CD4+ and CD8+ T cells reduce inflammation and promote bone healing in response to titanium implants

T cells are adaptive immune cells essential in pathogenic response, cancer, and autoimmune disorders. During the integration of biomaterials with host tissue, T cells modify the local inflammatory environment by releasing cytokines that promote inflammatory resolution following implantation. T cells are vital for the modulation of innate immune cells, recruitment and proliferation of mesenchymal stem cells (MSCs), and formation of functional tissue around the biomaterial implant. We have demonstrated that deficiency of αβ T cells promotes macrophage polarization towards a pro-inflammatory phenotype and attenuates MSC recruitment and proliferation in vitro and in vivo. The goal of this study was to understand how CD4+ and CD8+ T cells, subsets of the αβ T cell family, impact the inflammatory response to titanium (Ti) biomaterials. Deficiency of either CD4+ or CD8+ T cells increased the proportion of pro-inflammatory macrophages, lowered anti-inflammatory macrophages, and diminished MSC recruitment in vitro and in vivo. In addition, new bone formation at the implantation site was significantly reduced in T cell-deficient mice compared to T cell-competent mice. Deficiency of CD4+ T cells exacerbated these effects compared to CD8+ T cell deficiency. Our results show the importance of CD4+ and CD8+ T cells in modulating the inflammatory response and promoting new bone formation in response to modified Ti implants. STATEMENT OF SIGNIFICANCE: CD4+ and CD8+ T cells are essential in modulating the peri-implant microenvironment during the inflammatory response to biomaterial implantation. This study shows that deficiency of either CD4+ or CD8+ T cell subsets altered macrophage polarization and reduced MSC recruitment and proliferation at the implantation site.

Contribution of αβ T cells to macrophage polarization and MSC recruitment and proliferation on titanium implants

Physiochemical cues like topography and wettability can impact the inflammatory response and tissue integration after biomaterial implantation. T cells are essential for immunomodulation of innate immune cells and play an important role in the host response to biomaterial implantation. This study aimed to understand how CD4+ and CD8+ T cell subsets, members of the αβ T cell family, polarize in response to smooth, rough, or rough-hydrophilic titanium (Ti) implants and whether their presence modulates immune cell crosstalk and mesenchymal stem cell (MSC) recruitment following biomaterial implantation. Post-implantation in mice, we found that CD4+ and CD8+ T cell subsets polarized differentially in response to modified Ti surfaces. Additionally, mice lacking αβ T cells had significantly more pro-inflammatory macrophages, fewer anti-inflammatory macrophages, and reduced MSC recruitment in response to modified Ti post-implantation than αβ T cell -competent mice. Our results demonstrate that T cell activation plays a significant role during the inflammatory response to implanted biomaterials, contributing to macrophage polarization and MSC recruitment and proliferation, and the absence of αβ T cells compromises new bone formation at the implantation site. STATEMENT OF SIGNIFICANCE: T cells are essential for immunomodulation and play an important role in the host response to biomaterial implantation. Our results demonstrate that T cells actively participate during the inflammatory response to implanted biomaterials, controlling macrophage phenotype and recruitment of MSCs to the implantation site.

Reduction of neutrophil extracellular traps accelerates inflammatory resolution and increases bone formation on titanium implants

Neutrophils are the most abundant immune cells in the blood and the first cells to be recruited to the biomaterial implantation site. Neutrophils are fundamental in recruiting mononuclear leukocytes to mount an immune response at the injury site. Neutrophils exert significant pro-inflammatory effects through the release of cytokines and chemokines, degranulation and release of myeloperoxidase (MPO) and neutrophil elastase (NE), and the production of large DNA-based networks called neutrophil extracellular traps (NETs). Neutrophils are initially recruited and activated by cytokines and pathogen- and damage-associated molecular patterns, but little is known about how the physicochemical composition of the biomaterial affects their activation. This study aimed to understand how ablating neutrophil mediators (MPO, NE, NETs) affected macrophage phenotype in vitro and osseointegration in vivo. We discovered that NET formation is a crucial mediator of pro-inflammatory macrophage activation, and inhibition of NET formation significantly suppresses macrophage pro-inflammatory phenotype. Furthermore, reducing NET formation accelerated the inflammatory phase of healing and produced greater bone formation around the implanted biomaterial, suggesting that NETs are essential regulators of biomaterial integration. Our findings emphasize the importance of the neutrophil response to implanted biomaterials and highlight innate immune cells' regulation and amplification signaling during the initiation and resolution of the inflammatory phase of biomaterial integration. STATEMENT OF SIGNIFICANCE: Neutrophils are the most abundant immune cells in blood and are the first to be recruited to the injury/implantation site where they exert significant pro-inflammatory effects. This study aimed to understand how ablating neutrophil mediators affected macrophage phenotype in vitro and bone apposition in vivo. We found that NET formation is a crucial mediator of pro-inflammatory macrophage activation. Reducing NET formation accelerated the inflammatory phase of healing and produced greater appositional bone formation around the implanted biomaterial, suggesting that NETs are essential regulators of biomaterial integration.

Immune cell response to orthopedic and craniofacial biomaterials depends on biomaterial composition

Materials for craniofacial and orthopedic implants are commonly selected based on mechanical properties and corrosion resistance. The biocompatibility of these materials is typically assessed in vitro using cell lines, but little is known about the response of immune cells to these materials. This study aimed to evaluate the inflammatory and immune cell response to four common orthopedic materials [pure titanium (Ti), titanium alloy (TiAlV), 316L stainless steel (SS), polyetheretherketone (PEEK)]. Following implantation into mice, we found high recruitment of neutrophils, pro-inflammatory macrophages, and CD4+ T cells in response to PEEK and SS implants. Neutrophils produced higher levels of neutrophil elastase, myeloperoxidase, and neutrophil extracellular traps in vitro in response to PEEK and SS than neutrophils on Ti or TiAlV. Macrophages co-cultured on PEEK, SS, or TiAlV increased polarization of T cells towards Th1/Th17 subsets and decreased Th2/Treg polarization compared to Ti substrates. Although SS and PEEK are considered biocompatible materials, both induce a more robust inflammatory response than Ti or Ti alloy characterized by high infiltration of neutrophils and T cells, which may cause fibrous encapsulation of these materials. STATEMENT OF SIGNIFICANCE: Materials for craniofacial and orthopedic implants are commonly selected based on their mechanical properties and corrosion resistance. This study aimed to evaluate the immune cell response to four common orthopedic and craniofacial biomaterials: pure titanium, titanium-aluminum-vanadium alloy, 316L stainless steel, and PEEK. Our results demonstrate that while the biomaterials tested have been shown to be biocompatible and clinically successful, the inflammatory response is largely driven by chemical composition of the biomaterials.

Canonical Wnt signaling enhances pro-inflammatory response to titanium by macrophages

Biomaterial characteristics like surface roughness and wettability can determine the phenotype of macrophages following implantation. We have demonstrated that inhibiting Wnt ligand secretion abolishes macrophage polarization in vitro and in vivo; however, the role of canonical Wnt signaling in macrophage activation in response to physical and chemical biomaterial cues is unknown. The aim of this study was to understand whether canonical Wnt signaling affects the response of macrophages to titanium (Ti) surface roughness or wettability in vitro and in vivo. Activating canonical Wnt signaling increased expression of toll-like receptors and interleukin receptors and secreted pro-inflammatory cytokines and reduced anti-inflammatory cytokines on Ti, regardless of surface properties. Inhibiting canonical Wnt signaling reduced pro-inflammatory cytokines on all Ti surfaces and increased anti-inflammatory cytokines on rough or rough-hydrophilic Ti. In vivo, activating canonical Wnt signaling increased total macrophages, pro-inflammatory macrophages, and T cells and decreased anti-inflammatory macrophages on both smooth and rough-hydrophilic implants. Functionally, canonical Wnt activation increases pro-inflammatory macrophage response to cell and cell-extracellular matrix lysates. These results demonstrate that activating canonical Wnt signaling primes macrophages to a pro-inflammatory phenotype that affects their response to Ti implants in vitro and in vivo.

E-cigarette Aerosol Mixtures Inhibit Biomaterial-Induced Osseointegrative Cell Phenotypes

OBJECTIVES

Smoking is a known contributor to the failure of dental implants. Despite a decline in cigarette use, the popularity of e-cigarettes has exploded. However, little is known about how e-cigarettes affect the biologic response to implants. This study examines the effect of e-cigarette aerosol mixtures (ecig-AM) on macrophage activation and osteoblastogenesis of mesenchymal stem cells (MSCs) in response to titanium (Ti) implant surfaces.

METHODS

Ecig-AMs were prepared by bubbling aerosol through PBS. Human-derived MSCs or murine-derived macrophages were plated on smooth, rough-hydrophobic, or rough-hydrophilic Ti surfaces in media supplemented with ecig-AM. In macrophages, expression of inflammatory markers was measured by qPCR and macrophage immunophenotype characterized by flow cytometry after 24 hours of exposure. In MSCs, expression of osteogenic markers and inflammatory cytokines was measured by qPCR and ELISA, while alkaline phosphatase activity (ALP) was determined by colorimetric assay.

RESULTS

Ecig-AM polarized primary macrophages into a pro-inflammatory state with higher effect on ecig-AM with flavorants and nicotine. Metabolic activity of MSCs decreased in a concentration dependent fashion and was stronger in ecig-AM containing nicotine. MSCs reduced expression of osteogenic markers in response to ecig-AM, but increased RANKL secretion, particularly at the highest ecig-AM concentrations. The effect of ecig-AM exposure was lessened when macrophages or MSCs were cultured on rough-hydrophilic substrates.

SIGNIFICANCE

Ecig-AM activated macrophages into a pro-inflammatory phenotype and impaired MSC-to-osteoblast differentiation in response to Ti implant surfaces. These effects were potentiated by flavorants and nicotine, suggesting that e-cigarette use may compromise the osseointegration of dental implants.

Control of innate immune response by biomaterial surface topography, energy, and stiffness

As the focus of implantable biomaterials has shifted from bioinert implants to bioactive designs, recent research has highlighted the complex interactions between cell physiologic systems and material properties, particularly physical cues. From the cells known to interact with implanted biomaterials, the response of the immune system has been a critical target of study recently. Here, we review studies characterizing the response of innate immune cells to various material cues, particularly of those at the surface of implanted materials.The innate immune system consists of cell types with various roles in inflammation. Neutrophils and macrophages serve both phagocytic and signaling roles, especially early in the inflammatory phase of biomaterial implantation. These cell types ultimately dictate the outcome of implants as chronic inflammation, fibrosis, or integration. Other cell types like dendritic cells, mast cells, natural killer cells, and innate lymphoid cells may also serve an immunomodulatory role in the biomaterial context. This review highlights recent advances in our understanding of the role of innate immunity in the response to implantable biomaterials as well as key mechanobiological findings in innate immune cells underpinning these advances. STATEMENT OF SIGNIFICANCE: This review highlights recent advances in the understanding of the role of innate immunity in the response to implantable biomaterials, especially in neutrophils and macrophages, as well as key mechanobiological findings in innate immune cells underpinning these advances. Here we discuss how physicochemical properties of biomaterials control innate immune cell behavior.

Dietary L-tryptophan modulates agonistic behavior and brain serotonin in male dyadic contests of a cichlid fish

Although some studies have investigated the effects of dietary L-tryptophan on agonistic behavior, research on adult fish specimens is still lacking. Moreover, submissive behaviors have been generally overlooked. We focused on agonistic behavior between males of the cichlid fish Cichlasoma dimerus, in dyadic encounters held in a novel context after being fed or not with an L-tryptophan enriched diet (TRP) for 2 weeks. We arranged three different dyads: control/control (control conditions: not TRP enriched), control/TRP, and TRP/TRP. We also registered the response of the brain serotonergic system in four brain regions. TRP/TRP dyads showed higher latencies to first attack, lower overall aggression, and lower proportions of bites and passive copings (submissive display) compared to control/control. TRP dominant males performed fewer bites with respect to controls, and subordinate males opposed to TRP males showed fewer passive copings. Higher serotonergic activities were found in subordinates' optic tectum and in the telencephalon and preoptic area/hypothalamus of TRP males. Altogether, results point out that dietary L-tryptophan reduced males' motivation to attack and dominant aggression, which consequently influenced subordinate agonistic repertory. In addition, males within TRP/TRP dyads showed a switch in their behavioral agonistic repertory. These behavioral outcomes were probably due to modifications at brain serotonergic functioning.

Frequency and exact position of valves in the saphenofemoral junction

Background: Varicose veins are common. As venous valves are included in the pathological development of varices they have been studied by many authors. Nonetheless, the exact position of valves is unclear. Material and method: The exact position of the valves in the greater saphenous vein was studied macroscopically from the saphenofemoral junction up to 25 cm distally in situ on 72 cadavers with a total of 140 veins. Results: A terminal valve existed in 88.5% in the range of 0 to 1.4 cm and a preterminal valve was present in 89.2% in the range of 1.4 cm to 8.2 cm distally to the saphenofemoral junction. In about a fifth of the cases a third valve could be identified. Conclusion: Our results suggest, that the recent general agreement that there are always a terminal and a preterminal valve has to be negated.

The pineal complex in the cichlid Cichlasoma dimerus: effect of different photoperiods on its cell morphology

This research describes the pineal complex histology in juvenile and adult Cichlasoma dimerus, and the effect of different photoperiods on its cell morphology. In both juveniles and adults, the pineal complex of C. dimerus has three components: the pineal organ, consisting of a pineal vesicle (PV) and a pineal stalk, the parapineal organ and the dorsal sac. Although a strong morphological resemblance exists between the two stages, different synthesis patterns of cone and rod opsins were detected in the two life stages. An effect of the photoperiod length was observed on putative pinealocytes' activity from the PV, measured indirectly through nuclear area morphometry. Individuals exposed to a natural photoperiod (14L:10D) had smaller nuclear areas (mean ± s.e. = 13·82 ± 1·52 µm(2) ) than those exposed to a short photoperiod (8:16) (21·45 ± 2·67 µm(2) ; P < 0·001). Eventually, the nuclear area of pinealocytes could be used as a putative indicator of melatonin synthesis in fishes where it is difficult to obtain plasma samples, e.g. due to its small size or age. This work constitutes one of the few comparative descriptions of the pineal complex of juvenile and adult teleost and suggests potential approaches for the study of melatonin synthesis in fish larvae or small adult fishes.

[Nutritional studies in a commune of Lazio. Anthropometric data and food consumption in childhood]

The present study concerns with anthropometric and nutritional data collected in the school population of a small rural town in Lazio. We studied 368 school-children of both sexes, belonging to the following age groups: from 7 to 8 years, 9 to 10 years, 11 to 12 years, 13 to 14 years. The technique of evaluation of obesity used in this paper is: weight 20% higher than the height-adjusted figure according to NCHS's curves and triceps skinfold higher than 90 degrees centile according to Tanner's curves. Dietary intake was assessed by a "24 hour-recall" on three consecutive days one of which of holiday. The prevalence of obesity is 17.7%. In all the age groups daily caloric intake is adjusted to that recommended by Italian 1987 Larn. On the other hand the single nutrient's assumption shows important differences from Larn. Particularly in all the age groups daily protein intake is high (14.6%-15.8% of the energy in a day), with an increased animal-vegetable protein ratio (1.5-2.1). Dietary lipids are higher than 35.9% of day's energy (35.9%-39.5%); the polyunsaturated/saturated fatty acids ratio is low (0.3-0.5). Cholesterol in the diet (231-347 mg/day) exceeds the level recommended. The daily intake of total carbohydrates (45.3%-48.5%) is low. Crude fiber intake increases with age from 2.8 g to 4.5 g/day. There is no statistical difference between obese and not obese subjects for what concerns energy intake or single nutrient's assumption.(ABSTRACT TRUNCATED AT 250 WORDS)

Free radical-induced lipoperoxidation and severe head injury. A clinical study

Ten severely head injured patients (GCS less than or equal to 8), aged 17-62 years, were studied in order to investigate the role of lipoperoxidation in secondary brain damage. No patients had intracranial mass lesions, shock, hypoxemia, fever or sepsis. Blood samples were taken from the jugular bulb and from the right atrium, and thiobarbituric acid reacting substances (TBARS) were measured in plasma by spectrophotometry. Arterio-jugular venous oxygen differences (AVDO2) were obtained in seven patients, in order to estimate cerebral blood flow. Jugular TBARS (TBARSj) were always elevated (from To, to 2 h after injury) and correlated in a linear fashion with TBARS of right atrium (TBARSv): r = 0.74, p less than 0.001. TBARSj and AVDO2 are closely correlated, in accordance with an exponential function (R = 0.45, p less than 0.001) which describes how any cerebral perfusion derangement determines high levels of TBARSj, confirming lipoperoxidation as a key factor in the final common pathway of secondary posttraumatic brain damage.

[The transcutaneous method of monitoring partial pressure of O2 and CO2 during laser surgery of the trachea and bronchi]

Anesthesia during Nd-YAG laser resection of the airways necessitates continuous O2 and CO2 monitoring. Although only partial, monitoring may be performed using a transcutaneous method utilising Clark's electrode to measure O2 and Stowe-Severinghaus' electrode to assess CO2 on the skin surface. The paper evaluates the advantages and limits of this form of monitoring during anesthesia in 85 patients undergoing laser resection of the airways. In conclusion, in spite of the fact that it is currently impossible to build up a complete picture of blood gas status from a single transcutaneous finding, the use of the transcutaneous method increases the level of safety of the operation as a whole.