Negative selection by apoptosis enriches progenitors in naïve and expanded human umbilical cord blood grafts.
The influence of TNF-α and Fas-ligand (FasL) on viability and function was evaluated in fresh- and expanded-umbilical cord blood (UCB) cells. CD34(+) progenitors and T cells display outstanding survival, whereas ~30% and >50% B lymphocytes and myeloid cells undergo spontaneous apoptosis within 24 and 48 h, respectively. Although the impact of exposure to toxic doses of FasL and TNF-α was undetectable in measurements of apoptosis; removal of dead cells after 2 days of incubation with the ligands revealed a twofold increase in frequency of colony-forming cells (CFU). The sensitivity of progenitors to apoptosis was also unaffected by Fas cross-linking following TNF-induced upregulation of the receptor, increasing CFU frequency without impairing SCID repopulating cell (SRC) activity. Most significant enrichment in CD34(+) progenitors and corresponding increase in CFU frequency were observed when FasL was applied during the final week of ex vivo expansion under the influence of nicotinamide, without impairing SRC activity. These data emphasize differential sensitivities of UCB progenitors and lineage-positive cells to apoptotic signaling mediated by the Fas and TNF receptors, which might be useful in improving the efficiency of ex vivo expansion and improving UCB cell engraftment.
Department of Pediatric Hematology-Oncology, Frankel Laboratory, Center for Stem Cell Research, Schneider Children's Medical Center of Israel, Petach Tikva, Israel.
K
K
Mizrahi
Department of Pediatric Hematology-Oncology, Schneider Children's Medical Center of Israel, Petach Tikva, Israel.
S
S
Ash
Gamida Cell Ltd., Jerusalem, Israel.
T
T
Peled
Department of Pediatric Hematology-Oncology, Bone Marrow Transplant Unit, Schneider Children's Medical Center of Israel, Petach Tikva, Israel.
I
I
Yaniv
Department of Pediatric Hematology-Oncology, Schneider Children's Medical Center of Israel, Petach Tikva, Israel.
J
J
Stein
Department of Pediatric Hematology-Oncology, Frankel Laboratory, Center for Stem Cell Research, Schneider Children's Medical Center of Israel, Petach Tikva, Israel.
N
N
Askenasy
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D036101:Cord Blood Stem Cell Transplantation / Q000379:methods*; D005312:Fetal Blood / Q000166:cytology* / Q000637:transplantation*; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL