Lineage Differentiation Potential Research Articles

A matter of identity — Phenotype and differentiation potential of human somatic stem cells

Human somatic stem cells with neural differentiation potential can be valuable for developing cell-based therapies, including treatment of birth-related defects, while avoiding issues associated with cell reprogramming. Precisely defining the “identity” and differentiation potential of somatic stem cells from different sources, has proven difficult, given differences in sets of specific markers, protocols used and lack of side-by-side characterization of these cells in different studies. Therefore, we set to compare expression of mesenchymal and neural markers in human umbilical cord-derived mesenchymal stem cells (UC-MSCs), pediatric adipose-derived stem cells (p-ADSCs) in parallel with human neural stem cells (NSCs). We show that UC-MSCs at a basal level express mesenchymal and so-called “neural” markers, similar to that we previously reported for the p-ADSCs. All somatic stem cell populations studied, independently from tissue and patient of origin, displayed a remarkably similar expression of surface markers, with the main difference being the restricted expression of CD133 and CD34 to NSCs. Expression of certain surface and neural markers was affected by the expansion medium used. As predicted, UC-MSCs and p-ADSCs demonstrated tri-mesenchymal lineage differentiation potential, though p-ADSCs display superior chondrogenic differentiation capability. UC-MSCs and p-ADSCs responded also to neurogenic induction by up-regulating neuronal markers, but crucially they appeared morphologically immature when compared with differentiated NSCs. This highlights the need for further investigation into the use of these cells for neural therapies. Crucially, this study demonstrates the lack of simple means to distinguish between different cell types and the effect of culture conditions on their phenotype, and indicates that a more extensive set of markers should be used for somatic stem cell characterization, especially when developing therapeutic approaches.

Loss of non-coding RNA expression from the DLK1-DIO3 imprinted locus correlates with reduced neural differentiation potential in human embryonic stem cell lines.

IntroductionPluripotent stem cells are increasingly used to build therapeutic models, including the transplantation of neural progenitors derived from human embryonic stem cells (hESCs). Recently, long non-coding RNAs (lncRNAs), including delta-like homolog 1 gene and the type III iodothyronine deiodinase gene (DLK1-DIO3) imprinted locus-derived maternally expressed gene 3 (MEG3), were found to be expressed during neural development. The deregulation of these lncRNAs is associated with various neurological diseases. The imprinted locus DLK1-DIO3 encodes abundant non-coding RNAs (ncRNAs) that are regulated by differential methylation of the locus. We aim to study the correlation between the DLK1-DIO3-derived ncRNAs and the capacity of hESCs to differentiate into neural lineages.MethodsWe classified hESC sublines into MEG3-ON and MEG3-OFF based on the expression levels of MEG3 and its downstream microRNAs as detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). A cDNA microarray was used to analyze the gene expression profiles of hESCs. To investigate the capacity of neural differentiation in MEG3-ON and MEG3-OFF hESCs, we performed neural lineage differentiation followed by neural lineage marker expression and neurite formation analyses via qRT-PCR and immunocytochemistry, respectively. MEG3-knockdown via small interfering RNA (siRNA) and small hairpin RNA (shRNA) was used to investigate the potential causative effect of MEG3 in regulating neural lineage-related gene expression.ResultsDLK1-DIO3-derived ncRNAs were repressed in MEG3-OFF hESCs compared with those in the MEG3-ON hESCs. The transcriptome profile indicated that many genes related to nervous system development and neural-type tumors were differentially expressed in MEG3-OFF hESCs. Three independent MEG3-knockdown assays using different siRNA and shRNA constructs consistently resulted in downregulation of some neural lineage genes. Lower expression levels of stage-specific neural lineage markers and reduced neurite formation were observed in neural lineage-like cells derived from MEG3-OFF-associated hESCs compared with those in the MEG3-ON groups at the same time points after differentiation.ConclusionsRepression of ncRNAs derived from the DLK1-DIO3 imprinted locus is associated with reduced neural lineage differentiation potential in hESCs.Electronic supplementary materialThe online version of this article (doi:10.1186/scrt535) contains supplementary material, which is available to authorized users.

Aldehyde dehydrogenase and estrogen receptor define a hierarchy of cellular differentiation in the normal human mammary epithelium.

IntroductionAlthough estrogen and progesterone play a key role in normal mammary development and in breast cancer, the potential for proliferation and lineage differentiation as well as origin of cells that express the estrogen receptor (ER) in normal breast epithelium are not known. Some evidence suggests that normal human mammary stem/progenitor cells are ER–, but the identity of these cells and the cellular hierarchy of breast epithelium are still subjects of controversy. It is likely that elucidation of these aspects will bring insight into the cellular origin of breast cancer subtypes.MethodsWe used fluorescence-activated cell sorting of primary human mammary epithelial cells along with in vitro and in vivo functional assays to examine the hierarchic relation between cells with aldehyde dehydrogenase enzymatic activity (ALDH+ cells) and ER+ cells in the normal human breast epithelium. We assessed the proliferation and lineage differentiation potential of these cells in vitro and in vivo. A gene reporter assay was used to separate live ER+ and ER– mammary epithelial cells. With shRNA-mediated knockdown, we investigated the role of ALDH isoforms in the functionality of mammary epithelial progenitor cells.ResultsWe describe a cellular hierarchy in the normal human mammary gland in which ER–/ALDH+ cells with functional properties of stem/progenitor cells generate ER+ progenitor cells, which in turn give rise to cells of luminal lineage. We show that the ALDH1A1 isoform, through its function in the retinoic acid metabolism, affects the proliferation and/or early differentiation of stem/progenitor cells and is important for branching morphogenesis.ConclusionsThis study presents direct evidence that ER+ cells are generated by ER–/ALDH+ stem/progenitor cells. We also show that ER+ cells are able to generate cell progeny of luminal lineage in vitro and in vivo. Loss of ALDH1A1 function impairs this process, as well as branching morphogenesis and clonogenicity in suspension culture. This latter effect is reversed by treatment with retinoic acid.

A committed hemopoietic precursor to innate lymphoid cells (HEM3P.277)

Abstract Innate lymphoid cells specialize in the rapid secretion of polarized sets of cytokines and chemokines to combat infection and promote tissue repair at mucosal barriers. Their growing diversity and close similarities with previously characterized NK and LTi cells have prompted a provisional classification of all innate lymphocytes into groups 1, 2 and 3 based solely on cytokine properties. Elucidating their development pathways is essential to resolve their lineage relationships and dissect their respective functions in disease and homeostasis. Using lineage tracing and transfer studies, we identified and characterized a novel subset of lymphoid precursors in fetal liver and adult bone marrow that transiently expressed high amounts of PLZF, a transcription factor previously associated with NKT cell development. PLZF-high precursors were committed ILC progenitors with multiple ILC1, ILC2 and ILC3 lineage differentiation potential at the clonal level. They excluded classical LTi and NK cells, but included a peculiar subset of NK1.1+ DX5- ‘NK-like’ cells residing in the liver. Deletion of PLZF markedly altered the frequency and function of several ILC subsets, but did not affect LTi or NK cells. These findings establish novel lineage relationships between ILC, NK and LTi cells and identify the elusive precursor to ILC, termed ILCP. They also reveal the broad, defining role of PLZF in the differentiation of innate lymphocytes.

Hematopoietic Stem and Progenitor Cell Fate Decisions Are Regulated By a Cell-Autonomous p190-B/TGF-β Signaling Pathway

Hematopoietic stem cells (HSC) are undifferentiated cells that self-renew and produce all mature blood and immune cells in order to sustain life-long hematopoiesis. The molecular mechanisms that determine HSC fate decisions still remain poorly understood. Identifying these factors is of great biological and clinical importance, as alteration in HSC fate decisions will eventually lead to HSC depletion or malignant HSC expansion. We previously showed that p190-B GTPase Activating Protein (GAP), a negative regulator of Rho activity, is a critical regulator of HSC self-renewal. P190-B loss enhanced long-term engraftment during serial transplantation; but, surprisingly, without altering their survival, blood lineage differentiation and the balance between quiescence and proliferation (Xu et al, Blood). Therefore, we hypothesize that p190-B regulates HSC self-renewal by controlling a HSC fate decision to self-renew or to differentiate, so-called asymmetric versus symmetric self-renewal divisions. To test this, we compared patterns of single WT and p190-B-/- HSC (i.e. Lin-c-kit+Sca-1+CD150+CD48- [LSK-SLAM]) divisions over serial transplantation. First, we confirmed that the division rate of single LSK-SLAM was similar between the genotypes. Then, we performed the pair daughter cell assay to examine the ability of LSK-SLAM to generate daughter cells that retain multipotent lineage differentiation potential. We found that non-transplanted (CTL) HSC gave rise to 93% symmetric self-renewal divisions (i.e. both daughter cells are multipotent, neutrophil, erythroid, macrophage and megakaryocyte (nemM)), and 7% were asymmetric (only one daughter cell is multipotent). Interestingly, after 2 rounds of transplantation (2T), WT HSCs produced only 50% symmetric self-renewal divisions whereas p190-B-deficient HSCs maintained 92% symmetric self-renewal divisions. Hence, p190-B modulates asymmetric/symmetric self-renewal divisions to control HSC regeneration over serial transplantation. Using transcriptional profiling and chemical screening, we identified, quite unexpectedly, the transforming growth factor beta (TGFβ) pathway as a regulatory pathway mediating p190-B functions. Expression of TGFβ responsive genes (mRNA expression of tgif2, smurf2) were higher in 2T-WT than in 2T-p190-B–/–-HSCs and CTL HSC. To assess if increased TGFβ signaling affected HSC self-renewing decisions, we used the TGF-β inhibitor, SB431542, ex vivo. TGFβ inhibitor treatment of 2T-WT LSK-SLAM in pair daughter cell assay converted their fate decision to produce 90% symmetric self-renewal divisions; TGFβ inhibitor treatment ex vivo for 48h of WT LT-HSCs isolated from primary transplanted mice enhanced engraftment into secondary mice. Importantly, TGFβ inhibitor-treatment of mice over serial transplantation reversed transplant-related WT HSC decline as it enhanced HSC pool regeneration in BM and long-term HSC engraftment. Interestingly, it did not alter HSC cell cycle parameters or the relative heterogeneity of the HSC pool or blood lineage maturation. Mechanistically, p190-B appeared to regulate TGF-β signaling in a cell-autonomous manner by controlling bioactive TGF-β protein within HSCs. Finally we observed that TGFβ mediated its effect via non-canonical p38MAPK signaling. This study identifies a previously unknown p190-B/TGFβ signaling network that governs HSC fate decisions to self-renew or to differentiate, without altering HSC quiescence or development of the progeny. This also reveals an unexpected role for TGFβ as a regulator of HSC fate beyond its well-defined role in HSC hibernation. The clinical implications are important for the field of HSC expansion and bone marrow transplantation. Disclosures: No relevant conflicts of interest to declare.

First Description Of a t(10;11)(q22;q23)/MLL-TET1 Reciprocal Translocation In a T Lymphoblastic Lymphoma With Subsequent Lineage Switch To Acute Myelomonocytic Myeloid Leukemia

TET1 genomic breakpoints and clinical features of MLL-TET1 rearrangements have been described in 13 acute leukemia cases, 11 in AML, 2 in B cell-precursor ALL. The incidence of this rare translocation was evaluated to 0.3% of MLL rearranged AML cases (5 out of 1590 MLL [Meyer C. Leukemia 2013]). Although those cases are very uncommon, their study can improve our current understanding of leukemogenesis. We report here the first t(10;11) MLL-TET1 positive case of lymphoblastic T lymphoma occurring in a 31 years old male patient, with a subsequent transformation to AML.The patient was referred for a large mediastinal mass and right pleural effusion. Mediastinal and bronchus biopsies led to the diagnosis of a precursor-T cell lymphoblastic lymphoma, expressing CD3, CD5, CD4, CD8, CD10 antigens, without any expression of CD34 or CD79.Molecular analyses of the malignant T-cells showed a clonal TCR gamma-chain gene rearrangement together with HOXA10 overexpression. FISH analysis showed a MLL breakage. The partner gene, TET1, was identified using RP11-9E13 and RP11-314J18 BACs, corresponding to the recurrent translocation t(10;11)(q22;q23). MLL-TET1 fusion transcript was detected (intron 8 of TET1 fused to exon 8 of MLL), as well as its reciprocal transcript.The patient was treated following the (GELA) LL03 protocol, and was considered in complete remission after induction and consolidation phases. Fourteen months after the diagnosis, a bone marrow examination was performed for thrombopenia (6 G/L) which revealed a myelomonocytic acute leukemia with trilineage dysplasia.At this time, The MLL-TET1 fusion transcript as well as HOXA10 overexpression was still present but the TCR rearrangement was not detected. A non-familial donor allogeneic bone marrow transplant was performed in CR after intensive chemotherapy, that was complicated by a grade IV acute graft-versus-host disease. The patient died 54 days after the transplant of bacterial sepsis leading to multi-organ failure.MLL-TET1 fusions have been described in 13 cases in the literature, mainly in AMLs (11/13 cases, mostly AML M4 or M5 cases) and in B-ALLs (2/13 cases). The case reported here presents two interesting features. Firstly, this patient harbors the first MLL-TET1 fusion reported to date in T-ALL, and secondly this case presented a lymphoid to myeloid phenotype switch during the time course of the disease.This strongly suggests that the translocation occurred very early during hematopoietic differentiation, prior to the lymphoid/myeloid commitment. As described for the Ph1 chromosome rearrangement, the t(10;11) translocation may arise in hematopoietic stem cell rather than in committed progenitors. These features are also described in 8p11 stem cell syndrome that involves FGFR1. In both cases, genetic rearrangements arise in myeloid or lymphoid neoplasms with possible subsequent transformation.TET family enzymes convert 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and play a key role in active DNA demethylation. TET1 and TET2 are also the key enzymes responsible for the presence of 5hmC in mouse embryonic stem cells (ESCs) (Koh KP., Cell Stem Cell 2011), and TET1 functions to regulate the lineage differentiation potential of ESCs. In addition to its role in DNA demethylation, TET1 interacts physically with NANOG and NANOG/TET1 co-occupy genomic loci of genes associated with both maintenance of pluripotency and lineage commitment in embryonic stem cells (Costa Y., Nature 2013). Taken together, these observations enlighten possible mechanism of the lineage switch observed in this case, and may be a rationale for using demethylating agents in MLL-TET1 neoplasms. Disclosures:No relevant conflicts of interest to declare.

CD133 Is a Positive Marker Of Human Cord Blood-Derived CD34-Negative Hematopoietic Stem Cells

BackgroundWe have previously identified very primitive human cord blood (CB)-derived CD34-negative (CD34-) severe combined immunodeficiency (SCID)- repopulating cells (SRCs) using the intra-bone marrow injection (IBMI) method (Blood 2003:101;2924). A series of our studies suggests that the identified CD34- SRCs are a distinct class of primitive hematopoietic stem cell (HSC) and that they are at the apex of human HSC hierarchy. Recently, we developed a high-resolution purification method for primitive CD34- SRCs using 18 lineage (Lin)-specific antibodies, which can enrich CD34- SRC at 1/1,000 level (Exp Hematol 2011: 39:203). In the present study, we tried to identify the positive marker of CD34- SRCs in order to further purify and characterize the CD34- SRCs (HSCs). Materials and MethodsFirst, we extensively analyzed candidate positive markers, including known HSC markers and various adhesion molecules by FACS using highly purified CB-derived 18Lin-CD34+/- cells. Finally, we identified CD133 as a positive marker of human CB-derived CD34- SRCs. Then, CB-derived 18Lin- CD34+/-CD133+/- cells were sorted by FACS, and hematopoietic stem/progenitor cell (HSPC) capacities of these four fractions of cells were extensively investigated. HSPC capacities were evaluated using (1) colony-forming cell (CFC) assays, (2) measurement of maintenance/production of CD34+ cell capacities in co-cultures with human bone marrow-derived mesenchymal stromal cells (BM-MSCs) (Blood 2010:24:162), (3) SRC activities using NOG mice, (4) limiting dilution analyses (LDA) to determine the SRC frequency in the 18Lin-CD34-CD133+ fractions, and (5) comparison of gene expression profiles between 18Lin-CD34+/-CD133+/- cells by real-time RT-PCR. ResultsSeventy-five percent of 18Lin-CD34+ and 13.5% of 18Lin-CD34- cells highly expressed CD133. In the CFC assays, the plating efficiencies of 18Lin-CD34+CD133+, CD34+CD133-, CD34-CD133+ and CD34-CD133- cells were 57%, 65%, 39% and 19%, respectively. Interestingly, most of 18Lin-CD34-CD133+/- cells formed erythroid-bursts (71% and 73%) and erythro/megakaryocytes-containing mixed colonies (25% and 27%). On the contrary, they formed few granulocyte/macrophage colonies (4.2% and 0%). Then, we co-cultured these four fractions of cells with human BM-MSCs. One thousand of 18Lin-CD34+/-CD133+/- cells were seeded into each well and cells were co-cultured for 7 days in the presence of SCF+TPO+FL+IL-3+IL-6 +G-CSF. Both the 18Lin-CD34-CD133+/- cells produced CD34+ cells. However, the percentage and absolute number of CD34+ cells produced from 18Lin-CD34-CD133+ cells (31.7 % and 3.2 x 104 cells) were greater than those of 18Lin-CD34-CD133- cells (13.2 % and 0.4 x 104 cells). In addition, both the 18Lin-CD34- CD133+/- cells generated higher percentages (13.5 % and 11.5%) of CD41+ cells compared to those of the 18Lin- CD34+CD133+/- (1.8% and 4.2%) cells. Collectively, 18Lin-CD34+/-CD133+/- cells showed different in vitro lineage differentiation potentials. Then, these four fractions of cells were transplanted into NOG mice by IBMI. We performed primary and secondary transplantations for up to 36 weeks. In the results, all of the mice received 18Lin-CD34+CD133+ cells (n = 5) or 18Lin-CD34-CD133+ cells (n = 9) showed primary and secondary human CD45+ cell repopulations. However, neither 18Lin-CD34+CD133- cells nor 18Lin-CD34-CD133- cells showed human cell repopulations (n = 6 in each group). These results clearly demonstrated that the CD133 expression clearly segregated SRC activities in the 18Lin-CD34+/- cells. Moreover, LDA demonstrated that the frequency of SRCs in the 18Lin-CD34-CD133+ fraction was 1/142. Interestingly, HSC self-renewal maintenance genes, such as Notch1, HoxB4, HoxA9, and Bmi-1, were highly expressed in both 18Lin-CD34+/-CD133+ cells. ConclusionThese results clearly demonstrated that CD133 is a positive marker of human CB-derived CD34- SRCs (HSCs). Furthermore, CD133 segregated SRC activities of 18Lin-CD34- as well as 18Lin-CD34+ cells in its positive fractions. More importantly, these findings suggest that number of CD133+ cells in cord blood units is a more appropriate marker to detect/predict HSC potentials in cord blood stem cell transplantation in comparison to currently used CD34+ cell numbers. Disclosures:No relevant conflicts of interest to declare.

The relationship between the polymorphism of immunity genes and both aging and age-related diseases

Aging is acommon, progressive and irreversible state of multi-cell dysfunction. Immune aging mainly includes the declines of regenerative capacity and lymphoid lineage differentiation potential, the hyporesponsive to infection and vaccination, the hyperresponsive in the context of inflammatory pathology, and the increased risk of autoimmunity. The dysfunction of aged immune system accelerates the occurrence of aging and age-related diseases. The mutation of immunity genes that affect immune responses accelerates or slows aging process and age-related diseases. The frequencies of acquired immunity genes, such as immune protective HLA II DRB1*11 and DRB*16-associated haplotype, are increased in the longevity populations. The increased susceptibility of immune inflammatory response, morbidity and mortality in the elderly is often associated with decreased frequencies of anti-inflammatory factor IL-10 -1082G allele, TNF-β1 haplotype cnd10T/C, cnd25G/G, -988C/C, -800G/A, low proinflammatory fator TNFa level related extended TNF-A genotype -1031C/C, -863C/A, -857C/C, IL-6-174 CC and IFN-γ+874 T allele as well. The innate immunity genes, such as highly expressed anti-inflammatory +896 G KIR4 allele, CCR5Δ32 variant, -765 C Cox-2 allele, -1708 G and 21 C 5-Lox alleles are detected in centenarians. In age-related diseases, a higher CMV-specific IgG antibody level in elderly individuals is associated with a decreased frequency of KIR haplotypes KIR2DS5 and A1B10 and an increased frequency of MBL2 haplotypes LYPB, LYQC and HYPD that result in the absence of MBL2 protein. The increased frequencies of CRP ATG haplotypes and CFH 402 His allele indicate high mortality in the elderly. In the present study, we review the advances in the polymorphism and haplotype of innate and adoptive immunity genes, and their association with both aging and age-related diseases. To strengthen the analysis of extended haplotypes, epigenetic studies of immunity genes and genetic study of hematopoietic stem cell senescence will be helpful to understand the accurate basis of aging-related immune genetics better.

FoxO3a Contributes to the Reprogramming Process and the Differentiation of Induced Pluripotent Stem Cells

Induced pluripotent stem (iPS) cells, which are morphologically and functionally similar with embryonic stem (ES) cells, have been successfully generated from somatic cells through defined reprogramming transcription factors. Forkhead class O3a (FoxO3a) has been recently reported to play an important role in the homeostasis and maintenance of certain types of stem cells; however, the role of FoxO3a in the reprogramming process and differentiation of iPS cells remains unclear. In this study, we investigate the function of FoxO3a during the reprogramming process and characterize the properties of iPS cells from FoxO3a-wild type and -null mouse embryonic fibroblasts (MEFs). Our results show that the FoxO3a-null iPS cells are similar to the wild-type iPS cells in the levels of ES cell markers, alkaline phosphatase activity, and formation of teratoma in vivo. The reprogramming process is delayed in the FoxO3a-null MEFs compared to the wild-type MEFs; whereas the overexpression of FoxO3a partially recovers the impaired reprogramming efficiency in the null group. More importantly, FoxO3a deficiency impairs the neuronal lineage differentiation potential of iPS cells in vitro. These results suggest that FoxO3a affects the reprogramming kinetics and the neuronal lineage differentiation potential of the resulting iPS cells. Therefore, this study demonstrates a novel function of FoxO3a in cell reprogramming, which will help the development of alternative strategies for generating iPS cells.

Ontogeny of Human Umbilical Cord Perivascular Cells: Molecular and Fate Potential Changes During Gestation

Human umbilical cord-derived perivascular cells (PVCs) are a recently characterized source of mesenchymal stromal cells that has gained much interest in the field of cellular therapeutics. However, very little is known about the changes in fate potential and restrictions that these cells undergo during gestational development. This study is the first to examine the phenotypic, molecular, and functional properties of first trimester (FTM)-derived PVCs, outlining properties that are unique to this population when compared to term (TERM) counterparts. FTM- and TERM-PVCs displayed analogous mesenchymal, perivascular, and immunological immunophenotypes. Both PVCs could be maintained in culture without alteration to these phenotypes or mesenchymal lineage differentiation potential. Some unique features of FTM-PVCs were uncovered in this study: (1) while the gene signatures of FTM- and TERM-PVCs were similar, key differences were observed, namely, that the Oct4A and Sox17 proteins were detected in FTM-PVCs, but not in TERM counterparts; (2) FTM-PVCs exhibited a greater proliferative potential; and (3) FTM-PVCs were more efficient in their in vitro differentiation toward selective mesenchymal cell types, including the chondrogenic and adipogenic lineages, as well as toward neuronal- and hepatocyte-like lineages, when compared to TERM-PVCs. Both PVCs were able to generate osteocytes and cardiomyocyte-like cells with similar efficiencies in vitro. Overall, FTM-PVCs show more plasticity than TERM-PVCs with regard to fate acquisition, suggesting that a restriction in multipotentiality is imposed on PVCs as gestation progresses. Taken together, our findings support the idea that PVCs from earlier in gestation may be better than later sources of multipotent stromal cells (MSCs) for some regenerative medicine applications.

Wnt Signaling Regulates the Lineage Differentiation Potential of Mouse Embryonic Stem Cells through Tcf3 Down-Regulation

Canonical Wnt signaling plays a rate-limiting role in regulating self-renewal and differentiation in mouse embryonic stem cells (ESCs). We have previously shown that mutation in the Apc (adenomatous polyposis coli) tumor suppressor gene constitutively activates Wnt signaling in ESCs and inhibits their capacity to differentiate towards ecto-, meso-, and endodermal lineages. However, the underlying molecular and cellular mechanisms through which Wnt regulates lineage differentiation in mouse ESCs remain to date largely unknown. To this aim, we have derived and studied the gene expression profiles of several Apc-mutant ESC lines encoding for different levels of Wnt signaling activation. We found that down-regulation of Tcf3, a member of the Tcf/Lef family and a key player in the control of self-renewal and pluripotency, represents a specific and primary response to Wnt activation in ESCs. Accordingly, rescuing Tcf3 expression partially restored the neural defects observed in Apc-mutant ESCs, suggesting that Tcf3 down-regulation is a necessary step towards Wnt-mediated suppression of neural differentiation. We found that Tcf3 down-regulation in the context of constitutively active Wnt signaling does not result from promoter DNA methylation but is likely to be caused by a plethora of mechanisms at both the RNA and protein level as shown by the observed decrease in activating histone marks (H3K4me3 and H3-acetylation) and the upregulation of miR-211, a novel Wnt-regulated microRNA that targets Tcf3 and attenuates early neural differentiation in mouse ESCs. Our data show for the first time that Wnt signaling down-regulates Tcf3 expression, possibly at both the transcriptional and post-transcriptional levels, and thus highlight a novel mechanism through which Wnt signaling inhibits neuro-ectodermal lineage differentiation in mouse embryonic stem cells.

Isolation, characterization, and mesodermic differentiation of stem cells from adipose tissue of camel (Camelus dromedarius)

Adipose-derived stem cells are an attractive alternative as a source of stem cells that can easily be extracted from adipose tissue. Isolation, characterization, and multi-lineage differentiation of adipose-derived stem cells have been described for human and a number of other species. Here we aimed to isolate and characterize camel adipose-derived stromal cell frequency and growth characteristics and assess their adipogenic, osteogenic, and chondrogenic differentiation potential. Samples were obtained from five adult dromedary camels. Fat from abdominal deposits were obtained from each camel and adipose-derived stem cells were isolated by enzymatic digestion as previously reported elsewhere for adipose tissue. Cultures were kept until confluency and subsequently were subjected to differentiation protocols to evaluate adipogenic, osteogenic, and chondrogenic potential. The morphology of resultant camel adipose-derived stem cells appeared to be spindle-shaped fibroblastic morphology, and these cells retained their biological properties during in vitro expansion with no sign of abnormality in karyotype. Under inductive conditions, primary adipose-derived stem cells maintained their lineage differentiation potential into adipogenic, osteogenic, and chondrogenic lineages during subsequent passages. Our observation showed that like human lipoaspirate, camel adipose tissue also contain multi-potent cells and may represent an important stem cell source both for veterinary cell therapy and preclinical studies as well.

Functional Significance of MPL Expression in the Human Primitive Hematopoietic Stem Cell Compartment

Abstract 1195 Background:In the murine primitive hematopoietic stem cell (HSC) compartment, MPL/thrombopoietin (THPO) signaling plays an important role for the maintenance of adult quiescent HSCs. However, the role of MPL/THPO signaling in the human primitive HSC compartment has not yet been elucidated. We have previously identified very primitive human cord blood (CB)-derived CD34-negative (CD34−) severe combined immunodeficiency (SCID)-repopulating cells (SRCs) using the intra-bone marrow injection (IBMI) method (Blood 2003:101;2924). Recently, we developed a high-resolution purification method for the primitive CD34− SRCs using 18 lineage (Lin)-specific antibodies (Exp Hematol 2011:39:203). In this study, we investigated the functional significance of the MPL expression in the human primitive CD34− SRCs (HSCs). Materials and Methods:First, we sorted 18Lin−CD34+/−MPL+/−cells by FACS. Thereafter, these four fractions of cells were analyzed for their hematopoietic colony-forming capacities (CFCs), the maintenance/production of CD34+ cells in cocultures with human bone marrow-derived mesenchymal stromal cells (DP MSCs) (Blood 2010:116:1575). Finally, these four fractions of cells were transplanted by IBMI into NOD/Shi-scid/IL-2R ƒÁcnull (NOG) mice to investigate their long-term (LT) repopulating capacities. We performed primary, secondary, and tertiary transplantations for up to 18 months. Results:The CFCs of highly purified 18Lin−CD34−cells were quite unique, since they yielded mainly erythroid-bursts (BFU-E) and erythro/megakaryocytes-containing mixed colonies (CFU-EM). Interestingly, they showed very weak myeloid CFCs. Moreover, 200 18Lin−CD34−MPL+cells yielded about 150 colonies, consisting of 20% BFU-E, 20% colony-forming unit-megakaryocytes, and 60% CFU-EM in the presence of 10% platelet-poor plasma, THPO, IL-3, and erythropoietin. The phenotypic and functional characteristics of the 18Lin−CD34+/−MPL+/−cells were further investigated by cocultures with DP MSCs. After 7 days of coculturing the 18Lin−CD34+MPL+/−cells, the total number of cells was observed to expand by about 500 times, 40 % of which consisted of CD34+ cells. On the other hand, the 18Lin−CD34−MPL+/−cells expanded only by about 100 times, 10 to 20% of which consisted of CD34+ cells. Interestingly, the lineage differentiation potentials of the observed 18Lin−CD34+/−MPL+/−cells were significantly different. The percentages of myeloid cells generated from the 18Lin−CD34+MPL+/−cells were significantly greater than those of the 18Lin−CD34−MPL+/−cells. On the contrary, 18Lin−CD34−MPL+cells generated significantly higher percentages of CD41+ cells compared to the other fractions. These observations suggested that the differentiation potentials of 18Lin−CD34+/−MPL+/− cells were different and that these four cell populations contained distinct classes of hematopoietic progenitors as well as HSCs. We next investigated the SRC activities of the 18Lin−CD34+/−MPL+/−cells using NOG mice. In the primary recipient mice, all 18 mice (9 for each cell type) received CD34+MPL+/−SRCs were highly repopulated with human CD45+ cells. On the other hand, 11/13 mice receiving CD34−MPL+SRCs and 12/12 mice receiving CD34−MPL−SRCs showed human cell repopulation. Interestingly, these CD34+/−MPL+/−SRCs showed different repopulation kinetics. The CD34+MPL+ SRCs showed a rapid and sustained repopulating pattern (Fig.1-A). In contrast, the repopulation rates in the mice receiving CD34+MPL− and CD34−MPL+/− SRCs gradually increased, and thereafter reached a high level of repopulation at 18–24 weeks after the transplantation (Fig.1-A, B). All of the primary recipient mice that received CD34+MPL+/− SRCs showed a secondary repopulating capacity. However, only the mice that received CD34+MPL− SRCs showed a tertiary repopulating capacity. Very interestingly, the primary recipient mice that received CD34−MPL− SRCs showed a distinct secondary repopulating capacity. Tertiary transplantation experiments in these mice are now underway in our laboratory. Conclusion:These results clearly indicated that both the CD34+/− SRCs not expressing MPL sustained a LT (> 1 year) human cell repopulation in NOG mice. Therefore, these findings suggest that the functional significance of the MPL expression in the human primitive HSCs is different from that in murine primitive HSCs. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Notch signals contribute to preserve the multipotentiality of human CD34+CD38−CD45RA−CD90+ hematopoietic progenitors by maintaining T cell lineage differentiation potential

Notch signals are critical for T-cell development, limiting the differentiation potential of multipotent progenitors arriving in the thymus via the bloodstream. Notch ligands Delta-like and Jagged are expressed in the bone marrow and, consequently, a role in the regulation of early events of adult hematopoiesis has been proposed. However, mice with disruptions in the Notch pathway do not show gross defects in the hematopoietic stem cell compartment, limiting Notcheffects at later stages of development. In this study, we identify cord blood CD34(+)CD38(-)CD45RA(-)CD90(+) cells, a recently described population of hematopoietic stem cells, as one of the earliest targets of Notch in human hematopoiesis. Upon Notch activation, CD34(+)CD38(-) cells are blocked in their differentiation at the CD34(+)CD38(-)CD45RA(-)CD90(+) stage. Importantly, population and clonal analysis demonstrate that Delta-like-1 exposure does not affect lymphoid vs myeloid decisions. However, Notch signaling is required before lymphoid commitment to preserve T-cell potential of CD34(+)CD38(-)CD45RA(-)CD90(+) cells.Our experiments also show that in terms of differentiation potential, CD34(+)CD38(-)CD45RA(-)CD90(+) cells cultured in the presence of Notch signals, resemble cells directly isolated from cord blood. These results could have implications for translational efforts in the design of strategies aimed to accelerate immune reconstitution after transplantation.

Comparison of the biological characteristics of serum-free and fetal bovine serum-contained medium cultured umbilical cord-derived mesenchymal stem cells

To compare the differences of biological characteristics between human umbilical cord-derived mesenchymal stem cells (UC-MSCs) cultured by serum-free medium or fetal bovine serum-contained complete medium to establish a xenogeneic protein-free UC-MSCs culture system. Healthy human umbilical cord segments were digested with collagenase. UC-MSCs were cultured by serum-free MesenCult-XF medium and FBS-based αMEM complete medium, then analyzed the morphology, immunophenotype, expansion potential, lineage differentiation potential, karyotype and immunosuppression of early passages. The average cell diameters of UC-MSCs in suspension cultured by serum-free medium and FBS-based medium were 26 (18 - 39) µm and 35 (20 - 61) µm, respectively. Cell expansion folds with serum free medium and FBS-based medium were (5.2 ± 0.2) and (3.5 ± 0.1) respectively, in the first five passages. The expansion potential of serum-free medium cultured UC-MSCs was significantly higher than FBS-based medium cultured ones (P < 0.05). A panel of markers CD29, CD44, CD90, CD73, CD105 and HLA-ABC expressed on human UC-MSCs. Hematopoietic lineage markers CD34, CD45 and HLA-DR were not detectable on UC-MSCs. The cpm were (4.57 ± 0.14)×10(4), (2.04 ± 0.16)×10(4) and (0.42 ± 0.04)×10(4), respectively when serum-free medium cultured MSCs were added to the cultures at MSCs/T cell ratios of 1:100, 1:10 and 1:5. While the cpm was (4.57 ± 0.14)×10(4), (2.04 ± 0.16)×10(4) and (0.42 ± 0.04)×10(4), respectively when serum-free medium cultured UC-MSCs were added to the cultures. The immunosuppressive potential of serum-free medium-cultured UC-MSCs was higher than serum-contained medium cultured ones at three different MSC/T cell ratios (P < 0.05). Compare with serum-contained medium cultured early passages of UC-MSCs, the cell diameter of serum-free medium cultured UC-MSCs was smaller with higher expansion potential. No xenogeneic proteins were presented in UC-MSCs preparations when cultured with serum-free medium. Human UC-MSCs suppressed T-cell proliferation in a dose-dependent manner. The immunosuppressive potential of serum-free medium cultured UC-MSCs was higher than FBS-based medium cultured ones.

Molecular signature and in vivo behavior of bone marrow endosteal and subendosteal stromal cell populations and their relevance to hematopoiesis

In the bone marrow cavity, hematopoietic stem cells (HSC) have been shown to reside in the endosteal and subendosteal perivascular niches, which play specific roles on HSC maintenance. Although cells with long-term ability to reconstitute full hematopoietic system can be isolated from both niches, several data support a heterogenous distribution regarding the cycling behavior of HSC. Whether this distinct behavior depends upon the role played by the stromal populations which distinctly create these two niches is a question that remains open. In the present report, we used our previously described in vivo assay to demonstrate that endosteal and subendosteal stromal populations are very distinct regarding skeletal lineage differentiation potential. This was further supported by a microarray-based analysis, which also demonstrated that these two stromal populations play distinct, albeit complementary, roles in HSC niche. Both stromal populations were preferentially isolated from the trabecular region and behave distinctly in vitro, as previously reported. Even though these two niches are organized in a very close range, in vivo assays and molecular analyses allowed us to identify endosteal stroma (F-OST) cells as fully committed osteoblasts and subendosteal stroma (F-RET) cells as uncommitted mesenchymal cells mainly represented by perivascular reticular cells expressing high levels of chemokine ligand, CXCL12. Interestingly, a number of cytokines and growth factors including interleukin-6 (IL-6), IL-7, IL-15, Hepatocyte growth factor (HGF) and stem cell factor (SCF) matrix metalloproteases (MMPs) were also found to be differentially expressed by F-OST and F-RET cells. Further microarray analyses indicated important mechanisms used by the two stromal compartments in order to create and coordinate the “quiescent” and “proliferative” niches in which hematopoietic stem cells and progenitors reside.

Efficient isolation and enrichment of mesenchymal stem cells from bone marrow

Bone marrow (BM) mesenchymal stromal cells (MSC) have been identified as a source of pluripotent stem cells used in clinical practice to regenerate damaged tissues. BM MSC are commonly isolated from BM by density-gradient centrifugation. This process is an open system that increases the risk of sample contamination. It is also time consuming and requires technical expertise that may result in variability regarding cellular recovery. The BD Vacutainer® Cell Preparation Tube™ (CPT) was conceived to separate mononuclear cells from peripheral blood. The main goal of this study was to verify whether MSC could be isolated from BM using the CPT. BM was harvested, divided into two equal aliquots and processed using either CPT or a Ficoll-Paque™ PREMIUM density gradient. Both methods were compared regarding cell recovery, viability, proliferation, differentiation capacities and the presence of MSC progenitors. Similar numbers of mononuclear cells were isolated from BM when comparing the two methods under study. No differences were found in terms of phenotypic characterization, viability, kinetics and lineage differentiation potential of MSC derived by CPT or Ficoll. Surprisingly, a fibroblast-colony-forming unit (CFU-F) assay indicated that, with CPT, the number of MSC progenitors was 1.8 times higher compared with the Ficoll gradient separation. The CPT method is able to isolate MSC efficiently from BM, allowing the enrichment of MSC precursors.

Cell Senescence: A Challenge in Cartilage Engineering and Regeneration

Cartilage defects, most commonly caused by aging and degenerative disease, have become the primary target of cartilage tissue engineering due to a lack of effective treatments and limited regenerative abilities. The limited success of autologous chondrocyte implantation necessitates the development of alternative cell sources. Adult mesenchymal stem cells (MSCs) with multiple lineage differentiation potentials from various sources can supplement the shortage of human autologous chondrocytes. However, cell senescence presents a big challenge for large-scale ex vivo expansion and maintenance of MSC stemness. In this review, we will summarize some potential factors resulting in cell senescence during cartilage tissue engineering, including ex vivo expansion, donor age, and degenerative diseases, and the challenge in the identification of senescent cells. The presence of senescence-associated β-galacotosidase and DNA damage, accumulation of reactive oxygen species, the decline of DNA replication and telomerase activity, and shortened telomere length is indicative of senescence, but none of them are specific. To some extent, growth factors, antioxidants, serum deprivation, or platelet-rich plasma treatment as well as low oxygen have been successful in retarding cell senescence. Recently, decellurized extracellular matrix, especially decellularized stem cell matrix, has emerged as a more promising tool in retaining cells in a younger state. Some potential signaling pathways in cell senescence will also be discussed for their potential involvement in cartilage regeneration despite the fact that comprehensive mechanisms are still under investigation.

In vitro differentiation of human skin-derived multipotent stromal cells into putative endothelial-like cells

BackgroundMultipotent stem cells have been successfully isolated from various tissues and are currently utilized for tissue-engineering and cell-based therapies. Among the many sources, skin has recently emerged as an attractive source for multipotent cells because of its abundance. Recent literature showed that skin stromal cells (SSCs) possess mesoderm lineage differentiation potential; however, the endothelial differentiation and angiogenic potential of SSC remains elusive. In our study, SSCs were isolated from human neonatal foreskin (hNFSSCs) and adult dermal skin (hADSSCs) using explants cultures and were compared with bone marrow (hMSC-TERT) and adipose tissue-derived mesenchymal stem cells (hADMSCs) for their potential differentiation into osteoblasts, adipocytes, and endothelial cells.ResultsConcordant with previous studies, both MSCs and SSCs showed similar morphology, surface protein expression, and were able to differentiate into osteoblasts and adipocytes. Using an endothelial induction culture system combined with an in vitro matrigel angiogenesis assay, hNFSSCs and hADSSCs exhibited the highest tube-forming capability, which was similar to those formed by human umbilical vein endothelial cells (HUVEC), with hNFSSCs forming the most tightly packed, longest, and largest diameter tubules among the three cell types. CD146 was highly expressed on hNFSSCs and HUVEC followed by hADSSCs, and hMSC-TERT, while its expression was almost absent on hADMSCs. Similarly, higher vascular density (based on the expression of CD31, CD34, vWF, CD146 and SMA) was observed in neonatal skin, followed by adult dermal skin and adipose tissue. Thus, our preliminary data indicated a plausible relationship between vascular densities, and the expression of CD146 on multipotent cells derived from those tissues.ConclusionsOur data is the first to demonstrate that human dermal skin stromal cells can be differentiated into endothelial lineage. Hence, SSCs represents a novel source of stem/stromal cells for tissue regeneration and the vascularization of engineered tissues. Moreover, the CD146 investigations suggested that the microenvironmental niche might contribute to direct stromal cells multipotency toward certain lineages, which warrants further investigation.

Abstract P014: Oxidative Stress Mediated Regulation of Antioxidants in Cardiac Progenitor Cells

Cardiac diseases are the leading causes of death throughout the world and transplantation of endogenous myocardial progenitor population with robust cardiovascular lineage differentiation potential is a promising therapeutic strategy. Therefore, in vitro expansion and transplantation of cardiac progenitor cells (CPCs) is currently in early clinical testing as a potential treatment for severe cardiac dysfunction. However, poor survival and engraftment of cells is one of the major limitations of cell transplantation therapy. Oxidative stress is increased in the ischemic myocardium and indirect inferences suggest the vulnerability of CPCs to oxidative stress. In this study, we show that in vitro, resident c-kit positive CPCs isolated from rat myocardium are significantly (p&lt;0.05) resistant to superoxide-induced apoptosis compared to cardiomyocytes as analyzed by the number of sub-G1 population following xanthine/xanthine oxidase treatment. Interestingly, CPCs have two to four fold higher basal SOD1 and SOD2 activities (p&lt;0.01) compared to cardiomyocytes and endothelial cells. Superoxide treatment increased expression of SOD1 (p&lt;0.01), SOD2 (p&lt;0.01), and glutathione peroxidase (p&lt;0.05) mRNAs within 6 h of treatment compared to control cells. Recent studies suggest the involvement of AKT in controlling cell death, survival and also expression of SOD enzymes. Therefore, we investigated the involvement of AKT in CPCs subjected to oxidative stress. Western blot analysis revealed that the amount of phosphorylated AKT increased significantly within 10 minutes of xanthine/xanthine oxidase treatment. In addition, treatment with LY294002 - a PI3 kinase/AKT inhibitor, increased apoptosis in CPCs treated with superoxide. Our studies demonstrate a novel finding in which resident progenitor cells are protected from oxidative injury by containing higher basal levels of antioxidants as compared to myocytes. Moreover, under oxidant challenge antioxidant levels are regulated, possibly in an AKT-dependent manner. Further elucidation of this pathway may lead to novel therapeutic opportunities.