Contact with fibronectin enhances preservation of normal but not chronic myelogenous leukemia primitive hematopoietic progenitors.
OBJECTIVE
Coculture with stromal cells enhances preservation and self-renewal of primitive progenitor potential in hematopoietic cells during ex vivo culture with growth factors (GF). However, the respective roles of growth factors, stromal contact, and extracellular matrix (ECM) ligands in this effect are not clear. Here we investigated the role of direct contact with stroma and the ECM protein fibronectin (FN) in these effects, and investigated whether abnormal integrin receptor function in chronic myelogenous leukemia (CML) progenitors was associated with perturbation in these responses.


METHODS
Normal bone marrow CD34+ cells were cultured in GF-containing medium with or without contact with stromal layers, glutaraldehyde-fixed stromal layers (stroma-contact), or integrin-binding FN fragments for 7 days. Progeny cells were assayed for primitive progenitors in week-6 long-term culture-initiating cell (LTC-IC) and week-10 extended LTC-IC (ELTC-IC) assays.


RESULTS
Increased LTC-IC and ELTC-IC preservation was seen following coculture with stroma, and was also observed after culture in contact with fixed stromal layers and FN. Both alpha4beta1 and alpha5beta1-integrin binding FN fragments enhanced LTC-IC preservation. Analysis of single CD34+CD38- cells showed that coculture with FN resulted in significantly reduced cell division, but enhanced retention of LTC-IC capacity in divided cells. FN also increased LTC-IC frequency in undivided cells. CML progenitors demonstrate deficient integrin-mediated adhesion, migration, and signaling. Coculture of CML CD34+ cells with stroma and FN failed to enhance LTC-IC preservation.


CONCLUSIONS
We conclude that beta1 integrin-FN interactions enhance normal primitive progenitor preservation with or without cell division, and that these mechanisms are impaired in CML primitive progenitors.
Bhatia
Ravi
R
Division of Hematology and Bone Marrow Transplantation, City of Hope National Medical Center, 1500 E Duarte Road, Duarte, CA 91010, USA. rbhatia@coh.org
Williams
Andrea D
AD
Munthe
Heidi A
HA
D016022:Case-Control Studies; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D018920:Coculture Techniques; D005353:Fibronectins / Q000378:metabolism / Q000494:pharmacology*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D039041:Integrin alpha4beta1; D016023:Integrins / Q000378:metabolism; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology*; D011485:Protein Binding / Q000502:physiology; D017469:Receptors, Fibronectin / Q000378:metabolism; D016201:Receptors, Lymphocyte Homing / Q000378:metabolism; D017154:Stromal Cells
D005353:Fibronectins; D039041:Integrin alpha4beta1; D016023:Integrins; D017469:Receptors, Fibronectin; D016201:Receptors, Lymphocyte Homing