Assessment of stability of CD34+ cell products enriched by immunoselection from peripheral blood mononuclear cells during refrigerated storage

Durable engraftment of transplanted CD34+ cells largely depends on the quality of the cell product. Limited data are currently available about extended storage of immunoselected CD34+ cells. The aim of our study was to assess the stability of CD34+ cell product with the cells stored in high concentration (80 × 106 in 6 mL) in small bags intended for cell implantation. Cell products were prepared by leukapheresis and immunoselection (Clinimacsplus procedure) from 13 patients with chronic dilated cardiomyopathy. CD34+ cell products were stored at 2-8 °C and analyzed at time 0 (fresh products), 24, 48 h, 4 and 6 days. Product viability, absolute number of viable CD34+ cells and apoptosis were determined by flow cytometry. Microbiological contamination of the cell products was tested by BACTEC system. The mean viability of CD34+ cells decreased by 2.7% within 24 h, by 13.4% within 48 h and by 37.5% within 6 days. The mean recovery of viable CD34+ cells was 91.1%, 74.8%, 66.3% and 56.2% at 24, 48 h, 4 and 6 days, respectively. The mean fraction of early apoptotic cells in fresh and stored products was 4.9 ± 3.5% at 0 h, 5.9 ± 3.8% at 24 h, 4.2 ± 3.1% at 48 h, 6.3 ± 2.6% at 4 days and 9.3 ± 4.6% at 6 days. All products were negative for microbial contamination.