Multilineage Hematopoietic Expression in a Three-Dimensional Long Term Bone Marrow Culture System

Abstract

The initial attempts to grow bone marrow cells in semi-solid or liquid medium promoted only the terminal differentiation of hematopoietic stem cells in the absence of self-renewal, with cultures becoming hematopoietically unproductive after 1–2 weeks of culture. Subsequent work in the murine system by Dexter and co-workers demonstrated that the sustained growth of hematopoietic cells in liquid culture was possible if these cells were plated onto a pre-established monolayer of bone marrow stromal cells³. These cells synthesize the matrix necessary to support hematopoiesis and contribute trophic/regulatory factors to the hematopoietic microenvironment. Inclusive of this group are fibroblasts, adipocytes reticular adventitial cells, macrophages, and endothelia⁴. The Dexter long-term bone marrow culture (LTBMC) system sustains the self renewal of murine pluripotential stem cells (CFU-S) although the lineage restricted progenitors become predominantly myeloid in character after the first several weeks of culture^3,5. This system can be modulated to favor the growth of lymphoid cells^6,7 or erythroid progenitors⁸, but single cultures do not produce substantial numbers of each hematologic cell type concurrently.