Pre- and post-cryopreservation enumeration of viable CD34+ haemopoietic stem cells in autologous peripheral blood stem cell products: do viable CD34+ stem cell numbers reduce with cryopreservation time?

Abstract

<h3>Introduction</h3> Autologous peripheral blood stem cell (PBSC) transplantation has an established role in the treatment of some haematological and non-haematological malignancies. The safety and efficacy of this procedure are dependent on the fact that haematopoietic stem cells can be mobilised, harvested, cryopre-served and accurately enumerated prior to transplantation. The effect of the cryopreservation procedure on the PBSC product is evaluated. <h3>Methods</h3> We analysed the number of CD34+ peripheral blood cell progenitors obtained by aphaeresis pre- and post-cryopreser-vation to determine if there is significant loss of CD34+ cells during freezing, processing and thawing. We then further correlated CD34+ cell degradation and its effect on neutrophil or platelet engraftment. <h3>Results</h3> Twenty-eight CD34 products from 28 individual patients, most undergoing treatment for haematological malignancy, were analysed for viable CD34 number using the standard ISHAGE single platform enumeration assay immediately post-harvest and pre-infusion. CD34 numbers were then calculated and expressed in the standard form of CD34+ cells/kg body weight. Mean pre-cryopreservation CD34+ cell product numbers were 4.04±2.17x106/kg (mean+SD). Mean post-cryopreservation CD34+ cell product numbers were 2.80±1.39x106/kg. Mean CD34+ ‘loss' with cryopreservation=1.24 ± 106/kg. Mean time to neutrophil and platelet engraftment was 10.6±0.04 and 13.52±0.13 days, respectively. There was no significant difference in CD34+ cell loss in products stored for >100 days compared with those stored for <100 days, with no change seen in engraftment potential. <h3>Conclusion</h3> Despite a documented decrease in viable CD 34 numbers arising form the cryopreservation and processing process, generally adequate CD34 numbers are preserved and no effect is seen on either neutrophil or platelet engraftment. The length of cryopreservation appears to have no effect on viable CD 34+ cell numbers inferring that cell loss, when it occurs, is during the initial processing of CD34+ products.