Neural transcription factor Pou4f1 promotes renal fibrosis via macrophage–myofibroblast transition

Abstract

Unresolved inflammation can lead to tissue fibrosis and impaired organ function. Macrophage–myofibroblast transition (MMT) is one newly identified mechanism by which ongoing chronic inflammation causes progressive fibrosis in different forms of kidney disease. However, the mechanisms underlying MMT are still largely unknown. Here, we discovered a brain-specific homeobox/POU domain protein Pou4f1 (Brn3a) as a specific regulator of MMT. Interestingly, we found that Pou4f1 is highly expressed by macrophages undergoing MMT in sites of fibrosis in human and experimental kidney disease, identified by coexpression of the myofibroblast marker, α-SMA. Unexpectedly, Pou4f1 expression peaked in the early stage in renal fibrogenesis in vivo and during MMT of bone marrow-derived macrophages (BMDMs) in vitro. Mechanistically, chromatin immunoprecipitation (ChIP) assay identified that Pou4f1 is a Smad3 target and the key downstream regulator of MMT, while microarray analysis defined a Pou4f1-dependent fibrogenic gene network for promoting TGF-β1/Smad3-driven MMT in BMDMs at the transcriptional level. More importantly, using two mouse models of progressive renal interstitial fibrosis featuring the MMT process, we demonstrated that adoptive transfer of TGF-β1-stimulated BMDMs restored both MMT and renal fibrosis in macrophage-depleted mice, which was prevented by silencing Pou4f1 in transferred BMDMs. These findings establish a role for Pou4f1 in MMT and renal fibrosis and suggest that Pou4f1 may be a therapeutic target for chronic kidney disease with progressive renal fibrosis.

Magnoflorine Ameliorates Inflammation and Fibrosis in Rats With Diabetic Nephropathy by Mediating the Stability of Lysine-Specific Demethylase 3A

“…Moreover, we observed consistent results in rats challenged with STZ, corroborating the activation of the TGF-β1/Smad2/Smad3 signaling in DN development. The paramount importance of the TGF-β1/Smad signaling has been underscored in various DN pathogenesis, includes podocyte injury, mesangial cell proliferation, and especially renal fibrosis ( Isacsson et al, 1988 ; Tang et al, 2018a , b , 2020 ; Zhang et al, 2019 ; Qi et al, 2020 ). As an important regulator in the pathway, TGF-β1 has been recognized as an effective cytokine that modulates cell proliferation, differentiation, migration, and ECM turnover in the kidney ( Lan and Chung, 2012 ).…”

TGF-β1 Signaling: Immune Dynamics of Chronic Kidney Diseases

“…Mechanistically, TGF-β1/Smad3 signaling is suggested as the key regulator for initiating MMT during renal fibrosis in a UUO model in vivo , where TGF-β1 induces the de novo expression of myofibroblast marker α-SMA and effector collagen I in the bone marrow derived macrophages (BMDMs) via a Smad3-dependent mechanism ( 164 ). Bioinformatic analysis of TGF-β1/Smad3 dependent transcriptome of MMT in vitro further reveals Src and Pou4f1 as the pathogenic mediator in the Smad3 downstream signaling, representing a precise therapeutic target for blocking MMT ( 24 , 165 ). In brief, TGF-β1/Smad3 directly activates a Src-centric gene network in BMDMs via transcriptional regulation for promoting the MMT process in the fibrosing kidney ( 15 ).…”

“…In brief, TGF-β1/Smad3 directly activates a Src-centric gene network in BMDMs via transcriptional regulation for promoting the MMT process in the fibrosing kidney ( 15 ). More importantly, Tang et al further discovered the importance of a neural-specific homeobox/POU domain protein Pou4f1 in the Smad3 downstream as a specific mediator for regulating MMT ( 24 ). Besides, non-canonical TGF-β1 signaling also induces MMT via β-catenin/TCF pathway, promoting pro-fibrotic gene expression in the kidney infiltrating macrophages ( 30 , 166 ).…”

“…Besides, non-canonical TGF-β1 signaling also induces MMT via β-catenin/TCF pathway, promoting pro-fibrotic gene expression in the kidney infiltrating macrophages ( 30 , 166 ). Inhibitor of Src (PP1) and TCF (ICG-001) and BMDM-specific Pou4f1 silencing effectively suppress the MMT process and associated renal fibrosis, suggesting MMT may be therapeutically targeted to restrain CKD progression ( 24 , 165 ).…”

“…However, direct targeting of TGF-β1 signaling would affect its physiological functions in the regulation of cell differentiation, apoptosis, and immune homeostasis ( 22 ). Consequently, disease-specific pathogenic downstream of TGF-β1 pathway has been proposed to serve as an alternative therapeutic target and prognostic marker for CKD ( 23 , 24 ). Recently, emerging studies have uncovered the downstream mechanisms of TGF-β1 in both adaptive and innate immunity during CKD.…”