[Effect of IL-6/sIL-6R on ex vivo expansion of human cord blood derived CD34+ cells]

Abstract

Background & objective: Hematopoietic stem cells (HSC) have the ability of regeneration, differentiation, and reconstructing hematopoietic function, and it is widely used in many fields such as hematopoietic stem cell transplantation, immune therapy, gene therapy and so on. Human cord blood (CB) is abundant of HSC. But a single collection of CB has only a limited amount of HCS and cannot fit the clinical and research use. Thus ex vivo expansion of human CB derived HSC is important. We know that there are some cytokines, which can synergize for enhancing the expansion of CB derived CD34(+) cells in vitro. Currently, some experiments have discovered that IL-6/sIL-6R or its chimera can enhance the ex vivo expansion of CD34(+)gp130+IL-6R- subpopulation. This study was designed to observe the effect of IL-6/sIL-6R on the ex vivo expansion of human CB derived CD34(+) cells, and explore the optimal cytokine combinations.

Methods: Human CB derived CD34(+) cells were isolated by Mini MACS and cultured in ex vivo liquid media in the presence of different cytokine cocktails for 7 or 14 days. After cultured on the seventh or the fourteenth day, the total number of the cultured cells were counted, the ratio of the CD34(+) cell were assayed by flow cytometry (FCM) and the number of it were calculated, and CFU-GM were cultured, then the effects of different cytokine combinations on the ex vivo expansion of CD34(+) cells were compared. In line with the different cytokine cocktails, our experiment divided into five groups: (A) control,(B) SCF,(C) IL-6/sIL-6R+SCF,(D) IL-6/sIL-6R+SCF+FL,and (E) SCF+FL.

Results: After cultured in vitro for 7 or 14 days, (1) the number of CD34(+) cells descended apparently in groups A and B; (2) the number of nucleated cells and CD34(+) cells after cultural on the seventh or the fourteenth day increased 7.1+/-2.4 folds, 39.0+/-14.0 folds; 1.8+/-0.7 folds, 4.8+/-2.4 folds, respectively in group C; 16.5+/-5.7 folds, 110.0+/-28.0 folds; 3.5+/-1.5 folds, 10.2+/-4.2 folds in Group D; 17.3+/-3.8 folds, 104.0+/-21.0 folds; 3.6+/-2.1folds, 8.4+/-3.5 folds in Group E. The expansion effects of group C, D, and E were all superior to the group A or B (P< 0.01). The expansion effects of group D and E were superior to group C (P< 0.01). But there was no difference between group D and E (P >0.05); (3) Adding the concentration of sIL-6R to 400 ng/ml, the number of nucleated and CD34(+) cells increased 24.0+/-4.8 folds and 5.6+/-1.2 folds in group D after cultured for seven days superior to group E (P< 0.05).

Conclusion: IL-6/sIL-6R, SCF, FL can synergize for enhancing the ex vivo expansion of human CB derived CD34(+) cells. But this synergetic effect depends on the concentration of sIL-6R.