Role of mitochondria in endogenous renal repair

Renal ischemia alters the mRNA and miRNA profile of vasculature-related genes in scattered tubular-like cells from female pigs

Scattered tubular-like cells (STCs) are renal tubular cells that survive episodes of renal injury and acquire progenitor-like characteristics to repair other damaged kidney cells. STCs release proangiogenic factors in culture and induce microvascular proliferation in injured murine kidneys in vivo. Renovascular disease (RVD) compromises the reparative capacity of STCs, but the underlying mechanisms remain unknown. We hypothesized that RVD alters the expression of vasculature-related genes in swine STCs and impair their vasculoprotective properties. CD24+/CD133+ STCs were harvested from female pig kidneys after 10 wk of RVD or sham (n = 6 each), and the mRNA profiles of vasculature-related genes were analyzed using mRNA and microRNA seq (n = 3/group). STC expression of candidate differentially expressed (DE) genes and their capacity to induce human umbilical endothelial cells (HUVECs) to form tube-like networks were subsequently assessed in vitro before and after micro-RNA (miRNA) modulation (n = 6 each). mRNA-seq identified 67 upregulated and 42 downregulated vasculature-related genes in RVD-STCs. Four miRNAs were upregulated and 12 downregulated in RVD-STCs and found to target 31.3% to 40.5% of DE vasculature-related genes. Modulation in vitro of representative miRNAs decreased RVD-STC expression of anti-angiogenic and increased expression of proangiogenic target genes, respectively. Furthermore, this restored the ability of STCs to induce HUVEC tube formation on Matrigel that was impaired in RVD. Chronic renal ischemia alters the expression of vasculature-related genes in swine STCs, likely through posttranscriptional mechanisms, impairing their proangiogenic activity. These observations may contribute to develop novel approaches to preserve the reparative capacity of STCs in individuals with RVD.NEW & NOTEWORTHY The intrinsic reparative capacity of the adult mammalian kidney is restricted to the ability of scattered tubular-like cells (STCs) to repair damaged kidney cells. Our study provides evidence that chronic renal ischemia alters the mRNA/miRNA profile of angiogenic/vascular development genes of swine STCs, limiting their potential to repair injured tubular cells. Our observations may assist in developing new therapies to improve renal repair in individuals with chronic renal ischemia.

Morphometric study of proximal tubular cell mitochondria using TEM images in renal diseases

The kidney is rich in mitochondria, and any alterations or damage to tubular cell mitochondria play an important role in renal metabolic activities and the pathogenesis of various kidney diseases. Quantitative analysis of mitochondrial concentration, size, and shape is essential for understanding mitochondrial biology in renal disorders. This study assessed mitochondrial morphometric parameters of the proximal convoluted tubular cell adjacent to the glomerulus in different renal disorders and investigated how they correlated with serum creatinine. A total of 65 kidney biopsy cases received by the transmission electron microscope (TEM) laboratory for diagnosis were included in the study. TEM images of glutaraldehyde-osmium tetroxide fixed epoxy-resin embedded 70 nm thick sections were used for the evaluation of (i) minor axis(MinX) (ii) major axis(MajX) (iii) Area, (iv)Perimeter, (v) Aspect ratio and (vi) Roundness of mitochondria in renal tubular cells using QuPath software. Mitochondrial density (MDensity), % of mitochondrial space (MSpace), and mitochondrial surface density (MSDensity) in the cytoplasm of tubular space were estimated for each sample. Serum creatinine showed good negative correlations with MSpace and MSDensity, and elongation of mitochondria was more in renal disorder in comparison to normal histology, which indicated the variation of mitochondrial concentration and shape in proximal tubular cells could be important features in the renal function disorder.

Astragaloside IV attenuates cadmium induced nephrotoxicity in rats by activating Nrf2

Acute kidney injury (AKI) has become a disease of global concern due to its high morbidity and mortality. This has highlighted the need for renoprotective agents. Astragaloside IV (AS-IV) is a saponin isolated from Astragalus membranaceus with good antioxidant, anti-inflammatory and anti-tumor properties. In this study, HK2 cells and rat model were utilized to explore the protective effect of AS-IV against cadmium chloride-induced oxidative stress-induced apoptosis. CdCl2-induced apoptosis, ROS production, and mitochondrial membrane potential alterations were significantly inhibited in AS-IV -treated HK2 cells. Expression of the mitochondria-associated apoptotic proteins Cleaved-Caspase3, Cleaved-Caspase9, and Cleaved-PARP was significantly reduced after AS-IV intervention. In addition, AS-IV inhibited Rat weight loss and also alleviated the symptoms of CdCl2-induced nephrotoxicity in a rat model of CdCl2-induced kidney injury. Further experiments showed that AS-IV suppresses heavy metal Cd-induced mitochondria-mediated apoptosis by regulating the Nrf2/HO-1 pathway. In conclusion, AS-IV could protect the kidney from heavy metal-induced toxicity and could be used as a nephroprotective agent.

Commentary: the perspectives of harnessing the power of scattered tubular-like cells for renal repair

The commentary discusses the regenerative capacity of the kidneys; recent studies reveal that renal cells can regenerate when exposed to certain conditions. A major focus is on scattered tubular-like cells (STCs), which can dedifferentiate and acquire progenitor-like properties in response to injury. These cells exhibit a glycolytic metabolism, making them resilient to hypoxic conditions and capable of repairing damaged renal tissues. Despite their potential, STCs are difficult to isolate and exist in small numbers. Here we highlight the need for more research into STC function, metabolic profiles, mechanisms limiting STC injury repair capacity, and methods of their pharmacological activation. Understanding these mechanisms could lead to novel therapies for kidney diseases.

Urinary N-acetylglucosaminidase in People Environmentally Exposed to Cadmium Is Minimally Related to Cadmium-Induced Nephron Destruction

Exposure to even low levels of the environmental pollutant cadmium (Cd) increases the risk of kidney damage and malfunction. The body burden of Cd at which these outcomes occur is not, however, reliably defined. Here, multiple-regression and mediation analyses were applied to data from 737 non-diabetic Thai nationals, of which 9.1% had an estimated glomerular filtration rate (eGFR) ≤ 60 mL/min/1.73 m2 (a low eGFR). The excretion of Cd (ECd), and renal-effect biomarkers, namely β2-microglobulin (Eβ2M), albumin (Ealb), and N-acetylglucosaminidase (ENAG), were normalized to creatinine clearance (Ccr) as ECd/Ccr Eβ2M/Ccr, Ealb/Ccr, and ENAG/Ccr. After adjustment for potential confounders, the risks of having a low eGFR and albuminuria rose twofold per doubling ECd/Ccr rates and they both varied directly with the severity of β2-microglobulinuria. Doubling ECd/Ccr rates also increased the risk of having a severe tubular injury, evident from ENAG/Ccr increments [POR = 4.80, p = 0.015]. ENAG/Ccr was strongly associated with ECd/Ccr in both men (β = 0.447) and women (β = 0.394), while showing a moderate inverse association with eGFR only in women (β = -0.178). A moderate association of ENAG/Ccr and ECd/Ccr was found in the low- (β = 0.287), and the high-Cd body burden groups (β = 0.145), but ENAG/Ccr was inversely associated with eGFR only in the high-Cd body burden group (β = -0.223). These discrepancies together with mediation analysis suggest that Cd-induced nephron destruction, which reduces GFR and the tubular release of NAG by Cd, involves different mechanisms and kinetics.