Fig. 5. Down-regulation of Dicer1 in MSCs stimulated MM cell proliferation and protected MM cells against apoptosis in vitro.

a NCI-H929 were co-cultured with MSCs: control-MSC (HC-MSC without transfection), negative MSC (transfected with control lentiviruses), Dicer1-KD MSC (shRNA), and MM-MSC for 24 h. Cell cycle behavior of H929 was assessed by Click-iT Edu Flow Cytometry Assay. Fluorescence-activated cell analysis plots from one representative experiment showing the cell cycle plots for cultured alone MM cell lines(H929) or with MSCs as indicated. The location of cells in different phases of the cell cycle is indicated in the left histogram, and the percentage of cells in S is given for each condition. b Summary of results from separate experiments. H929 cultured alone (control), or co-cultured with HC-MSCs from three healthy controls(H929 + HC-1-3MSC), or co-cultured with MM-MSCs from four different patient samples (H929 + MM1-4-MSC), or co-cultured with negative MSC (transfected with control lentiviruses), Dicer1-KD MSC (shRNA) for 24 h were assessed for the proportion of cells in S by Click-iT Edu Flow Cytometry Assay. The results are expressed as means ± SD. The average of three replicates is displayed. Compared with controls, the significance was set as *p ≤ 0.05; **p ≤ 0.01. c–e MSCs were cocultured in complete growth medium with MM cells (NCI-H929 or CD138⁺ MM cells) for 48 h at a ratio of 1:10 (MSCs/MM cells). As measured by AnnexinV/PI staining, MM-MSCs could protect against Bortezomib-induced apoptosis at a ratio of 1:10 (MSCs/MM cells). Similarly, MSC-Dicer1-shRNA can also protect Bortezomib-induced apoptosis of MM cells. The results are expressed as means ± SD. The average of three replicates is displayed. Compared with controls, the significance was set as *p ≤ 0.05; **p ≤ 0.01