Analysis of decellularized mouse liver fragment and its recellularization with human endometrial mesenchymal cells as a candidate for clinical usage

Liver tissue engineering using decellularized scaffolds: Current progress, challenges, and opportunities

Liver transplantation represents the only definitive treatment for patients with end-stage liver disease. However, the shortage of liver donors provokes a dramatic gap between available grafts and patients on the waiting list. Whole liver bioengineering, an emerging field of tissue engineering, holds great potential to overcome this gap. This approach involves two main steps; the first is liver decellularization and the second is recellularization. Liver decellularization aims to remove cellular and nuclear materials from the organ, leaving behind extracellular matrices containing different structural proteins and growth factors while retaining both the vascular and biliary networks. Recellularization involves repopulating the decellularized liver with appropriate cells, theoretically from the recipient patient, to reconstruct the parenchyma, vascular tree, and biliary network. The aim of this review is to identify the major advances in decellularization and recellularization strategies and investigate obstacles for the clinical application of bioengineered liver, including immunogenicity of the designed liver extracellular matrices, the need for standardization of scaffold fabrication techniques, selection of suitable cell sources for parenchymal repopulation, vascular, and biliary tree reconstruction. In vivo transplantation models are also summarized for evaluating the functionality of bioengineered livers. Finally, the regulatory measures and future directions for confirming the safety and efficacy of bioengineered liver are also discussed. Addressing these challenges in whole liver bioengineering may offer new solutions to meet the demand for liver transplantation and improve patient outcomes.

Liver click dECM hydrogels for engineering hepatic microenvironments

Decellularized extracellular matrix (dECM) hydrogels provide tissue-specific microenvironments which accommodate physiological cellular phenotypes in 3D in vitro cell cultures. However, their formation hinges on collagen fibrillogenesis, a complex process which limits regulation of physicochemical properties. Hence, achieving reproducible results with dECM hydrogels poses as a challenge. Here, we demonstrate that thiolation of solubilized liver dECM enables rapid formation of covalently crosslinked hydrogels via Michael-type addition, allowing for precise control over mechanical properties and superior organotypic biological activity. Investigation of various decellularization methodologies revealed that treatment of liver tissue with Triton X-100 and ammonium hydroxide resulted in near complete DNA removal with significant retention of the native liver proteome. Chemical functionalization of pepsin-solubilized liver dECMs via 1-ethyl-3(3-dimethylamino)propyl carbodiimide (EDC)/N-hydroxysuccinimide (NHS) coupling of l-Cysteine created thiolated liver dECM (dECM-SH), which rapidly reacted with 4-arm polyethylene glycol (PEG)-maleimide to form optically clear hydrogels under controlled conditions. Importantly, Young's moduli could be precisely tuned between 1 - 7 kPa by varying polymer concentrations, enabling close replication of healthy and fibrotic liver conditions in in vitro cell cultures. Click dECM-SH hydrogels were cytocompatible, supported growth of HepG2 and HepaRG liver cells, and promoted liver-specific functional phenotypes as evidenced by increased metabolic activity, as well CYP1A2 and CYP3A4 activity and excretory function when compared to monolayer culture and collagen-based hydrogels. Our findings demonstrate that click-functionalized dECM hydrogels offer a highly controlled, reproducible alternative to conventional tissue-derived hydrogels for in vitro cell culture applications. STATEMENT OF SIGNIFICANCE: Traditional dECM hydrogels face challenges in reproducibility and mechanical property control due to variable crosslinking processes. We introduce a click hydrogel based on porcine liver decellularized extracellular matrix (dECM) that circumnavigates these challenges. After optimizing liver decellularization for ECM retention, we integrated thiol-functionalized liver dECM with polyethylene-glycol derivatives through Michael-type addition click chemistry, enabling rapid, room-temperature gelation. This offers enhanced control over the hydrogel's mechanical and biochemical properties. The resultant click dECM hydrogels mimic the liver's natural ECM and exhibit greater mechanical tunability and handling ease, facilitating their application in high-throughput and industrial settings. Moreover, these hydrogels significantly improve the function of HepaRG-derived hepatocytes in 3D culture, presenting an advancement for liver tissue cell culture models for drug testing applications.

The journey of decellularized vessel: from laboratory to operating room

Over the past few decades, there has been a remarkable advancement in the field of transplantation. But the shortage of donors is still an urgent problem that requires immediate attention. As with xenotransplantation, bioengineered organs are promising solutions to the current shortage situation. And decellularization is a unique technology in organ-bioengineering. However, at present, there is no unified decellularization method for different tissues, and there is no gold-standard for evaluating decellularization efficiency. Meanwhile, recellularization, re-endothelialization and modification are needed to form transplantable organs. With this mind, we can start with decellularization and re-endothelialization or modification of small blood vessels, which would serve to address the shortage of small-diameter vessels while simultaneously gathering the requisite data and inspiration for further recellularization of the whole organ-scale vascular network. In this review, we collect the related experiments of decellularization and post-decellularization approaches of small vessels in recent years. Subsequently, we summarize the experience in relation to the decellularization and post-decellularization combinations, and put forward obstacle we face and possible solutions.

Optimizing Decellularization of Bovine Ovarian Tissue: Toward a Transplantable Artificial Ovary Scaffold with Minimized Residual Toxicity and Preserved Extracellular Matrix Morphology

INTRODUCTION

The decellularized extracellular matrix (dECM) from ovarian tissue could be the best scaffold for the development of a transplantable artificial ovary. Typically, dECM from ovarian tissue has been obtained using sodium dodecyl sulfate (SDS), at a concentration of 1% for 24 h. However, SDS can leave residues in the tissue, which may be toxic to the seeded cells. This study aimed to obtain dECM from bovine ovarian tissue using SDS and NaOH at a minimum concentration in the shortest incubation time.

METHODS

The respective SDS and NaOH concentrations investigated were 1% and 0.2 m; 0.5% and 0.1 m; 0.1% and 0.02 m; and 0.05% and 0.01 m, with 24-, 12-, and 6-h incubation periods. After the incubation time, the tissue was washed in 50 mL of distilled water for 6 h.

RESULTS

Histological analysis confirmed decellularization and showed the conservation of collagen fibers in all samples following treatment. Furthermore, the lowest SDS and NaOH concentrations that showed no DNA remaining during electrophoresis analysis were 0.1% and 0.02 m when incubated for 24 and 12 h. DNA quantification resulted in <0.2 ng DNA/mg ovarian tissue using these protocols. Additionally, the coculture of dECM (obtained by 0.1% SDS and 0.02 m NaOH for 12 h) with ovarian cells showed that there was no toxic effect for the cells for up to 72 h.

CONCLUSION

The protocol involving 0.1% SDS and 0.02 m NaOH for 12-h incubation decellularizes bovine ovarian tissue, generating a dECM that preserves the native ECM morphology and is nontoxic to ovarian cells.

Evaluation of Vascular Endothelial Growth Factor Gene Expression in Recellularized Liver Tissue by Mouse Embryo Fibroblast

Background

The aim of the present study was to evaluate alterations in the vegf gene expression as an angiogenic factor in mouse embryo fibroblasts seeded on the decellularized liver fragments.

Methods

Liver tissue samples (n = 10) collected from adult male mice were randomly divided into decellularized and native control groups. Tissues were decellularized by treating with 1% Triton X-100 and 0.1% SDS for 24 hours and assessed by H&E staining and SEM. Then DNA content analysis and toxicity tests were performed. By centrifugation, DiI-labeled mouse embryo fibroblasts were seeded on each scaffold and cultured for one week. The recellularized scaffolds were studied by H&E staining, SEM, and LSCM. After RNA extraction and cDNA synthesis, the expression of the vegf gene in these samples was investigated using real-time RT-PCR.

Results

Our observations showed that the decellularized tissues had morphology and porous structure similar to the control group, and their DNA content significantly reduced (p < 0.05) and reached to 4.12% of the control group. The MTT test indicated no significant cellular toxicity for the decellularized scaffolds. Light microscopy, SEM, and LSCM observations confirmed the attachment and penetration of embryonic fibroblast cells on the surface and into different depths of the scaffolds. There was no statistically significant difference in terms of vegf gene expression in the cultured cells in the presence and absence of a scaffold.

Conclusion

The reconstructed scaffold had no effect on vegf gene expression. Decellularized mouse liver tissue recellularized by embryonic fibroblasts could have an application in regenerative medicine.