Comparison of Cord Blood CD34 + Stem Cell Expansion in Coculture with Mesenchymal Stem Cells Overexpressing SDF‐1 and Soluble /membrane Isoforms of SCF

Aim Umbilical cord blood hematopoietic stem cells (UCB HSCs) have been considered for the treatment of hematological malignancies due to their noninvasive collection, greater capacity of expansion, and remarkable tolerance for HLA mismatch in transplantation. On the other hand, the most considerable limitation of these cells is their inadequate amount of CD34 + HSCs which leads to delayed engraftment. The aim of this study was the expansion of CD34 + HSCs by coculturing with mesenchymal stem cells (MSCs) overexpressing stromal cell-derived factor-1, soluble and membrane isoforms of stem cell factor (sSCF/mSCF). Keeping structure and function of overexpressed cytokines by MSCs was expected which could beneficially affect the CD34 + HSC expansion. Methods MSCs and CD34 + HSCs were isolated from UCB mononuclear cells. UCB MSCs were nucleofected with one or more of sSCF, mSCF, and SDF-1 expression vectors. Isolated CD34 + HSCs were then cocultured with nucleofected MSCs in 10 groups in culture medium containing TPO and Flt3L with or without SCF (3F or 2F groups). Then the CD34 + HSCs numeration, clonogenic capacity, and transcriptional levels of well-known HSCs regulatory and stemness genes (CXCR4, HOXB4, BMI1, and SALL4) were assessed following coculture with modified MSCs. Results CD34 + HSCs which expanded on MSCs overexpressing mSCF/sSCF/SDF-1 in the 3F group showed the most significant increase in the expansion (4.73 +/- 0.26 fold), clonogenic capacity (5.3 +/- 0.25 fold) and also transcriptional levels of CXCR4, HOXB4, and BMI1 (3.49 +/- 0.13, 9.49 +/- 0.78, and 11.6 +/- 0.9 fold), respectively (P < 0.05). Conclusion Overexpression of SCF and SDF-1 by UCB MSCs in coculture system has efficient effect on UCB HSCs expansion. Furthermore nucleofected MSC overexpressing either sSCF/mSCF or mSCF/ sSCF /SDF-1 could substitute the rhu SCF in HSC expansion culture medium.