Kidney function is essential for removing the wastes that result from normal cell function and maintaining water and salt balance in our internal tissues. These actions are carried out by roughly a million nephrons within the kidney that filter all the body’s blood roughly once every 1-2 hours. The kidney also regulates other tissues controlling blood pressure and blood cell composition, and regulating the strength of bone by activating vitamin D. Chronic kidney injury over time results in a loss of normal kidney function leading to end stage renal disease (ESRD). ESRD affects 500,000 Americans and its prevalence is increasing with a rise in diabetes and hypertension. ESRD is associated with significant morbidity and mortality: ultimately kidney transplant is the only cure but for every four patients requiring a transplant there are only enough available kidneys to help one. Life-threatening kidney injury also occurs through acute damage particularly in hospital settings were infection, toxic drugs or ischemia during surgery kills cells in the nephron shutting down the kidneys. Animal studies indicate that the kidney is unable to make new nephrons: the full complement of nephrons for life are established prior to birth. However, the damaged nephron has a limited capacity to restore activity through the regeneration of missing cells by their surviving neighbors.
Our research has focused on an understanding of the damage/repair process following acute kidney injury to identify new therapeutic opportunities. We have utilized a mouse model to generate a BioBank resource of injured and repairing kidney samples. Further, we have generated a novel approach that allows the investigator to focus on injury and repair responses within specific cellular compartments in the kidney. As an example, this approach allows us to investigate changes in gene activity within the nephron itself, or in the blood vessels that engulf the nephrons. Both are targets of injury and effective repair will likely involve solutions for each of these components of the kidney. We have generated a large informational base and started to mine this data to identify genes with the potential to direct or augment renal repair. Using modern genetic strategies we are now exploring the roles of several of these genes. Our goal is to move from discovery to translation of those discoveries during the course of this CIRM leadership award.
Reporting Period:
Year 2
Kidney function is essential for removing the wastes that result from normal cell function and maintaining water and salt balance in our internal tissues. These actions are carried out by roughly a million nephrons within the kidney that filter all the body’s blood roughly once every 1-2 hours. The kidney also regulates other tissues controlling blood pressure and blood cell composition, and regulating the strength of bone by activating vitamin D. C hronic kidney injury over time results in a loss of normal kidney function leading to end stage renal disease (ESRD). ESRD affects 500,000 Americans and its prevalence is increasing with a rise in diabetes and hypertension. ESRD is associated with significant morbidity and mortality: ultimately kidney transplant is the only cure but for every four patients requiring a transplant there are only enough available kidneys to help one. Life-threatening kidney injury also occurs through acute damage particularly in hospital settings were infection, toxic drugs or ischemia during surgery kills cells in the nephron shutting down the kidneys. Animal studies indicate that the kidney is unable to make new nephrons: the full complement of nephrons for life are established prior to birth. However, the damaged nephron has a limited capacity to restore activity through the regeneration of missing cells by their surviving neighbors.
Our research has focused on an understanding of the damage/repair process following acute kidney injury to identify new therapeutic opportunities. We have utilized a mouse model to generate a BioBank resource of injured and repairing kidney samples. Further, we have generated a novel approach that allows the investigator to focus on injury and repair responses within specific cellular compartments in the kidney. As an example, this approach allows us to investigate changes in gene activity within the nephron itself, or in the
blood vessels that engulf the nephrons. Both are targets of injury and effective repair will likely involve solutions for each of these components of the kidney. We have generated a large informational base and started to mine this data to identify genes with the potential to direct or augment renal repair. Using modern genetic strategies we are now exploring the roles of several of these genes. Our goal is to move from discovery to translation of those discoveries during the course of this C IRM leadership award.
Reporting Period:
Year 3
Kidney function is essential for removing the wastes that result from normal cell function and maintaining water and salt balance in our internal tissues. These actions are carried out by roughly a million nephrons within the kidney that filter all the body’s blood roughly once every 1-2 hours. The kidney also regulates other
tissues controlling blood pressure and blood cell composition, and regulating the strength of bone by activating vitamin D. C hronic kidney injury over time results in a loss of normal kidney function leading to end stage renal disease (ESRD). ESRD affects 500,000 Americans and its prevalence is increasing with a rise in diabetesand hypertension. ESRD is associated with significant morbidity and mortality: ultimately kidney transplant is the only cure but for every four patients requiring a transplant there are only enough available kidneys to help one. Life-threatening kidney injury also occurs through acute damage particularly in hospital settings were infection, toxic drugs or ischemia during surgery kills cells in the nephron shutting down the kidneys. Animal studies indicate that the kidney is unable to make new nephrons: the full complement of nephrons for life are established prior to birth. However, the damaged nephron has a limited capacity to restore activity through the regeneration of missing cells by their surviving neighbors.
Our research has focused on an understanding of the damage/repair process following acute kidney injury to identify new therapeutic opportunities. We have utilized a mouse model to generate a BioBank resource of injured and repairing kidney samples. Further, we have generated a novel approach that allows the investigator to focus on injury and repair responses within specific cellular compartments in the kidney. As an example, this approach allows us to investigate changes in gene activity within the nephron itself, or in the blood vessels that engulf the nephrons. Both are targets of injury and effective repair will likely involve solutions for each of these components of the kidney. We have generated a large informational base andstarted to mine this data to identify genes with the potential to direct or augment renal repair. Using modern genetic strategies we are now exploring the roles of several of these genes. Our goal is to move from discovery to translation of those discoveries during the course of this C IRM leadership award.
Reporting Period:
Year 4
Kidney function is essential for removing the wastes that result from normal cell function and maintaining water and salt balance in our internal tissues. These actions are carried out by roughly a million nephrons within the kidney that filter all the body's blood roughly once every 1·2 hours. The kidney also regulates other tissues controlling blood pressure and blood cell composition, and regulating the strength of bone by activating vitamin D. Chronic kidney injury over time results in a loss of normal kidney function leading to end stage renal disease (ESRD). ESRD affects 500,000 Americans and its prevalence is increasing with a rise in diabetes and hypertension. ESRD is associated with significant morbidity and mortality: ultimately kidney transplant is the only cure but for every four patients requiring a transplant there are only enough available kidneys to help one. Life-threatening kidney injury also occurs through acute damage particularly in hospital settings were infection, toxic drugs or ischemia during surgery kills cells in the nephron shutting down the kidneys. Animal studies indicate that the kidney is unable to make new nephrons: the nephron complement is established prior to birth. However, the damaged nephron has a limited capacity to restore activity through the regeneration of missing cells by their surviving neighbors.
Our research has focused on an understanding of the progenitor cell types that build the kidney and the damage repair processes that restore function following an acute kidney. While there is a considerable understanding of nephron progenitors in the mouse, our understanding of their human counter parts is limited. We have examined human nephron progenitors and identified differences in the regulatory factors responsible for regulating the nephron progenitor state. Recent progress has enabled kidney-like structures, kidney organoids, to develop in cell culture from pluripotent stem cells. This advance will facilitate the characterization of human kidney progenitors and the structures to which they give rise. To take advantage of these systems we have developed genetically modified cell lines where activation of a fluorescent marker signals the formation of kidney cell types of interest in kidney organoid cultures. With these, we can optimize protocols for nephron generation in the dish and determine if key cell types mirror the molecular properties of their counterparts in the normal kidney.
In kidney repair, we have identified a regulatory factor, SOX9, activated on kidney injury in cells that go onto repair kidney tubule damage. Further, SOX9 action is critical for the normal repair process. Understanding how SOX9 operates in renal repair may provide means to activate and augment repair processes to effect lasting repair following kidney damage. This is particularly important not only because of the high mortality (more than 40%) associated with acute kidney injury, but the increased likelihood that a patient that survives acute injury succumbs to chronic disease often times many years after the injurious event.
To provide additional insight into both the repair process and the transition over time to chronic kidney disease, we have generated a BioBank resource of injured and repairing kidney samples and characterized these extensively at the molecular level. This resource forms the basis for both hypothesis driven research of ideas emerging from these data sets and an information set to be correlated to events at play in the human kidney to focus future studies on the most human-relevant components of the mouse kidneys injury and repair responses. Our CIRM leadership award is moving from discovery to functional analysis with the ultimate goals of clinical translation
Reporting Period:
Year 6
Chronic kidney disease affects 10% of Americans. Over 700,000 receive dialysis. The long-term prognosis for the dialysis patient is poor. A renal transplant can provide a cure but there are too few kidneys to meet the need. Our studies have taken two distinct directions towards the goal of improving outcomes for kidney patients: understanding how the human kidney is built to be able to replicate normal developmental strategies to synthesize new kidney structures and examining injury-invoked repair processes in the mammalian kidney to better understand normal repair processes: the cell types and molecular mechanisms, the limits to repair, and the relationship between failed repair, fibrosis and the progression of chronic kidney disease.
Our analysis of the developing human kidney has provided the first comprehensive insight into developmental processes highlighting molecular and cellular events shared with the well-studied mouse model, but unique human features. The insights here will be critical to optimizing strategies to generate normal human kidney structures from pluripotent stem cells (PSCs). To this end, we employed genetic tagging strategies to facilitate the isolation of key cell types from PSC-derived human kidney organoids demonstrating that cells generated in the tissue culture dish have remarkable similarities to their counterparts within the normal kidney. Kidney organoids not only provide a mechanism to obtain relevant renal cell types to move translational efforts forward but they can also model renal disease as we have shown with a PSC-directed, kidney organoid model of polycystic kidney disease, a leading genetic cause of end stage renal disease.
Grant Application Details
Application Title:
Repair and regeneration of the nephron
Public Abstract:
Kidney function is essential for removing the wastes that result from normal cell function and maintaining water and salt balance in our internal tissues. These actions are carried out by roughly a million nephrons within the kidney that filter all the body’s blood roughly once every 1-2hours. The kidney also regulates other tissues controlling blood pressure and blood cell composition, and regulating the strength of bone by activating vitamin D. Chronic kidney injury over time results in a loss of normal kidney function leading to end stage renal disease (ESRD). ESRD affects 500,000 Americans and its prevalence is increasing with a rise in diabetes and hypertension. ESRD is associated with significant morbidity and mortality: ultimately kidney transplant is the only cure but for every four patients requiring a transplant there are only enough available kidneys to help one. Life-threatening kidney injury also occurs through acute damage particularly in hospital settings were infection, toxic drugs or ischemia during surgery kills cells in the nephron shutting down the kidneys. Animal studies indicate that the kidney is unable to make new nephrons: the full complement of nephrons for live are established prior to birth. However, the damaged nephron has a limited capacity to restore activity through the regeneration of missing cells by their surviving neighbors.
Kidney stem cells give rise to all specialist parts of the complex nephron structure during kidney development. New genetic approaches in the mouse have enabled the isolation of these stems cell providing an opportunity to develop strategies to propagate and differentiate kidney stem cells into nephrons in the tissue culture dish. We expect that the insights gained from these studies will facilitate the translation of de novo nephrogenesis to human nephron cultures, and as a result, the development of new approaches to study and treat kidney disease. An alternative approach comes from the observation of limited self-repair by cells within damaged nephrons. The molecular and cellular processes at play in the damage-repair responses are largely unknown but elucidating these mechanisms will facilitate development of novel strategies to either augment the repair process following damage or prevent tubule damage in the first instance within at risk patients. Mouse models again provide a way forward to this long-term goal. By isolating repairing cells, and comparing gene expression signatures amongst damaged, repairing and healthy cells, we will identify repair specific responses and test the ability of candidate repair regulators to enhance the restoration of kidney function.
Statement of Benefit to California:
Approximately 1% of Medicare enrollees in the State of California have End State Renal Disease and this number will rise. There is no effective cure aside from kidney transplantation, too few donors, and a high morbidity and mortality associated with long-term dialysis. Approximately 5-7% of hospitalized patients experience acute kidney injury, a leading cause of mortality in institutionalized settings. The target of kidney injury and disease is the nephron, all nephrons form during fetal life and self-repair within nephrons is thought to restore normal function. Through identifying conditions that support stem cells capable of new nephrogenesis and generating new nephrons from these cells, we will be able to explore approaches to restoring kidney function that are not currently possible. Further, the identification of factors associated with normal nephron repair will enable functional investigation of their potential clinical significance in kidney injury models. Given the fiscal cost of kidney disease within the State, the toll of kidney disease on patients and their families, and the lack of alternatives – developing approaches that treat disease would have a significant impact.
