Rapamycin inhibits proliferation and differentiation of human endothelial progenitor cells in vitro

Bone-marrow-derived, circulating endothelial precursor cells contribute to neoangiogenesis in various diseases. Rapamycin has recently been shown to have anti-angiogenic effects in an experimental tumor model. Our group has developed a culture system that allows expansion and endothelial differentiation of human CD133(+) precursor cells. We could show by PCR analysis that mTOR, the rapamycin-binding protein, was expressed in fresh CD133(+) cells, in expanded cells after 28 days, and in differentiated endothelial cells. Rapamycin inhibited proliferation of CD133(+) cells dose dependently at similar concentrations as hematopoietic Jurkat or HL-60 cells. Apoptosis was induced by rapamycin after 48 h of treatment, which could be reduced by preincubation with FK 506. Furthermore, the development of adherent endothelial cells from expanded CD133(+) cells was dose dependently inhibited. Expression of endothelial antigens CD144 and von Willebrand factor on differentiating endothelial precursors was reduced by rapamycin. In summary, rapamycin inhibits proliferation and differentiation of human endothelial precursor cells underlining its anti-angiogenic effects.     

Betacellulin regulates the proliferation and differentiation of retinal progenitor cells in vitro

Retinal progenitor cells (RPCs) hold great potential for the treatment of retinal degenerative diseases. However, their proliferation capacity and differentiation potential towards specific retinal neurons are limited, which limit their future clinical applications. Thus, it is important to improve the RPCs’ ability to proliferate and differentiate. Currently, epidermal growth factor (EGF) is commonly used to stimulate RPC growth in vitro. In this study, we find that betacellulin (BTC), a member of the EGF family, plays important roles in the proliferation and differentiation of RPCs. Our results showed that BTC can significantly promote the proliferation of RPCs more efficiently than EGF. EGF stimulated RPC proliferation through the EGFR/ErbB2‐Erk pathway, while BTC stimulated RPC proliferation more powerfully through the EGFR/ErbB2/ErbB4‐Akt/Erk pathway. Meanwhile, under differentiated conditions, the BTC‐pre‐treated RPCs were preferentially differentiated into retinal neurons, including photoreceptors, one of the most important types of cells for retinal cell replacement therapy, compared to the EGF‐pre‐treated RPCs. In addition, knockdown of endogenous BTC expression can also obviously promote RPC differentiation into retinal neuronal cells. This data demonstrate that BTC plays important roles in promoting RPC proliferation and differentiation into retinal neurons. This study may provide new insights into the study of RPC proliferation and differentiation and make a step towards the application of RPCs in the treatment of retinal degenerative diseases.     

Cooperation between PDGF and FGF converts slowly dividing O-2Aadult progenitor cells to rapidly dividing cells with characteristics of O- 2Aperinatal progenitor cells

We have shown previously that oligodendrocyte-type-2 astrocyte (O-2A) progenitor cells isolated from adult rat optic nerves can be distinguished in vitro from their perinatal counterparts on the basis of their much slower rates of division, differentiation, and migration when grown in the presence of cortical astrocytes or PDGF. This behavior is consistent with in vivo observations that there is only a modest production of oligodendrocytes in the adult CNS. As such a behavior is inconsistent with the likely need for a rapid generation of oligodendrocytes following demyelinating damage to the mature CNS, we have been concerned with identifying in vitro conditions that allow O-2Aadult progenitor cells to generate rapidly large numbers of progeny cells. We now provide evidence that many slowly dividing O-2Aadult progenitor cells can be converted to rapidly dividing cells by exposing adult optic nerve cultures to both PDGF and bFGF. In addition, these O-2Aadult progenitor cells appear to acquire other properties of O-2Aperinatal progenitor cells, such as bipolar morphology and high rate of migration. Although many O-2Aadult progenitor cells in cultures exposed to bFGF alone also divide rapidly, these cells are multipolar and migrate little in vitro. Oligodendrocytic differentiation of O-2Aadult progenitor cells, which express receptors for bFGF in vitro, is almost completely inhibited in cultures exposed to bFGF or bFGF plus PDGF. As bFGF and PDGF appear to be upregulated and/or released after injury to the adult brain, this particular in vitro response of O-2Aadult progenitor cells to PDGF and bFGF may be of importance in the generation of large numbers of new oligodendrocytes in vivo following demyelination.     

In vitro analysis of the origin and maintenance of O-2Aadult progenitor cells

We have been studying the differing characteristics of oligodendrocyte- type-2 astrocyte (O-2A) progenitors isolated from optic nerves of perinatal and adult rats. These two cell types display striking differences in their in vitro phenotypes. In addition, the O- 2Aperinatal progenitor population appears to have a limited life-span in vivo, while O-2Aadult progenitors appear to be maintained throughout life. O-2Aperinatal progenitors seem to have largely disappeared from the optic nerve by 1 mo after birth, and are not detectable in cultures derived from optic nerves of adult rats. In contrast, O-2Aadult progenitors can first be isolated from optic nerves of 7-d-old rats and are still present in optic nerves of 1-yr-old rats. These observations raise two questions: (a) From what source do O-2Aadult progenitors originate; and (b) how is the O-2Aadult progenitor population maintained in the nerve throughout life? We now provide in vitro evidence indicating that O-2Aadult progenitors are derived directly from a subpopulation of O-2Aperinatal progenitors. We also provide evidence indicating that O-2Aadult progenitors are capable of prolonged self renewal in vitro. In addition, our data suggests that the in vitro generation of oligodendrocytes from O-2Aadult progenitors occurs primarily through asymmetric division and differentiation, in contrast with the self-extinguishing pattern of symmetric division and differentiation displayed by O-2Aperinatal progenitors in vitro. We suggest that O-2Aadult progenitors express at least some properties of stem cells and thus may be able to support the generation of both differentiated progeny cells as well as their own continued replenishment throughout adult life.     

Glycine regulates proliferation and differentiation of salivary-gland-derived progenitor cells

Amino acids have various physiological activities that influence processes such as intestinal regeneration, EGF secretion, protein synthesis, and cell growth. Salivary glands are exposed to nutrients that influence their proliferation and regeneration. Glycine is included in saliva in large quantities and reportedly has important roles in antibacterial activities and the inhibition of tumor growth and as a precursor of nucleotide synthesis in cell proliferation. We have investigated the effects of glycine on the proliferation and differentiation of salivary glands by using mouse salivary-gland-derived progenitor (mSGP) cells. In cultures of mSGP cells, cell proliferation is suppressed in the presence of glycine, whereas it is promoted by its removal. Glycine promotes three-dimensional formations of mSGP cells, which are negative for immature markers and positive for differentiation markers. In cell-cycle analysis, cell-cycle progression is delayed at the S-phase by glycine supplementation. Glycine also suppresses the phosphorylation of p42/p44MAPK. These results suggest that glycine suppresses the proliferation and promotes the differentiation of mSGP cells, and that it has inhibitory effects on growth factor signaling and cell-cycle progression. Glycine might therefore be a physiological activator that regulates the proliferation and differentiation of salivary glands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. This work was supported in part by the Advanced Education Program for Integrated Clinical, Basic and Social Medicine, Graduate School of Medical Sciences, Kumamoto University (Support Program for Improving Graduate School Education, MEXT,　Japan).     

Direct effects of IL-4 on the in vitro differentiation and proliferation of hematopoietic progenitor cells

The purpose of this study was to analyze the effects of recombinant human interleukin 4 (IL-4) on the differentiation and proliferation in vitro of human granulocyte/macrophage (GM) and erythroid progenitors. IL-4 was added to either fetal bovine serum (FBS)-supplemented or to FBS-deprived cultures of unfractionated human marrow cells or marrow cells depleted of adherent and/or T cells. Paradoxical effects similar to those reported in the murine system were detected in these experiments. In FBS-supplemented cultures, IL-4, which had no effect on the growth or erythroid bursts (from burst-forming cells; BFU-E) detected in the presence of Epo alone, decreased by 46% the number of erythroid bursts detected in the presence of Epo and phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM). In contrast, in FBS-deprived cultures, IL-4 increased by 30-700% the number of erythroid bursts in cultures containing Epo alone or containing Epo, IL-3, and GM-CSF. The stimulatory effect of IL-4 on erythroid burst growth under FBS-deprived conditions was particularly evident when adherent cells were removed. Under the conditions investigated, IL-4 had little effect on the growth of GM colonies. In FBS-deprived suspension cultures of nonadherent, T-cell-depleted marrow cells, IL-4 maintained both the number of BFU-E and CFU-GM for at least 8 days. In these cultures, IL-4 antagonized the capacity of IL-3 to increase the number of BFU-E but IL-4 and IL-3 acted together to maintain the number of CFU-GM. To determine if IL-4 acted directly or indirectly, its effects on the growth of factor-dependent subclones of the murine progenitor cell line 32D were analyzed. Three subclones were studied: the original IL-3-dependent clone 32D cl.3, the Epo-dependent erythroid clone 32D Epo-1, and the G-CSF-dependent myeloid clone 32D G-1. IL-4 alone failed to induce colony growth from these cell lines. However, IL-4 inhibited by 25% the number of colonies formed by 32D cl.3 in the presence of IL-3 while increasing by 25% and 25-50% the number of colonies formed by 32D Epo-1 and 32D G-1 in the presence of Epo or G-CSF, respectively. These results indicate that human IL-4, as its murine counterpart, is a multilineage growth factor with paradoxical effects which are mediated by the direct action of IL-4 on progenitor cells.     

A key role for Pak4 in proliferation and differentiation of neural progenitor cells

The Pak4 serine/threonine kinase regulates cytoskeletal organization, and controls cell growth, proliferation, and survival. Deletion of Pak4 in mice results in embryonic lethality prior to embryonic day 11.5. Pak4 knockout embryos exhibit abnormalities in the nervous system, the heart, and other tissues. In this study a conditional deletion of Pak4 was generated in order to study the function of Pak4 in the development of the brain. Nervous system-specific conditional deletion of Pak4 was accomplished by crossing mice with a floxed allele of Pak4 with transgenic mice expressing Cre recombinase under the control of the nestin promoter. The conditional Pak4 knockout mice were born normally, but displayed growth retardation and died prematurely. The brains showed a dramatic decrease in proliferation of cortical and striatal neuronal progenitor cells. In vitro analyses revealed a reduced proliferation and self-renewing capacity of neural progenitor cells isolated from Pak4 knockout brains. The mice also exhibited cortical thinning, impaired neurogenesis and loss of neuroepithelial adherens junctions. By the time the mice died, by 4 weeks after birth, severe hydrocephalus could also be seen. These results suggest that Pak4 plays a critical role in the regulation of neural progenitor cell proliferation and in establishing the foundation for development of the adult brain.     

Hypoxia affects in vitro proliferation and differentiation of mouse corneal epithelial progenitor cell

This study was to investigate the proliferation and differentiation of mouse corneal epithelial progenitor cell in hypoxic airlift culture. Mouse corneal epithelial progenitor cell line progenitor cells were cultured under airlift with normoxic and hypoxic conditions for various durations up to 2 wk. Under normoxic conditions when exposed to air, the hyperproliferation and abnormal epidermal-like differentiation of mouse corneal epithelium was induced, whereas when exposed to air under hypoxic conditions, although we observed augmented proliferation, the abnormal differentiation was inhibited. The mechanism by which hypoxia prevents abnormal differentiation may involve downregulation of Wnt signaling pathways, which were inhibited in cells cultured with hypoxic airlift technique. In conclusion, hypoxia can prevent abnormal differentiation while enhancing the proliferation of corneal epithelial cells by blocking Wnt/β-catenin signaling pathway.     

DISP3 promotes proliferation and delays differentiation of neural progenitor cells

DISP3 (PTCHD2), a sterol-sensing domain-containing protein, is highly expressed in neural tissue but its role in neural differentiation is unknown. In the present study we used a multipotent cerebellar progenitor cell line, C17.2, to investigate the impact of DISP3 on the proliferation and differentiation of neural precursors. We found that ectopically expressed DISP3 promotes cell proliferation and alters expression of genes that are involved in tumorigenesis. Finally, the differentiation profile of DISP3-expressing cells was altered, as evidenced by delayed expression of neural specific markers and a reduced capacity to undergo neural differentiation.     

PDGF A chain homodimers drive proliferation of bipotential (O-2A) glial progenitor cells in the developing rat optic nerve.

The bipotential glial progenitor cells (O-2A progenitors), which during development of the rat optic nerve give rise to oligodendrocytes and type 2 astrocytes, are stimulated to divide in culture by platelet-derived growth factor (PDGF), and there is evidence that PDGF is important for development of the O-2A cell lineage in vivo. We have visualized PDGF mRNA in the rat optic nerve by in situ hybridization, and its spatial distribution is compatible with the idea that type 1 astrocytes are the major source of PDGF in the nerve. We can detect mRNA encoding the A chain, but not the B chain of PDGF in the brain and optic nerve, suggesting that the major form of PDGF in the central nervous system is a homodimer of A chains (PDGF-AA). PDGF-AA is a more potent mitogen for O-2A progenitor cells than is PDGF-BB, while the reverse is true for human or rat fibroblasts. Fibroblasts display two types of PDGF receptors, type A receptors which bind to all three dimeric isoforms of PDGF, and type B receptors which bind PDGF-BB and PDGF-AB, but have low affinity for PDGF-AA. Our results suggest that O-2A progenitor cells possess predominantly type A receptors, and proliferate during development in response to PDGF-AA secreted by type 1 astrocytes.     

Stimulation of differentiation and proliferation of haemopoietic cells in vitro

A liquid culture system, for haemopoietic cells, has been developed using bone marrow cells alone, or co-cultures of thymus and bone marrow cells, inoculated into four ounce medical bottles. After several days growth, such cultures consisted of an attaching population of cells, forming discrete colonies, and a non-attaching population. In the (co-cultures) there was a 2 X enhancement of monolayer colony development compared with the combined total present in the (marrow alone) plus (thymus alone) cultures. Also, better maintenance of non-attaching cells was seen in the (co-cultures). Normal CFUS and CFUC were present in both the (marrow alone) and the (co-cultures) for at least 14 days. In the (marrow alone) cultures, granulocytes in all stages of development were present for the first week, but by 12 days the culture consisted mainly of mono-nuclear cells. In the (co-cultures), however, at 12 days more than 60% of the cells were granulocytes, in all stages of differentiation. (Co-cultures) established using lethally irradiated thymus cells were not able to support this prolonged myeloid differentiation. By feeding the (co-cultures) it was possible to maintain production of (granulocytic) cells for at least ten weeks, although no fully mature granulocytes were observed. After the second feeding, no CFU_S were detectable, but variable numbers of agar colony forming cells (not classical CFU_C) were present at least for ten weeks.     

Hedgehog signal activation coordinates proliferation and differentiation of fetal liver progenitor cells

Hedgehog (Hh) signaling plays crucial roles in development and homeostasis of various organs. In the adult liver, it regulates proliferation and/or viability of several types of cells, particularly under injured conditions, and is also implicated in stem/progenitor cell maintenance. However, the role of this signaling pathway during the normal developmental process of the liver remains elusive. Although Sonic hedgehog (Shh) is expressed in the ventral foregut endoderm from which the liver derives, the expression disappears at the onset of the liver bud formation, and its possible recurrence at the later stages has not been investigated. Here we analyzed the activation and functional relevance of Hh signaling during the mouse fetal liver development. At E11.5, Shh and an activation marker gene for Hh signaling, Gli1, were expressed in Dlk⁺ hepatoblasts, the fetal liver progenitor cells, and the expression was rapidly decreased thereafter as the development proceeded. In the culture of Dlk⁺ hepatoblasts isolated from the E11.5 liver, activation of Hh signaling stimulated their proliferation and this effect was cancelled by a chemical Hh signaling inhibitor, cyclopamine. In contrast, hepatocyte differentiation of Dlk⁺ hepatoblasts in vitro as manifested by the marker gene expression and acquisition of ammonia clearance activity was significantly inhibited by forced activation of Hh signaling. Taken together, these results demonstrate the temporally restricted manner of Hh signal activation and its role in promoting the hepatoblast proliferation, and further suggest that the pathway needs to be shut off for the subsequent hepatic differentiation of hepatoblasts to proceed normally.     

The regulation of proliferation and differentiation in oligodendrocyte progenitor cells by alphaV integrins

We have previously shown that oligodendrocyte progenitor cells exhibit developmental switching between alphav-associated beta integrin subunits to sequentially express alphavbeta1, alphavbeta3 and alphavbeta5 integrins during differentiation in vitro. To understand the role that alphavveta3 integrin may play in regulating oligodendrocyte progenitor cell behaviour, cells of the rat cell line, CG-4, were genetically engineered to constitutively express alphavbeta3 integrin by transfection with full-length human beta3 integrin subunit cDNA. Time-lapse videomicroscopy showed no effect of beta3 expression on cell migration but revealed enhanced proliferation on vitronectin substrata. Comparison of mitotic indices, as measured by 5-bromo-2'-deoxyuridine incorporation, confirmed that human beta3 integrin-expressing cells exhibited enhanced proliferation, as compared to both vector-only transfected, and wild-type CG-4 cells when switched to differentiation medium from growth medium, but only in cultures grown on vitronectin and not on poly-D-lysine. The effects on proliferation were inhibited by a function-blocking antibody specifically directed against the human beta3 integrin subunit. Human beta3 integrin-expressing cells also exhibited reduced differentiation. This differentiation could be reduced still further by a function-blocking monoclonal antibody against alphavbeta5 integrin, as could differentiation in the wild-type CG-4 cells. Taken together, these results suggest that alphavbeta3 integrin may regulate oligodendroglial cell proliferation and that both downregulation of alphavbeta3 integrin expression and signalling through alphavbeta5 integrin may be critical to continued differentiation in vitro.     

Protein kinases associated with proliferation and differentiation in murine erythroleukaemic cells.

1. The changes in electrophoretic distribution of cytosolic protein kinases have been studied in relation to proliferation, differentiation and transformation in murine erythroleukaemic cells, using a non-denaturing polyacrylamide gel electrophoresis system. 2. Native molecular masses of the major forms were determined by Ferguson plots. 3. A two dimensional electrophoresis method was developed for determination of the subunit molecular masses. 4. These studies suggest that the major bands of activity contain components which may correspond to cGMP dependent protein kinase, cAMP dependent protein kinase and protein kinase C. 5. On hexamethylene bisacetamide induced differentiation of the cells, changes in proportions of the different forms were observed.     

CIP2A promotes proliferation of spermatogonial progenitor cells and spermatogenesis in mice

Protein phosphatase 2A (PP2A) is a critical regulator of protein serine/threonine phosphorylation. However, the physiological and developmental roles of different PP2A complexes are very poorly understood. Here, we show that a newly characterized PP2A inhibitory protein CIP2A is co-expressed with ki-67 and with self-renewal protein PLZF in the spermatogonial progenitor cell (SPC) population in the testis. CIP2A and PLZF expression was shown also to correlate Ki-67 expression in human testicular spermatogonia. Functionally, CIP2A mutant mouse testes exhibited smaller number of PLZF-positive SPCs and reduced sperm counts. Moreover, seminiferous tubuli cells isolated from CIP2A mutant mice showed reduced expression of Plzf and other renewal genes Oct-4 and Nanog at mRNA level. However, PLZF-deficient testes did not show altered CIP2A expression. Importantly, spermatogonia-specific restoration of CIP2A expression rescued PLZF expression and sperm production defects observed in CIP2A mutant mice. Taken together, these results reveal first physiological function for an emerging human oncoprotein CIP2A, and provide insights into maintenance of PLZF-positive progenitors. Moreover, demonstration that CIP2A expression can be systematically inhibited without severe consequences to normal mouse development and viability may have clinical relevance regarding targeting of oncogenic CIP2A for future cancer therapies.     

Genome-wide gene amplification during differentiation of neural progenitor cells in vitro

DNA sequence amplification is a phenomenon that occurs predictably at defined stages during normal development in some organisms. Developmental gene amplification was first described in amphibians during gametogenesis and has not yet been described in humans. To date gene amplification in humans is a hallmark of many tumors. We used array-CGH (comparative genomic hybridization) and FISH (fluorescence in situ hybridization) to discover gene amplifications during in vitro differentiation of human neural progenitor cells. Here we report a complex gene amplification pattern two and five days after induction of differentiation of human neural progenitor cells. We identified several amplified genes in neural progenitor cells that are known to be amplified in malignant tumors. There is also a striking overlap of amplified chromosomal regions between differentiating neural progenitor cells and malignant tumor cells derived from astrocytes. Gene amplifications in normal human cells as physiological process has not been reported yet and may bear resemblance to developmental gene amplifications in amphibians and insects.