CASC15 Promotes Cholangiocyte Proliferation and Liver Fibrosis by Regulating the HNRNPU-IGFBP3 Axis in Biliary Atresia.

PURPOSE: Active cholangiocytes featured with massive proliferation activate hepatic stellate cells (HSCs) and could cause eventual liver fibrosis (LF), however, this crosstalk still remains unclear in biliary atresia (BA). We aimed to evaluate the involvement of cancer susceptibility candidate 15 (CASC15) in BA.

METHODS

Cholangiocyte organoid culture and sequencing was used to identify differentially expressed long noncoding RNA associated with cholangiocyte proliferation. The expression level of CASC15 were detected in liver tissues. The CCK-8, EdU assay, co-culture experiments, and subcellular fractionation were employed to investigate its function and subcellular localization. Chromatin isolation by RNA purification coupled with mass spectrometry, RNA immunoprecipitation, and RNA sequencing were utilized to clarify the underlying mechanism of CASC15.

RESULTS

CASC15 showed increased expression in cholangiocyte organoids and liver tissues of BA patients. Overexpressed CASC15 in cholangiocytes enhanced cell proliferation and promoted HSC activation in vitro. CASC15 predominantly located in the nucleus and was identified to interact with heterogeneous nuclear ribonucleoprotein U (HNRNPU) to maintain the expression of downstream target insulin-like growth factor binding protein 3 (IGFBP3), which could facilitate in the activation of HSCs.

CONCLUSION

This research revealed the crucial role of CASC15/HNRNPU-IGFBP3 regulatory network in the pathogenesis of LF in BA.