Solochrome cyanine: A histological stain for cobalt-chromium wear particles in metal-on-metal periprosthetic tissues.

Metal-on-metal (MoM) hip arthroplasties produce abundant implant-derived wear debris composed mainly of cobalt (Co) and chromium (Cr). Cobalt-chromium (Co-Cr) wear particles are difficult to identify histologically and need to be distinguished from other wear particle types and endogenous components (e.g., haemosiderin, fibrin) which may be present in MoM periprosthetic tissues. In this study we sought to determine whether histological stains that have an affinity for metals are useful in identifying Co-Cr wear debris in MoM periprosthetic tissues. Histological sections of periprosthetic tissue from 30 failed MoM hip arthroplasties were stained with haematoxylin-eosin (HE), Solochrome Cyanine (SC), Solochrome Azurine (SA) and Perls' Prussian Blue (PB). Sections of periprosthetic tissue from 10 cases of non-MoM arthroplasties using other implant biomaterials, including titanium, ceramic, polymethylmethacrylate (PMMA) and ultra-high molecular weight polyethylene (UHMWP) were similarly analysed. Sections of 10 cases of haemosiderin-containing knee tenosynovial giant cell tumour (TSGCT) were also stained with HE, SC, SA and PB. In MoM periprosthetic tissues, SC stained metal debris in phagocytic macrophages and in the superficial necrotic zone which exhibited little or no trichrome staining for fibrin. In non-MoM periprosthetic tissues, UHMWP, PMMA, ceramic and titanium particles were not stained by SC. Prussian Blue, but not SC or SA, stained haemosiderin deposits in MoM periprosthetic tissues and TSGT. Our findings show that SC staining (most likely Cr-associated) is useful in distinguishing Co-Cr wear particles from other metal/non-metal wear particles types in histological preparations of periprosthetic tissue and that SC reliably distinguishes haemosiderin from Co-Cr wear debris.

Polytetrafluoroethylene topographies determine the adhesion, activation, and foreign body giant cell formation of macrophages.

Polytetrafluoroethylene (PTFE) is one of the commonly used materials in making various cardiovascular implants. However, the success rates of these implants in several occasions are hindered by unwanted immune responses from immune cells, such as macrophages. In this study, we investigated the response of macrophages with different structures (flat, expanded, and electrospun) of PTFE having varied surface topographies: smooth planar surface (flat PTFE), node-fibrils (ePTFE), and randomly oriented microfibers (electrospun PTFE). The electrospun PTFE showed the least adhesion of macrophages. Also, the morphology of macrophages adhered on electrospun PTFE exhibited minimal activation. The macrophage pro-inflammatory cytokine secretions showed that the lowest level of TNF-α was produced on electrospun PTFE whereas IP-10 was produced in lowest levels on expanded PTFE (ePTFE). The production of IL-6 and MCP-1 cytokines was also dependent on the structure of PTFE that the macrophages interacted with, but in a time-dependent manner. Confocal microscopy images taken at 7, 14, and 21 days showed that the electrospun PTFE resulted in the lowest percentage of macrophage fusion, thus indicating the least possible chance of foreign body giant cell (FBGC) formation. Therefore, this study showed that electrospun PTFE with randomly oriented microfibers can provide reduced adhesion, activation, and FBGC formation of macrophages compared to the smooth and planar surface of flat PTFE and node-fibril structured surface of ePTFE. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2441-2450, 2017.

Foreign Body Reaction to Subcutaneous Implants.

Subcutaneously implanted materials trigger the host's innate immune system, resulting in the foreign body reaction. This reaction consists of protein adsorption on the implant surface, inflammatory cell infiltration, macrophage fusion into foreign body giant cells, fibroblast activation and ultimately fibrous encapsulation. This series of events may affect the function of subcutaneous implants, such as inhibition of drug diffusion from long-acting drug delivery depots and medical device failure. The foreign body reaction is a complex phenomenon and is not yet fully understood; ongoing research studies aim to elucidate the cellular and molecular dynamics involved. Recent studies have revealed information about the specific role of macrophages and their differential activation towards pro- and anti-inflammatory states, as well as species differences in the timing of collagen deposition and fibrosis. Understanding of the diverse processes involved in the foreign body reaction has led to multiple approaches towards its negation. Delivery of tissue response modifiers, such as corticosteroids, NSAIDs, antifibrotic agents, and siRNAs, has been used to prevent or minimize fibrosis. Of these, delivery of dexamethasone throughout the implantation period is the most common method to prevent inflammation and fibrosis. More recent approaches employ surface modifications to minimize protein adsorption to 'ultra-low' levels and reduce fibrosis. However, the diverse nature of the processes involved in the foreign body reaction favor the use of corticosteroids due to their wide spectrum action compared to other approaches. To date, combination approaches, such as hydrophilic coatings that reduce protein adsorption combined with delivery of dexamethasone are the most effective.

Molecular Characterization of Macrophage-Biomaterial Interactions.

Implantation of biomaterials in vascularized tissues elicits the sequential engagement of molecular and cellular elements that constitute the foreign body response. Initial events include the non-specific adsorption of proteins to the biomaterial surface that render it adhesive for cells such as neutrophils and macrophages. The latter undergo unique activation and in some cases undergo cell-cell fusion to form foreign body giant cells that contribute to implant damage and fibrotic encapsulation. In this review, we discuss the molecular events that contribute to macrophage activation and fusion with a focus on the role of the inflammasome, signaling pathways such as JAK/STAT and NF-κB, and the putative involvement of micro RNAs in the regulation of these processes.

Phenotypic expression in human monocyte-derived interleukin-4-induced foreign body giant cells and macrophages in vitro: dependence on material surface properties.

The effects of different material surfaces on phenotypic expression in macrophages and foreign body giant cells (FBGC) were addressed using our in vitro system of interleukin (IL)-4-induced macrophage fusion and FBGC formation. Arginine-glycine-aspartate (RGD)-, vitronectin (VN)-, and chitosan (CH)-adsorbed cell culture polystyrene, carboxylated (C, negatively charged) polystyrene, and unmodified (PS, non-cell culture treated) polystyrene were compared for their abilities to support monocyte/macrophage adhesion and IL-4-induced macrophage fusion. Pooled whole cell lysates from four different donors were evaluated by immunoblotting for expression of selected components in monocytes, macrophages, and FBGC. In addition to RGD and VN as previously shown, we find that CH supports macrophage adhesion and FBGC formation, whereas C or PS support macrophage adhesion but do not permit macrophage fusion under otherwise identical conditions of IL-4 stimulation. Likewise, components related to macrophage fusion (CD206, CD98, CD147, CD13) are strongly expressed on RGD-, VN-, and CH-adsorbed surfaces but are greatly diminished or not detected on C or PS. Importantly, material surfaces also influence the FBGC phenotype itself, as demonstrated by strong differences in patterns of expression of HLA-DR, B7-2, B7-H1, and toll-like receptor (TLR)-2 on RGD, VN, and CH despite morphologic similarities between FBGC on these surfaces. Likewise, we observe differences in the expression of B7-2, α2-macroglobulin, TLR-2, and fascin-1 between mononuclear macrophages on C and PS. Collectively, these findings reveal the extent to which material surface chemistry influences macrophage/FBGC phenotype beyond evident morphological similarities or differences and identify CH as an FBGC-supportive substrate.

Inhibition of foreign body giant cell formation by 4- hexylresorcinol through suppression of diacylglycerol kinase delta gene expression.

Grafted macromolecules often induce granuloma formation with foreign body giant cell (FBGC) infiltration, and this is the main reason for graft failure. Diacylglycerol kinase (DAGK) is an important intracellular mediator of FBGC formation in macrophages. In this study, 4-hexylresorcinol (4HR) inhibited DAGKδ in a macrophage cell line (RAW264.7 cells). As a result of DAGK-δ inhibition by 4HR, FBGC formation was significantly inhibited in RAW264.7 cells. Silk fibroin is a well-known natural macromolecule, and when it is grafted into bone defects, it results in granuloma formation with massive FBGC formation. 4HR-incorporating silk graft materials displayed significant reduction of granuloma formation and increases in the extent of new bone formation in a rabbit calvarial defect model. In conclusion, 4HR could inhibit foreign body reaction via a DAGK-mediated pathway.

Adsorbed fibrinogen enhances production of bone- and angiogenic-related factors by monocytes/macrophages.

Macrophages are phagocytic cells with great importance in guiding multiple stages of inflammation and tissue repair. By producing a large number of biologically active molecules, they can affect the behavior of other cells and events, such as the foreign body response and angiogenesis. Since protein adsorption to biomaterials is crucial for the inflammatory process, we addressed the ability of the pro-inflammatory molecule fibrinogen (Fg) to modulate macrophage behavior toward tissue repair/regeneration. For this purpose, we used chitosan (Ch) as a substrate for Fg adsorption. Freshly isolated human monocytes were seeded on Ch substrates alone or previously adsorbed with Fg, and allowed to differentiate into macrophages for 10 days. Cell adhesion and morphology, formation of foreign body giant cells (FBGC), and secretion of a total of 80 cytokines and growth factors were evaluated. Both substrates showed similar numbers of adherent macrophages along differentiation as compared with RGD-coated surfaces, which were used as positive controls. Fg did not potentiate FBGC formation. In addition, actin cytoskeleton staining revealed the presence of punctuate F-actin with more elongated and interconnecting cells on Ch substrates. Antibody array screening and quantification of inflammation- and wound-healing-related factors indicated an overall reduction in Ch-based substrates versus RGD-coated surfaces. At late times, most inflammatory agents were down-regulated in the presence of Fg, in contrast to growth factor production, which was stimulated by Fg. Importantly, on Ch+Fg substrates, fully differentiated macrophages produced significant amounts of macrophage inflammatory protein-1delta (MIP-1δ), platelet-derived growth factor-BB, bone morphogenetic protein (BMP)-5, and BMP-7 compared with Ch alone. In addition, other important factors involved in bone homeostasis and wound healing, such as growth hormone, transforming growth factor-ß3, and insulin-like growth factor-binding proteins, as well as several angiogenic mediators, including endocrine gland-derived vascular endothelial factor, fibroblast growth factor-7, and placental growth factor, were significantly promoted by Fg. This work provides a new perspective on the inflammatory response in the context of bone repair/regeneration mediated by a pro-inflammatory protein (Fg) adsorbed onto a biomaterial (Ch) that does not otherwise exhibit osteogenic properties.

Dexamethasone eluting cochlear implant: Histological study in animal model.

OBJECTIVE: New cochlear implant (CI) designs and developments in implantation techniques have revolutionized the management of hearing loss. However, cochlear implantation still has some disadvantages, such as its potential to initiate an inflammatory response that may lead to further hair cell damage. Recent topics of investigation have been the effect of glucocorticoids on inflammatory tissue response reduction, glucocorticoid dosage levels, and drug-delivery methods. In the present study, dexamethasone delivery via a drug-eluting CI was evaluated histologically through assessing inflammatory cell infiltration. METHODS AND MATERIALS: Thirty healthy, adult male guinea pigs were included and randomly assigned to one of three surgical groups that underwent cochleostomy of the basal turn. The experimental group (Group 1) of 12 animals were implanted with a dexamethasone-loaded silicone elastomer shaped like a CI electrode. The primary control group (Group 2) of 12 animals were implanted with a simple CI (non-eluting). A second control group (Group 3) of six animals underwent cochleostomy only. Inflammatory responses were compared between groups by evaluating inflammatory cell infiltration in inner-ear specimens at days 3 and 13. RESULTS: The Mann­Whitney test revealed reduction in most of the inflammatory indices in Group 1 compared with Group 2. This was significant for fibrocyte, macrophage, and giant cell infiltration at day 3 as well as lymphocyte, macrophage infiltration, and capillary formation at day 13. CONCLUSION: This study showed some attenuation in inflammatory response following insertion of a dexamethasone-eluting CI, suggesting that it could be a route for local drug delivery into the cochlea.

Complications of Bioglue postsurgery for aortic dissections and aortic valve replacement.

AIMS: Bioglue is an adhesive used during cardiovascular surgery to improve hemostasis perioperatively and to strengthen and reinforce vascular anastomoses. It has also been used to 'seal' the false lumen in patients presenting with acute aortic dissections. Herein, we examine the complications of Bioglue, which may lead to redo sternotomy in selected patients. METHODS: A review of pathology records at our institution from 2002 to 2010 found 4 cases of excised aortic tissue and/or aortic valves with previous Bioglue use at initial operation. Excised tissues and valves were examined, looking for the presence of Bioglue, inflammatory cells (acute, chronic, macrophage and giant cells) and micro-organisms. Patient demographics were also reviewed and recorded. RESULTS: We identified four cases of Bioglue use found at redo surgery, after the formation of pseudoaneurysm (n=3) and aortic stenosis (n=1). Mean interval to redo surgery was 2.28 + 0.32 years (range 2-2.6 years). Pseudoaneurysm formation was thought to be caused by an inflammatory reaction to the Bioglue itself in two cases, while one case found no such reaction. One patient with previous aortic valve replacement had large annular abscesses filled with necrotic debris surrounding the prosthesis and pannus found on the sewing cuff, comprised of Bioglue itself. CONCLUSIONS: The mechanisms leading to these complications include mechanical strain, inflammation and tissue necrosis. The judicious use of Bioglue when clinically indicated, and close follow-up of these patients with serial imaging, remain an integral part of avoiding future complications.

Light- and transmission-electron-microscopic investigations on distribution of CD44, connexin 43 and actin cytoskeleton during the foreign body reaction to a nanoparticular hydroxyapatite in mini-pigs.

Foreign body giant cells (FBGCs) are formed by fusion of mononucleated macrophages during the foreign body response to a nanoparticulate hydroxyapatite (HA) implanted in defects of mini-pig femura. The molecular mechanisms underlying the formation of FBGCs are still largely obscure. Here we propose connexin 43 (cx43) and CD44 as candidate molecules involved in the fusion process. Immunohistochemistry and ultrastructural immunogold labeling indicated that cx43 is present within the ruffled border of FBGCs and is the main component of gap junctions formed between fusing macrophages. CD44 was strongly expressed during clustering and fusion of mononucleated macrophages. FBGCs adhering apically at the implanted HA showed CD44 reactivity only along the basolateral aspects of the plasma membranes, while podosome formation was observed within the sealing zone and ruffled border. Taken together, these findings demonstrate that cx43 and CD44 are part of the fusion machinery responsible for the formation of FBGCs. Furthermore, the results of microfilament and cx43 labeling suggest a functional role for podosomes and hemi-channels in biomaterial degradation.

Histological evaluation of bone response to pediatric endodontic pastes: an experimental study in guinea pig.

This study aimed to evaluate by the intra-osseous implant technique the most commonly used materials for pulp therapy in pediatric dentistry: calcium hydroxide (CH), Guedes Pinto paste and CTZ paste, according to FDI (1980) and ANSI/ADA (1982) recommendations. Thirty guinea pigs, 10 for each material, divided into experimental periods of 4 and 12 weeks received one implant on each side of the lower jaw symphysis. The external lateral tube wall served as control for the technique. At the end of the observation periods, the animals were euthanized and specimens were prepared for routine histological examination. It was observed that CH and CTZ paste induced severe inflammation, a large amount of necrotic tissue, lymphocytes, foreign body cells and bone resorption, while Guedes Pinto Paste induced little or no inflammation in the 4-week observation period. After 12 weeks, the reactions to CH and Guedes Pinto paste were also absent/mild, presenting a general pattern of replacement by recently formed bone tissue while a moderate to severe inflammatory response was observed with CTZ paste. Guedes Pinto paste presented acceptable biocompatibility levels in both analyzed periods; CH only showed acceptable biocompatibility in the 12-week period while CTZ paste showed no biocompatibility in both periods. Among the tested materials, only Guedes Pinto paste presented an acceptable biocompatibility.

Histological evaluation of bone response to pediatric endodontic pastes: an experimental study in guinea pig

This study aimed to evaluate by the intra-osseous implant technique the most commonly used materials for pulp therapy in pediatric dentistry: calcium hydroxide (CH), Guedes Pinto paste and CTZ paste, according to FDI (1980) and ANSI/ADA (1982) recommendations. Thirty guinea pigs, 10 for each material, divided into experimental periods of 4 and 12 weeks received one implant on each side of the lower jaw symphysis. The external lateral tube wall served as control for the technique. At the end of the observation periods, the animals were euthanized and specimens were prepared for routine histological examination. It was observed that CH and CTZ paste induced severe inflammation, a large amount of necrotic tissue, lymphocytes, foreign body cells and bone resorption, while Guedes Pinto Paste induced little or no inflammation in the 4-week observation period. After 12 weeks, the reactions to CH and Guedes Pinto paste were also absent/mild, presenting a general pattern of replacement by recently formed bone tissue while a moderate to severe inflammatory response was observed with CTZ paste. Guedes Pinto paste presented acceptable biocompatibility levels in both analyzed periods; CH only showed acceptable biocompatibility in the 12-week period while CTZ paste showed no biocompatibility in both periods. Among the tested materials, only Guedes Pinto paste presented an acceptable biocompatibility.

A pesquisa teve como objetivo avaliar a biocompatibilidade através da técnica de implantes intra-ósseos dos materiais utilizados em odontopediatria para tratamento pulpar: hidróxido de cálcio, pastas Guedes Pinto e CTZ, de acordo com as recomendações da FDI (1980) e ANSI/ADA(1982). Trinta guinea pigs, dez para cada material, divididos em períodos experimentais de 4 e 12 semanas receberam um implante em cada lado da sínfise mandibular. A parede lateral externa do copo serviu como controle para a técnica. No final dos períodos experimentais, os animais foram sacrificados e os espécimes preparados para o exame histológico de rotina. Observou-se que o hidróxido de cálcio e a pasta CTZ mostraram reação inflamatória severa, grande quantidade de tecido necrosado, linfócitos, células de corpo estranho e reabsorção óssea; enquanto a pasta Guedes Pinto induziu pouca ou nenhuma inflamação no período de 4 semanas. Após 12 semanas as reações para o hidróxido de cálcio e pasta Guedes Pinto foram ausentes/suaves apresentando um padrão geral de substituição por tecido ósseo neoformado, enquanto uma resposta inflamatória de moderada a severa foi observada para a pasta CTZ. A pasta Guedes Pinto apresentou níveis aceitáveis de biocompatibilidade nos dois períodos analisados; hidróxido de cálcio apresentou biocompatibilidade aceitável somente no período de 12 semanas e a pasta CTZ não mostrou biocompatibilidade em ambos os períodos. Entre estes, apenas a pasta Guedes Pinto apresentou níveis de biocompatibilidade nos dois períodos analisados.

Functionalization of deproteinized bovine bone with a coating-incorporated depot of BMP-2 renders the material efficiently osteoinductive and suppresses foreign-body reactivity.

The repair of critical-sized bony defects remains a challenge in the fields of implantology, maxillofacial surgery and orthopaedics. As an alternative bone-defect filler to autologous bone grafts, deproteinized bovine bone (DBB) is highly osteoconductive and clinically now widely used. However, this product suffers from the disadvantage of not being intrinsically osteoinductive. In the present study, this property was conferred by coating DBB with a layer of calcium phosphate into which bone morphogenetic protein 2 (BMP-2) was incorporated. Granules of DBB bearing a coating-incorporated depot of BMP-2--together with the appropriate controls (DBB bearing a coating but no BMP-2; uncoated DBB bearing adsorbed BMP-2; uncoated DBB bearing no BMP-2)--were implanted subcutaneously in rats. Five weeks later, the implants were withdrawn for a histomorphometric analysis of the volume densities of (i) bone, (ii) bone marrow, (iii) foreign-body giant cells and (iv) fibrous capsular tissue. Parameters (i) and (ii) were highest, whilst parameters (iii) and (iv) were lowest in association with DBB bearing a coating-incorporated depot of BMP-2. Hence, this mode of functionalization not only confers DBB with the property of osteoinductivity but also improves its biocompatibility--thus dually enhancing its clinical potential in the repair of bony defects.

The effect of a slow mode of BMP-2 delivery on the inflammatory response provoked by bone-defect-filling polymeric scaffolds.

We investigated the inflammatory response to, and the osteoinductive efficacies of, four polymers (collagen, Ethisorb, PLGA and Polyactive) that bore either an adsorbed (fast-release kinetics) or a calcium-phosphate-coating-incorporated (slow-release kinetics) depot of BMP-2. Titanium-plate-supported discs of each polymer (n = 6 per group) were implanted at an ectopic (subcutaneous) ossification site in rats (n = 48). Five weeks later, they were retrieved for a histomorphometric analysis of the volumes of ectopic bone and foreign-body giant cells (a gauge of inflammatory reactivity), and the degree of polymer degradation. For each polymer, the osteoinductive efficacy of BMP-2 was higher when it was incorporated into a coating than when it was directly adsorbed onto the material. This mode of BMP-2 carriage was consistently associated with an attenuation of the inflammatory response. For coated materials, the volume density of foreign-body giant cells was inversely correlated with the volume density of bone (r(2) = 0.96), and the volume density of bone was directly proportional to the surface-area density of the polymer (r(2) = 0.97). Following coating degradation, other competitive factors, such as the biocompatibility and the biodegradability of the polymer itself, came into play.

Cholate-containing high-fat diet induces the formation of multinucleated giant cells in atherosclerotic plaques of apolipoprotein E-/- mice.

OBJECTIVE: To determine the role of multinucleated giant cells (MGCs) in cardiovascular diseases. METHODS AND RESULTS: MGCs are a hallmark of giant cell arteritis. They are also described in atherosclerotic plaques from aortic aneurysms and carotid and coronary arteries. Herein, we demonstrate that the cholate-containing Paigen diet yields many MGCs in atherosclerotic plaques of apolipoprotein E-/- mice. These mice revealed a 4-fold increase in MGC numbers when compared with mice on a Western or Paigen diet without cholate. Most of the MGCs stained intensively for cathepsin K and were located at fibrous caps and close to damaged elastic laminae, with associated medial smooth muscle cell depletion. During in vitro experiments, MGCs demonstrated a 6-fold increase in elastolytic activity when compared with macrophages and facilitated transmigration of smooth muscle cells through a collagen-elastin matrix. An elastin-derived hexapeptide (Val-Gly-Val-Ala-Pro-Gly [VGVAPG]) significantly increased the rate of macrophage fusion, providing a possible mechanism of in vivo MGC formation. Comparable to the mouse model, human specimens from carotid arteries and aortic aneurysms contained cathepsin K-positive MGCs. CONCLUSIONS: Apolipoprotein E-/- mice fed a Paigen diet provide a model to analyze the tissue-destructive role of MGCs in vascular diseases.

Macrophage fusion leading to foreign body giant cell formation persists under phagocytic stimulation by microspheres in vitro and in vivo in mouse models.

The formation of surface-damaging foreign body giant cells (FBGC) from the fusion of macrophages is considered a hallmark of the foreign body response. Experimental evidence indicates that when macrophages are unable to internalize foreign bodies via phagocytosis due to their large size, they acquire a fusogenic phenotype. The mechanism behind this transformation is unclear, and questions, such as which phenotype takes precedence for co-stimulated macrophages engaged in the foreign body response and whether or not such phenotypic alteration is graded, remain unanswered. By recapitulating fusion in vitro using cell lines and primary mouse bone marrow-derived macrophages, we investigated whether concurrent exposure of macrophages to phagocytic and fusogenic stimuli would limit fusion. Induction of phagocytosis by addition of 3.0 mum-diameter polystyrene microspheres to cells under fusogenic conditions, at ratios of 1:10, 1:1, and 10:1 did not prevent fusion. To determine the effect of microsphere phagocytosis on fusion in vivo, we first determined the kinetics of monocyte recruitment, surface adhesion, and fusion following intraperitoneal implantation of a foreign body in a mouse model. Concomitant or subsequent injection of microspheres resulted in their significant accumulation at the biomaterial surface at 2 weeks, but FBGC were still detected. Our findings indicate that despite increasing the abundance of a phagocytic stimulus (microspheres), significant FBGC formation occurs.

Immunologic adverse reaction associated with low-carbide metal-on-metal bearings in total hip arthroplasty.

BACKGROUND: An increased incidence of periprosthetic osteolysis, resulting in loss of biologic fixation, has been reported in contemporary THAs with low-carbide metal-on-metal compared with metal-on-polyethylene couple bearings. Although a hypersensitivity reaction attributable to Co and Cr debris is reportedly a potential cause for failure of THAs with high-carbide bearings, there are no evidence-based data for this reaction in low-carbide metal-on-metal bearings, although such hypersensitivity might be related to osteolysis. QUESTIONS/PURPOSES: We investigated whether there were differences in immunologic hypersensitivity reactions in retrievals from revised THAs with ceramic-on-polyethylene versus metal-on-metal bearing couples. PATIENTS AND METHODS: We compared newly formed capsule and periprosthetic interface membranes from revision surgery for aseptic failure from 20 patients with low-carbide bearings and 13 patients with ceramic-on-polyethylene bearings. For control tissue, we obtained samples from the hip capsule during the primary THA implantation in 13 patients with low-carbide bearings and seven with ceramic-on-polyethylene bearings. We examined the tissues with conventional histologic and immunohistochemical methods. RESULTS: Compared with tissue from the control subjects and patients with ceramic-on-polyethylene bearings, the tissues from patients with low-carbide metal-on-metal bearings were associated with (1) extensive necrosis and fibrin exudation in the newly formed hip capsule and (2) diffuse and perivascular lymphocytic infiltration of a higher degree than in the hips with ceramic-on-polyethylene bearings in conventional histologic examination, and (3) more T than B cells. CONCLUSIONS: The conventional histologic and immunohistochemical findings in tissues retrieved from failed THAs with low-carbide metal-on-metal bearings are consistent with a link between hypersensitivity and osteolysis with low-carbide bearing couples.

Lymphocyte adhesion and interactions with biomaterial adherent macrophages and foreign body giant cells.

To characterize the effects of adherent macrophages and biomaterial surface chemistries on lymphocyte adhesion and activation, lymphocytes were co-cultured with monocytes alone and together, directly and separated by a porous membrane transwell on hydrophobic, hydrophilic/neutral, hydrophilic/anionic, and hydrophilic/cationic biomaterial surfaces. Surface adherent cells were quantitatively analyzed after 3 days utilizing immunofluorescence and phase contrast imaging. After periods of 3, 7, and 10 days, secreted interferon-gamma (IFN-gamma) was quantified by ELISA. Limited direct biomaterial-adherent lymphocytes were identified regardless of the presence of macrophages or foreign body giant cells (FBGC). The majority of adherent lymphocytes, which were T cells (>95%) rather than natural killer cells, predominantly interacted with adherent macrophages and FBGCs; greater than 90% were interacting on surfaces with higher levels of adherent macrophages and FBGCs and greater than 55% were interacting on surfaces with lower levels of macrophages and FBGCs. The hydrophilic/anionic surface promoted higher levels of macrophage- and FBGC-adherent lymphocytes but was nonselective for lymphocyte subtype interactions. The hydrophilic/neutral surface was selective for CD4+ T lymphocyte interactions while the hydrophobic surface was selective for CD8+ T lymphocyte interactions. IFN-gamma was produced in direct and indirect co-cultures but not in lymphocyte- and monocyte-only cultures suggesting that lymphocytes are activated via macrophage-derived cytokines rather than direct biomaterial contact. Direct lymphocyte interactions with adherent macrophages/FBGCs enhanced IFN-gamma production relative to indirect co-cultures. These results suggest that lymphocytes prefer interactions with adherent macrophages and FBGCs, resulting in lymphocyte activation, and these interactions can be influenced by biomaterial surface chemistries.

Histological analysis of the association between formocresol and endotoxin in the subcutaneous tissue of mice.

This study performed a histological analysis of the effect of formocresol associated to endotoxin (LPS) in the subcutaneous connective tissue of mice. Ninety mice were randomly assigned to 3 groups (n=30). Each animal received one plastic tube implant containing endotoxin solution (10 mg/mL), formocresol (original formula) or a mixture of endotoxin and formocresol. The endotoxin and formocresol groups served as controls. The periods of analysis were 7, 15 and 30 days. At each experimental period, tissue samples were collected and submitted to routine processing for histological analysis. Endotoxin and formocresol produced necrosis and chronic inflammation at 7 and 15 days. At 30 days, the endotoxin group showed no necrosis, while in the formocresol group necrosis persisted. The formocresol-endotoxin association produced necrosis and chronic inflammation in the same way as observed with formocresol at all experimental periods. In conclusion, formocresol seems not to be able to inactive the toxic effects of endotoxin in connective tissues.

Histological analysis of the association between formocresol and endotoxin in the subcutaneous tissue of mice

This study performed a histological analysis of the effect of formocresol associated to endotoxin (LPS) in the subcutaneous connective tissue of mice. Ninety mice were randomly assigned to 3 groups (n=30). Each animal received one plastic tube implant containing endotoxin solution (10 mg/mL), formocresol (original formula) or a mixture of endotoxin and formocresol. The endotoxin and formocresol groups served as controls. The periods of analysis were 7, 15 and 30 days. At each experimental period, tissue samples were collected and submitted to routine processing for histological analysis. Endotoxin and formocresol produced necrosis and chronic inflammation at 7 and 15 days. At 30 days, the endotoxin group showed no necrosis, while in the formocresol group necrosis persisted. The formocresol-endotoxin association produced necrosis and chronic inflammation in the same way as observed with formocresol at all experimental periods. In conclusion, formocresol seems not to be able to inactive the toxic effects of endotoxin in connective tissues.

O objetivo deste estudo foi avaliar histologicamente o efeito da associação do formocresol com endotoxina (LPS) em tecido conjuntivo de camundongos. Noventa camundongos foram divididos em três grupos de 30 camundongos cada. Cada camundongo recebeu um implante subcutâneo de tubo plástico contendo solução de endotoxina (10 mg/ml), formocresol (fórmula original), ou uma mistura de formocresol com endotoxina. Os grupos da endotoxina e formocresol foram considerados grupos controle. Os períodos de análise foram 7, 15 e 30 dias. Após os períodos experimentais, os tecidos foram removidos e submetidos a processamento histológico. Os resultados obtidos indicam que a endotoxina e o formocresol produzem necrose e inflamação tecidual crônica aos 7 e 15 dias e aos 30 dias o grupo da endotoxina não mostrava necrose e no grupo do formocresol a necrose persistiu. A combinação formocresol e endotoxina mostrou necrose e inflamação crônica com resultados semelhantes ao do grupo formocresol para todos os períodos experimentais. Pode-se concluir que o formocresol parece não ser capaz de inativar os efeitos tóxicos da endotoxina.