Biliary Epithelial Cell and Macrophage Cross‐Talk Is Important To Cyst Progression
Authors: Munteanu Maria Cristina , Sivasami Pulavendran , Ferencz Beatrix , Mansat Robert Silasi , Poudel Nabin , Watnick Terry , Lupu Florea , Hinsdale Myron 
Published: November 2023

Background & aims

Polycystic liver disease arises most commonly in patients with polycystic kidney disease that is one of the most common single gene disorders. High phenotypic variation indicates that genetic modifiers are important in disease severity. Genetic modifiers of primary mutations are factors that influence cellular behaviors and include cytokines, extracellular matrix proteins such as proteoglycans (PGs), and growth factors. Reduction in extracellular matrix PGs could disturb chemokine and growth factor concentration gradients leading to ectopic and exaggerated cellular responses. Reduced liver tissue PGs can lead to biliary cyst formation, biliary tract proliferation, fibrosis and inflammation as seen in our Xylosyltransferase II deficient mice (Xylt2−/−). Using our mouse model of reduced proteoglycans (PGs) and another orthogonal polyductin/fibrocystin deficient model, we investigated the cytokine profile and its cellular sources in liver cystic disease. From previous observations in our model of liver cystic development, we Hypothesize that biliary epithelial cells (BEC) are paramount to M2‐macrophage recruitment and activation.

Methods

Immunohistochemistry was used to evaluate inflammatory changes in pre‐cystic and cystic livers. Liver and isolated biliary tract inflammatory factors were analyzed with real‐time reverse transcription PCR (RT‐PCR) and western blots, respectively. Liver inflammatory cells were isolated and characterized by RT‐PCR and flow cytometry. Biliary tract epithelial cells (BEC) were isolated and challenged in vitro in proliferation and expression assays.

Results

We found cystic lesion progression depends on high TGFβ levels in concert with a transition from an early mixed pro‐inflammatory/pro‐repair environment to one of predominantly pro‐repair. This pro‐repair stage is driven in part by TGFβ‐2 activated BEC expressing Il4 and BEC proliferation due to synergistic activation by VEGF‐A and CCL2. The overall inflammatory profile is supported in early disease by non‐BEC liver cells and with severe cystic disease is driven by BEC and macrophages. Lastly, we show that high levels of the extracellular matrix (ECM) proteoglycan decorin are associated with cyst formation and progression, suggesting that age and ECM glycosaminoglycans (GAG) concentrations are integral to the cyst lesion

Conclusions

A feedback loop consisting of BEC proliferation and M2 macrophage activation appears to drive cyst progression. Furthermore, our study reveals that age associated changes in extracellular matrix and inflammation contribute to cystogenesis and the antagonism of TGFβ2, CCL2, and VEGF‐A could be a significant multi‐factorial approach to lessening cyst growth in genetic liver cystic disease.

Support or Funding Information

M.C. Munteanu, P. Sivasami, N. Poudel, and M.E. Hinsdale, are supported by a Research Advisory Committee grant, Oklahoma State University College of Veterinary Medicine and NIH grants P20GM103648 and DK087989. F. Lupu and R. Silasi‐Mansat are supported by NIH grant GM097747. T. Watnick is supported by NIH grants R01DK095036 and R01 DK076017. These studies used reagents provided by the Baltimore PKD Center supported by P30 DK090868.