Foreign Body Giant Cell Formation Research Articles

Mir-146a is required for foreign body response and giant cell formation

The implantation of biomaterials or medical devices often leads to the development of a foreign body response (FBR), an inflammatory condition that can lead to implant failure, which may cause harm to or death of the patient. Hallmarks of the FBR include accumulation of macrophages and destructive foreign body giant cells (FBGCs), and development of fibrous scar tissue encompassing the implant. There are no effective medical treatments for FBR, although improved fundamental understanding of the molecular mechanisms underlying the development of FBR may lead to novel strategies for the amelioration of FBR. MicroRNAs (miRs) are endogenous, small, non-coding RNAs that have emerged as powerful regulators of gene expression in numerous cellular processes including macrophage activation, inflammation, and fibrosis. In this research, we tested the hypothesis that specific miRs play a crucial role in regulating the FBR to biomaterials. In our subcutaneous implantation mouse model, we found that: 1) miR-146a expression levels decreased in the implant-adhered tissues, and the decrease correlated with increased macrophage accumulation, FBGC formation, and collagen accumulation; and 2) miR-146a deletion in mice exacerbated in vivo macrophage accumulation, FBGC formation, and collagen accumulation. In our in vitro model, we found that deficiency of miR-146a function exacerbated key macrophage functions including adhesion on stiff matrix, and FBGC formation in primary mouse macrophages. In essence, our findings suggest that miR-146a might act as a suppressor of FBR. We expect that the results of this study may provide invaluable information and insight regarding the molecular mechanisms mediating the FBR to biomaterials, which may lead to the development of a novel microRNA-based therapeutic strategy for the amelioration of the poorly understood FBR to biomaterials. NIH (R01 AI172086) grant to Shaik O. Rahaman. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Implant-Induced Foreign Body Response Is Limited by CD13-Dependent Regulation of Ubiquitination of Fusogenic Proteins.

Implanted medical devices, from artificial heart valves and arthroscopic joints to implantable sensors, often induce a foreign body response (FBR), a form of chronic inflammation resulting from the inflammatory reaction to a persistent foreign stimulus. The FBR is characterized by a subset of multinucleated giant cells (MGCs) formed by macrophage fusion, the foreign body giant cells (FBGCs), accompanied by inflammatory cytokines, matrix deposition, and eventually deleterious fibrotic implant encapsulation. Despite efforts to improve biocompatibility, implant-induced FBR persists, compromising the utility of devices and making efforts to control the FBR imperative for long-term function. Controlling macrophage fusion in FBGC formation presents a logical target to prevent implant failure, but the actual contribution of FBGCs to FBR-induced damage is controversial. CD13 is a molecular scaffold, and invitro induction of CD13KO bone marrow progenitors generates many more MGCs than the wild type, suggesting that CD13 regulates macrophage fusion. In the mesh implant model of FBR, CD13KO mice produced significantly more peri-implant FBGCs with enhanced TGF-β expression and increased collagen deposition versus the wild type. Prior to fusion, increased protrusion and microprotrusion formation accompanies hyperfusion in the absence of CD13. Expression of fusogenic proteins driving cell-cell fusion was aberrantly sustained at high levels in CD13KO MGCs, which we show is due to a novel CD13 function, to our knowledge, regulating ubiquitin/proteasomal protein degradation. We propose CD13 as a physiologic brake limiting aberrant macrophage fusion and the FBR, and it may be a novel therapeutic target to improve the success of implanted medical devices. Furthermore, our data directly implicate FBGCs in the detrimental fibrosis that characterizes the FBR.

Identification of a humanized mouse model for functional testing of immune-mediated biomaterial foreign body response.

Biomedical devices comprise a major component of modern medicine, however immune-mediated fibrosis and rejection can limit their function over time. Here, we describe a humanized mouse model that recapitulates fibrosis following biomaterial implantation. Cellular and cytokine responses to multiple biomaterials were evaluated across different implant sites. Human innate immune macrophages were verified as essential to biomaterial rejection in this model and were capable of cross-talk with mouse fibroblasts for collagen matrix deposition. Cytokine and cytokine receptor array analysis confirmed core signaling in the fibrotic cascade. Foreign body giant cell formation, often unobserved in mice, was also prominent. Last, high-resolution microscopy coupled with multiplexed antibody capture digital profiling analysis supplied spatial resolution of rejection responses. This model enables the study of human immune cell-mediated fibrosis and interactions with implanted biomaterials and devices.

Mechanisms of Foreign Body Giant Cell Formation in Response to Implantable Biomaterials

Long term function of implantable biomaterials are determined by their integration with the host's body. Immune reactions against these implants could impair the function and integration of the implants. Some biomaterial-based implants lead to macrophage fusion and the formation of multinucleated giant cells, also known as foreign body giant cells (FBGCs). FBGCs may compromise the biomaterial performance and may lead to implant rejection and adverse events in some cases. Despite their critical role in response to implants, there is a limited understanding of cellular and molecular mechanisms involved in forming FBGCs. Here, we focused on better understanding the steps and mechanisms triggering macrophage fusion and FBGCs formation, specifically in response to biomaterials. These steps included macrophage adhesion to the biomaterial surface, fusion competency, mechanosensing and mechanotransduction-mediated migration, and the final fusion. We also described some of the key biomarkers and biomolecules involved in these steps. Understanding these steps on a molecular level would lead to enhance biomaterials design and improve their function in the context of cell transplantation, tissue engineering, and drug delivery.

Biodegradation of HA and β-TCP Ceramics Regulated by T-Cells.

Biodegradability is one of the most important properties of implantable bone biomaterials, which is directly related to material bioactivity and the osteogenic effect. How foreign body giant cells (FBGC) involved in the biodegradation of bone biomaterials are regulated by the immune system is poorly understood. Hence, this study found that β-tricalcium phosphate (β-TCP) induced more FBGCs formation in the microenvironment (p = 0.0061) accompanied by more TNFα (p = 0.0014), IFNγ (p = 0.0024), and T-cells (p = 0.0029) than hydroxyapatite (HA), resulting in better biodegradability. The final use of T-cell depletion in mice confirmed that T-cell-mediated immune responses play a decisive role in the formation of FBGCs and promote bioceramic biodegradation. This study reveals the biological mechanism of in vivo biodegradation of implantable bone tissue engineering materials from the perspective of material-immune system interaction, which complements the mechanism of T-cells’ adaptive immunity in bone immune regulation and can be used as a theoretical basis for rational optimization of implantable material properties.

Immunological reaction to magnesium-based implants for orthopedic applications. What do we know so far? A systematic review on in vivo studies.

Magnesium-based implants (Mg) became an attractive candidate in orthopedic surgery due to their valuable properties, such as osteoconductivity, biodegradability, elasticity and mechanical strength. However, previous studies on biodegradable and non-biodegradable metal implants showed that these materials are not inert when placed in vivo as they interact with host defensive mechanisms. The aim of this study was to systematically review available in vivo studies with Mg-based implants that investigated immunological reactions to these implants. The following questions were raised: Do different types of Mg-based implants in terms of shape, size and alloying system cause different extent of immune response? and; Are there missing links to properly understand immunological reactions upon implantation and degradation of Mg-based implants? The database used for the literature research was PubMed (U.S. National Library of Medicine) and it was undertaken in the end of 2021. The inclusion criteria comprised (i) in vivo studies with bony implantation of Mg-based implants and (ii) analysis of the presence of local immune cells or systemic inflammatory parameters. We further excluded any studies involving coated Mg-implants, in vitro studies, and studies in which the implants had no bone contact. The systematic search process was conducted according to PRISMA guidelines. Initially, the search yielded 225 original articles. After reading each article, and based on the inclusion and exclusion criteria, 16 articles were included in the systematic review. In the available studies, Mg-based implants were not found to cause any severe inflammatory reaction, and only a mild to moderate inflammatory potential was attributed to the material. The timeline of foreign body giant cell formation showed to be different between the reviewed studies. The variety of degradation kinetics of different tested implants and discrepancies in studies regarding the time points of immunological investigations impair the conclusion of immunological reactions. This may be induced by different physical properties of an implant such as size, shape and alloying system. Further research is essential to elucidate the underlying mechanisms by which implant degradation affects the immune system. Also, better understanding will facilitate the decision of patients whether to undergo surgery with new device implantation.

Antimicrobial and Anti-inflammatory Gallium-Defensin Surface Coatings for Implantable Devices.

Emerging and re-emerging infections are a global threat driven by the development of antimicrobial resistance due to overuse of antimicrobial agents and poor infection control practices. Implantable devices are particularly susceptible to such infections due to the formation of microbial biofilms. Furthermore, the introduction of implants into the body often results in inflammation and foreign body reactions. The antimicrobial and anti-inflammatory properties of gallium (Ga) have been recognized but not yet utilized effectively to improve implantable device integration. Furthermore, defensin (De, hBD-1) has potent antimicrobial activity in vivo as part of the innate immune system; however, this has not been demonstrated as successfully when used in vitro. Here, we combined Ga and De to impart antimicrobial activity and anti-inflammatory properties to polymer-based implantable devices. We fabricated polylactic acid films, which were modified using Ga implantation and subsequently functionalized with De. Ga-ion implantation increased surface roughness and increased stiffness. Ga implantation and defensin immobilization both independently and synergistically introduced antimicrobial activity to the surfaces, significantly reducing total live bacterial biomass. We demonstrated, for the first time, that the antimicrobial effects of De were unlocked by its surface immobilization. Ga implantation of the surface also resulted in reduced foreign body giant cell formation and expression of proinflammatory cytokine IL-1β. Cumulatively, the treated surfaces were able to kill bacteria and reduce inflammation in comparison to the untreated control. These innovative surfaces have the potential to prevent biofilm formation without inducing cellular toxicity or inflammation, which is highly desired for implantable device integration.

Mechanosensing by TRPV4 mediates stiffness-induced foreign body response and giant cell formation.

Implantation of biomaterials or devices into soft tissue often leads to the development of the foreign body response (FBR), an inflammatory condition that can cause implant failure, tissue injury, and death of the patient. Macrophages accumulate and fuse to generate destructive foreign body giant cells (FBGCs) at the tissue-implant interface, leading to the development of fibrous scar tissue around the implant that is generated by myofibroblasts. We previously showed that the FBR in vivo and FBGC formation in vitro require transient receptor potential vanilloid 4 (TRPV4), a mechanosensitive ion channel. Here, we report that TRPV4 was required specifically for the FBR induced by implant stiffness independently of biochemical cues and for intracellular stiffening that promotes FBGC formation in vitro. TRPV4 deficiency reduced collagen deposition and the accumulation of macrophages, FBGCs, and myofibroblasts at stiff, but not soft, implants in vivo and inhibited macrophage-induced differentiation of wild-type fibroblasts into myofibroblasts in vitro. Atomic force microscopy demonstrated that TRPV4 was required for implant-adjacent tissue stiffening in vivo and for cytoskeletal remodeling and intracellular stiffening induced by fusogenic cytokines in vitro. Together, these data suggest a mechanism whereby a reciprocal functional interaction between TRPV4 and substrate stiffness leads to cytoskeletal remodeling and cellular force generation to promote FBGC formation during the FBR.

Morphological Features of Foreign Body Giant Cells in Experimental Conditions

Background: The purpose of our work was determined by the accumulation of a significant amount of experimental material under the conditions of implantation of a foreign body, a mesh implant, into the region of the anterior abdominal wall in order to obtain experimental inflammation, in which foreign body giant cells (FBGCs) were constantly visualized as reactive formations. This research aimed to study the dynamics of morphological changes in FBGCs under conditions of experimental implantation of a foreign body, a mesh implant, and the possible mechanism of their formation Methods and Results: This study was carried out on male Wistar rats, in which a foreign body was implanted—a mesh endoprosthesis made of polypropylene—in the region of the anterior abdominal wall under the aponeurosis of the rectus abdominis muscles. A section of the anterior abdominal wall with the implanted endoprosthesis was excised on Days 10, 21, 30, and 60 after surgery, fixed in 10% buffered formalin solution. The obtained samples were embedded in paraffin according to standard prescriptions; histological sections with a thickness of 5-7µm were made and stained with H&E, according to the methods of Van Gieson and Mallory, and an immunohistochemical study was performed using the marker of cell proliferation (Ki-67). The revealed structural features of multinucleated cells were recorded by microphotography using a photo attachment and a Levenhuk video camera (USA). During the study, it was revealed that the amount, functional activity and morphological diversity of FBGCs gradually increased, reaching a maximum by Day 30 of the experiment. At a later date, some of them died, while the remaining part was differentiated, splitting into small multinucleated cells and mononuclear elements, morphologically identical to macrophages and fibroblasts. The formation of FBGCs continued as long as the mesh implant was in the body. Conclusion: FBGCs are reactive formations that arise in response to various endo- and exogenous irritation.

Cholesterol granuloma of the maxillary sinus: a forgotten entity

Aim of the study: Cholesterol granuloma is a histological entity which consists of granulation tissue in which a large quantity of cholesterol crystals provoke foreign body giant cell formation. Cholesterol granulomas are often found in the middle ear with rare presentation in the paranasal sinus. We would like to highlight the diagnostic challenges and the management of maxillary sinus cholesterol granuloma in a young woman presenting as a unilateral nasal mass. Case study: We report a young woman with cholesterol granuloma of maxillary sinus who initially presented with unilateral nasal obstruction. Rigid nasoendoscopy and imaging were suggestive of an antrochoanal polyp. Ipsilateral functional endoscopic sinus surgery was done successfully. Conclusion: Albeit rare, cholesterol granuloma ought to be considered a differential diagnosis in a sinonasal tumour. This case report highlights the rare presentation of maxillary sinus cholesterol granuloma which ought to be considered a differential diagnosis of a unilateral nasal mass.

Effects of Cyanoacrylate in Rabbits with Induced Achilles Tendon Rupture.

BackgroundIn this study, we aimed to investigate the effects of N-butyl-2-cyanoacrylate (cyanoacrylate) on the biomechanical and histopathological aspects of tendon healing in a rabbit model of Achilles tendon injury.Material/MethodsIn total, 36 rabbits were randomized to experimental (cyanoacrylate) and control groups (n=36 tendons in each group). A simple suture was used in the control group and a simple suture plus cyanoacrylate was used in the experimental group.Nine rabbits from each group were euthanized at week 4 and week 6 after surgery for histopathological and biomechanical testing.ResultsGranulation tissue formation was significantly greater in the experimental group in week 4 and week 6 than in the control group. Foreign body giant cell formation was significantly higher in the experimental group in week 4 and week 6. The maximum rupture force was significantly higher in the experimental group in week 4 and week 6 than in the control group. Elasticity and stiffness were comparable between groups in week 4; however, stiffness, but not elasticity, was significantly higher in the experimental group in week 6.ConclusionsIn the short term, cyanoacrylate enhanced tendon endurance in both a histopathological and biomechanical manner. We conclude that the early initiation of rehabilitation in patients may be safe in cases of cyanoacrylate use for surgical repair of tendon injury.

Mechanotransduction via a TRPV4-Rac1 signaling axis plays a role in multinucleated giant cell formation

Multinucleated giant cells are formed by the fusion of macrophages and are a characteristic feature in numerous pathophysiological conditions including the foreign body response (FBR). Foreign body giant cells (FBGCs) are inflammatory and destructive multinucleated macrophages and may cause damage and/or rejection of implants. However, while these features of FBGCs are well established, the molecular mechanisms underlying their formation remain elusive. Improved understanding of the molecular mechanisms underlying the formation of FBGCs may permit the development of novel implants that eliminate or reduce the FBR. Our previous study showed that transient receptor potential vanilloid 4 (TRPV4), a mechanosensitive ion channel/receptor, is required for FBGC formation and FBR to biomaterials. Here, we have determined that (a) TRPV4 is directly involved in fusogenic cytokine (interleukin-4 plus granulocyte macrophage–colony stimulating factor)–induced activation of Rac1, in bone marrow–derived macrophages; (b) TRPV4 directly interacts with Rac1, and their interaction is further augmented in the presence of fusogenic cytokines; (c) TRPV4-dependent activation of Rac1 is essential for the augmentation of intracellular stiffness and regulation of cytoskeletal remodeling; and (d) TRPV4-Rac1 signaling axis is critical in fusogenic cytokine–induced FBGC formation. Together, these data suggest a novel mechanism whereby a functional interaction between TRPV4 and Rac1 leads to cytoskeletal remodeling and intracellular stiffness generation to modulate FBGC formation.

Tuning the immune reaction to manipulate the cell-mediated degradation of a collagen barrier membrane

In order to elicit a desired barrier function in guided bone regeneration (GBR) or guided tissue regeneration (GTR), a barrier membrane has to maintain its integrity for a certain period of time to guarantee the regeneration of target tissue. Due to the complexity and variety of clinical conditions, the healing time required for tissue regeneration varies from one case to another, which implies the need for tailoring the barrier membranes to diverse conditions via manipulating their degradation property. As a “non-self” biomaterial, a barrier membrane will inevitably trigger host-membrane immune response after implantation, which entails the activation of phagocytic cells. In the degradation process of a barrier membrane, the cell-mediated degradation may play a more vital role than enzymatic and physicochemical dissolution; however, limited studies have been carried out on this topic. In this context, we investigated the cell-mediated degradation and illustrated the possible key cells and mediators for immunomodulation via in vivo and in vitro studies. We discovered that IL-13, a key cytokine mainly released by T helper 2 cells (Th2), induced the formation of foreign body giant cells (FBGCs), thus resulting in membrane degradation. Neutralizing IL-13 could suppress membrane degradation and formation of FBGC. The contributions of this study are (1) unveiling the immune mechanisms underlying the cell-mediated collagen membrane degradation; (2) allowing the formation of an “immunodegradation” strategy to develop an “immune-smart” barrier membrane to manipulate its degradation; (3) providing the key regulatory immune cells and cytokines for the immunomodulation target in collagen membrane degradation. Statement of SignificanceThe significance of this research includes:(1)Unveiling the immune mechanisms underlying the cell-mediated collagen membrane degradation;(2)Allowing the formation of an “immunodegradation” strategy to develop an “immune-smart” barrier membrane to manipulate its degradation;(3)Providing the key regulatory immune cells and cytokines for the immunomodulation target in collagen membrane degradation, which may allow accurate and customized modulation during tissue/bone regenerative process.

Role of TRPV4 mechanosensing in foreign body response and giant cell formation

Implantable biomaterials and medical devices are used in millions of procedures each year worldwide. However, the implantation of these devices leads to the development of a foreign body response (FBR), a chronic inflammatory condition that can ultimately lead to implant failure, which may cause harm to or death of the patient. Despite decades of research, the mechanisms underlying the FBR remain poorly understood, as neither the materials from which these implants are made nor their chemical properties can explain triggering of the FBR. Hallmarks of the FBR include activation of macrophages at the tissue‐implant interface, formation of destructive foreign body giant cells (FBGCs), and development of fibrous tissue that encapsulates the implant. Here, we report that genetic ablation of TRPV4, an ion channel in the transient receptor potential vanilloid family, and which is a mechanosensor, is possibly the mediator of FBR. Specifically, we found that: 1) Trpv4 deletion in mice prevented macrophage accumulation, FBGC formation, and collagen accumulation in a subcutaneous implantation model; 2) the severity of the in vivo macrophage accumulation at the tissue‐implant interface was dependent on the stiffness of the implant; 3) genetic ablation of TRPV4 blocked macrophage adhesion and spreading on stiff matrix in bone marrow derived macrophages; and 4) genetic deficiency of TRPV4 blocked cytokine‐induced FBGC formation, which was restored by lentivirus‐mediated TRPV4 reintroduction. Furthermore, we found that: 5) TRPV4 activity (calcium influx) was augmented in response to a biomechanical stimulus; and 6) loss of TRPV4 activity reduced internal stiffness in macrophages as determined by Atomic Force Microscopy analysis. Taken together, these results suggest an important, previously unknown role for TRPV4 in FBR and giant cell formation.Support or Funding InformationFunding: This work was supported by NIH (1R01EB024556‐01) and NSF (CMMI‐1662776) grants to Shaik O. Rahaman.

Functional supramolecular bioactivated electrospun mesh improves tissue ingrowth in experimental abdominal wall reconstruction in rats

Development of biomaterials for hernia and pelvic organ prolapse (POP) repair is encouraged because of high local complication rates with current materials. Therefore, we aimed to develop a functionalized electrospun mesh that promotes tissue ingrowth and provides adequate mechanical strength and compliance during degradation. We describe the in vivo function of a new supramolecular bioactivated polycarbonate (PC) material based on fourfold hydrogen bonding ureidopyrimidinone (UPy) units (UPy-PC). The UPy-PC material was functionalized with UPy-modified cyclic arginine-glycine-aspartic acid (cRGD) peptide additives. Morphometric analysis of the musculofascial content during wound healing showed that cRGD functionalization promotes myogenesis with inhibition of collagen deposition at 14 days. It also prevents muscle atrophy at 90 days and exerts an immunomodulatory effect on infiltrating macrophages at 14 days and foreign body giant cell formation at 14 and 90 days. Additionally, the bioactivated material promotes neovascularization and connective tissue ingrowth. Supramolecular cRGD-bioactivation of UPy-PC-meshes promotes integration of the implant, accelerates tissue ingrowth and reduces scar formation, resulting in physiological neotissue formation when used for abdominal wall reconstruction in the rat hernia model. Moreover, cRGD-bioactivation prevents muscle atrophy and modulates the inflammatory response. Our results provide a promising outlook towards a new type of biomaterial for the treatment of hernia and POP. Statement of SignificanceDevelopment of biomaterials for hernia and pelvic organ prolapse (POP) repair is encouraged because of high local complication rates with current materials. Ureidopyrimidinone-polycarbonate is a elastomeric and biodegradable electrospun mesh, which could mimic physiological compliance. The UPy-PC material was functionalized with UPy-modified cyclic arginine-glycine-aspartic acid (cRGD) peptide additives. Supramolecular cRGD-bioactivation of UPy-PC-meshes promotes integration of the implant, accelerates tissue ingrowth and reduces scar formation, resulting in physiological neotissue formation when used for abdominal wall reconstruction in rat hernia model. Moreover, cRGD-bioactivation prevents muscle atrophy and modulates the inflammatory response. These data provide a promising outlook towards a new type of biomaterial for the treatment of hernia and POP.

Prostaglandin E2 and Its Receptor EP2 Modulate Macrophage Activation and Fusion in Vitro.

The foreign body response (FBR) has impaired progress of new implantable medical devices through its hallmark of chronic inflammation and foreign body giant cell (FBGC) formation leading to fibrous encapsulation. Macrophages are known to drive the FBR, but efforts to control macrophage polarization remain challenging. The goal for this study was to investigate whether prostaglandin E2 (PGE2), and specifically its receptors EP2 and/or EP4, attenuate classically activated (i.e., inflammatory) macrophages and macrophage fusion into FBGCs in vitro. Lipopolysaccharide (LPS)-stimulated macrophages exhibited a dose-dependent decrease in gene expression and protein production of tumor necrosis factor alpha (TNF-α) when treated with PGE2. This attenuation was primarily by the EP4 receptor, as the addition of the EP2 antagonist PF 04418948 to PGE2-treated LPS-stimulated cells did not recover TNF-α production while the EP4 antagonist ONO AE3 208 did. However, direct stimulation of EP2 with the agonist butaprost to LPS-stimulated macrophages resulted in a ∼60% decrease in TNF-α secretion after 4 h and corresponded with an increase in gene expression for Cebpb and Il10, suggesting a polarization shift toward alternative activation through EP2 alone. Further, fusion of macrophages into FBGCs induced by interleukin-4 (IL-4) and granulocyte-macrophage colony-stimulating factor (GM-CSF) was inhibited by PGE2 via EP2 signaling and by an EP2 agonist, but not an EP4 agonist. The attenuation by PGE2 was confirmed to be primarily by the EP2 receptor. Mrc1, Dcstamp, and Retlna expressions increased upon IL-4/GM-CSF stimulation, but only Retnla expression with the EP2 agonist returned to levels that were not different from controls. This study identified that PGE2 attenuates classically activated macrophages and macrophage fusion through distinct EP receptors, while targeting EP2 is able to attenuate both. In summary, this study identified EP2 as a potential therapeutic target for reducing the FBR to biomaterials.

Evaluation of a Chitosan Hemostat in a Porcine Laparoscopic Partial Nephrectomy Model: A Pilot Study.

Background and Objective: The ideal hemostatic agent for laparoscopic partial nephrectomy (LPN) would provide complete hemostasis and sealing of the collecting system at a low cost. Chitosan (CS) is an established topical hemostatic agent, but standard sterilization techniques affect its functional and biologic properties, thereby preventing parenteral uses. This study sought to characterize the safety and efficacy of an implanted CS hemostat sterilized with either a standard technique, electron beam (e-beam) irradiation, or a novel technique, nonthermal nitrogen plasma, in a porcine LPN model. Methods: Laparoscopic partial nephrectomies were performed on six farm pigs and hemostasis achieved using only a CS hemostatic agent (Clo-Sur P.A.D.) that was e-beam (n = 3) or plasma sterilized (PS) (n = 3). Number of pads needed to achieve hemostasis, estimated blood loss, operative time, mass of kidney resection, and warm ischemia time were measured. Animals were monitored for 14 weeks and at harvest, retrograde ureteropyelography and histologic analysis were performed. Results: Complete hemostasis and collection system sealing were achieved in both groups. There was a trend toward less pads required for hemostasis (p = 0.056) and reduced blood loss (p = 0.096) with PS pads, although this did not achieve statistical significance. No complications were observed for 14 weeks and gross examination showed the implanted CS was encapsulated in a fibrous capsule. Histologic analysis revealed a healed nephrectomy site with residual CS and associated chronic inflammation, reactive fibrosis, and foreign body giant cell formation. Importantly, the adjacent renal tissue was intact and viable with no residual parenchymal inflammation or cytologic damage. Conclusion: CS pads alone provided safe and effective hemostasis in a porcine LPN model. PS may enhance hemostatic efficacy and resorption compared with e-beam.

Anti-inflammatory Surface Coatings Based on Polyelectrolyte Multilayers of Heparin and Polycationic Nanoparticles of Naproxen-Bearing Polymeric Drugs.

Immune response to biomaterials can produce chronic inflammation and fibrosis leading to implant failure, which is related to the surface properties of the biomaterials. This work describes the preparation and characterization of polyelectrolyte multilayer (PEM) coatings that combine the anti-inflammatory activity of heparin as polyanion with the potential release of Naproxen, a nonsteroidal anti-inflammatory drug from polymeric nanoparticles (NP) with cationic surface charge. The polyelectrolyte multilayers were characterized by physical methods to estimate multilayer growth, thickness, zeta potential, and topography. It was found that multilayers with NP had negative zeta potentials and expressed a viscoelastic behavior, while studies of topography showed that nanoparticles formed continuous surface coatings. THP-1-derived macrophages were used to study short-term anti-inflammatory activity (time scale 48 h), showing that PEM that contained heparin reduced cell adhesion and IL1-β secretion, when compared to those with polystyrenesulfonate, used as alternative polyanion in multilayer formation. On the other hand, the presence of NP in PEM was related to a reduced foreign body giant cell formation after 15 days, when compared to PEM that contained chitosan as alternative polycation, which suggests a long-term anti-inflammatory effect of Naproxen-containing nanoparticles. It was also shown that macrophages were able to take up NP from multilayers, which indicates a release of Naproxen by digestion of NP in the lysosomal compartment. These findings indicate that surface coatings composed of heparin and Naproxen-based NP on implants such as biosensors have the potential to attenuate foreign body reaction after implantation, which may improve the long-term functionality of implants.

P4. Autologous blood coagulum as a native carrier for rhBMP6 induces new bone formation and posterolateral lumbar spine fusion in rabbits and sheep

BACKGROUND CONTEXT RhBMP2 soaked in bovine tendon collagen and synthetic ceramics composite as well as rhBMP7/OP1 lyophilized in bovine bone collagen particles with additive carboxyl-methyl cellulose have been evaluated for posterolateral lumbar fusion (PLF). We investigated rhBMP6 delivered in autologous blood coagulum (ABC), a native carrier (scaffold), with and without allograft bone particles (ALLO) to induce new bone formation and promote posterolateral lumbar spine fusion (PLF) in rabbit and sheep. PURPOSE To evaluate the efficacy of RhBMP6 with autologous blood coagulum (ABC) alone or with ABC and allograft (ALLO) will induce a successful posterolateral spinal fusion in animal models. STUDY DESIGN/SETTING Preclinical evaluation of spine fusion in animal models. PATIENT SAMPLE Multiple experimental groups of rats, rabbits and sheep. OUTCOME MEASURES Radiographic and histologic evaluation for bone formation and spinal fusion. METHODS An autologous bone graft substitute (ABGS) was fabricated by dispersing rhBMP6 in ABC with and without ALLO and evaluated for bone induction in rat subcutaneous implants and to promote bone formation in posterolateral lumbar fusion in preclinical models. The cellular response of bone induction and the quantity and quality of newly formed bone were examined by histology, radiographs, micro-CT analyses at various time intervals. RESULTS ABGS with and without ALLO induced new bone formation in rat implants. ALLO alone induced formation of multinucleated foreign body giant cells (FBGCs). However, ALLO plus ABC decreased the formation of FBGCs. The addition of rhBMP6 to ABC/ALLO, resulted in fewer or no FBGCs. In Rabbits, the groups with ABC alone or with ALLO did not fuse. The 50 micrograms rhBMP6 group only 2 out of 4 animals successfully fused. In the 100 micrograms, 200 micrograms and 400 micrograms rhBMP6 groups all animals successfully fused. In sheep, the groups with ABC or ABC with ALLO failed to fuse. In the rhBMP6 187.5 micro grams/ml group with ABC and instrumentation fusion was achieved in 83% (10/12 animals). In the 187.5 micro grams/ml group with ABC, ALLO and instrumentation, fusion was achieved in 93% (11/12 animals). Bone formation occurred uniformly within ABGS implants where the ALLO was replaced by the newly formed bone via creeping substitution. CONCLUSIONS RhBMP6 with autologous blood coagulum (ABC) alone or with ABC and allograft (ALLO) induced a robust bone formation in posterolateral spinal fusion in preclinical models. FDA DEVICE/DRUG STATUS RhBMP6 (Not approved for this indication).

Role of the captured retroviral envelope syncytin-B gene in the fusion of osteoclast and giant cell precursors and in bone resorption, analyzed ex vivo and in vivo in syncytin-B knockout mice

Syncytin-A and -B are envelope genes of retroviral origin that have been captured in evolution for a role in placentation. They trigger cell-cell fusion and were shown to be essential for the formation of the syncytiotrophoblast layer during mouse placenta formation. Syncytin-A and -B expression has been described in other tissues and their highly fusogenic properties suggested that they might be involved in the fusion of other cell types. Here, taking advantage of mice knocked out for syncytin-B, SynB−/− mice, we investigated the potential role of syncytin-B in the fusion of cells from the monocyte/macrophage lineage into multinucleated osteoclasts (OCs) -in bone- or multinucleated giant cells -in soft tissues. In ex vivo experiments, a significant reduction in fusion index and in the number of multinucleated OCs and giant cells was observed as soon as Day3 in SynB−/− as compared to wild-type cell cultures. Interestingly, the number of nuclei per multinucleated OC or giant cell remained unchanged. These results, together with the demonstration that syncytin-B expression is maximal in the first 2 days of OC differentiation, argue for syncytin-B playing a role in the fusion of OC and giant cell mononucleated precursors, at initial stages. Finally, ex vivo, the observed reduction in multinucleated OC number had no impact on the expression of OC differentiation markers, and a dentin resorption assay did not evidence any difference in the osteoclastic resorption activity, suggesting that syncytin-B is not required for OC activity. In vivo, syncytin-B was found to be expressed in the periosteum of embryos at embryonic day 16.5, where TRAP-positive cells were observed. Yet, in adults, no significant reduction in OC number or alteration in bone phenotype was observed in SynB−/− mice. In addition, SynB−/− mice did not show any change in the number of foreign body giant cells (FBGCs) that formed in response to implantation of foreign material, as compared to wild-type mice. Altogether the results suggest that in addition to its essential role in placenta formation, syncytin-B plays a role in OCs and macrophage fusion; yet it is not essential in vivo for OC and FBGC formation, or maintenance of bone homeostasis, at least under the conditions tested.