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Deciphering intrarenal communication to unvail mechanisms of chronic kidney diseases

Periodic Reporting for period 1 - DIE_CKD (Deciphering intrarenal communication to unvail mechanisms of chronic kidney diseases)

Período documentado: 2019-09-01 hasta 2021-08-31

The kidneys are essential, often overlooked organs that perform several vital functions in the human body. Far beyond the well-known removal of wastes from the blood, the kidneys participate in regulating body volume, organ homeostasis, and blood pressure regulation. Because of performing so many tasks, their structure is very complex. Certain parts of the kidneys demand a lot of energy, in other words, a lot of oxygen. That leaves the kidney vulnerable to injury, with different parts showing different susceptibility to injury. In brief, the kidney structural unit, nephron, is composed of the blood filtering unit, glomerulus which continues in the renal tubules where non-waste solutes are reabsorbed and returned to the bloodstream. Both components can be injured individually, and there are usually different triggers to glomerular or tubular injury. An injury to one compartment is known to affect other parts of the kidney. While the mechanisms of disease progression originating in the glomerulus and spreading to tubule is relatively well described, less is known how tubular injury affects glomerulus. Moreover, recently, it has been described that even after recovery from an injury to one compartment (tubule), there is an increased risk of damage to the other compartment (glomerulus). Currently, the mechanisms responsible for such detrimental signalling are not fully understood.
The number of people with kidney disease worldwide is high, and it is expected to rise due to a variety of reasons. For example, the advancements in modern medicine in the recent decades have led to a higher life expectancy. However, because a higher age is linked to a higher risk for the development of various diseases, that in turn led to a higher number of people suffering from health complications. Similarly to other organs, the aging kidney loses its functionality and becomes more susceptible to injury. Approximately one in five hospitalized people have or develop acute kidney injury. When kidney injury is present, the prognosis for the patient is worse. Most of the cases of acute kidney injury originate in the renal tubule. Moreover, acute kidney injury is a risk factor for developing chronic kidney disease, which is a long-term health complication. Chronic kidney diseases are progressive, and they eventually reach a state when the kidneys can no longer perform their function (end-stage renal disease). Such patients require regular dialysis or a kidney transplant. Kidney dialysis has a negative impact on patients' life quality and poses a substantial economic burden. At the same time, long waiting lists hamper kidney transplantation due to a shortage of available organs. Thus, a better understanding of the crosstalk between different kidney compartments might have implications in developing therapeutic approaches for preventing the onset and progression of kidney diseases.
The overall objective of our work was to investigate how tubular injury influences future harm to the glomerulus. We tested varying degrees of tubular injury and their effect on the glomerulus upon a second hit injury. In addition, we sought possible mediators of such detrimental signalling by RNA sequencing of isolated tubules and glomeruli, as well as single nuclei RNA sequencing.
We performed murine experiments using sequential tubular injury followed by a second hit glomerular injury. We included both sexes in the experiments and induced tubular injury by three different doses of two different agents in two separate experiments. To analyze the samples, we performed biochemical and histopathological analyses to assess renal function and renal damage. To analyze the crosstalk between the tubular and glomerular segments, we used RNA sequencing methods to explore the gene expression in the search for molecules involved in the signalling. We used standard, bulk RNA sequencing from isolated tubules and isolated glomeruli. In addition, we performed single nuclei RNA sequencing, a novel high-throughput method that allows performing gene expression analysis on a single cell level and thus provide an in-depth perspective on the pathological processes taking place in different cell types. We have found sex differences in the susceptibility to both tubular and glomerular injury, which may have further implications in developing future personalized therapies that take into account gender-based differences. We also found potential new mediators that might be involved in detrimental tubuloglomerular crosstalk in renal disease.
We have tested varying extents of tubular injury and their implications for a subsequent glomerular injury, which has not been studied in this setting and extent until now. We also performed different high-throughput RNA sequencing analyses, including on a single cell level which will provide novel data on the crosstalk between different kidney compartments. Understanding of the complex interactions between different compartments will be beneficiary in future drug developments to combat kidney disease.
Synopsis of the studied question.