Complete replacement of serum in primary cultures of erythropoietin-dependent red cell precursors (CFU-E) by albumin, transferrin, iron, unsaturated fatty acid, lecithin and cholesterol

Three-Dimensional Bioprinting in Vascular Tissue Engineering and Tissue Vascularization of Cardiovascular Diseases

In the 21st century, significant progress has been made in repairing damaged materials through material engineering. However, the creation of large-scale artificial materials still faces a major challenge in achieving proper vascularization. To address this issue, researchers have turned to biomaterials and three-dimensional (3D) bioprinting techniques, which allow for the combination of multiple biomaterials with improved mechanical and biological properties that mimic natural materials. Hydrogels, known for their ability to support living cells and biological components, have played a crucial role in this research. Among the recent developments, 3D bioprinting has emerged as a promising tool for constructing hybrid scaffolds. However, there are several challenges in the field of bioprinting, including the need for nanoscale biomimicry, the formulation of hydrogel blends, and the ongoing complexity of vascularizing biomaterials, which requires further research. On a positive note, 3D bioprinting offers a solution to the vascularization problem due to its precise spatial control, scalability, and reproducibility compared with traditional fabrication methods. This paper aims at examining the recent advancements in 3D bioprinting technology for creating blood vessels, vasculature, and vascularized materials. It provides a comprehensive overview of the progress made and discusses the limitations and challenges faced in current 3D bioprinting of vascularized tissues. In addition, the paper highlights the future research directions focusing on the development of 3D bioprinting techniques and bioinks for creating functional materials.

Improvements in in vitro spermatogenesis: oxygen concentration, antioxidants, tissue-form design, and space control

Incorporation of bovine serum-derived albumin formulation (AlbuMAX) into a basic culture medium, MEMα, enables the completion of in vitro spermatogenesis through testicular tissue culture in mice. However, this medium was not effective in other animals. Therefore, we sought an alternative approach for in vitro spermatogenesis using a synthetic medium without AlbuMAX and aimed to identify its essential components. In addition to factors known to be important for spermatogenesis, such as retinoic acid and reproductive hormones, we found that antioxidants (vitamin E, vitamin C, and glutathione) and lysophospholipids are vital for in vitro spermatogenesis. Moreover, based on our experience with microfluidic devices (MFD), we developed an alternative approach, the PDMS-ceiling method (PC method), which involves simply covering the tissue with a flat chip made of PDMS, a silicone resin material used in MFD. The PC method, while straightforward, integrates the advantages of MFD, enabling improved and uniform oxygen and nutrient supply via tissue flattening. Furthermore, our studies underscored the significance of lowering the oxygen concentration to 10-15%. Using an integrated cultivation method based on these findings, we successfully achieved in vitro spermatogenesis in rats, which has been a long-standing challenge. Further improvements in culture conditions would pave the way for spermatogenesis completion in diverse animal species.

Hematopoietic Stem Cells Culture, Expansion and Differentiation: An Insight into Variable and Available Media

Owing to differentiation and self-renewal capacity, hematopoietic stem cells clasp potentiality to engender all blood cell types, leading to their immense competence to play a diverse role in therapeutic applications. Although these stem cells are the most investigated and exploited until now, further research is still essential to comprehend their nature, fate, and potential. Enhanced usage of hematopoietic stem cells in research and therapeutics intensified the requirement of expansion and differentiation of hematopoietic stem cells under in vitro conditions. Since these cells remain in senescence for a prolonged period before isolation, selection of appropriate growth medium along with supplements and culture conditions are crucial to initiate their cell division and to designate their destiny. The precise equilibrium between self-renewal and differentiation of stem cells sustained by exclusive medium along with special growth or differentiation factors is accountable for generating diverse cell lineages. Maintenance of hematopoietic stem and progenitor cell lines along with the advancement of research work generate an inexorable demand for production and commercialization of specialized stem cell culture media, with or without serum along with specific growth factors and supplements. Media commercialization for precise stem cell types, culturing and differentiation is a cost-effective developing field. Here in this review, we are assembling various types of hematopoietic stem cell self-renewal, expansion and differentiation media along with supplements and culture conditions, either developed and used by various scientists or are available commercially.

Antioxidant vitamins and lysophospholipids are critical for inducing mouse spermatogenesis under organ culture conditions

In vitro mouse spermatogenesis using a classical organ culture method became possible by supplementing basal culture medium with only the product of bovine serum albumin purified by chromatography (AlbuMAX), which indicated that AlbuMAX contained every chemical factor necessary for mouse spermatogenesis. However, since the identity of these factors was unclear, improvements in culture media and our understanding of the nutritional and signal substances required for spermatogenesis were hindered. In the present study, chemically defined media (CDM) without AlbuMAX was used to evaluate each supplementary factor and their combinations for the induction of spermatogenesis. Similar to in vivo conditions, retinoic acid, triiodothyronine (T₃ ), and testosterone (T) were needed. Based on differences in spermatogenic competence between AlbuMAX, fetal bovine serum, and adult bovine serum, we identified α-tocopherol, which strongly promoted spermatogenesis when combined with ascorbic acid and glutathione. Differences were also observed in the abilities of lipids extracted from AlbuMAX using two different methods to induce spermatogenesis. This led to the identification of lysophospholipids, particularly lysophosphatidylcholine, lysophosphatidic acid, and lysophosphatidylserine, as important molecules for spermatogenesis. New CDM formulated based on these results induced and promoted spermatogenesis as efficiently as AlbuMAX-containing medium. In vitro spermatogenesis with CDM may provide a unique experimental system for research on spermatogenesis that cannot be performed in in vivo experiments.

A Few Key Historical Events in the Antibody Field: The Alacritous Antibody

We have coined the term "alacrity" to describe the extraordinary diversity of B cell activation potentials, even among cells in a single B cell clone responding to a single antigen. The discovery of methodologies for B cell culture in limiting dilution allowed scientists to identify the source of cellular heterogeneity among cells of the immune system. Analyses of individual B cells set the stage for more detailed descriptions of the factors that diversify B cell functions, some of which will be expanded upon by partner articles in this B cell issue.

Human fetal liver cultures support multiple cell lineages that can engraft immunodeficient mice

During prenatal development the liver is composed of multiple cell types with unique properties compared to their adult counterparts. We aimed to establish multilineage cultures of human fetal liver cells that could maintain stem cell and progenitor populations found in the developing liver. An aim of this study was to test if maturation of fetal hepatocytes in short-term cultures supported by epidermal growth factor and oncostatin M can improve their ability to engraft immunodeficient mice. Fetal liver cultures supported a mixture of albumin⁺ cytokertin-19⁺ hepatoblasts, hepatocytes, cholangiocytes, CD14⁺⁺CD32⁺ liver sinusoidal endothelial cells (LSECs) and CD34⁺CD133⁺ haematopoietic stem cells. Transplantation of cultured cells into uPA-NOG or TK-NOG mice yielded long-term engraftment of hepatocytes, abundant LSEC engraftment and multilineage haematopoiesis. Haematopoietic engraftment included reconstitution of B-, T- and NK-lymphocytes. Colonies of polarized human hepatocytes were observed surrounded by human LSECs in contact with human CD45⁺ blood cells in the liver sinusoids. Thus, fetal liver cultures support multiple cell lineages including LSECs and haematopoietic stem cells while also promoting the ability of fetal hepatocytes to engraft adult mouse livers. Fetal liver cultures and liver-humanized mice created from these cultures can provide useful model systems to study liver development, function and disease.

Serum-free Erythroid Differentiation for Efficient Genetic Modification and High-Level Adult Hemoglobin Production

In vitro erythroid differentiation from primary human cells is valuable to develop genetic strategies for hemoglobin disorders. However, current erythroid differentiation methods are encumbered by modest transduction rates and high baseline fetal hemoglobin production. In this study, we sought to improve both genetic modification and hemoglobin production among human erythroid cells in vitro. To model therapeutic strategies, we transduced human CD34⁺ cells and peripheral blood mononuclear cells (PBMCs) with lentiviral vectors and compared erythropoietin-based erythroid differentiation using fetal-bovine-serum-containing media and serum-free media. We observed more efficient transduction (85%-93%) in serum-free media than serum-containing media (20%-69%), whereas the addition of knockout serum replacement (KSR) was required for serum-free media to promote efficient erythroid differentiation (96%). High-level adult hemoglobin production detectable by electrophoresis was achieved using serum-free media similar to serum-containing media. Importantly, low fetal hemoglobin production was observed in the optimized serum-free media. Using KSR-containing, serum-free erythroid differentiation media, therapeutic adult hemoglobin production was detected at protein levels with β-globin lentiviral transduction in both CD34⁺ cells and PBMCs from sickle cell disease subjects. Our in vitro erythroid differentiation system provides a practical evaluation platform for adult hemoglobin production among human erythroid cells following genetic manipulation.

Humanized culture medium for clinical expansion of human erythroblasts

Ex vivo-generated erythroblasts represent alternative transfusion products. However, inclusion of bovine components in media used for their growth precludes clinical use, highlighting the importance of developing culture media based on pharmaceutical grade reagents. In addition, because adult blood generates ex vivo lower numbers of erythroblasts than cord blood, cord blood has been proposed as the source of choice for ex vivo erythroblast production. To clarify the potential of adult blood to generate erythroblasts ex vivo, experiments were designed to identify growth factors [stem cell factor (SCF), interleukin-3 (IL-3), erythropoietin (EPO), and/or thrombopoietin (TPO)] and the optimal concentration and addition schedule of hormones (dexamethasone and estradiol) sustaining maximal erythroid amplification from adult blood mononuclear cells (MNC) using media with serum previously defined as human erythroid massive amplification culture (HEMA(ser)). Adult MNC stimulated with SCF and IL-3 in combination with EPO generated a 6-12-fold increase in erythroid cells while TPO was ineffective. Dexamethasone and estradiol (both at 10(-6) M) exerted partially overlapping but nonredundant functions. Dexamethasone was indispensable in the first 10 days of culture while estradiol was required from day 10 on. The growth factor and hormone combinations identified in HEMA(ser) were then used to formulate a media composed of dialyzed pharmaceutical grade human albumin, human albumin-lipid liposomes, and iron-saturated recombinant human tranferrin (HEMA(def)). HEMA(def) sustained erythroid amplification as efficiently as HEMA(ser) for cord blood MNC and 10-fold higher than HEMA(ser) for adult blood MNC. In fact, the numbers of erythroblasts generated in HEMA(def) by adult MNC were similar to those generated by cord blood MNC. In conclusion, this study identifies growth factors, hormone combinations, and human protein-based media that allow similar levels of ex vivo erythroid expansion from adult and cord blood MNC, paving the way to evaluate adult blood as a source of ex vivo-expanded erythroblasts for transfusion.

Mapping cell surface antigen expression of haemopoietic progenitor cells using monoclonal antibodies

A library of monoclonal antibodies which show selective reactivity with particular cells or gene products (e.g. HLA-DR, glycophorin) of different cell lineages in the haemopoietic system has been compiled. Using these probes in conjunction with the fluorescence-activated cell sorter (FACS) the pattern and sequence of cell surface antigenic expression on haemopoietic progenitor cells have been mapped. A cell is identified in bone marrow which has a unique membrane phenotype and the nuclear enzyme terminal deoxynucleotidyl transferase. Its composite phenotype is identical to that seen in the common variant of acute lymphoblastic leukaemia (ALL). It is suggested that this cell is a putative B lineage progenitor which provides the major target for ALL. Detailed analysis of erythroid differentiation with monoclonal antibodies on the FACS reveals an intriguing pattern of antigenic expression in which HLA-DR, glycophorin and band III appear in sequence. HLA-DR (Ia-like antigen) may be present on all or most committed haemopoietic progenitor cells and could play an important role in cell interactions regulating early haemopoiesis.

Differential Amplification of Murine Bipotent Megakaryocytic/Erythroid Progenitor and Precursor Cells During Recovery from Acute and Chronic Erythroid Stress

Two murine bipotent erythroid/megakaryocytic cells, the progenitor (MEP) and precursor (PEM) cells, recently have been identified on the basis of the phenotypes of linnegc-kitposSca-1neg CD16/CD32lowCD34low and TER119pos4A5pos or 2D5pos, respectively. However, the functional relationship between these two subpopulations and their placement in the hemopoietic hierarchy is incompletely understood. We compared the biological properties of these subpopulations in marrow and spleen of mice with and without acute or chronic erythroid stress. MEP cells, but not PEM cells, express c-kit, respond to stem cell factor in vitro, and form spleen colonies in vivo. PEM cells comprise up to 50%-70% of the cells in BFU-E-derived colonies but are not present among the progeny of purified MEP cells cultured under erythroid and megakaryocytic permissive conditions. PEM cells increase 10- to 20-fold under acute and chronic stress, whereas MEP cell increases (21%-84%) are observed only in acutely stressed animals. These data suggest that MEP and PEM cells represent distinct cell populations that may exist in an upstream-downstream differentiation relationship under conditions of stress. Whereas the dynamics of both populations are altered by stress induction, the differential response to acute and chronic stress suggests different regulatory mechanisms. A model describing the relationship between MEP, PEM, and common myeloid progenitor cells is presented.

Immune thrombocytopenic purpura (ITP) plasma and purified ITP monoclonal autoantibodies inhibit megakaryocytopoiesis in vitro

To determine if megakaryocytes are targeted by immune thrombocytopenic purpura (ITP) autoantibodies, as are platelets, we have studied the effects of ITP plasma on in vitro megakaryocytopoiesis. Umbilical cord blood mononuclear cells were incubated in the presence of thrombopoietin and 10% plasma from either ITP patients (n = 53) or healthy donors. The yield of megakaryocytic cells, as determined by flow cytometry, was significantly reduced in the presence of ITP plasma containing antiplatelet glycoprotein Ib (GPIb) autoantibodies (P <.001) as compared with both the control and patient plasma with no detectable anti-GPIIb/IIIa or anti-GPIb autoantibodies. Platelet absorption of anti-GPIb autoantibodies in ITP plasmas resulted in double the megakaryocyte production of the same plasmas without absorption, whereas platelet absorption of control plasma had no effect on megakaryocyte yield. Furthermore, 2 human monoclonal autoantibodies isolated from ITP patients, 2E7, specific for human platelet glycoprotein IIb heavy chain, and 5E5, specific for a neoantigen on glycoprotein IIIa expressed on activated platelets, had significant inhibitory effects on in vitro megakaryocytopoiesis (P <.001). Taken together, these data indicate that autoantibodies against either platelet GPIb or platelet GPIIb/IIIa in ITP plasma not only are involved in platelet destruction, but may also contribute to the inhibition of platelet production.

Induction of globin mRNA expression by interleukin-3 in a stem cell factor-dependent SV-40 T-antigen-immortalized multipotent hematopoietic cell line

Erythropoiesis requires the stepwise action on immature progenitors of several growth factors, including stem cell factor (SCF), interleukin 3 (IL-3), and erythropoietin (Epo). Epo is required to sustain proliferation and survival of committed progenitors and might further modulate the level of expression of several erythroid genes, including globin genes. Here we report a new SCF-dependent immortalized mouse progenitor cell line (GATA-1 ts SCF) that can also grow in either Epo or IL-3 as the sole growth factor. When grown in SCF, these cells show an "open" chromatin structure of the beta-globin LCR, but do not significantly express globin. However, Epo or IL-3 induce globin expression and are required for its maintainance. This effect of IL-3 is unexpected as IL-3 was previously reported either to be unable to induce hemoglobinization, or even to antagonize it. This suggests that GATA-1 ts SCF cells may have progressed to a stage in which globin genes are already poised for expression and only require signal(s) that can be elicited by either Epo or IL-3. Through the use of inhibitors, we suggest that p38 may be one of the molecules modulating induction and maintenance of globin expression.

Development of myelofibrosis in mice genetically impaired for GATA-1 expression (GATA-1(low) mice)

The phenotype induced by the GATA-1(low) (neodeltaHS) mutation is here further characterized by analyzing the hemopoietic system during the aging (up to 20 months) of a GATA-1(low) colony (135 mutants and 40 normal littermates). Mutants expressed normal hematocrit values (Hct = 45.9 +/- 4.0) until 12 months but became anemic from 15 months on (Hct = 30.9 +/- 3.9; P <.05). Anemia was associated with several markers of myelofibrosis such as the presence of tear-drop poikilocytes and progenitor cells in the blood, collagen fibers in the marrow and in the spleen, and hemopoietic foci in the liver. Semiquantitative reverse transcription-polymerase chain reaction showed that growth factor genes implicated in the development of myelofibrosis (such as osteocalcin, transforming growth factor-beta1, platelet-derived growth factor, and vascular endothelial growth factor) were all expressed in the marrow from the mutants at higher levels than in corresponding normal tissues. The GATA-1(low) mutants experienced a slow progression of the disease because the final exitus was not observed until at least 15 months with a probability of survival more favorable than that of W/Wv mice concurrently kept in the animal facility (P <.001, by Kaplan-Meier analysis). In conclusion, impaired GATA-1 expression may contribute to the development of myelofibrosis, and the GATA-1(low) mutants may represent a suitable animal model for the human disease that may shed light on its pathogenesis.

Transferrin Receptor Expression and Iron Uptake in the Injured and Regenerating Rat Sciatic Nerve

Iron-saturated transferrin is a ubiquitous growth factor that plays a critical role in cellular iron uptake, growth and proliferation. Here we have studied the expression and distribution of transferrin receptors and iron uptake following injury of the rat sciatic nerve. Axotomy led to a massive but transient increase (days 2 - 9, maximum day 4) in [125I]transferrin binding at the site of the injury and in the distal, denervated part of the crushed or resected sciatic nerve, shortly preceding the time course of cellular proliferation (Friede and Johnstone, Acta Neuropathol, 7, 218 - 231, 1967; Jurecka et al., Acta Neuropathol, 32, 299 - 312, 1975). An additional, transient increase in specific binding was observed during reinnervation after reconnection of the resected sciatic nerve. Immunocytochemistry using the Ox-26 monoclonal antibody revealed strong and simultaneous expression of the transferrin receptor protein on two different cell types: on a subpopulation of blood-borne macrophages invading the injured peripheral nerve and on Schwann cells reacting to denervation and reinnervation. In addition, studies using intravenously injected radioactive iron (59Fe3+) showed a massive increase in endoneural iron uptake confined to the lesion site and to the distal part of the axotomised sciatic nerve, parallel to the time course of reactive transferrin receptor expression. Since iron is an essential cofactor of a number of key enzymes needed in energy metabolism and DNA synthesis, these data suggest that the induction of transferrin receptor expression may play an important role in the regulation of cellular growth and proliferation during peripheral nerve regeneration.

Isolation, growth and identification of colony-forming cells with erythroid, myeloid, dendritic cell and NK-cell potential from human fetal liver

The study of hematopoietic stem cells (HSCs) and the process by which they differentiate into committed progenitors has been hampered by the lack of in vitro clonal assays that can support erythroid, myeloid and lymphoid differentiation. We describe a method for the isolation from human fetal liver of highly purified candidate HSCs and progenitors based on the phenotypes CD38(-)CD34(++) and CD38(+)CD34(++), respectively. We also describe a method for the growth of colony-forming cells (CFCs) from these cell populations, under defined culture conditions, that supports the differentiation of erythroid, CD14/CD15(+) myeloid, CD1a(+) dendritic cell and CD56(+) NK cell lineages. Flow cytometric analyses of individual colonies demonstrate that CFCs with erythroid, myeloid and lymphoid potential are distributed among both the CD38(-) and CD38(+) populations of CD34(++) progenitors.

Accentuated response to phenylhydrazine and erythropoietin in mice genetically impaired for their GATA-1 expression (GATA-1(low) mice)

The response of mice genetically unable to up-regulate GATA-1 expression (GATA-1(low) mice) to acute (phenylhydrazine [PHZ]-induced anemia) and chronic (in vivo treatment for 5 days with 10 U erythropoietin [EPO] per mouse) erythroid stimuli was investigated. Adult GATA-1(low) mice are profoundly thrombocytopenic (platelet counts [x 10(9)/L] 82.0 +/- 28.0 vs 840 +/- 170.0 of their control littermates, P <.001) but have a normal hematocrit (Hct) (approximately.47 proportion of 1.0 [47%]). The spleens of these mutants are 2.5-fold larger than normal and contain 5-fold more megakaryocytic (4A5(+)), erythroid (TER-119(+)), and bipotent (erythroid/megakaryocytic, TER-119(+)/4A5(+)) precursor cells. Both the marrow and the spleen of these animals contain higher frequencies of burst-forming units-erythroid (BFU-E)- and colony-forming units-erythroid (CFU-E)-derived colonies (2-fold and 6-fold, respectively) than their normal littermates. The GATA-1(low) mice recover 2 days faster from the PHZ-induced anemia than their normal littermates (P <.01). In response to EPO, the Hct of the GATA-1(low) mice raised to.68 proportion of 1.0 (68%) vs the.55 proportion of 1.0 (55%) reached by the controls (P <.01). Both the GATA-1(low) and the normal mice respond to PHZ and EPO with similar (2- to 3-fold) increases in size and cellularity of the spleen (increases are limited mostly to cells, both progenitor and precursor, of the erythroid lineage). However, in spite of the similar relative cellular increases, the increases of all these cell populations are significantly higher, in absolute cell numbers, in the mutant than in the wild-type mice. In conclusion, the GATA-1(low) mutation increases the magnitude of the response to erythroid stimuli as a consequence of the expansion of the erythroid progenitor cells in their spleen.

Erythropoietin-dependent suppression of the expression of the beta subunits of the interleukin-3 receptor during erythroid differentiation

To clarify how erythroid cells lose their response to interleukin-3 (IL-3), we analyzed the expression of the alpha (alpha(IL-3)) and beta (beta(IL-3)/beta(com)) subunits of its receptor in a panel of murine cell lines immortalized at different stages of hemopoietic differentiation. The panel was composed by the mast cell line 32D and by its granulo-monocytic (32D GM), granulocytic (32D G), and erythroid (32D Epo1.1 and Epo) subclones. The 32D Epo cells grow only in erythropoietin (EPO) while the Epo1.1 subclone grows in either EPO or IL-3. The phenotype of these cells is that of early (expression of globins and erythroid-specific carbonic anhydrase II) and late (also expression of the erythroid-specific band 4.1 mRNA) erythroblasts when they grow in IL-3 or EPO, respectively. All the cell lines expressed comparable levels of alpha(IL-3). In contrast, the expression of beta(IL-3)/beta(com) was restricted to cells growing in IL-3 and was barely detectable in 32D Epo and 32D Epo1.1 cells growing in EPO. When switched from EPO to IL-3, 32D Epo1.1 cells expressed 10 times more beta(IL-3)/beta(com) by rapidly activating (within 1 h) their transcription rate. When reexposed to EPO, 32D Epo1.1 cells first expressed (1-6 h) more beta(IL-3)/beta(com) (2 times) but suppressed such an expression at later time points (by 48 h). The beta(IL-3)/beta(com) mRNA half-life was also different when 32D Epo1.1 cells grew in EPO or IL-3 (2-3 h vs >5 h, respectively). These results indicate that EPO specifically induces transcriptional and posttranscriptional downmodulation of beta(IL-3)/beta(com) expression in late erythroid cells.

Identification and characterization of a bipotent (erythroid and megakaryocytic) cell precursor from the spleen of phenylhydrazine-treated mice

We have identified a cell population expressing erythroid (TER-119) and megakaryocyte (4A5) markers in the bone marrow of normal mice. This population is present at high frequency in the marrows and in the spleens involved in the erythroid expansion that occurs in mice recovering from phenylhydrazine (PHZ)-induced hemolytic anemia. TER-119+/4A5+ cells were isolated from the spleen of PHZ-treated animals and were found to be blast-like benzidine-negative cells that generate erythroid and megakaryocytic cells within 24-48 hours of culture in the presence of erythropoietin (EPO) or thrombopoietin (TPO). TER-119+/4A5+ cells represent a late bipotent erythroid and megakaryocytic cell precursors that may exert an important role in the recovery from PHZ-induced anemia.

Identification and characterization of a bipotent (erythroid and megakaryocytic) cell precursor from the spleen of phenylhydrazine-treated mice

We have identified a cell population expressing erythroid (TER-119) and megakaryocyte (4A5) markers in the bone marrow of normal mice. This population is present at high frequency in the marrows and in the spleens involved in the erythroid expansion that occurs in mice recovering from phenylhydrazine (PHZ)-induced hemolytic anemia. TER-119+/4A5+ cells were isolated from the spleen of PHZ-treated animals and were found to be blast-like benzidine-negative cells that generate erythroid and megakaryocytic cells within 24-48 hours of culture in the presence of erythropoietin (EPO) or thrombopoietin (TPO). TER-119+/4A5+ cells represent a late bipotent erythroid and megakaryocytic cell precursors that may exert an important role in the recovery from PHZ-induced anemia.

Clonal growth of human acute leukemia cells in serum-free methylcellulose medium

The clonal growth of human acute leukemia cell line (K562) and acute myeloid leukemia cells in the serum-free culture (SFC) was studied in order to establish a SFC system which could replace the effects of serum by using semi-solid methylcellulose culture technique. Our results showed that the clonal growth of K562 cells in semi-solid culture was dependent on exogenous serum. The K562 could be grown in SFC supplemented with 4 major replacing substances. The multifactor and multilevel orthogonal experiment demonstrated that the colony formation was statistically influenced by the 4 replacing substances at various concentrations (P < 0.01). Among them, bovine serum albumin had greatest effect on clonal growth of K562 cells with the optimal concentration being 15 mg/L, followed by transferring, cholesterol and insulin with their optimal concentrations being of 150 mg/L, 7.8 mg/L and 7.0 mg/L respectively. SFC system was formed with the 4 substances at their optimal concentrations. Colony formation of the blast cells in 10 patients with acute myeloid leukemia was observed in this SFC system. There was a heterogeneity of acute myeloid leukemia cells among the 10 patients in response to the growth substances. In SFC system, there was a linear relationship between the number of the clonal formation and the count of the added cells, indicating the colony growth of the cells. Primary acute leukemia cells maintained in SFC system in 10 cases could completely form clones. The colony formation number in some cases in SFC system was more than that of the serum-containing culture. The SFC system could partially replace the serum for study of the clonal formation of human leukemia cells.

Stem cell factor induces proliferation and differentiation of fetal progenitor cells in the mouse

We have investigated the kinetics of the amplification of the progenitor cell compartments (CFC) in haemopoietic organs during murine ontogenesis and compared the growth requirements of fetal and adult CFC. Two haemopoietic phases were recognized in the fetal liver (FL): an exponential growth phase, from 11.5 to 15.5 d post conception (p.c.), during which the mean number of nucleated cells and of CFC in the FL increased from 4.9 x 10(5) to 7.0 x 10(7) and from 4.5 x 10(3) to 2.7 x 10(5), respectively, and a recessive phase after 15.5 d p.c., during which the CFC number in the FL gradually decreased, although some CFC were still detectable in the liver after birth. In serum-deprived cultures, FL and adult marrow (AM) CFC had similar responses to GM-CSF, and did not respond to G-CSF or IL-3. In contrast, FL, but not AM, erythroid colonies grew Epo-independently whereas SCF alone induced formation of maximal numbers of erythroid bursts from FL, but not from AM cells. The proliferative and differentiative effect of SCF alone on fetal cells was confirmed in serum-deprived cultures of purified early progenitor cells isolated by cell sorting on the basis of multiple parameters from FL and AM light-density cells. In culture of purified FL cells, SCF alone induced a similar amplification of total cells (maximal amplification at day 12: 800-300-fold) and total CFC (11-38-fold of maximal amplification at day 6) to the combination of SCF plus IL-3 (1300-800-fold amplification of total cells and 31-88-fold amplification of CFC). In contrast, SCF alone allowed only survival of purified AM early progenitor cells. Therefore FL early progenitor cells have an intrinsic higher potential than their adult counterpart to respond to SCF, confirming the potent role of this growth factor in the development of the murine haemopoietic system.

The making of an erythroid cell. Molecular control of hematopoiesis

The number of circulating red cells is regulated by the daily balance between two processes: the destruction of the old red cells in the liver and the generation of new cells in the bone marrow. The process during which hematopoietic stem cells generate new red cells is called erythropoiesis. This manuscript will describe the molecular mechanisms involved in the process of erythroid differentiation as we understand them today. In particular it will review how erythroid specific growth factor-receptor interactions activate specific transcription factors to turn on the expression of the genes responsible for the establishment of the erythroid phenotype.

Recombinant Human Albumin in Cell Culture: Evaluation of Growth-Promoting Potential for NRK and SCC-9 Cells In Vitro

Serum-derived albumin has for a long time been used in cell culture media, but the exact role of albumin and/or impurities bound to albumin has not been precisely defined. In this study, recombinant human albumin was evaluated for its growth-promoting activity on two cell lines, NRK and SCC-9. For NRK cells, the recombinant human albumin was found to exert an inhibitory effect. The fact that fatty acid free HSA was also inhibitory while HSA fraction V was stimulatory suggested a role for fatty acids or some other bound moieties in growth stimulation by HSA fraction V. Addition of oleic acid, cholesterol, phosphatidylcholine, phosphatidylserine or a combination of these lipids, however, did not significantly improve the growth stimulating activity of either fatty acid free HSA or the recombinant human albumin. For SCC-9 cells, both recombinant human albumin and fatty acid free HSA showed slight stimulation (although they were not as active as HSA fraction V), suggesting that in some cell systems, the albumin molecule per se may promote cell growth and survival.

Growth factor receptor expression during in vitro differentiation of partially purified populations containing murine stem cells

We have investigated, by semiquantitative RT-PCR, the kinetics of activation of hematopoietic receptors and differentiation markers in partially purified murine hematopoietic stem cells (HSC) induced to differentiate in serum-free culture with combinations of growth factor (GF). The combinations of GF used sustained either multilineage [stem cell factor (SCF) + interleukin 3 (IL-3), or erythroid [SCF + IL-3 + erythropoietin (Epo)] or myeloid [SCF + IL-3 + granulocyte colony-stimulating factor (G-CSF)] differentiation. The GF receptor genes investigated were the alpha and beta subunits of the IL-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor, the erythropoietin receptor, the G-CSF receptor, and c-Fms, the receptor for macrophage colony-stimulating factor (M-CSF). The expression of Gata1 and alpha- and beta-globin was investigated at the same time as a marker of erythroid differentiation. HSC were purified according to standard protocols, which include partitioning of lineage-negative bone marrow cells with the mitochondrial dye Rhodamine 123 (Rho) into Rho-dull (> or = 17% of which reconstitute long-term hematopoiesis in recipient mice) and into Rho-bright (which are as capable as Rho-dull of multilineage differentiation but do not permanently reconstitute the host). The following pattern of expression was observed: the alpha subunit of the IL-3 receptor clearly was expressed in both Rho-bright and Rho-dull cells at the outset, and its expression did not change over time in culture. The beta subunits of the IL-3 and GM-CSF receptor, the alpha subunit of the GM-CSF receptor, the Epo and G-CSF receptors and Fms barely were expressed in purified Rho-bright and Rho-dull cells, but their expression increased in cells cultured both in erythroid and in myeloid GF combinations. Gata1 was expressed maximally in Rho-bright cells but was below the level of detection in Rho-dull cells. Rho-dull cells expressed Gata1 when cultured both in erythroid and in myeloid GF combinations. In contrast, alpha- and beta-globin, which also were not expressed in the purified cells, were induced only in cells stimulated with Epo. These results indicate that the genes for all the GF receptors investigated (with the exception of the alpha subunit of the IL-3 receptor) are expressed at low levels, if any, in purified Rho-bright or Rho-dull cells, but are expressed in their progeny cultured either in erythroid or myeloid GF combinations. The expression of the Epo receptor, in particular, is activated both in erythroid (alpha- and beta-globin positive and in myeloid (alpha- and beta-globin negative) cells. Therefore, activation of the expression of the Epo receptor gene and activation of the erythroid differentiation program are two independent events in normal hematopoiesis.

Comparison of whole serum-deprived media for ex vivo expansion of hematopoietic progenitor cells from cord blood and mobilized peripheral blood mononuclear cells

A whole serum-deprived (WSD) medium was developed and optimized for expansion of colony-forming cells (CFC) in cord blood (CB) mononuclear cell (MNC) cultures. This medium was compared with four commercially available WSD media (commercial media), three WSD media whose compositions have been publicly disclosed (public media), two serum-containing media, and two basal media, for cell and CFC expansion in 10-day CB and mobilized peripheral blood (PB) MNC cultures supplemented with interleukin-3 (IL-3), IL-6, and stem cell factor (SCF). Selected WSD media and both serum-containing media gave significant CFC expansion in CBMNC and PBMNC cultures. The serum-containing human long-term medium gave the greatest cell (3.0-fold) and CFC (25-fold) expansions in CBMNC cultures, whereas our medium maintained the most cells (93% of input) and gave the greatest CFC expansion (6.1-fold) for PBMNC cultures. Of the commercial media, Progenitor-34 gave the greatest cell expansion (1.2-fold) and X VIVO-10 gave the greatest CFC expansion (11-fold) for CBMNC cultures, and Progenitor-34 maintained the most cells (83% of input) and gave the greatest CFC expansion (3.1-fold) for PBMNC cultures. Of the public media (including ours), our medium gave the greatest cell (1.4-fold) and CFC (6.1-fold) expansion for CBMNC cultures. Although there were slight correlations between cell and CFC expansion in 10-day CBMNC and PBMNC cultures (r2 of 0.848 and 0.594, respectively), the correlations did not give reliable predictions for medium selection. In addition, the different media favored expansion of different CFC types and performed differently for cultures using different cell sources (CB versus PB). Taken together, these results suggest that media must be carefully screened for the cell source to be cultured and the cell type(s) to be produced (e.g. total cells, CFC).

Inhibition of apoptosis by the expression of antisense Nedd2

Nedd2 belongs to a family of mammalian cysteine proteases which share similarity with the Caenorhabditis elegans cell death protein, Ced-3. Overexpression of Nedd2 has been shown to induce apoptosis in mammalian cells but in the absence of a specific known inhibitor, it remains to be seen whether this represents cytotoxic effects of the Nedd2 protease or the specific activation of an apoptotic pathway. The present work shows that the factor-dependent cell line FDC-P1 expressing mouse antisense Nedd2 mRNA, exhibits significant inhibition of cell death upon removal of the cytokines, thus providing evidence for a direct role of Nedd2 in mediating apoptosis.

A newly developed serum-free culture system: clonal growth of human acute myelogeneous leukemia (AML) progenitors--a report of 14 AML cases

A new serum-free culture (SFC) system for human AML-CFU was established and the colony-promoting activity of four recombinant human hematopoietic growth factors (rhHGFs) including granulocyte-macrophage colony-stimulating factor (rhGM-CSF), interleukin-3 (rhIL-3), erythropoietin (rhEPO) and newly developed stem cell factor (rhSCF) were investigated in this SFC system. Under the orthogonal design condition, it was found that human AML-CFU presented optimal clonal growth in an environment of bovine serum albumin (0.6%), saturated human transferrin (2 x 10(-6) mol/L), cholesterol (2.8 micrograms/ml), bovine insulin (15 micrograms/ml), bovine hemin (0.05 mmol/L), linoleic acid (2.8 micrograms/ml), and IMDM. Spontaneously growing colonies were observed in 11 out of 14 cases studied. The plating efficiencies obtained by culturing with rhGM-CSF, rhIL-3, and rhSCF were 0.776 +/- 0.621%, 0.574 +/- 0.510%, and 0.647 +/- 0.543% (mean +/- s), respectively. There was one case (M3b) showing no response to all HGFs in both SFC ad SCC. The clonal growth of AML-CFU obtained from peripheral blood of the patient with M6 was unexpectedly marked. As a whole, the newly designed SFC system has been demonstrated to be useful for culture of human AML-CFU from both bone marrow and peripheral blood.

Transforming growth factor beta 1 is an inducer of erythroid differentiation

Normal human bone marrow cells, highly enriched for burst-forming units-erythroid (BFU-E), were cultured in serum-free medium, in the presence and absence of various factors, to investigate the mechanisms involved in regulating erythroid differentiation. In cultures containing interleukin 3 (IL-3), Steel factor (SF), and erythropoietin (Ep), benzidine-positive erythroblasts first became detectable on day 6. Their numbers then rapidly increased until, by day 16, > 99% of the cells, which were 20,000-fold amplified over input numbers, were benzidine-positive. It is interesting to note that omission of either SF or Ep from this assay markedly enhanced the rate of differentiation and reduced total cell numbers, whereas omission of IL-3 had no effect on the rate of differentiation and only slightly reduced cell numbers. Of various agents tested, the most potent erythroid differentiation inducer (and inhibitor of cell proliferation) was found to be transforming growth factor beta 1 (TGF-beta 1). This cytokine stimulated both the rapid appearance of hemoglobin-positive cells and an early cessation of cell proliferation. Using fluorescently tagged antibodies to glycophorin A and fluorescence-activated cell sorter (FACS) analysis, this phenomenon was shown to be due to an early induction of erythroid differentiation rather than an aberrant production of hemoglobin. Methylcellulose assays indicated that the well-documented reduction of BFU-E colony numbers observed with TGF-beta 1 may actually be due to a TGF-beta 1-induced "conversion" of BFU-E into colony-forming units-erythroid (CFU-E). Thus, in vivo, TGF-beta 1 might serve, in part, to decrease the number of mature erythrocytes by stimulating BFU-E to skip a number of cell divisions and differentiate early.

Evidence for a selective inhibitory effect of thrombin on megakaryocyte progenitor growth mediated by the thrombin receptor

An efficient method for the culture of human megakaryocyte precursors in serum-free medium has been developed facilitating study of the effect of regulators of megakaryocyte growth and maturation without interference by serum-derived factors. We have investigated how megakaryocytes and their precursors respond to the procoagulant enzyme, thrombin. In addition to its already documented agonist effect on mature megakaryocytes, thrombin was found to have a marked inhibitory effect on the growth of megakaryocyte colonies from CD34+ bone marrow cells stimulated by IL3. This inhibitory effect, not previously reported, was selective for megakaryocytic cells. The growth of granulomonocytic and erythroid colonies was not affected. A monoclonal antibody which neutralized the effect of exogenous transforming growth factor beta (TGF beta) was unable to fully neutralize the inhibitory effect of thrombin. With the use of a synthetic peptide, corresponding to the tethered thrombin receptor ligand, and of a recombinant inactive form of thrombin, we provide direct evidence that both the inhibitory effect of thrombin on megakaryocyte proliferation and its agonist effect on mature megakaryocytes are mediated by a receptor analogous to the recently cloned platelet thrombin receptor.

Impaired proliferation and differentiation of myelodysplastic CD34+ cells

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders of hematopoiesis entailing hyperproliferative and ineffective hematopoiesis resulting in refractory cytopenia(s), and increased risk of transformation into acute myeloblastic leukemia (AML). The widely used classification defined by the French-American-British group (FAB) recognizes 5 cytological subtypes of different prognosis, based essentially on the presence and the frequency of marrow blasts. The percentage of marrow blasts does not exceed 30%, hence, direct investigations of biological and biochemical events of MDS blast cells have been hampered. The CD34 antigen is currently unique in its narrow specificity of expression on human lymphohematopoietic progenitor cells. This cell membrane phosphoglycoprotein has been used for immunologic blast cell purification, notwithstanding the frequency of marrow blasts, and has provided a set of tools for investigations of MDS i.e. a direct comparison of the nature of blast cells in each of the MDS subtypes, using immunologic, biologic, biochemical and molecular biological methodology. A combination of serum-free medium and a purification method for blast cells provided evidence that the progenitor cell growth abnormalities in these disorders involve a defect in the capacity of progenitor cells to respond to stimulation with growth factor(s), and has presented direct evidence for the manner in which myelodysplastic CD34+ cells are impaired.

In vitro purging of clonogenic leukaemic cells from human bone marrow by interferon-gamma-activated monocytes

With a view to the immunologically mediated purging of autologous bone marrow transplants in acute myeloid leukaemia, the efficacy of cytotoxic monocytes to eradicate leukaemic cells has been studied using clonogenic assays. U937 cells were found to be sensitive to highly purified and interferon-gamma-activated human monocytes whereas HL60 cells were rather resistant as measured in an MTT-based cytotoxicity assay under liquid conditions. A spectrophotometric clonogenic assay measured almost complete inhibition of clonogenic activity for U937 cells at low effector-to-target cell (E/T) ratios of at least 0.1. Limiting dilution analysis detected a 2-3 log10 unit reduction in clonogenic activity. In an experimental mixture of U937 cells with a 20-fold excess of normal bone marrow nuclear cells a maximum 2-log10-unit killing could be measured at E/T = 10. Only at high E/T ratios could a reduction in granulocyte/macrophage-colony-forming units (cfu) be observed with only marginal effects on erythroid cfu and erythroid burst-forming. In conclusion, cytotoxic monocytes are highly potent anti-leukaemic effector cells, as measured in clonogenic assays, that do not compromise normal human progenitors.

Leucovorin rescue of human cancer and bone marrow cells following edatrexate or methotrexate

We have examined the cytotoxic activities of edatrexate (EDX) and methotrexate (MTX) and their reversal by leucovorin in nine human cancer cell lines and in human bone marrow CFU-GM cells. EDX was 3.7- to 123-fold more toxic than MTX against the cancer cell lines and 25-fold against the bone marrow cells. Lower EDX concentrates generally were needed to inhibit cancer cell growth relative to bone marrow cells, however, whereas bone marrow and cancer cell growth were more often susceptible to the same MTX concentrations. The new antifolate was metabolized to long-chain polyglutamates to a greater extent than MTX in seven cell lines. Leucovorin at 0.2 microM rescued two breast cancer and two non-small cell lung cancer cell lines to a lesser extent following EDX than MTX, but significant rescue was observed in two head and neck cancer cell lines that formed large amounts of polyglutamates. These cell lines also accumulated reduced folates to a greater extent than the other cell lines following leucovorin exposure. Leucovorin rescued bone marrow cells following MTX but only partially following the highest EDX concentrations. EDX may enjoy a better therapeutic index than MTX against some cancer cell lines relative to bone marrow precursor cells, especially after leucovorin rescue.

Interferon alpha and 5'-deoxy-5-fluorouridine in colon cancer: effects as single agents and in combination on growth of xenograft tumours

Interferon-alpha (IFN-alpha) enhances the activity of the 5-fluorouracil (5-FU) prodrug 5'-deoxy-5-fluorouridine (5'-dFUrd) in colorectal cancer cells in vitro by upregulating the enzyme pyrimidine nucleoside phosphorylase (PNPase), which is responsible for converting 5'-dFUrd to 5-FU. We examined whether such enhancement also occurs in vivo using human colorectal xenografts in nude mice. The Co-115 line has high basal levels of PNPase and the enzyme level was increased in tumours from mice treated for 3 weeks with 50,000 IU/day (5 days/week) of IFN-alpha A/D. The prodrug 5'-dFUrd (200 mg/day, 5 days/week) had a much greater antitumour activity than 5-FU had when it was used at an approximately equitoxic dose (20 mg/day, 5 days/week). However, because of the high activity of 5'/dFUrd as a single agent, no enhancement by IFN-alpha A/D was observed. Studies on xenografts of WiDr cells indicated that this line is much less sensitive to 5'-dFUrd. However, treatment of animals with IFN-alpha A/D at doses of 75,000 IU/day or 150,000 IU/day resulted in significant inhibition of WiDr tumour growth. Combination treatment with 75 mg/kg/day or 150 mg/kg/day of 5'-dFUrd resulted in enhanced antitumour activity, particularly at the higher dose of IFN-alpha A/D. Synergy of this drug combination was confirmed by isobologram analysis. Analysis of PNPase levels in WiDr tumours, excised from mice treated with IFN-alpha A/D, demonstrated that the enzyme activity was increased by IFN-alpha in a dose-dependent manner. Slight increases were also seen in normal liver and intestine from the same animals. Our results indicate that modulation of converting enzymes for anticancer prodrugs by cytokines could be a novel therapeutic strategy for combination therapy of colorectal cancer.

Time lapse video recordings of highly purified human hematopoietic progenitor cells in culture

Major hurdles in studies of stem cell biology include the low frequency and heterogeneity of human hematopoietic precursor cells in bone marrow and the difficulty of directly studying the effect of various culture conditions and growth factors on such cells. We have adapted the cell analyzer imaging system for monitoring and recording the morphology of limited numbers of cells under various culture conditions. Hematopoietic progenitor cells with a CD34+ CD45RAlo CD71lo phenotype were purified from previously frozen organ donor bone marrow by fluorescence activated cell sorting. Cultures of such cells were analyzed with the imaging system composed of an inverted microscope contained in an incubator, a video camera, an optical memory disk recorder and a computer-controlled motorized microscope XYZ precision stage. Fully computer-controlled video images at defined XYZ positions were captured at selected time intervals and recorded at a predetermined sequence on an optical memory disk. In this study, the cell analyzer system was used to obtain descriptions and measurements of hematopoietic cell behavior, like cell motility, cell interactions, cell shape, cell division, cell cycle time and cell size changes under different culture conditions.

Serum-free medium allows the optimal growth of human megakaryocyte progenitors compared with human plasma supplemented cultures: role of TGF beta

The growth of human megakaryocyte progenitors from human bone marrow (BM) cells was compared using a methylcellulose semisolid assay supplemented either by normal human plasma or by a serum-free medium. Far better growth of megakaryocyte colonies from CD34+ BM cells stimulated by interleukin 3 (IL-3) and interleukin 6 (IL-6) was observed in serum-free medium compared with human plasma supplemented cultures. These results were confirmed in liquid cultures using the same serum-free medium composition. The megakaryocytes were identified by using an immunocytochemical procedure after labeling with an anti-GPIIb-IIIa monoclonal antibody. High percentages (15 to 20%) of megakaryocytes were present in serum-free cultures stimulated by IL-3 alone or combined with IL-6. The absolute number of megakaryocytes in serum-free medium exceeds by 3.3 (IL-3 plus IL-6) to 4.4 (IL-3 alone) times the corresponding number of megakaryocytes observed in human plasma supplemented cultures. The optimal concentration of IL-3 alone was 5 ng/ml, and an optimal synergistic effect of IL-6 (5 ng/ml) was obtained when combined with a suboptimal dose of IL-3 (1 ng/ml). The poor growth of megakaryocyte colonies from CD34+ BM cells in human plasma suggested the presence of an inhibitory factor. When a neutralizing monoclonal antibody against transforming growth factor beta (TGF beta) is present in human plasma supplemented cultures of CD34+ BM cells, the number of megakaryocyte colonies is increased to the level observed in corresponding serum-free cultures. The high efficiency of this serum-free medium to promote the growth of human megakaryocytes will be useful to study the effects of regulators and platelet agonists acting on human megakaryocytes, without interference from factors in the serum.

The in vitro growth of murine high proliferative potential-colony forming cells is not enhanced by growth in a low oxygen atmosphere

The growth of primitive murine hematopoietic progenitors, high proliferative potential colony-forming cells (HPP-CFC), has been reported to be improved in low O2 tension cultures. In this report we investigated the growth of HPP-CFC stimulated by combinations of interleukin (IL)-1, IL-6, kit-ligand (KL), granulocyte (G) colony-stimulating factor (CSF), macrophage-CSF (M-CSF), granulocyte-macrophage-CSF (GM-CSF) and IL-3 in clonal cultures incubated at 7% or 21% O2 tension. Neither the numbers of HPP-CFC colonies nor the number of cells per HPP-CFC colony differed significantly between cultures grown under 7% or 21% O2 tension. The mean number of cells per HPP-CFC colony was found to range from 3.9 x 10(4) to 2.2 x 10(5). The smallest HPP-CFC colonies were stimulated by the cytokine combination IL-1 + IL-6 + KL, whereas the largest colonies were stimulated by a combination of all seven cytokines tested. The growth of erythroid colonies from murine or human bone marrow did, however, show some enhancement when cultured at a lower O2 tension. These results demonstrate that the growth of murine HPP-CFC was not compromised when cultured at ambient O2 concentration.

Recombinant antibody-metallothionein: design and evaluation for radioimmunoimaging

We have produced a chimeric antibody (Ab) in which metallothionein, a well-characterized biological chelator of metals, was genetically fused to the F(ab') domain of the S107 Ab heavy chain. Coexpression with the Ab light chain that conveys specificity for the synthetic antigen phosphocholine was achieved in plasmacytoma cells. Metal- and antigen-binding domains of the Ab-metallothionein hybrid function with normal avidity and specificity. Ab-metallothionein can be efficiently loaded with 99mTc and used to specifically bind phosphocholine-haptenated cells in vitro or to localize plasma-cell ascites tumors in mice. The approach offers potential advantages for producing radiolabeled Ab for targeted radiotherapy and diagnostic imaging.

Human interleukin-9 supports formation of a subpopulation of erythroid bursts that are responsive to interleukin-3

We have investigated the biological activities of recombinant human interleukin-9 (IL-9) on enriched hematopoietic progenitors, alone or in combination with other cytokines, including Epo, G-CSF, IL-3, and GM-CSF, under serum-containing and serum-free cultures. IL-9 alone did not support colony formation. However, IL-9 plus Epo induced erythroid burst (BFU-E) formation derived from peripheral blood (PB) progenitors. Delayed addition experiments demonstrated that a part of bone marrow (BM) derived BFU-E, which seems to be immature, only responded to IL-9 and formed erythroid bursts. The burst-promoting activity (BPA) of IL-9 was confirmed using neutralizing aIL-3, aGM-CSF, and aIL-9 antisera and serum-free culture. IL-9 supported a part of BFU-E population that respond to IL-3, which was almost identical to the number of BFU-E supported by GM-CSF. IL-9 had no additive effect on erythroid and mixed colony formation supported by IL-3. In contrast, IL-9 showed an additive effect on erythroid burst formation supported by GM-CSF in serum-free culture. These data suggest that IL-9 and GM-CSF act on distinct IL-3-responsive BFU-E population. In addition, delayed addition experiment clearly demonstrated that IL-9 supports survival and the early stage of proliferation of BFU-E. These results led us to propose that IL-9 possibly acts as a BPA and selectively supports a subpopulation of early class of BFU-E that respond to IL-3.

Human serum stimulates the production of G-CSF, IL-1, IL-6 and IL-8 by human peripheral blood leucocytes

Human serum induces human peripheral blood leucocytes (PBL) to release an activity stimulating neutrophil colony formation (G-CSA) from human bone marrow cells. By titrating individual growth factors and using specific neutralizing antibodies we showed that: human serum contains very low levels of G-CSF which are by themselves insufficient to stimulate myeloid colony formation in primary human bone marrow cultures and cannot account for the serum releaser activity; that although no detectable levels of IL-1, IL-2, IL-3, IL-4, IL-6 or IL-8 are found in the serum, anti IL-1 antibodies partially block the release of G-CSA when added early during PBL incubation; that PBL incubated in the absence of serum for 2 d produce small amounts of IL-1, IL-6, IL-8 and G-CSF and this is increased 6-16 fold in the presence of human serum; and that the neutrophil colony-stimulating activity released by PBL incubated with human serum is G-CSF.