Abstract
Background We and others have shown a critical role for CD34+ CD38− cells in hematopoietic recovery after autologous stem cell transplantation (ASCT), in particular for platelet reconstitution. Thus a routine assessment of CD34+ CD38− cells in freezing–thawing procedures for autografting could represent an important tool for predicting poor engraftment.
Methods To compare the impact of cryopreservation on CD34+ CD38+ and CD34+ CD38− hematopoietic stem cell subsets, 193 autograft products collected in 84 patients with malignancies were assessed before controlled-rate cryopreservation in 10% DMSO and after thawing for autografting.
Results Cell counts after thawing were significantly different from the pre-freezing counts for total CD34+ (P<0.0001) and CD34+ CD38+ (P<0.0001) cells, but not for CD34+ CD38− cells (P=0.252). Median losses for CD34+, CD34+ CD38+ and CD34+ CD38− cells were, respectively, 11.8%, 11.4% and 0.0%. The magnitude of fresh/post-thawing percentage cell variation was significantly different when comparing between the CD34+ CD38+ and CD34+ CD38− cell subsets (P<0.001). Moreover, CD34+ CD38− cells exhibited recovery values ≥100% in 85/160 graft products, compared with 51/193 in CD34+ CD38+ cells (P<0.0001). Also, recovery values ≥90% were significantly better in the CD34+ CD38− (98/160 grafts) than in the CD34+ CD38+ subsets (89/193 grafts) (P<0.01).
Discussion In this work we have demonstrated that CD34+ cells that do not express the CD38 Ag show a significantly better resistance to cryopreservation. This could represent another example of the particular ability of less committed progenitor cells to overcome environmental injuries. Moreover, we consider routine assessment of CD34+ CD38− cells before freezing as clinically relevant, but post-thawing controls may be avoided because of their good resistance to freezing.
