Potential Role of L-Arginine and Vitamin E Against Bone Loss Induced by Nano-Zinc Oxide in Rats

The effect of L-Arginine therapy on achilles tendon healing: A histological and biomechanical investigation in an animal model

PURPOSE

Several clinical and experimental studies have revealed that L-Arginine, which has antioxidant properties, accelerates tissue healing. This study examined the in vivo effects of oral L - Arginine supplementation on tendon regeneration in Wistar rats.

METHOD

For each weighting of an average of 250-300 g, 24 Wistar rats were separated into three equal groups. Each rat's right hind leg Achilles tendons were tenotomized and then repaired. The first group (Control) was followed up with a regimen of standard food and water. In the second group (L-Arg Low Dose), 300 mg/kg, and in the third group (L-Arg High Dose), 600 mg/kg L-Arginine was administered in water daily with a regimen of standard food and water ad libitum. After eight weeks, the rats were sacrificed, and the tendons were histologically and biomechanically analyzed.

RESULTS

Tendon peak strength values of the L-Arg Low Dose and L-Arg High Dose groups were similar but significantly higher than the control group. A statistically significant difference was observed between the groups in terms of ground substance, fiber arrangement, cellularity, hyalinization, and GAG properties ( p = 0.05, p = 0.002, p = 0.016, p = 0.027, p = 0.05). There was no statistically significant difference between the groups according to the histological examination of collagen properties, fiber structure, tenocyte properties, rounding of the nuclei, and collagen stainability. (p = 0.999, p = 0.061, p = 0.195, p = 0.195, p = 0.130). No mortality, wound complications, or re-ruptures were observed.

CONCLUSION

Compared with the control group, histologically and biomechanically distinct therapeutic effects of L-Arginine supplementation on tendon healing were determined.

LEVEL OF CLINICAL EVIDENCE

5.

Stage-specific roles of microbial dysbiosis and metabolic disorders in rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a progressive disease including four stages, where gut microbiome is associated with pathogenesis. We aimed to investigate stage-specific roles of microbial dysbiosis and metabolic disorders in RA.

METHODS

We investigated stage-based profiles of faecal metagenome and plasma metabolome of 76 individuals with RA grouped into four stages (stages I-IV) according to 2010 RA classification criteria, 19 individuals with osteroarthritis and 27 healthy individuals. To verify bacterial invasion of joint synovial fluid, 16S rRNA gene sequencing, bacterial isolation and scanning electron microscopy were conducted on another validation cohort of 271 patients from four RA stages.

RESULTS

First, depletion of Bacteroides uniformis and Bacteroides plebeius weakened glycosaminoglycan metabolism (p<0.001), continuously hurting articular cartilage across four stages. Second, elevation of Escherichia coli enhanced arginine succinyltransferase pathway in the stage II and stage III (p<0.001), which was correlated with the increase of the rheumatoid factor (p=1.35×10-3) and could induce bone loss. Third, abnormally high levels of methoxyacetic acid (p=1.28×10-8) and cysteine-S-sulfate (p=4.66×10-12) inhibited osteoblasts in the stage II and enhanced osteoclasts in the stage III, respectively, promoting bone erosion. Fourth, continuous increase of gut permeability may induce gut microbial invasion of the joint synovial fluid in the stage IV.

CONCLUSIONS

Clinical microbial intervention should consider the RA stage, where microbial dysbiosis and metabolic disorders present distinct patterns and played stage-specific roles. Our work provides a new insight in understanding gut-joint axis from a perspective of stages, which opens up new avenues for RA prognosis and therapy.

Vitamin Supplementation Protects against Nanomaterial-Induced Oxidative Stress and Inflammation Damages: A Meta-Analysis of In Vitro and In Vivo Studies

The extensive applications of nanomaterials have increased their toxicities to human health. As a commonly recommended health care product, vitamins have been reported to exert protective roles against nanomaterial-induced oxidative stress and inflammatory responses. However, there have been some controversial conclusions in regards to this field of research. This meta-analysis aimed to comprehensively evaluate the roles and mechanisms of vitamins for cells and animals exposed to nanomaterials. Nineteen studies (seven in vitro, eleven in vivo and one in both) were enrolled by searching PubMed, EMBASE, and Cochrane Library databases. STATA 15.0 software analysis showed vitamin E treatment could significantly decrease the levels of oxidants [reactive oxygen species (ROS), total oxidant status (TOS), malondialdehyde (MDA)], increase anti-oxidant glutathione peroxidase (GPx), suppress inflammatory mediators (tumor necrosis factor-α, interleukin-6, C-reactive protein, IgE), improve cytotoxicity (manifested by an increase in cell viability and a decrease in pro-apoptotic caspase-3 activity), and genotoxicity (represented by a reduction in the tail length). These results were less changed after subgroup analyses. Pooled analysis of in vitro studies indicated vitamin C increased cell viability and decreased ROS levels, but its anti-oxidant potential was not observed in the meta-analysis of in vivo studies. Vitamin A could decrease MDA, TOS and increase GPx, but its effects on these indicators were weaker than vitamin E. Also, the combination of vitamin A with vitamin E did not provide greater anti-oxidant effects than vitamin E alone. In summary, we suggest vitamin E alone supplementation may be a cost-effective option to prevent nanomaterial-induced injuries.

Osteoporosis: Current and Emerging Therapies Targeted to Immunological Checkpoints

Osteoporosis is a skeletal pathology characterized by compromised bone strength leading to increased risk of fracture, mainly the spine and hip fractures. Osteoporosis affects more than 200 million people worldwide and because of the skeletal fractures it causes, represents a major cause of morbidity, disability and mortality in older people. Recently, the new discoveries of osteoimmunology have clarified many of the pathogenetic mechanisms of osteoporosis, helping to identify new immunological targets for its treatment opening the way for new and effective therapies with biological drugs. Currently, there are basically two monoclonal antibodies for osteoporosis therapy: denosumab and romosozumab. Here, we focus on the modern approach to the osteoporosis management and in particular, on current and developing biologic drugs targeted to new immunological checkpoints, in the landscape of osteoimmunology.

Oral Exposure to ZnO Nanoparticles Disrupt the Structure of Bone in Young Rats via the OPG/RANK/RANKL/IGF-1 Pathway

Purpose

To evaluate the effects of ZnO NPs on bone growth in rats and explore the possible mechanisms of action.

Materials and Methods

Three-week-old male rats received ultrapure water or 68, 203, and 610 mg/kg zinc oxide nanoparticles (ZnO NPs) for 28 days, orally.

Results

The high-dosage groups caused significant differences in weight growth rate, body length, and tibia length (P<0.05), all decreasing with increased ZnO NP dosage. There were no significant differences in body mass index (BMI) (P>0.05). The zinc concentration in liver and bone tissue increased significantly with increased ZnO NP dosage (P<0.05). Clearly increased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were observed in the 610 mg/kg ZnO NP group (P>0.05), whereas alkaline phosphatase (ALP) increased in the 610 mg/kg ZnO NP group (P<0.05). Significant differences in insulin-like growth factor type 1 (IGF-1) levels and a decrease in calcium (Ca) levels were observed in 203 and 610 mg/kg ZnO NP groups (P<0.05). Phosphorus (P) levels increased and the Ca/P ratio decreased in the 610 mg/kg ZnO NP group (P<0.05). Micro-computed tomography (micro-CT) of the tibia demonstrated signs of osteoporosis, such as decreased bone density, little trabecular bone structure and reduced cortical bone thickness. Micro-CT data further demonstrated significantly decreased bone mineral density (BMD), trabecular number (Tb.N), and relative bone volume (BV/TV) with increasing dosage of ZnO NPs. Osteoprotegerin (OPG) expression and the ratio of OPG to receptor activator of nuclear factor-κB ligand (RANKL) were statistically lower in the 610 mg/kg ZnO NP group (P<0.05), whereas RANKL expression did not change significantly (P>0.05).

Conclusion

We infer that ZnO NPs affect bone growth in young rats directly or indirectly by altering IGF-1 levels. Overall, the results indicate that ZnO NPs promote osteoclast activity and increase bone loss through the OPG/RANK/RANKL/IGF-1 pathway.

Enhancing ZnO-NP Antibacterial and Osteogenesis Properties in Orthopedic Applications: A Review

Prosthesis-associated infections and aseptic loosening are major causes of implant failure. There is an urgent need to improve the antibacterial ability and osseointegration of orthopedic implants. Zinc oxide nanoparticles (ZnO-NPs) are a common type of zinc-containing metal oxide nanoparticles that have been widely studied in many fields, such as food packaging, pollution treatment, and biomedicine. The ZnO-NPs have low toxicity and good biological functions, as well as antibacterial, anticancer, and osteogenic capabilities. Furthermore, ZnO-NPs can be easily obtained through various methods. Among them, green preparation methods can improve the bioactivity of ZnO-NPs and strengthen their potential application in the biological field. This review discusses the antibacterial abilities of ZnO-NPs, including mechanisms and influencing factors. The toxicity and shortcomings of anticancer applications are summarized. Furthermore, osteogenic mechanisms and synergy with other materials are introduced. Green preparation methods are also briefly reviewed.