Mechanism Of Thrombopoietin In Protecting Bone Marrow Endothelial Progenitor Cells Function Of Chemotherapy-treated Hematological Malignancies Patients

Background:Chemotherapy-induced thrombocytopenia(CIT)is a common adverse effect of large dose chemotherapy.Thrombocytopenia can delay the therapeutic schedule and be life threntening if bleeding occurs in a vital organ,such as brain.An intact bone marrow microenvironment are composed of bone marrow endothelial cells(BM-EPC),osteoclasts,adipocytes,etc.and it plays an important role in the process of platelet formation.How to shorten the time of platelets construction and decrease the bleeding events are still a challenge to us.Recombinant human thrombopoietin(rhTPO)is widely used in the treatment of CIT and has been proved to be effective.Our previous study shows that rhTPO can rescue the BM-EPC function of chemotherapy-treated hematological malignancies patients.But the mechanism of it is still unknown.So we conducted a series of experiments to figure it out.Methods:In the first part of the experiment,bone marrow mononuclear cells(BMMNCs)were isolated from the bone marrow of patients with hematological malignancies after 30 days of chemotherapy.The adherent cells were proved to be BM-EPCs and cultured with and without rhTPO.rhTPO can protect BM-EPCs functions by comparing their proliferation,tube formation,and migration functions.In the second part of our study,we conducted western blot to explore the effect of rhTPO in P13K/AKT pathway and Src/Erk pathway.At last,we verified it with inhibitors FR180204 and LY294002.Results:1.rhTPO can rescue the function of BM-EPCs function of chemotherapy-treated hematological malignancies patients in proliferation,tube formation,and migration.2.rhTPO can upregulation the P13K/AKT pathway(N=6 P<0.05)and Src/Erk pathway(N=6 P<0.05).3.The IC50 of FR180204 and LY294002 on BM-EPC were 40uM and 10uM respectively.After the addition of FR180204 and LY294002 inhibitors,the proliferation,migration and tubue formation of BM-EPC in the rhTPO group were decreased.Conclusion:TPO can activate PI3K/Akt and Src/ERK pathways by binding to c-mpl receptors to promote the proliferation,tube formation and migration of BM-EPC.