Bone marrow architecture reconstitution after hematopoietic grafting: A cross-sectional study

Objective

Changes in bone marrow (BM) architecture and its remodeling after hematopoietic stem cell transplantation (HSCT) following a reduced-intensity conditioning regimen for treating malignant hematologic diseases are poorly documented. We assessed these changes and their correlation with the clinical course to investigate the dynamics of this process.

Material and methods

Hematology patients who received a reduced intensity conditioning (RIC) were followed after successful allogeneic or autologous HSCT. Patients had at least 100 days after hematopoietic grafting. Post-transplant BM architecture was assessed by expert examination of a trephine biopsy using age-adjusted scores and histopathology results were contrasted with clinical post-transplant evolution to determine meaningful associations.

Results

Twenty-seven HSCT recipients, 19 allogeneic and 8 autologous, were studied at a median 155 (100–721) days post-transplant. Eleven (40.7%) had hypocellular biopsies with around 50% of the expected cell composition for a normal individual at that age. Patients with increased fibrosis had lower peripheral white blood cell counts compared to those with normal reticulin distribution (p = 0.015). A decrease in overall survival (OS) was documented in the group with more severe myelofibrosis at a median 813 days of follow-up. Infectious complications were more frequent in patients receiving an allogeneic (n = 6) compared with the recipients of an autologous transplant (n = 0).

Conclusions

Despite normal peripheral blood count and composition, significant post-transplant hypocellularity, revealing incomplete bone marrow reconstitution, was documented after HSCT in patients conditioned with a RIC regimen. Severe BM fibrosis was associated to decrease OS.