Dissecting the Marrow Microenvironment

Abstract

Cloned human stromal cell lines representing functionally distinct cellular components of the marrow microenvironment were generated to serve as tools for identifying gene products that regulate hematopoiesis. Oligonucleotide arrays, or "gene chips" were used to provide a comprehensive comparison of gene expression among the cell lines. One line, designated HS-5, was found to secrete large amounts of cytokines, and conditioned media from this line was found to support the ex vivo expansion of both immature and mature progenitors. In contrast, a second line, designated HS-27a, does not secrete known cytokines but does support cobblestone area formation by CD34+/38lo cells. HS-27a, but not HS-5, was also found to express hJagged1, a ligand for Notch1, which may function to influence cell fate decisions of hematopoietic precursors. Both cell lines are currently being used to identify other gene products that regulate hematopoiesis and to generate reagents that will allow more formal evaluation of the putative role of hJagged1 in hematopoietic cell fate decisions.

Functional interleukin-7 receptors (IL-7Rs) are expressed by marrow stromal cells: binding of IL-7 increases levels of IL-6 mRNA and secreted protein

“…3 Relative gene expression levels between HS-5 and HS-27a were consistent between the 2 data sets. Importantly, ratios of gene expression for several known stromal factors were also consistently reflected in levels of secreted proteins.…”

“…1,2 Differential gene expression in HS-27a and HS-5 cell lines was previously investigated on small-scale Affymetrix gene chips specifying 250 genes, most of which were cytokines and chemokines. 3 These original array data, although limited in scope, did confirm that the 2 cell lines were functionally distinct with HS-5 expressing more RNA for factors like granulocyte colonystimulating factor (G-CSF) and granulocyte-macrophage colonystimulating factor (GM-CSF), whereas HS-27a expressed more message for stromal cell-derived factor 1 (SDF-1) and transforming growth factor-␤ (TGF␤). We have now used a large-scale DNA spotted microarray technology to provide a more comprehensive understanding of genes differentially expressed between HS-27a and HS-5.…”

Stromal Cells in Dense Collagen Promote Cardiomyocyte and Microvascular Patterning in Engineered Human Heart Tissue

“…HS27a and HS5 have been extensively characterized and although both lines secrete a plethora of ECM proteins, they have distinct functions due to differing expression of matrix proteases and cytokines. 36,47,48 hDFs are known to secrete vast amounts of extracellular matrix and matrix degradation proteins normally and during wound healing. 49 FHH cells were selected based on their expression of pericyte markers NG2 and PDGFRb, suggesting a more pericyte-like function of vascular stabilization.…”

Angiotensin II stimulates arachidonic acid release from bone marrow stromal cells

“…18,19 Since human HS-5 MSC express AT 1 -receptor mRNA 15 and we showed that rat MSC express AT 1 -and AT 2 -receptor mRNA and protein, 17 regulation of MSC function may represent an additional pathway by which Ang II influences haematopoiesis. Arachidonic acid (AA), a biologically active fatty acid released by MSC, modulates differentiation of HSC and erythroid and myeloid precursors through eicosanoid metabolites and the production of haematopoietic regulatory factors, 20,21 and may also directly alter the function of HSC. 22 Release of AA by AT 1 -and AT 2 -mediated receptorstimulation of a variety of cell types results in altered cell growth and proliferation, 23,25 suggesting that MSC may also respond to Ang II by increased AA release.…”