Foreign Body Reaction Research Articles

Wear and corrosion of titanium alloy spinal implants in vivo

To investigate the wear and corrosion of titanium alloy spinal implants in vivo, we evaluated removed implants and their surrounding scar tissues from 27 patients between May 2019 and April 2021. We performed scanning electron microscopy, energy-dispersive X-ray spectroscopy, and histological analysis. The results revealed metal-like particles in the soft tissues of seven patients, without any considerable increase in inflammatory cell infiltration. Patients with fractures showed lower percentages of wear and corrosion compared with other patients (42% and 17% vs. 59% and 26%). Polyaxial screws exhibited higher wear and corrosion percentages (53% and 23%) compared with uniaxial screws (39% and 3%), although in patients with fracture, the reverse was observed (20% and 0% vs. 39% and 3%). We found that titanium alloy spinal implants experience some degree of wear and corrosion in vivo. The titanium alloy particles formed by wear exhibited good histocompatibility, not causing inflammation, foreign body reactions, or osteolysis. Therefore, spinal implants should be removed cautiously when treating titanium alloy spinal metallosis. The wear and corrosion of the implants increase with the increase in implantation time, although the screw structure does not significantly affect these changes.

Understanding the Foreign Body Response via Single-Cell Meta-Analysis.

Foreign body response (FBR) is a universal reaction to implanted biomaterial that can affect the function and longevity of the implant. A few studies have attempted to identify targets for treating FBR through the use of single-cell RNA sequencing (scRNA-seq), though the generalizability of these findings from an individual study may be limited. In our study, we perform a meta-analysis of scRNA-seq data from all available FBR mouse studies and integrate these data to identify gene signatures specific to FBR across different models and anatomic locations. We identify subclusters of fibroblasts and macrophages that emerge in response to foreign bodies and characterize their signaling pathways, gene ontology terms, and downstream mediators. The fibroblast subpopulations enriched in the setting of FBR demonstrated significant signaling interactions in the transforming growth factor-beta (TGF-β) signaling pathway, with known pro-fibrotic mediators identified as top expressed genes in these FBR-derived fibroblasts. In contrast, FBR-enriched macrophage subclusters highly expressed pro-fibrotic and pro-inflammatory mediators downstream of tumor necrosis factor (TNF) signaling. Cell-cell interactions were additionally interrogated using CellChat, with identification of key signaling interactions enriched between fibroblasts and macrophages in FBR. By combining multiple FBR datasets, our meta-analysis study identifies common cell-specific gene signatures enriched in foreign body reactions, providing potential therapeutic targets for patients requiring medical implants across a myriad of devices and indications.

Few incidentally found interesting foreign objects in human body: a case series

Foreign bodies are objects that do not typically belong in the human body but can be ingested, inserted, or entered due to injuries. This article presents various cases and examples of foreign bodies, including objects swallowed, objects inserted into the rectum, vagina, urethra, ear, and nose, or due to injuries caused by falls, puncture wounds, and gunshot wounds. Foreign bodies can be difficult to detect, particularly if they are not inherently radio-opaque, and may be overlooked by patients who cannot provide an adequate history. These foreign bodies may cause harm to the patient. Interpretation is done on radiographs, computed tomography (CT), Ultrasonography (USG), and magnetic resonance imaging (MRI) studies. Most foreign objects pass through the gastrointestinal tract without problem; sharp and elongated objects can cause significant injury, and even if they only partially perforate the bowel wall, they can produce chronic inflammatory processes that produce symptoms months or years later. Hence, searching for foreign bodies should be done throughout the gastrointestinal tract, particularly in children and people with mental illness who are more likely to swallow multiple items more than once. Although rare, various materials can be left behind in the body of a patient after surgery, including large and small wire sutures, surgical drains, and retained sponges, which can cause potential complications and foreign body reactions. This article highlights the importance of being aware of the presence of foreign bodies in clinical practice, and a thorough search should be carried out using different modalities, especially CT. Great suspicion and early diagnosis of foreign bodies can avoid potential complications and morbidity. In general, it provides information on the diagnosis and treatment of various types of foreign bodies.

Characterization and Comparative Investigation of Hydroxyapatite/Carboxymethyl Cellulose (CaHA/CMC) Matrix for Soft Tissue Augmentation in a Rat Model.

This study endeavors to develop an injectable subdermal implant material tailored for soft tissue repair and enhancement. The material consists of a ceramic phase of calcium hydroxyapatite (CaHA), which is biocompatible, 20-60 μm in size, known for its biocompatibility and minimal likelihood of causing foreign body reactions, antigenicity, and minimal inflammatory response, dispersed in a carrier phase composed of carboxymethyl cellulose (CMC), glycerol, and water for injection. The gel formulation underwent comprehensive characterization via various analytical techniques. X-ray diffraction (XRD) was employed to identify crystalline phases and investigate the structural properties of ceramic particles, while thermogravimetric analysis (TGA) was conducted to evaluate the thermal stability and decomposition behavior of the final formulation. Scanning electron microscopy (SEM) was utilized to examine the surface morphology and particle size distribution, confirming the homogeneous dispersion of spherical CaHA particles within the matrix. SEM analysis revealed particle sizes ranging from approximately 20-60 μm. Elemental analysis confirmed a stoichiometric Ca/P ratio of 1.65 in the hydroxyapatite (HA) structure. Heavy metal content exhibited suitability for surgical implant use without posing toxicity risks. Rheological analysis revealed a storage modulus of 58.6 and 68.9 kPa and a loss modulus of 21.7 and 24.8 kPa at the frequencies of 2 and 5 Hz, respectively. 150 μL of sterilized CaHA/CMC was injected subcutaneously into rats and compared with a similar product, Crystalys, to assess its effects on soft tissues. Skin tissue samples of rats were collected at specific intervals throughout the study (30, 45, 60, 90 and 120 days), and examined histologically. Results demonstrated that CaHA/CMC gel led to a significant increase in dermal thickness, elastic fibers, and collagen density. Based on the findings, the formulated CaHA/CMC gel was found to be biocompatible, biodegradable, nonimmunogenic, nontoxic, safe, and effective, and represents a promising option for soft tissue repair and augmentation.

Targeting Macrophage Polarization for Reinstating Homeostasis following Tissue Damage.

Tissue regeneration and remodeling involve many complex stages. Macrophages are critical in maintaining micro-environmental homeostasis by regulating inflammation and orchestrating wound healing. They display high plasticity in response to various stimuli, showing a spectrum of functional phenotypes that vary from M1 (pro-inflammatory) to M2 (anti-inflammatory) macrophages. While transient inflammation is an essential trigger for tissue healing following an injury, sustained inflammation (e.g., in foreign body response to implants, diabetes or inflammatory diseases) can hinder tissue healing and cause tissue damage. Modulating macrophage polarization has emerged as an effective strategy for enhancing immune-mediated tissue regeneration and promoting better integration of implantable materials in the host. This article provides an overview of macrophages' functional properties followed by discussing different strategies for modulating macrophage polarization. Advances in the use of synthetic and natural biomaterials to fabricate immune-modulatory materials are highlighted. This reveals that the development and clinical application of more effective immunomodulatory systems targeting macrophage polarization under pathological conditions will be driven by a detailed understanding of the factors that regulate macrophage polarization and biological function in order to optimize existing methods and generate novel strategies to control cell phenotype.

The Ray Method: Aesthetic and Simple Technique for Prosthesis Coverage in Prepectoral Breast Reconstruction

Summary: In prepectoral breast reconstruction, the acellular dermal matrix (ADM) is commonly used to envelop breast implants. Various wrapping methods have been proposed. We present a simple but aesthetic method (ie, the ray method) for wrapping in prepectoral breast reconstruction. Without any complicated design, we folded the four corners of one large ADM and sewed them together to completely envelop the implant. Then, the 6 o’clock corner of the ADM envelope was folded up and sutured to make a pentagonal shape. The other corners of the ADM envelope were quilted to determine the position and movement of the internal implant. Additional sutures were placed on the ADM envelope to separate the implant from the host tissue. The folded 6 o’clock corner was cut to a convex contour and had a diagonal gap to prevent the collection of fluid in the ADM envelope. Finally, the wrapped implant was inserted in the postmastectomy space, and the ADM envelope was spread widely to support soft tissue effectively. This simple design is straightforward for inexperienced surgeons and reduces operation time. The position and movement of the breast implant in the ADM envelope can be easily controlled by using quilted sutures. Subclavian depression and step-off deformities can be minimized by this wide-stretched ADM. By total coverage with a large ADM, the breast implant is separated from the surrounding tissue, and foreign body reactions are reduced. This method is reliable for maximizing the aesthetic advantages of prepectoral direct-to-implant breast reconstruction.

An elastomer with in situ generated pure zwitterionic surfaces for fibrosis-resistant implants

Polymeric elastomers are widely utilized in implantable biomedical devices. Nevertheless, the implantation of these elastomers can provoke a robust foreign body response (FBR), leading to the rejection of foreign implants and consequently reducing their effectiveness in vivo. Building effective anti-FBR coatings on those implants remains challenging. Herein, we introduce a coating-free elastomer with superior immunocompatibility. A super-hydrophilic anti-fouling zwitterionic layer can be generated in situ on the surface of the elastomer through a simple chemical trigger. This elastomer can repel the adsorption of proteins, as well as the adhesion of cells, platelets, and diverse microbes. The elastomer elicited negligible inflammatory responses after subcutaneous implantation in rodents for 2 weeks. No apparent fibrotic capsule formation was observed surrounding the elastomer after 6 months in rodents. Continuous subcutaneous insulin infusion (CSII) catheters constructed from the elastomer demonstrated prolonged longevity and performance compared to commercial catheters, indicating its great potential for enhancing and extending the performance of various implantable biomedical devices by effectively attenuating local immune responses. Statement of significanceThe foreign body response remains a significant challenge for implants. Complicated coating procedures are usually needed to construct anti-fibrotic coatings on implantable elastomers. Herein, a coating-free elastomer with superior immunocompatibility was achieved using a zwitterionic monomer derivative. A pure zwitterionic layer can be generated on the elastomer surface through a simple chemical trigger. This elastomer significantly reduces protein adsorption, cell and bacterial adhesion, and platelet activation, leading to minimal fibrotic capsule formation even after six months of subcutaneous implantation in rodents. CSII catheters constructed from the PQCBE-H elastomer demonstrated prolonged longevity and performance compared to commercial catheters, highlighting the significant potential of PQCBE-H elastomers for enhancing and extending the performance of various implantable biomedical devices.

Late-Onset Reactions after Hyaluronic Acid Dermal Fillers: A Consensus Recommendation on Etiology, Prevention and Management.

Hyaluronic acid (HA) dermal fillers, generally considered low-risk, can lead to rare late-onset reactions (LORs) manifesting between 3 and 4 months postinjection, occasionally even as early as 24h postinjection. The Complication Assessment and Risk Evaluation (CARE) board was established to review these reactions. In this publication, the authors aims to explore the etiological hypotheses underlying LORs, associated risk factors, prevention, and management approaches suggested by the CARE board. The CARE board identified three etiological hypotheses contributing to LORs. Firstly, the physicochemical structure of the filler, particularly low molecular weight HA, which may trigger an immune response. Secondly, infection, potentially introduced during injection or by dormant biofilm activation. Lastly, an imbalance in the host immune system, caused by factors like autoimmune diseases or viral infections, may lead to extended foreign body reactions, delayed type IV hypersensitivity, or adjuvant-based reactions. Based on these hypotheses, the board categorized various risk factors as patient-related (e.g., recent dental treatment, current medical status, active autoimmune disease), product-related (e.g., molecular weight), and procedure-related (e.g., aseptic technique and trauma). To reduce the risk of LORs, the CARE board recommends diligent patient selection, including comprehensive medical history assessment and informed consent. Practitioners should maintain an effective aseptic technique, and choose an appropriate product and injection depth for the anatomical location. Post-procedure, patients should receive education on proper filler care. Management of LORs depends on the suspected etiology, and the CARE board has proposed an algorithm to determine the most appropriate treatment. Hyaluronidase is recommended for noninflammatory reactions in the absence of active infection, while watchful waiting and/or steroid treatment may be preferred for inflammatory reactions. Hyaluronidase is not recommended as a first-line treatment for infections, which require drainage, bacterial culture, and antibiotic treatment. However, the board emphasizes the need for individualized evaluation and treatment in all cases.

Stretchable Tissue-Like Gold Nanowire Composites with Long-Term Stability for Neural Interfaces.

Soft and stretchable nanocomposites can match the mechanical properties of neural tissue, therebyminimizing foreign body reactions to provide optimal stimulation and recording specificity. Soft materials for neural interfaces should simultaneously fulfill a wide range of requirements, including low Young's modulus (<<1MPa), stretchability (≥30%), high conductivity (>> 1000 Scm-1), biocompatibility, and chronic stability (>> 1 year). Current nanocomposites do not fulfill the above requirements, in particular not the combination of softness and high conductivity. Here, this challenge is addressed by developing a scalable and robust synthesis route based on polymeric reducing agents for smooth, high-aspect ratio gold nanowires (AuNWs) of controllable dimensions with excellent biocompatibility. AuNW-silicone composites show outstanding performance with nerve-like softness (250kPa), high conductivity (16000 Scm-1), and reversible stretchability. Soft multielectrode cuffs based on the composite achieve selective functional stimulation, recordings of sensory stimuli in rat sciatic nerves, and show an accelerated lifetime stability of >3 years. The scalable synthesis method provides a chemically stable alternative to the widely used AgNWs, thereby enabling new applications within electronics, biomedical devices, and electrochemistry.

Low-intensity pulsed ultrasound stimulation (LIPUS) modulates microglial activation following intracortical microelectrode implantation

Microglia are important players in surveillance and repair of the brain. Implanting an electrode into the cortex activates microglia, produces an inflammatory cascade, triggers the foreign body response, and opens the blood-brain barrier. These changes can impede intracortical brain-computer interfaces performance. Using two-photon imaging of implanted microelectrodes, we test the hypothesis that low-intensity pulsed ultrasound stimulation can reduce microglia-mediated neuroinflammation following the implantation of microelectrodes. In the first week of treatment, we found that low-intensity pulsed ultrasound stimulation increased microglia migration speed by 128%, enhanced microglia expansion area by 109%, and a reduction in microglial activation by 17%, indicating improved tissue healing and surveillance. Microglial coverage of the microelectrode was reduced by 50% and astrocytic scarring by 36% resulting in an increase in recording performance at chronic time. The data indicate that low-intensity pulsed ultrasound stimulation helps reduce the foreign body response around chronic intracortical microelectrodes.

A supramolecular bifunctional hydrogel with zero-order release kinetics to resist bacterial infection and foreign body response of implants

A supramolecular bifunctional hydrogel with zero-order release kinetics to resist bacterial infection and foreign body response of implants

Preoperative localization of potentially invisible colonic lesions on the laparoscopic operation field: using autologous blood tattooing.

Preoperative colonoscopic (POC) localization is recommended for patients scheduled for elective laparoscopic colectomy for early colon cancer. Among the various localization method, POC tattooing localization has been widely used. Several dyes have been used for tattooing, but dye has disadvantages, including foreign body reactions. For this reason, we have used autologous blood tattooing for POC localization. This study aimed to evaluate the safety and efficacy of the autologous blood tattooing method. This study included patients who required POC localization of the colonic neoplasm among the patients who were scheduled for elective colon resection. The indication for localization was early colon cancer (clinically T1 or T2) or colonic neoplasms that could not be resected endoscopically. POC autologous blood tattooing was performed after saline injection, and 2 hemoclips were applied. A total of 45 patients who underwent autologous blood tattooing and laparoscopic colectomy were included in this study. All POC localization sites were visible in the laparoscopic view. POC localization sites showed almost perfect agreement with intraoperative surgical findings. There were no complications like bowel perforation, peritonitis, hemoperitoneum, and mesenteric hematoma. Autologous blood is a safe and effective agent for localizing materials that can replace previous dyes. However, a large prospective case-control study is required for the routine application of this procedure in early colon cancer or colonic neoplasms.

Gossypiboma larynx: a rare cause of post-tracheostomy stridor—case report and review of literature

BackgroundGossypiboma, a retained surgical sponge with a foreign body reaction, is an unusual but serious complication seen in open abdominal surgeries. It is exceptionally rare following head and neck surgeries. Here, we present a case of Gossypiboma of the upper airway following tracheostomy.Case presentationA 32-year-old male presented with stridor and difficulty breathing one-month post-tracheostomy after a severe head injury following a road traffic accident. A neck radiograph was unremarkable, and a computed tomography (CT) scan of the neck showed a well-defined homogenous curvilinear membrane extending from the hypopharynx to the upper trachea. Bronchoscopic evaluation of the larynx and upper trachea revealed a retained surgical sponge, which was retrieved. The patient’s breathing improved drastically post intervention.ConclusionGossypiboma may go undetected in radiographs and may also present atypically as a homogenous membrane on a CT scan of the neck. Though rare, retained surgical items can have profound medicolegal and professional consequences on physicians. Hence, a strong clinical suspicion and vigilance for gossypiboma is necessary for patients presenting with respiratory distress post-tracheostomy.

Long-term histological and hemodynamic findings of repairing penile tunica albuginea defects with collagen fleece in dogs.

Clinically, collagen fleece patching of the penile tunica albuginea (TA) has been successful. However, the histopathological and hemodynamic outcomes are not known. We studied in vivo TachoSil® patching in two beagle dogs weighing 16.8 (16.7-16.9) Kg. Bilateral intracavernous pressures (ICP) response to 10 mg papaverine hydrochloride were measured. A full-thickness defect was created on the left side in TA 1 × 0.5 cm, and four transverse incisions 1 cm long were made on the right side, placed 0.5 cm apart, and covered with TachoSil®. Six months later, ICP measurements were repeated, and the penis was excised for histopathology. Grossly, the graft site was indistinguishable. The mean baseline ICP was 19.3 ± 2.98 mmHg and increased after papaverine injection to a mean peak ICP of 122 ± 26.1 mmHg. The ICP measurement before and after grafting did not show a significant difference in the baseline (p = 0.068) or the peak pressure (p = 0.465). Histologically, minimal foreign body reaction was seen, and the TA was completely regenerated. The underlying cavernous tissue did not show inflammation or necrosis. The study is the first to show the long-term histopathologic regeneration of TA after collagen fleece patching while maintaining the hemodynamic response to papaverine.

A Thy-1-negative immunofibroblast population emerges as a key determinant of fibrotic outcomes to biomaterials.

Fibrosis-associated fibroblasts have been identified across various fibrotic disorders, but not in the context of biomaterials, fibrotic encapsulation, and the foreign body response. In other fibrotic disorders, a fibroblast subpopulation defined by Thy-1 loss is strongly correlated with fibrosis yet we do not know what promotes Thy-1 loss. We have previously shown that Thy-1 is an integrin regulator enabling normal fibroblast mechanosensing, and here, leveraging nonfibrotic microporous annealed particle (MAP) hydrogels versus classical fibrotic bulk hydrogels, we demonstrate that Thy1-/- mice mount a fibrotic response to MAP gels that includes inflammatory signaling. We found that a distinct and cryptic α-smooth muscle actin-positive Thy-1- fibroblast population emerges in response to interleuklin-1β (IL-1β) and tumor necrosis factor-α (TNFα). Furthermore, IL-1β/TNFα-induced Thy-1- fibroblasts consist of two distinct subpopulations that are strongly proinflammatory. These findings illustrate the emergence of a unique proinflammatory, profibrotic fibroblast subpopulation that is central to fibrotic encapsulation of biomaterials.

Uniaxial extending neural probes for bleeding-absent implantation

Implantable neural probes, essential for brain electrophysiological research, have advanced with ultra-flexible designs to mitigate immune responses and postoperative complications. Strategies of shuttle-assisted implantation and temporary stiffening address issues in penetrating these probes into the target region, avoiding undesired bending. However, the risk of intraoperative bleeding remains due to these implants’ necessary rigidity during insertion. Here, we describe a neural probe with mechanical compliance accompanying self-implantation along the principal axis in the absence of bleeding. Crucial to the behavior is its anisotropic relaxation, which is dominated by the cross-sectional in-plane deformation inhibition due to interchain interactions between the parallel backbones in the globally aligned polymer system. We observed the ensured upright insertion of the probe into the brain while avoiding angiorrhexis with a two-photon microscope and a high-speed camera. The probes permit electrophysiological studies with minimal foreign body responses and imageological compatibility, underscoring their clinical potential.

The cellular and molecular properties of capsule surrounding silicone implants in humans vary uniquely according to the tissue type adjacent to the implant.

The foreign body reaction (FBR) to biomaterials results in fibrous encapsulation. Excessive capsule fibrosis (capsular contracture) is a major challenge to the long-term stability of implants. Clinical data suggests that the tissue type in contact with silicone breast implants alters susceptibility to developing capsular contracture; however, the tissue-specific inflammatory and fibrotic characteristics of capsule have not been well characterized at the cellular and molecular level. In this study, 60 breast implant capsule samples are collected from patients and stratified by the adjacent tissue type including subcutaneous tissue, glandular breast tissue, or muscle tissue. Capsule thickness, collagen organization, immune and fibrotic cellular populations, and expression of inflammatory and fibrotic markers is quantified with histological staining, immunohistochemistry, and real-time PCR. The findings suggest there are significant differences in M1-like macrophages, CD4+ T cells, CD26+ fibroblasts, and expression of IL-1β, IL-6, TGF-β, and collagen type 1 depending on the tissue type abutting the implant. Subglandular breast implant capsule displays a significant increase in inflammatory and fibrotic markers. These findings suggest that the tissue microenvironment contributes uniquely to the FBR. This data could provide new avenues for research and clinical applications to improve the site-specific biocompatibility and longevity of implantable devices.

Assessment of tissue response in vivo: PET-CT imaging of titanium and biodegradable magnesium implants

To study in vivo the bioactivity of biodegradable magnesium implants and other possible biomaterials, we are proposing a previously unexplored application of PET-CT imaging, using available tracers to follow soft tissue and bone remodelling and immune response in the presence of orthopaedic implants. Female Wistar rats received either implants (Ti6Al7Nb titanium or WE43 magnesium) or corresponding transcortical sham defects into the diaphyseal area of the femurs. Inflammatory response was followed with [18F]FDG and osteogenesis with [18F]NaF, over the period of 1.5 months after surgery. An additional pilot study with [68Ga]NODAGA-RGD tracer specific to αvβ3 integrin expression was performed to follow the angiogenesis for one month.[18F]FDG tracer uptake peaked on day 3 before declining in all groups, with Mg and Ti groups exhibiting overall higher uptake compared to sham. This suggests increased cellular activity and tissue response in the presence of Mg during the initial weeks, with Ti showing a subsequent increase in tracer uptake on day 45, indicating a foreign body reaction. [18F]NaF uptake demonstrated the superior osteogenic potential of Mg compared to Ti, with peak uptake on day 7 for all groups. [68Ga]NODAGA-RGD pilot study revealed differences in tracer uptake trends between groups, particularly the prolonged expression of αvβ3 integrin in the presence of implants.Based on the observed differences in the uptake trends of radiotracers depending on implant material, we suggest that PET-CT is a suitable modality for long-term in vivo assessment of orthopaedic biomaterial biocompatibility and underlying tissue reactions. Statement of significanceThe study explores the novel use of positron emission tomography for the assessment of the influence that biomaterials have on the surrounding tissues. Previous related studies have mostly focused on material-related effects such as implant-associated infections or to follow the osseointegration in prosthetics, but the use of PET to evaluate the materials has not been reported before. The approach tests the feasibility of using repeated PET-CT imaging to follow the tissue response over time, potentially improving the methodology for adopting new biomaterials for clinical use.

Engineered Graphene Material Improves the Performance of Intraneural Peripheral Nerve Electrodes.

Limb neuroprostheses aim to restore motor and sensory functions in amputated or severely nerve-injured patients. These devices use neural interfaces to record and stimulate nerve action potentials, creating a bidirectional connection with the nervous system. Most neural interfaces are based on standard metal microelectrodes. In this work, a new generation of neural interfaces which replaces metals with engineered graphene, called EGNITE, is tested. In vitro and in vivo experiments are conducted to assess EGNITE biocompatibility. In vitro tests show that EGNITE does not impact cell viability. In vivo, no significant functional decrease or harmful effects are observed. Furthermore, the foreign body reaction to the intraneural implant is similar compared to other materials previously used in neural interfaces. Regarding functionality, EGNITE devices are able to stimulate nerve fascicles, during two months of implant, producing selective muscle activation with about three times less current compared to larger microelectrodes of standard materials. CNAP elicited by electrical stimuli and ENG evoked by mechanical stimuli are recorded with high resolution but are more affected by decreased functionality over time. This work constitutes further proof that graphene-derived materials, and specifically EGNITE, is a promising conductive material of neural electrodes for advanced neuroprostheses.

Immune system triggers as a factor for the formation of foreign body granuloma after hyaluronic acid fillers treatment.

Immune system triggers as a factor for the formation of foreign body granuloma after hyaluronic acid fillers treatment.