Bioengineering of a CLiP-derived tubular biliary-duct-like structure for bile transport in vitro

Recent research progresses of bioengineered biliary stents

Bile duct lesion, including benign (eg. occlusion, cholelithiasis, dilatation, malformation) and malignant (cholangiocarcinoma) diseases, is a frequently encountered challenge in hepatobiliary diseases, which can be repaired by interventional or surgical procedures. A viable cure for bile duct lesions is implantation with biliary stents. Despite the placement achieved by current clinical biliary stents, the creation of functional and readily transplantable biliary stents remains a formidable obstacle. Excellent biocompatibility, stable mechanics, and absorbability are just a few benefits of using bioengineered biliary stents, which can also support and repair damaged bile ducts that drain bile. Additionally, cell sources & organoids derived from the biliary system that are loaded onto scaffolds can encourage bile duct regeneration. Therefore, the implantation of bioengineered biliary stent is considered as an ideal treatment for bile duct lesion, holding a broad potential for clinical applications in future. In this review, we look back on the development of conventional biliary stents, biodegradable biliary stents, and bioengineered biliary stents, highlighting the crucial elements of bioengineered biliary stents in promoting bile duct regeneration. After providing an overview of the various types of cell sources & organoids and fabrication methods utilized for the bioengineering process, we present the in vitro and in vivo applications of bioengineered biliary ducts, along with the latest advances in this exciting field. Finally, we also emphasize the ongoing challenges and future development of bioengineered biliary stents.

Mitigation of polystyrene microplastic-induced hepatotoxicity in human hepatobiliary organoids through bile extraction

BACKGROUND & AIMS

Polystyrene microplastics (PS-MPs) are pervasive in our daily life and can be ingested by the human body through bioaccumulation, causing organ damage, especially liver damage. However, the effect of PS-MPs bioaccumulation on human hepatotoxicity and their metabolism remains unclear. Recent studies have demonstrated that PS-MPs cause lipid and bile acid metabolism disorders. The human hepatobiliary organoids (HBOs) regenerated from chemically induced liver progenitor cells converted by mature hepatocytes and the bile duct provides a bioengineering model for liver disease and hepatic metabolism.

APPROACH & RESULTS

Exposure of HBOs to PS-MPs with a diameter of 1 µm for 48 h causes hepatotoxicity, hepatocyte damage, and changes in bile acid metabolism. PS-MPs could be accumulated into the bile ducts of HBOs, which can be promoted by ursodeoxycholic acid, increasing bile flow and volume by activating the bile transporter of BSEP in a dose-dependent manner along with MRP-2. The accumulation of PS-MPs in the bile duct was able to be inhibited by the bile transporter inhibitor of troglitazone that could inhibit the transporters of BSEP and MRP-2, which increased the hepatotoxicity caused by PS-MPs.

CONCLUSIONS

This study provides insights into the metabolic pathways of PS-MPs in the liver and suggests potential therapeutic strategies to reduce MP-induced liver damage.

Efficacy of chemically induced human hepatic progenitor cells from diseased liver against nonalcoholic steatohepatitis model

BACKGROUND

Numerous chemical reprogramming techniques have been reported, rendering them applicable to regenerative medicine research. The aim of our study was to evaluate the therapeutic potential of human CLiP derived from clinical specimens transplanted into a nonalcoholic steatohepatitis (NASH) mouse model of liver fibrosis.

METHODS

We successfully generated chemically induced liver progenitor (CLiP), which exhibited progenitor-like characteristics, through stimulation with low-molecular-weight compounds. We elucidated their cell differentiation ability and therapeutic effects. However, the therapeutic efficacy of human CLiP generated from clinical samples on liver fibrosis, such as liver cirrhosis, remains unproven.

RESULTS

Following a 4 week period, transplanted human CLiP in the NASH model differentiated into mature hepatocytes and demonstrated suppressive effects on liver injury markers (i.e., aspartate transaminase and alanine transaminase). Although genes related to inflammation and fat deposition did not change in the human CLiP transplantation group, liver fibrosis-related factors (Acta2 and Col1A1) showed suppressive effects on gene expression following transplantation, with approximately a 60% reduction in collagen fibers. Importantly, human CLiP could be efficiently induced from hepatocytes isolated from the cirrhotic liver, underscoring the feasibility of using autologous hepatocytes to produce human CLiP.

CONCLUSION

Our findings demonstrate the effectiveness of human CLiP transplantation as a viable cellular therapy for liver fibrosis, including NASH liver. These results hold promise for the development of liver antifibrosis therapy utilizing human CLiP within the field of liver regenerative medicine.

Generation of human hepatobiliary organoids with a functional bile duct from chemically induced liver progenitor cells

BACKGROUND

Liver disease imposes a significant medical burden that persists due to a shortage of liver donors and an incomplete understanding of liver disease progression. Hepatobiliary organoids (HBOs) could provide an in vitro mini-organ model to increase the understanding of the liver and may benefit the development of regenerative medicine.

METHODS

In this study, we aimed to establish HBOs with bile duct (BD) structures and mature hepatocytes (MHs) using human chemically induced liver progenitor cells (hCLiPs). hCLiPs were induced in mature cryo-hepatocytes using a small-molecule cocktail of TGF-β inhibitor (A-83-01, A), GSK3 inhibitor (CHIR99021, C), and 10% FBS (FAC). HBOs were then formed by seeding hCLiPs into ultralow attachment plates and culturing them with a combination of small molecules of Rock-inhibitor (Y-27632) and AC (YAC).

RESULTS

These HBOs exhibited bile canaliculi of MHs connected to BD structures, mimicking bile secretion and transportation functions of the liver. The organoids showed gene expression patterns consistent with both MHs and BD structures, and functional assays confirmed their ability to transport the bile analogs of rhodamine-123 and CLF. Functional patient-specific HBOs were also successfully created from hCLiPs sourced from cirrhotic liver tissues.

CONCLUSIONS

This study demonstrated the potential of human HBOs as an efficient model for studying hepatobiliary diseases, drug discovery, and personalized medicine.

Reprogramming canine cryopreserved hepatocytes to hepatic progenitor cells using small molecule compounds

Introduction

Exploring techniques for differentiating and culturing canine hepatocytes serves as a means to establish systems for liver transplantation and drug metabolism testing. However, establishing consistent methods for culturing stable hepatocytes remains a challenge. Recently, several investigations have shown the reprogramming of mature hepatocytes into hepatic progenitor cells by applying specific small molecule compounds, including Y-27632, (a ROCK inhibitor), A-83-01 (a TGFβ inhibitor), and CHIR99021 (a GSK3 inhibitor) (termed YAC) in rat, mouse, and humans, respectively. However, reports or evidence of successful reprogramming using these small-molecule compounds in dogs are absent. This study aimed to induce the differentiation of mature canine hepatocytes into progenitor cells.

Methods

Cryopreserved canine hepatocytes (cHep) were cultured for 14 d in a YAC-supplemented hepatocyte growth medium. Subsequently, an assessment was conducted involving morphological observations, quantitative real-time polymerase chain reaction (qRT-PCR), and immunocytochemistry.

Results

Notably, cryopreserved cHep cells emerged and exhibited ongoing proliferation and concurrently developed colonies within the YAC-enriched culture. These observations indicated that the mature hepatocytes reprogrammed into hepatic progenitor cells. Moreover, qRT-PCR analysis revealed a notable enhancement in gene expression levels. Specifically, the genes encoding α-fetoprotein (AFP), epithelial cell adhesion molecule (EpCAM), Cytokeratin 19 (CK19) and SRY-box9 (Sox9) displayed approximately 12-, 2.2-, 517- and 2.9- increases in hepatic progenitor cells, respectively, on day 14 as compared to their state before induction of differentiation. Hepatocyte-related protein expression of AFP, EPCAM, SOX9 and CK19 was confirmed via immunocytochemistry on day 21. In contrast, ALB and MRP2, which are highly expressed in mature hepatocytes, were decreased compared to those before YAC addition, which is consistent with the characteristics of undifferentiated hepatocytes.

Conclusions

Herein, we effectively promoted the reprogramming of cryopreserved cHep cells into hepatic progenitor cells using three small-molecule compounds. The mRNA and protein expression analyses demonstrated increased levels of hepatic progenitor cells-specific markers, whereas markers related to mature hepatocytes decreased, suggesting that reprogramming cryopreserved cHep cells to hepatic progenitor cells was achieved using YAC. Therefore, cultivating liver progenitor cells holds the potential to offer valuable insights into the development of artificial livers for drug discovery research and transplantation therapy aimed at addressing liver diseases in dogs.

Modulation of hepatic cellular tight junctions via coculture with cholangiocytes enables non-destructive bile recovery

Estimation of the biliary clearance of drugs and their metabolites in humans is crucial for characterizing hepatobiliary disposition and potential drug-drug interactions. Sandwich-cultured hepatocytes, while useful for in vitro bile analysis, require cell destruction for bile recovery, limiting long-term or repeated dose drug effect evaluations. To overcome this limitation, we investigated the feasibility of coculturing a human hepatic carcinoma cell line (HepG2-NIAS cells) and a human cholangiocarcinoma cell line (TFK-1 cells) using the collagen vitrigel membrane in a variety of coculture configurations. The coculture configuration with physiological bile flow increased the permeability of fluorescein-labeled bile acids (CLF) across the HepG2-NIAS cell layer by approximately 1.2-fold compared to the HepG2-NIAS monoculture. This enhancement was caused by paracellular leakage due to the loosened tight junctions of HepG2-NIAS, confirmed by the use of an inhibitor for bile acid transporters, the increase of permeability of dextran, and the decrease of the transepithelial electrical resistance (TEER) value. Based on the results of loosening hepatic tight junctions via coculture with TFK-1 in the CLF permeability assay, we next attempted to collect the CLF accumulated in the bile canaliculi of HepG2-NIAS. The recovery of the CLF accumulated in the bile canaliculi was increased 1.4 times without disrupting hepatic tight junctions by the coculture of HepG2-NIAS cells and TFK-1 cells compared to the monoculture of HepG2-NIAS cells. This non-destructive bile recovery has the potential as a tool for estimating the biliary metabolite and provides valuable insights to improve in vitro bile analysis.

Three-dimensional human bile duct formation from chemically induced human liver progenitor cells

Background: The intrahepatic bile ducts (BDs) play an important role in the modification and transport of bile, and the integration between the BD and hepatocytes is the basis of the liver function. However, the lack of a source of cholangiocytes limits in vitro research. The aim of the present study was to establish three-dimensional BDs combined with human mature hepatocytes (hMHs) in vitro using chemically induced human liver progenitor cells (hCLiPs) derived from hMHs. Methods: In this study, we formed functional BDs from hCLiPs using hepatocyte growth factor and extracellular matrix. BDs expressed the typical biliary markers CK-7, GGT1, CFTR and EpCAM and were able to transport the bile-like substance rhodamine 123 into the lumen. The established three-dimensional BDs were cocultured with hMHs. These cells were able to bind to the BDs, and the bile acid analog CLF was transported from the culture medium through the hMHs and accumulated in the lumen of the BDs. The BDs generated from the hCLiPs showed a BD function and a physiological system (e.g., the transport of bile within the liver) when they were connected to the hMHs. Conclusion: We present a novel in vitro three-dimensional BD combined with hMHs for study, drug screening and the therapeutic modulation of the cholangiocyte function.

Evidence for in vitro extensive proliferation of adult hepatocytes and biliary epithelial cells

Over the last several years, a method has emerged that endows adult hepatocytes with in vitro proliferative capacity, producing chemically induced liver progenitors (CLiPs). However, there is a growing controversy regarding the origin of these cells. Here, we provide lineage tracing-based evidence that adult hepatocytes acquire proliferative capacity in vitro using rat and mouse models. Unexpectedly, we also found that the CLiP method allows biliary epithelial cells to acquire extensive proliferative capacity. Interestingly, after long-term culture, hepatocyte-derived cells (hepCLiPs) and biliary epithelial cell-derived cells (bilCLiPs) become similar in their gene expression patterns, and they both exhibit differentiation capacity to form hepatocyte-like cells. Finally, we provide evidence that hepCLiPs can repopulate injured mouse livers, reinforcing our earlier argument that CLiPs can be a cell source for liver regenerative medicine. This study advances our understanding of the origin of CLiPs and motivates the application of this technique in liver regenerative medicine.

Biomechanical Behaviors and Degradation Properties of Multilayered Polymer Scaffolds: The Phase Space Method for Bile Duct Design and Bioengineering

This article reports the electrospinning technique for the manufacturing of multilayered scaffolds for bile duct tissue engineering based on an inner layer of polycaprolactone (PCL) and an outer layer either of a copolymer of D,L-lactide and glycolide (PLGA) or a copolymer of L-lactide and ε-caprolactone (PLCL). A study of the degradation properties of separate polymers showed that flat PCL samples exhibited the highest resistance to hydrolysis in comparison with PLGA and PLCL. Irrespective of the liquid-phase nature, no significant mass loss of PCL samples was found in 140 days of incubation. The PLCL- and PLGA-based flat samples were more prone to hydrolysis within the same period of time, which was confirmed by the increased loss of mass and a significant reduction of weight-average molecular mass. The study of the mechanical properties of developed multi-layered tubular scaffolds revealed that their strength in the longitudinal and transverse directions was comparable with the values measured for a decellularized bile duct. The strength of three-layered scaffolds declined significantly because of the active degradation of the outer layer made of PLGA. The strength of scaffolds with the PLCL outer layer deteriorated much less with time, both in the axial (p-value = 0.0016) and radial (p-value = 0.0022) directions. A novel method for assessment of the physiological relevance of synthetic scaffolds was developed and named the phase space approach for assessment of physiological relevance. Two-dimensional phase space (elongation modulus and tensile strength) was used for the assessment and visualization of the physiological relevance of scaffolds for bile duct bioengineering. In conclusion, the design of scaffolds for the creation of physiologically relevant tissue-engineered bile ducts should be based not only on biodegradation properties but also on the biomechanical time-related behavior of various compositions of polymers and copolymers.

Promotion of Cyst Formation from a Renal Stem Cell Line Using Organ-Specific Extracellular Matrix Gel Format Culture System

Researchers have long awaited the technology to develop an in vitro kidney model. Here, we establish a rapid fabricating technique for kidney-like tissues (cysts) using a combination of an organ-derived extracellular matrix (ECM) gel format culture system and a renal stem cell line (CHK-Q cells). CHK-Q cells, which are spontaneously immortalized from the renal stem cells of the Chinese hamster, formed renal cyst-like structures in a type-I collagen gel sandwich culture on day 1 of culture. The cysts fused together and expanded while maintaining three-dimensional structures. The expression of genes related to kidney development and maturation was increased compared with that in a traditional monolayer. Under the kidney-derived ECM (K-ECM) gel format culture system, cyst formation and maturation were induced rapidly. Gene expressions involved in cell polarities, especially for important material transporters (typical markers Slc5a1 and Kcnj1), were restored. K-ECM composition was an important trigger for CHK-Q cells to promote kidney-like tissue formation and maturation. We have established a renal cyst model which rapidly expressed mature kidney features via the combination of K-ECM gel format culture system and CHK-Q cells.

Self-Organogenesis from 2D Micropatterns to 3D Biomimetic Biliary Trees

BACKGROUND AND AIMS

Globally, liver diseases account for 2 million deaths per year. For those with advanced liver disease the only curative approach is liver transplantation. However, less than 10% of those in need get a liver transplant due to limited organ availability. To circumvent this challenge, there has been a great focus in generating a bioengineered liver. Despite its essential role in liver functions, a functional biliary system has not yet been developed. In this framework, exploration of epithelial cell self-organogenesis and microengineering-driven geometrical cell confinement allow to envision the bioengineering of a functional biomimetic intrahepatic biliary tract.

APPROACH

three-dimensional (3D) bile ducts were built in vitro by restricting cell adhesion to two-dimensional (2D) patterns to guide cell self-organization. Tree shapes mimicking the configuration of the human biliary system were micropatterned on glass slides, restricting cell attachment to these areas. Different tree geometries and culture conditions were explored to stimulate self-organogenesis of normal rat cholangiocytes (NRCs) used as a biliary cell model, either alone or in co-culture with human umbilical endothelial cells (HUVECs).

RESULTS

Pre-seeding the micropatterns with HUVECs promoted luminogenesis with higher efficiency to yield functional branched biliary tubes. Lumen formation, apico-basal polarity, and preservation of the cholangiocyte phenotype were confirmed. Moreover, intact and functional biliary structures were detached from the micropatterns for further manipulation.

CONCLUSION

This study presents physiologically relevant 3D biliary duct networks built in vitro from 2D micropatterns. This opens opportunities for investigating bile duct organogenesis, physiopathology, and drug testing.