INTRODUCTION AND AIMS: It has been demonstrated that the administration of mesenchymal stem cells (MSCs) improves the recovery of acute kidney injury (AKI). Paracrine mechanisms have been involved in MSCs-induced recovery of damaged kidney. Microvesicles (MVs) released by MSCs were shown to trigger functional and regenerative events via a horizontal transfer of mRNA. Recently, we demonstrated the presence of a cell population (Gl-MSC) expressing both MSC and renal stem cell markers in adult human-decapsulated glomeruli that is capable to differentiate in endothelial and epithelial cells, suggesting a potential role in the physiological cell turnover and/or in response to kidney injury. In the present study we aimed to investigate whether MVs derived from Gl-MSCs may contribute to AKI recovery in a murine model of ischemia-reperfusion (I/R) injury. METHODS: Severe combined immunodeficient (SCID) mice were divided into two groups (n= 8/group) and treated with 15 mg/proteins of MVs or vehicle alone (CTL). I/R was induced in anesthetized mice by clamping the left renal pedicle for 35 minutes. The right kidney was subsequently removed. All treatments were administered intravenously immediately after surgery. Mice were sacrificed at 48 h after surgery and the blood samples collected at this time were used to measure plasma creatinine. To compare the changes in renal histology, luminal casts and tubular necrosis were assessed in 5 µm-thick paraffin-fixed sections. Tubular cell proliferation and apoptosis were detected using monoclonal antibodies anti-BrdU, anti-PCNA and with TUNEL assay, respectively. RESULTS: Gl-MSC-derived MVs improved renal function 48 h after I/R injury (plasma creatinine: 0.6±0.2 vs 1.4±0.4; MVs vs CTL, respectively). The quantitative evaluation of casts and tubular necrosis showed a reduction in MV-treated group compared to CTL group (casts n/HPF: 1.7±0.7 vs 3.8±1.9; tubular necrosis n/HPF: 8.9±1.2 vs 11.7±2). In addition, we found a significant increase of tubular cell proliferation in mice treated with MVs compared to the CTL group (PCNA positive cells n/HPF: 23.3±3.3 vs 12.4±1.2 and BrdU positive cells n/HPF 14.8±1.9 vs 7±2). No differences were demonstrated in the number of apoptotic cells. CONCLUSIONS: The results of the present study indicate that the treatment with Gl-MSC-derived MVs improves the recovery from ischemia-reperfusion-induced injury by promoting tubular cell proliferation.
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