Reduced liver cell death using an alginate scaffold bandage: a novel approach for liver reconstruction after extended partial hepatectomy

Transcriptome sequencing and metabolome analysis reveal the metabolic reprogramming of partial hepatectomy and extended hepatectomy

Surgical resection remains a critical treatment option for many patients with primary and secondary hepatic neoplasms. Extended hepatectomy (eHx) may be required for some patients with large tumors, which may cause liver failure and death. Partial hepatectomy (pHx) and eHx mouse models were constructed, liver tissues were sampled at 18, 36, and 72 h posthepatectomy. Transcriptome and metabolome analyses were employed to explore the different potential mechanisms in regeneration and injury between pHx and eHx. The results showed that eHx was associated with more severe liver injury and lower survival rates than pHx. Transcriptomics data showed there were 1842, 2129, and 1277 differentially expressed genes (DEGs) in eHx and 962, 1305, and 732 DEGs in pHx at 18, 36, and 72 h posthepatectomy, respectively, compared with the those in the sham groups. Compared with pHx, the number of DEGs in the eHx group reached a maximum of 230 at 18 h after surgery and decreased sequentially to 87 and 43 at 36 and 72 h. Metabolomics analysis identified a total of 1399 metabolites, and 48 significant differentially produced metabolites (DPMs) were screened between eHx and pHx. Combined analysis of DEGs and DPMs indicated that cholesterol metabolism and insulin resistance may be two important pathways for liver regeneration and mouse survival postextended hepatectomy. Our results showed the global influence of pHx and eHx on the transcriptome and metabolome in mouse liver, and revealed cholesterol metabolism and insulin resistance pathways might be involved in regeneration post-pHx and -eHx.

A feasibility study using sodium alginate injection for penetrating abdominal trauma in a swine model

Penetrating abdominal injury is a major cause of death in trauma. Sodium alginate hydrogel, a hemostatic agent, offers a platform for targeting both mechanical and biological injuries. The current study assessed the effect of Very Low Viscosity (high) G (VLVG) alginate following abdominal trauma in a swine model of penetrating abdominal injury. Seven anesthetized pigs were instrumented with invasive monitoring catheters and abdominal trauma was introduced by laparoscopic hepatectomy. Ten minutes after the induction of hypovolemic shock, three animals were intra-abdominally administered with VLVG alginate (study group) and four animals with saline (control group). During 8 h of continuous monitoring, various hemodynamic and biochemical variables were measured and liver biopsies for histological evaluation were taken. Hemodynamically, VLVG alginate-treated animals were more stable than controls, as reflected by their lower heart rate and higher blood pressure (p < 0.05 for both). They also had lower levels of liver enzymes and lactate, and less histopathological damage. We show that VLVG alginate might be a promising new agent for reducing penetrating intra-abdominal injury, with hemostatic and biocompatibility efficiency, and tissue preserving properties. Future effort of integrating it with a dispersal device may turn it into a valuable pre-hospital emergency tool to improve survival of trauma casualties.

Hyaluronic Acid-Based Scaffolds as Potential Bioactive Wound Dressings

The negative factors that result in delayed and prolonged wound healing process include microbial pathogens, excess wound exudates, underlying conditions, smoking, obesity, etc. Most of the currently used wound dressings demonstrate an inadequate capacity to treat wounds resulting from the factors mentioned above. The commonly used wound dressings include hydrogels, films, hydrocolloids, foams, fibers, sponges, dermal patches, bandages, etc. These wound dressings can be loaded with various types of bioactive agents (e.g., antibiotics, nanoparticles, anti-inflammatory drugs, etc.) to improve their therapeutic outcomes. Biopolymers offer interesting properties suitable for the design of wound dressings. This review article will be based on hyaluronic-acid-based scaffolds loaded with therapeutic agents for the treatment of wounds.

SARS-CoV-2 and tissue damage: current insights and biomaterial-based therapeutic strategies

The effect of SARS-CoV-2 infection on humanity has gained worldwide attention and importance due to the rapid transmission, lack of treatment options and high mortality rate of the virus. While scientists across the world are searching for vaccines/drugs that can control the spread of the virus and/or reduce the risks associated with infection, patients infected with SARS-CoV-2 have been reported to have tissue/organ damage. With most tissues/organs having limited regenerative potential, interventions that prevent further damage or facilitate healing would be helpful. In the past few decades, biomaterials have gained prominence in the field of tissue engineering, in view of their major role in the regenerative process. Here we describe the effect of SARS-CoV-2 on multiple tissues/organs, and provide evidence for the positive role of biomaterials in aiding tissue repair. These findings are further extrapolated to explore their prospects as a therapeutic platform to address the tissue/organ damage that is frequently observed during this viral outbreak. This study suggests that the biomaterial-based approach could be an effective strategy for regenerating tissues/organs damaged by SARS-CoV-2.

Chitosan and Cellulose-Based Hydrogels for Wound Management

Wound management remains a challenge worldwide, although there are several developed wound dressing materials for the management of acute and chronic wounds. The wound dressings that are currently used include hydrogels, films, wafers, nanofibers, foams, topical formulations, transdermal patches, sponges, and bandages. Hydrogels exhibit unique features which make them suitable wound dressings such as providing a moist environment for wound healing, exhibiting high moisture content, or creating a barrier against bacterial infections, and are suitable for the management of exuding and granulating wounds. Biopolymers have been utilized for their development due to their non-toxic, biodegradable, and biocompatible properties. Hydrogels have been prepared from biopolymers such as cellulose and chitosan by crosslinking with selected synthetic polymers resulting in improved mechanical, biological, and physicochemical properties. They were useful by accelerating wound re-epithelialization and also mimic skin structure, inducing skin regeneration. Loading antibacterial agents into them prevented bacterial invasion of wounds. This review article is focused on hydrogels formulated from two biopolymers-chitosan and cellulose-for improved wound management.

Development of 3D Hepatic Constructs Within Polysaccharide-Based Scaffolds with Tunable Properties

Organoids production is a key tool for in vitro studies of physiopathological conditions, drug-induced toxicity assays, and for a potential use in regenerative medicine. Hence, it prompted studies on hepatic organoids and liver regeneration. Numerous attempts to produce hepatic constructs had often limited success due to a lack of viability or functionality. Moreover, most products could not be translated for clinical studies. The aim of this study was to develop functional and viable hepatic constructs using a 3D porous scaffold with an adjustable structure, devoid of any animal component, that could also be used as an in vivo implantable system. We used a combination of pharmaceutical grade pullulan and dextran with different porogen formulations to form crosslinked scaffolds with macroporosity ranging from 30 µm to several hundreds of microns. Polysaccharide scaffolds were easy to prepare and to handle, and allowed confocal observations thanks to their transparency. A simple seeding method allowed a rapid impregnation of the scaffolds with HepG2 cells and a homogeneous cell distribution within the scaffolds. Cells were viable over seven days and form spheroids of various geometries and sizes. Cells in 3D express hepatic markers albumin, HNF4α and CYP3A4, start to polarize and were sensitive to acetaminophen in a concentration-dependant manner. Therefore, this study depicts a proof of concept for organoid production in 3D scaffolds that could be prepared under GMP conditions for reliable drug-induced toxicity studies and for liver tissue engineering.

Regulated differentiation of stem cells into an artificial 3D liver as a transplantable source

End-stage liver disease is one of the leading causes of death around the world. Since insufficient sources of transplantable liver and possible immune rejection severely hinder the wide application of conventional liver transplantation therapy, artificial three-dimensional (3D) liver culture and assembly from stem cells have become a new hope for patients with end-stage liver diseases, such as cirrhosis and liver cancer. However, the induced differentiation of single-layer or 3D-structured hepatocytes from stem cells cannot physiologically support essential liver functions due to the lack of formation of blood vessels, immune regulation, storage of vitamins, and other vital hepatic activities. Thus, there is emerging evidence showing that 3D organogenesis of artificial vascularized liver tissue from combined hepatic cell types derived from differentiated stem cells is practical for the treatment of end-stage liver diseases. The optimization of novel biomaterials, such as decellularized matrices and natural macromolecules, also strongly supports the organogenesis of 3D tissue with the desired complex structure. This review summarizes new research updates on novel differentiation protocols of stem cell-derived major hepatic cell types and the application of new supportive biomaterials. Future biological and clinical challenges of this concept are also discussed.

Liver Tissue Engineering: Challenges and Opportunities

Liver tissue engineering aims at the possibility of reproducing a fully functional organ for the treatment of acute and chronic liver disorders. Approaches in this field endeavor to replace organ transplantation (gold standard treatment for liver diseases in a clinical setting) with in vitro developed liver tissue constructs. However, the complexity of the liver microarchitecture and functionality along with the limited supply of cellular components of the liver pose numerous challenges. This review provides a comprehensive outlook onto how the physicochemical, mechanobiological, and spatiotemporal aspects of the substrates could be tuned to address current challenges in the field. We also highlight the strategic advancements made in the field so far for the development of artificial liver tissue. We further showcase the currently available prototypes in research and clinical trials, which shows the hope for the future of liver tissue engineering.

Polysaccharide Based Scaffolds for Soft Tissue Engineering Applications

Soft tissue reconstructs require materials that form three-dimensional (3-D) structures supportive to cell proliferation and regenerative processes. Polysaccharides, due to their hydrophilicity, biocompatibility, biodegradability, abundance, and presence of derivatizable functional groups, are distinctive scaffold materials. Superior mechanical properties, physiological signaling, and tunable tissue response have been achieved through chemical modification of polysaccharides. Moreover, an appropriate formulation strategy enables spatial placement of the scaffold to a targeted site. With the advent of newer technologies, these preparations can be tailor-made for responding to alterations in temperature, pH, or other physiological stimuli. In this review, we discuss the developmental and biological aspects of scaffolds prepared from four polysaccharides, viz. alginic acid (ALG), chitosan (CHI), hyaluronic acid (HA), and dextran (DEX). Clinical studies on these scaffolds are also discussed.

Mesenchymal stem cells seeded on a human amniotic membrane improve liver regeneration and mouse survival after extended hepatectomy

Liver failure remains the leading cause of post-operative mortality after hepatectomy. This study investigated the effect of treatment with allogenic mesenchymal stem cells (MSCs) on survival and liver regeneration 48 hr and 7 days after 80% hepatectomy in C57Bl/6 mice. To optimize their biodistribution, MSCs were grown on acellular human amniotic membranes (HAM) and applied as a patch on the remnant liver. This approach was compared with MSC infusion and HAM patch alone. Hepatectomized mice without any treatment were used as control group. Survival rate was calculated and biological and histopathological parameters were analysed to monitor liver function and regeneration. MSCs grown on HAM retained their ability to proliferate, to differentiate into osteoblasts and adipocytes and to respond to pro-inflammatory stimuli. Extended hepatectomy (80%) led to liver failure that resulted in death within 72 hr in 76% of mice. MSC infusion showed an early but transitory positive effect on survival. MSC/HAM patches stimulated regeneration and significantly improved survival rate (54% vs. 24% in the control group at 7 days). They also decreased the severity of hepatectomy-induced steatosis, suggesting a modulation of lipid metabolism in hepatocytes. MSCs were still present on HAM at Days 2 and 7 posthepatectomy. In conclusion, engineered tissue constructs that combine MSCs and HAM improve survival and liver regeneration after 80% hepatectomy in mice. These encouraging results pave the way to potential clinical application.

Alginate-embedded HuH-7 cells increase MMP-9 and reduce OCLN expression in vitro

BACKGROUND

Hepatocellular carcinoma is a common cancer, ranking third in cancer-associated deaths. An important cause of cancer patients' mortality is metastasis. At the start of metastasis progression, there is an epithelial-mesenchymal transition, characterized by matrix degradation, junction reductions and vessels formation. HuH-7 is a cell line used in research as an in vitro model for hepatocellular carcinoma. It is known that two-dimensional growth reflects tumor characteristics poorly. In contrast, three-dimensional cultures provide a better approach to the study of tumorigenic potential. The purpose of this work was to mimic a three-dimensional environment in order to assess gene expression of some epithelial-mesenchymal transition and metastasis progression markers in HuH-7 cells and compare them with traditional two-dimensional culture model.

METHODS

HuH-7 cells were encapsulated in sodium alginate (three-dimensional model) to be compared with cells grown in two-dimensional flasks. After 4 days in culture, gene expression of Matrix metallopeptidase 9, Occludin, p65, Intercellular adhesion molecule 1 and Vascular endothelial growth factor A was analyzed by qPCR and cytoskeleton assessment was performed by rhodamine-phalloidin staining.

RESULTS

Differences were found in gene expression, with a high increment of Matrix metallopeptidase 9 and Occludin reduction. The cytoskeleton morphology also showed differences, with a cytoplasm restricted only near the nuclei in the three-dimensional model.

CONCLUSIONS

This work shows the effects of using sodium alginate capsules as a three-dimensional model to the study of HuH-7. Cells in this 3D system show key markers of epithelial-mesenchymal transition, such as Matrix metallopeptidase 9 overexpression and Occludin down-regulation.

Transplantation of bovine adrenocortical cells encapsulated in alginate

Current treatment options for adrenal insufficiency are limited to corticosteroid replacement therapies. However, hormone therapy does not replicate circadian rhythms and has unpleasant side effects especially due to the failure to restore normal function of the hypothalamic-pituitary-adrenal (HPA) axis. Adrenal cell transplantation and the restoration of HPA axis function would be a feasible and useful therapeutic strategy for patients with adrenal insufficiency. We created a bioartificial adrenal with 3D cell culture conditions by encapsulation of bovine adrenocortical cells (BACs) in alginate (enBACs). We found that, compared with BACs in monolayer culture, encapsulation in alginate significantly increased the life span of BACs. Encapsulation also improved significantly both the capacity of adrenal cells for stable, long-term basal hormone release as well as the response to pituitary adrenocorticotropic hormone (ACTH) and hypothalamic luteinizing hormone-releasing hormone (LHRH) agonist, [D-Trp6]LHRH. The enBACs were transplanted into adrenalectomized, immunodeficient, and immunocompetent rats. Animals received enBACs intraperitoneally, under the kidney capsule (free cells or cells encapsulated in alginate slabs) or s.c. enclosed in oxygenating and immunoisolating βAir devices. Graft function was confirmed by the presence of cortisol in the plasma of rats. Both types of grafted encapsulated cells, explanted after 21-25 d, preserved their morphology and functional response to ACTH stimulation. In conclusion, transplantation of a bioartificial adrenal with xenogeneic cells may be a treatment option for patients with adrenocortical insufficiency and other stress-related disorders. Furthermore, this model provides a microenvironment that ensures 3D cell-cell interactions as a unique tool to investigate new insights into cell biology, differentiation, tissue organization, and homeostasis.