Study of In Vitro Proliferation Potential of CD133 Positive Cells Derived from Umbilical Cord Blood.

Transforming growth factor-beta 1 (TGF-β₁) is known to maintain primitive human hematopoietic stem/progenitor cells with polyfunctional role in a quiescent state and CD133 is a new stem cell antigen that may provide an alternative to CD34 for the selection and expansion of hematopoietic cells for transplantation. To investigate the specific effect of TGF-β₁ on proliferation and differentiation of CD133 positive cells derived from umbilical cord blood (UCB) during short-term culture in vitro, CD133 positive cells from 20 fresh UCB samples were selected using Miltenyi Biotec’s CliniMACS separation device and were cultured in IMDM medium with 20% FCS in the presence of a cytokine combination of SCF, IL-6, thrombopoietin, IL-3 and Flt3-ligand for up to 2 weeks and TGF-β₁ with low concentration was also added to the mediumon day 4. The proliferative response was assessed at day 7, day 10 and day 14 by evaluating the following parameters: nucleated cells (NC), clonogenic progenitors (CFU-GEMM,CFU-GM and BFU-E), and immunophenotypes (CD133 and CD34). The results showed that efficacious expansion of various hematopoietic stem/progenitor cells was constantly observed during the culture. The fold expansion of NC on day7, day10 and day14 expansion were 33.59,224.26 and 613.48, respectively. The fold expansion of CFU-GEMM, CFU-GM and BFU-E on day 10 were 24.89, 41.62 and 49.28, respectively, obviously higher than that without ex vivo expansion (P<0.05). The expansions of CD133⁺, CD133⁺CD34⁺ and CD34⁺ subpopulation on day 14 were up to 25.83-fold, 16.16-fold and 60.54-fold, respectively. Furthermore the expansion systems with TGF-β₁ showed more CD133⁺ cells than control at every time points. Our datas suggested that the CD133⁺ cells from human UCB have great expansion potential for ex-vivo expansion. The low concentration of TGF-β₁ may delay over-differentiation of hematopoietic stem/progenitor cells.