Crosstalk between lysine methyltransferase Smyd2 and TGF-β-Smad3 signaling promotes renal fibrosis in autosomal dominant polycystic kidney disease

Long-term expandable mouse and human-induced nephron progenitor cells enable kidney organoid maturation and modeling of plasticity and disease

Nephron progenitor cells (NPCs) self-renew and differentiate into nephrons, the functional units of the kidney. Here, manipulation of p38 and YAP activity allowed for long-term clonal expansion of primary mouse and human NPCs and induced NPCs (iNPCs) from human pluripotent stem cells (hPSCs). Molecular analyses demonstrated that cultured iNPCs closely resemble primary human NPCs. iNPCs generated nephron organoids with minimal off-target cell types and enhanced maturation of podocytes relative to published human kidney organoid protocols. Surprisingly, the NPC culture medium uncovered plasticity in human podocyte programs, enabling podocyte reprogramming to an NPC-like state. Scalability and ease of genome editing facilitated genome-wide CRISPR screening in NPC culture, uncovering genes associated with kidney development and disease. Further, NPC-directed modeling of autosomal-dominant polycystic kidney disease (ADPKD) identified a small-molecule inhibitor of cystogenesis. These findings highlight a broad application for the reported iNPC platform in the study of kidney development, disease, plasticity, and regeneration.

Inhibition of SMYD2 attenuates paraquat-induced pulmonary fibrosis by inhibiting the epithelial-mesenchymal transition through the GLIPR2/ERK/p38 axis

Paraquat (PQ) poisoning leads to irreversible fibrosis in the lungs with high mortality and no known antidote. In this study, we investigated the effect of the SET and MYND domain containing 2 (SMYD2) on PQ-induced pulmonary fibrosis (PF) and its potential mechanisms. We established an in vivo PQ-induced PF mouse model by intraperitoneal injection of PQ (20 mg/kg) and in vitro PQ (25 μM)-injured MLE-12 cell model. On the 15th day of administration, tissue injury, inflammation, and fibrosis in mice were evaluated using various methods including routine blood counts, blood biochemistry, blood gas analysis, western blotting, H&E staining, ELISA, Masson staining, and immunofluorescence. The findings indicated that AZ505 administration mitigated tissue damage, inflammation, and collagen deposition in PQ-poisoned mice. Mechanistically, both in vivo and in vitro experiments revealed that AZ505 treatment suppressed the PQ-induced epithelial-mesenchymal transition (EMT) process by downregulating GLI pathogenesis related 2 (GLIPR2) and ERK/p38 pathway. Further investigations demonstrated that SMYD2 inhibition decreased GLIPR2 methylation and facilitated GLIPR2 ubiquitination, leading to GLIPR2 destabilization in PQ-exposed MLE-12 cells. Moreover, rescue experiments conducted in vitro demonstrated that GLIPR2 overexpression eliminated the inhibitory effect of AZ505 on the ERK/p38 pathway and EMT. Our results reveal that the SMYD2 inhibitor AZ505 may act as a novel therapeutic candidate to suppress the EMT process by modulating the GLIPR2/ERK/p38 axis in PQ-induced PF.

CD74 Promotes Cyst Growth and Renal Fibrosis in Autosomal Dominant Polycystic Kidney Disease

The progression of autosomal dominant polycystic kidney disease (ADPKD), an inherited kidney disease, is associated with renal interstitial inflammation and fibrosis. CD74 has been known not only as a receptor of macrophage migration inhibitory factor (MIF) it can also have MIF independent functions. In this study, we report unknown roles and function of CD74 in ADPKD. We show that knockout of CD74 delays cyst growth in Pkd1 mutant kidneys. Knockout and knockdown of CD74 (1) normalize PKD associated signaling pathways, including ERK, mTOR and Rb to decrease Pkd1 mutant renal epithelial cell proliferation, (2) decrease the activation of NF-κB and the expression of MCP-1 and TNF-alpha (TNF-α) which decreases the recruitment of macrophages in Pkd1 mutant kidneys, and (3) decrease renal fibrosis in Pkd1 mutant kidneys. We show for the first time that CD74 functions as a transcriptional factor to regulate the expression of fibrotic markers, including collagen I (Col I), fibronectin, and α-smooth muscle actin (α-SMA), through binding on their promoters. Interestingly, CD74 also regulates the transcription of MIF to form a positive feedback loop in that MIF binds with its receptor CD74 to regulate the activity of intracellular signaling pathways and CD74 increases the expression of MIF in ADPKD kidneys during cyst progression. We further show that knockout of MIF and targeting MIF with its inhibitor ISO-1 not only delay cyst growth but also ameliorate renal fibrosis through blocking the activation of renal fibroblasts and CD74 mediated the activation of TGF-β-Smad3 signaling, supporting the idea that CD74 is a key and novel upstream regulator of cyst growth and interstitial fibrosis. Thus, targeting MIF-CD74 axis is a novel therapeutic strategy for ADPKD treatment.

Pharmacological inhibition of SMYD2 protects against cisplatin-induced renal fibrosis and inflammation

SET and MYND domain protein 2 (SMYD2) can methylate histone H3 at lysine36 (H3K36) and some non-histone substrates to play a role in tumorigenesis. However, It is unclear how SMYD2 contributes to chronic kidney disease (CKD). Here, AZ505 or LLY507, which could inhibit SMYD2, were used in cisplatin-induced CKD to investigate the effects and possible mechanisms by which they might act. We found that high expression of SMYD2 in cisplatin-induced CKD. However, AZ505 or LLY507 can significantly inhibit its expression, improve renal function injury and fibrosis induced by cisplatin, inhibit the transition of epithelial cells to a fibrogenic phenotype and fibrosis-related proteins, inhibit the expression of Inflammatory Cytokines (such as IL-6 and TNF-α), And inhibit the phosphorylation of pro-fibrosis molecule Smad3 and signal transduction and transcription activator-3 (STAT3) and up-regulated the expression of renal protective factor Smad7. In cultured tubular epithelial cells, AZ505 also can inhibit the expression of EMT, fibrosis-related proteins, and inflammatory cytokines in cisplatin-induced tubular epithelial cells. Based on these findings, SMYD2 may be a critical regulator of cisplatin-induced CKD and targeted pharmacological inhibition of SMYD2 may prevent cisplatin-induced CKD through Smad3 or STAT3-related signaling pathways.

Modeling kidney development, disease, and plasticity with clonal expandable nephron progenitor cells and nephron organoids

Nephron progenitor cells (NPCs) self-renew and differentiate into nephrons, the functional units of the kidney. Here we report manipulation of p38 and YAP activity creates a synthetic niche that allows the long-term clonal expansion of primary mouse and human NPCs, and induced NPCs (iNPCs) from human pluripotent stem cells. Cultured iNPCs resemble closely primary human NPCs, generating nephron organoids with abundant distal convoluted tubule cells, which are not observed in published kidney organoids. The synthetic niche reprograms differentiated nephron cells into NPC state, recapitulating the plasticity of developing nephron in vivo. Scalability and ease of genome-editing in the cultured NPCs allow for genome-wide CRISPR screening, identifying novel genes associated with kidney development and disease. A rapid, efficient, and scalable organoid model for polycystic kidney disease was derived directly from genome-edited NPCs, and validated in drug screen. These technological platforms have broad applications to kidney development, disease, plasticity, and regeneration.

Transcription factor FoxM1 promotes cyst growth in PKD1 mutant ADPKD

Autosomal dominant polycystic kidney disease (ADPKD) is driven by mutations in the PKD1 and PKD2 genes, and it is characterized by renal cyst formation, inflammation and fibrosis. Forkhead box protein M1 (FoxM1), a transcription factor of the Forkhead box (Fox) protein super family, has been reported to promote tumor formation, inflammation and fibrosis in many organs. However, the role and mechanism of FoxM1 in regulation of ADPKD progression is still poorly understood. Here, we show that FoxM1 is an important regulator of cyst growth in ADPKD. FoxM1 is upregulated in cyst-lining epithelial cells in Pkd1 mutant mouse kidneys and human ADPKD kidneys. FoxM1 promotes cystic renal epithelial cell proliferation by increasing the expression of Akt and Stat3 and the activation of ERK and Rb. FoxM1 also regulates cystic renal epithelial cell apoptosis through NF-κB signaling pathways. In addition, FoxM1 regulates the recruitment and retention of macrophages in Pkd1 mutant mouse kidneys, a process that is associated with FoxM1-mediated upregulation of monocyte chemotactic protein 1. Targeting FoxM1 with its specific inhibitor, FDI-6, delays cyst growth in rapidly progressing and slowly progressing Pkd1 mutant mouse kidneys. This study suggests that FoxM1 is a central and upstream regulator of ADPKD pathogenesis and provides a rationale for targeting FoxM1 as a therapeutic strategy for ADPKD treatment.

PKD1 deficiency induces Bronchiectasis in a porcine ADPKD model

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a prevalent genetic disorder, mainly characterized by the development of renal cysts, as well as various extrarenal manifestations. Previous studies have shown that ADPKD is related to bronchiectasis, while its pathogenic mechanism is unclear. In previous studies, we have generated the PKD1^+/- pigs to simulate the progression of cyst formation and physiological alterations similar to those seen in ADPKD patients.

METHODS

Phenotypic changes to airway epithelial cell and mesenchymal cell in PKD1^+/- pigs were assessed by histological analysis. The molecular mechanisms driving these processes were investigated by using PKD1^+/- pig lungs, human mesenchymal cells, and generating PKD1 deficient human epithelial cells.

RESULTS

We identified bronchiectasis in PKD1^+/- pigs, which is consistent with the clinical symptoms in ADPKD patients. The deficiency of PKD1 suppressed E-cadherin expression in the airway epithelial barrier, which aggravated invasion and leaded to a perpetuated inflammatory response. During this process, extracellular matrix (ECM) components were altered, which contributed to airway smooth muscle cell phenotype switch from a contractile phenotype to a proliferative phenotype. The effects on smooth muscle cells resulted in airway remodeling and establishment of bronchiectasis.

CONCLUSION

To our knowledge, the PKD1^+/- pig provides the first model recapitulating the pathogenesis of bronchiectasis in ADPKD. The role of PKD1 in airway epithelial suggests a potential target for development of new strategies for the diagnosis and treatment of bronchiectasis.