Human aging is associated with a decrease in tissue functions combined with a decline in stem cells frequency and activity followed by a loss of regenerative capacity. The molecular mechanisms behind ...this senescence remain largely obscure, precluding targeted approaches to counteract aging. Focusing on mesenchymal stromal/stem cells (MSC) as known adult progenitors, we identified a specific switch in miRNA expression during aging, revealing a miR‐196a upregulation which was inversely correlated with MSC proliferation through HOXB7 targeting. A forced HOXB7 expression was associated with an improved cell growth, a reduction of senescence, and an improved osteogenesis linked to a dramatic increase of autocrine basic fibroblast growth factor secretion. These findings, along with the progressive decrease of HOXB7 levels observed during skeletal aging in mice, indicate HOXB7 as a master factor driving progenitors behavior lifetime, providing a better understanding of bone senescence and leading to an optimization of MSC performance. Stem Cells 2015;33:939–950
The peptide hormone glucagon binds to plasma membrane receptors in the liver and activates adenylate cyclase. The two-step, collagenase perfusion of intact liver was used to prepare a suspension of ...isolated hepatocytes. Isopycnic centrifugation through a Percoll density gradient removed nonparenchymal cells, nonviable cells, cell debris, and soluble material to produce consistent, viable populations of hepatocytes used in the study of the binding and internalization phenomena. Competition binding assays and Scatchard analyses are indicative of a single class of receptors binding glucagon by a noncooperative mechanism at 0(DEGREES)C and 37(DEGREES)C. The association of glucagon with the hepatocyte receptor at a variety of hormone concentrations is consistent with these conclusions at both temperatures. The observed rate constant of association is directly proportional to hormone concentration at 0(DEGREES)C, but the relationship demonstrates a downward deviation from linearity at 37(DEGREES)C. Dissociation of glucagon bound to hepatocyte receptors approximates first order kinetics at 0(DEGREES)C. However, dissociation is biexponential at 37(DEGREES)C and is dependent on the duration of receptor occupancy prior to dissociation. These data supports the hypothesis that the glucagon receptor exists in two interconvertible states. Glucagon binds to the low affinity state and then the receptor undergoes a time-dependent, temperature-dependent conversion to the high affinity state. The two-state receptor was further characterized by studying the binding of glucagon at a variety of concentrations and the binding of the glucagon analogues, (S-methyl-Met('27)) glucagon, a full agonist with reduced potency, and N('(alpha))-biotinyl-N('(epsilon))-acetimidoglucagon, a partial agonist with reduced potency. Increasing concentrations of glucagon increase the velocity of the entire binding reaction, but do not alter the equilibrium. (S-methyl-Met('27)) glucagon-receptor complexes exhibit the two-state characteristics analogous to native glucagon binding. N('(alpha))-biotinyl-N('(epsilon))-acetimidoglucagon-receptor complexes strikingly favor the formation of the low affinity state. This suggests that the low affinity state is not directly responsible for the activation of adenylate cyclase and that partial agonism is the consequence of the inability of a glucagon analogue to induce the high affinity receptor state. Subsequent to receptor binding, glucagon is translocated into the cell by a receptor-dependent mechanism. Endocytosis proceeds according to a first order rate constant of 0.183 min('-1) (t(, 1/2) = 3.8 min) until 30% of the cell-associated hormone has been internalized. The plasma membrane receptors are down-regulated in excess of the amount of glucagon internalized, suggesting that unoccupied receptors may also be internalized. Additionally, hepatocytes incubated in culture medium internalize 40% of the cell-associated hormone suggesting that extracellular factors modulate receptor-mediated endocytosis.
Abstract The impact of pretransplant (hematopoietic cell transplantation HCT) cytarabine consolidation therapy on post-HCT outcomes has yet to be evaluated after reduced-intensity or nonmyeloablative ...conditioning. We analyzed 604 adults with acute myeloid leukemia in first complete remission (CR1) reported to the Center for International Blood and Marrow Transplant Research who received a reduced-intensity or nonmyeloablative conditioning HCT from an HLA-identical sibling, HLA-matched unrelated donor, or umbilical cord blood donor from 2000 to 2010. We compared transplant outcomes based on exposure to cytarabine postremission consolidation. Three-year survival rates were 36% (95% confidence interval CI, 29% to 43%) in the no consolidation arm and 42% (95% CI, 37% to 47%) in the cytarabine consolidation arm ( P = .16). Disease-free survival was 34% (95% CI, 27% to 41%) and 41% (95% CI, 35% to 46%; P = .15), respectively. Three-year cumulative incidences of relapse were 37% (95% CI, 30% to 44%) and 38% (95% CI, 33% to 43%), respectively ( P = .80). Multivariate regression confirmed no effect of consolidation on relapse, disease-free survival, and survival. Before reduced-intensity or nonmyeloablative conditioning HCT, these data suggest pre-HCT consolidation cytarabine does not significantly alter outcomes and support prompt transition to transplant as soon as morphologic CR1 is attained. If HCT is delayed while identifying a donor, our data suggest that consolidation does not increase transplant treatment-related mortality and is reasonable if required.
The impact of pre transplant (HCT) cytarabine consolidation therapy on post HCT outcomes has yet to be evaluated after reduced intensity or non-myeloablative conditioning. We analyzed 604 adults with ...acute myeloid leukemia (AML) in first complete remission (CR1) reported to the CIBMTR who received a RIC or NMA HCT from an HLA-identical sibling, HLA-matched unrelated donor (URD), or umbilical cord blood (UCB) donor in 2000–2010. We compared transplant outcomes based on exposure to cytarabine post remission consolidation. Three year survival rates were 36% (29–43%, 95% CI) in the no consolidation arm and 42% (37–47%, 95% CI) in the cytarabine consolidation arm (p=0.16). Disease free survival was 34% (27–41%, 95% CI) and 41% (35–46%, 95% CI) (p=0.15), respectively. Three year cumulative incidences of relapse were 37% (30–44%, 95% CI) and 38% (33–43%, 95% CI), respectively (p=0.80). Multivariate regression confirmed no effect of consolidation on relapse, DFS and survival. Prior to RIC/NMA HCT, these data suggest pre-HCT consolidation cytarabine does not significantly alter outcomes and support prompt transition to transplant as soon as morphologic CR1 is attained. If HCT is delayed while identifying a donor, our data suggest that consolidation does not increase transplant TRM and is reasonable if required.
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