Abstract:

Objective To investigate the efficency of Toll-like receptor 3 （TLR3） activation in the human umbilical cord mesenchymal stem cells（hUC-MSCs） transplantation for the treatment of lupus nephritis （LN）， and to preliminariy clarify its mechanism. Methods The hUC-MSCs were cultured and identified， and treated with 10 mg·L^－1 polyinosinic acid. A total of 45 MRL/Lpr female mice were randomly divided into model group， hUC-MSCs group， and TLR3+hUC-MSCs group，and another 15 C57BL/6C female mice were selected as control group；the mice were the injected with hUC-MSCs or polyinosinic acid-treated hUC-MSCs via tail vein. After administration， the levels of 24 h urine protein of the mice were measured every two weeks； the blood sample and kidney tissue were collected after 8 weeks，and the levels of anti-double stranded DNA（anti-dsDNA） antibody in serum and the levels of tumor necrosis factor-α （TNF-α）， interleukin-1β （IL-1β）， interleukin-6（IL-6）， and interleukin-17（IL-17） in kidney tissue of the mice in various groups were detected by enzyme linked immunosorbent assay（ELISA） method. HE staining and PAS staining were used to observe the pathomorphology of kidney tissue； immunofluorescence staining was used to detect the deposition of IgG and complement C3 in kidney tissue. Western blotting method was used to detect the expression levels of protein kinase B （Akt）， mammalian target of rapamycin （mTOR） and autophagy-related proteins in kidney tissue of the mice in various groups. Results The hUC-MSCs had typical mesenchymal stem cell characteristics. Compared with control group， the level of anti-dsDNA antibody in serum of the mice in model group was significantly increased （P<0.05），the levels of TNF-α， IL-1β， IL-6 and IL-17 in kidney tissue were significantly increased （P<0.05）， and there were glomerular mesangial cell proliferation， renal tubular atrophy and necrosis， and inflammatory cell infiltration in kidney tissue； IgG and C3 deposition in glomerulus was obvious （P<0.05）， and the expression levels of Akt and mTOR proteins in kidney tissue were significantly increased （P<0.05），while the expression levels of microtubule-assaciated protein 1 light chain 3 Ⅱ（LC3Ⅱ） and Beclin1 proteins were significantly decreased （P<0.05）. Compared with model group， the level of 24 h urine protein of the mice in TLR3+hUC-MSCs group was significantly reduced at 4 weeks of administration（P<0.05）， and the levels of 24 h urine protein of the mice in hUC-MSCs group and TLR3+hUC-MSCs group were significantly decreased at 6 and 8 weeks of administration（P<0.05）；and the levels of anti-dsDNA antibody in serum of the mice in hUC-MSCs group and TLR3+hUC-MSCs group were significantly decreased （P<0.05）；the levels of TNF-α， IL-1β， IL-6 and IL-17 in kidney tissue were significantly decreased （P<0.05）， the lesion of kidney tissue was improved to a certain extent， the depositions of IgG and C3 in kidney tissue were reduced （P<0.05）， and the improvement effect in TLR3+hUC-MSCs group was more significant； the expression levels of Akt and mTOR proteins in kidney tissue of the mice in hUC-MSCs group and TLR3+hUC-MSCs group were significantly decreased （P<0.05）， and the expression levels of LC3Ⅱ and Beclin1 proteins were significantly increased （P<0.05）. Compared with hUC-MSCs group， the expression levels of LC3Ⅱ and Beclin1 proteins in kidney tissue of the mice in TLR3+hUC-MSCs group were significantly increased （P<0.05）. Conclusion TLR3 can enhance the effect of hUC-MSCs transplantation in the treatment of LN in the mice， and inhibit kidney tissue inflammation and regulate the level of autophagy.

Key words: Toll-like receptor 3, Umbilical cord mesenchymal stem cells, Lupus nephritis, Mice