[New mechanisms and recent insights in the pathogenesis of acute kidney injury (AKI)]. / Nuovi meccanismi e recenti acquisizioni nella patogenesi del danno renale acuto.

Acute kidney injury (AKI) is a frequent complication in hospitalized patients often associated with multiple organ failure, increased mortality and progression toward chronic kidney disease. The identification of new cellular and molecular targets involved in AKI may lead to an improvement of diagnostic and therapeutic approaches. In recent years, the pathogenetic mechanisms of AKI have been fully elucidated: tubular epithelial cells and endothelial cells present in the microvasculature have been identified as the main targets of ischemia and of nephrotoxic drugs. Indeed, endothelial cell injury is associated with an extension phase of AKI, whereas tubular cells are subjected to an alteration of cell polarity, mislocalization of tight junction proteins and membrane transporters, and finally to the development of necrosis or apotosis. Apoptosis, or programmed cell death, is also a key component of sepsis-associated AKI in which the mechanisms of tissue damage are associated not only with hypoperfusion but also with a direct detrimental effect of bacterial products and inflammatory mediators on resident kidney cells. Endothelial and tubular epithelial cells also represent the main targets in the immunological mechanisms of AKI in kidney transplantation during cell-mediated and antibody-mediated rejection. Recent studies evidenced new molecules as early biomarkers of AKI. Among these molecules, NGAL and KIM-1 play a possible role in the progression toward chronic kidney disease. Lastly, the new frontier of AKI therapy is represented by the use of bone marrow-derived mesenchymal stem cells able to induce a regenerative program in the damaged kidney.

Human liver stem cell-derived extracellular vesicles enhance cancer stem cell sensitivity to tyrosine kinase inhibitors through Akt/mTOR/PTEN combined modulation.

It is well recognized that Cancer Stem Cells (CSCs) sustain the initiation, the maintenance and the recurrence of tumors. We previously reported that extracellular vesicles (EVs) derived from human liver stem cells (HLSCs) were able to limit tumor development. In this study, we evaluated whether EV derived from HLSCs could act in synergy with tyrosine kinase inhibitors (TKIs) on apoptosis of CSCs isolated from renal carcinomas. For this purpose, we administered to renal CSCs, HLSC-EVs and TKIs, as co-incubation or sequential administration. We found that HLSC-EVs in combination with Sunitinb or Sorafenib significantly increased renal CSCs apoptosis induced by low TKI dose. At variance, no synergistic effect was observed when bone marrow mesenchymal stem cell-derived EVs were used. In particular, renal CSCs chemosensitivity to TKIs was enhanced when HLSC-EVs were either co-administered with TKIs or added after, but not before. CSC apoptosis was also incremented at a percentage comparable to that of co-administration when TKIs were loaded in HLSC-EVs. By a mechanistic point of view, Akt/mTOR and Erk and Creb intracellular pathways, known to be pivotal in the induction of tumor growth and survival, appeared modulated as consequence of TKIs/HLSC-EVs co-administration. Together, our results indicate that the synergistic effect of HLSC-EVs with TKIs may increase the response to TKIs at low doses, providing a rational for their combined use in the treatment of renal carcinoma.

Charge-based precipitation of extracellular vesicles.

Vesicular-mediated communication between cells appears critical in many biological processes. Extracellular vesicles (EVs) released from healthy and diseased cells are involved in a network of exchange of biologically active molecules. Since EVs present in biological fluids carry the signature of the cell of origin, they are potential biomarkers for ongoing physiological or pathological processes. Despite the knowledge on EV biology accrued in recent years, techniques of EV purification remain a challenge and all the described methods have some advantages and disadvantages. In the present study, we described a method based on charge precipitation of EVs from biological fluids and from cell supernatants in comparison with the differential ultracentrifugation, which is considered the gold standard for EV purification. The analysis of ζ­potential revealed that EVs have a negative charge that allows the interaction with a positively charged molecule, such as protamine. Protamine was shown to induce EV precipitation from serum and saliva and from cell culture media without the need for ultracentrifugation. EV resuspension was facilitated when protamine (P) precipitation was performed in the presence of PEG 35,000 Da (P/PEG precipitation). The recovery of precipitated EVs evaluated by NanoSight analysis was more efficient than that obtained by ultracentrifugation. By electron microscopy the size of EVs was similar after both methods were used, and the expression of CD63, CD9 and CD81 exosomal markers in the P/PEG­precipitated EVs indicated an enrichment in exosomes. The RNA recovery of P/PEG­precipitated EVs was similar to that of EVs isolated by ultracentrifugation. In addition, P/PEG­precipitated EVs retained the biological activity in vitro as observed by the induction of wound closure by keratinocytes and of proliferation of tubular epithelial cells. In conclusion, charge-based precipitation of EVs has the merit of simplicity and avoids the requirement of expensive equipments and may be used for the efficient isolation of EVs from small biological samples.

Isolation, characterization and potential role in beta cell-endothelium cross-talk of extracellular vesicles released from human pancreatic islets.

The cross-talk between beta cells and endothelium plays a key role in islet physiopathology and in the revascularization process after islet transplantation. However, the molecular mechanisms involved in this cross-talk are not fully elucidated. Extracellular vesicles (EVs) are secreted membrane nanoparticles involved in inter-cellular communication through the transfer of proteins and nucleic acids. The aims of this study were: 1) isolation and characterization of EVs from human islets; 2) evaluation of the pro-angiogenic effect of islet-derived EVs on human islet endothelial cells (IECs). EVs were isolated by ultracentrifugation from conditioned medium of human islets and characterized by nanotrack analysis (Nanosight), FACS, western blot, bioanalyzer, mRNA/microRNA RT-PCR array. On IECs, we evaluated EV-induced insulin mRNA transfer, proliferation, resistance to apoptosis, in vitro angiogenesis, migration, gene and protein profiling. EVs sized 236±54 nm, expressed different surface molecules and islet-specific proteins (insulin, C-peptide, GLP1R) and carried several mRNAs (VEGFa, eNOS) and microRNAs (miR-27b, miR-126, miR-130 and miR-296) involved in beta cell function, insulin secretion and angiogenesis. Purified EVs were internalized into IECs inducing insulin mRNA expression, protection from apoptosis and enhancement of angiogenesis. Human islets release biologically active EVs able to shuttle specific mRNAs and microRNAs (miRNAs) into target endothelial cells. These results suggest a putative role for islet-derived EVs in beta cell-endothelium cross-talk and in the neoangiogenesis process which is critical for engraftment of transplanted islets.