Thrombopoietin and the TPO receptorduring platelet storage.
BACKGROUND
For most cells, the addition of a specific growth factor has improved cellular viability by preventing programmed cell death (apoptosis). To determine whether the platelet-specific hematopoietic growth factor thrombopoietin (TPO) might improve platelet viability, endogenous TPO and the platelet TPO receptor were analyzed during storage, and the effect of recombinant TPO on platelet viability was assessed.


METHODS
During platelet storage, TPO stability was assessed by SDS-PAGE, TPO receptor function was measured, and the platelet TPO receptor was characterized by a (125)I-rHuTPO competitive-binding assay. A recombinant TPO, pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF), was added to platelet concentrates during storage, and its effect on pH, LDH, and metabolic activity was determined.


RESULTS
During storage, the molecular weight and concentration of endogenous TPO (125 +/- 19 pg/mL) and exogenous TPO (5720 +/- 140 pg/mL) were constant for 12 days; the number (33 +/- 4), binding affinity (149 +/- 33 pM), and function of the platelet TPO receptors were constant for 7 days. Metabolic activity measured with the MTT and MTS assays closely correlated with changes in the pH and LDH. The addition of PEG-rHuMGDF did not alter the pH, LDH, or metabolic activity of platelets during storage, but it did increase by 65 percent the uptake of (35)S-methionine into platelets. Finally, platelet concentrates obtained from donors treated with PEG-rHuMGDF retained normal metabolic activity for 12 days, as compared with 5 to 6 days for normal platelet concentrates.


CONCLUSIONS
TPO and its platelet receptor are present in normal amounts and have normal function during platelet storage. The addition of recombinant TPO increased platelet methionine transport but did not alter platelet viability during storage. Other means to prevent apoptosis during platelet storage should be considered, and the measurement of platelet metabolic activity by MTT and MTS assays may assist this effort.
Xia
Y
Y
Hematology-Oncology Unit, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
Li
J
J
Bertino
A
A
Kuter
D J
DJ
D001792:Blood Platelets / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D001793:Blood Preservation; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007770:L-Lactate Dehydrogenase / Q000097:blood; D008715:Methionine / Q000187:drug effects / Q000493:pharmacokinetics; D009363:Neoplasm Proteins; D011092:Polyethylene Glycols / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000494:pharmacology*; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D011994:Recombinant Proteins / Q000494:pharmacology; D013926:Thrombopoietin / Q000494:pharmacology*
D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D011994:Recombinant Proteins; C103117:polyethylene glycol-recombinant human megakaryocyte growth and development factor; C082218:MPL protein, human; D011092:Polyethylene Glycols; D013926:Thrombopoietin; D008715:Methionine; D007770:L-Lactate Dehydrogenase