RESUMEN
Objective:To investigate the effects of exosomes of human nucleus pulposus cells (NPCs) on the differentiation of urine derived stem cells (USCs) into nucleus pulposus-like cells.Methods:USCs and NPCs were isolated and cultured in vitro. The exosomes of NPCs were extracted and detected by Western-blot. USCs cytoplasm was transfected with GFP lentivirus, while nucleus was transfected with DAPI dye. The NPCs exosomes were transfected with PKH26 dye. After co-incubation for 12 h, USCs and NPCs exosomes were observed by macroscopy. USCs differentiation was induced by NPCs exosomes and non-contact co-culture methods. The relative expression of marker gene mRNA of nucleus pulposus cells in each group and the absorbance at 450 nm wavelength were detected.Results:The isolated USCs had the ability to differentiate into osteocytes, adipocytes and chondrocytes with high expression of marker CD29 (99.57%), CD44 (97.46%) and CD73 (97.71%) and with low expression of negative proteins CD31 (0.59%) and CD45 (0.19%). The isolated NPCs highly expressed nuclear pulposus cell marker COL2A1, ACAN and SOX-9. The exosomes extracted from NPCs showed high expression of exosome marker CD63, CD81 and Tsg101. After 12 h co-incubation, NPCs exosomes fused with USCs membrane and appeared in the cytoplasm of USCs. At 3, 5 and 7 days of co-culture, the absorbance value of USCs cells in exosome group (0.44±0.004, 0.76±0.004, 0.82±0.006) was higher than that in co-culture group (0.39±0.022, 0.63±0.035, 0.69±0.012) ( P<0.05). The mRNA relative expression of USCs nucleus pulposus marker genes ACAN (1.80±0.31, 3.50±0.21, 5.35±0.31, 7.46±0.12), COL2A1 (1.43±0.15, 4.33±0.23, 6.89±0.22, 8.11±0.31), SOX-9 (2.21±0.13, 3.13±0.11, 3.96± 0.14, 4.52±0.26) and HIF-1α (1.45±0.16, 2.14±0.21, 4.31±0.41, 4.01±0.25) in exosomes group were significantly higher than those in the control group ( P<0.05) at the 3rd, 7th, 14th and 21st days. The mRNA relative expression of USCs nucleus pulposus marker genes ACAN (5.69±0.21, 6.69±0.13), COL2A1 (6.33±0.17, 7.89±0.15), SOX-9 (4.19±0.29, 4.38±0.12), HIF-1α (4.49±0.32, 4.96±0.26) in exosomes group were significantly higher than those ACAN (3.69±0.35, 5.13±0.23), COL2A1 (3.40±0.16, 6.79±0.19), SOX-9 (2.26±0.32, 3.69±0.26), HIF-1α (2.39±0.11, 3.96±0.13) in non-contact co-culture group ( P<0.05) at the 14th and 21st days. Conclusion:Human nucleus pulposus exosomes could induce differentiation of human USCs into nucleus pulposus-like cells in vitro. Compared with non-contact co-culture, exosomes have higher induction efficiency and can better maintain the proliferation activity of nucleus pulposus-like cells