Disrupted Renal Mitochondrial Homeostasis after Liver Transplantation in Rats

Cold storage effects on mitochondrial bioenergetics and protein expression in human mesenchymal stromal cells

BACKGROUND

A ready-to-use format for cell therapy products, human mesenchymal stromal cells (MSCs) or other progenitor cells, would make their use in acute trauma feasible by the military or in rural community hospitals. In designing a strategy to package MSCs, it was noted that vitality (adenosine triphosphate [ATP] content) fell prior to viability. This study investigated the effects of cold storage on mitochondrial bioenergetics and protein in MSCs.

METHODS

Commercial MSCs were harvested and resuspended in either a balanced salt solution (PlasmaLyte A) or xeno-free medium (XFM) and then stored at 4°C. Cells were assayed on Days 0, 4, 7, 14, and 21 for cell count, viability, and ATP content, mitochondrial bioenergetics by Seahorse XF24 and Oroboros, and mitochondrial membrane potential by JC1 staining. Levels of proteins involved in mitochondrial function were assayed by Western blots. Proteins assessed included those involved in mitochondrial fusion (OPA1, MFN1, MFN2), fission (FIS1, DRP1, and DRP1 phosphoserine 637), regulation (PINK1 kinase and Parkin ubiquitin-ligase), mitophagy (NDP52 and optineurin), and electron transport chain function (COX IV, SDHB, cytochrome C, and NDUFS1).

RESULTS

Total counts for cells stored in PlasmaLyte A and XFM were similar through Day 21. However, by Day 4, while viability was modestly decreased for cells stored in PlasmaLyte A compared with those in XFM (68% vs. 83%), ATP content plummeted for cells stored in PlasmaLyte A, with only 9.5% of the initial ATP compared with 86% of the initial ATP levels for cells stored in XFM. Both the Seahorse assays and JC1 staining identified further differences between media. JC1 staining revealed that mitochondria were almost completely depolarized by Day 7 following storage in PlasmaLyte A whereas polarized mitochondria were still evident at Day 21 for cells stored in XFM. By Western blot analyses, significant changes in fusion, fission, and mitophagy proteins were observed both for media and over time whereas the electron transport proteins were generally stable. Significant changes in the phosphorylated form of the fission protein DRP1S637 most closely correlated with the ATP data. All parameters were better preserved over time in the XFM.

CONCLUSIONS

This study highlighted changes that occur during 4°C storage in the areas of vitality, mitochondrial membrane polarization, and fission. With these targets, research into treatments or additives to a media to improve cold storage and maintain functional cells at 4°C could result in a product that greatly extends the therapeutic use of cellular therapies.

Mitochondrial dysfunction in the pathophysiology of renal diseases

Mitochondria are essential organelles in the human body, serving as the metabolic factory of the whole organism. When mitochondria are dysfunctional, it can affect all organs of the body. The kidney is rich in mitochondria, and its function is closely related to the development of kidney diseases. Studying the relationship between mitochondria and kidney disease progression is of great interest. In the past decade, scientists have made inspiring progress in investigating the role of mitochondria in the pathophysiology of renal diseases. This article discusses various mechanisms for maintaining mitochondrial quality, including mitochondrial energetics, mitochondrial biogenesis, mitochondrial dynamics, mitochondrial DNA repair, mitochondrial proteolysis and the unfolded protein response, mitochondrial autophagy, mitochondria-derived vesicles, and mitocytosis. The article also highlights the cross talk between mitochondria and other organelles, with a focus on kidney diseases. Finally, the article concludes with an overview of mitochondria-related clinical research.

Roles of Mitochondrial DNA Damage in Kidney Diseases: A New Biomarker

The kidney is a mitochondria-rich organ, and kidney diseases are recognized as mitochondria-related pathologies. Intact mitochondrial DNA (mtDNA) maintains normal mitochondrial function. Mitochondrial dysfunction caused by mtDNA damage, including impaired mtDNA replication, mtDNA mutation, mtDNA leakage, and mtDNA methylation, is involved in the progression of kidney diseases. Herein, we review the roles of mtDNA damage in different setting of kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD). In a variety of kidney diseases, mtDNA damage is closely associated with loss of kidney function. The level of mtDNA in peripheral serum and urine also reflects the status of kidney injury. Alleviating mtDNA damage can promote the recovery of mitochondrial function by exogenous drug treatment and thus reduce kidney injury. In short, we conclude that mtDNA damage may serve as a novel biomarker for assessing kidney injury in different causes of renal dysfunction, which provides a new theoretical basis for mtDNA-targeted intervention as a therapeutic option for kidney diseases.

Literature review of the mechanisms of acute kidney injury secondary to acute liver injury

People exposed to liver ischaemia reperfusion (IR) injury often develop acute kidney injury and the combination is associated with significant morbidity and mortality. Molecular mediators released by the liver in response to IR injury are the likely cause of acute kidney injury (AKI) in this setting, but the mediators have not yet been identified. Identifying the mechanism of injury will allow the identification of therapeutic targets which may modulate both liver IR injury and AKI following liver IR injury.

Loss of core fucosylation enhances the anticancer activity of cytotoxic T lymphocytes by increasing PD-1 degradation

As an immune checkpoint, programmed cell death 1 (PD-1) and its ligand (PD-L1) pathway plays a crucial role in CD8⁺ cytotoxic T lymphocytes (CTL) activation and provides antitumor responses. The N-glycans of PD-1 and PD-L1 are highly core fucosylated, which are solely catalyzed by the core fucosyltransferase (Fut8). However, the precise biological mechanisms underlying effects of core fucosylation of PD-1 and PD-L1 on CTL activation have not been fully understood. In this study, we found that core fucosylation was significantly upregulated in lung adenocarcinoma. Compared to those of Fut8^+/+ OT-I mice, the lung adenocarcinoma formation induced by urethane was markedly reduced in Fut8^-/- OT-I mice. De-core fucosylation of PD-1 compromised its expression on Fut8^-/- CTL, resulted in enhanced Fut8^-/- CTL activation and cytotoxicity, leading to more efficient tumor eradication. Indeed, loss of core fucosylation significantly enhanced the PD-1 ubiquitination and in turn led to the degradation of PD-1 in the proteasome. Our current work indicates that inhibition of core fucosylation is a unique strategy to reduce PD-1 expression for the antilung adenocarcinoma immune therapy in the future.