Inhibition Of Progenitor Cell Proliferation Research Articles

Rejuvenation of three germ layers tissues by exchanging old blood plasma with saline-albumin.

Heterochronic blood sharing rejuvenates old tissues, and most of the studies on how this works focus on young plasma, its fractions, and a few youthful systemic candidates. However, it was not formally established that young blood is necessary for this multi-tissue rejuvenation. Here, using our recently developed small animal blood exchange process, we replaced half of the plasma in mice with saline containing 5% albumin (terming it a “neutral” age blood exchange, NBE) thus diluting the plasma factors and replenishing the albumin that would be diminished if only saline was used. Our data demonstrate that a single NBE suffices to meet or exceed the rejuvenative effects of enhancing muscle repair, reducing liver adiposity and fibrosis, and increasing hippocampal neurogenesis in old mice, all the key outcomes seen after blood heterochronicity. Comparative proteomic analysis on serum from NBE, and from a similar human clinical procedure of therapeutic plasma exchange (TPE), revealed a molecular re-setting of the systemic signaling milieu, interestingly, elevating the levels of some proteins, which broadly coordinate tissue maintenance and repair and promote immune responses. Moreover, a single TPE yielded functional blood rejuvenation, abrogating the typical old serum inhibition of progenitor cell proliferation. Ectopically added albumin does not seem to be the sole determinant of such rejuvenation, and levels of albumin do not decrease with age nor are increased by NBE/TPE. A model of action (supported by a large body of published data) is that significant dilution of autoregulatory proteins that crosstalk to multiple signaling pathways (with their own feedback loops) would, through changes in gene expression, have long-lasting molecular and functional effects that are consistent with our observations. This work improves our understanding of the systemic paradigms of multi-tissue rejuvenation and suggest a novel and immediate use of the FDA approved TPE for improving the health and resilience of older people.

An Inhibitor of TGF-β Promotes Proliferation of Normal but Not MPN Hematopoietic Cells and Is a Candidate Therapeutic Agent for the Treatment of MPN Patients Carrying JAK2 V617F or Calr pQ365fs Mutations

The inhibitory effects exerted by transforming growth factor-β (TGF-β) on adult erythropoiesis has been well established. Canonical SMAD-depedent TGF-β signaling inhibits erythroid differentiation at multiple levels: it induces hematopoietic stem cells into quiescence (Chabanon et at Stem Cells. 2008;26:3150), it elicits a Smad5-dependent inhibition of progenitor cell proliferation (Bruno et al, Blood 1998; 91:1971) by increasing the length of G1 through reduction of G1 cyclin and cyclin-dependent protein kinases (Jacobsen et al, Blood 1995; 86:2957; Geng and Weinberg, PNAS 1993; 90:10315) and triggers Smad4-signaling accelerating terminal erythroid maturation (Zermati et al, Exp hematol 2000; 28:885; Choi et al MCB 2005;271:23). TGF-β is expressed by almost every cell type, but is produced in the greatest amount by megakaryocytes (Assonian et al, JBC 1983;258:7155; Massague, Cell 2008;134, 215).TGF-β has been implicated in the pathogenesis of primary myelofibrosis (PMF) by Schmitt et al (Blood. 2000;96:1342). Plasma, bone marrow and spleen washes of PMF patients, as well as those from murine PMF models, contain 2 fold-greater levels of total and bioactive TGF-β than those from normal controls (Zingariello et al, Blood 2013;121:3345). In addition, megakaryocytes from PMFpatients contain greater amounts of TGF-β than those from other MPNs such as polycythemia vera (PV) and essential thrombocythemia (Ciurea et al, Blood 2007;110:986). Published data, however, also suggest that malignant MPN cells are insensitive to TGF-β. Microarray analyses of PMF bone marrow and spleen cells revealed TGF-β signaling abnormalities which predict activation of non-canonical p38/ERK-dependent rather than canonical SMAD-dependent signaling (Ciaffoni et al, BCMD 2015;54:234). In addition, by phosphoproteomic profiling of PV erythroblasts (Erys) expanded in vitro express lower levels of pSmad2 as compared to Erys from healthy controls (Hricik et al. AJH 2013;88:723).The hypothesis that malignant MPN cells are insensitive to TGF-β was tested here by evaluating the effect of SB431542 [1,3,10 and 26µM], a small molecule inhibitor of TGF-β receptor 1, on ex vivo erythropoiesis in cultures generated by peripheral blood mononuclear cells from patients with JAK2 V617+-PV (n=2) and JAK2 V617F+ or CALR pQ365f+-PMF. Identical experiments were performed with Erys generated from adult peripheral blood (AB, n=3) and cord blood (CB, n=2) of healthy controls. All cultures were stimulated with SCF, IL-3 and EPO with and without dexamethasone (Dex).In cultures of JAK2 V617F+ -PV, SB431542 increased by 2-fold the numbers of progenitor cells observed by day 6, but had no effect on that of Erys observed by day 12-17 [fold increase (FI) ~4 fold in all cases]. Moreover, neither the number of progenitor cells nor that of Erys were affected by SB431542 treatment in cultures generated from JAK2 V617F+ (n=1) and CALR pQ365fs+ -PMF (n=1) patients (Fig. 1). This lack of effects was observed in cultures with and without Dex.By contrast, as expected, in cultures of AB, SB431542 significantly increased by 2.5-fold the number of progenitor cells observed by day 6 and that of Erys observed by day 14-17 (Fig. 1). This increase was associated with greater retention of an immature erythroid phenotype (CD36+ CD235a+ cells 16% vs 3%) and an increased proliferative index (>3 Erys in metaphases per field vs 0). This was observed up to day 17 in cultures both with and without Dex. The effects of SB431542 in cultures of CB were, however, affected by the presence of Dex. In cultures without Dex, SB431542 increased by 2-fold the number of progenitor cells by day 6 but had no effect on that of Erys by day 12-17 (FI=10-15 and CD36+CD235a+ cells >60%). In the presence of Dex, SB431542 did not affect the number of progenitor cells at day 6 but reduced that of Erys by 3-fold on day 12-17. These results suggest that in the case of CB, TGF-β promotes erythroid maturation in synergy with Dex.In conclusion, SB431542 promoted proliferation and maturation of normal adult progenitor cells but had no effect on PMF progenitor cells suggesting that treatments with TGF-β receptor 1 inhibitors may reactivate normal hematopoiesis in PMF patients by providing a proliferative advantage to the resident non-diseased hematopoietic stem cells over the malignant clone. This therapeutic approach will be explored in a MPD-RC, multi-center, phase II trial in patients with PMF. [Display omitted] DisclosuresHoffman:Geron: Consultancy, Membership on an entity's Board of Directors or advisory committees; All Cells, LLC: Consultancy, Membership on an entity's Board of Directors or advisory committees; Promedior: Research Funding. Mascarenhas:Roche: Research Funding; Incyte Corporation: Research Funding; Kalobios: Research Funding; CTI Biopharma: Research Funding; Novartis Pharmaceuticals Corporation: Research Funding; Promedior: Research Funding.

Role of TWEAK in coregulating liver progenitor cell and fibrogenic responses

Failure of fibrotic liver to regenerate after resection limits therapeutic options and increases demand for liver transplantation, representing a significant clinical problem. The mechanism underlying regenerative failure in fibrosis is poorly understood. Seventy percent partial hepatectomy (PHx) was performed in C57Bl/6 mice with or without carbon tetrachloride (CCl4)- induced liver fibrosis. Liver function and regeneration was monitored at 1 to 14 days thereafter by assessing liver mass, alanine aminotransferase (ALT), mRNA expression, and histology. Progenitor (oval) cell mitogen tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and TWEAK-neutralizing antibody were used to manipulate progenitor cell proliferation in vivo. In fibrotic liver, hepatocytes failed to replicate efficiently after PHx. Fibrotic livers showed late (day 5) peak of serum ALT (35426355 IU/L compared to 93665 IU/L in nonfibrotic livers), which coincided with progenitor cell expansion, increase in profibrogenic gene expression and de novo collagen deposition. In fibrotic mice, inhibition of progenitor activation using TWEAK-neutralizing antibody after PHx resulted in strongly down-regulated profibrogenic mRNA, reduced serum ALT levels and improved regeneration. Failure of hepatocyte-mediated regeneration in fibrotic liver triggers activation of the progenitor (oval) cell compartment and a severe fibrogenic response. Inhibition of progenitor cell proliferation using anti-TWEAK antibody prevents fibrogenic response and augments fibrotic liver regeneration. Targeting the fibrogenic progenitor response represents a promising strategy to improve hepatectomy outcomes in patients with liver fibrosis.

Failure of Fibrotic Liver Regeneration in Mice Is Linked to a Severe Fibrogenic Response Driven by Hepatic Progenitor Cell Activation

Failure of fibrotic liver to regenerate after resection limits therapeutic options and increases demand for liver transplantation, representing a significant clinical problem. The mechanism underlying regenerative failure in fibrosis is poorly understood. Seventy percent partial hepatectomy (PHx) was performed in C57Bl/6 mice with or without carbon tetrachloride (CCl4)-induced liver fibrosis. Liver function and regeneration was monitored at 1 to 14 days thereafter by assessing liver mass, alanine aminotransferase (ALT), mRNA expression, and histology. Progenitor (oval) cell mitogen tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and TWEAK-neutralizing antibody were used to manipulate progenitor cell proliferation in vivo. In fibrotic liver, hepatocytes failed to replicate efficiently after PHx. Fibrotic livers showed late (day 5) peak of serum ALT (3542 ± 355 IU/L compared to 93 ± 65 IU/L in nonfibrotic livers), which coincided with progenitor cell expansion, increase in profibrogenic gene expression and de novo collagen deposition. In fibrotic mice, inhibition of progenitor activation using TWEAK-neutralizing antibody after PHx resulted in strongly down-regulated profibrogenic mRNA, reduced serum ALT levels and improved regeneration. Failure of hepatocyte-mediated regeneration in fibrotic liver triggers activation of the progenitor (oval) cell compartment and a severe fibrogenic response. Inhibition of progenitor cell proliferation using anti-TWEAK antibody prevents fibrogenic response and augments fibrotic liver regeneration. Targeting the fibrogenic progenitor response represents a promising strategy to improve hepatectomy outcomes in patients with liver fibrosis.

Expansion of Hepatic Tumor Progenitor Cells in Pten-Null Mice Requires Liver Injury and Is Reversed by Loss of AKT2

The tumor suppressor PTEN inhibits AKT2 signaling; both are aberrantly expressed in liver tumors. We investigated how PTEN and AKT2 regulate liver carcinogenesis. Loss of PTEN leads to spontaneous development of liver tumors from progenitor cells. We investigated how the loss of PTEN activates liver progenitor cells and induces tumorigenesis. We studied mice with liver-specific disruptions in Pten and the combination of Pten and Akt2 to investigate mechanisms of liver carcinogenesis. PTEN loss leads to hepatic injury and establishes selective pressure for tumor-initiating cells (TICs), which proliferate to form mixed-lineage tumors. The Pten-null mice had increasing levels of hepatic injury before proliferation of hepatic progenitors. Attenuation of hepatic injury by deletion of Akt2 reduced progenitor cell proliferation and delayed tumor development. In Pten/Akt2-null mice given 3,5-diethoxycarbonyl-1,4 dihydrocollidine (DDC), we found that the primary effect of AKT2 loss was attenuation of hepatic injury and not inhibition of progenitor-cell proliferation in response to injury. Liver carcinogenesis in Pten-null mice requires not only the transformation of TICs but selection pressure from hepatic injury and cell death, which activates TICs. Further research is required to elucidate the mechanism for hepatic injury and its relationship with TIC activation.

Neuronal Ras activation inhibits adult hippocampal progenitor cell division and impairs spatial short‐term memory

A large number of endogenous and exogenous factors have been identified to upregulate and downregulate proliferation, differentiation and/or survival of newborn cells in the adult hippocampus. For studying neuronal mechanisms mediating the impact of those factors, we used a transgenic synRas mouse model expressing constitutively activated Valin12-Harvey Ras selectively in differentiated neurons. BrdU injections showed significantly reduced proliferation of new cells within the adult hippocampus of transgenic animals compared with their wild-type siblings. In contrast, the relative survival of newborn cells was increased in synRas mice, although this effect did not fully compensate for diminished proliferation. Inhibition of progenitor cell proliferation and enhancement of cellular survival were more pronounced in males compared with females. Double labelling and doublecortin immunostaining verified that specifically newborn neurons were decreased in synRas mice. Reduced cell generation was observed already 2 h after BrdU pulse injections, identifying an early precursor cell population as target of the inhibitory transgene effect. Differences in proliferation remained stable after 24 h and were specific for the subgranular zone of the dentate gyrus, as subventricular cell generation was not affected supporting a non-cell autonomous effect on neural hippocampal progenitors. Transgene expression only starts with synaptic differentiation and therefore reduced proliferation must represent an indirect secondary consequence of synRas activity in differentiated neurons. This was associated with impaired spatial short-term memory capacities as observed in a radial maze paradigm. Our data suggest that constantly high Ras activity in differentiated neurons downregulates hippocampal precursor cell generation in the neuronal lineage, but is modulated by sex-dependent factors.

Discovery of Novel Hippocampal Neurogenic Agents by Using an in Vivo Stable Isotope Labeling Technique

Neurogenesis occurs in discrete regions of adult mammalian brain, including the subgranular zone of the hippocampus. Hippocampal neurogenesis is enhanced by different classes of antidepressants, but screening for neurogenic actions of novel antidepressants has been inefficient because of limitations of 5-bromo-2'-deoxyuridine labeling techniques. We describe an efficient in vivo method for measuring hippocampal neurogenesis involving incorporation of the stable isotope, (2)H, into genomic DNA during labeling with (2)H(2)O (heavy water). Male rodents received 8 to 10% (2)H(2)O in drinking water; DNA was isolated from hippocampal progenitor cells or neurons. Label incorporation into progenitor cells of Swiss-Webster mice revealed subpopulation kinetics: 16% divided with t(1/2) of 2.7 weeks; the remainder did not divide over 1 year. Progenitor cell proliferation rates in mice were strain-dependent. Chronic antidepressant treatment for 3 weeks, with (2)H(2)O administered during the final week, increased progenitor cell proliferation across all the strains tested. Fluoxetine treatment increased (2)H incorporation into DNA of gradient-enriched neurons or flow-sorted neuronal nuclei 4 weeks after (2)H(2)O labeling, representing the survival and differentiation of newly divided cells into neurons. By screening 11 approved drugs for effects on progenitor cell proliferation, we detected previously unrecognized, dose-dependent enhancement of hippocampal progenitor cell proliferation by two statins and the anticonvulsant topiramate. We also confirmed stimulatory activity of other anticonvulsants and showed inhibition of progenitor cell proliferation by isotretinoin and prednisolone. In conclusion, stable isotope labeling is an efficient, high-throughput in vivo method for measuring hippocampal progenitor cell proliferation that can be used to screen for novel neurogenic drugs.

Inhibition of Progenitor Cell Proliferation in the Dentate Gyrus of Rats Following Post-Weaning Lead Exposure

Although lead is a potent developmental neurotoxin, the effects of postnatal lead exposure on progenitor cell proliferation in the hippocampus has not been examined. Postnatal day 25 rats were fed a lead containing diet (1500 ppm lead acetate) for 30–35 days and administered bromodeoxyuridine (BrdU, 50 mg/kg, i.p.) during the last 5 days of lead exposure. Animals were killed 24 h after the last BrdU injection. Proliferation of new cells in the subgranular zone and dentate gyrus was significantly decreased in lead-exposed rats compared to control animals that ate a similar diet devoid of lead. These results suggest that postnatal lead exposure can have significant deleterious effects on progenitor cell proliferation and thus the structure and function of the hippocampus.

Contact-mediated inhibition of human haematopoietic progenitor cell proliferation may be conferred by stem cell antigen, CD34.

The function of CD34, a transmembrane sialomucin expressed by human haematopoietic progenitor cells, is poorly understood. Its structure suggests it may act as a cell adhesion and signalling molecule. KGIa cells and primary CD34-positive marrow cells were tested for their ability to aggregate in the presence of the anti-CD34 antibody QBEND10; CFU-GM colonies were grown using standard methods and tested for their content of colony-forming cells by replating; 'haematons' were isolated from marrow by filtration; the phosphorylation of CD34 was investigated by immunoprecipitation and Western blotting CD34-positive cells in human bone marrow, like KG1a cells, aggregate when incubated with QBEND10. Staining aggregates with anti-CD34-FITC revealed that aggregation involved co-localisation of CD34 at intercellular binding sites. We examined myeloid colonies (CFU-GM) grown from normal human bone marrow cells, and multicellular aggregates ('haematons') separated from freshly aspirated marrow by filtration, and found CD34-positive cells bound together with co-localisation of the CD34 at the binding sites. This finding shows that CD34-positive cell-cell adhesion occurs physiologically in vitro and in vivo. QBEND10-induced aggregation of KG1a and CD34-positive cells was enhanced by staurosporine (a protein kinase C inhibitor) and inhibited by genistein (a protein tyrosine kinase inhibitor). Moreover, aggregated cells had increased phosphorylation of tyrosine on CD34 and translocation of protein kinase C (PKC) to the cytoplasm, compared with non-aggregated cells. We used the ability of primary colonies to produce secondary colonies on replating as a functional parameter and found that the replating ability of the colonies was increased by treatment with genistein (P=0.003). In addition, the ability of individual samples of primary CD34-positive cells to undergo QBEND10-induced aggregation and the ability of CD34-positive cell-derived colonies to produce secondary clones on replating were inversely related (r=0.86). Our results suggest that homotypic aggregation of haematopoietic progenitor cells may be an important mechanism for preventing inappropriate proliferation in vivo. Thus, regulation of expression of the CD34 molecule may play an important role in maintaining the normal level of haematopoietic activity by contact-mediated inhibition of progenitor cell proliferation.

Tumor Necrosis Factor (TNF) Is a Physiologic Regulator of Hematopoietic Progenitor Cells: Increase of Early Hematopoietic Progenitor Cells in TNF Receptor p55-Deficient Mice In Vivo and Potent Inhibition of Progenitor Cell Proliferation by TNFα In Vitro

Murine bone marrow cells with lineage phenotypes (Lin)-Sca-1+c-kit+ and Lin-Sca-1-c-kit+ cells represent primitive hematopoietic stem cells (HSCs) and committed hematopoietic progenitor cells, respectively. The number of Lin-Sca-1+c-kit+ HSCs in bone marrow was significantly increased in tumor necrosis factor (TNF) receptor p55-deficient (TNF-R55-1-) mice compared with the TNF-R55+/+ wild-type mice without a marked change in bone marrow cellularity. In both the methylcellulose culture and a single-cell proliferation assay, mouse TNF alpha (mTNF alpha) inhibited in vitro the proliferation of wild-type mouse-derived Lin-Sca-1+c-kit+ cells in response to a combination of multiple growth factors. The same is true for that of Lin-Sca-1+c-kit+ cells stimulated with granulocyte colony-stimulating factor (G-CSF) plus stem cell factor (SCF). Moreover, mTNF alpha significantly arrested the entry into S-phase from G0/G1 phase of Lin-Sca-1+c-kit+ cells stimulated with multiple growth factors and Lin-Sca-1-c-kit+ cells stimulated with G-CSF plus SCF. In contrast, mTNF alpha failed to affect the growth and cell cycle progression of Lin-Sca-1+c-kit+ cells and Lin-Sca-1-c-kit+ cells that were obtained from TNF-R55-deficient mice. These data suggest that TNF may be an important physiologic regulator of hematopoiesis and that TNF-R55 may be essentially involved in TNF-mediated inhibition of the growth of both primitive stem and more committed progenitor cells.

Tumor necrosis factor (TNF) is a physiologic regulator of hematopoietic progenitor cells: increase of early hematopoietic progenitor cells in TNF receptor p55-deficient mice in vivo and potent inhibition of progenitor cell proliferation by TNF alpha in vitro

Murine bone marrow cells with lineage phenotypes (Lin)-Sca-1+c-kit+ and Lin-Sca-1-c-kit+ cells represent primitive hematopoietic stem cells (HSCs) and committed hematopoietic progenitor cells, respectively. The number of Lin-Sca-1+c-kit+ HSCs in bone marrow was significantly increased in tumor necrosis factor (TNF) receptor p55-deficient (TNF-R55–1-) mice compared with the TNF-R55+/+ wild-type mice without a marked change in bone marrow cellularity. In both the methylcellulose culture and a single-cell proliferation assay, mouse TNF alpha (mTNF alpha) inhibited in vitro the proliferation of wild-type mouse-derived Lin-Sca-1+c-kit+ cells in response to a combination of multiple growth factors. The same is true for that of Lin-Sca-1+c-kit+ cells stimulated with granulocyte colony-stimulating factor (G-CSF) plus stem cell factor (SCF). Moreover, mTNF alpha significantly arrested the entry into S-phase from G0/G1 phase of Lin-Sca-1+c-kit+ cells stimulated with multiple growth factors and Lin-Sca-1-c-kit+ cells stimulated with G-CSF plus SCF. In contrast, mTNF alpha failed to affect the growth and cell cycle progression of Lin-Sca-1+c-kit+ cells and Lin-Sca-1-c-kit+ cells that were obtained from TNF-R55-deficient mice. These data suggest that TNF may be an important physiologic regulator of hematopoiesis and that TNF-R55 may be essentially involved in TNF-mediated inhibition of the growth of both primitive stem and more committed progenitor cells.

Interleukin-2 inhibition of oligodendrocyte progenitor cell proliferation depends on expression of the TAC receptor.

Interleukin-2 (IL-2) has been shown to inhibit oligodendrocyte progenitor cell proliferation. Within the immune system, IL-2 biological action is dependent strictly on the expression of the IL-2 receptor. The antibody TAC, which specifically binds the lymphocyte IL-2 receptor, has been shown to also bind oligodendrocyte progenitor cells cultured in a serumless, chemically defined medium. The expression of the TAC antigen was found necessary for IL-2 inhibition of oligodendrocyte progenitor cell proliferation. After IL-2 induced down-regulation of the TAC antigen, the progenitor cell was unresponsive to IL-2, even 72 hr after IL-2 withdrawal. During this unresponsive period, the oligodendrocyte progenitor cell was immunocytochemically negative for the TAC antigen. Thus, in contrast to IL-2 receptors on T-cells, IL-2 does not up-regulate its receptor on oligodendrocyte progenitor cells. However, upon interleukin 1 (IL-1) addition both IL-2 responsiveness and TAC immunocytochemical staining reappeared. These data suggest that IL-2 inhibition of progenitor cell proliferation depends on the expression of the TAC antigen, which can be regulated by IL-1.

HLA-DR monoclonal antibodies inhibit the proliferation of normal and chronic granulocytic leukaemia myeloid progenitor cells.

We studied the capacity of murine monoclonal antibodies with HLA-DR specificity to inhibit the proliferation in vitro of erythroid (BFU-E and CFU-E) and granulocyte-macrophage (CFU-GM) progenitor cells in normal bone marrow and the blood of patients with chronic granulocytic leukaemia (CGL). Two IgG2 antibodies (CA 2.06 and L243) inhibited the proliferation of normal BFU-E and CFU-GM at relatively high dilution; a third antibody, DA2, had no effect on either progenitor cell. A complement-fixing monoclonal antibody with T-cell activity (OKT3) produced only minor reduction in progenitor cel proliferation. Further studies with L243 showed that BFU-E and CFU-GM from the blood of patients with CGL were inhibited to the same degree as normal marrow progenitor cells. The inhibition of progenitor cell proliferation by a given antibody was always complement dependent and was therefore presumed to be due to a direct cytotoxic effect. The inhibitory effect of monoclonal antibodies is a valuable approach to the characterization of antigenic determinants on myeloid progenitor cells and the differential cytotoxicity of selected monoclonal antibodies might be exploitable for therapy.