Constructing biomimetic liver models through biomaterials and vasculature engineering

Hydrogels in Gene Delivery Techniques for Regenerative Medicine and Tissue Engineering

Hydrogels are 3D networks swollen with water. They are biocompatible, strong, and moldable and are emerging as a promising biomedical material for regenerative medicine and tissue engineering to deliver therapeutic genes. The excellent natural extracellular matrix simulation properties of hydrogels enable them to be co-cultured with cells or enhance the expression of viral or non-viral vectors. Its biocompatibility, high strength, and degradation performance also make the action process of carriers in tissues more ideal, making it an ideal biomedical material. It has been shown that hydrogel-based gene delivery technologies have the potential to play therapy-relevant roles in organs such as bone, cartilage, nerve, skin, reproductive organs, and liver in animal experiments and preclinical trials. This paper reviews recent articles on hydrogels in gene delivery and explains the manufacture, applications, developmental timeline, limitations, and future directions of hydrogel-based gene delivery techniques.

Silymarin enriched gelatin methacrylamide bioink imparts hepatoprotectivity to 3D bioprinted liver construct against carbon tetrachloride induced toxicity

Three-dimensional liver bioprinting is an emerging technology in the field of regenerative medicine that aids in the creation of functional tissue constructs that can be used as transplantable organ substitutes. During transplantation, the bioprinted donor liver must be protected from the oxidative stress environment created by various factors during the transplantation procedure, as well as from drug-induced damage from medications taken as part of the post-surgery medication regimen following the procedure. In this study, Silymarin, a flavonoid with the hepatoprotective properties were introduced into the GelMA bioink formulation to protect the bioprinted liver against hepatotoxicity. The concentration of silymarin to be added in GelMA was optimised, bioink properties were evaluated, and HepG2 cells were used to bioprint liver tissue. Carbon tetrachloride (CCl4) was used to induce hepatotoxicity in bioprinted liver, and the effect of this chemical on the metabolic activities of HepG2 cells was studied. The results showed that Silymarin helps with albumin synthesis and shields liver tissue from the damaging effects of CCl4. According to gene expression analysis, CCl4 treatment increased TNF-α and the antioxidant enzyme SOD expression in HepG2 cells while the presence of silymarin protected the bioprinted construct from CCl4-induced damage. Thus, the outcomes demonstrate that the addition of silymarin in GelMA formulation protects liver function in toxic environments.

Recent Advances in Liver Tissue Engineering as an Alternative and Complementary Approach for Liver Transplantation

Acute and chronic liver diseases cause significant morbidity and mortality worldwide, affecting millions of people. Liver transplantation is the primary intervention method, replacing a non-functional liver with a functional one. However, the field of liver transplantation faces challenges such as donor shortage, postoperative complications, immune rejection, and ethical problems. Consequently, there is an urgent need for alternative therapies that can complement traditional transplantation or serve as an alternative method. In this review, we explore the potential of liver tissue engineering as a supplementary approach to liver transplantation, offering benefits to patients with severe liver dysfunctions.

Experimental Correction and Treatment of Chronic Liver Failure Using Implantable Cell-Engineering Constructs of the Auxiliary Liver Based on a Bioactive Heterogeneous Biopolymer Hydrogel

Our study sought approaches for chronic liver failure (CLF) treatment and correction via cell-engineered constructs (CECs). They are built from biopolymer-based, microstructured, and collagen-containing hydrogel (BMCG). We also strove to evaluate the functional activity of BMCG in liver regeneration.

MATERIALS AND METHODS

Allogeneic liver cells (namely, hepatocytes; LC) together with mesenchymal multipotent stem cells of bone marrow origin (MMSC BM; BMSCs) were adhered to our BMCG to compose implanted liver CECs. Thereafter, we investigated a model of CLF in rats receiving the implanted CECs. The CLF had been provoked by long-term exposure to carbon tetrachloride. The study comprised male Wistar rats (n = 120) randomized into 3 groups: Group 1 was a control group with the saline treatment of the hepatic parenchyma (n = 40); Group 2 received BMCG only (n = 40); and Group 3 was loaded with CECs implanted into the parenchyma of their livers (n = 40). August rats (n = 30) made up a donor population for LCs and MMSC BM to develop grafts for animals from Group 3. The study length was 90 days.

RESULTS

CECs were shown to affect both biochemical test values and morphological parameters in rats with CLF.

CONCLUSION

We found BMCG-derived CECs to be operational and active, with regenerative potential. Group 3 showed significant evidence of forced liver regeneration that tended to persist until the end of the study (day 90). The phenomenon is reflected by biochemical signs of hepatic functional recovery by day 30 after grafting (compared to Groups 1 and 2), whereas structural features of liver repair (necrosis prevention, missing formation of vacuoles, degenerating LC number decrease, and delay of hepatic fibrotic transformation). Such implantation of BMCG-derived CECs with allogeneic LCs and MMSC BM might represent a proper option to correct and treat CLF, as well as to maintain affected liver function in patients with liver grafting needed.

Liver Organoids as an In Vitro Model to Study Primary Liver Cancer

Primary liver cancers (PLC), including hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), are among the leading causes of cancer-related mortality worldwide. Bi-dimensional in vitro models are unable to recapitulate the key features of PLC; consequently, recent advancements in three-dimensional in vitro systems, such as organoids, opened up new avenues for the development of innovative models for studying tumour's pathological mechanisms. Liver organoids show self-assembly and self-renewal capabilities, retaining essential aspects of their respective in vivo tissue and allowing modelling diseases and personalized treatment development. In this review, we will discuss the current advances in the field of liver organoids focusing on existing development protocols and possible applications in regenerative medicine and drug discovery.

Influence of the physico-chemical bioink composition on the printability and cell biological properties in 3D-bioprinting of a liver tumor cell line

The selection of a suitable matrix material is crucial for the development of functional, biomimetic tissue and organ models. When these tissue models are fabricated with 3D-bioprinting technology, the requirements do not only include the biological functionality and physico-chemical properties, but also the printability. In our work, we therefore present a detailed study of seven different bioinks with the focus on a functional liver carcinoma model. Agarose, gelatin, collagen and their blends were selected as materials based on their benefits for 3D cell culture and Drop-on-Demand (DoD) bioprinting. The formulations were characterized for their mechanical (G' of 10-350 Pa) and rheological (viscosity 2-200 Pa*s) properties as well as albumin diffusivity (8-50 μm²/s). The cellular behavior was exemplarily shown for HepG2 cells by monitoring viability, proliferation and morphology over 14 days, while the printability on a microvalve DoD printer was evaluated by drop volume monitoring in flight (100-250 nl), camera imaging of the wetting behavior and microscopy of the effective drop diameter (700 µm and more). We did not observe negative effects on cell viability or proliferation, which is due to the very low shear stresses inside the nozzle (200-500 Pa). With our method, we could identify the strengths and weaknesses of each material, resulting in a material portfolio. By specifically selecting certain materials or blends, cell migration and possible interaction with other cells can be directed as indicated by the results of our cellular experiments.