Proliferation and differentiation patterns of hematopoietic precursor from umbilical blood in mesenchymal stem cell microenvironment

AIM: To investigate the proliferation and differentiation patterns of hematopoietic precursors from cord blood in mesenchymal stem cell(MSC) microenvironment. METHODS: MSC was used as feeder cells, the mononuclear cells (MNCs) from cord blood were expanded in MSC microenvironment in the presence of stem cell factor(SCF), FMS-like tyrosine kinase 3 ligand(Flt3L), thrombopoietin (TPO) and IL-6. MNC count and colony-forming cell(CFC) culture were performed at week 1, 2, 3 and 4. RESULTS: (1) The number of MNCs increased and reached 108-fold in group MSC+CK(cytokine), but 7.8-fold in group CK at week 4. (2) CFC increased and reached the peak at week 3, the total number of CFC was higher in group MSC+CK than that in group CK, a rapid decline was observed at week 4. (3) The greatest expansion of erythroid CFC and high proliferative potential colony-forming cells(HPP-CFC) occurred at week 1, went down rapidly and dropped to zero at week 3, expansions in group MSC+CK were greater than that in group CK. (4) Myeloid CFC expanded continuously and the greatest expansion occurred at week 3, and declined at week 4. Myeloid CFC expanded greater in group MSC+CK than that in group CK. (5) CFC number per 104 MNCs reached the peak after one week of expansion, then declined rapidly from week 2, and dropped lower than that before expansion by the end of week 4.CONCLUSION: (1) Expansion ability of hematopoietic precursors from cord blood in MSC microenvironment is better than that in culture system without MSC. (2) Even expansion is performed in MSC microenvironment, differentiation could not be prevented. (3) Expansion of erythroid precursors occurrs in the early stages of ex vivo expansion. Expansion of myelomonocytic precursors lasts longer than that of erythroid.