The Sympathetic Nervous System Promotes Hepatic Lymphangiogenesis, which Is Protective Against Liver Fibrosis

S-Allyl-Cysteine Ameliorates Cirrhotic Portal Hypertension by Enhancing Lymphangiogenesis via a VEGF-C-Independent Manner

BACKGROUND AND AIMS

Lymphangiogenesis is enhanced during the development of liver cirrhosis and portal hypertension (PHT). However, hepatic lymphatic vascular system is understudied in liver cirrhosis and PHT. Hydrogen sulfide (H2S) and related compounds have potential prolymphangiogenic effects besides its previously reported vascular-protective effects. Therefore, we aimed to investigate the effects of endogenous H2S donor S-allyl-cysteine (SAC) on bile duct ligation (BDL)-induced liver cirrhosis and PHT.

METHODS

BDL rats with cholestatic liver cirrhosis and PHT were orally administrated with SAC at 100 or 200 mg/kg/day, as well as DL-propargylglycine (PAG) or MAZ-51 injections. Hemodynamic parameters were determined, and subsequent evaluations of liver fibrosis, intrahepatic vascular resistance (IHVR) and lymphangiogensis were performed. Human lymphatic endothelial cells (hLECs) were used for in vitro verification of prolymphangiogenic effects of SAC.

RESULTS

SAC treatment significantly decreased PP and promoted endogenous H2S production. Liver fibrosis and IHVR were also ameliorated. Hepatic and mesenteric lymphangiogenesis were enhanced in BDL rats and further promoted by SAC despite a significant downregulation of hepatic VEGF-C. Inhibition of H2S production by PAG significantly reduced lymphatic vessels, while inhibition of lymphangiogensis by MAZ-51 reversed the protective effects of SAC against PHT. SAC enhanced lymphangiogenic functions in vitro by promoting cellular H2S production and activating Akt phosphorylation without altering VEGF-C/D, which were reversed by PAG and MAZ-51.

CONCLUSIONS

SAC significantly alleviated BDL-induced liver cirrhosis and PHT. Meanwhile, elevated H2S induced by SAC facilitated lymphangiogenesis via a VEGF-C-independent manner, which contributed to the alleviation of PHT.

Hepatic Arterial Flow-Induced Portal Tract Fibrosis in Portal Hypertension: The Role of VCAM-1 and Osteopontin-Expressing Macrophages

Background

The liver undergoes significant hemodynamic changes during surgery, transplantation, or cirrhosis with portal hypertension(PH). The hepatic artery buffer response(HABR), which compensates for reduced portal venous flow by increasing hepatic artery(HA) flow, is hypothesized to induce pathological portal tract remodeling. This study investigates the molecular mechanisms underlying this process.

Methods

PH was induced in Sprague-Dawley rats via partial portal vein ligation(PPVL). Structural evaluation(microCT), immune cell profiling, hemodynamic measurements, and transcriptomic analysis in macrophages(Mϕ) from sham or PPVL rats were conducted.

Results

MicroCT revealed decreased portal vein flow and increased HA flow correlated with portal pressure(r=0.799, p<0.01). A 2-fold increase in portal tract fibrosis(p<0.001) was observed with increased α-SMA+ myofibroblasts in PPVL rats. CD68+ Mϕ peaked at 10 days post-PPVL, and their depletion significantly reduced fibrosis(p<0.001), indicating critical roles of Mϕ in portal tract remodeling. VCAM-1 was elevated in HA endothelium and portal fibroblasts (PFs); VCAM-1 neutralization reduced collagen accumulation(p<0.05), CD68+ Mϕ(46.3%, p<0.01), and CD3+ T cells(18%, p<0.05). Mϕ-conditioned medium increased VCAM-1 in PFs(8-fold, p<0.001) and enhanced PF migration, while VCAM-1 knockdown reduced this effect (p<0.01). Single-cell RNA sequencing data(GSE171904) and RNA-FISH revealed increased interactions between osteopontin (Spp1)+ Mϕ and PFs, with Spp1+ Mϕ driving fibrosis. Spp1 knockdown in Mϕ co-culture reduced PF fibrogenic markers, while recombinant Spp1 upregulated Col1a1, Fn1, and Acta2 expression in PFs.

Conclusion

Increased VCAM-1 in arterial endothelial cells and PFs facilitates the recruitment of Spp1+ Mϕ, which drive HA flow-mediated vascular remodeling and portal tract fibrosis. These findings highlight arterial flow-induced fibrosis as a key mechanism in PH, potentially contributing to disease progression and decompensation.

Synopsis

Liver hemodynamic changes in portal hypertension drive extracellular matrix accumulation and portal tract remodeling via Spp1+ macrophages. This study highlights how altered blood flow induces fibrosis, and its potential role in decompensation, and identifies therapeutic targets for advanced liver disease.

Liver Lymphatic Dysfunction as a Driver of Fibrosis and Cirrhosis Progression

The liver lymphatic system plays a critical role in maintaining interstitial fluid balance and immune regulation. Efficient lymphatic drainage is essential for liver homeostasis, but its role in liver disease progression remains poorly understood. In cirrhosis, lymphangiogenesis initially compensates for increased lymph production, but impaired lymphatic drainage in advanced stages may lead to complications such as ascites and portal hypertension. This study aimed to evaluate how liver lymphatic dysfunction affects disease progression and to assess therapeutic strategies. Using a surgical model to block liver lymphatic outflow, we found that impaired drainage accelerates liver injury, fibrosis, and immune cell infiltration, even in healthy livers. Mechanistically, enhanced TGF-β signaling in liver lymphatic endothelial cells (LyECs) contributed to reduced lymphatic vessel (LV) density and function in late-stage decompensated cirrhosis. This dysfunction was linked to the progression from compensated to decompensated cirrhosis, particularly in patients with primary sclerosing cholangitis (PSC). Conversely, liver-specific overexpression of VEGF-C via AAV8 improved lymphatic drainage, restored LV density, reduced fibrosis, mitigated liver injury, and alleviated portal hypertension in cirrhotic rats. These findings establish impaired liver lymphatic function as a pivotal driver of cirrhosis progression and identify VEGF-C as a promising therapeutic target to prevent decompensation.

Tumor-associated lymphatic vessel density is a postoperative prognostic biomarker of hepatobiliary cancers: a systematic review and meta-analysis

Purpose

This study aimed to investigate whether tumor-associated lymphatic vessel density (LVD) could predict the survival of patients with hepato-biliary-pancreatic (HBP) cancers after radical resection.

Methods

A systematic search was conducted using PubMed, Embase, and Cochrane Library from the inception to July 31, 2024 for literature that reported the role of LVD in overall survival (OS) and recurrence-free survival (RFS) of patients with HBP cancers after radical resection.

Results

Ten studies with 761 patients were included for the meta-analysis. The results indicated that a higher level of LVD was associated with worse OS (hazard ratio, HR = 2.87, 95% CI 1.63 to 5.04) and worse RFS (HR = 3.18, 95% CI 1.41 to 7.17) in HBP cancers. Subgroup analysis based on pathological types revealed that a higher level of LVD was significantly related to worse OS in hepatocellular carcinoma (HCC) (HR = 2.35, 95% CI 1.16 to 4.78), cholangiocarcinoma (HR = 4.65, 95% CI 1.70 to 12.70), and gallbladder cancer patients (HR = 4.64, 95% CI 1.37 to 15.71). The levels of LVD were not significantly associated with OS in pancreatic adenocarcinoma patients after radical resection (HR = 1.08, 95% CI 0.61 to 1.89). Similarly, a higher level of LVD was significantly associated with worse RFS in HCC (HR = 1.92, 95% CI 1.01 to 3.65) and cholangiocarcinoma patients (HR = 4.54, 95% CI 2.10 to 9.83).

Conclusions

A higher level of LVD was a biomarker for the prediction of worse OS and RFS in patients with hepatobiliary cancers after radical resection.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42024571167.

Lymphatic vessel: origin, heterogeneity, biological functions, and therapeutic targets

Lymphatic vessels, comprising the secondary circulatory system in human body, play a multifaceted role in maintaining homeostasis among various tissues and organs. They are tasked with a serious of responsibilities, including the regulation of lymph absorption and transport, the orchestration of immune surveillance and responses. Lymphatic vessel development undergoes a series of sophisticated regulatory signaling pathways governing heterogeneous-origin cell populations stepwise to assemble into the highly specialized lymphatic vessel networks. Lymphangiogenesis, as defined by new lymphatic vessels sprouting from preexisting lymphatic vessels/embryonic veins, is the main developmental mechanism underlying the formation and expansion of lymphatic vessel networks in an embryo. However, abnormal lymphangiogenesis could be observed in many pathological conditions and has a close relationship with the development and progression of various diseases. Mechanistic studies have revealed a set of lymphangiogenic factors and cascades that may serve as the potential targets for regulating abnormal lymphangiogenesis, to further modulate the progression of diseases. Actually, an increasing number of clinical trials have demonstrated the promising interventions and showed the feasibility of currently available treatments for future clinical translation. Targeting lymphangiogenic promoters or inhibitors not only directly regulates abnormal lymphangiogenesis, but improves the efficacy of diverse treatments. In conclusion, we present a comprehensive overview of lymphatic vessel development and physiological functions, and describe the critical involvement of abnormal lymphangiogenesis in multiple diseases. Moreover, we summarize the targeting therapeutic values of abnormal lymphangiogenesis, providing novel perspectives for treatment strategy of multiple human diseases.