Summary:In all, 78 peripheral hematopoietic progenitor cell collections from 52 patients were evaluated using our previously published validated post-thaw assays at the time of collection and following transplantation by assessment of viable CD34 þ cells, and granulocytemacrophage colony-forming units (CFU-GM) cryopreserved in quality control vials. The median (range) post-thaw recovery of viable CD34 þ cells and CFU-GM was 66.4% (36.1-93.6%) and 63.0% (28.6-85.7%), respectively, which did not show significant correlation with the engraftment of either neutrophils (P ¼ 0.136 and 0.417, respectively) or platelets (P ¼ 0.88 and 0.126, respectively). However, the reinfused viable CD34 þ cells/ kg of patient weight pre-or post-cryopreservation showed significant correlation to engraftment of neutrophils (P ¼ 0.0001 and 0.001, respectively) and platelets (P ¼ 0.023 and 0.010, respectively), whereas CFU-GM pre-or post-cryopreservation was significantly correlated to neutrophils (P ¼ 0.011 and 0.007, respectively) but not to platelets (P ¼ 0.112 and 0.100, respectively). The results show that post-cryopreservation assessment of viable CD34 þ cells or CFU-GM is as reliable a predictor of rapid engraftment as that of pre-cryopreservation measures. Therefore, the post-cryopreservation number of viable CD34 þ cells or CFU-GM should be used to eliminate the risks of unforeseen cell loss that could occur during cryopreservation or long-term storage.

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BACKGROUND: Stromal cell-derived factor (SDF)-1, a chemokine produced in the bone marrow (BM), is essential for the homing of hematopoietic stem/ progenitor cells (HSPCs) to the BM after transplantation. This study examines whether there is a correlation between the in vitro chemotaxis of CD34+ HSPC toward an SDF-1 gradient and in vivo hematopoietic engraftment. STUDY DESIGN AND METHODS: Thirty-five patients underwent granulocyte-colony-stimulating factor HSPC collection and autologous transplant with a median dose of 7.7 (range, 3.9-41.5) ¥ 10 6 CD34+ cells per kg body weight. The chemotactic index (CI) of CD34+ cells isolated from leukapheresis products collected from these patients was calculated as the ratio of the percentages of cells migrating toward an SDF-1 gradient to cells migrating to media alone. Expression of the SDF-1 receptor CXCR4 on CD34+ cells was measured by flow cytometry. RESULTS: Spontaneous cell migration (range, 3.1 Ϯ 0.6 to 26.5 Ϯ 7.7%) and SDF-1-directed chemotaxis (11.1 Ϯ 0.7 to 54.9 Ϯ 8.3%) of CD34+ cells did not correlate with time to neutrophil engraftment, which occurred at a median of 10 days (range, 8-16 days). Nonparametric tests showed a negative correlation (r = -0.434) between CI and CD34+ cell dose such that neutrophil recovery occurred within the same period in patients transplanted with a lower dose of CD34+ cells but having a high CI as in those transplanted with a higher dose of CD34+ cells but having a low CI. Moreover, CI correlated (r = 0.8) with surface CXCR4 expression on CD34+ cells. CONCLUSION: In patients transplanted with a relatively lower CD34+ cell dose who achieved fast engraftment, a higher responsiveness to SDF-1 and high CI could have compensated for the lower cell dose. However, to apply the CI as a prognostic factor of the rate of engraftment requires validation in a larger number of patients.

We develop a Bayesian approach to a calibration problem with one interested covariate subject to multiplicative measurement errors. Our work is motivated by a stem cell study with the objective of establishing the recommended minimum doses for stem cell engraftment after a blood transplant. When determining a safe stem cell dose based on the prefreeze samples, the postcryopreservation recovery rate enters in the model as a multiplicative measurement error term, as shown in the model. We examine the impact of ignoring measurement errors in terms of asymptotic bias in the regression coefficient. According to the general structure of data available in practice, we propose a two-stage Bayesian method to perform model estimation via R2WinBUGS (Sturtz, Ligges, and Gelman, 2005, Journal of Statistical Software 12, 1-16). We illustrate this method by the aforementioned motivating example. The results of this study allow routine peripheral blood stem cell processing laboratories to establish recommended minimum stem cell doses for transplant and develop a systematic approach for further deciding whether the postthaw analysis is warranted.