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Scanning electron microscopy studies of bone marrow
Abstract:
This paper reviews scanning electron microscopy (SEM) observations of bone marrow, based on our findings on the marrow of rat femur and tibia. The marrow sinuses are lined by an endothelium, of which the cell juncture is undulated and overlapping. The endothelium is backed by a thin sheet of adventitial cells which is discontinuous because of large perforations. Mature blood cells pass through the discontinuous parts of the adventitial cells and then penetrate the endothelium at its parajunctional zone. Mature megakaryocytes reveal the demarcation membrane system in their cracked surfaces, and its orifices in their surface. The platelet liberation is visualized by a bunch of ribbons projected from a megakaryocyte into the sinus lumen; these ribbons become beaded and then separate into platelets. After puncture perfusion into the parenchyme of marrow, erythroblastic islands can be clearly demonstrated by SEM. Erythroblasts with rhopheocytotic pits are embraced by a nursing cell which, with its filopodia and lamellipodia, corresponds to the macrophage and clearly differs from the reticular cell. The nursing cell differs in size from island to island and occasionally shows indications of cell death. The erythroblasts in an island may be in a uniform maturation stage or in a few different stages. Adipose cells in the marrow are observed and their relation to reticular cells is discussed.
Insights
Scanning electron microscopy reveals bone marrow structure, detailing how blood cells, including platelets from megakaryocytes, navigate sinus endothelium. It also visualizes erythroblastic islands and nursing macrophages within the marrow.
Area of Science:
- Hematology
- Cell Biology
- Microscopy
Background:
- Understanding bone marrow microenvironment is crucial for hematopoiesis.
- Scanning electron microscopy (SEM) offers unique insights into cellular structures and interactions.
Purpose of the Study:
- To detail the ultrastructure of rat bone marrow using SEM.
- To visualize the process of blood cell formation and egress from the marrow.
Main Methods:
- Scanning electron microscopy (SEM) of rat femur and tibia bone marrow.
- Puncture perfusion technique for in situ visualization.
Main Results:
- SEM revealed detailed endothelium structure of marrow sinuses and adventitial cell layers.
- Observed mature megakaryocytes undergoing platelet liberation.
- Visualized erythroblastic islands with nursing macrophages and erythroblast maturation stages.
Conclusions:
- SEM provides high-resolution imaging of bone marrow cellular components and their spatial relationships.
- The study elucidates the pathways for mature blood cell egress and the role of macrophages in erythroblast development.