Thrombopoietin stimulated ex vivo expansion of megakaryocytes in human bone marrow.

SCHATTNER M; LEFEBVRE P; SPANIER MINGOLELLI S; GOOLSBY CL; RADEMAKER A; WHITE JG; FOSTER D; COHEN I

Seattle, USA

Congreso; XXXVI Congress of the American Society of Hematology; 1995

THROMBOPOIETIN STIMULATED EX VIVO EXPANSION OF MEGAKARYOCYTES IN HUMAN BONE MARROW. The effect of thrombopoietin (TPO) on megakaryocytopoiesis (MKP) has been mainly examined using clonogenic assays in murine systems. ln this study, we evaluated. MKP in liquid cultures using human bone marrow mononuclear cells (MNCs) and purified CD34+ cells.While interleukin-3 (IL-3) and stem cell factor (SCF) are potent activators of TPO-stimulated MKP in the murine system, only IL-3 exhibited a synergistic activity with TPO in cultures of human bone marrow cells. The IL-3 effect on TPO stimulated MK proliferation, expressed as the absolute number of megakaryocytes per seeded CD34+ cell, was more pronounced with purified CD34+ cells (5.7 ± 1.6 SEM vs 1.8 ± 0.5 SEM in presence and absence of IL-3, respectively) than with MNCs (13.7 ± 2.2 SEM vs 9.7 ± 1.7 SEM). This effect of IL-3 on TPO stimulated MK proliferation was due to a general proliferation of all cell types since the relative frequency of MKs (32.1 ± 3 SEM and 55.8± 3 SEM in MNCs and CD34+ cells, respectively) was not affected by IL-3. Under all conditions, greater proliferation of MKs was obtained with MNCs than CD34+ cells. This effect of MNCs was also observed on MK ploidy in the presence of TPO and IL-3. While proliferation and ploidy increase with TPO concentration in the murine system, they are inversely related in the human system. A significant 2.5 fold enhancement of TPO induced MK proliferation was observed when purified CD34+ cells were cultured in inserts separated from human bone marrow stroma, indicating that soluble stimulatory factors are released from stroma. These findings will help in designing an ex vivo expansion protocol for MKs in the management of post-transplant or chemotherapy thrombocytopenia.