Distinct Cell Lineages Research Articles

Human Endometrial-Derived Mesenchymal Stem Cells Suppress Inflammation in the Central Nervous System of EAE Mice

Mesenchymal stromal cells (MSCs) are undifferentiated multipotent cells endowed with the capacity for self-renewal and the potential to differentiate into several distinct cell lineages [1]. It is well established that adult MSCs constitute a reservoir found within connective tissues of most organs, and whose biological function is involved in the maintenance and repair of tissues throughout the postnatal life of an individual. Over the past years we and others have shown that menstrual blood, the endometrium and fallopian tubes are very rich sources of MSCs and able to differentiate into different cell lineages in vitro and/or in vivo [2, 3]. The unique regenerative capacity of the human endometrium following menstruation, postpartum, surgical procedures (uterine curettage, endometrial ablation) and in postmenopausal women undergoing hormonal replacement therapy suggests that MSCs niches present in this tissue are responsible, at least in part, for this process. This makes these cells a very interesting approach to studies in regenerative medicine, especially in autoimmune disorders. Multiple sclerosis (MS) is a debilitating and neurodegenerative autoimmune disease with a significant social burden. It is mainly characterized by central nervous system (CNS) inflammation, gliosis, neuronal death and demyelination [4, 5]. Its murine model, experimental autoimmune encephalomyelitis (EAE), has generated many important data concerning MS pathology and treatment [6–9]. In EAE, mice are subcutaneously immunized with myelin-derived antigens such as myelin oligodendrocyte glycoprotein (MOG35-55), myelin basic protein (MBP) and also proteolipoprotein (PLP) [6]. In the periphery T CD4 cells differentiate into Th1 and Th17 cells and have been implicated in the pathogenesis of EAE [10–12]. Although IFN-γ and ILStem Cell Rev and Rep (2012) 8:940–952 DOI 10.1007/s12015-011-9338-3

Generation of Melanocytes from Induced Pluripotent Stem Cells

Epidermal melanocytes play an important role in protecting skin from ultraviolet (UV) rays, and are implicated in a variety of skin diseases. Here, we developed an efficient method for differentiating induced pluripotent stem cells (iPSCs) into melanocytes. We first generated iPSCs from adult mouse tail-tip fibroblasts (TTFs) using retroviral vectors or virus-free piggyBac transposon vectors carrying murine Sox2, Oct3/4, cMyc and Klf4. The TTF-derived iPSC clones exhibited similar morphology and growth properties as mouse embryonic stem (ES) cells. The iPSCs expressed ES cell markers, displayed characteristic epigenetic changes and formed teratomas with all three germ layers. The iPSCs were used to generate embryoid bodies (EBs) and were then successfully differentiated into melanocytes by treatment with growth factors. The iPSC-derived melanocytes expressed characteristic melanocyte markers and produced melanin pigment. Electron microscopy showed that the melanocytes contained mature melanosomes. We manipulated the conditions used to differentiate iPSCs to melanocytes and discovered that Wnt3a is not required for mouse melanocyte differentiation. This report shows that melanocytes can be readily generated from iPSCs, providing a powerful resource for the in vitro study of melanocyte developmental biology and diseases. By inducing iPSCs without viruses, the possibility of integration mutagenesis is alleviated, providing iPSCs are more compatible for cell replacement therapies.

Evolutionary relationships and diversification of barhl genes within retinal cell lineages

BackgroundBasic helix-loop-helix and homeodomain transcription factors have been shown to specify all different neuronal cell subtypes composing the vertebrate retina. The appearance of gene paralogs of such retina-specific transcription factors in lower vertebrates, with differently evolved function and/or conserved non-coding elements, might provide an important source for the generation of neuronal diversity within the vertebrate retinal architecture. In line with this hypothesis, we investigated the evolution of the homeobox Barhl family of transcription factors, barhl1 and barhl2, in the teleost and tetrapod lineages. In tetrapod barhl2, but not barhl1, is expressed in the retina and is important for amacrine cell specification. Zebrafish has three barhl paralogs: barhl1.1, barhl1.2 and barhl2, but their precise spatio-temporal retinal expression, as well as their function is yet unknown.ResultsHere we performed a meticulous expression pattern comparison of all known barhl fish paralogs and described a novel barhl paralog in medaka. Our detailed analysis of zebrafish barhl gene expression in wild type and mutant retinas revealed that only barhl1.2 and barhl2 are present in the retina. We also showed that these two paralogs are expressed in distinct neuronal lineages and are differently regulated by Atoh7, a key retinal-specific transcription factor. Finally, we found that the two retained medaka fish barhl paralogs, barhl1 and barhl2, are both expressed in the retina, in a pattern reminiscent of zebrafish barhl1.2 and barhl2 respectively. By performing phylogenetic and synteny analysis, we provide evidence that barhl retinal expression domain is an ancestral feature, probably lost in tetrapods due to functional redundancy.ConclusionsFunctional differences among retained paralogs of key retina-specific transcription factors between teleosts and tetrapods might provide important clues for understanding their potential impact on the generation of retinal neuronal diversity. Intriguingly, within teleosts, retention of zebrafish barhl1.2 and its medaka ortholog barhl1 appears to correlate with the acquisition of distinct signalling mechanisms by the two genes within distinct retinal cell lineages. Our findings provide a starting point for the study of barhl gene evolution in relation to the generation of cell diversity in the vertebrate retina.

Efficient Generation of iPS Cells from Skeletal Muscle Stem Cells

Reprogramming of somatic cells into inducible pluripotent stem cells generally occurs at low efficiency, although what limits reprogramming of particular cell types is poorly understood. Recent data suggest that the differentiation status of the cell targeted for reprogramming may influence its susceptibility to reprogramming as well as the differentiation potential of the induced pluripotent stem (iPS) cells that are derived from it. To assess directly the influence of lineage commitment on iPS cell derivation and differentiation, we evaluated reprogramming in adult stem cell and mature cell populations residing in skeletal muscle. Our data using clonal assays and a second-generation inducible reprogramming system indicate that stem cells found in mouse muscle, including resident satellite cells and mesenchymal progenitors, reprogram with significantly greater efficiency than their more differentiated daughters (myoblasts and fibroblasts). However, in contrast to previous reports, we find no evidence of biased differentiation potential among iPS cells derived from myogenically committed cells. These data support the notion that adult stem cells reprogram more efficiently than terminally differentiated cells, and argue against the suggestion that “epigenetic memory” significantly influences the differentiation potential of iPS cells derived from distinct somatic cell lineages in skeletal muscle.

Generation of human induced pluripotent stem cells from osteoarthritis patient-derived synovial cells

This study was undertaken to generate and characterize human induced pluripotent stem cells (PSCs) from patients with osteoarthritis (OA) and to examine whether these cells can be developed into disease-relevant cell types for use in disease modeling and drug discovery. Human synovial cells isolated from two 71-year-old women with advanced OA were characterized and reprogrammed into induced PSCs by ectopic expression of 4 transcription factors (Oct-4, SOX2, Klf4, and c-Myc). The pluripotency status of each induced PSC line was validated by comparison with human embryonic stem cells (ESCs). We found that OA patient-derived human synovial cells had human mesenchymal stem cell (MSC)-like characteristics, as indicated by the expression of specific markers, including CD14-, CD19-, CD34-, CD45-, CD44+, CD51+, CD90+, CD105+, and CD147+. Microarray analysis of human MSCs and human synovial cells further determined their unique and overlapping gene expression patterns. The pluripotency of established human induced PSCs was confirmed by their human ESC-like morphology, expression of pluripotency markers, gene expression profiles, epigenetic status, normal karyotype, and in vitro and in vivo differentiation potential. The potential of human induced PSCs to differentiate into distinct mesenchymal cell lineages, such as osteoblasts, adipocytes, and chondrocytes, was further confirmed by positive expression of markers for respective cell types and positive staining with alizarin red S (osteoblasts), oil red O (adipocytes), or Alcian blue (chondrocytes). Functional chondrocyte differentiation of induced PSCs in pellet culture and 3-dimensional polycaprolactone scaffold culture was assessed by chondrocyte self-assembly and histology. Our findings indicate that patient-derived synovial cells are an attractive source of MSCs as well as induced PSCs and have the potential to advance cartilage tissue engineering and cell-based models of cartilage defects.

Gut inflammation and indoleamine deoxygenase inhibit IL-17 production and promote cytotoxic potential in NKp44+ mucosal NK cells during SIV infection

AbstractNatural killer (NK) cells are classically viewed as effector cells that kill virus-infected and neoplastic cells, but recent studies have identified a rare mucosal NK- cell subpopulation secreting the TH17 cytokine IL-22. Here, we report identification of 2 distinct lineages of mucosal NK cells characterized as NKG2A+NFIL3+RORC– and NKp44+NFIL3+RORC+. NKG2A+ NK cells were systemically distributed, cytotoxic, and secreted IFN-γ, whereas NKp44+ NK cells were mucosae-restricted, noncytotoxic, and produced IL-22 and IL-17. During SIV infection, NKp44+ NK cells became apoptotic, were depleted, and had an altered functional profile characterized by decreased IL-17 secretion; increased IFN-γ secretion; and, surprisingly, increased potential for cytotoxicity. NKp44+ NK cells showed no evidence of direct SIV infection; rather, depletion and altered function were associated with SIV-induced up-regulation of inflammatory mediators in the gut, including indoleamine 2,3-dioxygenase 1. Furthermore, treatment of NKp44+ NK cells with indoleamine 2,3-dioxygenase 1 catabolites in vitro ablated IL-17 production in a dose-dependent manner, whereas other NK-cell functions were unaffected. Thus lentiviral infection both depletes and modifies the functional repertoire of mucosal NK cells involved in the maintenance of gut integrity, a finding that highlights the plasticity of this rare mucosal NK-cell population.

Epigenetic modifications: basic mechanisms and role in cardiovascular disease.

The term epigenetics was first used to refer to the complex interactions between the genome and the environment that are involved in development and differentiation in higher organisms. Today, this term is used to refer to heritable alterations that are not due to changes in DNA sequence. Rather, epigenetic modifications, or tags, such as DNA methylation and histone modification, alter DNA accessibility and chromatin structure, thereby regulating patterns of gene expression. These processes are crucial to normal development and differentiation of distinct cell lineages in the adult organism. They can be modified by exogenous influences, and as such, they can contribute to or be the result of environmental alterations of phenotype or pathophenotype. Importantly, epigenetic programming has a crucial role in the regulation of pluripotency genes, which become inactivated during differentiation. Here, we review the major mechanisms in epigenetic regulation; highlight the role of stable, long-term epigenetic modifications that involve DNA methylation; and discuss those modifications that are more flexible (short-term) and involve histone modifications, such as methylation and acetylation. We will also discuss the role of nutritional and environmental challenges in generational inheritance and epigenetic modifications, concentrating on examples that relate to complex cardiovascular diseases, and specifically dissect the mechanisms by which homocysteine modifies epigenetic tags. Lastly, we will discuss the possibilities of modifying therapeutically acquired epigenetic tags, summarizing currently available agents and speculating on future directions. Chromatin is the complex of chromosomal DNA associated with proteins in the nucleus (for review, see Campos and Reinberg1). DNA in chromatin is packaged around histone proteins, in units referred to as nucleosomes. A nucleosome has 147 base pairs of DNA associated with an octomeric core of histone proteins, which consists of 2 H3-H4 histone dimers surrounded by 2 H2A-H2B dimers. N-terminal histone tails protrude from nucleosomes into the nuclear lumen. …

The Cdk4-E2f1 pathway regulates early pancreas development by targeting Pdx1+ progenitors and Ngn3+ endocrine precursors

Cell division and cell differentiation are intricately regulated processes vital to organ development. Cyclin-dependent kinases (Cdks) are master regulators of the cell cycle that orchestrate the cell division and differentiation programs. Cdk1 is essential to drive cell division and is required for the first embryonic divisions, whereas Cdks 2, 4 and 6 are dispensable for organogenesis but vital for tissue-specific cell development. Here, we illustrate an important role for Cdk4 in regulating early pancreas development. Pancreatic development involves extensive morphogenesis, proliferation and differentiation of the epithelium to give rise to the distinct cell lineages of the adult pancreas. The cell cycle molecules that specify lineage commitment within the early pancreas are unknown. We show that Cdk4 and its downstream transcription factor E2f1 regulate mouse pancreas development prior to and during the secondary transition. Cdk4 deficiency reduces embryonic pancreas size owing to impaired mesenchyme development and fewer Pdx1(+) pancreatic progenitor cells. Expression of activated Cdk4(R24C) kinase leads to increased Nkx2.2(+) and Nkx6.1(+) cells and a rise in the number and proliferation of Ngn3(+) endocrine precursors, resulting in expansion of the β cell lineage. We show that E2f1 binds and activates the Ngn3 promoter to modulate Ngn3 expression levels in the embryonic pancreas in a Cdk4-dependent manner. These results suggest that Cdk4 promotes β cell development by directing E2f1-mediated activation of Ngn3 and increasing the pool of endocrine precursors, and identify Cdk4 as an important regulator of early pancreas development that modulates the proliferation potential of pancreatic progenitors and endocrine precursors.

Eomesodermin and T-bet each specify a distinct natural killer cell lineage (153.36)

Abstract Natural killer (NK) cells play a critical role in host defense against tumors and intracellular pathogens. Eomesodermin (Eomes) and T-bet are T-box transcription factors that direct fate and function in cytotoxic lineages, such as CD8+ T cells and NK cells. Eomes and T-bet redundantly regulate differentiation of CD8+ effector T cells. Here we report that Eomes and T-bet play complementary and non-redundant roles in NK cell development. We find that conventional, CD49b-expressing (DX5+) NK cells fail to develop in the absence of Eomes. T-bet, however, is dispensable for the formation of conventional NK cells, even though this lineage expresses both T-bet and Eomes. Eomes-dependent, DX5+ NK cells are absent in neonatal mice. Instead, non-canonical, immature-appearing NK cells, characterized by the expression of the death ligand TRAIL, comprise the early neonatal NK cell repertoire. Non-canonical NK cells express T-bet but not Eomes and are absent in animals lacking T-bet. T-bet-dependent, TRAIL+ NK cells are less prevalent in lymphoid tissue of adult mice but represent a major subset of NK cells in the adult liver. In animals lacking both Eomes and T-bet, we find that neither Eomes-dependent, DX5+ NK cells nor T-bet-dependent, TRAIL+ NK cells develop, and that double mutant mice are devoid of all NK cells. Eomes and T-bet thus coordinate transcriptional programs required for development of two genetically, phenotypically, and functionally distinct NK cell lineages.

Dynamics of Polycomb and Trithorax activities during development

Dynamic changes in gene expression are tightly controlled during development, as a single totipotent zygote gives rise to distinct cell lineages. The establishment and maintenance of these diverse transcriptional programs rely on changes of chromatin state, mainly through histone modifications. Polycomb and Trithorax complexes participate in setting apart active and inactive genes by respectively repressing and activating key developmental regulators in different cell types. Over the last decade, our understanding of the biochemical mechanisms underlying their activities has greatly improved, but the signals targeting these proteins to specific regions of the genome are still poorly understood, particularly in vertebrates. Recent findings highlight the highly dynamic activities of Polycomb and Trithorax complexes in vivo. Surprisingly, although their role in transcriptional regulation is deeply conserved during evolution, the time sequence in which they act seems to vary across species.

Growth and Long-Term Somatic and Germline Chimerism Following Fusion of Juvenile Botryllus schlosseri

The colonial ascidian Botryllus schlosseri undergoes a histocompatibility reaction that can result in vascular fusion of distinct genotypes, creating a chimera. Chimerism has both potential benefits, such as an immediate increase in size that may enhance growth rates, and costs. For the latter, the presence of multiple genotypes in a chimera can lead to competition between genetically distinct stem cell lineages, resulting in complete replacement of somatic and germline tissues by a single genotype. Although fusion can occur at any point after metamorphosis, previous studies have focused on chimeras created from sexually mature adults, where no benefit to chimerism has been documented. Here we focus on the costs and benefits of fusion between juveniles, characterizing growth rates and patterns of somatic and germline chimerism after natural and controlled fusion events. We also compared outcomes between low- and high-density growth conditions, the latter more likely representative of what occurs in natural populations. We found that growth rates were density-dependent, and that only chimeras grew under high-density conditions. We also observed a positional component to a post-fusion event called resorption, indicating that extrinsic factors were important in this process. Patterns of germline and somatic chimerism and dominance in chimeras made from fused juveniles were equivalent to those after fusion of sexually mature adults, and there were no age-related differences in these processes. Finally, by using genetic markers that could retrospectively assign genotypes, we also found that the majority of individual testes in a chimera were clonally derived.

Liver Cancer Stem Cells

Hepatocellular carcinoma is the most common primary malignancy of the liver in adults. It is also the fifth most common solid cancer worldwide and the third leading cause of cancer-related death. Recent research supports that liver cancer is a disease of adult stem cells. From the models of experimental hepatocarcinogenesis, there may be at least three distinct cell lineages with progenitor properties susceptible to neoplastic transformation. Identification of specific cell surface markers for each of the liver cell types, production of corresponding monoclonal antibodies and cell sorting techniques have together revolutionized the characteristics of normal stem cells. In hepatocarcinogenesis, multiple signaling transduction pathways, important for stem cell proliferation and differentiations, are deregulated. Strategies are being developed to identify and characterize the liver cancer stem cells. Targeting liver cancer stem cells may bring hope to curing hepatocellular carcinoma.

Applications of myeloid-specific promoters in transgenic mice support in vivo imaging and functional genomics but do not support the concept of distinct macrophage and dendritic cell lineages or roles in immunity

Myeloid lineage cells contribute to innate and acquired immunity, homeostasis, wound repair, and inflammation. There is considerable interest in manipulation of their function in transgenic mice using myeloid-specific promoters. This review considers the applications and specificity of some of the most widely studied transgenes, driven by promoter elements of the lysM, csf1r, CD11c, CD68, macrophage SRA, and CD11b genes, as well as several others. Transgenes have been used in mice to generate myeloid lineage-specific cell ablation, expression of genes of interest, including fluorescent reporters, or deletion via recombination. In general, the specificity of such transgenes has been overinterpreted, and none of them provide well-documented, reliable, differential expression in any specific myeloid cell subset, macrophages, granulocytes, or myeloid DCs. Nevertheless, they have proved valuable in cell isolation, functional genomics, and live imaging of myeloid cell behavior in many different pathologies.

Fetal and Adult Hematopoietic Stem Cells Give Rise to Distinct T Cell Lineages in Humans

Although the mammalian immune system is generally thought to develop in a linear fashion, findings in avian and murine species argue instead for the developmentally ordered appearance (or "layering") of distinct hematopoietic stem cells (HSCs) that give rise to distinct lymphocyte lineages at different stages of development. Here we provide evidence of an analogous layered immune system in humans. Our results suggest that fetal and adult T cells are distinct populations that arise from different populations of HSCs that are present at different stages of development. We also provide evidence that the fetal T cell lineage is biased toward immune tolerance. These observations offer a mechanistic explanation for the tolerogenic properties of the developing fetus and for variable degrees of immune responsiveness at birth.

Establishing Three Blastocyst Lineages--Then What?

Development of the mouse embryo to the blastocyst stage occurs over 3 to 4 days following fertilization of the oocyte. During this time, several molecular and morphological events take place that result in the formation of three distinct cell lineages: the trophectoderm, the epiblast, and the primitive endoderm. Many studies have investigated the processes that control lineage specification in the blastocyst including gene expression, cell signaling, cell-cell contact/positional relationships, and most recently, epigenetics. Here we review, at the molecular level, recent contributions to our understanding of the mechanisms that play a role in formation of these lineages. Additionally, we focus on the next steps in differentiation to highlight processes important in the development of those lineages that contribute to the extraembryonic tissues. In this context, we discuss the establishment of extraembryonic ectoderm and the contributions of parietal and visceral endoderm to yolk sac formation.

βig-h3 Regulates Differentiation and Survival of Human Hematopoietic Stem/Progenitor Cells.

AbstractAbstract 2591Adult hematopoietic stem cells (HSC) reside in dedicated niches in the bone marrow (BM). Within this specialized microenvironment, the various interactions of HSC with adhesion molecules on neighbouring cells and extracellular matrix (ECM) components are critical for the maintenance of the HSC population and the concomitant development of the distinct blood cell lineages. Comparative gene-expression profiling of purified HSC identified ECM proteins that are differentially expressed in homeostatic and regenerative conditions. The ECM protein βig-h3 was one of the proteins upregulated in regenerative conditions. Therefore, we characterized the role of βig-h3 in the regulation of HSC self-renewal and differentiation.A comparison between human CD34+ hematopoietic stem/progenitor cells (HSPC) isolated from BM, mobilized peripheral blood (MPB) and umbilical cord blood (UCB), revealed the highest βig-h3 expression in BM-HSPC (3.9-fold increased compared to MPB, 1.7-fold increased compared to CB), which may implie a role for βig-h3 in retaining HSC in the BM.To examine the functional relevance of βig-h3 in HSC, we first increased βig-h3 expression by transducing human HSPC with a lentiviral βig-h3-SIN-GFP expression vector or a control SIN-GFP vector. Over-expression of βig-h3 (80-fold) in HSPC decreased colony-forming-unit-granulocyte-monocyte (CFU-GM) formation from 130 (SEM=47) to 73 (SEM=19, n=3) CFU-GM per 500 plated CD34+ cells, while megakaryopoiesis was accelerated and the number of mature megakaryocytic cells increased from 16% (SEM=6%) to 30% (SEM=7%, n=4) at day 14 of culture. Ectopic expression of βig-h3 did not affect differentiation along the erythroid or granulopoietic lineage. The development of megakaryocytes at the cost of pluripotent CFU-GM suggests that βig-h3 drives differentiation.In addition, βig-h3 expression in HSPC was reduced by two different short-hairpin-RNAs (shRNA) expressed from lentiviral vectors, which resulted in decreased proliferation (from 19.6- to 5.8-fold per input cell at day 13) and increased apoptosis (from 13.5% to 25.3% at day 13) in liquid HSPC cultures, as analyzed by Annexin V staining. Similarly, knock-down of βig-h3 in various cell lines also resulted in a decreased proliferation and increased apoptosis. Knock-down of βig-h3 in primary HSPC dramatically reduced CFU-GM from 73 (SEM=8.7) to 31 (SEM=14.4, n=6) CFU-GM per 500 CD34+ cells plated, and reduced colony-forming-unit-erythrocyte (CFU-E) formation from 30 (SEM=6.5) to 9 (SEM=1.6, n=4) CFU-E per 500 CD34+ cells plated. This can be explained by increased apoptosis of βig-h3 knock-down cells. Notably, co-culture of βig-h3 knock-down HSPC with stromal feeder cells, known to express high levels of βig-h3, showed no difference compared to control HSPC in cobblestone area formation within two weeks, indicating that stromal cells can counteract apoptosis in βig-h3 knock-down cells. Remarkably, long-term-culture CFU-GM (LTC-CFU) formation of HSPC that were co-cultured with stromal cells during two weeks, was even significantly increased (1.9-fold, n=2) in βig-h3 knock-down cells, indicating that decreased endogenous levels of βig-h3 stimulates the maintenance or expansion of HSPC on stroma.In conclusion, ectopic expression of βig-h3 decreased CFU-GM in HSPC and accelerated differentiation towards megakaryocytes, suggesting that βig-h3 might drive lineage commitment of HSC. Conversely, knock-down of βig-h3 in HSPC stimulated LTC-CFU formation, indicating that decreased βig-h3 levels in HSPC maintain their undifferentiated state. In absence of stroma, however, knock-down of βig-h3 induces apoptosis, indicating βig-h3 as an essential survival factor, which expression levels regulate differentiation and maintenance of HSC. Disclosures:No relevant conflicts of interest to declare.

Imatinib Treated Chronic Myelogenous Leukemia Concomitant with Multiple Myeloma. Is There a Relationship?

AbstractAbstract 5005Chronic myelogenous leukemia (CML) and multiple myeloma (MM) are hematological neoplasms with involvement of distinct hematopoietic cell lineages. The simultaneous occurrence of CML and MM is an extremely rare event. We report the case of a 46-year-old asymptomatic patient who was diagnosed with CML after an abnormal white blood cell count (90×109 u/L) was found on a routine complete blood cell count. Physical examination showed only splenomegaly. At diagnosis, a monoclonal protein peak was observed on electrophoresis (0.82g/dL). Bone marrow (BM) biopsy was characterized by granulocyte hyperplasia without clonal plasmacytosis. Karyotype showed t(9;22)(q34.1;q11.2) and a BCR/ABL mRNA transcript was detected by RT-PCR. Cytoreduction was initiated with hydroxyurea for 20 days until imatinib 400 mg/day was initiated. Patient achieved a major molecular response (MMR) after 7 months of treatment and remains in MMR. After 12 months from diagnosis, the patient persisted with monoclonal peak, and a new BM biopsy showed 15% monoclonal plasma cells, compatible with IgG lambda Myeloma. No end-organ damage was found, and there was no indication for therapy. Karyotype was 46, XX and a FISH analysis was positive for IgH rearrangement and for del 13q. At the time of this report the patient persists in MMR for CML with a monoclonal peak of 1.2 g/dL. No evidence of MM progression has been observed. These findings indicate coexistence of CML in chronic phase and monoclonal gamopathy of uncertain significance (MGUS), progressing to smoldering MM IgG lambda during IM treatment. At this moment, the association of CML and MM has been considered coincidental, but it is possible that imatinib may induce changes in phenotype of plasma cells which might lead to progression of multiple myeloma. Disclosures:No relevant conflicts of interest to declare.

Innate Lymphoid Cell Relations

A common progenitor cell gives rise to distinct lineages of innate lymphoid cells in the gastrointestinal tract.

Reversible transdifferentiation of blood vascular endothelial cells to a lymphatic-like phenotype in vitro

Blood vascular cells and lymphatic endothelial cells (BECs and LECs, respectively) form two separate vascular systems and are functionally distinct cell types or lineages with characteristic gene expression profiles. Interconversion between these cell types has not been reported. Here, we show that in conventional in vitro angiogenesis assays, human BECs of fetal or adult origin show altered gene expression that is indicative of transition to a lymphatic-like phenotype. This change occurs in BECs undergoing tubulogenesis in fibrin, collagen or Matrigel assays, but is independent of tube formation per se, because it is not inhibited by a metalloproteinase inhibitor that blocks tubulogenesis. It is also reversible, since cells removed from 3D tubules revert to a BEC expression profile upon monolayer culture. Induction of the lymphatic-like phenotype is partially inhibited by co-culture of HUVECs with perivascular cells. These data reveal an unexpected plasticity in endothelial phenotype, which is regulated by contact with the ECM environment and/or cues from supporting cells.

Reversible transdifferentiation of blood vascular endothelial cells to a lymphatic-like phenotype in vitro

Blood vascular cells and lymphatic endothelial cells (BECs and LECs, respectively) form two separate vascular systems and are functionally distinct cell types or lineages with characteristic gene expression profiles. Interconversion between these cell types has not been reported. Here, we show that in conventional in vitro angiogenesis assays, human BECs of fetal or adult origin show altered gene expression that is indicative of transition to a lymphatic-like phenotype. This change occurs in BECs undergoing tubulogenesis in fibrin, collagen or Matrigel assays, but is independent of tube formation per se, because it is not inhibited by a metalloproteinase inhibitor that blocks tubulogenesis. It is also reversible, since cells removed from 3D tubules revert to a BEC expression profile upon monolayer culture. Induction of the lymphatic-like phenotype is partially inhibited by co-culture of HUVECs with perivascular cells. These data reveal an unexpected plasticity in endothelial phenotype, which is regulated by contact with the ECM environment and/or cues from supporting cells.