OBJECTIVETo investigate the effects of soluble M-CSF receptor (sMR) on proliferation and differentiation of hematopoietic precursors derived from umbilical cord blood in mesenchymal stem cell (MSC) microenvironment.

METHODIn group of cytokine (CK) + sMR, MSCs were used as feeder cells, mononuclear cells (MNCs) from cord blood were expanded in MSC microenvironment in presence of SCF, Flt3L, TPO, IL-6 and sMR. In CK control group, no sMR was added. MNC counting and colony forming cell (CFC) culture were performed at week 1, 2, 3 and 4.

RESULTS1) The number of MNCs increased rapidly in both group CK and group CK + sMR (108.47 -fold and 120.67 -fold, respectively, P > 0.05). 2) CFC increased, peaked at week 3(38.1 x 10(3)) and declined rapidly at week 4(18.1 x 10(3)) in group CK, but still increased in group CK + sMR at week 4 (84 x 10(3)), the total number of CFC was higher in group CK + sMR than in group CK at week 3 and week 4 (P <0.01). 3) The erythroid CFC peaked at week 1 (5891.2 and 5635.6 for groups CK and CK + sMR, respectively), then dropped rapidly and to zero at week 3, in both group CK and group CK + sMR (P > 0. 05). 4) Myeloid CFC expanded continuously and peaked at week 3 (31.5 x 10(3)), then declined at week 4 (18.3 x 10(3)) in group CK; but still increased at week 4(80.8 x 10(3)) in group CK + sMR, being higher than that in group CK at week 3 and week 4 (P <0.01).

CONCLUSIONsMR can inhibit the differentiation of cord blood hematopoietic precursors expanded in MSC microenvironment, but the inhibition exerts only on myelomonocytic but not on erythroid precursors.