# Transcriptional Regulation of Thrombotic Microangiopathy in the Renal Microvasculature

> **NIH VA IK2** · NORTHPORT VA MEDICAL CENTER · 2022 · —

## Abstract

Renal-specific thrombotic microangiopathy (TMA) represents the most severe manifestation of renal endothelial
injury consisting of endothelial cell (EC) swelling, subEC expansion, inflammation and microthrombi and
untreated progresses uniformly to chronic kidney disease. TMA occurs subsequent to various etiologies including
hemolytic uremic syndrome, anti-vascular endothelial growth factor (VEGF) therapy, malignant hypertension and
antibody mediated rejection after transplant, and despite diverse causes, is typically associated with
dysregulation of key thrombotic and inflammatory EC transcripts and complement activation. Furthermore,
expression of membrane bound (DAF, CD59, CD46) complement regulators, is altered in many subtypes of TMA
and it is unclear whether this is a driver or consequence of injury. To investigate the mechanism(s) by which
complement activation and EC transcripts are dysregulated in TMA, we reviewed expression arrays of RNA-
sequencing from kidney biopsies with TMA, and observed that Krüppel-Like Factor 4 (KLF4), a zinc finger
transcription factor, is the highest differentially expressed transcript. Previous studies demonstrate that KLF4 is
a critical mediator of anti-thrombotic and anti-inflammatory phenotype in systemic vascular beds, but its role
modulating renal microvascular injury and complement activation in TMA remains to be investigated. Based on
this and our preliminary data, my central hypothesis, that EC-KLF4 is required to prevent complement-dependent
and independent renal microvascular EC injury in TMA, will be investigated by the following specific aims: 1)
Determine the renoprotective role of EC-specific KLF4 in TMA; 2) Test the hypothesis that KLF4-DAF interaction
is required to mitigate complement activation in TMA; and 3) Investigate the mechanism(s) by which KLF4
attenuates renal microvascular EC injury in TMA. Under subaim 1A, we will determine whether mice with the
inducible loss of EC-Klf4 (iKlf4ΔEC) have accelerated renal EC injury and complement activation using two murine
TMA models (anti-VEGFR2 Ab and Shiga toxin). In subaim 1B, the protective role of KLF4 will be determined
using mice with EC-overexpression of KLF4 subjected to VEGFR2 inhibition. Extent of injury will be evaluated
by histology, ultrastructure and functional measures, as well as inflammatory and thrombotic transcripts and
complement activation. In subaim 2.A., we will evaluate the mechanism of interaction between KLF4 and DAF
using ChIP assay and luciferase reporter. In subaim 2.B., we will test whether mice with EC-Daf knockdown
have increased susceptibility to EC complement activation by treating them with a VEGFR2 inhibitor and crossing
them with Klf4ΔEC mice in two experiments. In subaim 2.C, we will perform IF for DAF and C3 in human biopsies
TMA specimens to corroborate our findings. Finally, in aim 3, we will investigate the mechanism(s) by which
KLF4 attenuates EC injury via complement dependent (subaim 3.A), and independe...

## Key facts

- **NIH application ID:** 10253029
- **Project number:** 1IK2BX005380-01A1
- **Recipient organization:** NORTHPORT VA MEDICAL CENTER
- **Principal Investigator:** Chelsea Estrada
- **Activity code:** IK2 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2022
- **Award amount:** —
- **Award type:** 1
- **Project period:** 2021-10-01 → 2026-09-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10253029

## Citation

> US National Institutes of Health, RePORTER application 10253029, Transcriptional Regulation of Thrombotic Microangiopathy in the Renal Microvasculature (1IK2BX005380-01A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10253029. Licensed CC0.

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