Abstract
Background aims. Delayed neutrophil recovery following autologous hematopoietic stem cell transplantation (aHSCT) increases transplant-related morbidity. Apoptosis induced by cryopreservation and thawing of hematopoietic progenitor cells collected by apheresis (HPC-A) was investigated in this nested case-control study as a factor associated with delayed neutrophil recovery following aHSCT. Methods. Among patients with lymphoma who underwent aHSCT between 2000 and 2007 (n = 326), 13 cases of primary delayed neutrophil recovery and 22 age- and sex-matched controls were identified. Apoptosis and viability were measured using multiparameter flow cytometry, and colony-forming capacity was determined using semi-solid methylcellulose assays. Results. HPC-A grafts from cases and controls had similar percentages of viable mononuclear cells (MNC) and CD34+progenitor cells, as determined by standard 7AAD dye exclusion methods measured before and after cryopreservation. Patients with delayed neutrophil recovery received increased numbers of apoptotic MNC (P = 0.02) but similar numbers of apoptotic CD34+ cells per kilogram measured after thawing. Apoptosis was more pronounced in MNC compared with CD34+ cells after thawing, and apoptosis was negligible in freshly collected HPC-A products. Patients with delayed neutrophil recovery had fewer total colony-forming unites (CFU) and CFU-granulocyte–macrophages (GM) per 105 viable post-thaw MNC compared with controls (P < 0.05). Conclusions. Increased numbers of apoptotic MNC in thawed HPC-A products are associated with delayed neutrophil recovery after aHSCT. Studies that address factors contributing to increased apoptosis are needed, and measuring apoptosis in thawed HPC-A may have a role in the assessment of graft adequacy.
Acknowledgments
This work was supported in part by an award from MITACS Accelerate (Canada). DSA is an Adjunct Scientist with Canadian Blood Services and a recipient of a Research Award from the Department of Medicine at the University of Ottawa and a New Investigator Award from Canadian Institutes of Health Research. RB holds a Canada Research Chair in Medicinal Chemistry. We are grateful for the patients and their families who entrusted their care to our team of physicians, nurses, pharmacists and health care providers at The Ottawa Hospital. We wish to gratefully acknowledge the assistance of Sheryl Mcdiarmid for expert assistance with the BMT database at The Ottawa Hospital, supported by The Ottawa Hospital Foundation.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.