PINK1 Kinase Enhances the Repair Effects of Bone Marrow Mesenchymal Stem Cells on Renal Ischemia/Reperfusion-Induced Acute Kidney Injury in Mice

Background: Acute kidney injury (AKI) is a common severe acute syndrome caused by multiple causes, which is characterized by a rapid decline of renal function in a short period. Bone mesenchymal stem cells (BMSCs) are effective in the treatment of AKI. However, it remains unclear about the mechanism of their beneficial effects. PENT-induced kinase 1 (PINK1) may play an important role in the kidney tissue repair. In this study, an endeavor would be made to explore the enhancing effect of PINK1 overexpression on the repair of AKI through BMSCs. Methods: In this study, the ischemia/reperfusion-induced acute kidney injury (IRI-AKI) in mice and the hypoxia-reoxygenation model of cells were established, and the indexes were detected by pathology and immunology experimental.Results: After ischemia/reperfusion, compared with the BMSCs group, the OE PINK1 group had a decreased expression of BUN, the mitigated renal fibrosis , the reduced tissue damage degree. Overexpressed PINK1 could decrease the inflammatory reaction of injured kidney tissues in IRI-AKI mice, the decreased expression of IL-10 in peripheral blood serum; and regulate the distribution of immune cells in the kidney during IRI, the decreased infiltration of lymphocytes, the increased infiltration of macrophages; and reduce the stress response of BMSCs under hypoxia and inflammation; and enhance the stress response of BMSCs to renal tubular epithelial cells(RTECs) under hypoxia and inflammation, the decreased apoptosis rate of RTECs, the decreased release of TNF-α in the cell supernatant, and the decreased proliferation of PBMCs in peripheral blood after hypoxia and reoxygenation; and regulate the autophagy of BMSCs in kidney tissues with IRI-AKI to better repair the injured kidney tissues, the increased expression of LC3-B related to autophagy and the decreased expression of mTOR.Conclusions: In this study, PINK1 overexpression enhances the repair effect of BMSCs on IRI-AKI, and the distribution of injured renal immune cells during IRI regulation by BMSCs. Besides, PINK1 enhances BMSCs and their resistance to the stress response of RTECs under hypoxia and inflammation. In addition, it regulates mitophagy during IRI-AKI. The findings of this study provide a new direction and target for the repair of IRI-AKI through BMSCs.

Delayed Contralateral Nephrectomy Halted Post-Ischemic Renal Fibrosis Progression and Inhibited the Ischemia-Induced Fibromir Upregulation in Mice

(1) Background: Ischemia reperfusion (IR) is the leading cause of acute kidney injury (AKI) and results in predisposition to chronic kidney disease. We demonstrated that delayed contralateral nephrectomy (Nx) greatly improved the function of the IR-injured kidney and decelerated fibrosis progression. Our aim was to identify microRNAs (miRNA/miR) involved in this process. (2) Methods: NMRI mice were subjected to 30 min of renal IR and one week later to Nx/sham surgery. The experiments were conducted for 7–28 days after IR. On day 8, multiplex renal miRNA profiling was performed. Expression of nine miRNAs was determined with qPCR at all time points. Based on the target prediction, plexin-A2 and Cd2AP were measured by Western blot. (3) Results: On day 8 after IR, the expression of 20/1195 miRNAs doubled, and 9/13 selected miRNAs were upregulated at all time points. Nx reduced the expression of several ischemia-induced pro-fibrotic miRNAs (fibromirs), such as miR-142a-duplex, miR-146a-5p, miR-199a-duplex, miR-214-3p and miR-223-3p, in the injured kidneys at various time points. Plexin-A2 was upregulated by IR on day 10, while Cd2AP was unchanged. (4) Conclusion: Nx delayed fibrosis progression and decreased the expression of ischemia-induced fibromirs. The protein expression of plexin-A2 and Cd2AP is mainly regulated by factors other than miRNAs.

Role of mesenchymal stromal cells and their secretory products in kidney regeneration

Kidney diseases are an important medical problem. Kidney injuries are accompanied by oxidative stress, cell death, capillary destruction, inflammation and fibrosis. Mesenchymal stromal cells (MSCs) have a complex effect on the regeneration by producing various regulatory molecules, including those inside extracellular vesicles, and therefore are considered as a promising therapeutic resource for cell therapy of kidney diseases. Their renoprotective effect has been shown in different experimental models, but the results of the clinical trials are ambiguous. Clinical use of MSCs is complicated by their low survival rate in the injured kidney, potential immunogenicity, tumorogenicity and fibrogenicity. Cell-free therapy with the secretory products of MSCs such as conditioned environments or extracellular vesicles is a promising direction for using their regenerative potential. However, introduction of MSCs and their secretory products into medical practice requires further research into the mechanisms of their proregenerative action, improvement of cultivation protocols, and more clinical trials.

New Aspects of the Kidney in the Regulation of Fibroblast Growth Factor 23 (FGF23) and Mineral Homeostasis

The bone-derived hormone fibroblast growth factor 23 (FGF23) acts in concert with parathyroid hormone (PTH) and the active vitamin D metabolite calcitriol in the regulation of calcium (Ca) and phosphate (P) homeostasis. More factors are being identified to regulate FGF23 levels and the endocrine loops between the three hormones. The present review summarizes the complex regulation of FGF23 and the disturbed FGF23/Klotho system in chronic kidney disease (CKD). In addition to the reduced ability of the injured kidney to regulate plasma levels of FGF23, several CKD-related factors have been shown to stimulate FGF23 production. The high circulating FGF23 levels have detrimental effects on erythropoiesis, the cardio-vascular system and the immune system, all contributing to the disturbed system biology in CKD. Moreover, new factors secreted by the injured kidney and the uremic calcified vasculature play a role in the mineral and bone disorder in CKD and create a vicious pathological crosstalk.

P0546EARLY, BUT NOT LATE, CONTRALATERAL NEPHRECTOMY OVERCOMES PROGRESSION TO CKD AFTER UNILATERAL ISCHEMIC INJURY

Background and Aims It is increasingly clear that acute kidney injury (AKI) can result in the development of chronic kidney disease (CKD) in humans. Murine renal unilateral ischemia-reperfusion injury (UIRI) models this AKI-to-CKD progression in the injured kidney in the presence of its healthy counterpart (Le Clef et al, Plos One 2016). In mice, we and others demonstrated that contralateral nephrectomy (Nx), when performed shortly after UIRI (i.e. 3 days), is able to significantly attenuate the progression to CKD. Although non-translatable, Nx can be considered an experimental therapeutic intervention that incites inherent physiological recovery mechanisms in the kidney. Here, we investigate in rats to what extent contralateral Nx is able to attenuate or revert CKD progression when performed well beyond the acute injury phase, i.e. with increased Nx delay time after UIRI. Method AKI was induced in male Wister rats by left UIRI for 60 min at 35°C core body temperature after which contralateral Nx was performed 3, 10 or 20 days later, or no Nx was performed. Control animals underwent sham-UIRI and sham-Nx 3 days later. Renal function was assessed by serum creatinine and transcutaneous GFR measurement 24h and 72h after Nx and weekly thereafter. Rats were euthanized 11 weeks after Nx. Kidneys were weighed and histology was evaluated by PAS stain for overall morphology and Sirius Red stain for interstitial fibrosis. Results When no Nx was performed, renal function of the injured kidney decreased 44% compared to control animals at week 11. Nx at day 3 induced full functional recovery from week 5 after Nx on, whereas Nx at day 10 and 20 both lead to a persistent 20% loss of renal function at week 9 after Nx (p<0.05). Nx at day 3 was able to attenuate renal atrophy and fibrotic tubulointerstitial expansion. Nx at day 10 and 20 were less efficient and led to 1.6 (p>0.05) and 2.6 (p<0.05) fold increase of tubulointerstitial area compared to controls. Nx at day 3 and 10 induced a significant increase in renal mass-to-body weight ratio compared to control from 2.9±0.1 mg/g (control) to 4.6±0.4 mg/g (day 3) and 4.8±0.3 mg/g (day 10) respectively. When Nx was performed at day 20 or no Nx was performed, renal mass-to-body weight ratio did not differ significantly from control animals, however, parallel with renal function, histopathology was considerably worse. Conclusion Early contralateral Nx after UIRI rescues renal function and morphology, whereas delayed Nx does not allow full recovery of the injured kidney. There was no additional functional loss when Nx was performed on day 20 versus day 10, though, histopathology aggravated. These results imply that a damaged kidney loses its intrinsic (compensatory) recovery potential over time and that an early intervention is crucial for averting CKD outcome after AKI.

Post-Ischemic Renal Fibrosis Progression Is Halted by Delayed Contralateral Nephrectomy: The Involvement of Macrophage Activation

(1) Background: Successful treatment of acute kidney injury (AKI)-induced chronic kidney disease (CKD) is unresolved. We aimed to characterize the time-course of changes after contralateral nephrectomy (Nx) in a model of unilateral ischemic AKI-induced CKD with good translational utility. (2) Methods: Severe (30 min) left renal ischemia-reperfusion injury (IRI) or sham operation (S) was performed in male Naval Medical Research Institute (NMRI) mice followed by Nx or S one week later. Expression of proinflammatory, oxidative stress, injury and fibrotic markers was evaluated by RT-qPCR. (3) Results: Upon Nx, the injured kidney hardly functioned for three days, but it gradually regained function until day 14 to 21, as demonstrated by the plasma urea. Functional recovery led to a drastic reduction in inflammatory infiltration by macrophages and by decreases in macrophage chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α) mRNA and most injury markers. However, without Nx, a marked upregulation of proinflammatory (TNF-α, IL-6, MCP-1 and complement-3 (C3)); oxidative stress (nuclear factor erythroid 2-related factor 2, NRF2) and fibrosis (collagen-1a1 (Col1a1) and fibronectin-1 (FN1)) genes perpetuated, and the injured kidney became completely fibrotic. Contralateral Nx delayed the development of renal failure up to 20 weeks. (4) Conclusion: Our results suggest that macrophage activation is involved in postischemic renal fibrosis, and it is drastically suppressed by contralateral nephrectomy ameliorating progression.