Bone marrow sinusoidal endothelial cells undergo nonapoptotic cell death and are replaced by proliferating sinusoidal cells in situ to maintain the vascular niche following lethal irradiation

Li, Xiao-Miao; Hu, Zhongbo; Jorgenson, Marda L.; Wingard, John R.; Slayton, William B.

doi:10.1016/j.exphem.2008.06.009

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Volume 36, Issue 9 , Pages 1143-1156.e3, September 2008

Bone marrow sinusoidal endothelial cells undergo nonapoptotic cell death and are replaced by proliferating sinusoidal cells in situ to maintain the vascular niche following lethal irradiation

Xiao-Miao Li
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Florida, Gainesville, Fla., USA
Zhongbo Hu
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Florida, Gainesville, Fla., USA
Marda L. Jorgenson
- Department of Regenerative Medicine, University of Florida, Gainesville, Fla., USA
John R. Wingard
- Department of Medicine Division of Blood and Marrow Transplantation, University of Florida, Gainesville, Fla., USA
William B. Slayton
- Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Florida, Gainesville, Fla., USA
- Offprint requests to: William B. Slayton, M.D., Department of Pediatrics, Division of Pediatric Hematology/Oncology, University of Florida Health Sciences Center, Box 100296, Gainesville, FL 32610

Received 11 June 2008; received in revised form 11 June 2008; accepted 18 June 2008.

Objective

Bone marrow sinusoids remain predominantly host-derived following bone marrow transplantation. Systematic analysis was conducted at the cellular level to investigate how the host sinusoidal structures survived after lethal irradiation.

Materials and Methods

Apoptosis and cell proliferation assays were performed on bone marrow sections at various time points during the first 2 weeks postirradiation to study the extent of damage to sinusoidal endothelial cells from lethal irradiation and to determine whether cell proliferation contributes to the recovery of the sinusoidal system.

Results

Phosphorylated H2AX was present in both hematopoietic and sinusoidal endothelial cells 3 hours after irradiation demonstrating DNA damage. Three days after irradiation, some sinusoidal endothelial cells became terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling –positive, but were caspase-3 and in situ oligo ligation –negative, suggesting nonapoptotic DNA fragmentation. Clusters of sinusoidal endothelial cells that expressed Ki67 appeared 3 days after irradiation, and increased through day 7. These Ki67-positive endothelial cells were host-derived. Bromodeoxyuridine-positive endothelial cells were present in the Ki67-positive areas confirming endothelial cell replication. Twenty percent of the sinusoidal endothelial cells were lost by day 3 after irradiation. The total number of endothelial cells remained relatively unchanged between day 3 and day 14. These results demonstrate that lethal irradiation resulted in limited, nonapoptotic sinusoidal endothelial cell loss, followed by proliferation of preexisting host-derived mature sinusoidal endothelial cells. Our data suggest that DNA repair mechanisms and proliferation of host endothelial cells within the sinusoids are involved in maintenance of the structural integrity of the bone marrow vascular niche following lethal irradiation.