Decellularization Techniques for Tissue Engineering: Towards Replicating Native Extracellular Matrix Architecture in Liver Regeneration

Injectable cell-laden gelatin-chondroitin sulphate hydrogels for liver in vitro models

Liver extracellular matrix-based models that precisely reproduce liver physiology and functions are required as 3D culture microenvironments for multiple applications in toxicology and metabolism, or for understanding the mechanisms implicated in liver disease. We introduced injectable gelatin-chondroitin sulphate (Gel/CS) hydrogels for culturing HepG2 cells, and evaluated the mechanical properties and functionality of cells in different Gel/CS compositions. The Gel/CS hydrogels exhibited soft mechanical properties and allowed the HepG2 culture. The characterisation and comparison of 3D cultures to standard monolayer systems revealed the regulation of key hepatic markers (i.e. CYP3A4, GSTA1) when cells were cultured in the Gel/CS hydrogels compared to 2D cultures, and also enhanced urea and albumin production, which would indicate increased cells functionality. This study underpins 3D in vitro models based on the Gel/CS hydrogels that can be used for different hepatology applications by offering increased predictivity and physiological relevance compared to current in vitro models.

Towards Safety and Regulation Criteria for Clinical Applications of Decellularized Organ-Derived Matrices

Whole-organ decellularization generates scaffolds containing native extracellular matrix (ECM) components with preserved tissue microarchitecture, providing a promising advancement in tissue engineering and regenerative medicine. Decellularization retains the ECM integrity which is important for supporting cell attachment, growth, differentiation, and biological function. Although there are consensus guidelines to standardize decellularization processes and ECM characterization, no specific criteria or standards regarding matrix sterility and biosafety have been established so far. This regulatory gap in safety, sterilization, and regulation criteria has hampered the clinical translation of decellularized scaffolds. In this review, we identify essential criteria for the safe clinical use of decellularized products from both human and animal sources. These include the decellularization efficacy, levels of chemical residue, preservation of ECM composition and physical characteristics, and criteria for the aseptic processing of decellularization to assure sterility. Furthermore, we explore key considerations for advancing decellularized scaffolds into clinical practice, focusing on regulatory frameworks and safety requirements. Addressing these challenges is crucial for minimizing risks of adverse reactions or infection transmission, thereby accelerating the adoption of tissue-engineered products. This review aims to provide a foundation for establishing robust guidelines, supporting the safe and effective integration of decellularized scaffolds into regenerative medicine applications.

Development of Controllable Perfusion Culture Scaffolds Using Multi-Channel Collagen Gels: Effects of Gelation Conditions on Channel Formation and Media Supply

The development of scaffold materials that effectively mimic the extracellular matrix while enabling controlled nutrient delivery remains a critical challenge in tissue engineering. Multi-channel collagen gels (MCCGs), which form through the competition between gelation and phase separation, have emerged as promising scaffolds due to their self-organized vessel-like structures. However, a systematic understanding of the relationship between the gelation conditions and functional properties is limited. In this study, MCCGs were developed as controllable perfusion culture scaffolds by investigating the effects of carbonate buffer concentration on channel formation, permeation behavior, and cell proliferation. MCCGs were prepared using different carbonate buffer concentrations (12.5, 25, and 50 mM), with 25 mM producing optimal channel formation, characterized by an approximately 60% channel area fraction and uniform distribution. Permeation studies revealed that fluid transport through MCCGs is governed by a complex interplay between capillary phenomena and hydraulic pressure, whose relative dominance shifts with flow rate: capillary action dominates at low flow rates (2.5 mL/h), whereas hydraulic pressure becomes the primary driver at higher rates (5.0-10.0 mL/h). Cell proliferation assessments demonstrated that MCCGs prepared with 25 mM carbonate buffer provided the most favorable microenvironment, achieving superior cell growth over 168 h through balanced media supply and cell adhesion area. This optimization approach through buffer concentration adjustment offers a cost-effective and scalable method for developing perfusion culture scaffolds, advancing both the fundamental understanding of functional gel systems and practical applications in tissue engineering and regenerative medicine.

Three-Dimensional Printing/Bioprinting and Cellular Therapies for Regenerative Medicine: Current Advances

The application of three-dimensional (3D) printing/bioprinting technologies and cell therapies has garnered significant attention due to their potential in the field of regenerative medicine. This paper aims to provide a comprehensive overview of 3D printing/bioprinting technology and cell therapies, highlighting their results in diverse medical applications, while also discussing the capabilities and limitations of their combined use. The synergistic combination of 3D printing and cellular therapies has been recognised as a promising and innovative approach, and it is expected that these technologies will progressively assume a crucial role in the treatment of various diseases and conditions in the foreseeable future. This review concludes with a forward-looking perspective on the future impact of these technologies, highlighting their potential to revolutionize regenerative medicine through enhanced tissue repair and organ replacement strategies.

Hydrogel-Based Strategies for Liver Tissue Engineering

The liver's role in metabolism, detoxification, and immune regulation underscores the urgency of addressing liver diseases, which claim millions of lives annually. Due to donor shortages in liver transplantation, liver tissue engineering (LTE) offers a promising alternative. Hydrogels, with their biocompatibility and ability to mimic the liver's extracellular matrix (ECM), support cell survival and function in LTE. This review analyzes recent advances in hydrogel-based strategies for LTE, including decellularized liver tissue hydrogels, natural polymer-based hydrogels, and synthetic polymer-based hydrogels. These materials are ideal for in vitro cell culture and obtaining functional hepatocytes. Hydrogels' tunable properties facilitate creating artificial liver models, such as organoids, 3D bioprinting, and liver-on-a-chip technologies. These developments demonstrate hydrogels' versatility in advancing LTE's applications, including hepatotoxicity testing, liver tissue regeneration, and treating acute liver failure. This review highlights the transformative potential of hydrogels in LTE and their implications for future research and clinical practice.

Comparative analysis of porcine-uterine decellularization for bioactive-molecule preservation and DNA removal

Introduction

Decellularized uterine extracellular matrix has emerged as a pivotal focus in the realm of biomaterials, offering a promising source in uterine tissue regeneration, research on disease diagnosis and treatments, and ultimately uterine transplantation. In this study, we examined various protocols for decellularizing porcine uterine tissues, aimed to unravel the intricate dynamics of DNA removal, bioactive molecules preservation, and microstructural alterations.

Methods

Porcine uterine tissues were treated with 6 different, yet rigorously selected and designed, protocols with sodium dodecyl sulfate (SDS), Triton® X-100, peracetic acid + ethanol, and DNase I. After decellularization, we examined DNA quantification, histological staining (H&E and DAPI), glycosaminoglycans (GAG) assay, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and Thermogravimetric Analysis (TGA).

Results

A comparative analysis among all 6 protocols was conducted with the results demonstrating that all protocols achieved decellularization; while 0.1% SDS + 1% Triton® X-100, coupled with agitation, demonstrated the highest efficiency in DNA removal. Also, it was found that DNase I played a key role in enhancing the efficiency of the decellularization process by underscoring its significance in digesting cellular contents and eliminating cell debris by 99.79% (19.63 ± 3.92 ng/mg dry weight).

Conclusions

Our findings enhance the nuanced understanding of DNA removal, GAG preservation, microstructural alteration, and protein decomposition in decellularized uterine extracellular matrix, while highlighting the importance of decellularization protocols designed for intended applications. This study along with our findings represents meaningful progress for advancing the field of uterine transplantation and related tissue engineering/regenerative medicine.

Moonlighting on the Fasciola hepatica tegument: Enolase, a glycolytic enzyme, interacts with the extracellular matrix and fibrinolytic system of the host

Enolase is a 47 kDa enzyme that functions within the glycolysis and gluconeogenesis pathways involved in the reversible conversion of D-2-phosphoglycerate (2PGA) to phosphoenolpyruvate (PEP). However, in the context of host-pathogen interactions, enolase from different species of parasites, fungi and bacteria have been shown to contribute to adhesion processes by binding to proteins of the host extracellular matrix (ECM), such as fibronectin (FN) or laminin (LM). In addition, enolase is a plasminogen (PLG)-binding protein and induces its activation to plasmin, the main protease of the host fibrinolytic system. These secondary 'moonlighting' functions of enolase are suggested to facilitate pathogen migration through host tissues. This study aims to uncover the moonlighting role of enolase from the parasite Fasciola hepatica, shedding light on its relevance to host-parasite interactions in fasciolosis, a global zoonotic disease of increasing concern. A purified recombinant form of F. hepatica enolase (rFhENO), functioning as an active homodimeric glycolytic enzyme of ~94 kDa, was successfully obtained, fulfilling its canonical role. Immunoblotting studies on adult worm extracts showed that the enzyme is present in the tegument and the excretory/secretory products of the parasite, which supports its key role at the host-parasite interface. Confocal immunolocalisation studies of the protein in newly excysted juveniles and adult worms also localised its expression within the parasite tegument. Finally, we showed by ELISA that rFhENO can act as a parasitic adhesin by binding host LM, but not FN. rFhENO also binds PLG and enhances its conversion to plasmin in the presence of the tissue-type and urokinase-type PLG activators (t-PA and u-PA). This moonlighting adhesion-like function of the glycolytic protein enolase could contribute to the mechanisms by which F. hepatica efficiently invades and migrates within its host and encourages further research efforts that are designed to impede this function by vaccination or drug design.

Engineering cell-derived extracellular matrix for peripheral nerve regeneration

Extracellular matrices (ECMs) play a key role in nerve repair and are recognized as the natural source of biomaterials. In parallel to extensively studied tissue-derived ECMs (ts-ECMs), cell-derived ECMs (cd-ECMs) also have the capability to partially recapitulate the complicated regenerative microenvironment of native nerve tissues. Notably, cd-ECMs can avoid the shortcomings of ts-ECMs. Cd-ECMs can be prepared by culturing various cells or even autologous cells in vitro under pathogen-free conditions. And mild decellularization can achieve efficient removal of immunogenic components in cd-ECMs. Moreover, cd-ECMs are more readily customizable to achieve the desired functional properties. These advantages have garnered significant attention for the potential of cd-ECMs in neuroregenerative medicine. As promising biomaterials, cd-ECMs bring new hope for the effective treatment of peripheral nerve injuries. Herein, this review comprehensively examines current knowledge about the functional characteristics of cd-ECMs and their mechanisms of interaction with cells in nerve regeneration, with a particular focus on the preparation, engineering optimization, and scalability of cd-ECMs. The applications of cd-ECMs from distinct cell sources reported in peripheral nerve tissue engineering are highlighted and summarized. Furthermore, current limitations that should be addressed and outlooks related to clinical translation are put forward as well.

Microscale tissue engineering of liver lobule models: advancements and applications

The liver, as the body's primary organ for maintaining internal balance, is composed of numerous hexagonal liver lobules, each sharing a uniform architectural framework. These liver lobules serve as the basic structural and functional units of the liver, comprised of central veins, hepatic plates, hepatic sinusoids, and minute bile ducts. Meanwhile, within liver lobules, distinct regions of hepatocytes carry out diverse functions. The in vitro construction of liver lobule models, faithfully replicating their structure and function, holds paramount significance for research in liver development and diseases. Presently, two primary technologies for constructing liver lobule models dominate the field: 3D bioprinting and microfluidic techniques. 3D bioprinting enables precise deposition of cells and biomaterials, while microfluidics facilitates targeted transport of cells or other culture materials to specified locations, effectively managing culture media input and output through micro-pump control, enabling dynamic simulations of liver lobules. In this comprehensive review, we provide an overview of the biomaterials, cells, and manufacturing methods employed by recent researchers in constructing liver lobule models. Our aim is to explore strategies and technologies that closely emulate the authentic structure and function of liver lobules, offering invaluable insights for research into liver diseases, drug screening, drug toxicity assessment, and cell replacement therapy.