BACKGROUND: Some patients demonstrate delayed recoveries after autologous hematopoietic stem cell transplantation despite infusion of an adequate number of CD34+ cells/kg and clinically stable status. Factors considered being possible predictors of this outcome in this context were explored.
STUDY DESIGN AND METHODS: A total of 246 patients were evaluated in terms of engraftment. Delayed recovery was defined by white blood cell recovery time exceeding mean + 1 SEM. Clinical factors and graft characteristics were examined. Comparisons between patients with normal or delayed engraftment were made. Proinflammatory cytokines and proteolytic enzyme quantification and CXCR4+ and CD44+ cell enumeration were performed on peripheral hematopoietic stem cells (PHSC) product samples of patients with delayed engraftment and patients with usual engraftment time.
RESULTS: Sixteen patients, who received at least 3 × 106 CD34+ cells/kg without known clinical factors likely to affect engraftment, demonstrated a delayed recovery time of over 20 days. Some graft variables were found to be significantly increased in these patients by univariate analysis. One variable was the total number of nucleated cells cryopreserved and infused. Among the nucleated cells, the absolute number of granulocytes before and after cryopreservation also differed significantly between the two groups. A multivariate analysis showed that the main predictive factor for delayed recovery was the number of nucleated cells in the graft (p = 0.0044). The influence of contaminating cells might be related to the release of elastase, matrix metalloproteinase-9, interleukin (IL)-1β, and IL-6 involved in stem cell homing.
CONCLUSION: Therefore, the numeration of total nucleated cells and granulocytes should be considered as a possible quality control variable of PHSCs submitted for cryopreservation.