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 HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Dravid, G.
Right arrow Articles by Rao, S.G.A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Dravid, G.
Right arrow Articles by Rao, S.G.A.
Stem Cells 2002;20:183-189 www.StemCells.com
© 2002 AlphaMed Press

Ex Vivo Expansion of Stem Cells from Umbilical Cord Blood: Expression of Cell Adhesion Molecules

G. Dravid, S.G.A. Rao

Chemotherapy and Stem Cell Biology Division, Cancer Research Institute, Tata Memorial Centre, Parel, Mumbai, India

Key Words. Cord blood • CD34+ cells • Expansion • Cell adhesion molecules • CAMs

S.G.A. Rao, Ph.D., Reliance Life Sciences, Sir H.N. Hospital, PG Chowk, RajaRam Mohan Roy Road, Mumbai – 400 004, India. Telephone: 91-22-3810707 ext. 503; Fax: 91-22-3889390; e-mail: sgarao{at}vsnl.net


   ABSTRACT
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Expansion of stem cells from cord blood has been demonstrated to increase the numbers of CD34+ cells, CD34+ subsets, long-term culture-initiating cells, and severe combined immunodeficient mouse, repopulating cells. However, reports suggest that the ex vivo expanded population behaves differently than freshly isolated cells and shows a delayed or diminished engraftment. In this study, we investigated the effects of the cytokines flt3 ligand, stem cell factor, and thrombopoietin on expansion of CD34+ and CD34+/CD38- cells. In addition, we studied the expression of adhesion molecules, very late activation antigen-4 (VLA-4) and leukocyte function antigen-1 (LFA-1), on CD34+ cells from cord blood by flow cytometry. We also looked at the expression of an adhesion receptor, namely, vascular cell adhesion molecule-1 (VCAM-1) on bone marrow stromal cells by Western blot analysis after exposure to low dose {gamma} irradiation. After culturing for 7 days, increases in the absolute numbers of CD34+, CD34+/CD38-, CD34+/VLA-4+, and CD34+/LFA-1+ cells were 5.67 ± 2.91 (mean ± standard deviation) fold, 7.21 ± 4.38 fold, 99.56 ± 101.5 fold, and 101.39 ± 83.25 fold, respectively. There was a transient upregulation in the expression levels of VCAM-1 on stromal cells, which peaked at 4 hours. Though there was an increase in the absolute numbers of CD34+ cells expressing the adhesion molecules, the expression levels (antigen density) of the adhesion molecules on the CD34+ cells remained unaffected.


   INTRODUCTION
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Umbilical cord blood (UCB) has gained tremendous importance over the last decade as a potential source of transplantable stem cells. It is easily available and has been shown to contain a large number of hematopoietic progenitor cells [1]. So far, more than 2,000 UCB transplants have been done worldwide. Though the majority of recipients belong to the pediatric group, successful transplants in adults have also been reported. Expansion has been suggested as a means of obtaining larger cell numbers to improve outcomes in patients with higher body weight [2]. Expansion should ideally lead to cell populations, which would reduce long periods of neutropenia and thrombocytopenia associated with UCB transplants. Expansion in the presence of cytokines also facilitates introduction of therapeutic genes for treatment of genetic disorders. CD34+ cells from UCB have been expanded under different culture conditions, namely, in liquid cultures in the presence of recombinant cytokines [3], on stromal support [4–7], or in stroma noncontact cultures [8, 9]. Results have indicated that expansion of CD34+ cells, CD34+/CD38- cells, and long-term culture-initiating cells is achievable [3] and that these cells are capable of engraftment as demonstrated in a nonobese diabetic/combined immunodeficient (NOD/SCID) mouse model [10]. However, certain studies have expressed concern regarding the behavior of ex vivo expanded populations, in particular, in their engraftment capacity [11, 12]. We have investigated whether ex vivo expansion of CD34+ cells in the presence of recombinant cytokines affects the expression of the adhesion molecules very late activation antigen-4 (VLA-4) and leukocyte function antigen-1 (LFA-1). These molecules are known to be important in the interaction of stem cells with bone marrow (BM) stroma. We hypothesized that downmodulation of such molecules may be the reason for poor or delayed homing of the transplanted cells. We have also studied the effect of irradiation on the adhesion receptors on BM stroma, since these interactions play a crucial role in the homing of stem cells that are transplanted.


   MATERIALS AND METHODS
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Cell Separation
UCB was collected in sterile 100-ml glass bottles containing citrate phosphate dextrose adenine (CPDA) as an anticoagulant, from normal full-term deliveries from Wadia Maternity Hospital, Parel, Mumbai. Informed consent was obtained in all cases. The volume of blood collected ranged from 45-70 ml. The majority of RBCs was depleted by a 3% dextran sedimentation method [13]. The leukocyte-rich fraction was washed with Ca2+- and Mg2+-free phosphate buffered saline (PBS) to remove the dextran and then loaded on Histopaque®-1077 (Sigma; St. Louis, MO; http://www.sigmaaldrich.com) (density = 1.077 g/ml). Cells were centrifuged at 400 g for 30 minutes at room temperature. The mononuclear cells (MNCs) at the interface were washed with PBS and resuspended in PBS containing CPDA. Viability was determined by trypan blue dye exclusion method.

CD34 Cell Purification
CD34+ cells were separated using the magnetic cell sorting (MACS) system (Miltenyi Biotech; Bergisch Gladbach, Germany; http://www.miltenyibiotec.com) according to the manufacturer's instructions with minor modifications. Briefly, 100 x 106 MNCs were incubated with CD34 microbeads for 30 minutes at 4°C in MACS buffer. The positive fraction was obtained, and the viability determined by trypan blue dye exclusion method. Percent purity of the positive fraction was determined using anti-CD34 phycoerythrin (PE)-tagged antibody (clone 581; Pharmingen; San Diego, CA; http://www.pharmingen.com).

Expansion in Liquid Cultures
For expansion, 10,000 CD34+ cells/ml were cultured in 60-mm petri dishes (Tarsons; Kolkata, West Bengal, India; http://www.tarsonsproducts.com/frame.htm) in serum-free medium (SFM) (Stem Pro CD34; GIBCO BRL; Grand Island, NY; http://www.invitrogen.com) containing flt3 ligand (FL) at 50 ng/ml, thrombopoietin (TPO) at 25 ng/ml, and stem cell factor (SCF) at 10 ng/ml. FL and TPO were from PeproTech USA (Rocky Hill, NJ; http://www.peprotech.com) while SCF was from Roche Biochemicals (Mannheim, Germany; http://www.biochem.roche.com). Cells were incubated at 37°C with 5% CO2 for 7 days. Cells were harvested at day 7, counted, and used for flow cytometry.

Flow Cytometric Analysis
Flow cytometry was done on a FACSCalibur (Becton Dickinson [BD]; San Jose, CA; http://www.bd.com) equipped with an argon laser emitting at 488 nm. The monoclonal antibodies used were anti-CD34 PE (Pharmingen), anti-CD38 fluorescein isothiocyanate (FITC) (Pharmingen), anti-VLA-4 FITC, and anti-LFA-1 FITC; the latter two were both from Immunotech (Marseille, France). Relevant isotype control antibodies were also used. Ten thousand events were acquired. Analysis was done using Cell Quest software (BD).

Establishment of Stroma
Stroma was established according to the method described by Gartner and Kaplan [14] with minor modifications. Briefly, BM was obtained from resected ribs from patients undergoing cardiac surgery at the CardioVascular Thoracic Centre, Mumbai or from patients undergoing lung surgery at Tata Memorial Hospital, Mumbai. Informed consent was obtained in all cases. The BM cells were resuspended in Iscove's modified Dulbecco's medium containing 10% fetal bovine serum, 10% horse serum, 10-6 M hydrocortisone 21-hemisuccinate Na-salt (Sigma), and the antibiotics penicillin, at 200 IU/ml, and streptomycin, at 250 µm/ml. Cells were passed through Falcon (Franklin Lakes, NJ) cell strainers (70 µm), and 2 x 106 nucleated cells/ml were plated in 24-well plates (Corning; New York, NY; http://www.corning.com). Cultures were incubated at 37°C with 5% CO2. Cultures were demi-depopulated weekly and fresh medium was added. Four-week-old stromal cultures were used for all experiments.

Irradiation of Stroma
Four-week-old stroma was washed five times with PBS to remove spent medium and serum. Fresh medium was added and the stroma was uniformly irradiated with 2 Gy {gamma} irradiation from a Theratron 780-C. At 4- and 24-hour time points, the stroma was subjected to protein extraction. Unirradiated control was also maintained.

Extraction of Protein
Stroma was washed five times with chilled PBS to remove serum proteins. Chilled saline-EDTA was added, and the plates were placed on a rocker to facilitate detachment of the stroma. The proteins were extracted in radioimmunoprotection assay buffer (NaCl, Tris-Cl, Triton X-100, SDS, Na-deoxycholate, EGTA, MnCl2, phenylmethylsulfonyl fluoride, Leupeptin, and Aprotinin). Extraction of protein was facilitated by sonication (Bronwill; Rochester, NY). The extract was ultracentrifuged at 100,000 rpm in a tabletop ultracentrifuge (Beckman; Palo Alto, CA; http://www.coulter.com). The supernatant was stored at -20°C.

SDS PAGE and Western Blotting
After protein estimation, 100 µg of protein were subjected to SDS PAGE on a 7.5% resolving gel. Proteins were electrophoresed at 30 mA constant current until the indicator dye reached the end of the gel. The proteins were transferred to polyvinyl difluoride membrane at 4°C at 30 mA constant current for 14 hours in a Transblot apparatus (Technosource; Mumbai, India). The efficiency of blotting was determined by Ponceau-S (Sigma).

Immunodetection
Blots were blocked overnight at 4°C with 5% skimmed milk powder and then incubated with anti-vascular cell adhesion molecule-1 (VCAM-1) antibody raised in rabbit (Santa Cruz Biotech; Santa Cruz, CA; http://www.scbt.com) (1:200 dilution). Secondary antibody used was donkey anti-rabbit tagged with horseradish peroxidase (Amersham; Little Chalfont, Buckinghamshire, UK; http://www.apbiotech.com) (1:10,000 dilution). Detection of bands was done by using the enhanced chemiluminescence-plus (ECL+) reagents (Amersham). Blots were exposed to Hyperfilm-ECL (Amersham).

Statistical Analysis
Statistical analysis was done by using the Student's t-test. p values less than 0.05 were considered to be significant.


   RESULTS
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Adhesion Molecule Expression of Stem Cells
MACS separation of CD34+ cells led to a purity ranging from 89%-96% (n = 8) while no loss of CD34 was observed in the negative fraction (data not shown). The expression of VLA-4 and LFA-1 on CD34+ cells on day 0 is shown in Figure 1Go. From 15%-27% of the CD34+ cells expressed the two adhesion molecules on day 0, as determined by dual-color flow cytometric analysis. A large percentage of CD34+ cells did not express the CD38 antigen, reminiscent of a primitive stem cell population. The expression of the adhesion molecules and CD38 after expansion for 7 days in SFM is depicted in Figure 2Go. It is evident that there is a loss of CD34 antigen on cells after expansion. On day 7, cells were dual labeled with CD34 PE and VLA-4 FITC or LFA-1 FITC and analyzed on a FACSCalibur. The results are shown in Figure 2Go. There was no increase or decrease in the antigen density (in terms of the mean fluorescence intensity) of the two adhesion molecules on the CD34+ cells. The percentages of different subsets measured by flow cytometry were multiplied by the total nucleated cells obtained on day 7 to get the absolute numbers of the different cell subsets. The increases in the absolute numbers of CD34+, CD34+/VLA-4+, CD34+/LFA-1+, and CD34+/CD38- cells and the relative fold expansions are shown in Table 1Go.



View larger version (28K):
[in this window]
[in a new window]
  		Figure 1. Flow cytometric analysis of MACS-separated CD34+ cells stained with CD34 PE and VLA-4 FITC or LFA-1 FITC before expansion. From 15%-27% of cells that were CD34+ were also positive for the expression of VLA-4 and LFA-1 (D and F) (upper right quadrant). A substantial number of CD34+ cells did not show expression of CD38 antigen (G), indicating a primitive stem cell population. The side scatter versus adhesion molecule expression is also shown in the total population (C and E).

 


View larger version (30K):
[in this window]
[in a new window]
  		Figure 2. Flow cytometric analysis of MACS-separated CD34+ cells stained with CD34 PE and VLA-4 FITC or LFA-1 FITC after expansion in SFM in the presence of FL, TPO, and SCF. There was a decrease in the percentage of CD34+ cells indicating the loss of CD34 antigen. No change was observed in the antigen density of VLA-4 or LFA-1 on the CD34+ cells (D and F). A loss of CD34+ / CD38+ population is evident by the probable downmodulation of CD38 antigen after expansion (G). The side scatter versus adhesion molecule expression is shown also for the total expanded population (C and E).

 

View this table:
[in this window]
[in a new window]
  		Table 1. Absolute counts of different cell populations before and after expansion of MACS-separated CD34+ cells from UCB in SFM in the presence of FL, TPO, and SCF in static liquid cultures. The fold expansion of different cell subsets is indicated.
 
Adhesion Receptors on Stromal Cells
The expression of VCAM-1 at 4 and 24 hours postirradiation compared with the unirradiated control (UC) is shown in Figure 3Go. There was a transient upregulation in the expression of VCAM-1 at 4 hours postirradiation that decreased by 24 hours.



View larger version (47K):
[in this window]
[in a new window]
  		Figure 3. Expression of VCAM-1 on 4-week-old stroma at 4- and 24-hour time points after irradiation with 2 Gy. There was an upregulation of VCAM-1 seen at 4 hours compared with the unirradiated control (UC), which decreased by 24 hours.

 

   DISCUSSION
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Expansion of CD34+ cells and other cell subtypes has been widely documented. However, the engraftment capacity of the expanded cells, as defined in NOD/SCID repopulation assays, does not show unequivocal results. There seems to be some delay in the engraftment characteristics of the ex vivo-expanded cells [12]. This is important, since early engraftment of stem cells is necessary for reconstitution of hematopoiesis. Therefore, expansion protocols should in no way jeopardize the engraftment potential. Since cell adhesion molecules, such as VLA-4 and LFA-1, are important in adhesion of CD34+ cells to the BM, their status was investigated to determine if ex vivo expansion in some way affected their levels. These adhesion molecules may be important in the homing of the transplanted stem cells to the recipient marrow. VLA-4, LFA-1, and E-cadherin have been described to be present on CD34+ cells from UCB and BM [15–17] and are known to be involved in the adhesion of CD34+ cells to the BM stroma [17, 18]. Saeland et al. and Timeus et al. indicated that 100% of CD34+ cells express both VLA-4 and LFA-1, an observation never seen by us. We did, however, find a 99.56 ± 101.5-fold expansion of CD34+/VLA-4+ cells and a 101.39 ± 83.25-fold expansion of CD34+/LFA-1+ cells after culturing for 7 days. There was a large variation in the expression of both VLA-4 and LFA-1 (15%-27%) on CD34+ cells among the cord blood samples. The same was evident at the end of the expansion period. This resulted in a high standard deviation, which can be seen in the results. There was no increase or decrease in the antigen density of these molecules on the CD34+ cell population after expansion. An upregulation of LFA-1 on CD34+ cells from UCB after 6-12 days of culture in presence of interleukin-3 (IL-3) alone has been documented [15]. The same authors did not find any difference in VLA-4 expression. The combined effects of FL, TPO, and SCF on the expression levels of the adhesion molecules VLA-4 and LFA-1 have not previously been studied. Our results suggest that expansion does not seem to affect the expression levels of these adhesion molecules on CD34+ cells. SCF has been implicated in modulating the avidity but not the density of VLA-4 on the hematopoietic cell line Mo7E [19]. In our study, there was also a 7.21 ± 4.38-fold expansion of CD34+/CD38- cells, indicating expansion of a primitive stem cell pool. This was probably due to downmodulation of CD38 antigen expression while still retaining the CD34 antigen (Fig. 2Go). Such a downmodulation of CD38 antigen has been described before [11, 20]. The reason for such a downmodulation is unclear at present.

Since total body irradiation is used as a myeloablative regimen [21], we wanted to determine if irradiation had any effect on the expression of adhesion receptors on stromal cells. This, in turn, could affect the homing of the cells that are pushed in as a graft. VCAM-1, which is the ligand for VLA-4, has been described on vascular endothelial cells after treatment with inflammatory cytokines like tumor necrosis factor-{alpha} (TNF-{alpha}) and IL-4 at a 4-hour timepoint [18, 22]. We saw a similar increase in VCAM-1 after low-dose {gamma} irradiation. VCAM-1 is also expressed on several nonvascular cell types, such as tissue macrophages, dendritic cells, and fibroblastic elements within the BM [22–24]. Increased expression of VCAM-1 has been described on sinusoidal epithelium 2 days after irradiation in an in vivo study [25]. The in vivo increase in VCAM-1 expression has been attributed to an indirect effect of TNF-{alpha}. This is important, since reports have shown that there is an increase in the levels of TNF-{alpha} in the serum of patients undergoing radiotherapy [26]. If levels of expression of particular adhesion receptors following irradiation are transient, as seen by us, then the expression levels when the transplanted cells actually reach the marrow may dictate the extent of homing of the stem cells. Whether this would translate into better and faster engraftment remains to be answered. We conclude that the delay or poor engraftment that has been documented is not due to downmodulation of adhesion molecules (VLA-4 and LFA-1) on stem cells following expansion. Though expression levels are not affected, the fact remains that, following transplantation, the cytokines, both membrane bound and secreted, which are elaborated in the stromal microenvironment, in coordination with accessory cells or extracellular matrix, might locally regulate the function of adhesion molecules by affecting their avidity state. Designing protocols to achieve true expansion of stem cells requires a better understanding of the manner in which stem cells are regulated in coordination with the surrounding microenvironment and the way they respond to the growth signals that are elaborated within the stromal niche [27]. More work is warranted, which is currently being pursued in our lab to understand the complex process of homing and engraftment


   ACKNOWLEDGMENT
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 
We would like to thank the Lady Tata Memorial Trust for its financial support and Ms. Prachi Gokhale for the flow cytometry work.


   REFERENCES
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Broxmeyer HE, Douglas GW, Hangoc G et al. Human umbilical cord blood as a potential source of transplantable hematopoeitic stem/progenitor cells. Proc Natl Acad Sci USA 1989;86:3828–3832.[Abstract/Free Full Text]

  2. Broxmeyer HE, Hangoc GC, Cooper S et al. Growth characteristics and expansion of human umbilical cord blood and estimation of its potential for transplantation in adults. Proc Natl Acad Sci USA 1992;89:4109–4113.[Abstract/Free Full Text]

  3. Piacibello W, Sanavio F, Garetto L et al. Extensive amplification and self-renewal of human primitive hematopoietic stem cells from cord blood. Blood 1997;89:2644–2653.[Abstract/Free Full Text]

  4. Brandt JE, Galy AHM, Leuns KM et al. Bone marrow repopulation by human marrow stem cells after long-term expansion culture on porcine endothelial cell line. Exp Hematol 1998;26:950–961.[Medline]

  5. Kanai M, Hirayama F, Yamaguchi M et al. Stromal cell-dependent ex vivo expansion of human cord blood progenitors and augmentation of transplantable stem cell activity. Bone Marrow Transplant 2000;26:837–844.[CrossRef][Medline]

  6. Kawada H, Ando K, Tsuji T et al. Rapid ex vivo expansion of human umbilical cord hematopoietic progenitors using a novel culture system. Exp Hematol 1999;27:904–915.[CrossRef][Medline]

  7. Köhler T, Plettig R, Wetzstein W et al. Defining optimum conditions for the ex vivo expansion of human umbilical cord blood cells. Influences of progenitor enrichment, interference with feeder layers, early-acting cytokines and agitation of culture vessels. STEM CELLS 1999;17:19–24.[Abstract/Free Full Text]

  8. Prosper F, Vanoverbeke K, Stroncek D et al. Primitive long-term culture-initiating cells (LTC-ICs) in the granulocyte colony-stimulating factor mobilized peripheral blood progenitor cells have similar potential for ex vivo expansion as primitive LTC-ICs in steady state bone marrow. Blood 1997;89:3991–3997.[Abstract/Free Full Text]

  9. Verfaillie CM. Direct contact between human primitive hematopoietic progenitors and bone marrow stroma is not required for long-term in vitro hematopoiesis. Blood 1992;79:2821–2826.[Abstract/Free Full Text]

  10. Piacibello W, Sanavio F, Severino A et al. Engraftment in nonobese diabetic severe combined immunodeficient mice of human CD34+ cord blood cells after ex vivo expansion: evidence for the amplification and self-renewal of repopulating stem cells. Blood 1999;93:3736–3749.[Abstract/Free Full Text]

  11. Dorrell C, Gan OI, Pereira DS et al. Expansion of human cord blood CD34+CD38- cells in ex vivo culture during retroviral transduction without a corresponding increase in SCID repopulating cell (SRC) frequency: dissociation of SRC phenotype and function. Blood 2000;95:102–110.[Abstract/Free Full Text]

  12. Guenechea G, Segovia JC, Albella B et al. Delayed engraftment of nonobese diabetic/severe combined immunodeficient mice transplanted with ex vivo expanded human CD34+ cord blood cells. Blood 1999;93:1097–1105.[Abstract/Free Full Text]

  13. Tanavde VM, Desai SS, Rao SGA. Erythrocyte depletion of human umbilical cord blood using dextran sedimentation. Indian J Med Res 1997;106:16–19.[Medline]

  14. Gartner S, Kaplan HS. Long-term culture of human bone marrow cells. Proc Natl Acad Sci USA 1980;77:4756–4759.[Abstract/Free Full Text]

  15. Saeland S, Duvert V, Caux C. Distribution of surface-membrane molecules on bone marrow and cord blood CD34+ hematopoietic cells. Exp Hematol 1992;20:24–33.[Medline]

  16. Timeus F, Crescenzio N, Basso G et al. Cell adhesion molecule expression in cord blood CD34+ cells. STEM CELLS 1998;16:120–126.[Abstract/Free Full Text]

  17. Turel KR, Rao SGA. Expression of the cell adhesion molecule E-cadherin by the human bone marrow stromal cells and its probable role in CD34+ stem cell adhesion. Cell Biol Int 1998;22:641–648.[CrossRef][Medline]

  18. Teixido J, Hemler ME, Greenberger JS et al. Role of ß1 and ß2 integrins in the adhesion of human CD34hi stem cells to bone marrow stroma. J Clin Invest 1992;90:358–367.

  19. Kovach NL, Lin N, Yednock T et al. Stem cell factor modulates avidity of {alpha}4ß1 and {alpha}5ß1 integrins expressed on hematopoietic cell lines. Blood 1995;85:159–167.[Abstract/Free Full Text]

  20. Reems JA, Torok-Storb B. Cell cycle and functional differences between CD34+/CD38hi and CD34+/CD38lo human marrow cells after in vitro cytokine exposure. Blood 1995;85:1480–1487.[Abstract/Free Full Text]

  21. Chao NJ, Snyder DS, Jain M et al. Equivalence of 2 effective graft-versus-host disease prophylaxis regimens: results of a prospective double-blind randomized trial. Biol Blood Bone Marrow Transplant 2000;6:254–261.[CrossRef][Medline]

  22. Simmons PJ, Masinovsky B, Longenecker BM et al. Vascular cell adhesion molecule-1 expressed by bone marrow stromal cells mediates the binding of hematopoietic progenitor cells. Blood 1992;80:388–395.[Abstract/Free Full Text]

  23. Rice GE, Munro JM, Corless C et al. Vascular and nonvascular expression of INCAM-110. A target for mononuclear leukocyte adhesion in normal and inflamed human tissues. Am J Pathol 1991;138:385–393.[Abstract]

  24. Freedman AS, Munro JH, Rice GE et al. Adhesion of human B cells to germinal centres in vitro involves VLA-4 and INCAM-110. Science 1990;249:788–795.

  25. Jacobsen K, Kravitz J, Kincade PW et al. Adhesion receptors on bone marrow stromal cells: in vivo expression of vascular cell adhesion molecule-1 by reticular cells and sinusoidal endothelium in normal and {gamma}-irradiated mice. Blood 1996;87:73–82.[Abstract/Free Full Text]

  26. Girinsky TA, Pallardy M, Comoy E et al. Peripheral blood corticotropin-releasing factor, adrenocorticotropic hormone and cytokine (interleukin beta, interleukin 6, tumor necrosis factor alpha) levels after high- and low-dose total-body irradiation in humans. Radiat Res 1994;139:360–363.[Medline]

  27. Rao SGA, Dravid G. Expansion of haematopoietic stem cells in-vitro: a challenge to stem cell biologists. Indian J Exp Biol 1999;37:1051–1052.[Medline]

Received November 21, 2001; accepted for publication January 23, 2002.



This article has been cited by other articles:


Home page
 Stem CellsHome page
P. Denning-Kendall, S. Singha, B. Bradley, and J. Hows
Cytokine Expansion Culture of Cord Blood CD34+ Cells Induces Marked and Sustained Changes in Adhesion Receptor and CXCR4 Expressions
Stem Cells, January 1, 2003; 21(1): 61 - 70.
[Abstract] [Full Text] [PDF]

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 HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Dravid, G.
Right arrow Articles by Rao, S.G.A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Dravid, G.
Right arrow Articles by Rao, S.G.A.

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