Journal
BLOOD
Volume 103, Issue 12, Pages 4496-4502Publisher
AMER SOC HEMATOLOGY
DOI: 10.1182/blood-2004-01-0256
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Funding
- NCI NIH HHS [CA 15704] Funding Source: Medline
- NHLBI NIH HHS [HL 62923] Funding Source: Medline
- NIDDK NIH HHS [DK 56465] Funding Source: Medline
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The hematopoietic microenvironment, approximated in vitro by long-term marrow cultures (LTCs), consists of both nonhematopoietic-derived stromal elements and hematopoietic-derived monocyte/macrophages. To better understand the consequences of monocyte-stroma interactions, we compared gene expression profiles of CD14(+) peripheral blood monocytes and HS-27a stromal cells cultured alone and together in cocultures. Results from 7 separate experiments revealed 22 genes were significantly up- or down-regulated in the cocultures, with osteopontin (OPN) up-regulated more than 15-fold. The microarray OPN data were confirmed by Northern blot, real-time polymerase chain reaction (PCR), and by detection of OPN protein. High levels of OPN gene expression were also detected in 2- to 3-week-old primary LTCs. Using Transwells we determined that stromal cells were secreting a factor that upregulated OPN gene expression in CD14(+) cells. When CD34(+) cells were cultured in the presence of purified OPN, tyrosine phosphorylation of a 34-kDa molecule was increased 2- to 3-fold, an effect that was diminished in the presence of an OPN neutralizing monoclonal antibody. In addition, Notch1 gene expression was decreased 5-fold in OPN-treated CD34(+) cells. We conclude that interactions between stroma and monocytes can result in activities that limit the role of Notch signaling in hematopoietic regulation. (C) 2004 by The American Society of Hematology.
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