciferase and herpes simplex virus thymidine kinase (HSVtk)) reporter genes using lentiviral transduction. We used fluorescence-activated cell sorting to purify these populations in vitro,bioluminescence imaging and positron emission tomography (PET) imaging to track them in vivo and fluorescence immunostaining to confirm the results ex vivo. Unlike other methods of cell tracking,such as iron particle and radionuclide labeling,reporter genes are inherited genetically and can be used to monitor cell proliferation and survival for the lifetime of transplanted cells and their progeny. View Publication

Murine embryonic stem (mES) cells are self-renewing pluripotent cells that bear the capacity to differentiate into ectoderm-,endoderm-,and mesoderm-derived tissues. In suspension culture,embryonic stem (ES) cells grow into spherical embryoid bodies (EBs) and are useful for the study of specific gene products in the development and function of various tissue types. Osteoclasts are hematopoietic stem cell-derived cells that participate in bone turnover by secreting resorptive molecules such as hydrochloric acid and acidic proteases,which degrade the bone extracellular matrix. Aberrant osteoclast function leads to dysplastic,erosive,and sclerosing bone diseases. Previous studies have reported the derivation of osteoclasts from mES cells; however,most of these protocols require coculture with stromal cell lines. We describe two simplified,novel methods of stromal cell-independent ES cell-derived osteoclast development. View Publication