Apparent Diffusion Coefficient is a Useful Biomarker for Monitoring Adipose-Derived Mesenchymal Stem Cell Therapy of Renal Ischemic-Reperfusion Injury

Purpose: This study aimed to investigate the potential of apparent diffusion coefficient (ADC) for monitoring adipose-derived mesenchymal stem cell (ADMSC) therapy of renal ischemic-reperfusion injury (IRI). Procedures: After baseline magnetic resonance imaging (MRI), 36 Sprague-Dawley rats with bilateral renal IRI were divided equally as groups 1, 2, and 3 (non-treated rats) and groups 4, 5, and 6 (ADMSC-treated rats, with 2 million ADMSCs injected via the tail vein at 6 h after IRI). Groups 1 and 4, 2 and 5, and 3 and 6 were euthanized at days 1, 3, and 7, respectively, after renal MRI. The ratios of ADC at different time points to baseline values in the cortex, outer, and inner stripes of outer medulla (OSOM/ISOM), assessments of monocyte chemoattractant protein-1 (MCP-1), CD68+ cells, tubular cast formation, and degree of fibrosis in three zones over time were compared between the non-treated and ADMSC-treated rats. Results: Among three zones, the differences in cortical ADC and immunohistochemical changes between the non-treated and ADMSC-treated IRI rats over time were less obvious. Compared with the non-treated rats, the ADMSC-treated rats exhibited significantly higher ADC ratios of OSOM and ISOM at days 1 and 3 corresponding to significantly less MCP-1 staining, CD68+ cells, and tubular casts. From day 3 to day 7, coupling with the decrement of MCP-1 and CD68+ cells in IRI kidneys, the effect of cell density on ADC declined. By day 7, the ADMSC-treated rats showed significantly higher ADC ratios of ISOM than the non-treated IRI rats, indicating better recovery, which could be related to significantly fewer tubular casts and marked amelioration of fibrosis. Conclusions: We suggest ADC is a useful in vivo biomarker for monitoring ADMSC therapy of renal IRI.