Hepatic Osteodystrophy: The Mechanism of Bone Loss in Hepatocellular Disease and the Effects of Pamidronate Treatment

Establishment of a human 3D in vitro liver-bone model as a potential system for drug toxicity screening

Drug toxicity is an important cause of chronic liver damage, which in the long term can lead to impaired bone homeostasis through an imbalance in the liver-bone axis. For instance, non-steroidal anti-inflammatory drugs (e.g., diclofenac), which are commonly used to control pain during orthopaedic interventions, are known to reduce bone quality and are the most prevalent causes of drug-induced liver damage. Therefore, we used human cell lines to produce a stable, reproducible, and reliable in vitro liver-bone co-culture model, which mimics the impaired bone homeostasis seen after diclofenac intake in vivo. To provide the best cell culture conditions for the two systems, we tested the effects of supplements contained in liver and bone cell culture medium on liver and bone cell lines, respectively. Additionally, different ratios of culture medium combinations on bone cell scaffolds and liver spheroids' viability and function were also analysed. Then, liver spheroids and bone scaffolds were daily exposed to 3-6 µM diclofenac alone or in co-culture to compare and evaluate its effect on the liver and bone system. Our results demonstrated that a 50:50 liver:bone medium combination maintains the function of liver spheroids and bone scaffolds for up to 21 days. Osteoclast-like cell activity was significantly upregulated after chronic exposure to diclofenac only in bone scaffolds co-cultured with liver spheroids. Consequently, the mineral content and stiffness of bone scaffolds treated with diclofenac in co-culture with liver spheroids were significantly reduced. Interestingly, our results show that the increase in osteoclastic activity in the system is not related to the main product of diclofenac metabolism. However, osteoclast activation correlated with the increase in oxidative stress and inflammation associated with chronic diclofenac exposure. In summary, we established a long-term stable liver-bone system that represents the interaction between the two organs, meanwhile, it is also an outstanding model for studying the toxicity of drugs on bone homeostasis.

Protective effect of hydroxysafflor yellow a on thioacetamide-induced liver injury and osteopenia in zebrafish

Hydroxysafflor yellow A (HSYA) is the main water-soluble compound of safflower. It is commonly used in liver disease treatment and has anti-osteoporotic activity. However, the specific mechanism of HSYA is not yet fully understood. Thioacetamide (TAA) has toxic effects on the liver and is widely used in establishing animal models of cirrhosis and liver fibrosis. In research of liver-related diseases and bone deformation in vivo, the zebrafish has become a frequently utilized animal model. In establishing a TAA-induced zebrafish liver injury model, we found that TAA-induced zebrafish also developed osteopenia. The aim of our study is to investigate the protective effect of HSYA on TAA-induced liver injury and osteopenia in zebrafish. The findings demonstrated that HSYA alleviated hepatic oxidative stress, inhibited the release of inflammatory factors, and promoted in vivo skeletal mineralization in zebrafish larvae. Further Real-time Polymerase Chain Reaction and Western blotting analyses showed that HSYA altered the expression levels of SIRT1, HMGB1, TLR4, MYD88 and NF-ΚB, ameliorated TAA-induced liver injury, reduced the release of inflammation-related factors IL-6, IL-1β, TNF-α, regulated the ratio of RANKL/OPG, ameliorated TAA-induced osteopenia. In conclusion, our study demonstrated that HSYA exhibited a noteworthy beneficial influence on TAA-induced liver injury and osteopenia in zebrafish, this finding provide a foundation for the application of HSYA in clinical research.

The Role of the Receptor Activator of Nuclear Factor Kappa-B Ligand/Osteoprotegerin Ratio in Vascular Diseases: A Therapeutic Approach

Cardiovascular and bone diseases contribute independently to mortality and global health. The exact mechanisms involved in the pathophysiology shared between bone and vascular diseases are not well defined. Endothelial cells and osteoblasts communicate during osteogenesis, thus establishing a connection between angiogenesis and osteogenesis. One shared mechanism may involve osteoprotegerin (OPG) and its ligand Receptor Activator of NF-κB Ligand (RANKL). The RANKL/OPG ratio is an important modulator for the skeletal, immunological, and vascular systems. OPG levels are elevated due to either osteogenic causes or inflammatory responses in the vasculature. The data obtained from clinical and in vitro studies support the role of the RANKL/OPG ratio as a potential marker for the progression of endothelial damage. Therefore, determining the therapeutic approaches for the targeting RANKL/OPG ratio and evaluating its usage as a biomarker in cardiovascular and bone pathophysiology are needed. By integrating the protective and disease-causing role of OPG with its ligand, this review outlines the role of the RANKL/OPG ratio at the molecular level. We also consider targeted therapeutic approaches.

Targeting hepatic oxidative stress rescues bone loss in liver fibrosis

OBJECTIVE

Chronic liver diseases often involve metabolic damage to the skeletal system. The underlying mechanism of bone loss in chronic liver diseases remains unclear, and appropriate therapeutic options, except for orthotopic liver transplantation, have proved insufficient for these patients. This study aimed to investigate the efficacy and mechanism of transplantation of immature hepatocyte-like cells converted from stem cells from human exfoliated deciduous teeth (SHED-Heps) in bone loss of chronic liver fibrosis.

METHODS

Mice that were chronically treated with CCl₄ received SHED-Heps, and trabecular bone density, reactive oxygen species (ROS), and osteoclast activity were subsequently analyzed in vivo and in vitro. The effects of stanniocalcin 1 (STC1) knockdown in SHED-Heps were also evaluated in chronically CCl₄ treated mice.

RESULTS

SHED-Hep transplantation (SHED-HepTx) improved trabecular bone loss and liver fibrosis in chronic CCl₄-treated mice. SHED-HepTx reduced hepatic ROS production and interleukin 17 (Il-17) expression under chronic CCl₄ damage. SHED-HepTx reduced the expression of both Il-17 and tumor necrosis factor receptor superfamily 11A (Tnfrsf11a) and ameliorated the imbalance of osteoclast and osteoblast activities in the bone marrow of CCl₄-treated mice. Functional knockdown of STC1 in SHED-Heps attenuated the benefit of SHED-HepTx including anti-bone loss effect by suppressing osteoclast differentiation through TNFSF11-TNFRSF11A signaling and enhancing osteoblast differentiation in the bone marrow, as well as anti-fibrotic and anti-ROS effects in the CCl₄-injured livers.

CONCLUSIONS

These findings suggest that targeting hepatic ROS provides a novel approach to treat bone loss resulting from chronic liver diseases.

Change in tartrate-resistant acid phosphatase isoform 5b levels, a marker of bone metabolism, in patients with chronic hepatitis B treated with tenofovir alafenamide

Hepatitis B virus (HBV) infection is associated with the risk of osteoporosis and bone mineral density (BMD) loss. Tenofovir alafenamide (TAF) is associated with a slightly lower degree of BMD loss compared with tenofovir disoproxil, without loss of the excellent anti-HBV effects. The aim of the present study was to verify the effect of bone metabolism in patients with HBV treated with TAF. A total of 87 patients were treated with TAF. Of these, 32 patients were treatment naïve, and 55 patients were treated with entecavir (ETV) for at least 1 year, after which ETV was switched to TAF. At the start of TAF and after 1 year, BMD in the lumbar and neck of the femur, tartrate-resistant acid phosphatase isoform 5b (TRACP-5b) levels as a marker of bone metabolism and serum inorganic phosphorus (P) were compared to estimate bone metabolism. Serum creatinine (Cr), cystatin C, urine protein and β2 microglobulin levels were evaluated to estimate kidney function. Treatment with TAF for 1 year decreased TRACP-5b levels, particularly in patients with bone disease, except for a minimal significant change (MSC; decrease of 12.4%) in TRACP-5b levels. The change in rate of TRACP-5b levels were positively associated with changes in P, Cr-estimated glomerular filtration rate and TRACP-5b levels at the start of TAF. Logistic regression analysis showed that increased BMD in the lumbar region contributed to the switch from ETV to TAF. TAF induced a decrease in TRACP-5b levels in patients with HBV. Bone disease was a contributing factor for MSC. Since TRACP-5b can be used as a marker of bone metabolism and fractures, TAF may exhibit potential in preventing fractures in patients with HBV.

Ex vivo vibro-acoustography characterization of osteoporosis in an experimental mice model

Background

Osteoporosis is a highly prevalent multifactorial osteometabolic disease, classically diagnosed, in vivo, by dual energy X-ray absorptiometry (DXA). This study evaluated osteoporosis, ex vivo, using vibro-acoustography (VA), an elastographic technique based on ultrasound radiation force.

Methods

Three groups of mice femurs were used: (I) control group (CG), (II) osteoporosis group (OG) and (III) treated osteoporosis group (TOG), in which the animals received pamidronate, an antiresorptive drug. Evaluation was performed in an acoustic tank, using two high frequency focused beams produced by a confocal ultrasonic transducer. A hydrophone registered the low frequency acoustic response (AR) of bone samples. We used micro-computed tomography (microCT) as the reference standard and evaluated the correlation between VA and microCT parameters.

Results

The spectral analyses of the ARs with estimated area under the curve (AUC) values (mean; st. dev.) were, respectively, 1.29e^-07 and 9.32e^-08 for the CG, 3.25e^-08 and 2.16e^-08 for the OG, and 1.50e^-07 and 8.37e^-08 for the TOG. VA differentiated the experimental groups (P<0.01) and the results were reproducible [interclass correlation coefficient (ICC): 0.43 (95% CI: 0.15-0.71)]. There was also a statistically significant association between VA and microCT connectivity (Conn.) (r=0.80; P<0.01) and connectivity density (Conn. D) (r=0.76; P<0.01).

Conclusions

These results encourage further studies aimed at evaluating the potential use of VA for the diagnosis of osteoporosis as a relatively low-cost and radiation-free alternative to DXA.