Autosomal dominant polycystic kidney disease (ADPKD) is characterized by progressive cyst formation that replaces normal renal parenchyma. The transcription factor Runx1 is markedly upregulated in Pkd1 mutant renal epithelial cells and in kidneys from Pkd1-mutant mice, with increases demonstrated at both mRNA and protein levels. Immunostaining localized Runx1 to cyst-lining epithelia using lectin markers (LTL, THP, DBA) and nuclear counterstaining. The source reports statistically significant elevations of Runx1 in Pkd1 null and mutant models compared with wild type (reported p-values < 0.05 to < 0.01 in relevant comparisons).
Runx1 induction in Pkd1-mutant contexts was linked to elevated cAMP/PKA signaling. In vitro, treatment with forskolin increased Runx1 protein in wild-type and Pkd1 mutant cells, whereas PKA inhibition (H89) reduced Runx1 in Pkd1 null cells. Genetic models with constitutively activated PKA showed higher Runx1 mRNA, while constitutive inhibition of PKA reduced Runx1 expression in Pkd1 RC/RC mice. These observations indicate that Runx1 is regulated downstream of cAMP/PKA signaling in the ADPKD setting.
The selective Runx1 inhibitor Ro5-3335 was tested in both rapidly progressive (Pkd1 nl/nl) and slowly progressive (Pkd1 RC/RC) mouse models. Treatment reduced cystic burden as assessed by histology and quantitative endpoints. Reported outcomes in treated versus vehicle groups included reductions in cystic index and kidney-weight-to-body-weight (KW/BW) ratios; BUN levels were improved in treated animals. Ki67 immunostaining indicated decreased proliferative activity of cyst-lining epithelial cells after Ro5-3335. Group sizes cited in the figures were n = 9 per treatment arm for the mouse studies shown; multiple endpoints reached statistical significance (for example, cystic index and KW/BW p < 0.01, BUN p < 0.05 in some comparisons). Body weight differences were not significant in the reported comparisons (one comparison reported p = 0.17 or p = 0.24).
Mechanistic analyses demonstrated that Runx1 promotes activation of signaling pathways previously implicated in ADPKD. Phosphorylation levels of Akt, mTOR, S6, ERK, and STAT3 were increased in Pkd1 mutant kidneys and were decreased after Ro5-3335 treatment. In cultured PN24 cells, Runx1 knockdown by siRNA reduced phosphorylation of these signaling nodes; Ro5-3335 produced dose- and time-dependent reductions in pathway activation. These results support a model in which Runx1 amplifies proliferative and growth signaling via multiple convergent pathways.
Runx1 was reported to suppress p53-mediated apoptosis in cyst-lining epithelial cells, thereby favoring cyst expansion. Ro5-3335 treatment increased markers of epithelial cell death in cyst-lining epithelia in treated kidneys relative to vehicle, consistent with release of p53-dependent apoptotic controls. Concurrently, proliferation markers such as Ki67 were reduced after Runx1 inhibition, indicating that Runx1 supports a pro-proliferative program in cystic epithelia.
Beyond epithelial-autonomous effects, Runx1 enhanced renal inflammation and fibrosis in Pkd1-mutant kidneys. The transcription factor promoted macrophage infiltration and inflammatory responses through NF-κB activation. Runx1 also aggravated interstitial fibrosis via the TGF-β/Smad2 pathway. These combined pro-inflammatory and pro-fibrotic roles link Runx1 activity to both cyst expansion and progressive parenchymal injury.
The presented preclinical data identify Runx1 as a pivotal regulator of cyst growth and disease progression in Pkd1-based ADPKD models. Pharmacologic inhibition with Ro5-3335 reduced cyst burden, decreased epithelial proliferation, modulated key growth-signaling pathways (AKT-mTOR, MAPK/ERK, STAT3), relieved suppression of p53-dependent apoptosis, and attenuated inflammatory and fibrotic signaling (NF-κB, TGF-β/Smad2). The authors conclude that Runx1 is a promising therapeutic target in ADPKD.
Conflict of interest: the authors declare no conflicts. The source article contains detailed methods, dosing, and full experimental results; any specific procedural details not stated in the supplied abstract and figures are reported in the full text and are not inferred here.