技术资料

Pluripotent or multipotent cell-based therapeutics are vital for skeletal reconstruction in non-healing critical-sized defects since the local endogenous progenitor cells are not often adequate to restore tissue continuity or function. However,currently available cell-based regenerative strategies are hindered by numerous obstacles including inadequate cell availability,painful and invasive cell-harvesting procedures,and tumorigenesis. Previously,we established a novel platform technology for inducing a quiescent stem cell-like stage using only a single extracellular proteoglycan,fibromodulin (FMOD),circumventing gene transduction. In this study,we further purified and significantly increased the reprogramming rate of the yield multipotent FMOD reprogrammed (FReP) cells. We also exposed the 'molecular blueprint' of FReP cell osteogenic differentiation by gene profiling. Radiographic analysis showed that implantation of FReP cells into a critical-sized SCID mouse calvarial defect,contributed to the robust osteogenic capability of FReP cells in a challenging clinically relevant traumatic scenario in vivo. The persistence,engraftment,and osteogenesis of transplanted FReP cells without tumorigenesis in vivo were confirmed by histological and immunohistochemical staining. Taken together,we have provided an extended potency,safety,and molecular profile of FReP cell-based bone regeneration. Therefore,FReP cells present a high potential for cellular and gene therapy products for bone regeneration. View Publication

Despite many years of intensive effort,there is surprisingly little consensus on the most suitable markers with which to locate and isolate stem cells from adult tissues. By comparison,the study of cancer stem cells is still in its infancy; so,unsurprisingly,there is great uncertainty as to the identity of these cells. Stem cell markers can be broadly categorized into molecular determinants of self-renewal,clonogenicity,multipotentiality,adherence to the niche,and longevity. This review assesses the utility of recognizing cancer stem cells by virtue of high expression of aldehyde dehydrogenases (ALDHs),probably significant determinants of cell survival through their ability to detoxify many potentially cytotoxic molecules,and contributing to drug resistance. Antibodies are available against the ALDH enzyme family,but the vast majority of studies have used cell sorting techniques to enrich for cells expressing these enzymes. Live cells expressing high ALDH activity are usually identified by the ALDEFLUOR kit and sorted by fluorescence activated cell sorting (FACS). For many human tumours,but notably breast cancer,cell selection based upon ALDH activity appears to be a useful marker for enriching for cells with tumour-initiating activity (presumed cancer stem cells) in immunodeficient mice,and indeed the frequency of so-called ALDH(bri) cells in many tumours can be an independent prognostic indicator. View Publication

The diverse progenitors that give rise to the human neocortex have been difficult to characterize because progenitors,particularly radial glia (RG),are rare and are defined by a combination of intracellular markers,position and morphology. To circumvent these problems,we developed Fixed and Recovered Intact Single-cell RNA (FRISCR),a method for profiling the transcriptomes of individual fixed,stained and sorted cells. Using FRISCR,we profiled primary human RG that constitute only 1% of the midgestation cortex and classified them as ventricular zone-enriched RG (vRG) that express ANXA1 and CRYAB,and outer subventricular zone-localized RG (oRG) that express HOPX. Our study identified vRG and oRG markers and molecular profiles,an essential step for understanding human neocortical progenitor development. FRISCR allows targeted single-cell profiling of any tissues that lack live-cell markers. View Publication

Interaction between endothelial cells and mural cells (pericytes and vascular smooth muscle) is essential for vascular development and maintenance. Endothelial cells arise from Flk1-expressing (Flk1+) mesoderm cells,whereas mural cells are believed to derive from mesoderm,neural crest or epicardial cells and migrate to form the vessel wall. Difficulty in preparing pure populations of these lineages has hampered dissection of the mechanisms underlying vascular formation. Here we show that Flk1+ cells derived from embryonic stem cells can differentiate into both endothelial and mural cells and can reproduce the vascular organization process. Vascular endothelial growth factor promotes endothelial cell differentiation,whereas mural cells are induced by platelet-derived growth factor-BB. Vascular cells derived from Flk1+ cells can organize into vessel-like structures consisting of endothelial tubes supported by mural cells in three-dimensional culture. Injection of Flk1+ cells into chick embryos showed that they can incorporate as endothelial and mural cells and contribute to the developing vasculature in vivo. Our findings indicate that Flk1+ cells can act as 'vascular progenitor cells' to form mature vessels and thus offer potential for tissue engineering of the vascular system. View Publication

Loss or mutation of the TP53 tumor suppressor gene is not commonly observed in acute myeloid leukemia (AML),suggesting that there is an alternate route for cell transformation. We investigated the hypothesis that previously observed Bcl-2 family member overexpression suppresses wild-type p53 activity in AML. We demonstrate that wild-type p53 protein is expressed in primary leukemic blasts from patients with de novo AML using 2-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and phospho-specific flow cytometry. We found that p53 was heterogeneously expressed and phosphorylated in AML patient samples and could accumulate following DNA damage. Overexpression of antiapoptosis protein Bcl-2 in AML cells was directly correlated with p53 expression and phosphorylation on serine residues 15,46,and 392. Within those patients with the highest levels of Bcl-2 expression,we identified a mutation in FLT3 that duplicated phosphorylation site Y591. The presence of this mutation correlated with greater than normal Bcl-2 expression and with previously observed profiles of potentiated STAT and MAPK signaling. These results support the hypothesis that Flt3-mediated signaling in AML enables accumulation of Bcl-2 and maintains a downstream block to p53 pathway apoptosis. Bcl-2 inhibition might therefore improve the efficacy of existing AML therapies by inactivating this suppression of wild-type p53 activity. View Publication

Freshly isolated human adult hepatocytes are considered to be the gold standard tool for in vitro studies. However,primary hepatocyte scarcity,cell cycle arrest and the rapid loss of cell phenotype limit their widespread deployment. Human embryonic stem cells and induced pluripotent stem cells provide renewable sources of hepatocyte-like cells (HLCs). Despite the use of various differentiation methodologies,HLCs like primary human hepatocytes exhibit unstable phenotype in culture. It has been shown that the functional capacity can be improved by adding back elements of human physiology,such as cell co-culture or through the use of natural and/or synthetic surfaces. In this study,the effect of fluid shear stress on HLC performance was investigated. We studied two important liver functions,cytochrome P450 drug metabolism and serum protein secretion,in static cultures and those exposed to fluid shear stress. Our study demonstrates that fluid shear stress improved Cyp1A2 activity by approximately fivefold. This was paralleled by an approximate ninefold increase in sensitivity to a drug,primarily metabolised by Cyp2D6. In addition to metabolic capacity,fluid shear stress also improved hepatocyte phenotype with an approximate fourfold reduction in the secretion of a foetal marker,alpha-fetoprotein. We believe these studies highlight the importance of introducing physiologic cues in cell-based models to improve somatic cell phenotype. View Publication

Direct cell-cell contact between haematopoietic progenitor cells (HPCs) and their cellular microenvironment is essential to maintain 'stemness'. In cancer biology,focal adhesion (FA) proteins are involved in survival signal transduction in a wide variety of human tumours. To define the role of FA proteins in the haematopoietic microenvironment of myelodysplastic syndromes (MDS),CD73-positive mesenchymal stromal cells (MSCs) were immunostained for paxillin,pFAK [Y(397)],and HSP90α/β and p130CAS,and analysed for reactivity,intensity and cellular localisation. Immunofluorescence microscopy allowed us to identify qualitative and quantitative differences,and subcellular localisation analysis revealed that in pathological MSCs,paxillin,pFAK [Y(397)],and HSP90α/β formed nuclear molecular complexes. Increased expression of paxillin,pFAK [Y(397)],and HSP90α/β and enhanced nuclear co-localisation of these proteins correlated with a consistent proliferative advantage in MSCs from patients with refractory anaemia with excess blasts (RAEB) and negatively impacted clonogenicity of HPCs. These results suggest that signalling via FA proteins could be implicated in HPC-MSC interactions. Further,because FAK is an HSP90α/β client protein,these results suggest the utility of HSP90α/β inhibition as a target for adjuvant therapy for myelodysplasia. View Publication

Cell type-specific surface markers offer a powerful tool for purifying defined cell types for restorative therapies and drug screenings. Midbrain dopaminergic neurons (mesDA) are the nerve cells preferentially lost in the brains of Parkinson's disease patients. Clinical trials of transplantation of fetal neural precursors suggest that cell therapy may offer a cure for this devastating neurological disease. Many lines of preclinical studies demonstrate that neural progenitors committed to dopaminergic fate survive and integrate better than postmitotic DA neurons. We show that the folate-receptor 1 (FolR1),a GPI-anchored cell surface molecule,specifically marks mesDA neural progenitors and immature mesDA neurons. FolR1 expression superimposes with Lmx1a,a bona-fide mesDA lineage marker,during the active phase of mesDA neurogenesis from E9.5 to E14.5 during mouse development,as well as in ESC-derived mesDA lineage. FolR1(+) neural progenitors can be isolated by FACS or magnetic sorting (MAC) which give rise to dopamine neurons expressing TH and Pitx3,whilst FolR1 negative cells generate non-dopaminergic neurons and glia cells. This study identifies FolR1 as a new cell surface marker selectively expressed in mesDA progenitors in vivo and in vitro and that can be used to enrich in vitro differentiated TH neurons. View Publication

The generation of human induced pluripotent stem cells (hiPSC) from somatic cells has enabled the possibility to provide patient-specific hiPSC for cell-based therapy,drug discovery,and other translational applications. Two major obstacles in using hiPSC for clinical application reside in the risk of genomic modification when they are derived with viral transgenes and risk of teratoma formation if undifferentiated cells are engrafted. In this study,we report the generation of footprint-free" hiPSC-derived astrocytes. These are efficiently generated� View Publication

Many human embryonic stem (hES) and induced pluripotent stem (hiPS) cell differentiation protocols begin with the formation of three-dimensional aggregates of cells called embryoid bodies (EBs). Traditional EB formation methods result in a heterogeneous population of EB sizes and shapes,which then undergo heterogeneous differentiation efficiencies. AggreWell(TM)400 and AggreWell(TM)800 use the spin-EB method to force the aggregation of a defined number of cells,thereby controlling EB size and generating a population of uniform EBs. Moreover,the dense array of microwells on the bottom surface of AggreWell(TM)400 provide for the rapid and simple production of thousands of EBs at a time. View Publication

A simple,scalable,and reproducible technology that allows direct formation of large numbers of homogeneous and synchronized embryoid bodies (EBs) of defined sizes from dissociated human induced pluripotent stem cells (hiPSCs) was developed. Non-cell-adhesive hydrogels were used to create round-bottom microwells to host dissociated hiPSCs. No Rho-associated kinase inhibitor (ROCK-i),or centrifugation was needed and the side effects of ROCK-i can be avoided. The key requirement for the successful EB formation in addition to the non-cell-adhesive round-bottom microwells is the input cell density per microwell. Too few or too many cells loaded into the microwells will compromise the EB formation process. In parallel,we have tested our microwell-based system for homogeneous hEB formation from dissociated human embryonic stem cells (hESCs). Successful production of homogeneous hEBs from dissociated hESCs in the absence of ROCK-i and centrifugation was achieved within an optimal range of input cell density per microwell. Both the hiPSC- and hESC-derived hEBs expressed key proteins characteristic of all the three developmental germ layers,confirming their EB identity. This novel EB production technology may represent a versatile platform for the production of homogeneous EBs from dissociated human pluripotent stem cells (hPSCs). View Publication

The mechanisms regulating key fate decisions such as self-renewal and differentiation in hematopoietic stem and progenitor cells (HSPC) remain poorly understood. We report here a screening strategy developed to assess modulators of human hematopoiesis using a lentiviral short hairpin RNA (shRNA) library transduced into cord blood-derived stem/progenitor cells. To screen for modifiers of self-renewal/differentiation,we used the limited persistence of HSPCs under ex vivo culture conditions as a baseline for functional selection of shRNAs conferring enhanced maintenance or expansion of the stem/progenitor potential. This approach enables complex,pooled screens in large numbers of cells. Functional selection identified novel specific gene targets (exostoses 1) or shRNA constructs capable of altering human hematopoietic progenitor differentiation or stem cell expansion,respectively,thereby demonstrating the potential of this forward screening approach in primary human stem cell populations. View Publication