Cellular Mechanisms of Liver Regeneration and Cell-Based Therapies of Liver Diseases. Biomed Res Int. 2017;2017:8910821. [PMID: 28210629 PMCID: PMC5292184 DOI: 10.1155/2017/8910821]

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.

Building in vitro models for mechanistic understanding of liver regeneration in chronic liver diseases

The liver has excellent regeneration potential and attains complete functional recovery from partial hepatectomy. The regenerative mechanisms malfunction in chronic liver diseases (CLDs), which fuels disease progression. CLDs account for 2 million deaths per year worldwide. Pathophysiological studies with clinical correlation have shown evidence of deviation of normal regenerative mechanisms and its contribution to fueling fibrosis and disease progression. However, we lack realistic in vitro models that can allow experimental manipulation for mechanistic understanding of liver regeneration in CLDs and testing of candidate drugs. In this review, we aim to provide the framework for building appropriate organotypic models for dissecting regenerative responses in CLDs, with the focus on non-alcoholic steatohepatitis (NASH). By drawing parallels with development and hepatectomy, we explain the selection of critical components such as cells, signaling, and, substrate-driven biophysical cues to build an appropriate CLD model. We highlight the organoid-based organotypic models available for NASH disease modeling, including organ-on-a-chip and 3D bioprinted models. With the focus on bioprinting as a fabrication method, we prescribe building in vitro CLD models and testing schemes for exploring the regenerative responses in the bioprinted model.

Hepatitis B Virus Infection: A Mini Review

Hepatitis B and C viruses (HBV and HCV) are the leading causes of end-stage liver disease worldwide. Although there is a potent vaccine against HBV, many new infections are recorded annually, especially in poorly resourced places which have lax vaccination policies. Again, as HBV has no cure and chronic infection is lifelong, vaccines cannot help those already infected. Studies to thoroughly understand the HBV biology and pathogenesis are limited, leaving much yet to be understood about the genomic features and their role in establishing and maintaining infection. The current knowledge of the impact on disease progression and response to treatment, especially in hyperendemic regions, is inadequate. This calls for in-depth studies on viral biology, mainly for the purposes of coming up with better management strategies for infected people and more effective preventative measures for others. This information could also point us in the direction of a cure. Here, we discuss the progress made in understanding the genomic basis of viral activities leading to the complex interplay of the virus and the host, which determines the outcome of HBV infection as well as the impact of coinfections.

Optimizing a five-factor cocktail to prepare reparative macrophages for wound healing

The treatment of non-healing wounds, such as diabetic ulcers, remains a critical clinical challenge. Recent breakthroughs in cell therapy have shown great promise, with one primary focus on preparing cells with comprehensive reparative functions and foreseeable safety. In our previous study, we recapitulated the pro-regenerative and immunosuppressive functions of tumor-associated macrophages (TAMs) in non-tumor-derived macrophages, endowing the latter with characteristics for promoting diabetic wound healing - termed TAMs-educated macrophages (TAMEMs). To eliminate the use of tumor-derived sources and devise a more controllable method to prepare TAMEM-like cells, in this study, we identify a cocktail comprising five recombinant proteins as an essential condition to induce non-polarized macrophages (termed TAMEMs5) into therapeutic cells with pro-healing functions. The screened five factors are osteopontin (OPN), macrophage inflammatory protein (MIP)-2, chemokine (C-C motif) ligand 8 (CCL8), vascular endothelial growth factor (VEGF)-B, and macrophage colony-stimulating factor (M-CSF). We demonstrate the rationale for screening these factors and the phenotype of TAMEMs5 prepared from murine bone marrow-derived macrophages, which exhibit angiogenic and immunomodulatory effects in vitro. Then, we induce primary human monocytes from periphery blood into TAMEMs5, which show pro-healing effects in a human primary cell-based ex vivo model (T-SkinTM). Our study demonstrates a simple, effective, and controllable approach to induce primary macrophages to possess repairing activities, which may provide insights for developing cell-based therapeutics for non-healing wounds clinically.

A review on the application of chitosan-based polymers in liver tissue engineering

Chitosan-based polymers have enormous structural tendencies to build bioactive materials with novel characteristics, functions, and various applications, mainly in liver tissue engineering (LTE). The specific physicochemical, biological, mechanical, and biodegradation properties give the effective ways to blend these biopolymers with synthetic and natural polymers to fabricate scaffolds matrixes, sponges, and complexes. A variety of natural and synthetic biomaterials, including chitosan (CS), alginate (Alg), collagen (CN), gelatin (GL), hyaluronic acid (HA), hydroxyapatite (HAp), polyethylene glycol (PEG), polycaprolactone (PCL), poly(lactic-co-glycolic) acid (PGLA), polylactic acid (PLA), and silk fibroin gained considerable attention due to their structure-properties relationship. The incorporation of CS within the polymer matrix results in increased mechanical strength and also imparts biological behavior to the designed PU formulations. The significant and growing interest in the LTE sector, this review aims to be a detailed exploration of CS-based polymers biomaterials for LTE. A brief explanation of the sources and extraction, properties, structure, and scope of CS is described in the introduction. After that, a full overview of the liver, its anatomy, issues, hepatocyte transplantation, LTE, and CS LTE applications are discussed.

Prostaglandin F2α Affects the Cycle of Clock Gene Expression and Mouse Behavior

Prostaglandins are bioactive compounds, and the activation of their receptors affects the expression of clock genes. However, the prostaglandin F receptor (Ptgfr) has no known relationship with biological rhythms. Here, we first measured the locomotor period lengths of Ptgfr-KO (B6.129-Ptgfrtm1Sna) mice and found that they were longer under constant dark conditions (DD) than those of wild-type (C57BL/6J) mice. We then investigated the clock gene patterns within the suprachiasmatic nucleus in Ptgfr-KO mice under DD and observed a decrease in the expression of the clock gene cryptochrome 1 (Cry1), which is related to the circadian cycle. Moreover, the expression of Cry1, Cry2, and Period2 (Per2) mRNA were significantly altered in the mouse liver in Ptgfr-KO mice under DD. In the wild-type mouse, the plasma prostaglandin F2α (PGF2α) levels showed a circadian rhythm under a 12 h cycle of light-dark conditions. In addition, in vitro experiments showed that the addition of PTGFR agonists altered the amplitude of Per2::luc activity, and this alteration differed with the timing of the agonist addition. These results lead us to hypothesize that the plasma rhythm of PGF2α is important for driving clock genes, thus suggesting the involvement of PGF2α- and Ptgfr-targeting drugs in the biological clock cycle.

Old age as a risk factor for liver diseases: Modern therapeutic approaches

Recent scientific interest has been directed towards age-related diseases, driven by the significant increase in global life expectancy and the growing population of individuals aged 65 and above. The ageing process encompasses various biological, physiological, environmental, psychological, behavioural, and social changes, leading to an augmented susceptibility to chronic illnesses. Cardiovascular, neurological, musculoskeletal, liver and oncological diseases are prevalent in the elderly. Moreover, ageing individuals demonstrate reduced regenerative capacity and decreased tolerance towards therapeutic interventions, including organ transplantation. Liver diseases, such as non-alcoholic fatty liver disease, alcoholic liver disease, hepatitis, fibrosis, and cirrhosis, have emerged as significant public health concerns. Paradoxically, these conditions remain underestimated despite their substantial global impact. Age-related factors are closely associated with the severity and unfavorable prognosis of various liver diseases, warranting further investigation to enhance clinical management and develop novel therapeutic strategies. This comprehensive review focuses specifically on age-related liver diseases, their treatment strategies, and contemporary practices. It provides a detailed account of the global burden, types, molecular mechanisms, and epigenetic alterations underlying these liver pathologies.

Relationship between oxygen partial pressure and inhibition of cell aggregation of human adipose tissue-derived mesenchymal stem cells stored in cell preservation solutions

Introduction

This study investigated the storage conditions under which cell aggregation occurs and the conditions that inhibit cell aggregation when human adipose tissue-derived mesenchymal stem cells (hADSCs) are stored in lactated Ringer's solution (LR) supplemented with 3% trehalose and 5% dextran 40 (LR-3T-5D).

Methods

We first examined the effects of storage temperature and time on the aggregation and viability of hADSCs stored in LR and LR-3T-5D. The cells were stored at 5 °C or 25 °C for various times up to 24 h. We then evaluated the effects of storage volume (250-2,000 μL), cell density (2.5-20 × 10⁵ cells/mL), and nitrogen gas replacement on aggregation, oxygen partial pressure (pO₂), and viability of hADSCs stored for 24 h at 25 °C in LR-3T-5D.

Results

When stored in LR-3T-5D, viability did not change under either condition compared with pre-storage, but the cell aggregation rate increased significantly with storage at 25 °C for 24 h (p<0.001). In LR, the aggregation rate did not change under either condition, but cell viability decreased significantly after 24 h at both 5 °C and 25 °C (p < 0.05). The cell aggregation rates and pO₂ tended to decrease with increasing solution volume and cell density. Nitrogen gas replacement significantly decreased the cell aggregation rate and pO₂ (p < 0.05). However, there were no differences in viability among cells stored under conditions of different storage volumes, densities, and nitrogen gas replacement.

Conclusions

Aggregation of cells after storage at 25 °C in LR-3T-5D may be suppressed by increasing the storage volume and cell density as well as by incorporating nitrogen replacement, which lowers the pO₂ in the solution.

Age-Related Features of the Early Period of Liver Regeneration after Partial Hepatectomy in Rats

Regenerative processes in the liver were studied in 3-month-old (young) and 9-month-old (aged) male Wistar rats on day 1 after 30 and 70% hepatectomy. Regardless of the resected liver volume, shifts in the biochemical parameters of the serum in aged rats were more pronounced than in young animals. After 30% hepatectomy, no age differences in the rate of hepatic regeneration were found, while after 70% liver resection this parameter was higher in young rats. Hepatectomy in young rats led to recruitment of MSC, hepatocyte precursors, endothelial and epithelial progenitor cells into the liver parenchyma and increased fluidity of the plasma and mitochondrial membranes of hepatocytes. In aged rats, the recruitment of MSC, hepatocyte precursors, and endothelial progenitor cells into the injured liver was impaired and the rigidity of the mitochondrial membranes of hepatocytes increased.

Progress in bioprinting technology for tissue regeneration

In recent years, due to the increase in diseases that require organ/tissue transplantation and the limited donor, on the other hand, patients have lost hope of recovery and organ transplantation. Regenerative medicine is one of the new sciences that promises a bright future for these patients by providing solutions to repair, improve function, and replace tissue. One of the technologies used in regenerative medicine is three-dimensional (3D) bioprinters. Bioprinting is a new strategy that is the basis for starting a global revolution in the field of medical sciences and has attracted much attention. 3D bioprinters use a combination of advanced biology and cell science, computer science, and materials science to create complex bio-hybrid structures for various applications. The capacity to use this technology can be demonstrated in regenerative medicine to make various connective tissues, such as skin, cartilage, and bone. One of the essential parts of a 3D bioprinter is the bio-ink. Bio-ink is a combination of biologically active molecules, cells, and biomaterials that make the printed product. In this review, we examine the main bioprinting strategies, such as inkjet printing, laser, and extrusion-based bioprinting, as well as some of their applications.

The Crosstalk between Mesenchymal Stromal/Stem Cells and Hepatocytes in Homeostasis and under Stress

Liver diseases, characterized by high morbidity and mortality, represent a substantial medical problem globally. The current therapeutic approaches are mainly aimed at reducing symptoms and slowing down the progression of the diseases. Organ transplantation remains the only effective treatment method in cases of severe liver pathology. In this regard, the development of new effective approaches aimed at stimulating liver regeneration, both by activation of the organ's own resources or by different therapeutic agents that trigger regeneration, does not cease to be relevant. To date, many systematic reviews and meta-analyses have been published confirming the effectiveness of mesenchymal stromal cell (MSC) transplantation in the treatment of liver diseases of various severities and etiologies. However, despite the successful use of MSCs in clinical practice and the promising therapeutic results in animal models of liver diseases, the mechanisms of their protective and regenerative action remain poorly understood. Specifically, data about the molecular agents produced by these cells and mediating their therapeutic action are fragmentary and often contradictory. Since MSCs or MSC-like cells are found in all tissues and organs, it is likely that many key intercellular interactions within the tissue niches are dependent on MSCs. In this context, it is essential to understand the mechanisms underlying communication between MSCs and differentiated parenchymal cells of each particular tissue. This is important both from the perspective of basic science and for the development of therapeutic approaches involving the modulation of the activity of resident MSCs. With regard to the liver, the research is concentrated on the intercommunication between MSCs and hepatocytes under normal conditions and during the development of the pathological process. The goals of this review were to identify the key factors mediating the crosstalk between MSCs and hepatocytes and determine the possible mechanisms of interaction of the two cell types under normal and stressful conditions. The analysis of the hepatocyte-MSC interaction showed that MSCs carry out chaperone-like functions, including the synthesis of the supportive extracellular matrix proteins; prevention of apoptosis, pyroptosis, and ferroptosis; support of regeneration; elimination of lipotoxicity and ER stress; promotion of antioxidant effects; and donation of mitochondria. The underlying mechanisms suggest very close interdependence, including even direct cytoplasm and organelle exchange.

Placental scaffolds as a potential biological platform for embryonic stem cells differentiation into hepatic-like cells lineage: A pilot study

Hepatic microenvironment plays an essential role in liver regeneration, providing the necessary conditions for cell proliferation, differentiation and tissue rearrangement. One of the key factors for hepatic tissue reconstruction is the extracellular matrix (ECM), which through collagenous and non-collagenous proteins provide a three-dimensional structure that confers support for cell adhesion and assists on their survival and maintenance. In this scenario, placental ECM may be eligible for hepatic tissue reconstruction, once these scaffolds hold the major components required for cell support. Therefore, this preliminary study aimed to access the possibility of mouse embryonic stem cells differentiation into hepatocyte-like cells on placental scaffolds in a three-dimensional dynamic system using a Rotary Cell Culture System. Following a four-phase differentiation protocol that simulates liver embryonic development events, the preliminary results showed that a significant quantity of cells adhered and interacted with the scaffold through outer and inner surfaces. Positive immunolabelling for alpha fetus protein and CK7 suggest presence of hepatoblast phenotype cells, and CK18 and Albumin positive immunolabelling suggest the presence of hepatocyte-like phenotype cells, demonstrating the presence of a heterogeneous population into the recellularized scaffolds. Periodic Acid Schiff-Diastase staining confirmed the presence of glycogen storage, indicating that differentiate cells acquired a hepatic-like phenotype. In conclusion, these preliminary results suggested that mouse placental scaffolds might be used as a biological platform for stem cells differentiation into hepatic-like cells and their establishment, which may be a promissing biomaterial for hepatic tissue reconstruction.

Circulating Plasma miR-122 and miR-583 Levels Are Involved in Chronic Hepatitis B Virus Pathogenesis and Serve As Novel Diagnostic Biomarkers

Background: MicroRNAs regulate many biological processes and are involved in the pathogenesis of many diseases including chronic hepatitis B (CHB). Moreover, besides investigation of their roles in hepatitis B virus (HBV) infection, a noninvasive, sensitive, and specific biomarker is essential in the diagnosis of liver diseases. This study was designed to evaluate the role of miR-122, miR-583, and miR-24 in the pathogenesis of CHB both in active chronic hepatitis (ACH) patients and in inactive carriers (IC). Materials and Methods: Plasma samples and all relevant clinical features were collected from 43 patients with CHB (28 ACH and 15 IC) and 43 healthy controls. Quantitative real-time PCR was performed to detect the plasma levels of miR-122, miR-583, and miR-24. Results: Results show miR-122 (p = 0.0001) and miR-583 (p = 0.006) but not miR-24 (p = 0.65) were upregulated in patients with CHB versus the control group. Interestingly, there was a significant increase in the plasma expression of miR-583 in IC versus ACH. Moreover, receiver operating characteristic curve analysis determined plasma levels of miR-122 (area under the ROC curve [AUC] = 0.89, p < 0.0001, sensitivity: 100%, specificity: 62.5%) and miR-583 (AUC = 0.71, p = 0.0007, sensitivity: 90%, specificity: 47.62%) as sensitive biomarkers to discriminate CHB patients from controls. Conclusion: Our data showed an increase in the plasma levels of miR-583 in IC versus ACH patients. Moreover, we demonstrated that miR-122 and miR-583 may serve as potential biomarkers for CHB diagnosis and activity.

Multicellular Liver Organoids: Generation and Importance of Diverse Specialized Cellular Components

Over 40,000 patients in the United States are estimated to suffer from end-stage liver disease and acute hepatic failure, for which liver transplantation is the only available therapy. Human primary hepatocytes (HPH) have not been employed as a therapeutic tool due to the difficulty in growing and expanding them in vitro, their sensitivity to cold temperatures, and tendency to dedifferentiate following two-dimensional culture. The differentiation of human-induced pluripotent stem cells (hiPSCs) into liver organoids (LO) has emerged as a potential alternative to orthotropic liver transplantation (OLT). However, several factors limit the efficiency of liver differentiation from hiPSCs, including a low proportion of differentiated cells capable of reaching a mature phenotype, the poor reproducibility of existing differentiation protocols, and insufficient long-term viability in vitro and in vivo. This review will analyze various methodologies being developed to improve hepatic differentiation from hiPSCs into liver organoids, paying particular attention to the use of endothelial cells as supportive cells for their further maturation. Here, we demonstrate why differentiated liver organoids can be used as a research tool for drug testing and disease modeling, or employed as a bridge for liver transplantation following liver failure.

The pharmacology and mechanisms of traditional Chinese medicine in promoting liver regeneration: A new therapeutic option

BACKGROUND

The liver is renowned for its remarkable regenerative capacity to restore its structure, size and function after various types of liver injury. However, in patients with end-stage liver disease, the regenerative capacity is inhibited and liver transplantation is the only option. Considering the limitations of liver transplantation, promoting liver regeneration is suggested as a new therapeutic strategy for liver disease. Traditional Chinese medicine (TCM) has a long history of preventing and treating various liver diseases, and some of them have been proven to be effective in promoting liver regeneration, suggesting the therapeutic potential in liver diseases.

PURPOSE

This review aims to summarize the molecular mechanisms of liver regeneration and the pro-regenerative activity and mechanism of TCM formulas, extracts and active ingredients.

METHODS

We conducted a systematic search in PubMed, Web of Science and the Cochrane Library databases using "TCM", "liver regeneration" or their synonyms as keywords, and classified and summarized the retrieved literature. The PRISMA guidelines were followed.

RESULTS

Forty-one research articles met the themes of this review and previous critical studies were also reviewed to provide essential background information. Current evidences indicate that various TCM formulas, extracts and active ingredients have the effect on stimulating liver regeneration through modulating JAK/STAT, Hippo, PI3K/Akt and other signaling pathways. Besides, the mechanisms of liver regeneration, the limitation of existing studies and the application prospect of TCM to promote liver regeneration are also outlined and discussed in this review.

CONCLUSION

This review supports TCM as new potential therapeutic options for promoting liver regeneration and repair of the failing liver, although extensive pharmacokinetic and toxicological studies, as well as elaborate clinical trials, are still needed to demonstrate safety and efficacy.

Temporal Dynamics of Metabolic Acquisition in Grafted Engineered Human Liver Tissue

Liver disease affects millions globally, and end-stage liver failure is only cured by organ transplant. Unfortunately, there is a growing shortage of donor organs as well as inequitable access to transplants across populations. Engineered liver tissue grafts that supplement or replace native organ function can address this challenge. While engineered liver tissues have been successfully engrafted previously, the extent to which these tissues express human liver metabolic genes and proteins remains unknown. Here, it is built engineered human liver tissues and characterized their engraftment, expansion, and metabolic phenotype at sequential stages post-implantation by RNA sequencing, histology, and host serology. Expression of metabolic genes is observed at weeks 1-2, followed by the cellular organization into hepatic cords by weeks 4-9.5. Furthermore, grafted engineered tissues exhibited progressive spatially restricted expression of critical functional proteins known to be zonated in the native human liver. This is the first report of engineered human liver tissue zonation after implantation in vivo, which can have important translational implications for this field.

Preclinical-to-clinical innovations in stem cell therapies for liver regeneration

Acute and chronic liver diseases are the major cause of high morbidity and mortality globally. Liver transplantation is a widely used therapeutic option for liver failure. However, the shortage of availability of liver donors has encouraged research on the alternative approach to liver regeneration. Cell-based regenerative medicine is the best alternative therapy to cater to this need. To date, advanced preclinical approaches have been undertaken on stem cell differentiation and their use in liver tissue engineering for generating efficacious and promising regenerative therapies. Advancements in the bioengineering of stem cells, and organoid generation are the way forward to efficient therapies against liver injury. This review summarizes the recent approaches for stem cell therapy-based liver regeneration and their proof of concepts for clinical application, bioengineering liver organoids to alleviate the liver failure caused due to chronic liver diseases.

Hepatic neddylation deficiency triggers fatal liver injury via inducing NF-κB-inducing kinase in mice

The conjugation of neural precursor cell expressed, developmentally downregulated 8 (NEDD8) to target proteins, termed neddylation, participates in many cellular processes and is aberrant in various pathological diseases. Its relevance to liver function and failure remains poorly understood. Herein, we show dysregulated expression of NAE1, a regulatory subunit of the only NEDD8 E1 enzyme, in human acute liver failure. Embryonic- and adult-onset deletion of NAE1 in hepatocytes causes hepatocyte death, inflammation, and fibrosis, culminating in fatal liver injury in mice. Hepatic neddylation deficiency triggers oxidative stress, mitochondrial dysfunction, and hepatocyte reprogramming, potentiating liver injury. Importantly, NF-κB-inducing kinase (NIK), a serine/Thr kinase, is a neddylation substrate. Neddylation of NIK promotes its ubiquitination and degradation. Inhibition of neddylation conversely causes aberrant NIK activation, accentuating hepatocyte damage and inflammation. Administration of N-acetylcysteine, a glutathione surrogate and antioxidant, mitigates liver failure caused by hepatic NAE1 deletion in adult male mice. Therefore, hepatic neddylation is important in maintaining postnatal and adult liver homeostasis, and the identified neddylation targets/pathways provide insights into therapeutically intervening acute liver failure.

miR-182-5p promotes hepatocyte-stellate cell crosstalk to facilitate liver regeneration

A unique feature of the liver is its high regenerative capacity, which is essential to maintain liver homeostasis. However, key regulators of liver regeneration (LR) remain ill-defined. Here, we identify hepatic miR-182-5p as a key regulator of LR. Suppressing miR-182-5p, whose expression is significantly induced in the liver of mice post two-thirds partial hepatectomy (PH), abrogates PH-induced LR in mice. In contrast, liver-specific overexpression of miR-182-5p promotes LR in mice with PH. Overexpression of miR-182-5p failed to promote proliferation in hepatocytes, but stimulates proliferation when hepatocytes are cocultured with stellate cells. Mechanistically, miR-182-5p stimulates Cyp7a1-mediated cholic acid production in hepatocytes, which promotes hedgehog (Hh) ligand production in stellate cells, leading to the activation of Hh signaling in hepatocytes and consequent cell proliferation. Collectively, our study identified miR-182-5p as a critical regulator of LR and uncovers a Cyp7a1/cholic acid-dependent mechanism by which hepatocytes crosstalk to stellate cells to facilitate LR.

Hepatic miR-182-5p is identified as a key regulator of liver regeneration by stimulating Cyp7a1-mediated cholic acid production in hepatocytes and activating hedgehog (Hh) signaling, consequently increasing cell proliferation.

Mobilization of multilineage-differentiating stress-enduring cells into the peripheral blood in liver surgery

Purpose

This study investigated whether liver damage severity relates to the mobilization of multilineage-differentiating stress-enduring (Muse) cells, which are endogenous reparative pluripotent stem cells, into the peripheral blood (PB) and whether the degree of mobilization relates to the recovery of liver volume following human liver surgery.

Methods

Forty-seven patients who underwent liver surgery were included in the present study. PB-Muse cells were counted before surgery, on postoperative days (PODs) 3 and on POD 7. Liver volume was measured using computed tomography before and after surgery.

Results

The PB-Muse cell count increased after surgery. The number of PB-Muse cells before surgery was higher, but without statistical significance in the group with neoplasms than in the healthy group that included liver donors (p = 0.065). Forty-seven patients who underwent liver surgery were divided into major hepatic resection (MHR; hepatectomy of three or more segments according to the Couinaud classification, n = 22) and minor hepatic resection (mhr; hepatectomy of two segments or less according to the Couinaud classification, n = 25) groups. PB-Muse cells increased at high rates among MHR patients (p = 0.033). Except for complication cases, PB-Muse cells increased at higher rates in the group with advanced liver volume recovery (p = 0.043). The predictive impact of the rate of increase in PB-Muse cells on the recovery of liver volume was demonstrated by multivariate analysis (OR 11.0, p = 0.014).

Conclusions

PB-Muse cell mobilization correlated with the volume of liver resection, suggesting that the PB-Muse cell number reflects the degree of liver injury. Given that the degree of PB-Muse cell mobilization was related to liver volume recovery, PB-Muse cells were suggested to contribute to liver regeneration, although this mechanism remains unclear.

Study protocol of Phase 2 open-label multicenter randomized controlled trial for granulocyte-colony stimulating factor (GCSF) in post-Kasai Type 3 biliary atresia

Animal studies support RCT findings of improved liver function and short-term benefits using repurposed Granulocyte Colonic Stimulating Factor GCSF in adults with decompensated cirrhosis. We describe the protocol for phase 2 RCT of sequential Kasai-GCSF under an FDA-approved IND to test that GCSF improves early bile flow and post-Kasai biliary atresia BA clinical outcome. Immediate post-Kasai neonates, age 15-180 days, with biopsy-confirmed type 3 BA, without access to early liver transplantation, will be randomized 1:1 to standard of care SOC + GCSF at 10 ug/kg in 3 daily doses within 4 days of Kasai vs SOC + NO-GCSF (ClinicalTrials.gov NCT0437391). They will be recruited from children's hospitals in Vietnam, Pakistan and one US center. The primary objective is to demonstrate that GCSF decreases the proportion of subjects with a 3-month post-Kasai serum Total Bilirubin ≥ 34 umol/L by 20%, (for a = 0.05, b = 0.80, i.e., calculated sample size of 218 subjects). The secondary objectives are to demonstrate that the frequency of post-Kasai cholangitis at 6-month and 24-month transplant-free survival are improved. The benefits are that GCSF is an affordable BA adjunct therapy, especially in developing countries, to improve biliary complications, enhance quality of liver and survival while diminishing costly liver transplantation.Clinical trial registration: A phase 1 for GCSF dose and safety determination under ClinicalTrials.gov identifier NCT03395028 was completed in 2019. The current Phase 2 trial was registered under NCT04373941.

Novel protein markers of androgen activity in humans: proteomic study of plasma from young chemically castrated men

Background

Reliable biomarkers of androgen activity in humans are lacking. The aim of this study was, therefore, to identify new protein markers of biological androgen activity and test their predictive value in relation to low vs. normal testosterone values and some androgen deficiency linked pathologies.

Methods

Blood samples from 30 healthy GnRH-antagonist treated males were collected at three time points: a) before GnRH antagonist administration; b) 3 weeks later, just before testosterone undecanoate injection, and c) after additional 2 weeks. Subsequently they were analysed by mass spectrometry to identify potential protein biomarkers of testosterone activity. Levels of proteins most significantly associated with testosterone fluctuations were further tested in a cohort of 75 hypo- and eugonadal males suffering from infertility. Associations between levels of those markers and cardio-metabolic parameters, bone mineral density as well as androgen receptor CAG repeat lengths, were explored.

Results

Using ROC analysis, 4-hydroxyphenylpyruvate dioxygenase (4HPPD), insulin-like growth factor-binding protein 6 (IGFBP6) and fructose-bisphosphate aldolase (ALDOB), as well as a Multi Marker Algorithm, based on levels of 4HPPD and IGFBP6, were shown to be best predictors of low (< 8 nmol/L) vs. normal (> 12 nmol/L) testosterone. They were also more strongly associated with metabolic syndrome and diabetes than testosterone levels. Levels of ALDOB and 4HPPD levels also showed association with AR CAG-repeat lengths.

Conclusions

We identified potential new protein biomarkers of testosterone action. Further investigations to elucidate their clinical potential are warranted.

Funding

The work was supported by ReproUnion 2.0 (grant no 20201846), which is funded by the Interreg V EU program.

MicroRNA-183 accelerates the proliferation of hepatocyte during liver regeneration through targeting programmed cell death protein 6

BACKGROUND

Liver regeneration is a highly orchestrated process concerning the modulation of various microRNAs (miRs). miR-183 was recently found to be involved in the process of liver regeneration, that miR-183 was remarkably up-regulated at 2-6 h after partial hepatectomy.

OBJECTIVE

This study was aimed to explore the mechanism of miR-183 in on liver regeneration.

METHODS

After partial hepatectomy (PH) or transfection, we measured the changes of miR-183 and programmed cell death protein 6 (PDCD6) levels in rats and the hepatocytes. The histopathology was observed with hematoxylin-eosin staining. The miR-183 mimic and inhibitor plasmids were intravenously injected into rats, and the liver weight/body weight ratio was calculated. The prediction of TargetScan and the validation of luciferase activity assay were employed to confirm the targeting relationship between miR-183 and PDCD6. The viability, apoptosis and cell cycle of transfected rat hepatocyte BRL-3A were determined via MTT and flow cytometry assays.

RESULTS

MiR-183 expression showed a contrary tendency with that of PDCD6 during liver regeneration. Enhanced miR-183 in rats could notably increase liver/body weight ratio, while its inhibition did conversely. Overexpressed PDCD6, a target of miR-183, repressed the viability and cell cycle in hepatocytes, whereas its silence led to contrary results. Overexpressed miR-183 in BRL-3A cells enhanced cell viability and promoted the cell cycle yet suppressed apoptosis, whereas its inhibition showed contrary results, which were offset by PDCD6.

CONCLUSIONS

Collectively, miR-183 promoted liver regeneration via targeting PDCD6.

A pan-metazoan concept for adult stem cells: the wobbling Penrose landscape

Adult stem cells (ASCs) in vertebrates and model invertebrates (e.g. Drosophila melanogaster) are typically long-lived, lineage-restricted, clonogenic and quiescent cells with somatic descendants and tissue/organ-restricted activities. Such ASCs are mostly rare, morphologically undifferentiated, and undergo asymmetric cell division. Characterized by 'stemness' gene expression, they can regulate tissue/organ homeostasis, repair and regeneration. By contrast, analysis of other animal phyla shows that ASCs emerge at different life stages, present both differentiated and undifferentiated phenotypes, and may possess amoeboid movement. Usually pluri/totipotent, they may express germ-cell markers, but often lack germ-line sequestering, and typically do not reside in discrete niches. ASCs may constitute up to 40% of animal cells, and participate in a range of biological phenomena, from whole-body regeneration, dormancy, and agametic asexual reproduction, to indeterminate growth. They are considered legitimate units of selection. Conceptualizing this divergence, we present an alternative stemness metaphor to the Waddington landscape: the 'wobbling Penrose' landscape. Here, totipotent ASCs adopt ascending/descending courses of an 'Escherian stairwell', in a lifelong totipotency pathway. ASCs may also travel along lower stemness echelons to reach fully differentiated states. However, from any starting state, cells can change their stemness status, underscoring their dynamic cellular potencies. Thus, vertebrate ASCs may reflect just one metazoan ASC archetype.

Role of the Microenvironment in Mesenchymal Stem Cell-Based Strategies for Treating Human Liver Diseases

Liver disease is a severe health problem that endangers human health worldwide. Mesenchymal stem cell (MSC) therapy is a novel treatment for patients with different liver diseases due to its vast expansion potential and distinctive immunomodulatory properties. Despite several preclinical trials having confirmed the considerable efficacy of MSC therapy in liver diseases, the questionable safety and efficacy still limit its application. As a precursor cell, MSCs can adjust their characteristics in response to the surrounding microenvironment. The microenvironment provides physical and chemical factors essential for stem cell survival, proliferation, and differentiation. However, the mechanisms are still not completely understood. We, therefore, summarized the mechanisms underlying the MSC immune response, especially the interaction between MSCs and the liver microenvironment, discussing how to achieve better therapeutic effects.

Granulocyte-colony stimulating factor GCSF mobilizes hematopoietic stem cells in Kasai patients with biliary atresia in a phase 1 study and improves short term outcome

AIMS

In RCT of adults with decompensated cirrhosis, GCSF mobilizes hematopoietic stem cells HSC and improves short-term outcome. An FDA-IND for sequential Kasai-GCSF treatment in biliary atresia BA was approved. This phase 1 study examines GCSF safety in Kasai subjects. Preliminary short-term outcome was evaluated.

METHODS

GCSF (Neupogen) at 5 or 10 μg/kg (n = 3/group) was given in 3 daily doses starting on day 3 of Kasai surgery (NCT03395028). Serum CD34+ HSC cell counts, and 1-month of GCSF-related adverse events were monitored. The 6-months Phase 1 clinical outcome was compared against 10 subsequent post Phase 1 Kasai patients who did not receive GCSF.

RESULTS

With GCSF, WBC and platelet count transiently increased, LFT and serum creatinine remained stable. Reversible splenic enlargement (by 8.5-20%) occurred in 5/6 subjects. HSC count increased 12-fold and 17.5-fold for the 5 μg/kg and10 ug/kg dose respectively; with respective median total bilirubin levels for GCSF vs no-GCSF groups of 55 vs 91 μM at 1 month, p = 0.05; 15 vs 37 μM at 3 months, p = 0.24); and the 6-months cholangitis frequency of 40% vs 90%, p = 0.077.

CONCLUSIONS

GCSF safely mobilizes HSC in Kasai infants and may improve short-term biliary drainage and cholangitis. Phase 2 efficacy outcome of GCSF adjunct therapy for sequential Kasai and GCSF is pending.

Exendin-4 gene modification and microscaffold encapsulation promote self-persistence and antidiabetic activity of MSCs

Mesenchymal stem cell (MSC)-based therapy to combat diabetic-associated metabolic disorders is hindered by impoverished cell survival and limited therapeutic effects under high glucose stress. Here, we genetically engineered MSCs with Exendin-4 (MSC-Ex-4), a glucagon-like peptide-1 (GLP-1) analog, and demonstrated their boosted cellular functions and antidiabetic efficacy in the type 2 diabetes mellitus (T2DM) mouse model. Mechanistically, MSC-Ex-4 achieved self-augmentation and improved survival under high glucose stress via autocrine activation of the GLP-1R-mediated AMPK signaling pathway. Meanwhile, MSC-Ex-4-secreted Exendin-4 suppressed senescence and apoptosis of pancreatic β cells through endocrine effects, while MSC-Ex-4-secreted bioactive factors (e.g., IGFBP2 and APOM) paracrinely augmented insulin sensitivity and decreased lipid accumulation in hepatocytes through PI3K-Akt activation. Furthermore, we encapsulated MSC-Ex-4 in 3D gelatin microscaffolds for single-dose administration to extend the therapeutic effect for 3 months. Together, our findings provide mechanistic insights into Exendin-4-mediated MSCs self-persistence and antidiabetic activity that offer more effective MSC-based therapy for T2DM.

Nuclear VEGFR-2 Expression of Hepatocytes Is Involved in Hepatocyte Proliferation and Liver Regeneration During Chronic Liver Injury

BACKGROUND/AIM

The pathological role of vascular endothelial growth factor receptor 2 (VEGFR-2) in chronic liver injury and liver regeneration is not fully understood. This study analysed the role of VEGFR-2 in liver fibrosis and its regeneration process.

MATERIALS AND METHODS

We administered intraperitoneally 50 mg/kg to 300 mg/kg thioacetamide (TAA) to 9-week-old male mice for 17 weeks. We measured levels of VEGFR-2 protein and identified the location of cells that specifically express VEGFR-2.

RESULTS

VEGFR-2 is rarely expressed in normal hepatocytes. However, high VEGFR-2 expression in liver sinusoidal endothelial cells was noted in the TAA group. Conversely, the group that experienced regeneration from liver fibrosis showed significantly higher VEGFR-2 expression in the nucleus of hepatocytes compared to the other groups.

CONCLUSION

VEGFR-2 plays a pivotal role in the nucleus of hepatocytes during liver regeneration and VEGFR-2 may be closely related to cell division. Therefore, VEGFR-2 may be a new therapeutic target for liver regeneration.

Alginate-chitosan core-shell microcapsule cultures of hepatic cells in a small scale stirred bioreactor: impact of shear forces and microcapsule core composition

A small scale stirred bioreactor was designed and the effect of different agitation rates (30, 60 and 100 rpm) was investigated on HepG2 cells cultured in alginate-chitosan (AC) core-shell microcapsule in terms of the cell proliferation and liver-specific function. The microencapsulated hepatic cells could proliferate well when they were cultured for 10 days at 30 rpm while the cell-laden microcapsules showed no cell proliferation at 100 rpm in the bioreactor system. Albumin production rate, as an important liver function, increased also 1.8- and 1.5- fold under stirring rate of 30 rpm compared to the static culture and 60 rpm of agitation, respectively. Moreover, In comparison with the static culture, about 1.5-fold increment in urea production was observed at 30 rpm. Similarly, the highest expressions of albumin and P450 genes were found at 30 rpm stirring rate, which were 4.9- and 19.2-fold of the static culture. Addition of collagen to the microcapsule core composition (ACol/C) could improve the cell proliferation and functionality at 60 rpm in comparison with the cell-laden microcapsules without collagen. The study demonstrated the hepatic cell-laden ACol/C microcapsule hydrogel cultured in the small scale stirred bioreactor at low mixing rate has a great potential for mass production of the hepatic cells while maintaining liver-specific functions.

Molecular pathways of liver regeneration: A comprehensive review

The liver is a unique parenchymal organ with a regenerative capacity allowing it to restore up to 70% of its volume. Although knowledge of this phenomenon dates back to Greek mythology (the story of Prometheus), many aspects of liver regeneration are still not understood. A variety of different factors, including inflammatory cytokines, growth factors, and bile acids, promote liver regeneration and control the final size of the organ during typical regeneration, which is performed by mature hepatocytes, and during alternative regeneration, which is performed by recently identified resident stem cells called “hepatic progenitor cells”. Hepatic progenitor cells drive liver regeneration when hepatocytes are unable to restore the liver mass, such as in cases of chronic injury or excessive acute injury. In liver maintenance, the body mass ratio is essential for homeostasis because the liver has numerous functions; therefore, a greater understanding of this process will lead to better control of liver injuries, improved transplantation of small grafts and the discovery of new methods for the treatment of liver diseases. The current review sheds light on the key molecular pathways and cells involved in typical and progenitor-dependent liver mass regeneration after various acute or chronic injuries. Subsequent studies and a better understanding of liver regeneration will lead to the development of new therapeutic methods for liver diseases.

Postnatal Pluripotent Cells: Quarter of a Century of Research

Almost quarter of a century long studies aimed at identification, isolation, culturing, and use of postnatal pluripotent cells for the development of cell-based technologies have not met with success and failed to provide reliable and reproducible protocols of cell isolation, identification, and culturing. At the same time, experimental data in this field suggest that postnatal pluripotent cells are not the copies of embryonic cells and, therefore, the tests routinely used for identification of embryonic pluripotent cells are not fully adequate for characterization of their postnatal analogues. Therefore, cell lineage tracing methods showing the differentiation routes of the studied cells in human or animal body after birth should be developed and used.

Recent advances in bioprinting technologies for engineering hepatic tissue

In the sphere of liver tissue engineering (LTE), 3D bioprinting has emerged as an effective technology to mimic the complex in vivo hepatic microenvironment, enabling the development of functional 3D constructs with potential application in the healthcare and diagnostic sector. This review gears off with a note on the liver's microscopic 3D architecture and pathologies linked to liver injury. The write-up is then directed towards unmasking recent advancements and prospects of bioprinting for recapitulating 3D hepatic structure and function. The article further introduces available stem cell opportunities and different strategies for their directed differentiation towards various hepatic stem cell types, including hepatocytes, hepatic sinusoidal endothelial cells, stellate cells, and Kupffer cells. Another thrust of the article is on understanding the dynamic interplay of different hepatic cells with various microenvironmental cues, which is crucial for controlling differentiation, maturation, and maintenance of functional hepatic cell phenotype. On a concluding note, various critical issues and future research direction towards clinical translation of bioprinted hepatic constructs are discussed.

Cell therapy as a new approach on hepatic fibrosis of murine model of Schistosoma mansoni-infection

BACKGROUND

Schistosomiasis is an acute and chronic disease of the genus Schistosoma triggered by blood flukes. Schistosomiasis is a disease occurring in, or endemic to, tropical and subtropical regions. A new concept was implemented to deal with schistosomiasis from natural plant sources. Curcumin's common name is Turmeric. Curcumin has proven to be main active component in Curcuma longa L. and has a wide range of anti-phrastic effects. Previous studies have shown the role of bone marrow mesenchymal stem cells (BMSCs) therapy in hepatic fibrosis recovery.

OBJECTIVE

The current study was, therefore, intended to examine therapeutic role of BMSCs and Turmeric in murine schistosomiasis mansoni.

ANIMALS

Mice were divided into five groups: a negative control group (non-infected non-treated), a positive control group (infected non-treated), a BMSCs treated group; Turmeric treated group, and untreated group. BMSCs derived from male mice were injected intraperitoneally into female mice receiving S. mansoni cercariae through the subcutaneous route. Liver histopathology and immuno-histochemical examinations were evaluated.

RESULTS

BMSCs intraperitoneal injection resulted in a significant reduction of liver collagen, granuloma size, and significant increase of OV-6 expression in the Schistosomiasis-treated mice group. There was overall improvement in pathological changes of the liver. Unfortunately, group IV showed a mild improvement in the granuloma size and fibrosis compared to corresponding BMSCs treatment group, although with vacuolated liver cells.

CONCLUSION AND CLINICAL RELEVANCE

BMSCs have a regenerative potential in liver tissue histopathology by decreasing liver fibrosis and granulomas. Turmeric, by contrast, could not be used as an anti-fibrotic, according to the findings.

NAIP expression increases in a rat model of liver mass restoration

The neuronal apoptosis inhibitory protein (NAIP) is a constituent of the NLRC4 inflammasome, which plays a key role in innate immunity, and an antiapoptotic protein. Recently, we reported the previously undescribed role of NAIP in cell division. The liver is one of the body's most actively regenerative organs. Given the novel mitotic role of NAIP, we examined its expression in hepatic mass restoration. The major liver lobe of Wistar rats was removed, and samples from both newly formed liver tissue, assessed by positive Ki67 immunostaining, and the remnant, intact liver lobes from hepatectomized rats were taken 3 and 7 days after surgery. Naip5 and Naip6 mRNA levels were significantly higher in regenerating hepatic tissue than in intact liver lobe tissue, and this increase was also observed at the protein level. Naip5 and Naip6 mRNA in situ hybridization showed that this increase occurred in the hepatic parenchyma. The histology of the regenerated liver tissue was normal, with the exception of a noticeable deficiency of hepatic lobule central veins. The results of this study suggest the involvement of NAIP in liver mass restoration following partial hepatectomy.

Some Special Aspects of Liver Repair after Resection and Administration of Multipotent Stromal Cells in Experiment

Changes in rat liver after resection and injection of autologous multipotent mesenchymal stromal cells of bone marrow origin (MSCs) transfected with the GFP gene and cell membranes stained with red-fluorescent lipophilic membrane dye were studied by light microscopy. It was found that after the introduction of MSCs into the damaged liver, their differentiation into any cells was not found. However, under the conditions of MSCs use, the number of neutrophils in the parenchyma normalizes earlier, and necrosis and hemorrhages disappear more quickly. It was concluded that the use of MSCs at liver resection for the rapid restoration of an organ is inappropriate, since the injected cells in vivo do not differentiate either into hepatocytes, into epithelial cells of bile capillaries, into endotheliocytes and pericytes of the vascular membranes, into fibroblasts of the scar or other connective tissue structures, or into any other cells present in the liver.

[Liver regeneration: resolved and problem issues]

Liver is an exceptional organ due to unique anatomical and physiological features, as well as advanced regenerative ability. Discovery of molecular mechanisms governing liver regeneration allowed researchers to use them to enhance liver regeneration. However, significant progress in this area was achieved through the introduction of gene therapy. In this manuscript, the authors consider stem cells for cell therapy and tissue engineering, as well as an alternative to liver transplantation.

The antiretroviral 2',3'-dideoxycytidine causes mitochondrial dysfunction in proliferating and differentiated HepaRG human cell cultures

Nucleoside reverse transcriptase inhibitors (NRTIs) were the first drugs used to treat human immunodeficiency virus infection, and their use can cause mitochondrial toxicity, including mitochondrial DNA (mtDNA) depletion in several cases. The first-generation NRTIs, including 2',3'-dideoxycytidine (ddC), were originally and are still pursued as anticancer agents. NRTI-sensitive DNA polymerases localizing to mitochondria allow for the opportunity to poison proliferating cancer cell mtDNA replication as certain cancers rely heavily on mitochondrial functions. However, mtDNA replication is independent of the cell cycle creating a significant concern that toxicants such as ddC impair mtDNA maintenance in both proliferating and nonproliferating cells. To examine this possibility, we tested the utility of the HepaRG cell line to study ddC-induced toxicity in isogenic proliferating (undifferentiated) and nonproliferating (differentiated) cells. Following ddC exposures, we measured cell viability, mtDNA copy number, and mitochondrial bioenergetics utilizing trypan blue, Southern blotting, and extracellular flux analysis, respectively. After 13 days of 1 μM ddC exposure, proliferating and differentiated HepaRG harbored mtDNA levels of 0.9% and 17.9% compared with control cells, respectively. Cells exposed to 12 μM ddC contained even less mtDNA. By day 13, differentiated cell viability was maintained but declined for proliferating cells. Proliferating HepaRG bioenergetic parameters were severely impaired by day 8, with 1 and 12 μM ddC, whereas differentiated cells displayed defects of spare and maximal respiratory capacities (day 8) and proton-leak linked respiration (day 14) with 12 μM ddC. These results indicate HepaRG is a useful model to study proliferating and differentiated cell mitochondrial toxicant exposures.

Cell Sources and Influencing Factors of Liver Regeneration: A Review

Liver regeneration (LR) is a set of complicated mechanisms between cells and molecules in which the processes of initiation, maintenance, and termination of liver repair are regulated. Although LR has been studied extensively, there are still numerous challenges in gaining its full understanding. Cells for LR have a wide range of sources and the feature of plasticity, and regeneration patterns are not the same under different conditions. Many patients undergoing partial hepatectomy develop cirrhosis or steatosis. The changes of LR in these cases are not clear. Many types of cells participate in LR. Hepatocytes, biliary epithelial cells, hepatic progenitor cells, and human liver stem cells can serve as the cell sources for LR. However, different types and degrees of damage trigger the response from the most suitable cells. Exploring the cell sources of LR is of great significance for accelerating recovery of liver function under different pathological patterns and developing a cell therapy strategy to cope with the shortage of donors for liver transplantation. In clinical practice, the background of the liver influences regeneration. Fibrosis and steatosis create different LR microenvironments and signal molecule interaction patterns. In addition, factors such as partial hepatectomy, aging, platelets, nerves, hormones, bile acids, and gut microbiota are widely involved in this process. Understanding the influencing factors of LR has practical value for individualized treatment of patients with liver diseases. In this review, we have summarized recent studies and proposed our views. We discuss cell sources and the influential factors on LR to help in solving clinical problems.

Solid Organ Bioprinting: Strategies to Achieve Organ Function

The field of tissue engineering has advanced over the past decade, but the largest impact on human health should be achieved with the transition of engineered solid organs to the clinic. The number of patients suffering from solid organ disease continues to increase, with over 100 000 patients on the U.S. national waitlist and approximately 730 000 deaths in the United States resulting from end-stage organ disease annually. While flat, tubular, and hollow nontubular engineered organs have already been implanted in patients, in vitro formation of a fully functional solid organ at a translatable scale has not yet been achieved. Thus, one major goal is to bioengineer complex, solid organs for transplantation, composed of patient-specific cells. Among the myriad of approaches attempted to engineer solid organs, 3D bioprinting offers unmatched potential. This review highlights the structural complexity which must be engineered at nano-, micro-, and mesostructural scales to enable organ function. We showcase key advances in bioprinting solid organs with complex vascular networks and functioning microstructures, advances in biomaterials science that have enabled this progress, the regulatory hurdles the field has yet to overcome, and cutting edge technologies that bring us closer to the promise of engineered solid organs.

Structure-Dependent Effects of Phthalates on Intercellular and Intracellular Communication in Liver Oval Cells

Humans are exposed to phthalates released from plastics, cosmetics, or food on a daily basis. Phthalates have low acute liver toxicity, but their chronic exposures could induce molecular and cellular effects linked to adverse health outcomes, such as liver tumor promotion or chronic liver diseases. The alternation of gap junctional intercellular communication (GJIC) and MAPK-Erk1/2 pathways in liver progenitor or oval cells can disrupt liver tissue homeostatic mechanisms and affect the development and severity of these adverse outcomes. Our study with 20 different phthalates revealed their structurally dependent effects on liver GJIC and MAPK-Erk1/2 signaling in rat liver WB-F344 cell line with characteristics of liver oval cells. The phthalates with a medium-length side chain (3–6 C) were the most potent dysregulators of GJIC and activators of MAPK-Erk1/2. The effects occurred rapidly, suggesting the activation of non-genomic (non-transcriptional) mechanisms directly by the parental compounds. Short-chain phthalates (1–2 C) did not dysregulate GJIC even after longer exposures and did not activate MAPK-Erk1/2. Longer chain (≥7 C) phthalates, such as DEHP or DINP, moderately activated MAPK-Erk1/2, but inhibited GJIC only after prolonged exposures (>12 h), suggesting that GJIC dysregulation occurs via genomic mechanisms, or (bio)transformation. Overall, medium-chain phthalates rapidly affected the key tissue homeostatic mechanisms in the liver oval cell population via non-genomic pathways, which might contribute to the development of chronic liver toxicity and diseases.

Enhancing the Therapeutic Potential of Mesenchymal Stem Cells with the CRISPR-Cas System

Mesenchymal stem cells (MSCs), also known as multipotent mesenchymal stromal stem cells, are found in the perivascular space of several tissues. These cells have been subject of intense research in the last decade due to their low teratogenicity, as well as their ability to differentiate into mature cells and to secrete immunomodulatory and trophic factors. However, they usually promote only a modest benefit when transplanted in experimental disease models, one of the limitations for their clinical application. The CRISPR-Cas system, in turn, is highlighted as a simple and effective tool for genetic engineering. This system was tested in clinical trials over a relatively short period of time after establishing its applicability to the edition of the mammalian cell genome. Similar to the research evolution in MSCs, the CRISPR-Cas system demonstrated inconsistencies that limited its clinical application. In this review, we outline the evolution of MSC research and its applicability, and the progress of the CRISPR-Cas system from its discovery to the most recent clinical trials. We also propose perspectives on how the CRISPR-Cas system may improve the therapeutic potential of MSCs, making it more beneficial and long lasting.

Quantification of common and planar bile acids in tissues and cultured cells

Bile acids (BAs) have been established as ubiquitous regulatory molecules implicated in a large variety of healthy and pathological processes. However, the scope of BA heterogeneity is often underrepresented in current literature. This is due in part to inadequate detection methods, which fail to distinguish the individual constituents of the BA pool. Thus, the primary aim of this study was to develop a method that would allow the simultaneous analysis of specific C24 BA species, and to apply that method to biological systems of interest. Herein, we describe the generation and validation of an LC-MS/MS assay for quantification of numerous BAs in a variety of cell systems and relevant biofluids and tissue. These studies included the first baseline level assessment for planar BAs, including allocholic acid, in cell lines, biofluids, and tissue in a nonhuman primate (NHP) laboratory animal, Macaca mulatta, in healthy conditions. These results indicate that immortalized cell lines make poor models for the study of BA synthesis and metabolism, whereas human primary hepatocytes represent a promising alternative model system. We also characterized the BA pool of M. mulatta in detail. Our results support the use of NHP models for the study of BA metabolism and pathology in lieu of murine models. Moreover, the method developed here can be applied to the study of common and planar C24 BA species in other systems.

Powerful Homeostatic Control of Oligodendroglial Lineage by PDGFRα in Adult Brain

Oligodendrocyte progenitor cells (OPCs) are widely distributed cells of ramified morphology in adult brain that express PDGFRα and NG2. They retain mitotic activities in adulthood and contribute to oligodendrogenesis and myelin turnover; however, the regulatory mechanisms of their cell dynamics in adult brain largely remain unknown. Here, we found that global Pdgfra inactivation in adult mice rapidly led to elimination of OPCs due to synchronous maturation toward oligodendrocytes. Surprisingly, OPC densities were robustly reconstituted by the active expansion of Nestin⁺ immature cells activated in meninges and brain parenchyma, as well as a few OPCs that escaped from Pdgfra inactivation. The multipotent immature cells were induced in the meninges of Pdgfra-inactivated mice, but not of control mice. Our findings revealed powerful homeostatic control of adult OPCs, engaging dual cellular sources of adult OPC formation. These properties of the adult oligodendrocyte lineage and the alternative OPC source may be exploited in regenerative medicine.

Exosomes derived from chemically induced human hepatic progenitors inhibit oxidative stress induced cell death

The emerging field of regenerative medicine has revealed that the exosome contributes to many aspects of development and disease through intercellular communication between donor and recipient cells. However, the biological functions of exosomes secreted from cells have remained largely unexplored. Here, we report that the human hepatic progenitor cells (CdHs)‐derived exosome (EXO^hCdHs) plays a crucial role in maintaining cell viability. The inhibition of exosome secretion treatment with GW4869 results in the acceleration of reactive oxygen species (ROS) production, thereby causing a decrease of cell viability. This event provokes inhibition of caspase dependent cell death signaling, leading to a ROS‐dependent cell damage response and thus induces promotion of antioxidant gene expression or repair of cell death of hypoxia‐exposed cells. Together, these findings show the effect of exosomes in regeneration of liver cells, and offer valuable new insights into liver regeneration.