Long term bone marrow cultures: an ultrastructural review

Area of Science:

• Hematology
• Stem Cell Biology
• Cell Biology

Background:

• Long-term liquid cultures of bone marrow support hematopoietic stem cells (HSCs) and myeloid lineages.
• Stromal cell layers are essential for sustained stem cell production and differentiation.

Purpose of the Study:

• To investigate the role of stromal cells and cellular interactions in supporting hematopoiesis in vitro.
• To characterize the cellular composition of the adherent stromal layer and hematopoietic lineages in bone marrow cultures.

Main Methods:

• Establishment and maintenance of long-term liquid bone marrow cultures.
• Identification and characterization of stromal cells (adipocytes, fibroblasts, reticulum cells, endothelial cells) and hematopoietic lineages (granulocytes, megakaryocytes, erythroid cells, monocytes, macrophages).
• Observation of cellular interactions within the culture system.

Main Results:

• Normal cultures support granulocyte maturation, which can be shifted to erythropoiesis with specific stimuli.
• An adherent stromal layer, derived from original marrow inoculum, is critical for stem cell and differentiating cell production.
• Identified stromal cells include adipocytes, fibroblasts, reticulum cells, and endothelial cells.
• Observed hematopoietic lineages include granulocytes, megakaryocytes, erythroid cells, monocytes, and macrophages.
• Documented cellular interactions, such as adipocyte-granulocyte and macrophage-erythroblast associations forming 'in vitro' erythroblastic islets.

Conclusions:

• The adherent stromal layer is vital for maintaining an 'in vitro' hematopoietic stem cell niche.
• Cellular interactions within the culture, particularly erythroblastic islets, contribute to the 'in vitro' haemopoietic inductive microenvironment.
• These findings provide insights into the mechanisms regulating hematopoiesis in a controlled laboratory setting.