Background: The vascular niche of immune thrombocytopenia (ITP) is proven to be damaged.
It is presented as the impaired functions of migration and tube-formation in bone marrow endothelial progenitor cells (BM-EPCs). Our previous studies shown that thrombopoietin (TPO) has a protective effect on human endothelial cells.

Aims: This study aims to investigate whether TPO has a protective effect in ITP-EPCs, and to explore its potential mechanism.

Methods: BM-EPCs were isolated from ITP patients, and divided into two groups: TPO-treated group and TPO-free (control) group. CCK8 was used to explore the proliferative effect of TPO on BM-EPCs. BM-EPCs was identified by flow cytometry with co-expression of mouse anti-humanCD133, mouse anti-human CD34 and mouse anti-human vascular endothelial growth factor receptor (CD309) monoclonal antibodies. Moreover, the number of EPCs was evaluated with DiL-Ac-LDL uptake and FITC-UEA -I binding assay. The BM-EPCs functions were examed by tube-formation and migration experiments.

Results: The EPCs isolated from ITP patient in TPO-treated group exhibited longer fusiform and elliptical shape after 5 days and cobblestone-like morphology after 7-10 days culture. The result of CCK-8 showed TPO promoted proliferation of EPCs and the optional drug concentration is 100 ng/ml. Much higher co-expression of CD34/CD133/CD309 in TPO-treated group was detected by flow cytometry. The number of DiL-Ac-LDL (red) and FITC-UEA -I (green) double-stained cells in the TPO group was significantly higher than that of control group (n=10, p＜0.05). The tube formation (n=10, p< 0.05) and migration capacity (n=8, p< 0.05) were significantly enhanced in TPO-treated group.

Conclusions: Our studies indicates that TPO exerts protective effect of BM-EPCs in ITP patients, which may rescue megakaryopoiesis and reduce hemorrhage in these cases.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/role-of-thrombopoietin-in-rescuing-vascular-niche-of-itp-patients/