Disrupted BMP-9 Signaling Impairs Pulmonary Vascular Integrity in Hepatopulmonary Syndrome

RATIONALE

Hepatopulmonary syndrome (HPS) is a severe complication of liver diseases characterized by abnormal dilatation of pulmonary vessels, resulting in impaired oxygenation. Recent research highlights the pivotal role of liver-produced bone morphogenetic protein (BMP)-9 in maintaining pulmonary vascular integrity.

OBJECTIVES

This study aimed to investigate the involvement of BMP-9 in human and experimental HPS.

METHODS

Circulating BMP-9 levels were measured in 63 healthy controls and 203 cirrhotic patients, with or without HPS. Two animal models of portal hypertension were employed: common bile duct ligation (CBDL) with cirrhosis and long-term partial portal vein ligation (PPVL) without cirrhosis. Additionally, the therapeutic effect of low-dose BMP activator FK506 was investigated, and the pulmonary vascular phenotype of BMP-9 knockout rats was analyzed.

MEASUREMENTS AND MAIN RESULTS

Patients with HPS related to compensated cirrhosis demonstrated lower levels of circulating BMP-9 compared to patients without HPS. Severe cirrhosis patients exhibited consistently low levels of BMP-9. In animal models, HPS characteristics, including intrapulmonary vascular dilations (IPVDs) and alveolo-arterial gradient enlargement, were observed. HPS development in both rat models correlated with reduced intrahepatic BMP-9 expression, decreased circulating BMP-9 level and activity, and impaired pulmonary BMP-9 endothelial pathway. Daily treatment with FK506 for 2-weeks restored BMP pathway in the lungs, alleviating IPVDs, and improving gas exchange impairment. Furthermore, BMP-9 knockout rats displayed a pulmonary HPS phenotype, supporting its role in disease progression.

CONCLUSION

The study findings suggest that portal hypertension-induced loss of BMP-9 signaling contributes to HPS development.

Prevalence and determinants of hepatopulmonary syndrome in decompensated chronic liver disease

BACKGROUND

One of the severe complications of liver disease is hepatopulmonary syndrome (HPS). There is paucity in literature regarding the various factors associated with the development of HPS. This study was conducted to analyze the prevalence and determinants of HPS among patients with decompensated chronic liver disease (CLD).

METHODS

This study was a cross-sectional-observational study conducted in a tertiary care center. Decompensated CLD patients admitted for pre-liver transplant workup were included in the study. Demographic data, clinical findings, and biochemical and hematologic parameters were collected. Pulse oximetry, arterial blood gas analysis, bubble contrast echocardiogram, diffusion capacity of the lungs for carbon monoxide (DLCO), and spirometry were done to get the needed parameters. All data were entered into a Microsoft Excel sheet and analyzed using the statistical software SPSS for Windows, version 22.0.

RESULTS

Among 64 subjects, 58 were men (90.6%). Mean age was 54.5 years. HPS was present in 26 (40.6%) patients. Platypnea and orthodeoxia were present more often in HPS patients. DLCO was significantly impaired among patients with HPS. Portopulmonary hypertension was seen in 8 (12.5%) subjects with no difference between HPS and non-HPS patients. Subjects with HPS had more severe liver disease. A model for end-stage liver disease (MELD)-Na score > 19 was associated with HPS (sensitivity 73.08%, specificity 65.79%, PPV 59.4%, and NPV 78.1%). Multivariate analysis (binary logistic regression) revealed that a higher MELD-Na score, hepatic encephalopathy, and impaired DLCO were independently associated with HPS.

CONCLUSIONS

HPS is associated with more severe liver disease (as per Child-Turcotte-Pugh [CTP] stage and MELD-Na score). There was no relation between HPS and causes of CLD. Higher MELD-Na score, hepatic encephalopathy, impaired DLCO, clubbing, and spider naevi were independently associated with HPS.

[Diagnosis and therapeutic strategies for hepatopulmonary syndrome]

Hepatopulmonary syndrome (HPS) is a common pulmonary complication in patients with liver disease and / or portal hypertension, and is characterized by abnormal arterial oxygenation caused by intrapulmonary vascular dilatation. The pathogenesis of HPS is complex, with a low clinical early diagnosis rate and poor prognosis. HPS currently lacks effective therapeutic drugs; therefore, liver transplantation is the only fundamental treatment. This article summarizes the pathogenesis, clinical manifestations, diagnosis and treatment of HPS in order to further improve the level of clinical screening and diagnosis and treatment of HPS.