Monday, May 12, 2025
5/12/2025
Mechanisms of Ischemic Kidney Injury and Repair - Acute kidney injury (AKI) remains a very important and growing unmet therapeutic need. The overall goal of the studies proposed in this competitive renewal application for a grant which is now in its 37th year of support remains to understand the mechanisms involved in kidney cell injury and repair in order to develop therapeutic strategies for the prevention and treatment of AKI and its chronic consequences. The current proposal builds on prior work establishing the role of proximal tubule cells (PTCs) in adaptive and maladaptive repair. We hypothesize that kidney PTC cell injury results in DNA damage which triggers a DNA damage response including breast cancer 1 susceptibility protein (BRCA1), bromodomain containing protein 4 (BRD4) activation and nuclear lamin A accumulation leading to arrest of the cell cycle, inhibition of cell death and a senescence associated secretory phenotype (SASP). The released chemokines and growth factors, including hedgehog proteins, then activate COUP-TFII in the pericyte/fibroblast by a BRD4-dependent process, converting them to activated myofibroblasts. Male and female PTC specific BRCA1 and lamin A knockout mice, wild-type male mice and a novel transgenic “ICE” mouse with inducible DNA damage will be used in models of ischemic, obstructive and toxic kidney injury. Animal studies including genetic modifications with selective knockdown of BRCA1 or lamin A expression in PTCs or COUP-TFII in fibroblasts will be complemented by inhibitor studies and human kidney organoids, tubuloids and spheroids to enable the study of mechanisms of injury and maladaptive repair in human cell systems ex vivo. In Specific Aim 1 we will define the roles of PTC BRCA1 and BRD4 in maladaptive repair. We will evaluate pathways leading from DNA damage to senescence, impaired cell death, Target of Rapamycin (TOR)-Autophagy Spatial Coupled Compartments (TASCC) generation, and generation of pro-fibrotic growth factors and chemokines which lead to CKD. We will also evaluate the role of BRD4, a member of the bromodomain and extraterminal (BET) family, to stabilize BRCA1 after injury, increase senescence and inhibit death of DNA damaged cells. In Specific Aim 2 we will define the role of PTC lamin A in the pathobiology of kidney senescence and fibrosis. Assess the effects of lamin A and ZMPSTE24, which converts prelamin A to mature lamin A, on PTC senescence and tissue fibrosis in response to injury in vivo, and explore cellular mechanisms using human kidney epithelial cells, kidney organoids, and tubuloids ex vivo. In Specific Aim 3 we will evaluate the role of COUP-TFII, BRD4 and senescence on activation of fibroblasts, enhancement of glycolytic metabolism, and generation of profibrotic mediators.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).