Early down-regulation of Bcl-xL expression during megakaryocytic differentiation of thrombopoietin-induced CD34+ bone marrow cells in essential thrombocythemia.
OBJECTIVE
Essential thrombocythemia (ET) is a chronic myeloproliferative disorder with abnormal megakaryocyte/platelet production. Recent studies have found that Bcl-xL, as a member of the bcl-2 family of proteins that inhibit apoptosis, is essential in megakaryocytic differentiation. In this study the expression of Bcl-xL was evaluated during megakaryocytic differentiation in ET patients.


METHODS
To study the role of Bcl-xL in megakaryocyte differentiation, we evaluated the effect of small interfering RNA (siRNA) on the expression of Bcl-xL. CD34+ cells from patients with ET, chronic myeloid leukemia (CML), polycythemia vera (PV) and normal individuals were cultured in serum-free medium supplemented with thrombopoietin (TPO). Immunocytochemical staining and flow cytometric analysis were used to evaluate the Bcl-xL expression during megakaryocytic differentiation of CD34+ cells.


RESULTS
When exposured to si-Bcl-xL, the percentage of K562 cells induced into megakaryocytes in 72 hours was lower than the corresponding percentage of control cells. CD41a+ cells from the three groups of patients and the control group were cultured. At day 10, the percentage of Bcl-xL- cells in CD41a+ cells from ET patients was 61.0+/-28.1%, which was significantly higher than that from patients with CML (2.5+/-20.9%), PV (33.6+/-10.0%) or control subjects (15.1+/-13.0%).]


CONCLUSIONS
These results demonstrate that Bcl-xL is down-regulated early during in vitro differentiation of megakaryocytes from ET patients; this might reflect an early entry of megakaryocytes into a degenerating mature stage.
State Key Laboratory of Experimental Hematology, National Research Center for Stem Cell Engineering & Technology, Institute of Haematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, PR China.
Lei
L
Zhang
Hui
H
Zhao
Aihong
A
Sun
Shihong
S
Lu
Bin
B
Liu
Fengwu
F
Tang
Yi
Y
Feng
Lihua
L
Zhao
Renchi
R
Yang
Zhong Chao
ZC
Han
D000328:Adult; D017209:Apoptosis / Q000187:drug effects; D001854:Bone Marrow Cells / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects / Q000473:pathology; D002478:Cells, Cultured / Q000187:drug effects / Q000473:pathology; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D018390:Gene Targeting; D006801:Humans; D020014:K562 Cells / Q000187:drug effects / Q000473:pathology; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000473:pathology; D008297:Male; D008533:Megakaryocytes / Q000473:pathology*; D008875:Middle Aged; D011087:Polycythemia Vera / Q000473:pathology; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013920:Thrombocythemia, Essential / Q000473:pathology*; D013926:Thrombopoietin / Q000494:pharmacology*; D014162:Transfection; D051020:bcl-X Protein / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
C494811:BCL2L1 protein, human; D016895:Culture Media, Serum-Free; D034741:RNA, Small Interfering; D051020:bcl-X Protein; D013926:Thrombopoietin