title: In vitro and in vivo studies of stromal niches.
abstract: Lymphohematopoiesis occurs in the densely packed environment of the intramedullary spaces. Primitive lymphohematopoietic stem cells exist in close apposition to a variety of supportive cells including both hemopoietic and nonhemopoietic lineages. Using an in vitro long-term Dexter liquid culture system, we have established that a variety of cytokines are produced constitutively by such stromal cells in culture. These cytokines include Steel factor, interleukin-6 (IL-6), and colony-stimulating factor (CSF-1). Granulocyte-CSF and granulocyte-macrophage-CSF mRNA can be detected after refeeding of cultures, although in quiescent cultures message for these factors is difficult to detect. Interleukin-3, IL-4, and IL-5 are not detectable by standard Northern blot analysis or bioassay of condition media. However, IL-3--detectable by reverse-transcriptase PCR and biologic activity--was confirmed by growth of factor-dependent cells on stromal cells with IL-3 antibody blocking of such growth. Stem cells resident on such stromal cells are mirrored by the high proliferative potential colony-forming cell assay and are responsive to a relatively large number of cytokines, with Steel factor being of central importance, appearing to be a critical component of various synergistic combinations. Steel factor allows reduced levels of other factors in such combinations and works early in a temporal sequence. Hematopoietic stem cells can engraft in normal nonmyeloablated hosts. Using a male/female BALB/c transplantation model, we have shown high rates of engraftment into normal animals, out after marrow infusion to 25 months, after marrow infusion and that post-5-fluorouracil bone marrow is quite deficient in such engraftment.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, University of Massachusetts Medical Center, Worcester.
authors.forename: P J
authors.initials: PJ
authors.lastname: Quesenberry
authors.forename: R B
authors.initials: RB
authors.lastname: Crittenden
authors.forename: P
authors.initials: P
authors.lastname: Lowry
authors.forename: E W
authors.initials: EW
authors.lastname: Kittler
authors.forename: S
authors.initials: S
authors.lastname: Rao
authors.forename: S
authors.initials: S
authors.lastname: Peters
authors.forename: H
authors.initials: H
authors.lastname: Ramshaw
authors.forename: F M
authors.initials: FM
authors.lastname: Stewart
mesh_terms: D000818:Animals; D016026:Bone Marrow Transplantation / Q000473:pathology; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D013234:Stem Cells / Q000502:physiology; D017154:Stromal Cells / Q000378:metabolism / Q000502:physiology*
chemical_list: D016207:Cytokines