Clinical Significance of TNFSF14/LIGHT and CD160 in Gastric Cancer and Peptic Ulcer Dyspepsia.

BACKGROUND: Previous studies have reported the role of the Herpes Virus Entry Mediator (HVEM) in various cancer including gastric cancer. However, the expression level and clinical significance of CD160 and Tumor Necrosis Factor Ligand Superfamily Member 14 (TNFSF14) pathways in gastric cancer and gastric dyspepsia patients have remained unexplored. METHODS: The study involved the collection of gastric tissue biopsies from 42 patients with non-ulcerative dyspepsia (NUD) as the control group, 43 gastric cancer (GC) patients, and 48 patients with peptic-ulcerative dyspepsia (PUD). All the patients were endoscopically examined at Imam Khomeini Hospital in Sari, Mazandaran, Iran. The expression levels of TNFSF14 and CD160 mRNA were assessed using quantitative real-time PCR (qPCR) with the SYBR Green method. Statistical analysis was performed to investigate the potential association between the clinical and experimental data. RESULTS: Among the 133 gastric endoscopic biopsies examined, LIGHT exhibited a significant overexpression in GC patients (p-value < 0.01). Moreover, the expression of TNFSF14 was higher in GC patients with stages I and II (p-value<0.05). Furthermore, GC patients with TNM stages III+IV were accompanied by high expression levels of LIGHT (p-value < 0.01) as well as CD160 (p-value<0.05). The expression of CD160 was also higher in younger adults with PUD (p-value<0.05). Whereas TNFSF14 exhibited higher expression in older adults with GC (p-value<0.05). Furthermore, this research provided insights into the potential biological pathways and significant gene enrichment of TNFSF14 and CD160, suggesting the potential role of CD160 and TNFSF14 in the regulation of immune system in GC and PUD. CONCLUSION: These findings suggest the possible role of LIGHT and CD160 expression in gastric cancer patients in immune dysregulation toward gastric cancer. Targeted immunotherapy that harnessing co-stimulatory molecules like LIGHT and CD160 could be a promising approach in the treatment of GC as well as potential GC tumor markers.

Longitudinal Extensive Transverse Myelitis due to Varicella-Zoster Virus Infection in an Undiagnosed HIV-Positive Patient.

Introduction: Longitudinal extensive transverse myelitis (LETM) has four main causes: inflammatory, malnutrition, vascular, and infectious causes. Among the commonly described viral causes leading to LETM are the Herpesviridae family, HIV, and HTLV-1. Case Presentation. A 43-year-old man presented with asymmetric weakness of the lower limbs (the left side was weaker), urinary retention, and flank pain. The symptoms began five days after shingle eruption and progressed over twelve days. He was diagnosed with longitudinal extensive transvers myelitis extending from T4 to T6, which corresponded to the same dermatome involved in shingles. The PCR result of cerebrospinal fluid was positive for varicella-zoster virus with a viral load of 500 copies/ml. Additionally, the initial HIV enzyme-linked immunosorbent assay (ELISA) test was positive, and his CD4 count was 72 cells/mm3. Other lab results were normal. Based on the appearance of LETM in the thoracic MRI at T4-T6, VZV myelitis was diagnosed, and treatment was initiated with acyclovir (30 mg/kg divided daily for twenty-one days), methylprednisolone (1 g/day for three days), prophylactic antibiotics (trimethoprim/sulfamethoxazole, rifampin, and isoniazid), and antiretroviral therapy (dolutegravir and Truvada). After 2-month follow-up, he was nearly free of symptoms. Conclusion: Infection is one of the critical causes of transverse myelitis. When a patient presents with skin shingles along with myelopathy, varicella-zoster myelitis should be considered, and the patient should be evaluated in terms of immune system dysfunction. Treatment with acyclovir has been shown to be effective in reducing clinical symptoms in such cases.

Fracture behavior of human cortical bone with high glycation content under dynamic loading.

The present study simulates the fracture behavior of diabetic cortical bone with high levels of advanced glycation end-products (AGEs) under dynamic loading. We consider that the increased AGEs in diabetic cortical bone degrade the materials heterogeneity of cortical bone through a reduction in critical energy release rates of the microstructural features. To simulate the initiation and propagation of cracks, we implement a phase field fracture framework on 2D models of human tibia cortical microstructure. The simulations show that the mismatch between the fracture properties (e.g., critical energy release rate) of osteons and interstitial tissue due to high AGEs contents can change crack growth trajectories. The results show crack branching in the cortical microstructure under dynamic loading is affected by the mismatches related to AGEs. In addition, we observe cortical features such as osteons and cement lines can prevent multiple cracking under dynamic loading even with changing the mismatches due to high AGEs. Furthermore, under dynamic loading, some toughening mechanisms can be activated and deactivated with different AGEs contents. In conclusion, the current findings present that the combination of the loading type and materials heterogeneity of microstructural features can change the fracture response of diabetic cortical bone and its fragility.

Effective delivery of anti-PD-L1 siRNA with human heavy chain ferritin (HFn) in acute myeloid leukemia cell lines.

Because of the high biocompatibility, self-assembly capability, and CD71-mediated endocytosis, using human heavy chain ferritin (HFn) as a nanocarrier would greatly increase therapeutic effectiveness and reduce possible adverse events. Anti-PD-L1 siRNA can downregulate the level of PD-L1 on tumor cells, resulting in the activation of effector T cells against leukemia. Therefore, this study aimed to produce the tumor-targeting siPD-L1/HFn nanocarrier. Briefly, the HFn coding sequence was cloned into a pET-28a, and the constructed expression plasmid was subsequently transformed into E. coli BL21. After induction of Isopropyl ß-D-1-thiogalactopyranoside (IPTG), HFn was purified with Ni-affinity chromatography and dialyzed against PBS. The protein characteristics were analyzed using SDS-PAGE, Western Blot, and Dynamic light scattering (DLS). The final concentration was assessed using the Bicinchoninic acid (BCA) assay. The encapsulation was performed using the standard pH system. The treatment effects of siPD-L1/HFn were carried out on HL-60 and K-562 cancer cell lines. The RT-PCR was used to determine the mRNA expression of PD-L1. The biocompatibility and excretion of siPD-L1/HFn have also been evaluated. The expression and purity of HFn were well verified through SDS-PAGE, WB, and DLS. RT-PCR analyses also showed significant siRNA-mediated PD-L1 silencing in both HL-60 and K-562 cells. Our study suggested a promising approach for siRNA delivery. This efficient delivery system can pave the way for the co-delivery of siRNAs and multiple chemotherapies to address the emerging needs of cancer combination therapy.

Overcoming the inhibitory effects of urea to improve the kinetics of microbial-induced calcium carbonate precipitation (MICCP) by Lysinibacillus sphaericus strain MB284.

Among different microbial-induced calcium carbonate precipitation (MICCP) mechanisms utilized for biomineralization, ureolysis leads to the greatest yields of calcium carbonate. Unfortunately, it is reported that urea-induced growth inhibition can delay urea hydrolysis but it is not clear how this affects MICCP kinetics. This study investigated the impact of urea addition on the MICCP performance of Lysinibacillus sphaericus MB284 not previously grown on urea (thereafter named bio-agents), compared with those previously cultured in urea-rich media (20 g/L) (hereafter named bio-agents+ or bio-agents-plus). While it was discovered that initial urea concentrations exceeding 3 g/L temporarily hindered cell growth and MICCP reactions for bio-agents, employing bio-agents+ accelerated the initiation of bacterial growth by 33% and led to a 1.46-fold increase in the initial yield of calcium carbonate in media containing 20 g/L of urea. The improved tolerance of bio-agents+ to urea is attributed to the presence of pre-produced endogenous urease, which serves to reduce the initial urea concentration, alleviate growth inhibition, and expedite biomineralization. Notably, elevating the initial concentration of bio-agents+ from OD600 of 0.01 to 1, housing a higher content of endogenous urease, accelerated the initiation of MICCP reactions and boosted the ultimate yield of biomineralization by 2.6 times while the media was supplemented with 20 g/L of urea. These results elucidate the advantages of employing bio-agents+ with higher initial cell concentrations to successfully mitigate the temporary inhibitory effects of urea on biomineralization kinetics, offering a promising strategy for accelerating the production of calcium carbonate for applications like bio self-healing of concrete.

A statistical analysis of human talar shape and bone density distribution.

The shape of the talus, its internal structure, and its mechanical properties are important in determining talar behavior during loading, which may be significant for the design of surgical tools and implants. Although recent studies using statistical shape modeling have described quantitative talar external shape variation, no similar quantitative study exists to describe the density distribution of internal talar structure. The goal of this study is to quantify statistical variation in talar shape and density to benefit the design of talar implants. To this end, weight-bearing computed tomography (CT) scans of the ankle were collected in neutral, bilateral standing posture, and three-dimensional models were generated for each talus. Local density derived from the Hounsfield unit of each CT voxel was extracted. A weighted spherical harmonic analysis was performed to quantify the talar external shape. One hundred and seventy-nine volumes of interest were placed in the same relative position within each talus to quantify the talar density. Additionally, a finite element analysis (FEA) was conducted on a talus with both heterogeneous and homogeneous material properties to observe the effect of these properties on the stress and strain response. Significant differences were found in the talar density in sex and age, as well as in the stress and strain response between homogeneous and heterogeneous FEA. These differences show the importance of considering heterogeneity when examining the load response of tarsal bones.

The influence of propolis plus Hyoscyamus niger L. against COVID-19: A phase II, multicenter, placebo-controlled, randomized trial.

The incubation period of COVID-19 symptoms, along with the proliferation and high transmission rate of the SARS-CoV-2 virus, is the cause of an uncontrolled epidemic worldwide. Vaccination is the front line of prevention, and antiinflammatory and antiviral drugs are the treatment of this disease. In addition, some herbal therapy approaches can be a good way to deal with this disease. The aim of this study was to evaluate the effect of propolis syrup with Hyoscyamus niger L. extract in hospitalized patients with COVID-19 with acute disease conditions in a double-blinded approach. The study was performed on 140 patients with COVID-19 in a double-blind, randomized, and multicentral approach. The main inclusion criterion was the presence of a severe type of COVID-19 disease. The duration of treatment with syrup was 6 days and 30 CC per day in the form of three meals. On Days 0, 2, 4, and 6, arterial blood oxygen levels, C-reactive protein (CRP), erythrocyte sedimentation rate, and white blood cell, as well as the patient's clinical symptoms such as fever and chills, cough and shortness of breath, chest pain, and other symptoms, were recorded and analyzed. Propolis syrup with H. niger L. significantly reduces cough from the second day, relieving shortness of breath on the fourth day, and significantly reduces CRP, weakness, and lethargy, as well as significantly increased arterial blood oxygen pressure on the sixth day compared to the placebo group (p < 0.05). The results in patients are such that in the most severe conditions of the disease 80% < SpO2 (oxygen saturation), the healing process of the syrup on reducing CRP and increasing arterial blood oxygen pressure from the fourth day is significantly different compared with the placebo group (p < 0.05). The use of syrup is associated with a reduction of 3.6 days in the hospitalization period compared with the placebo group. Propolis syrup with H. niger L. has effectiveness in the viral and inflammatory phases on clinical symptoms and blood parameters and arterial blood oxygen levels of patients with COVID-19. Also, it reduces referrals to the intensive care unit and mortality in hospitalized patients with COVID-19. So, this syrup promises to be an effective treatment in the great challenge of COVID-19.

Fixation strength of swelling copolymeric anchors in artificial bone.

Fixation with suture anchors and metallic hardware for osteosynthesis is common in orthopedic surgeries. Most metallic commercial bone anchors achieve their fixation to bone through shear of the bone located between the threads. They have several deficiencies, including stress-shielding due to mechanical properties mismatch, generation of acidic by-products, poor osteointegration, low mechanical strength and catastrophic failure often associated with large bone defects that may be difficult to repair. To overcome these deficiencies, a swelling porous copolymeric material, to be used as bone anchors with osteointegration potential, was introduced. The purpose of this study was to investigate the fixation strength of these porous, swelling copolymeric bone anchors in artificial bone of various densities. The pull-out and subsidence studies indicate an effective fixation mechanism based on friction including re-fixation capabilities, and minimization of damage following complete failure. The study suggests that this swelling porous structure may provide an effective alternative to conventional bone anchors, particularly in low-density bone.

A seromolecular study to determine the prevalence of cytomegalovirus in pregnant women referred to health centers in the north of Iran.

Background and Objectives: Because of the controversial aspects of the CMV virus during pregnancy, it should be considered a serious health threat, especially in developing countries. The present seromolecular study aimed to determine cytomegalovirus prevalence in pregnant women referred to health centers in the north of Iran. Materials and Methods: One hundred and twenty-five pregnant women who were referred to health centers in Mazandaran province for regular health checks were randomly selected from Jan 2022 to Oct 2022. To detect the presence of the CMV genome and specific IgM and IgG antibodies against cytomegalovirus, the conventional PCR and ELISA tests were applied respectively. Results: All 125 pregnant women that attended the study were from Mazandaran province with a mean age of 30 years ranging from 20 to 42 years. The result showed that 2 (1.6%), 92 (73.6%), and 2 (1.6%) of the cases were positive for IgM, IgG, and IgM/IgG, respectively. The PCR test results indicated that the CMV DNA was present in 10 (8%) pregnant women. Our study shows that all PCR-positive cases were negative for the IgM test. Of the 10 PCR-positive samples 3 were positive and 1 was suspicious for the IgG test. Conclusion: Our study revealed that there is an urgent need for vaccination or other strategies to prevent and treat congenital CMV infection. Reducing the burden of congenital CMV infection requires global awareness. Further studies are recommended to obtain accurate estimates of the risk of congenital CMV infection.

Evaluation of mRNA Expressions of TOX and NR4As in CD8+ T cells in Acute Leukemia.

Background: Thymocyte selection-associated high mobility group box protein (TOX) and members of the nuclear receptor 4A (NR4A) are known as transcription factors involved in T cell exhaustion. Objective: To evaluate the mRNA expression of TOX and NR4A1-3 in CD8+ T cells in acute leukemia. Methods: Blood samples were obtained from 21 ALL and 6 AML patients as well as 20 control subjects. CD8+ T cells were isolated using MACS. Relative gene expression of TOX and NR4A1-3 was then evaluated using qRT-PCR. Results: Comparison of mRNA expression of TOX in CD8+ T cells showed no significant difference among the study groups (p>0.05), while the expression of NR4A1 was significantly lower in AML patients than in the control group (p=0.0006). Also, the expression of NR4A2 and NR4A3 was significantly lower in both ALL (p=0.0049 and p=0.0005, respectively) and AML (p=0.0019 and p=0.0055, respectively) patients. Conclusion: NR4As expressions were found to be lower in CD8+ T cells from patients with AML and ALL compared to controls, whereas the mRNA expression of TOX showed no significant difference. Although TOX and NR4As are associated with CD8+ T cell exhaustion in solid tumors, they might play different roles in acute leukemia, which requires further investigation.

Expression of Galectin-9-related immune checkpoint receptors in B-cell acute lymphoblastic leukemia.

Objectives: Exhausted CD8+ T-cells over-express immune checkpoint receptors (ICRs), which interact with their ligands on malignant cells. However, some ICRs have been reported to be expressed on both T-cells and tumor cells, including V-domain immunoglobulin suppressor of T cell activation (VISTA), Galectin-9, and T-cell immunoglobulin mucin-3 (TIM-3). We aimed to evaluate the mRNA expression of VISTA, Galectin-9, and TIM-3 on CD8+ T-cells and leukemic cells in B-cell acute lymphoblastic leukemia (B-ALL). Materials and Methods: Samples were obtained from 26 untreated B-ALL patients and 25 control subjects. CD8+ T-cells were isolated using Magnetic Activated Cell Sorting (MACS). Relative gene expression was then evaluated by qRT-PCR with specific primers for VISTA, Galectin-9, and TIM-3. Also, the mRNA expression profile and clinical data of 154 B-ALL patients were obtained from the TARGET. Results: mRNA expression of Galectin-9 on CD8+ T-cells in B-ALL patients was significantly lower than those in the control group (P=0.043), while VISTA expression was not significantly different between the two study groups (P=0.259). Besides, TIM-3 expression was significantly higher in B-ALL patients than in the control group (P<0.001). Also, data obtained from TARGET showed that the relapse incidence was not significantly different between patients with high and low expression of Galectin-9 and TIM-3 in leukemic cells (P=0.360 and P=0.655, respectively). Conclusion: Collectively, gene expression results suggest an important role for TIM-3, but not VISTA and Galectin-9, in B-ALL and it seems that TIM-3 could be a candidate for immune checkpoint therapy.

Immune response evaluation after Sputnik V vaccination in Sari healthcare population.

BACKGROUND AND OBJECTIVE: Generally, protection against SARS-CoV-2 was assessed by the measurement of antibody titers against spike protein and receptor binding domain "RBD". Many global efforts lead to development of several vaccines based on various strategies. The aim of the present study was to evaluate the efficacy of Sputnik V vaccine among Sari healthcare staff population, Iran. METHODS: Seventy-nine health professional staffs that were vaccinated with two doses of Sputnik V vaccine were selected. The Immune response against spike and RBD proteins was evaluated by ELISA assays 3-4 weeks after second dose of vaccine injection. RESULTS: The results showed the antibody titers were raised after vaccination. Data analysis has also demonstrated that the efficacy of vaccine was not related to age, gender and previous infection of SARS-CoV-2. CONCLUSION: Sputnik V vaccine can lead to a protective response against COVID-19 infection in high percentage of the population. J. Med. Invest. 70 : 317-320, August, 2023.

Single domain antibodies specific for HER2 dimerization domain effectively disrupts HER2 dimerization.

Dimer-dependent phosphorylation of HER2 receptor is a key event for the signal transduction of HER family of receptors which correlates with tumor invasion and metastasis. New generation of therapies based on dimerization domain inhibition using monoclonal or fragment antibodies was introduced. A potent method for manufacturing antibodies and antibody fragments is the phage display antibody library method. A recombinant phage was generated using the phage display method from synthetic dAb library. Subtractive biopanning was performed on sepharose 4b resin. Evaluation of success of subtractive biopanning was confirmed by the PCR fingerprinting after the fourth round of biopanning. The fourth round of biopanning results in the isolation of several dimerization domain reactive clones based on the polyclonal phage ELISA results. Monoclonal phage cell ELISA was used to select the positive clones with the highest affinity, and they were subsequently employed for functional tests. Cell-ELISA, MTT assay and dimerization inhibition test revealed that the reactivity and specificity of the selected monoclonal phage to dimerization domain of HER2. Further, Annexin V/PI staining and gene expression analysis showed that increased apoptosis rates. Also, in silico binding of the selected clones to conformational structure of HER2 was applied, using protein-protein docking tool of the ICM-Pro software, and showed sdAbs were specifically interacted with dimerization domain of the receptor. In conclusion, we have identified a single domain targeting HER2 dimerization, which represents a promising therapeutic and diagnostic candidate for HER2-positive cancers. Purified sdAb needs to more research to evaluate it both in vivo and in vitro via functional tests to determine if it can be applied for treatment and diagnostics.

Microstructural fatigue fracture behavior of glycated cortical bone.

The current study aims to simulate fatigue microdamage accumulation in glycated cortical bone with increased advanced glycation end-products (AGEs) using a phase field fatigue framework. We link the material degradation in the fracture toughness of cortical bone to the high levels of AGEs in this tissue. We simulate fatigue fracture in 2D models of cortical bone microstructure extracted from human tibias. The results present that the mismatch between the critical energy release rate of microstructural features (e.g., osteons and interstitial tissue) can alter crack initiation and propagation patterns. Moreover, the high AGEs content through the increased mismatch ratio can cause the activation or deactivation of bone toughening mechanisms under cyclic loading. The fatigue fracture simulations also show that the lifetime of diabetic cortical bone samples can be dependent on the geometry of microstructural features and the mismatch ratio between the features. Additionally, the results indicate that the trapped cracks in cement lines in the diabetic cortical microstructure can prevent further crack growth under cyclic loading. The present findings show that alterations in the materials heterogeneity of microstructural features can change the fatigue fracture response, lifetime, and fragility of cortical bone with high AGEs contents. Cortical bone models are created from microscopy images taken from the cortical cross-section of human tibias. Increased glycation contents in the cortical bone sample can change the crack growth trajectories.

Evaluation of mRNA Expression of CD244 and Its Adapter Molecules in CD8+ T Cells in Acute Leukemia.

Background: This study investigated the role of the immune-checkpoint receptor (ICR), CD244, and its adapter molecules, in CD8+ T cells in acute leukemia. Methods: Blood samples were obtained from 21 acute lymphoblastic leukemia (ALL) and 6 acute myeloid leukemia (AML) patients and 20 control subjects. Relative gene expression of CD244, immune receptor tyrosine-based switch motif-associated protein (SA), EWS/FLI1-activated transcript 2 (EAT-2), and LncRNA-GSTT1-AS1 were evaluated using quantitative reverse transcription polymerase chain reaction. Results: Expression of CD244, SAP, and EAT-2 were significantly lower in CD8+ T cells from ALL patients than those from control subjects. Interestingly, the expression of SAP was much lower than that of CD244, indicating a lower ratio of SAP to CD244. Also, SAP expression was significantly lower in AML patients compared to the control group. Expression of LncRNA-GSTT1-AS1 showed no significant difference in ALL and AML patients compared to control subjects. Conclusion: The low SAP/CD244 expression ratio in CD8+ T cells in ALL suggests an inhibitory role for CD244 in ALL.

Relative Expression of BATF and CD112 in PBMC of Patients with Chronic Lymphocytic Leukemia.

OBJECTIVE: BATF, as a transcription factor, and CD112, as a receptor for TIGIT, are involved in T-cell exhaustion. We investigated BATF and CD112 gene expression in the peripheral blood mononuclear cells from CLL patients and healthy subjects. METHODS: In a case-control study, 33 patients with CLL and 20 sex- and age-matched healthy individual were enrolled. Diagnosis and classification of patients was done according to immunophenotyping via flow cytometry and RAI staging system, respectively. Relative mRNA expression of BATF and CD112 was measured using qRT-PCR. RESULT: Our results showed that the expression of BATF and CD112 in CLL samples were significantly decreased in comparison those of the healthy controls (P = 0.0236 and P = 0.0002, respectively). CONCLUSION: These findings suggest the role of BATF and CD112 not only as a role in T cell exhaustion, but in effector differentiation program in CLL, which warrants further studies in future.

Numerical analysis of the mechanical response of novel swelling bone implants in polyurethane foams.

In this study, a numerical framework was developed in order to analyze the swelling properties, mechanical response and fixation strength of swelling bone anchors. Using this framework, fully porous and solid implants, along with a novel hybrid design (consisting of a solid core and a porous sleeve), were modeled and studied. Free swelling experiments were conducted to investigate their swelling characteristics. The finite element model of swelling was validated using the conducted free swelling. Compared with the experimental data, results obtained from the finite element analysis proved the reliability of this frame-work. Afterwards, the swelling bone anchors were studied embedded in artificial bones with different densities with two different interface properties: considering frictional interface between the bone anchors and artificial bones (simulating the stages prior to osteointegration, when the bone and implant are not fully bonded and the surface of the implant can slide along the interface), and perfectly bonded (simulating the stages subsequent to osteointegration, when the bone and implant are fully bonded). It was observed that the swelling considerably decreases while the average radial stress on the lateral surface of the swelling bone anchor surges in the denser artificial bones. Ultimately, the pull-out experiments and simulations of the swelling bone anchors from the artificial bones were conducted to look into the fixation strength of the swelling bone anchors. It was found that the hybrid swelling bone anchor exhibits mechanical and swelling properties close to those of solid bone anchors, while also bone in-growth is expected to happen, which is an integral factor to these bone anchors.

A porous swelling copolymeric material for improved implant fixation to bone.

Most metallic commercial bone anchors, such as screws and suture anchors achieve their fixation to bone through shear of the bone located between the threads. They have several deficiencies, potentially leading to failure, which are particularly evident in low-density bone. These include stress-shielding resulting from mechanical properties mismatch; lack of mechanically induced remodeling and osteointegration; and when the pullout force on the anchor, during functional activities, exceeds their pullout strength, catastrophic failure occurs leaving behind large bone defects that may be hard to repair. To overcome these deficiencies, we introduced in this study a porous swelling co-polymeric material and studied its swelling and compressive mechanical characteristics as bone anchor under different configurations. Porosity was achieved by adding a non-dissolvable agent (NaCl) during the process of polymerization, which was later dissolved in water, leaving behind a porous structure with adequate porosity for osteointegration. Three different groups of cylindrical samples of the swelling co-polymer were investigated. Solid, fully porous, and partially porous with a solid core and a porous outer layer. The results of the swelling and simple compression study show that the partially porous swelling co-polymer maintains excellent mechanical properties matching those of cancellous bone, quick swelling response, and an adequate porous outer layer for mechanically induced osteointegration. These suggest that this material may present an effective alternative to conventional bone anchors particularly in low-density bone.

Influence of age-related changes on crack growth trajectories and toughening mechanisms in human dentin.

OBJECTIVES: Dentin microstructure undergoes changes with age and its materials properties degrade over time. In the present study, we investigate the coupled influence of increased filled tubules and decreased materials properties on the fracture behavior of human dentin. METHODS: We assume degraded materials properties are linked with increased advanced glycation end-products (AGEs) crosslinks in dentin tissue. We use morphological data of human molars to create 2D and 3D models of dentin microstructure, and utilize a phase field fracture framework to study crack growth trajectories. We construct aged dentin samples (i.e., filled tubules and degraded properties) and compare the fracture results with the samples without age-related changes. RESULTS: The simulations show an increase in the number of filled tubules can deactivate the toughening mechanisms such as crack deflection and microcracking. In addition, filled tubules have adverse impacts on the ability of peritubular dentin to shield microcracking. We further show how the dentinal tubules' orientations affect the crack surface growth. We also investigate that an increase in the AGEs level can result in increased brittleness. SIGNIFICANCE: The developed model and findings of the present study provide region-dependent information on crack growth trajectories as well as more understanding of crack surface growth at the presence of filled tubules.