Kazeminia, Sara

Scattered tubular-like cells (STCs) are dedifferentiated renal tubular cells that repair other damaged kidney cells. This study shows that renovascular disease (RVD) induces site-specific 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) modifications in DNA associated with transcriptional changes and impaired proliferative capacity of swine STCs, which could be mitigated in RVD-STCs treated with an epigenetic modulator. Therefore, our observations may contribute to the development of novel approaches to preserve the reparative capacity of STCs in individuals with RVD.

Metabolic dysfunction-associated steatohepatitis (MASH) is a global health care burden. Appropriate large animal models mimicking the main MASH characteristics of steatosis, inflammation, and hepatocyte damage alongside progression of fibrosis are imperative for robust preclinical studies, especially in the field of hepatobiliary surgery. The present study aimed to characterize a novel model of steatohepatitis in fumarylacetoacetate hydroxylase-deficient ( FAH -/- ) pigs. FAH -/- pigs were generated using a CRISPR/Cas9 system. The animals received a choline-deficient, L-amino acid-defined high-fat diet and subtherapeutic doses of nitisinone and were followed for 3 months. Liver biopsies were obtained at baseline and every month during treatment. Steatosis, inflammation, and fibrosis were assessed by conventional histological scoring systems and by an artificial intelligence (AI) model. Serum liver parameters were analyzed every 2 weeks. Steatosis increased significantly throughout the study, with severe steatosis observed as early as 2 months into treatment. The inflammation score was increased in all animals after 3 months of treatment, whereas the AI-based CD45+ cell count showed region-specific trends in the portal and lobular areas. Collagen content and the corresponding fibrosis stage showed an increase over the 3-month period; however, the difference was not significant. Serum liver parameters did not show any relevant elevations during the study. In summary, we successfully developed and characterized a novel model of steatohepatitis in the FAH -/- pig within 3 months. Further studies with prolonged observation time and/or cycling of nitisinone administration are needed to evaluate whether progressive fibrosis and cirrhosis could be achieved with this model.

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.

Abstract Renal tubules have potential to regenerate and repair after mild-to-moderate injury. Proliferation of tubular epithelial cells represents the initial step of this reparative process. Although for many years, it was believed that proliferating cells originated from a pre-existing intra-tubular stem cell population, there is now consensus that surviving tubular epithelial cells acquire progenitor properties to regenerate the damaged kidney. Scattered tubular-like cells (STCs) are dedifferentiated adult renal tubular epithelial cells that arise upon injury and contribute to renal self-healing and recovery by replacing lost neighboring tubular epithelial cells. These cells are characterized by the co-expression of the stem cell surface markers CD133 and CD24, as well as mesenchymal and kidney injury markers. Previous studies have shown that exogenous delivery of STCs ameliorates renal injury and dysfunction in murine models of acute kidney injury, underscoring the regenerative potential of this endogenous repair system. Although STCs contain fewer mitochondria than their surrounding terminally differentiated tubular epithelial cells, these organelles modulate several important cellular functions, and their integrity and function are critical to preserve the reparative capacity of STCs. Recent data suggest that the microenviroment induced by cardiovascular risk factors, such as obesity, hypertension, and renal ischemia may compromise STC mitochondrial integrity and function, limiting the capacity of these cells to repair injured renal tubules. This review summarizes current knowledge of the contribution of STCs to kidney repair and discusses recent insight into the key role of mitochondria in modulating STC function and their vulnerability in the setting of cardiovascular disease.

Key Points Renovascular disease impairs the capacity of human adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic murine kidneys. miR-378h modulated the capacity of renovascular disease adipose tissue–derived mesenchymal stem/stromal cells to repair ischemic kidneys in vivo . Background Renovascular disease leads to renal ischemia, hypertension, and eventual kidney failure. Autologous transplantation of adipose tissue–derived mesenchymal stem/stromal cells (MSCs) improves perfusion and oxygenation in stenotic human kidneys, but associated atherosclerosis and hypertension might blunt their effectiveness. We hypothesized that renovascular disease alters the human MSC transcriptome and impairs their reparative potency. Methods MSCs were harvested from subcutaneous abdominal fat of patients with renovascular disease and healthy volunteers ( n =3 each), characterized and subsequently injected (5×10 5 /200 μ l) into mice 2 weeks after renal artery stenosis or sham surgery ( n =6/group). Two weeks later, mice underwent imaging and tissue studies. MSCs from healthy volunteers and in those with renovascular disease were also characterized by mRNA/microRNA (miRNA) sequencing. Based on these, MSC proliferation and mitochondrial damage were assessed in vitro before and after miRNA modulation and in vivo in additional renal artery stenosis mice administered with MSCs from renovascular disease pretreated with miR-378h mimic ( n =5) or inhibitor ( n =4). Results MSCs engrafted in stenotic mouse kidneys. Healthy volunteer MSCs (but not renovascular disease MSCs) decreased BP, improved serum creatinine levels and stenotic-kidney cortical perfusion and oxygenation, and attenuated peritubular capillary loss, tubular injury, and fibrosis. Genes upregulated in renovascular disease MSCs versus healthy volunteer MSCs were mostly implicated in transcription and cell proliferation, whereas those downregulated encoded mainly mitochondrial proteins. Upregulated miRNAs, including miR-378h, primarily target nuclear-encoded mitochondrial genes, whereas downregulated miRNAs mainly target genes implicated in transcription and cell proliferation. MSC proliferation was similar, but their mitochondrial structure and reparative function both in vivo and in vitro improved after miR-378h inhibition. Conclusions Renovascular disease impaired the reparative capacity of human MSCs, possibly by dysregulating miR-378h that targets mitochondrial genes. Podcast This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/JASN/2024_08_21_ASN0000000000000440.mp3

Abstract Background: Scattered tubular-like cells (STCs) are differentiated renal tubular cells that during recovery from ischemic injury dedifferentiate to repair other injured renal cells. Renal artery stenosis (RAS), often associated with chronic inflammatory injury, compromises the integrity and function of STCs, but the underlying mechanisms remain unknown. We hypothesized that RAS alters the transcriptomic and epigenetic profile of inflammatory genes in swine STCs. Methods: STCs were harvested from pig kidneys after 10 weeks of RAS or sham (n=6 each). STC mRNA profiles of inflammatory genes were analyzed using high-throughput mRNA-sequencing (seq) and their DNA methylation (5mC) and hydroxymethylation (5hmC) profiles by DNA immunoprecipitation and next-generation sequencing (MeDIP-seq) (n=3 each), followed by an integrated (mRNA-seq/MeDIP-seq) analysis. STC protein expression of candidate differentially expressed (DE) genes and common proinflammatory proteins were subsequently assessed in vitro before and after epigenetic (Bobcat339) modulation. Results: mRNA-seq identified 57 inflammatory genes up-regulated in RAS-STCs versus Normal-STCs (>1.4 or <0.7-fold, P<0.05), of which 14% exhibited lower 5mC and 5% higher 5hmC levels in RAS-STCs versus Normal-STCs, respectively. Inflammatory gene and protein expression was higher in RAS-STCs compared with Normal-STCs but normalized after epigenetic modulation. Conclusions: These observations highlight a novel modulatory mechanism of this renal endogenous repair system and support development of epigenetic or anti-inflammatory therapies to preserve the reparative capacity of STCs in individuals with RAS.

Autologous mesenchymal stem/stromal cells (MSCs) have demonstrated important therapeutic effects in several diseases. Cardiovascular risk factors may impair MSC mitochondrial structure and function, but the underlying mechanisms remain unknown. We hypothesized that metabolic syndrome (MetS) induces epigenetic alterations in mitochondria-related genes in swine MSCs. Pigs were fed a Lean or MetS diet (n = 6 each) for 16 weeks. MSCs were collected from subcutaneous abdominal fat, and DNA hydroxymethylation (5 hmC) profiles of mitochondria-related genes (MitoCarta-2.0) were analyzed by hydroxymethylated DNA immunoprecipitation and next-generation sequencing (hMeDIP-seq) in Lean- and MetS-MSCs untreated or treated with the epigenetic modulator vitamin (Vit)-C (n = 3 each). Functional analysis of genes with differential 5 hmC regions was performed using DAVID6.8. Mitochondrial structure (electron microscopy), oxidative stress, and membrane potential were assessed. hMeDIP-seq identified 172 peaks (associated with 103 mitochondrial genes) with higher and 416 peaks (associated with 165 mitochondrial genes) with lower 5 hmC levels in MetS-MSCs versus Lean-MSCs (≥2-fold, p < 0.05). Genes with higher 5 hmC levels in MetS + MSCs were primarily implicated in fatty acid metabolism, whereas those with lower 5 hmC levels were associated with electron transport chain activity. Vit-C increased 5 hmC levels in mitochondrial antioxidant genes, improved mitochondrial structure and membrane potential, and decreased oxidative stress. MetS alters 5 hmC levels of mitochondria-related genes in swine MSCs. Vit-C modulated 5 hmC levels in these genes and preserved mitochondrial structure and function in MetS-MSCs. These observations may contribute to development of strategies to overcome the deleterious effects of MetS on MSCs.