Kidney Week

Abstract: SA-OR07

Cell-Intrinsic C3 and Complement Factor B from Proximal Tubular Epithelial Cells Drive Post-Injury Kidney Fibrosis

Session Information

• AKI: An Inflamed State of the Union
  October 26, 2024 | Location: Room 5, Convention Center
  Abstract Time: 05:30 PM - 05:40 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Freiwald, Tilo, University Medical Center Hamburg-Eppendorf, III. Department of Medicine, Hamburg, Germany

Tilo Freiwald, MD, DrMed

• Tajmul, Md, Immunoregulation Section, Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH, Bethesda, Maryland, United States

Md Tajmul, PhD

• Trujillo-Ochoa, Jorge Luis, Immunoregulation Section, Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH, Bethesda, Maryland, United States

Jorge Luis Trujillo-Ochoa, PhD

• Chauss, Daniel, Immunoregulation Section, Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH, Bethesda, Maryland, United States

Daniel Chauss, PhD

• Cheru, Nardos Tesfaye, Yale University School of Medicine, New Haven, Connecticut, United States

Nardos Tesfaye Cheru

• Kumar, Dhaneshwar, Immunoregulation Section, Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH, Bethesda, Maryland, United States

Dhaneshwar Kumar, PhD

• Karim, Baktiar O., Molecular Histopathology Laboratory, Frederick National Laboratory, Leidos Biomedical Research, Frederick, Maryland, United States

Baktiar O. Karim, PA

• Jäger, Julius F.E., University Medical Center Hamburg-Eppendorf, III. Department of Medicine, Hamburg, Germany

Julius F.E. Jäger

• Guo, Yubing, University Medical Center Hamburg-Eppendorf, III. Department of Medicine, Hamburg, Germany

Yubing Guo, PhD

• Gunkel, Maja, University Medical Center Hamburg-Eppendorf, III. Department of Medicine, Hamburg, Germany

Maja Gunkel

• Kemper, Claudia, Complement and Inflammation Research Section (CIRS), National Heart, Lung, and Blood Institute (NHLBI), National Institutes of Health (NIH), Bethesda, Maryland, United States

Claudia Kemper, PhD

• Huber, Tobias B., University Medical Center Hamburg-Eppendorf, III. Department of Medicine, Hamburg, Germany

Tobias B. Huber, MD, FASN

• Wiech, Thorsten, Section of Nephropathology, Institute of Pathology, University Hospital Hamburg-Eppendorf, Hamburg, Germany

Thorsten Wiech, DrMed

• Kolev, Martin, Apellis Pharmaceuticals Inc, Waltham, Massachusetts, United States

Martin Kolev, PhD

• Kazemian, Majid, Departments of Biochemistry and Computer Science, Purdue University, West Lafayette, Indiana, United States

Majid Kazemian

• Portilla, Didier, Division of Nephrology and Center for Immunity, Inflammation, and Regenerative Medicine, University of Virginia, Charlottesville, Virginia, United States

Didier Portilla, MD

• Afzali, Behdad, Immunoregulation Section, Kidney Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH, Bethesda, Maryland, United States

Behdad Afzali, MD, PhD

Group or Team Name

• Immunoregulation Section.

Background

Local complement (C') deposition is strongly associated with kidney diseases. Current therapeutic efforts target plasma-circulating C', but C' components are also locally produced within tissues, where they regulate essential (patho)physiological functions, as we have previously shown in COVID-19. The role of C’ made by kidney cells remains under-explored. We hypothesized that tubular epithelial cell-derived intrinsic C' regulates the local inflammatory milieu and influences outcomes.

Methods

We analyzed existing and de novo bulk and single-cell high-throughput data from multiple acute kidney injury (AKI) models and investigated transcription factor binding genome-wide. Mechanistic studies utilized genome editing, cell-permeable CFB inhibitors, mass spectrometry, reporter and tissue-specific gene knockout mice, metabolic profiling, histological and confocal analyses.

Results

Multiple AKI models, particularly folic acid nephropathy (FAN), showed enriched C' gene transcription. Single-nucleus RNA sequencing of FAN identified co-expression of C3 and Factor B (Cfb) in Vcam1⁺ kidney tubules, which emerged post-injury and interacted with immune cells via C3a-C3AR1 and integrins. IL-1β was the critical inducer of C3 and Cfb. Il1r1 deletion reduced C3 and Cfb expression in response to injury. AP-1 and NF-κB downstream of IL-1β, were confirmed as transactivators through SCENIC-derived regulon activity, CUT&RUN, and CRISPR studies, showing binding at C3 and Cfb. Confocal imaging revealed C3 trafficking to the ER, Golgi, endosomes, lysosomes, and mitochondria, co-localizing with CFB. Conditional deletion of C3 in proximal tubular epithelial cells and chemical intracellular CFB inhibition reduced glycolysis and oxidative phosphorylation, consistent with mitochondrial localization of C3. C3 deletion also reduced fibrosis scores in FAN mice. In patients, C3 and CFB correlated with each other across glomerular diseases and negatively with eGFR.

Conclusion

These data elucidate the transcriptional and post-translational regulation and subcellular trafficking of C3 within PTECs, offering therapeutic implications for targeting the intracellular complement system in inflammatory kidney diseases.

Funding

• NIDDK Support – Apellis Pharmaceuticals