Stem Cells http://www.peprotech.com/
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Reprints/Permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Sakatoku, H.
Right arrow Articles by Inoue, S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Sakatoku, H.
Right arrow Articles by Inoue, S.
Stem Cells, Vol. 15, No. 4, 268-274, July 1997
© 1997 AlphaMed Press

In Vitro Proliferation and Differentiation of Erythroid Progenitors of Cord Blood

Hiroyuki Sakatokua, Susumu Inouea,b

a Yamada Red Cross Hospital, Mie-ken, Japan;
b Hurley Medical Center and Michigan State University College of Human Medicine, Flint, Michigan, USA

Key Words. Cord blood cells • Erythropoietin • Stem cell factor • Differentiation

Dr. Hiroyuki Sakatoku, Department of Pediatrics, Yamada Red Cross Hospital, 810 Takabuku Misono Watarai, Mie-ken, 516, Japan.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Stem cell factor (SCF) is known to synergize with erythropoietin (EPO) for erythropoiesis in vitro. Clonogenic assay and suspension culture were used to assess the effect of EPO alone or its combination with SCF on the proliferation and differentiation of erythroid progenitors of cord blood. Colony formation, increase in cell count, and cell cycling status for the proliferation as well as expression of Glycophorin A (Gly A) and hemoglobinization as the marker of differentiation were determined with each stimulation. The cell cycle status of the cells in suspension cultures was determined using FACScan after labeling of cells with propidium iodide. Expression of Gly A and degree of hemoglobinization were determined by FACScan and spectrophotometer on the cells plucked from colonies in semisolid culture. Larger increases in cell counts in suspension culture were observed with EPO + SCF after 12 days of inoculation than with EPO alone. Mean doubling time was 14.2 h with EPO + SCF and 22.7 h with EPO alone. The proportion of cells in S and G2 + M phase in day 14 suspension culture was 48% with EPO + SCF and 43% with EPO alone (no significant difference). Mean colony counts per 105 nonadherent mononuclear cells were 76 ± 14 with EPO + SCF and 51 ± 15 with EPO at day 14 (p < 0.05). The number of macroscopic colonies with > 0.5 mm diameter was 10.7 ± 1.2 with EPO + SCF and 0.3 ± 0.5 with EPO (p < 0.05). Percent of Gly A+ cells was 75% for both EPO + SCF and EPO colonies at day 14. Hemoglobin concentration/105 cells at day 14 was 0.70 ± 0.17 µg with EPO + SCF, and 1.16 ± 0.32 µg with EPO alone (p < 0.05). In conclusion, SCF in the combination with EPO showed a synergistic effect for erythroid proliferation in colony number as well as colony size derived from cord blood, while SCF with EPO decreased hemoglobin synthesis but not Gly A expression at day 14.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Stem cell factor (SCF) has been identified and determined to be a ligand of c-kit oncogene product [1] and has been cloned [2]. SCF has been reported to be the stimulator for pluripotent stem cells and synergizes with other cytokines in its stimulating effect [3], but this factor also appears to enhance more mature progenitor cell proliferation and differentiation [4-10]. It is still unclear how SCF exerts its function in the proliferation and differentiation of more mature progenitor cells.

Erythropoiesis is accomplished by highly complex interactions of hematopoietic progenitor cells with multiple stimulating factors in combination with erythropoietin (EPO). Erythroid progenitors gain and lose various specific features during their proliferation and differentiation. Surface antigens such as CD34, CD41 and HLA-DR disappear as erythropoiesis progresses, while other surface antigens such as CD71, CD36 and Glycophorin A (Gly A), as well as hemoglobinization, appear during maturation and acquisition of functional properties [11]. Gly A is a specific glycoprotein for erythroid cells to be expressed first on the cell surfaces of proerythroblasts [12], while hemoglobin synthesis is first observed in basophilic erythroblasts [13]. These two properties represent the differentiation and functional acquisition of erythroid cells. On the other hand, clonogenic assay and cell kinetic study are useful indicators for the proliferative condition.

For this study, we evaluated the effect of EPO + SCF versus EPO alone on the in vitro proliferation and differentiation of erythroid progenitors derived from cord blood. We investigated erythroid colony formation, cell count change in suspension culture, and cell cycle status as proliferative markers, and degree of hemoglobinization and expression of Gly A as differentiated markers.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Cell Preparation
Eight ml of umbilical cord blood samples from healthy full-term newborn neonates were collected in heparinized tubes immediately after birth. Light-density mononuclear cells (MNC) were isolated by Ficoll-Paque (Pharmacia; Uppsala, Sweden) gradient-separation at 400 x g for 30 min at room temperature. MNC were washed twice with phosphate buffer saline ([PBS] Sigma; St. Louis, MO), resuspended in 30 ml of RPMI 1640 (Sigma) with 10% fetal calf serum ([FCS] HyClone; Logan, UT) and then incubated in 75 ml culture flask at 37°C in a humidified incubator with 5% CO2 for two h. At the end of the incubation, nonadherent (NA) MNC were harvested and washed in PBS. Red cells were lysed in 0.75 M NH4Cl lysing buffer at 37°C for 5 min. Red cell lysed NAMNC were washed in PBS and resuspended at 1 x 106 cells/ml in Iscove's modified Dulbecco's medium (Sigma) with 5% FCS for colony forming unit (CFU) assay or for suspension culture.

CFU Assay
Red cell lysed NAMNC were cultured in Iscove's modified Dulbecco's medium with 0.8% of methylcellulose (Sigma), supplemented with 20% FCS, 1 U/ml of recombinant human EPO (Connaught; Swiftwater, PA), with or without 10 ng/ml of recombinant human SCF (kindly provided by Kirin Brewery; Tokyo, Japan) in 35 mm suspension culture dishes (Falcon; Franklin Lakes, NJ). The assay was performed in duplicate by plating approximately 1.0 x 105 cells/ml/dish at 37°C in a humidified incubator with 5% CO2 for 21 days. Colonies consisting of more than 20 cells were identified by inverted microscope as established colonies on days 7, 14 and 21. BFU-E and CFU-erythroid (CFU-E) are counted together as erythroid colony forming cells. Suspension culture was performed in a similar method without methylcellulose in a 96-well U bottom microculture plate (Falcon) for cell growth assay and flow cytometric assay.

Hemoglobin Concentration
Hemoglobin concentration of semisolid culture cells was detected by reaction with benzidine as described [14]. Briefly, colony forming cells on methylcellulose semisolid culture were harvested carefully by aspirating into a pipette on day 14, washed and then resuspended in PBS. Four-tenths ml of the suspension was mixed with 6 ml glacial acetic acid containing 42 mg of purified benzidine. Exactly 3.5 min after addition of 0.2 ml 3% hydrogen peroxide to the mixed solution, absorbance was detected by a spectrophotometer at 700 nm and adjusted by subtraction of the blank OD. Obtained hemoglobin concentration was calibrated on the standard curve and calculated per 1 x 105 cells.

Flow Cytometric Assay
Red cell lysed NAMNC before inoculation and harvested cells 7 or 14 days after suspension culture were resuspended in PBS with 2% bovine serum albumin (Sigma) at 1 x 106 cells/ml. The monoclonal antibodies (mAb) used in this study were Gly A (Caltag; San Francisco, CA) and CD34 (HPSC-2, Becton Dickinson; San Jose, CA) directly conjugated to fluorescein isothiocyanate. One ml of cell suspension was incubated with the manufacturer's recommended concentration of mAb at 4°C for 30 min. The cells were washed in PBS and resuspended in PBS with 2% bovine serum albumin followed by analysis with the FACScan flow cytometer (Becton Dickinson). At least 10,000 cells were analyzed. For cell cycle analysis, 0.75 ml of cell suspension in PBS was mixed with 0.25 ml of chilled (-20°C) 100% ethanol dropwise while gently voltexing and incubated at room temperature for 15 min and washed in PBS. Then, DNA in the cells was labeled by 50 µg/ml of propidium iodine (Sigma) with 1 mg/ml of RNAse A Type II (Sigma) one h before analysis. A minimum of 2,000 cells were analyzed for cell cycle study.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Proliferation of Erythroid Progenitor Cells
Cell counts in suspension culture exponentially increased from day 7 to day 16 both with EPO alone and with EPO + SCF as shown in Figure 1. During exponential growth phase, mean doubling time was 22.7 h with EPO alone and 14.2 h with EPO + SCF. The cells with EPO + SCF reached a peak at day 18, and those with EPO alone peaked at day 16. There was a significant difference in cell counts between EPO + SCF and EPO alone. They were 2x over baseline with EPO + SCF and 1x with EPO alone at day 7, and 25x and 12.5x at day 14, respectively. There was no increase with SCF alone.



View larger version (19K):
[in this window]
[in a new window]
  		Figure 1. Cell growth in suspension culture with no externally added colony stimulating factors ({square}), EPO alone (1 IU/mL)({diamond}), SCF alone (10 ng/mL) ({Delta}) or combination of SCF with EPO({bigcirc}) (mean of five experiments).

 
Mean colony number per 105 NAMNC increased up to day 14 and reached a plateau. The number of colonies was 51 ±15 with EPO alone and 76 ± 14 with EPO + SCF at day 14 (p < 0.05) (Fig. 2). The number of colonies with more than 0.5 mm of diameter (macroscopic colonies) was significantly larger with EPO + SCF than with EPO alone (10.7 ± 1.2 versus 0.3 ± 0.5/105 NAMNC, p < 0.05) (Fig. 3).



View larger version (16K):
[in this window]
[in a new window]
  		Figure 2. Number of erythroid colonies per 105 NAMNC in cord blood with EPO (1 IU/mL) ({diamond}) and EPO + SCF (10 ng/mL) ({bigcirc}).

 



View larger version (47K):
[in this window]
[in a new window]
  		Figure 3. A) The number of macroscopic erythroid colonies (see text) per 105 NAMNC in cord blood with EPO + SCF or EPO alone in semisolid culture (mean of three experiments). B) A representative photograph of the culture stimulated with EPO + SCF (left) and with EPO alone (right).

 
The proportion of cells in S and G2 + M phase in cell cycle before stimulation was only 1.0% which then increased to 31% with EPO + SCF and 23% with EPO alone in the day 7 suspension culture, and to 48% and 43% respectively at day 14 (mean of six experiments) (Fig. 4). There was no significant difference between EPO + SCF and EPO alone at either day of culture.



View larger version (12K):
[in this window]
[in a new window]
  		Figure 4. The proportion of cells in G1 , S and G2 + M phase of cell cycle at day 7 (left) and at day 14 (right) of suspension culture (n = 6).

 
Differentiation of Erythroid Progenitor Cells
Gly A+ cells in suspension culture were 4.9 ± 4.1% before stimulation. The Gly A+ cells did not increase at day 7 in any of the cultures with EPO, EPO + SCF, or without stimulators over day 0 baseline. At day 14 they increased to 75% in both EPO alone and EPO + SCF cultures as shown in Figure 5. Without stimulators, Gly A+ cells remained at the baseline value. Gly A+ cells were compared between cells cultured in suspension and cells picked from erythroid colonies that had formed in methylcellulose at day 14 of culture. The results are shown in Table 1. Virtually all cells from colonies were positive for Gly A whether they had been stimulated with EPO alone or EPO with SCF. Similarly Gly A+ cells were compared in the samples from suspension cultures whether they had been cultured with EPO alone or EPO with SCF. The lower Gly A+ cells in the suspension culture compared to cells picked from methylcellulose culture were most likely due to the presence of nonerythroid cells in the suspension culture.



View larger version (13K):
[in this window]
[in a new window]
  		Figure 5. Sequential expression of Gly A in suspension culture with EPO ({diamond}), EPO + SCF ({bigcirc}) or no externally added colony stimulating factors ({square}) (n = 6).

 

View this table:
[in this window]
[in a new window]
  		Table 1. Gly A+ cells in cells cultured with EPO alone or EPO with SCF, derived from cells in suspension culture and cells picked from methylcellulose culture
 
However, the hemoglobin concentration per 105 cells plucked from erythroid colonies at day 14 was 1.16 ± 0.32 µg with EPO alone, but only 0.7 ± 0.17 µg with EPO + SCF (p < 0.05) (Fig. 6).



View larger version (14K):
[in this window]
[in a new window]
  		Figure 6. Hemoglobin concentration per 105 cells plucked from erythroid colonies (n = 4).

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Cord blood as an alternative source of hematopoietic stem cells for bone marrow reconstitution has recently been shown to yield successful grafts to children [15]. Cord blood differs from bone marrow in immune mediating cell components [16] as well as in its hematopoietic reconstituting ability [17]. Cord blood transplantation provides several clinical advantages. These advantages include no risk to donors, less common contamination with microbiological organisms, ease of freezing and storing in a repository, and ease for a large number of registrants [18].

Our previous study demonstrated that the frequency of CFU-E was 0.05% in the MNC fraction of human cord blood, when stimulated with EPO alone (not published). This result is consistent with reported frequencies ranging from 0.0094% to 0.161% in MNC fraction, and from 0.9% to 2.08% in CD34+ cell fraction in cord blood [15, 19-25]. Since cell purification steps, culture condition and stimulating factors used varied in individual studies, it is not always possible to compare one reported result with another. The definitions of CFU-E and BFU-E are based on their function of differentiation and proliferation. Inasmuch as constant interactions occur between the progenitor cells, accessory cells and cytokines during culture, differentiation and proliferation of a progenitor cell could be enhanced or inhibited with the above variables. Furthermore, CFU-E and BFU-E are not two discretely separable progenitors. Other erythroid progenitors could be placed in between these two or proximal to BFU-E in a differentiation tree. Because of these reasons, in this study we decided to group all erythroid colonies in one category.

Many investigators have reported the effects of SCF on erythropoiesis, some using bone marrow cells [26, 27] and some using adult peripheral blood MNC [4, 28]. In this study, we evaluated responses of human cord blood cells to SCF and EPO. The major findings from our studies are: A) the number and the size of erythroid colonies are enhanced in the combination of SCF with EPO compared to EPO alone, and B) hemoglobin concentration per cell is significantly lower in EPO + SCF stimulation than in EPO alone, whereas there is no significant difference in Gly A expression of cultured cells between these two.

The increase in the size of colony by the addition of SCF to EPO suggests that cell cycle status of colony forming cells is enhanced. In suspension culture tested here, mean doubling time was 14.2 h in the combination of SCF with EPO, whereas that with EPO alone was 22.7 h. The proportion of cells in S and G2 + M phase showed no significant difference between SCF combination with EPO and EPO alone, but the absolute cell counts in S and G2 + M phase were significantly higher in EPO + SCF stimulation than in EPO alone.

Expression of Gly A by the cells cultured in suspension at day 7 and day 14 showed no significant difference between SCF + EPO and EPO alone. Edelman et al. [12] demonstrated that Gly A appeared first on proerythroblasts and continued to be expressed into mature erythrocytes. A majority of cells within the erythroid colonies in both SCF + EPO and EPO cultures in our study have morphologically matured up to or beyond proerythroblasts at day 14 and virtually every cell was positive for Gly A. Addition of SCF to EPO did not affect expression of Gly A. On the other hand, hemoglobin synthesis in the cells plucked from erythroid colonies was significantly lower in SCF combination than in EPO alone. This finding is consistent with reports of Miller et al. [6] using adult peripheral blood. It is possible that more rapid proliferation of cells stimulated by EPO + SCF compared to EPO alone may result in nutrient deficiency and less hemoglobinization. However, Miller et al. reported that addition of transferrin to culture media did not result in an increase in hemoglobin synthesis, suggesting that deficiency of iron was not the reason for the lack of increase in hemoglobinization [6]. Karhi et al. [13] reported that hemoglobin synthesis occurred first in the basophilic erythroblasts. If this is the case, our findings suggest that SCF may delay maturation of erythroid cells beyond basophilic erythroblasts. Miller et al. [6] compared total hemoglobin accumulation per cell between the cultures with EPO + SCF and with EPO alone at days 10, 14 and 18. During this period, the hemoglobin accumulation was always higher with EPO alone than with EPO + SCF. The difference in hemoglobin accumulation was the least at day 14 and at a maximum at day 18. The same authors [5] demonstrated decreased expression of ß-globin mRNA in the erythroid cells cultured with SCF + EPO compared to cultures with EPO alone. These observations support that the decrease in the hemoglobin concentration may be due to inhibition of maturation rather than maturation delay. These investigations were, however, done on the adult peripheral blood in patients with sickle cell disease and SCF concentration of 100 ng/ml compared to 10 ng/ml in our study. Therefore, their results may not be directly applicable to our system. Nonetheless, the reports that SCF enhanced proliferation but inhibited differentiation of human erythroleukemia cell lines [8, 9, 29] support this hypothesis. Thus it is possible that SCF suppresses expression of hemoglobin synthetic enzyme gene, while it does not affect the expression of Gly A in erythropoiesis in human cord blood. However, further studies to clarify signal transduction after binding to SCF receptor, and functional roles of subsequent protein products will be required to obtain more insights into the synergistic effects in the combination of SCF with EPO.

Other investigators showed that when compared to stimulation with each growth factor alone, SCF in combination with other growth factors synergistically increased the number and size of colonies derived from CFU-granulocyte/erythroid/macrophage/megakaryocyte, BFU-E [4], and CFU-granulocyte/macrophage [30]. On the other hand, Miller et al. [5] showed that SCF failed to increase the number of colonies derived from BFU-E in adult peripheral blood in combination with EPO compared to EPO alone. In selected experiments, we made preliminary observations that the addition of SCF to EPO resulted in an increase in number of CFU-E but not of BFU-E (data not shown). Thus our result is consistent with Miller's report. The difference between our results and those of others indicating that SCF synergistically increases BFU-E may be due to biological differences in hematopoietic stem cells between cord blood and adult peripheral blood on which many investigators documented the SCF effects. Alternatively, it may be due to the difference in purity of prepared cells, concentration of cytokines or colony growth factors used, or other culture conditions including presence or absence of FCS. In this regard it is interesting to note that Sawada et al. [31] reported that 100% of CFU-E but only 20% of BFU-E express EPO receptor. Thus it is possible that BFU-E that do not respond to EPO alone may be recruited by SCF to become EPO responsive and form CFU-E colonies. This would explain the observation that addition of SCF increased the number of CFU-E-derived colonies but not BFU-E-derived colonies.

We conclude that synergistic effects of SCF to EPO increase proliferation of erythroid progenitor cells in cord blood compared to EPO alone and decrease hemoglobin synthesis but not Gly A expression at day 14.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Chabot B, Stephenson DA, Chapman VM et al. The proto-oncogene c-kit encoding a transmembrane tyrosine kinase receptor maps to the mouse W locus. Nature 1988;335:88-89.[Medline]

  2. Martin FH, Suggs SV, Langley KE et al. Primary structure and functional expression of rat and human stem cell factor DNAs. Cell 1990;63:203-211.[Medline]

  3. Bernstein ID, Andrews RG, Zsebo KM. Recombinant human stem cell factor enhances the formation of colonies by CD34+ and CD34+ lin– cells, and the generation of colony-forming cell progeny from CD34+ lin– cell cultured with interleukin-3, granulocyte colony-stimulating factor, or granulocyte-macrophage colony-stimulating factor. Blood 1991;77:2316-2321.[Abstract/Free Full Text]

  4. Dai CH, Krantz SB, Zsebo KM. Human burst-forming units-erythroid need direct interaction with stem cell factor for further development. Blood 1991;78:2493-2497.[Abstract/Free Full Text]

  5. Miller BA, Floros J, Cheung JY et al. Steel factor affects SCL expression during normal erythroid differentiation. Blood 1994;84:2971-2976.[Abstract/Free Full Text]

  6. Miller BA, Perrine SP, Bernstein A et al. Influence of steel factor on hemoglobin synthesis in sickle cell disease. Blood 1992;79:1861-1868.[Abstract/Free Full Text]

  7. Muta K, Krantz SB, Bondurant MC et al. Distinct roles of erythropoietin, insulin-like growth factor I, and stem cell factor in the development of erythroid progenitor cells. J Clin Invest 1994;94:34-43.

  8. Ogawa K, Tashima M, Toi T et al. Inhibition of erythroid differentiation by stem cell factor in K562 cells expressing the c-kit gene. Exp Hematol 1992;22:45-51.

  9. Broudy NC, Morgan DA, Lin N et al. Stem cell factor influences the proliferation and erythroid differentiation of the MB-02 human erythroleukemia cell line by binding to a high-affinity c-kit receptor. Blood 1993;82:436-444.[Abstract/Free Full Text]

  10. Schibler KR, Ohls RK, Le T et al. Effect of recombinant stem cell factor on clonogenic maturation and cell cycle status of human fetal hematopoietic progenitors. Pediatr Res 1994;35:303-306.[Medline]

  11. Okumura N, Tsuji K, Nakahata T. Changes in cell surface antigen expressions during proliferation and differentiation of human erythroid progenitors. Blood 1992;80:642-650.[Abstract/Free Full Text]

  12. Edelman P, Vinci G, Villeval JL et al. A monoclonal antibody against an erythrocyte ontogenic antigen identifies fetal and adult erythroid progenitors. Blood 1986;67:56-63.[Abstract/Free Full Text]

  13. Karhi KK, Andersson LC, Voupio P et al. Expression of blood group A antigen in human bone marrow cells. Blood 1981;57:147-151.[Abstract/Free Full Text]

  14. Bauer JD, Ackermann P, Gelson T, ed. Clinical Laboratory Method. St. Louis: Mosby Co., 1974:139-142.

  15. Gluckman E, Broxmeyer HE, Auerbach AD et al. Hematopoietic reconstitution in a patient with Fanconi's anemia by means of umbilical-cord blood from an HLA-identical sibling. N Engl J Med 1989;321:1174-1178.[Medline]

  16. Harris DT. In vitro and in vivo assessment of the graft-versus-leukemia activity of cord blood. Bone Marrow Transplant 1995;15:17-23.[Medline]

  17. Pettengell R, Luft T, Henschler R et al. Direct comparison by limiting dilution analysis of long-term culture-initiating cells in human bone marrow, umbilical cord blood, and blood stem cells. Blood 1994;84:3653-3659.[Abstract/Free Full Text]

  18. Rubintein P, Rosenfield RE, Adamson JW et al. Stored placental blood for unrelated bone marrow reconstitution. Blood 1993;81:1679-1690.[Free Full Text]

  19. Lu L, Xiao M, Shen R et al. Enrichment, characterization, and responsiveness of single primitive CD34+++ human umbilical cord blood hematopoietic progenitors with high proliferation and replating potential. Blood 1993;81:41-48.[Abstract/Free Full Text]

  20. Abboud M, Xu F, LaVia M et al. Study of early hematopoietic precursors in human cord blood. Exp Hematol 1992;29:1043-1047.

  21. Caux C, Favre C, Saeland S et al. Sequential loss of CD34 and class II MHC antigens on purified cord blood hematopoietic progenitors cultured with IL-3: characterization of CD3–, HLA-DR+ cells. Blood 1989;74:1287-1294.[Abstract/Free Full Text]

  22. Thierry D, Hervatin F, Traineau R et al. Hematopoietic progenitor cells in cord blood. Bone Marrow Transplant 1992;9:101-104.

  23. Forestier F, Daffos F, Catherine N et al. Developmental hematopoiesis in normal human fetal blood. Blood 1991;77:2360-2363.[Abstract/Free Full Text]

  24. Newton I, Charbord P, Schaal JP et al. Toward cord blood banking: density-separation and cryopreservation of cord blood progenitors. Exp Hematol 1993;21:671-674.[Medline]

  25. Migliaccio AR, Baiocchi M, Durand B et al. Aspects of the biology of the neonatal hematopoietic stem cell. STEM CELLS 1993;11:56-64.[Abstract]

  26. Alter BP, Knoblock ME, He L et al. Effect of stem cell factor on in vitro erythropoiesis in patients with bone marrow failure syndromes. Blood 1992;80:3000-3008.[Abstract/Free Full Text]

  27. Tsuji K, Zsebo KM, Ogawa M. Enhancement of murine blast cell colony formation in culture by recombinant rat stem cell factor, ligand for c-kit. Blood 1991;78:1223-1229.[Abstract/Free Full Text]

  28. Papayannopoulou T, Brice M, Blau A. Kit ligand in synergy with interleukin-3 amplifies the erythropoietin-dependent, globin-synthesizing progeny of normal human burst-forming units-erythroid in suspension cultures: physiologic implications. Blood 1993;81:299-310.[Abstract/Free Full Text]

  29. Nicolis S, Ottolenghi S, Papayannopoulou T et al. Dependence for the proliferation response to erythropoietin on an established erythroid differentiation program in a human hematopoietic cell line, UT-7. Exp Hematol 1993;21:665-670.[Medline]

  30. Broxmeyer HE, Cooper S, Lu L et al. Effect of murine mast cell growth factor (c-kit proto-oncogene ligand) on colony formation by human marrow hematopoietic progenitor cells. Blood 1991;77:2142-2149.[Abstract/Free Full Text]

  31. Sawada K, Krantz SB, Dai CH et al. Purification of human blood burst-forming unit-erythroid and demonstration of the evolution of erythropoietin receptors. J Cell Physiol 1990;142:219-230.[Medline]

accepted for publication March 19, 1997.




This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Reprints/Permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Sakatoku, H.
Right arrow Articles by Inoue, S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Sakatoku, H.
Right arrow Articles by Inoue, S.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
STEM CELLS THE ONCOLOGIST CME ALPHAMED PRESS JOURNALS
http://www.stemcellsportal.com/