Introduction

Portal hypertension (PHT) most commonly due to cirrhosis, but non-cirrhotic portal hypertension (NCPH) related to metabolic dysfunction, specifically metabolic dysfunction-associated steatotic liver disease (MASLD), necessitates further clarification of its mechanisms and identification of therapeutic targets.

PHT may precede the development of hepatic fibrosis in MASLD, and even serve as a driving factor in the pathogenesis of MASLD. Consequently, metabolic dysfunction-associated PHT might not depend on structural alterations such as hepatic fibrosis or pseudolobule formation, but rather correlate with other factors such as endothelial dysfunction, which has been demonstrated to play a pivotal role in NCPH. Endothelial dysfunction encompasses endothelial injury and endothelial-to-mesenchymal transition (EndMT), the latter being a specific type of epithelial-to-mesenchymal transition (EMT). As reported, the JAK/STAT3 signaling pathway plays a pivotal role in the initiation and progression of EMT. Similarly, patients with NCPH induced by myeloproliferative neoplasms (MPN) often lack pathological features such as hepatic fibrosis or pseudolobule formation. The Janus kinase 2 (JAK2) V617F mutation is highly prevalent in MPN patients. Therefore, targeted inhibition of JAK2 serves as an effective therapeutic strategy for MPN.

Given the shared pathological features between MPN-associated portal hypertension and MASLD-associated portal hypertension, as well as the vital​ role of JAK2 in both disease, the application of JAK2 inhibitor holds significant therapeutic potential for metabolic dysfunction-associated portal hypertension.

Aims & Methods

This study aims to verify the therapeutic efficacy of JAK2 inhibition in attenuating MASLD-associated PHT, with particular focus on its modulation of EndMT. Mice were fed with a high-fat diet (HFD) diet for 12 weeks to induce MASLD-associated PHT and divided into two groups, the treatment group (Rux) and control (Ctr) group. Ruxolitinib (JAK2 inhibitor) was given as a suspension by gavage (60 mg/kg in 0.2 ml) every two days for 3 weeks, while controls received the same volume of saline, from week 10-12 of feeding. Portal pressure was measured, serological analysis and histopathological staining were performed. RT-PCR and Western Blot were conducted to measure EndMT-related genes expression.

Results

The treatment group (Rux) demonstrated a significant reduction in directly measured portal pressure, with concordant changes observed in the spleen-to-body weight ratio, which served as an indirect indicator of portal pressure. Concurrent improvement was noted in ALT, AST and TC. H&E, Masson and Sirius red staining showed decreased perisinusoidal and perivascular fibrosis in the Rux group. Electron microscopy revealed restoration of endothelial fenestration. Additionally, ruxolitinib treatment led to downregulation of endothelial damage markers, mesenchymal cell markers as well as EndMT-related regulatory factors, indicating an alleviation of EndMT and endothelial dysfunction.

Conclusion

The JAK2 inhibitor demonstrates therapeutic potential for MASLD-associated PHT through modulation of endothelial dysfunction and EndMT. These mechanistic insights position ruxolitinib as a promising candidate for clinical management of NCPH, particularly in the MASLD-associated PHT.

References

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