Upregulation of Foreign Body Response in Obese Mice

Amitriptyline efficacy in decreasing implant-induced foreign body reaction

Beyond its actions on the nervous system, amitriptyline (AM) has been shown to lower inflammatory, angiogenic, and fibrogenic markers in a few pathological conditions in human and in experimental animal models. However, its effects on foreign body reaction (FBR), a complex adverse healing process, after biomedical material implantation are not known. We have evaluated the effects of AM on the angiogenic and fibrogenic components on a model of implant-induced FBR. Sponge disks were implanted subcutaneously in C57BL/6 mice, that were treated daily with oral administration of AM (5 mg/kg) for seven consecutive days in two protocols: treatment was started on the day of surgery and the implants were removed on the seventh day after implantation and treatment started 7 days after implantation and the implants removed 14 after implantation. None of the angiogenic (vessels, Vascular endothelial growth factor (VEGF), and interleukin-1β (IL-1β) or fibrogenic parameters (collagen, TGF-β, and fibrous capsule) and giant cell numbers analyzed were attenuated by AM in 7-day-old implants. However, AM was able to downregulate angiogenesis and FBR in 14-day-old implants. The effects of AM described here expands its range of actions as a potential agent capable of attenuating fibroproliferative processes that may impair functionality of implantable devices.

Sodium butyrate attenuates peritoneal fibroproliferative process in mice

NEW FINDINGS

What is the central question of this study? Peritoneal injury can result in a persistent fibroproliferative process in the abdominal cavity, causing pain and loss of function of internal organs. This study aimed to demonstrate the use of sodium butyrate (NaBu) as a potential agent to attenuate peritoneal fibrosis induced by a synthetic matrix. What is the main finding and its importance? Our findings provide the first evidence that NaBu attenuates the inflammatory, angiogenesis and fibrogenesis axes involved in the formation of peritoneal fibrovascular tissue, indicating the potential of this compound to ameliorate peritoneal fibrosis.

ABSTRACT

The aim of this study was to identify the bio-efficacy of sodium butyrate (NaBu) on preventing the development of peritoneal fibrovascular tissue induced by implantation of a synthetic matrix in the abdominal cavity. Polyether-polyurethane sponge discs were implanted in the peritoneal cavity of mice, which were treated daily with oral administration of NaBu (100 mg/kg). Control animals received water (100 μl). After 7 days, the implants were removed for assessment of inflammatory, angiogenic and fibrogenic markers. Compared with control values, NaBu treatment decreased mast cell recruitment/activation, inflammatory enzyme activities, levels of pro-inflammatory cytokines, and the proteins p65 and p50 of the nuclear factor-κB pathway. Angiogenesis, as determined by haemoglobin content, vascular endothelial growth factor levels and the number of blood vessels in the implant, was reduced by the treatment. In NaBu-treated animals, the predominant collagen present in the abdominal fibrovascular tissue was thin collagen, whereas in control implants it was thick collagen. Transforming growth factor-β1 levels were also lower in implants of treated animals. Sodium butyrate downregulated the inflammatory, angiogenesis and fibrogenesis axes of the fibroproliferative tissue induced by the intraperitoneal synthetic matrix. This compound has potential to control/regulate chronic inflammation and adverse healing processes in the abdominal cavity.

Carbon fiber reinforced polymers for implantable medical devices

Carbon fibers reinforced polymers (CFRPs) are prolifically finding applications in the medical field, moving beyond the aerospace and automotive industries. Owing to its high strength-to-weight ratio, lightness and radiolucency, CFRP-based materials are emerging to replace traditional metal-based medical implants. Numerous types of polymers matrices can be incorporated with carbon fiber using various manufacturing methods, creating composites with distinct properties. Thus, prior to biomedical application, comprehensive evaluation of material properties, biocompatibility and safety are of paramount importance. In this study, we systematically evaluated a series of novel CFRPs, aiming at analyzing biocompatibility for future development into medical implants or implantable drug delivery systems. These CFRPs were produced either via Carbon Fiber-Sheet Molding Compound or Fused Deposition Modelling-based additive manufacturing. Unlike conventional methods, both fabrication processes afford high production rates in a time-and cost-effective manner. Importantly, they offer rapid prototyping and customization in view of personalized medical devices. Here, we investigate the physicochemical and surface properties, material mutagenicity or cytotoxicity of 20 CFRPs, inclusive of 2 surface finishes, as well as acute and sub-chronic toxicity in mice and rabbits, respectively. We demonstrate that despite moderate in vitro physicochemical and surface changes over time, most of the CFRPs were non-mutagenic and non-cytotoxic, as well as biocompatible in small animal models. Future work will entail extensive material assessment in the context of orthopedic applications such as evaluating potential for osseointegration, and a chronic toxicity study in a larger animal model, pigs.

Amitriptyline Downregulates Chronic Inflammatory Response to Biomaterial in Mice

Recent data has signaled that in addition to its therapeutic indications as antidepressant and analgesic, amitriptyline (AM) exerts anti-inflammatory effects in humans and experimental animal models of acute inflammation. We tested the hypothesis that this compound could also modulate the chronic inflammatory process induced by synthetic matrix in mice. Polyether-polyurethane sponge disks were implanted subcutaneously in 9-week-old male C57BL/6 mice. The animals received by oral gavage 5.0 mg/kg of amitriptyline for seven consecutive days in two treatment regimens. In the first series, the treatment was initiated on the day of surgery and the implants removed at day 7 post-implantation. For the assessment of the effect of amitriptyline on chronic inflammation, the treatment was initiated 7 days post-implantation and the sponge discs removed 14 after implantation. The inflammatory markers evaluated, myeloperoxidase - MPO, nitrite content, IL-6, IFN-γ, TNF-α, CXCL1 and CCL2 levels, and NF-κB transcription factor activation were reduced in implants when the treatment began 7 days post-implantation (chronic inflammation). In contrast, only mast cell number, MPO activity and activation of NF-κB pathway decreased when the treatment began soon after implantation (sub-acute inflammation) in 7-day old implants. The anti-inflammatory effects of amitriptyline described here, extend its range of actions as a potential agent able to attenuate long-term inflammatory processes.

Engineered immunological niches to monitor disease activity and treatment efficacy in relapsing multiple sclerosis

Relapses in multiple sclerosis can result in irreversible nervous system tissue injury. If these events could be detected early, targeted immunotherapy could potentially slow disease progression. We describe the use of engineered biomaterial-based immunological niches amenable to biopsy to provide insights into the phenotype of innate immune cells that control disease activity in a mouse model of multiple sclerosis. Differential gene expression in cells from these niches allow monitoring of disease dynamics and gauging the effectiveness of treatment. A proactive treatment regimen, given in response to signal within the niche but before symptoms appeared, substantially reduced disease. This technology offers a new approach to monitor organ-specific autoimmunity, and represents a platform to analyze immune dysfunction within otherwise inaccessible target tissues.

Implant-induced inflammatory angiogenesis is up-regulated in obese mice

The damaging effects of obesity extend to multiple pre-existing tissue/organs. However, the influence of this condition on key components (inflammation and angiogenesis) of fibrovascular connective proliferating tissue, essential in repair processes, has been neglected. Our objective in this study was to investigate whether obesity would influence inflammatory-angiogenesis induced by synthetic matrix of polyether-polyurethane implanted subcutaneously in high-fat-fed obese C57/BL6 mice. Fourteen days after implantation, the inflammatory and angiogenic components of the newly formed tissue intra-implant were evaluated. The pro-inflammatory enzyme activities, myeloperoxidase (MPO) and N-acetyl-β-D-glucosaminidase (NAG), the levels of TNF-α, CXCL1/KC and CCL2 and NF-κB transcription factor were examined. Angiogenesis was determined by morphometric analysis of implant blood vessels, intra-implant levels of hemoglobin content, VEGF levels, and western blot for VEGFR2. All inflammatory and angiogenic markers were increased in the implants of obese mice compared with their non-obese counterparts. Similarly, activation of the NF-κB pathway and phosphorylation of VEGFR2 were higher in implants of obese mice (1.60 ± 0.28 Np65/Cp65; 0.96 ± 0.08 p-VEGFR2/VEGFR2-T) compared with implants of non-obese animals (1.40 ± 0.14; 0.49 ± 0.08). These observations suggest that obesity exerts critical role in sponge-induced inflammatory-angiogenesis, possibly by activating fibrovascular components in the inflamed microenvironment. Thus, this pathological condition causes damage not only to pre-existing tissues/organs but also to newly formed proliferating fibrovascular tissue. This is relevant to the development of therapeutic approaches to improve healing processes in patients with obesity.

Immunity to influenza: Impact of obesity

Obesity is a health concern that is recognized as a critical factor for vulnerability to influenza A/pdmH1N1 virus infection, with epidemiological and clinical impacts. In humans, obesity induces disturbances in inflammatory and immune responses to the influenza virus and in some cases, this leads to severe complications, with fatal outcomes. Obesity impairs immunity by altering the response of cytokines, resulting in a decrease in the cytotoxic cell response of immunocompetent cells which have a key anti-viral role. Additionally, obesity seems to disturb the balance of endocrine hormones, such as leptin, that affect the interplay between metabolic and immune systems. This contribution focuses on reviewing the current epidemiologic data for the immune response to immunity in obese humans and animal models. In doing so, we aim to provide potential mechanisms to enhance immunity to influenza A/pdmH1N1 virus infection and protective factors in obese people.