Sca-1 Expression Research Articles

AIM2 Co-immunization with VP1 Is Associated with Increased Memory CD8 T Cells and Mounts Long Lasting Protection against Coxsackievirus B3 Challenge.

The recurrent Coxsackievirus B3 (CVB3) infection is the most important cause of intractable myocarditis which often leads to chronic myocarditis and even dilated cardiomyopathy. Therefore, enhanced DNA vaccines capable of memory CD8 T cells are essential for long-lasting immunological protection against CVB3 infection. In this study, absent in melanoma 2 (AIM2) was used as an adjuvant to enhance the induction of memory CD8 T cells elicited by VP1 (viral capsid protein 1) vaccine. Mice were intramuscularly injected with 50 μg AIM2 plasmid and equal amount of VP1 plasmid (pAIM2/pVP1) vaccine 4 times at 2 week-intervals. We observed that the protection of pAIM2/pVP1 vaccine against CVB3 challenge was evidenced by significantly improved cardiac function, reduced myocardial injuries, and increased survival rate when compared with immunization with pVP1. Co-immunization with pAIM2/pVP1 robustly augmented T lymphocytes proliferation and CVB3-specific cytotoxic T lymphocyte responses. Importantly, 16 weeks after the last immunization, pAIM2/pVP1 co-immunization significantly enhanced the expression of Bcl-6, SOCS3, and Sca-1 which are critical for memory CD8 T cells as compared with pVP1 immunization. Notably, CD8 T cells that are likely vaccine-induced memory T cells were responsible for the protective efficacy of pAIM2/pVP1 vaccine by abolition of a CD8 T cell immune response following a lethal dose of CVB3 infection. Our results indicate that AIM2-adjuvanted vaccine could be a potential and promising approach to promote a long-lasting protection against CVB3-induced myocarditis.

Fli-1 overexpression in erythroleukemic cells promotes erythroid de-differentiation while Spi-1/PU.1 exerts the opposite effect.

The ETS transcription factors play a critical role during hematopoiesis. In F-MuLV-induced erythroleukemia, Fli-1 insertional activation producing high expression of this transcription factor required to promote proliferation. How deregulated Fli-1 expression alters the balance between erythroid differentiation and proliferation is unknown. To address this issue, we exogenously overexpressed Fli-1 in an erythroleukemic cell harboring activation of spi-1/PU.1, another ETS gene involved in erythroleukemogenesis. While the proliferation in culture remains unaffected, Fli-1 overexpression imparts morphological and immunohistochemical characteristics of immature erythroid progenitors. Fli-1 overexpression in erythroleukemic cells increased the numbers of erythroid colonies on methylcellulose and reduced tumorigenicity as evidenced by increase latency of erythroleukemogenesis in mice inoculated with these cells. Although all transplanted mice developed enlargement of the spleen and liver due to leukemic infiltration, Fli-1 overexpression altered the hematopoietic phenotype, significantly increasing the expression of regulatory hematopoietic genes cKIT, SCA-1, CD41 and CD71. In contrast, expression of Spi-1/PU.1 in a Fli-1 producing erythroleukemia cell line in which fli-1 is activated, resulted in increased proliferation through activation of growth promoting proteins MAPK, AKT, cMYC and JAK2. Importantly, these progenitors express high levels of markers such as CD71 and TER119 associated with more mature erythroid cells. Thus, Fli-1 overexpression induces a de-differentiation program by reverting CFU-E to BFU-E erythroid progenitor activity, while Spi-1/PU.1 promoting maturation from BFU-E to CFU-E.

SCA-1 Expression Level Identifies Quiescent Hematopoietic Stem and Progenitor Cells.

SummaryBlood cell generation depends on continuous cellular output by the sequential hierarchy of hematopoietic stem cell (HSC) and progenitor populations that all contain quiescent and actively cycling cells. Hematopoietic stem and progenitor cells (HSPCs) express the surface molecule Stem cell antigen 1 (SCA-1/LY6A). Using histone 2B-red fluorescent fusion protein label retention and cell-cycle reporter mice, we demonstrate that high SCA-1 expression (SCA-1hi) identifies not only quiescent HSCs but quiescent cells on all hierarchical levels within the lineage−SCA-1+KIT+ (LSK) population. Each transplanted SCA-1hi HSPC population also displayed self-renewal potential superior to that of the respective SCA-1lo population. SCA-1 expression is inducible by type I interferon (IFN). We show, however, that quiescence and high self-renewal capacity of cells with brighter SCA-1 expression at steady state were independent of type I IFN signaling. We conclude that SCA-1 expression levels can be used to prospectively isolate functionally heterogeneous HSPC subpopulations.

Abstract 643: CX 3 CR1 Identifies Adventitial Macrophage Progenitor Cells (AMPCS), a Local Source of Self-Renewing Macrophages in Postnatal Murine Arteries

Background: Macrophages are integral to vascular biology and disease. Although traditional paradigms assert that vascular macrophages originate from circulating monocytes, recent data suggest that some are seeded in utero from CX 3 CR1 + progenitors, and are maintained postnatally by local self-renewal. We previously identified a novel population of locally-maintained adventitial macrophage progenitor cells (AMPCs) as a source of self-renewing macrophages in adult mouse arteries. Hypothesis: AMPCs express CX 3 CR1 and do not derive from definitive hematopoiesis. Methods: Single-cell disaggregates were prepared from postnatal murine aortas. AMPC content was assessed by macrophage colony-forming unit (CFU-M) assays. Flow cytometry together with fluorescence activated cell sorting (FACS) were used to investigate the immunophenotypic profile of AMPCs and fate-mapping to assess their origins. Results: CFU-M prevalence in C57BL/6J aortic cells was highest in neonatal mice (~100 per 10 5 cells), and diminished progressively with age (~55/10 5 at 3w, ~15/10 5 at 12w, ~5/10 5 at 52w, n>4, P<0.01). Secondary replating of single cells from aortic CFU-M revealed striking self-renewal capacity, with 1 in 10 cells forming new CFU-M (n=8). Undifferentiated CFU-M displayed >95% expression of the stem cell markers Sca-1 and c-Kit, and high levels of CX 3 CR1, but did not acquire the monocyte/macrophage markers CD11b or F4/80 until treated with macrophage-colony stimulating factor (n=6). Mice deficient in CX 3 CR1 (Cx 3 cr1 GFP/GFP ) produced fewer CFU-M than heterozygous (Cx 3 cr1 +/GFP ) littermates (8.7±0.7 vs 15.3±0.7 per 10 5 , P<0.001, n>7). FACS selection confirmed that CFU-M forming AMPCs were exclusively contained within a CX 3 CR1 + subpopulation that did not express either CD11b or F4/80 (n=3). Finally, CFU-M analysis from Flt3 Cre xRosa mT/mG mice demonstrated that AMPCs arise from a FLT3 -ve source, indicating that their origins are independent of definitive hematopoiesis (n=4). Conclusion: Clonogenic, self-renewing murine AMPCs express CX 3 CR1 but not the monocyte/macrophage markers CD11b and F4/80. The high prevalence of AMPCs in neonatal aorta is consistent with prenatal seeding from CX 3 CR1 + progenitors, independent of definitive hematopoiesis.

Activation of Endogenous Cardiac Stem Cells by Apelin-13 in Infarcted Rat Heart.

Our previous study demonstrated that the apelin-APJ pathway contributed to myocardial regeneration and functional recovery after bone marrow-derived mesenchymal stem cell (BM-MSC) transplantation during the differentiation of BM-MSCs into cardiomyogenic cells in acute myocardial infarction (AMI) rat models. However, the underlying mechanisms by which apelin promotes cardiac repair and functional recovery have not been completely clarified. In the present study, we investigated whether apelin could mobilize and activate endogenous cardiac stem cells and progenitors, thereby mediating regeneration and repair of the myocardium after AMI in rat models. Six-week-old male Sprague-Dawley rats underwent AMI and received apelin-13 (200 ng, n = 10) or an equivalent volume of saline by intramyocardial injection (n = 10); there was also a sham operation group (n = 8). Proliferation of endogenous cardiac stem cells was analyzed by immunofluorescence staining in rat infarcted myocardium, and heart function was evaluated by echocardiography at 28 days after apelin-13 injection. Treatment with apelin-13 led to a significant increase of Ki-67+-c-kit+/Sca-1+/Flk-1+ endogenous cardiac stem or progenitor cells in the border zone and infarct zone of rat hearts at 28 days after myocardial infarction (MI). Significant increases in the expression of c-kit, Sca-1, and Flk-1 on both levels of transcription and translation were confirmed by real-time polymerase chain reaction (RT-PCR) and Western blot. Treatment of apelin-13 also resulted in a significant reduction of infarct size and improvement of cardiac function post-MI. We conclude that apelin-13 is able to enhance mobilization, survival, and proliferation of endogenous myocardial stem cells in the injured heart, providing a novel mechanistic explanation for how apelin-13 might repair the heart and improve cardiac function. Thus, apelin-13 or pharmacological agonists of the APJ receptor could act as novel therapies for heart regeneration.

Abstract 1460: Bone marrow-derived CD11b+/Podoplanin+ cells are lymphatic progenitors directly responsible for breast cancer lymphatic formation

Abstract Introduction: Lymphatic metastasis, a key factor for poor outcome of breast cancer (BC), strongly depends on lymphatic vessel (LV) formation. Recent studies suggest that lymphangiogenesis is strongly promoted by bone marrow (BM)-derived CD11b+ monocytes that differentiate into Lymphatic Endothelial Cell Progenitors dubbed here M-LECP. While BC are known to recruit BM monocytes, a specific BM subset responsible for tumor lymphatic formation has not been identified. We recently discovered that podoplanin (Pdpn) is the highest upregulated lymphatic marker that signifies transdifferentiation of either human or mouse immature myeloid cells into M-LECP. We hypothesized that BM-derived M-LECP are represented by a subset expressing podoplanin in CD11b+ myeloid cells that are capable of inducing tumor lymphatics. Methods: Tumor lymphatic vessels expressing myeloid markers were detected immunohistochemically by triple-staining in clinical specimens and experimental breast tumors. Expression of Vegfr-3, Lyve-1, Sca-1, and other markers in BM-derived CD11b+/Pdpn+ and Pdpn-negative subsets was determined by FACS. Expression of lymphatic-specific markers in CD11b+/Pdpn+ and Pdpn− myeloid cells isolated from MDA-MB-231 tumors was determined by RT-qPCR. CD11b+/Pdpn+ and Pdpn-negative subsets from BM of GFP-expressing mice were adoptively transferred to mice with orthotopic breast tumors followed by quantifying mobilized GFP+/CD11b+/Pdpn+ cells and the density of tumor LV. Results: M-LECP were absent in normal human breast tissues but highly present in tumors. Analysis of clinical BC specimens showed significant correlations between tumor-mobilized M-LECP, density of LV and metastasis to regional nodes. All examined BC models exhibited very high densities (60-90%) of double-positive macrophages expressing lymphatic markers, and lymphatic vessels expressing myeloid proteins. At least a half of CD11b+ cells isolated from tumors were positive for podoplanin and nearly 90% of CD11b+/Pdpn+ subset expressed markers of progenitor cells. Only CD11b+/Pdpn+ subset (but not other myeloid cells) expressed a broad panel of proteins specific to the lymphatic endothelial lineage. Adoptive transfer of BM-derived CD11b+/Pdpn+ or Pdpn-negative fractions into tumor-bearing mice showed that only Pdpn+ BM myeloid cells integrated into preexisting LV and caused a 10-fold increase in peritumoral and intratumoral LV density. Conclusion: We show for the first time in clinical BC samples that tumor-recruited M-LECP significantly correlate with LN metastasis. We also identified a phenotypically distinct BM fraction of CD11b+/Pdpn+ cells that directly promote generation of new tumor lymphatic vessels. Our data suggest that tumors induce myeloid BM cells to undergo differentiation into M-LECP that subsequently promote cancer lymphatics thereby promoting tumor spread. Citation Format: Caitlin Griggs, Kelly Hall, Lisa Volk-Draper, Kathy Robinson, Sophia Ran. Bone marrow-derived CD11b+/Podoplanin+ cells are lymphatic progenitors directly responsible for breast cancer lymphatic formation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1460.

The Membrane-Bound Form of IL-17A Promotes the Growth and Tumorigenicity of Colon Cancer Cells.

Interleukin-17A is a member of the IL-17 family, and is known as CTLA8 in the mouse. It is produced by T lymphocytes and NK cells and has proinflammatory roles, inducing cytokine and chemokine production. However, its role in tumor biology remains controversial. We investigated the effects of locally produced IL-17A by transferring the gene encoding it into CT26 colon cancer cells, either in a secretory or a membrane-bound form. Expression of the membrane-bound form on CT26 cells dramatically enhanced their proliferation in vitro. The enhanced growth was shown to be due to an increased rate of cell cycle progression: after synchronizing cells by adding and withdrawing colcemid, the rate of cell cycle progression in the cells expressing the membrane-bound form of IL-17A was much faster than that of the control cells. Both secretory and membrane-bound IL-17A induced the expression of Sca-1 in the cancer cells. When tumor clones were grafted into syngeneic BALB/c mice, the tumor clones expressing the membrane-bound form IL-17A grew rapidly; those expressing the secretory form also grew faster than the wild type CT26 cells, but slower than the clones expressing the membrane-bound form. These results indicate that IL-17A promotes tumorigenicity by enhancing cell cycle progression. This finding should be considered in treating tumors and immune-related diseases.

Cardiac stem cell transplantation with 2,3,5,4′-tetrahydroxystilbehe-2-O-β-d-glucoside improves cardiac function in rat myocardial infarction model

Headings aimsCardiac stem cells (CSCs)-transplanted therapy provides a promising therapy for the ischemic heart disease (IHD), especially in the epidemic of myocardial infarction (MI). The compound 2,3,5,4′-tetrahydroxystilbene-2-O-β-d-glucoside (THSG) can induce CSC proliferation in vitro based on our previous study, so we aimed to study the induce effect of THSG on CSCs-transplanted MI rat in vivo. Materials and methodsUsing a murine model of MI, this study was designed to evaluate the impact of THSG (30, 60, 120mg/kg) on CSCs-based therapy for MI and the underlying mechanism in this process. Key findingThe results showed that THSG on CSCs-transplanted therapy groups (THSG+CSCs groups) can significantly reduce S-T segment elevation, and increase heart rate compared with MI group. The left ventricular ejection fraction (LVEF) and the left ventricular fractional shortening (LVFS) were significantly reduced in THSG+CSCs groups compared to the MI group. The levels of enzyme expression (CK-MB, LDH), the heart weight index (HWI) and myocardial infarct size (IS) were all reduced in THSG+CSCs groups. Moreover, other changes noted during these 28days post-MI, included pathologic changes, as well as increased stem cell antigen-1 (Sca-1) expression, or expression of Nkx2.5, GATA-4, and Connexin 43 in myocardial tissue, and reduced the Caspase-3 expression. SignificanceOur findings indicated that THSG facilitated CSCs-transplanted therapy in MI. These observations may be associated with the inducted of THSG on the proliferation of CSCs in vivo and also, with the subsequent differentiation of additional intrinsic neonatal cardiomyocytes to replace damaged heart tissue.

Mysm1 is required for interferon regulatory factor expression in maintaining HSC quiescence and thymocyte development.

Mysm1−/− mice have severely decreased cellularity in hematopoietic organs. We previously revealed that Mysm1 knockout impairs self-renewal and lineage reconstitution of HSCs by abolishing the recruitment of key transcriptional factors to the Gfi-1 locus, an intrinsic regulator of HSC function. The present study further defines a large LSKs in >8-week-old Mysm1−/− mice that exhibit increased proliferation and reduced cell lineage differentiation compared with those of WT LSKs. We found that IRF2 and IRF8, which are important for HSC homeostasis and commitment as transcription repressors, were expressed at lower levels in Mysm1−/− HSCs, and Mysm1 enhanced function of the IRF2 and IRF8 promoters, suggesting that Mysm1 governs the IRFs for HSC homeostasis. We further found that the lower expressions of IRF2 and IRF8 led to an enhanced transcription of p53 in Mysm1−/− HSCs, which was recently defined to have an important role in mediating Mysm1−/−-associated defects. The study also revealed that Mysm1−/− thymocytes exhibited lower IRF2 expression, but had higher Sca1 expression, which has a role in mediating thymocyte death. Furthermore, we found that the thymocytes from B16 melanoma-bearing mice, which display severe thymus atrophy at late tumor stages, exhibited reduced Mysm1 and IRF2 expression but enhanced Sca1 expression, suggesting that tumors may downregulate Mysm1 and IRF2 for thymic T-cell elimination.

Optimized Animal Model of Cyclophosphamide-induced Bone Marrow Suppression.

Myelosuppression is one of the serious side effects of anticancer chemotherapeutic drugs that deteriorate the bodily functions of patients, thereby affecting the quality of life considerably. Prevention of myelosuppression in anticancer chemotherapy is an important research topic. A stabilized chemotherapy-induced myelosuppression animal model is necessary in experimental research. This study aimed to establish an optimized animal model of chemotherapy-induced bone marrow suppression. After C57BL/6 mice were treated with intermediate- and high-dose (25/50 mg/kg) cyclophosphamide (CTX) for 10 days, the body-weight, changes in thymus and spleen, number of white blood cells (WBCs), red blood cells (RBCs), and platelets (PLTs) and changes in bone marrow in the mice were systematically evaluated at the next 2, 7 and 14 days. Our results demonstrated that CTX treatments could significantly decrease the body-weight of mice, as well as the ratios of the weights of thymus and spleen to body-weight. The physiological structures of thymus and spleen were destroyed by CTX treatments. The number of WBCs and RBCs significantly declined after CTX treatments; however, the number of PLTs increased. Moreover, the expression of Sca1 in bone marrow cells decreased on Day 2 but increased on Day 14. The expression of CD34 decreased in bone marrow cells after CTX treatments. In conclusion, mice models, with high-dose CTX treatments for 10 days, can be an optimized animal model for chemotherapy-induced bone marrow suppression.

GATA-related hematologic disorders.

The transcription factors GATA1 and GATA2 are fundamental regulators of hematopoiesis and have overlapping expression profiles. GATA2 is expressed in hematopoietic stem cells and early erythroid-megakaryocytic progenitors and activates a certain set of early-phase genes, including the GATA2 gene itself. GATA2 also initiates GATA1 gene expression. In contrast, GATA1 is expressed in relatively mature erythroid progenitors and facilitates the expression of genes associated with differentiation, including the GATA1 gene itself; however, GATA1 represses the expression of GATA2. Switching the GATA factors from GATA2 to GATA1 appears to be one of the key regulatory mechanisms underlying erythroid differentiation. Loss-of-function analyses using mice invivo have indicated that GATA2 and GATA1 are functionally nonredundant and that neither can compensate for the absence of the other. However, transgenic expression of GATA2 under the transcriptional regulation of the Gata1 gene rescues lethal dyserythropoiesis in GATA1-deficient mice, illustrating that the dynamic expression profiles of these GATA factors are critically important for the maintenance of hematopoietic homeostasis. Analysis of naturally occurring leukemias in GATA1-knockdown mice revealed that leukemic stem cells undergo functional alterations in response to exposure to chemotherapeutic agents. This mechanism may also underlie the aggravating features of relapsing leukemias. Recent hematologic analyses have suggested that disturbances in the balance of the GATA factors are associated with specific types of hematopoietic disorders. Here, we describe GATA1- and GATA2-related hematologic diseases, focusing on the regulation of GATA factor gene expression.

The contribution of the HSCs niche to bone marrow failure in the IL-2 deficient model

Abstract Bone marrow failure (BMF) is a devastating disease where regeneration of peripheral blood lineages is compromised, resulting in anemia and mortality. In IL-2 KO BALB/c mice, the balance between early myeloid and lymphoid progenitor cell populations is skewed resulting in insufficient myelopoiesis with accumulation of CD8 T cells in the BM. It is widely accepted that crosstalk between cells of the bone microenvironment and hematopoietic cells affects each other’s behavior. However, it remains unknown how the BM niche in this mouse model contribute to the BMF. Multipotent stromal cells (MSCs), osteoblasts (OBs) and endothelial cells (ECs) are the three types of BM stromal cells (BMSCs) that may serve as the distinct functional niche to maintain HSCs. Repots have shown the interplay between CD8 T cells and MSCs cause a change in myelopoiesis and that MSCs promote the formation of Tregs. Our data also indicates that IL-2 KO CD8 T cells are important for the expansion of CD4 T cells in the bone. Since IL-2 KO bones are extremely brittle and CD4 T cells produce RANKL, the ligand needed for osteoclast (OC) differentiation, we evaluated the frequency of BMSCs and OCs. Our preliminary data shows clear differences in BMSCs profiles of IL-2 KO mice, namely elevated stromal cell numbers and a shift in Sca-1 expression in ECs and CD51 expression in OBs. Additionally, OC precursor frequency is elevated in the BM, indicating an increase in bone resorption. The ability of the different subsets of the BMSCs to support the differentiation of HSCs in vitro and the role of CD8 T cells in promoting these changes in vivo is being currently evaluated. Overall, our preliminary data suggests that the change in the bone microenvironment may contribute to the BMF observed in these mice.

Abstract 61: Hedgehog-Responsive Stem Cell Antigen 1 Positive Cells Contribute To Vascular Smooth Muscle Cell Accumulation Following Vascular Injury

Background: Cardiovascular disease such as atherosclerosis is associated with the formation of an neointimal layer and medial hyperplasia as a result of the accumulation of vascular smooth muscle cells (vSMC) in the artery wall (i.e., intimal medial thickening, IMT). There is strong, albeit controversial, evidence indicating a putative role for stem cell antigen 1 positive (Sca1 + ) progenitor cell-derived vSMC in contributing to IMT. Interestingly, the Hedgehog (Hh) signaling receptor Patched 1 is present in the adventitial boundary and co-localizes with both Sca1 and Patched 1, the ligand for sonic hedgehog (SHh). The aim of our study was to determine the effect of Hh signaling on Sca1+ stem cells and their contribution to vSMC accumulation and IMT following vascular injury. Methods: Sca1 + stem cells were treated with differentiation inductive stimuli in the absence or presence of recombinant SHh (rSHh), with or without the Hh inhibitor cyclopamine, before the cells were examined for their stemness (telomerase activity), differentiation capacity (SMC differentiation) and epigenetic profile. In parallel, Sca1-eGFP transgenic mice were subjected to carotid injury (i.e., partial ligation), with or without cyclopamine, before IMT, Sca1 expression and SMC phenotype was assessed. Results: Sonic Hedgehog stimulated Sca1 + stem cell differentiation capacity, as demonstrated by enhanced expression of SMC differentiation markers in addition to their altered stemness, epigenetic profile (H3K4me2:H3K27me3) and proliferative status. In parallel studies, Hh signaling components were elevated in ligated carotids when compared to sham-operated controls, concomitant with increased Sca1 expression and SMC accumulation. Moreover, there was a significant attenuation of SMC accumulation and intimal medial thickening of injured carotids following Hh inhibition with cyclopamine. Conclusion: Sca1 + stem cells are Hh-responsive and they contribute to vSMC accumulation in the carotid following ligation injury.

Stem Cells Antigen-1 Enriches for a Cancer Stem Cell-Like Subpopulation in Mouse Gastric Cancer.

There is a strong need to identify markers to enrich gastric cancer stem cells (CSCs). However, CSC enrichment markers for mouse gastric cancers have not yet been determined. In our previous study, we generated primary mouse gastric cancer cell line NCC-S1 (S1) established from a Villin-cre;Smad4(F/F) ;Trp53(F/F) ;Cdh1(F/wt) mouse and its metastatic variant cell line NCC-S1M (S1M). Interestingly, S1M cells exhibited CSC-like features, such as increased tumorigenic potential and chemoresistance. By comparing gene expression profiles between S1 and S1M cells, we identified Stem Cells Antigen-1 (Sca-1) as a cell surface marker, which was mostly upregulated in S1M. Sca-1 was upregulated in tumorspheres from S1 cells or after cisplatin treatment in S1 cells. Immunofluorescence (IF) analysis showed that approximately 7% of cancer cells exhibited positivity for Sca-1 in primary mouse gastric cancer tissues. An in vivo-limiting dilution assay showed that Sca-1(high) mouse gastric cancer cells demonstrated increased tumorigenicity compared with Sca-1(negative) cells. The Sca-1 expression was downregulated by TGF-β pathway activation and Wnt pathway inhibition in mouse gastric cancer cells. Sca-1(high) cells showed relatively low TGF-β reporter activity and high TCF/LEF1 reporter activity compared with Sca-1(negative) cells. A chromatin immunoprecipitation analysis demonstrated that Sca-1 was a β-catenin/LEF1 target gene. Sca-1(high) allografts were more resistant to cisplatin/fluorouracil chemotherapy than Sca-1(negative) allografts, and overexpressed Bcl-xL. Eighty-five mouse genes overexpressed in Sca-1(high) S1 cells compared with Sca-1(negative) cells clustered 123 pretreatment gastric cancer patient samples according to survival following chemotherapy. Taken together, Sca-1 is a novel CSC enrichment marker that mediates TGF-β and Wnt/β-catenin signaling in mouse gastric cancer. Stem Cells 2016;34:1177-1187.

Expansion and Hepatic Differentiation of Adult Blood-Derived CD34+ Progenitor Cells and Promotion of Liver Regeneration After Acute Injury

The low availability of functional hepatocytes has been an unmet demand for basic scientific research, new drug development, and cell-based clinical applications for decades. Because of the inability to expand hepatocytes in vitro, alternative sources of hepatocytes are a focus of liver regenerative medicine. We report a new group of blood-derived CD34(+) progenitor cells (BDPCs) that have the ability to expand and differentiate into functional hepatocyte-like cells and promote liver regeneration. BDPCs were obtained from the peripheral blood of an adult mouse with expression of surface markers CD34, CD45, Sca-1, c-kit, and Thy1.1. BDPCs can proliferate in vitro and differentiate into hepatocyte-like cells expressing hepatocyte markers, including CK8, CK18, CK19, α-fetoprotein, integrin-β1, and A6. The differentiated BDPCs (dBDPCs) also display liver-specific functional activities, such as glycogen storage, urea production, and albumin secretion. dBDPCs have cytochrome P450 activity and express specific hepatic transcription factors, such as hepatic nuclear factor 1α. To demonstrate liver regenerative activity, dBDPCs were injected into mice with severe acute liver damage caused by a high-dose injection of carbon tetrachloride (CCl4). dBDPC treatment rescued the mice from severe acute liver injury, increased survival, and induced liver regeneration. Because of their ease of access and application through peripheral blood and their capability of rapid expansion and hepatic differentiation, BDPCs have great potential as a cell-based therapy for liver disease. Hematopoietic stem/progenitor cell expansion and tissue-specific differentiation in vitro are challenges in regenerative medicine, although stem cell therapy has raised hope for the treatment of liver diseases by overcoming the scarcity of hepatocytes. This study identified and characterized a group of blood-derived progenitor cells (BDPCs) from the peripheral blood of an adult mouse. The CD34(+) progenitor-dominant BDPCs were rapidly expanded and hepatically differentiated into functional hepatocyte-like cells with our established coculture system. BDPC treatment increased animal survival and produced full regeneration in a severe liver injury mouse model caused by CCl4. BDPCs could have potential for liver cell therapies.

Abstract B48: The effects of different types of hypoxia on tumor progression in breast cancer

Abstract Hypoxia, the state of low oxygen conditions, occurs frequently in solid tumors and is a poor prognostic factor. The expression of Hif-1α,the main mediator of the hypoxic response pathway, and the subsequent up-regulation of its target genes have been implicated in tumor growth, invasion, angiogenesis, therapy resistance and metastasis. There are two forms of hypoxia present in a growing tumor: chronic hypoxia (caused by limitations in oxygen diffusion from abnormal tumor vasculature) and intermittent hypoxia (caused by the aberrant, repeated and temporary closing and re-opening of blood vessels, leading to fluctuations in oxygen supply). This study investigates the phenotypes endowed by different forms of hypoxia that mediate metastatic potential in a syngeneic mouse model of breast cancer. By exposing murine breast cancer cells to 9 days of 20% O2 (normoxia), 1% O2 (chronic hypoxia) or alternating 24 hour cycles in 20% O2 and 1% O2 (intermittent hypoxia), we observe that intermittent hypoxia produces tumor cells with greater metastatic potential. These treatments produce no difference in primary tumor growth when orthotopically injected into the mammary fat pad of female C57Bl/6 mice. However, intermittent hypoxia-treated cells give rise to a greater number of and larger lung metastases when injected intravenously via the tail-vein of female C57Bl/6 mice. Intermittent hypoxia, but not chronic hypoxia, up-regulated the expression of genes that predict lung metastasis in breast cancer, endowed cells with an enhanced ability for anchorage-independent growth and produced greater clonal diversity. Furthermore, intermittent hypoxia also caused a switch to glycolysis in cells and induced a pro-tumorigenic, immunosuppressive secretory profile in vitro. Finally, intermittent hypoxia up-regulated the expression of mammary stem cell genes, increased expression of stem cell marker Sca-1 as well as CD14, and generated tumor-initiating cells at a higher frequency as evidenced by in vivo limiting dilution assays. This work demonstrates that intermittent hypoxia enhances metastatic seeding and outgrowth by priming cells intrinsically to metastasize, while activating co-operating factors that act extrinsically to form a permissive, immunosuppressive microenvironment. By delineating the contributions of different forms of hypoxia to metastasis, critical molecular mediators can be identified in aid of the development of efficacious therapies that could inhibit, prevent or cure metastatic disease. Citation Format: Anna Chen, Jaclyn Sceneay, Nathan Gödde, Erik Thompson, Patrick Humbert, Andreas Möller. The effects of different types of hypoxia on tumor progression in breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr B48.

Dasatinib promotes the activation of quiescent hematopoietic stem cells in mice.

Dasatinib is an orally available broad-spectrum tyrosine kinase inhibitor that is widely used to treat chronic myeloid leukemia. It is also in clinical trials for the treatment of other malignancies, including solid tumors. Despite its wide use, little is known of its effects on normal hematopoietic stem and progenitor cells. Here, we study wild-type mice dosed with dasatinib and find that it causes the transient induction of proliferation of quiescent hematopoietic stem cells (HSCs). This finding was unexpected given the ability of dasatinib to inhibit c-Kit signaling and promote cell cycle arrest in many cell types. The transient induction of HSC proliferation in dasatinib-dosed mice coincided with a marked induction in the expression of Sca-1 and phospho-S6. Also evident at this time was a rapid but transient loss of lineage-committed hematopoietic progenitors that express high levels of c-Kit and the induction of stem cell factor in the serum. These findings suggest that activation of quiescent HSCs is part of a rapid rescue response that restores hematopoietic progenitors to pretreatment levels. This restoration coincides with HSCs returning to quiescence, and the expression of Sca-1 and phospho-S6 reverting to pre-treatment levels, even though dasatinib dosing is maintained. These data suggest that equilibrium is reached between the opposing forces of dasatinib and hematopoietic growth factors. The transient induction of HSC proliferation provided a window of opportunity whereby these cells became sensitive to killing by the cytotoxic drug 5-fluorouracil.

Multiple Directional Differentiation Difference of Neonatal Rat Fibroblasts from Six Organs

Background/Aims: Fibroblasts are abundantly distributed throughout connective tissues in the body and are very important in maintaining the structural and functional integrity. Recent reports have proved that fibroblasts and mesenchymal stem cells share much more in common than previously recognized. The aim of this study was to investigate comparative studies in fibroblasts on the differences in the expression of molecular markers and differentiation capacity from different organs. Methods: Combined trypsin/collagenase enzymes digestion method was used to isolate and culture the fibroblasts derived from heart, liver, spleen, lung, kidney and skin. Cell activity was determined by methyl thiazolyl tetrazolium (MTT) assay. Common molecular markers for fibroblasts such as vimentin, DDR2 and FSP1, stem cell markers nanog, c-kit and sca-1 were detected by RT-PCR, immunofluorescence and western blotting. The osteogenic, adipogenic and cardiogenic differentiations of fibroblasts were performed by inductive culture in special mediums, and analyzed by Alizarin red, Oil red O and immunofluorescence staining of cTnT respectively. Results: The proliferation rate of fibroblasts in lung was faster than in other five organs. Common molecular markers for fibroblasts were expressed differently in different organs. DDR2 was strongly expressed in fibroblasts in the heart, partly expressed in the heart, skin, liver and spleen. Interestingly, no expression of DDR2 was detected in liver and kidney. However, vimentin and FSP1 were consistently expressed in fibroblasts from skin, liver, kidney, spleen and lung. nanog expression in fibroblasts from lung was less than that from heart, skin, liver and spleen (P < 0.01). c-kit expression in fibroblasts from heart, skin and kidney was higher than that from spleen (P < 0.05), while the c-kit positive fibroblasts from liver was obviously higher than that from spleen (P < 0.01). But sca-1 expression in fibroblasts from lung was the lowest among six organs (P < 0.01). Directed differentiation in vitro had demonstrated that skin fibroblasts had the strongest multiple differentiation potential, and the next was cardiac fibroblasts. And fibroblasts in liver and kidney had the advantage in myocardial differentiation, while fibroblasts in spleen only had the advantage in osteogenic differentiation. Conclusions: There are obvious heterogeneity in molecular markers and muti-directional differentiation in fibroblasts from six organs.

Abstract 13154: Modulation of Stem Cell Niche and Stem Cell Migration Promotes Functional Angiogenesis by Enhancing Stem Cell Homing in Ischemic Rat Myocardium: A Novel Concept of Cell-free Regeneration Therapy

Background: The microenvironments composed of extracellular matrix (ECM) components and cytokines are considered to be involved in the decision of the stem cell fate and behavior. In addition, some cytokines induced by ONO1301 has been reported to enhance cell migration contributing to myocardial regeneration. In this study, we hypothesized that combined administration of cardiac specific ECM such as laminins and ONO1301 may enhance regeneration process by modulation of stem cell activity and homing. Methods and Results: In vitro study revealed that MSCs showed strong adhesion to laminin (LM) 511. ONO1301 promoted the production of several cytokines in smooth muscle cells, and it enhanced MSCs migration in vitro assay. To examine the therapeutic effect of ONO1301 combined with LM511, we transplanted ONO1301 or ONO1301 with LM511 (n=5-12) in a rat acute myocardial infarction model. Four weeks later, the number of PDGFRα- and CD90-positive cells tended to be higher in the combination (ONO1301 with LM511) group than in the ONO1301 alone group. Furthermore the gene expression of Sca-1 and c-kit was higher in the combination group than the control group (Sca-1, ONO1301 with LM511: 2.16- (p&lt;0.05), ONO1301 alone: 2.01-fold to the control, c-kit, ONO1301 with LM511: 2.75- (p&lt;0.05), ONO1301 alone: 1.45-fold to the control). Histological examination revealed that the number of ILB4 (endothelial cell marker) positive cells was significantly higher in the combination group than in the ONO1301 group (ONO1301 with LM511: 521±68 cells/mm 2 , ONO1301 alone: 281±10 cells/mm 2 , control: 195±29 cells/mm 2 ; p&lt;0.05). Moreover, the number of CD31 (endothelial cell marker) and SMA (smooth muscle cell marker) double positive cell was significantly higher in the combination group compared with the control group (ONO1301 with LM511: 616±44 cells/mm 2 , control: 226±60 cells/mm 2 ; p&lt;0.05). Real time PCR analysis revealed that SDF-1, PGF, FGF2 and HGF were higher in the combination group. Moreover, infarct size tended to be smaller in the combination group than in the ONO1301 group. Conclusion: The cell free regeneration therapy using both ONO1301 and LM511 may contribute to enhanced stem cell homing to implanted site, leading to improve functional angiogenesis in rat ischemic heart.

Scaffold-free and scaffold-assisted 3D culture enhances differentiation of bone marrow stromal cells.

3D cultures of stem cells can preserve differentiation potential or increase the efficiency of methods that induce differentiation. Mouse bone marrow-derived stromal cells (BMSCs) were cultured in 3D as scaffold-free spheroids or "mesoid bodies" (MBs) and as aggregates on poly(lactic) acid microspheres (MB/MS). 3D cultures demonstrated viable cells, interaction on multiple planes, altered cell morphology, and the formation of structures similar to epithelial cell bridges. Cell proliferation was limited in suspension cultures of MB and MB/MS; however, cells regained proliferative capacity when transferred to flat substrates of tissue culture plates (TCPs). Expanded as monolayer, cells retained expression of Sca-1 and CD44 stem cell markers. 3D cultures demonstrated enhanced potential for adipogenic and osteogenic differentiation showing higher triglyceride accumulation and robust mineralization in comparison with TCP cultures. Enhanced and efficient adipogenesis was also observed in 3D cultures generated in a rotating cell culture system. Preservation of multilineage potential of BMSC was demonstrated in 5-azacytidine treatment of 3D cultures and TCP by expression of cardiac markers GATA4 and ACTA1 although functioning cardiomyocytes were not derived.