Contrast-induced acute kidney injury (CI-AKI) occurs in more than 30% of patients after intravenous iodinated contrast media and causes serious complications, including renal failure and mortality. Recent research has demonstrated that routine antioxidant and alkaline therapy failed to show benefits in CI-AKI patients with high risk for renal complications. Mitophagy is a mechanism of selective autophagy, which controls mitochondrial quality and mitochondrial reactive oxygen species (ROS) through degradation of damaged mitochondria. The role of mitophagy and its regulation of apoptosis in CI-AKI are poorly understood. In this study, we demonstrated that mitophagy was induced in renal tubular epithelial cells (RTECs) during CI-AKI, both in vivo and in vitro . Meanwhile, contrast media–induced mitophagy was abolished when silencing PINK1 or PARK2 (Parkin), indicating a dominant role of the PINK1-Parkin pathway in mitophagy. Moreover, mitochondrial damage, mitochondrial ROS, RTEC apoptosis, and renal injury under contrast exposure were more severe in PINK1- or PARK2-deficient cells and mice than in wild-type groups. Functionally, PINK1-Parkin–mediated mitophagy prevented RTEC apoptosis and tissue damage in CI-AKI through reducing mitochondrial ROS and subsequent NLRP3 inflammasome activation. These results demonstrated that PINK1-Parkin–mediated mitophagy played a protective role in CI-AKI by reducing NLRP3 inflammasome activation.

Cartilage defects are one of the most common symptoms of osteoarthritis (OA), a degenerative disease that affects millions of people world-wide and places a significant socio-economic burden on society. Hydrogels, which are a class of biomaterials that are elastic, and display smooth surfaces while exhibiting high water content, are promising candidates for cartilage regeneration. In recent years, various kinds of hydrogels have been developed and applied for the repair of cartilage defects in vitro or in vivo , some of which are hopeful to enter clinical trials. In this review, recent research findings and developments of hydrogels for cartilage defects repair are summarized. We discuss the principle of cartilage regeneration, and outline the requirements that have to be fulfilled for the deployment of hydrogels for medical applications. We also highlight the development of advanced hydrogels with tailored properties for different kinds of cartilage defects to meet the requirements of cartilage tissue engineering and precision medicine.

Background: Mesenchymal stem cells (MSCs) can be isolated from various tissues and can present themselves as a promising cell source for cell-based therapies. Although adipose- and bone marrow–derived mesenchymal stem cells have already been used in a considerable number of clinical trials for osteoarthritis treatment, systematic analyses from single- to bulk-cell resolution as well as clinical outcomes of these 2 MSCs are still insufficient. Purpose: To explore the characteristics and differences of adipose-derived stem cells (ADSCs) and bone marrow MSCs (BMSCs) at single- and bulk-cell levels, to study the clinical outcomes of these 2 cells on the treatment of osteoarthritis, and to provide potential guidance on the more precise clinical application of these MSCs. Study Design: Controlled laboratory study and meta-analysis. Methods: Same donor–derived ADSCs and BMSCs were isolated and cultured. Single- and bulk-cell assays were used to identify the characteristics of these 2 cells. Meta-analysis of clinical trials was done to compare the clinical therapeutic effects in osteoarthritis treatment with ADSCs and BMSCs. Results: Single-cell RNA sequencing analysis showed that the population of ADSCs showed lower transcriptomic heterogeneity when compared with BMSCs. Additionally, as compared with BMSCs, ADSCs were less dependent on mitochondrial respiration for energy production. Furthermore, ADSCs had a lower expression level of human leukocyte antigen class I antigen and higher immunosuppression capacity when compared with the BMSC population. Meta-analysis of current clinical trials of osteoarthritis treatment with MSCs consistently showed that ADSCs are more stable than BMSCs in their therapeutic effect. Conclusion: These results provide basic biological insights into human ADSCs and BMSCs at the single-cell resolution. Findings indicated that ADSCs may be a more controllable stem cell source, may be more adaptable to surviving in the hypoxic articular cavity niche, and may exhibit superiority in regulating inflammation. Based on the meta-analysis results of the different characteristics of ADSCs and BMSCs, ADSCs were implicated as being a better cell source for osteoarthritis treatment. Clinical Relevance: These results guide a more precise clinical application of adipose and bone marrow mesenchymal stem cells.

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Ni (2020): Inhibiting NLRP3 inflammasome attenuates apoptosis in contrast-induced acute kidney injury through the upregulation of HIF1A and BNIP3-mediated mitophagy, Autophagy,

Contrast-induced acute kidney injury (CI-AKI) is a serious complication in patients after administration of iodinated contrast media and is associated with a significant high risk for severe renal failure and death due to the wholesale necrosis of the tubules and interstitial inflammation. Pyroptosis is a form of programmed lytic cell death that is triggered by inflammatory caspases, but little is known about its role in tubular epithelial cell (TEC) death and contrast-induced acute kidney injury. Here we show that systemic exposure to contrast media causes severe tubular epithelial pyroptosis that is mediated by the inflammatory caspases, caspases 4/5 in human TECs, or the murine homolog caspase-11 in mice in vivo and in mouse TECs in vitro. Knockdown of caspase-4/5 preserved human TECs from cell death and reduced the release of mature IL-1β, and in caspase-11-deficient mice, contrast-induced acute kidney injury was abrogated, indicating a central role for caspase-11 in acute kidney injury. In addition, deletion of caspase-11 in TECs reduced Gsdmd cleavage, which is the key process for execution of pyroptosis. These results establish the requisite role of epithelial pyroptosis in contrast-induced acute kidney injury and suggest that epithelial inflammatory caspases are an important therapeutic target for acute kidney injury.

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