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-1ß (IL-1ß) or fibrogenic parameters (collagen, TGF-ß, 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.

ST2 deletion accelerates inflammatory-angiogenesis and remodeling in subcutaneous implants in mice.

Implantation of biomedical/synthetic devices to replace and/or repair biological tissues very often induces an adverse healing response (scarce angiogenesis, excessive collagen deposition) which is detrimental to implant functionality and integration to host tissue. Interleukin-33/ST2 axis (IL-33/ST2) has been shown to modulate angiogenic and remodeling processes in several types of injuries. However, its effects on these processes after implantation of synthetic matrix have not been reported. Using synthetic matrix of polyether-polyurethane implanted subcutaneously in mice lacking ST2 receptor (ST2/KO), we characterized neovascularization and matrix remodeling in the fibrovascular tissue induced by the implants. Tissue accumulation was increased inside and around the implants in KO implants relative to the wild type (WT). More intense proliferative activity, using CDC 47 marker, was observed in KO implants compared with that of WT implants. Angiogenesis, using two endothelial cell markers, Von Willebrand Factor (VWF) and vascular endothelial cell VE cadherin and hemoglobin content, increased in implants of KO mice relative to control WT. Remodeling of the newly formed fibrovascular tissue (soluble collagen and PicroSirius Red-stained histological sections) showed predominance of type 1 collagen in ST2-KO implants versus type 3 in control implants. The number of positive cells for caspase-3, apoptotic marker, decreased in ST2 group. Our findings evidenced a role of IL-33/ST2 axis in restraining blood vessel formation and regulating the pattern of matrix remodeling in the fibrovascular tissue induced by synthetic implants. Intervention in this cytokine complex holds potential to accelerate integration of biomaterial and host tissue by improving blood supply and matrix remodeling.

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.

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-ß-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.

Sodium Butyrate Downregulates Implant-Induced Inflammation in Mice.

Sodium butyrate (NaBu), a histone deacetylase inhibitor, has shown to exert beneficial actions attenuating inflammation in a number of intestinal and extra-intestinal diseases. However, the effects of NaBu on persistent inflammatory processes as in a response to implantation of foreign material have not been investigated. Synthetic matrix of polyether-polyurethane sponge was implanted in mice's subcutaneous layer of the dorsal region, and the animals were treated daily with oral administration of NaBu (100 mg/kg). After 7 days, the implants were removed and processed for assessment of inflammatory markers. Butyrate treatment caused a significant attenuation of neutrophil and macrophage infiltration in implants, which was reflected by the reduction of myeloperoxidase and N-acetyl-ß-D-glucosaminidase activities, respectively. Similar reduction was observed in intra-implants nitrite levels of NaBu-treated mice. NaBu treatment was also able to decrease mast cell recruitment/activation and the levels of CXCL1, CCL2, IL-6, TNF-ɑ, and TGF-ß1 in the implants but did not alter the levels of IL-10. In addition, NaBu administration decreased the concentration of proteins p65 and p50 in the nucleus as compared with the cytoplasm by western blot analysis. This result suggests that treatment with NaBu inhibited the NF-κB pathway. The circulating levels of TNF-ɑ and TGF-ß1 were also attenuated by NaBu. Persistent inflammation at sites of implanted devices very often impairs their functionality; therefore, our findings suggest that NaBu holds potential therapeutic value to control this adverse response to biomedical implants.