Role of endocycle in Acute Kidney Injury Response and Chronic Kidney Disease development

Project Information

ROAR

Grant agreement ID: 845774

DOI

10.3030/845774

Project closed

EC signature date 12 April 2019

Start date 1 September 2019

End date 31 August 2021

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 171 473,28

EU contribution

€ 171 473,28

Coordinated by

UNIVERSITA DEGLI STUDI DI FIRENZE
Italy

Periodic Reporting for period 1 - ROAR (Role of endocycle in Acute Kidney Injury Response and Chronic Kidney Disease development)

Reporting period: 2019-09-01 to 2021-08-31

Summary of the context and overall objectives of the project

Acute Kidney Injury (AKI) is characterized by an acute deterioration of kidney function impacting million patients per year. The cost of AKI-related inpatient care is estimated to be higher than that of the four most common cancers combined. In addition, AKI survivors frequently develop chronic kidney disease (CKD) which is associated with a high cardiovascular risk and progression toward end stage kidney disease (ESKD). CKD contributes a substantial proportion of disease burden globally. Yet over the past 30 years the burden of CKD has not declined to the same extent as many other important non-communicable diseases (i.e. cardiovascular and cancer-related diseases) implying a substantial deficit in the understanding of the disease progression. Recently, it has been described that kidney cells respond to AKI by triggering endocycle-mediated polyploidization. Polyploid cells derive from alternative cell cycles that lead to the formation of hypertrophic cells with an increased DNA content.

The discovery that polyploidy occurs within the kidney after AKI has revolutionized our understanding of how the kidney responses to an injury. However, the mechanisms controlling kidney polyploidization have been completely unknown until recently. Collectively the objectives of this project were: 1) to uncover the mechanisms governing polyploidy in the kidney; 2) to establish the importance of polyploid cells for patient’s survival after AKI; 3) to determine the role of polyplod cells in the progression of AKI to CKD and 4) to design novel tools for early detection and stratification of patients at risk of developing CKD after AKI.

The results obtained in this project have identified the pathways that control polyploidization of kidney cells. Importantly, these data proved that after AKI, polyploid cells are required to sustain kidney function and that they are essential for survival. Finally, polyploid cells were found to be involved in the formation of scar tissue after AKI promoting CKD progression. This important result was also confirmed in kidney biopsies of CKD patients representing an important translational output.

Finally, one essential feature of this project is the translation of this knowledge to novel promising therapeutic and diagnostic approaches to CKD progression and management of AKI patients. Consequently, these efforts will have a potential positive impact for both patients and public health.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

1) During this project, it has been successfully developed a noninvasive and novel in vitro model to screen and test the molecules potentially involved in kidney cell polyploidization.
2) The temporal and spatial distribution of kidney cells becoming polyploid after AKI was characterized by DNA content analysis and using new cutting edge tecquinques such as the sequencing of RNA from a single cell (scRNA-seq). These analyses led to the identification of a specific protein, denominated YAP1, as the main controller of kidney cell polyploidization.
3) Two novel transgenic mouse lines derived throughout the duration of the project, proved that kidney cell polyploidization represented a rapid way to sustain residual kidney function early during AKI. This lifesaving mechanism comes at the cost of premature aging of polyploid kidney cells promoting the formation of scar tissue and CKD, explaining the high prevalence of AKI-CKD transition in AKI survivors.
4) Importantly, considering the role of polyploid cells in scar tissue formation, a protocol was devised to block CKD progression by treating mice with an inhibitor of polyploid cells. This important translational output implies that polyploid cells can be exploited as a target to prevent CKD progression. In addition, they may serve as potential biomarkers of AKI severity and outcomes.
5) In human kidney biopsies, the level of polyploid kidney cells correlated with scar tissue development in CKD patients. This important result suggests that the extent of kidney polyploidization can be potentially used as a prognostic marker of CKD.
All these data have been effectively disseminated in various conferences. Specifically:

• The annual meeting of the American Society of Nephrology (Kidney Week) in 2019, 2020 and 2021.
• The annual meeting of the European Renal Association - European Dialysis and Transplant Association in 2020 and 2021
• The annual meeting of the European Renal Cell Study Group in 2019.
• The annual meeting of the American Society for Cell Biology in 2021

They also have been disseminated during the course of the researchers' nights and through the social media.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Ultimately this project aimed to: 1) Evaluate the importance of polyploid cells for kidney function recovery after AKI; 2) Assess the role of polyploid cells in the progression of AKI to CKD and 3) Study the mechanism by which kidney polyploidization contributes to CKD development. This highly ambitious program generated a number of tangible translational outputs described in the previous sections highly transferrable to the clinical sphere.

1) Evaluate the importance of polyploid cells for kidney function recovery after AKI.
In this project it was found that YAP1-driven tubular cell polyploidization is required to survive AKI, identifying for the first time a lifesaving mechanism of cellular adaptation to acute kidney injury. This result represents a significant advance in the field with critical implications for patient management and opens to the possibility of new strategies of treatment for AKI.

2) Assess the role of polyploid cells in the progression of AKI to CKD.
The lifesaving mechanism promoted by polyploidization comes at the cost of excessive stress at which polyploid kidney cells are exposed in their process of becoming hypertrophic. This excessive stress promotes the formation of scar tissue leading ultimately to CKD, explaining the high prevalence of AKI-CKD transition in AKI survivors. However, the data collected in this project demonstrated that targeting kidney polyploid cells after the early AKI phase can prevent AKI-CKD transition. These results revise the current pathophysiological concept of how the kidney responds to acute injury and identify a novel drug target to improve prognosis in AKI survivors.

3) Study the mechanism by which kidney polyploidization contributes to CKD development.
This project used cutting edge technologies (scRNA-seq and transgenic mouse models) to characterize polyploid cells providing unparalleled insights into the genes that regulate and control polyploidization in the kidney. As an important translational output, in this object it was proved that polyploid kidney cells activate a program that lead to the formation of scar tissue also in human CKD biopsies. Collectively, this object provided critical information about genes participating in the development of CKD. Importantly, the results of this objective are currently being exploited by performing a screening in the urine of AKI patients and correlating these markers with the risk of developing CKD. The acquired knowledge will lead to the identification of novel markers to predict the likelihood of CKD progression in a non-invasive manner in AKI patients.

Summary of results