To explore whether ultrasound microbubble destruction promotes recovery of the kidney in acute tubular necrosis (ATN) in rats.

ATN model was induced in forty Sprague-Dawley (SD) rats. Forty SD rats were randomly divided into the following groups after the establishment of animal models of ATN injury (n=10): (1) Model group alone (control group); (2) 1.0 W/cm² US+MB (US/MB group), Bubble (0.5 ml)+ 1.0 W/cm² US; (3) MSCs group ; (4) 1.0 W/cm² US+MB + MSCs group (US/MB + MSCs group). 0.5 ml infusion of microbubbles via the contralateral femoral vein were infused at days 1 and 3 after ATN. Simultaneous insonation was started at the lower back region of rats, using an ultrasound gene transfection treatment meter with the following settings: insonate for 5 s at 1 MHz and 1.0 W/cm² with a 5 s pause, totaling 60 s in US/MB group and US/MB + MSCs group. US/MB + MSCs group received an infusion of rat MSCs (2×10⁶ in 1 ml saline) via the contralateral femoral vein at 1 minute after US/MB at 3 days after ATN. Simultaneousin MSCs group, a concentration of 2×10⁶ in 1 ml saline were infused via the contralateral femoral vein at 3 days after ATN. Control group received no treatment. The rats were killed and their kidneys were excised at 7 days after MSCs transplantation. Western blotting was applied to determine hepatocyte growth factor (HGF) and epidermal growth factor (EGF). Histologicalexamination wasperformed to evaluate the extent of tubular necrosis. Statistical significances of the level of HGF and EGF expression and the extent of tubular necrosis were determined by one-way ANOVA followed by Student-Newman-Keuls-q for the comparison between two groups.

The special band of 83 kilodalton (KD) was found in all groups. A prominent band consistent with HGF was seen in the US/MB +MSCs group. Special band of 6 KD was found in all groups. A prominent band consistent with EGF was seen in the US/MB +MSCs group. Western blotting results showed that the levels of HGF protein expression were (0.16±0.30), (0.35±0.50), (0.37±0.50) and (0.70±0.60), respectively. The levels of EGF protein expression were (0.19±0.40), (0.41±0.50), (0.43±0.50) and (0.82±0.70), respectively. The extent of tubular necrosis and dilation were (4.1±0.8), (3.6±0.6), (1.8±0.4) and (1.0±0.3), respectively. The levels of HGF protein were higher in the US/MB +MSCs group compared with those of the control group, US/MB group and MSCs group, respectively (q=23.6, q=18.7 and q=9.6, P<0.05). The levels of EGF were higher in the US/MB +MSCs group compared with those of the control group, US/MB group and MSCs group, respectively (q=21.8, q=17.1 and q=9.3, P<0.05). The extent of tubular necrosis and dilation was milder in the US/MB +MSCs group compared with those of the control group, US/MB group and MSCs group, respectively (q=20.1, q=16.7 and q=6.9, P<0.05). The extent of tubular necrosis and dilation was significantly milder in the US/MB + MSCs group than those of all other groups.

Microbubble destruction by 1.0 W/cm² ultrasound can promote both the homing of mesenchymal stem cells to kidney tissue and the recovery of the kidney in ATN in rats, which provide a novel and efficient approach for cellular therapy.