Objective: To investigate the effect of adipose-derived stem cells (ADSC) on renal injury in mice with burn injury and sepsis and its underlying mechanism.
Methods: (1) Adipose tissue was collected from both inguinal regions of 5 C57BL/6J mice to isolate, culture and purify ADSC through enzyme digestion, density gradient centrifugation, and adherence method. Cells of the third passage were used in the experiment. The morphologic change in cells was observed and the growth curve of cells was determined. The expression of cell surface antigen phenotype was analyzed by flow cytometry, and the cells were identified by adipogenic and osteogenic differentiation. (2) Another 37 C57BL/6J mice were divided into normal control group (n = 5), saline group (n = 16), and group ADSC (n = 16) according to the random number table. The mice in saline group and group ADSC were injected with Pseudomonas aeruginosa after being subjected to 15% TBSA full-thickness burn on the back to reproduce septic burn model. Then the mice were injected with saline and ADSC through tail vein respectively. At post burn hour (PBH) 12, 24, 48, and 72, the pathological change in kidney tissue was observed, the levels of blood urea nitrogen and serum creatinine were determined, and the levels of TNF-α, IL-12, IL-10, and cyclooxygenase-2 (COX2) mRNA were determined with real-time fluorescence quantitative PCR in both groups. Above-mentioned indexes were also examined in the normal control group (without burn). Data were processed with multifactor analysis of variance and LSD- t test.
Results: (1) Cells in the third passage were orderly arranged with the shape similar to fibroblasts. The percentages of CD90(+), CD105(+), CD34(-), and CD45(-) cells were all above 90%. The cells could differentiate into osteoblasts and adipocytes. The cells were identified to be ADSC. (2) From PBH 12 to PBH 72, the neutrophil infiltration gradually increased, and the structure of kidney tubules and glomeruli were deranged in saline group. The pathological change in kidney tissue in group ADSC was less serious than that of normal control group at each time point. From PBH 12 to PBH 72, the levels of blood urea nitrogen and serum creatinine in saline group were significantly higher than those of normal control group and group ADSC (P values all below 0.01). Compared with those of the normal control group, the levels of TNF-α and IL-12 mRNA were higher in group ADSC and saline group at PBH 24 (P values all below 0.05). At PBH 24, the level of TNF-α mRNA in group ADSC (1.58 ± 0.19) was lower than that of saline group (3.36 ± 0.30, P < 0.05). At PBH 24, the levels of IL-10 and COX2 mRNA in group ADSC (2.89 ± 0.47, 4.90 ± 0.59) were higher than those in normal control group (1.00 ± 0.15, 1.00 ± 0.27) and saline group (1.32 ± 0.38, 1.57 ± 0.38, P values all below 0.05).
Conclusions: ADSC can decrease the levels of blood urea nitrogen and serum creatinine, promote the production of anti-inflammatory cytokines IL-10 and COX2, and reduce the release of the pro-inflammatory cytokines TNF-α and IL-12 to offer protective effects against renal injury in burn mice with sepsis.