Extracellular matrix gene expression by human bone marrow stroma and by marrow fibroblasts.

In the marrow space hemopoietic progenitors interact with stromal cells allowing homing, migration and the expression of developmental programs. Some of these interactions are mediated by extracellular matrix molecules (ECM) which are produced by marrow stromal cells. In the murine system the nature of these interactions and its biological significance have been studied in vitro by using indistinctly, either whole stroma (obtained from long-term marrow cultures) or isolated stromal (fibroblast-like) cells. In an attempt to analyze whether in the human system both sources of stromal cells are equivalent in terms of production of ECM components, we measured the expression of genes encoding for several ECM proteins. The results obtained show that whole stroma as well as marrow fibroblasts express genes for collagen types I, III, IV, V and VI as well as for fibronectin and laminin. However, the relative abundance of mRNA transcripts for some of these proteins was higher in marrow fibroblasts as compared to whole stroma. The latter was further supported by an increased collagen synthesis observed in marrow fibroblasts as compared to whole stroma.