An Acidic Tubulointerstitial Microenvironment Delays Cell-Cycle Progression in Proximal Tubule Cells and Fibroblasts and Synergizes With Lactate to Drive Phenotypic Alterations.

Authors

Marie-Christin Schulz, Virginie Dubourg, Lea Schaude, Natalie Schröder, Eva Janßen, Isabelle Görlich, Stefanie Ruhs, Michael Kopf, Michael Gekle

Published in

Acta physiologica (Oxford, England). Volume 242. Issue 10. Pages e70302.

Abstract

Chronic kidney disease (CKD) is characterized by progressive tubulointerstitial inflammation and fibrosis, particularly affecting the proximal tubule. Both proximal tubular epithelial cells and interstitial fibroblasts contribute to CKD progression through cell-cycle arrest and phenotypic transitions. The aim of the present study was to address whether lactic acidosis contributes to these processes.
Human proximal tubular cells (HK-2 cells) and fibroblasts (CCDSk cells) were exposed to lactic acid, hydrochloric acid, or sodium lactate. Transcriptomic changes were assessed by RNA sequencing followed by GO term enrichment as well as canonical pathway and upstream-regulator analyses. Predicted effects on the cell cycle were validated experimentally using BrdU incorporation and digital microscopy-based cell-cycle analysis. Protein expression of IL-6, c-FOS, phospho-JAK1 and JAK2, STAT3, SRF, and p38 was assessed by Western blot.
Transcriptomic analysis revealed synergistic effects of lactate and acidification on gene expression, which were associated with cell type-specific phenotypic changes. Biological assays confirmed these predictions: HK-2 cells underwent a sustained G1 arrest with reduced DNA synthesis, while CCDSk cells displayed only a transient arrest resolving after 48 h. Predictions further indicated that lactic acidosis amplifies these effects, driving fibrotic reprogramming in HK-2 cells and promoting a phenotypic switch of CCDSk cells toward an inflammatory state.
Our findings suggest that extracellular lactic acidosis primes tubular cells for fibrotic remodeling and CCDSk cells for inflammatory activation, and may therefore represent an initiating microenvironmental trigger for maladaptive changes in CKD progression.

PMID:
42703650
Bibliographic data and abstract were imported from PubMed on 07 Sep 2026.

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