The Protective Effect of Transplanting Liver Cells Into the Mesentery on the Rescue of Acute Liver Failure After Massive Hepatectomy

Improvement in aged liver regeneration using cell transplantation with chemically induced liver progenitors

BACKGROUND

A decrease in the regenerative capacity of age-damaged liver tissue has been reported. Liver progenitor cells may play an important role in the regeneration of injured livers. In the present study we aimed to investigate improvements in the regenerative capacity of age-damaged livers using chemically induced liver progenitors (CLiPs) derived from mature hepatocytes.

METHODS

Old (>90 weeks) and young (<20 weeks) mice underwent 70% hepatectomy, with or without trans-splenic CLiP administration. The residual liver/bodyweight (LW/BW) ratio was measured on postoperative days 1 and 7, and changes in liver regeneration and histology were evaluated.

RESULTS

At 7 days post-hepatectomy, LW/BW ratios were significantly better in CLiP-treated old mice than in untreated old mice (p = .02). By contrast, no effect of CLiP transplantation was observed in young mice (p = .62). Immunofluorescence staining of liver tissue after CLiP administration showed an increase in Ki67-positive cells (p < .01). Flow cytometry analysis of green fluorescent protein-labeled CLiPs indicated that transplanted CLiPs differentiated into mature hepatocytes and were present in the recipient liver.

CONCLUSIONS

CLiP transplantation appears to ameliorate the age-related decline in liver regeneration in mice.

Liver ductal organoids reconstruct intrahepatic biliary trees in decellularized liver grafts

Three-dimensional scaffolds decellularized from native organs are a promising technique to establish engineered liver grafts and overcome the current shortage of donor organs. However, limited sources of bile duct cells and inappropriate cell distribution in bioengineered liver grafts have hindered their practical application. Organoid technology is anticipated to be an excellent tool for the advancement of regenerative medicine. In the present study, we reconstructed intrahepatic bile ducts in a rat decellularized liver graft by recellularization with liver ductal organoids. Using an ex vivo perfusion culture system, we demonstrated the biliary characteristics of repopulated mouse liver organoids, which maintained bile duct markers and reconstructed biliary tree-like networks with luminal structures. We also established a method for the co-recellularization with engineered bile ducts and primary hepatocytes, revealing the appropriate cell distribution to mimic the native liver. We then utilized this model in human organoids to demonstrate the reconstructed bile ducts. Our results show that liver ductal organoids are a potential cell source for bile ducts from bioengineered liver grafts using three-dimensional scaffolds.

Syngeneic implantation of mouse hepatic progenitor cell-derived three-dimensional liver tissue with dense collagen fibrils

BACKGROUND

Liver transplantation is a therapy for irreversible liver failure; however, at present, donor organs are in short supply. Cell transplantation therapy for liver failure is still at the developmental stage and is critically limited by a shortage of human primary hepatocytes.

AIM

To investigate the possibility that hepatic progenitor cells (HPCs) prepared from the portal branch-ligated hepatic lobe may be used in regenerative medicine, we attempted to enable the implantation of extracellular matrices containing organoids consisting of HPC-derived hepatocytes and non-parenchymal cells.

METHODS

In vitro liver organoid tissue has been generated by accumulating collagen fibrils, fibroblasts, and HPCs on a mesh of polylactic acid fabric using a bioreactor; this was subsequently implanted into syngeneic wild-type mice.

RESULTS

The in vitro liver organoid tissues generated transplantable tissues in the condensed collagen fibril matrix and were obtained from the mouse through partial hepatectomy.

CONCLUSION

Liver organoid tissue was produced from expanded HPCs using an originally designed bioreactor system. This tissue was comparable to liver lobules, and with fibroblasts embedded in the network collagen fibrils of this artificial tissue, it is useful for reconstructing the hepatic interstitial structure.

The Efficacy of the Hepatocyte Spheroids for Hepatocyte Transplantation

The safety and short-term efficacy of hepatocyte transplantation (HCTx) have been widely proven. However, issues such as reduced viability and/or function of hepatocytes, insufficient engraftment, and lack of a long-term effect have to be overcome for widespread application of HCTx. In this study, we evaluated hepatocyte spheroids (HSs), formed by self-aggregation of hepatocytes, as an alternative to hepatocytes in single-cell suspension. Hepatocytes were isolated from C57BL/6 J mice liver using a three-step collagenase perfusion technique and HSs were formed by the hanging drop method. After the spheroids formation, the HSs showed significantly higher mRNA expression of albumin, ornithine transcarbamylase, glucose-6-phosphate, alpha-1-antitrypsin, low density lipoprotein receptor, coagulation factors, and apolipoprotein E (ApoE) than 2 dimensional (2D)-cultured hepatocytes (p < 0.05). Albumin production by HSs was significantly higher than that by 2D-cultured hepatocytes (9.5 ± 2.5 vs 3.5 ± 1.8 μg/dL, p < 0.05). The HSs, but not single hepatocytes, maintained viability and albumin mRNA expression in suspension (92.0 ± 2.8% and 1.03 ± 0.09 at 6 h). HSs (3.6 × 10⁶ cells) or isolated hepatocytes (fSH, 3.6 × 10⁶ cells) were transplanted into the liver of ApoE knockout (KO-/-) mice via the portal vein. Following transplantation, serum ApoE concentration (ng/mL) of HS-transplanted mice (1w: 63.1 ± 56.7, 4w: 17.0 ± 10.9) was higher than that of fSH-transplanted mice (1 w: 33.4 ± 13.0, 4w: 13.7 ± 9.6). In both groups, the mRNA levels of pro-inflammatory cytokines (IL-6, IL-1β, TNF-α, MCP-1, and MIP-1β) were upregulated in the liver following transplantation; however, no significant differences were observed. Pathologically, transplanted HSs were observed as flat cell clusters in contact with the portal vein wall on day 7. Additionally, ApoE positive cells were observed in the liver parenchyma distant from the portal vein on day 28. Our results indicate that HS is a promising alternative to single hepatocytes and can be applied for HCTx.

Establishment of practical recellularized liver graft for blood perfusion using primary rat hepatocytes and liver sinusoidal endothelial cells

Tissue decellularization produces a three-dimensional scaffold that can be used to fabricate functional liver grafts following recellularization. Inappropriate cell distribution and clotting during blood perfusion hinder the practical use of recellularized livers. Here we aimed to establish a seeding method for the optimal distribution of parenchymal and endothelial cells, and to evaluate the effect of liver sinusoidal endothelial cells (LSECs) in the decellularized liver. Primary rat hepatocytes and LSECs were seeded into decellularized whole-liver scaffolds via the biliary duct and portal vein, respectively. Biliary duct seeding provided appropriate hepatocyte distribution into the parenchymal space, and portal vein-seeded LSECs simultaneously lined the portal lumen, thereby maintaining function and morphology. Hepatocytes co-seeded with LSECs retained their function compared with those seeded alone. Platelet deposition was significantly decreased and hepatocyte viability was maintained in the co-seeded group after extracorporeal blood perfusion. In conclusion, our seeding method provided optimal cell distribution into the parenchyma and vasculature according to the three-dimensional structure of the decellularized liver. LSECs maintained hepatic function, and supported hepatocyte viability under blood perfusion in the engineered liver graft owing to their antithrombogenicity. This recellularization procedure could help produce practical liver grafts with blood perfusion.

Identification of keratin 19-positive cancer stem cells associating human hepatocellular carcinoma using CYFRA 21-1

The current lack of an easily measurable surrogate marker of cancer stem cells (CSCs) prevents the clinical application of CSCs for hepatocellular carcinoma (HCC). We previously reported that keratin 19 (K19) is a novel HCC‐CSC marker associated with transforming growth factor beta (TGFβ)/Smad signaling, and that K19⁺ HCC‐CSCs could be a new therapeutic target of TGFβ receptor 1 inhibitor LY2157299. In this study, we examined whether K19⁺ HCC‐CSCs can be tracked using cytokeratin 19 fragment CYFRA 21‐1. In 147 HCC patients who underwent curative resection and evaluated K19 expression by immunohistochemistry, preoperative serum CYFRA 21‐1 levels were significantly higher in K19⁺ patients than in K19⁻ patients (P < 0.01). Receiver operating characteristic analyses revealed that serum CYFRA 21‐1 was the statistically significant and the most sensitive predictor of tumor K19 expression among preoperative laboratory test values (P < 0.001). In HCC cells encoding with a K19 promoter‐driven enhanced green fluorescent protein, fluorescence‐activated cell sorting (FACS)‐isolated K19⁺ cells displayed significantly higher levels of supernatant CYFRA 21‐1 than K19⁻ cells (P < 0.01). Gain/loss of K19 function experiments confirmed that CYFRA 21‐1 levels were regulated by K19 function in HCC cells. Furthermore, CYFRA 21‐1 levels reflected the treatment efficacy of LY2157299 in K19⁺ cells. In conclusion, CYFRA 21‐1 can be used to predict K19 expression in HCC, and should thereby aid in the development of novel therapeutic strategies targeting K19⁺ HCC‐CSCs.

Generation of non-viral, transgene-free hepatocyte like cells with piggyBac transposon

Somatic cells can be reprogrammed to induced hepatocyte-like cells (iHeps) by overexpressing certain defined factors in direct reprogramming techniques. Of the various methods to deliver genes into cells, typically used genome-integrating viral vectors are associated with integration-related adverse events such as mutagenesis, whereas non-integrating viral vectors have low efficiency, making viral vectors unsuitable for clinical application. Therefore, we focused on developing a transposon system to establish a non-viral reprogramming method. Transposons are unique DNA elements that can be integrated into and removed from chromosomes. PiggyBac, a type of transposon, has high transduction efficiency and cargo capacity, and the integrated transgene can be precisely excised in the presence of transposase. This feature enables the piggyBac vector to achieve efficient transgene expression and a transgene-free state, thus making it a promising method for cell reprogramming. Here, we attempted to utilize the piggyBac transposon system to generate iHeps by integrating a transgene consisting of Hnf4a and Foxa3, and successfully obtained functional iHeps. We then demonstrated removal of the transgene to obtain transgene-free iHeps, which still maintained hepatocyte functions. This non-viral, transgene-free reprogramming method using the piggyBac vector may facilitate clinical applications of iHeps in upcoming cell therapy.

Efficient recellularisation of decellularised whole-liver grafts using biliary tree and foetal hepatocytes

A whole-organ regeneration approach, using a decellularised xenogeneic liver as a scaffold for the construction of a transplantable liver was recently reported. Deriving suitable scaffolds was the first step towards clinical application; however, effective recellularisation remains to be achieved. This report presents a strategy for the improvement of the recellularisation process, using novel cell-seeding technique and cell source. We evaluated recellularised liver grafts repopulated through the portal vein or the biliary duct with mice adult hepatocytes or E14.5 foetal hepatocytes. More than 80% of the cells seeded through the biliary tree entered the parenchyma beyond the ductule-lining matrix barrier and distributed throughout the liver lobule. In contrast, about 20% of the cells seeded through the portal tree entered the parenchyma. The gene expression levels of foetal hepatocyte albumin, glucose 6-phosphatase, transferrin, cytokeratin 19, and gamma-glutamyl transpeptidase were increased in three-dimensional cultures in the native liver-derived scaffolds, and the activation of liver detoxification enzymes and formation of biliary duct-like structures were supported. The metabolic functions of liver grafts recellularised with different cell types were similar. These results suggest that biliary tree cell-seeding approach is promising, and that liver progenitor cells represent a good cell source candidate.