Sam Nasser

Inflammatory responses to orthopaedic biomaterials in the murine air pouch.

An in vivo model of the inflammatory response to orthopaedic biomaterials was used to examine cellular and cytokine responses to polymer particles of ultra high molecular weight polyethylene (UHMWPE) and polymethylmethacrylate (PMMA), and metal particles of cobalt-chrome (Co-Cr) and titanium alloy (Ti-6Al-4V). Responses were determined separately and in combinations, to examine interactions between different forms of biomaterials. Murine air pouches were injected with particle suspensions, and reactions evaluated using histological, immunological, and molecular techniques. All particulate biomaterials caused significant increases in membrane thickness compared with control (saline) air pouches, with the highest reaction seen in response to Ti-6Al-4V particles. A synergistic increase in membrane thickness was observed when PMMA was combined with UHMWPE, suggesting that multiple biomaterial stimuli markedly increase the inflammatory reaction. Cellular analysis indicated that all particles increased the absolute number and the percentage of macrophages in the membrane over the control level, with the most pronounced increase due to individual biomaterial occurring with UHMWPE particles. Cytokine analysis revealed that biomaterials provoked a strong IL-1 response. Ti-6Al-4V stimulated the highest IL-6 gene transcription and the lowest IL-1 gene transcription. The data suggest that synergism in the inflammatory response to biomaterials may be important in adverse responses to orthopaedic wear debris.

Direct-Exchange Arthroplasty for the Treatment of Infection after Total Hip Replacement. An Average Ten-Year Follow-up*

Twenty consecutive patients who had a direct-exchange total hip arthroplasty, performed by one surgeon between October 1979 and July 1990, were prospectively followed and data were collected. The most common infecting organism was Staphylococcus epidermidis (nine patients), followed by Streptococcus species and Staphylococcus aureus (five patients each). Three patients (15 per cent) had a draining sinus tract at the time of the operation. The operation and the postoperative management included meticulous débridement, administration of appropriate systemic antibiotic therapy, and use of antibiotic-loaded cement. By an average of 9.9 years (range, 3.5 to 17.1 years) postoperatively, no patient had had recurrence of the infection. Two patients had a revision for aseptic loosening nine and seventeen years after the direct exchange. Although the present series is relatively small, our experience has shown that direct exchange, which is associated with less morbidity and is less expensive than delayed exchange, can be successful in carefully selected patients.

Diverse cellular and apoptotic responses to variant shapes of UHMWPE particles in a murine model of inflammation.

The wear of orthopaedic prostheses results in the release of a markedly heterogeneous assortment of particulate debris, with respect to both size and shape. Although particle size has been extensively examined, the role of particle shape in adverse inflammatory reactions to debris remains unclear. Using an in vivo murine model of inflammation, we assessed tissue responses to globular and to elongated ultra-high molecular weight polyethylene (UHMWPE) particles with a similar surface area, and investigated whether inflammation and cellular apoptosis varied with particle shape in the debris-tissue interaction. Histological changes of UHMWPE-stimulated pouch membrane were assessed using a computerized image analysis system. Quantitative real time PCR and ELISA were performed to assess mRNA expression and protein level of the cytokines, and TUNEL assays were conducted to quantify apoptotic cells. The data revealed that elongated particles generated more active inflammatory air pouches, stimulated more severe membrane proliferation and the inflammatory cellular infiltration compared to globular particles. Increased levels of IL-1beta and TNFalpha were detected in the lavage and homogenate of pouches stimulated with elongated particles in comparison to pouches with globular particles, and the apoptotic assay indicated more severe apoptotic changes within the inflammatory membrane provoked with elongated particles. Our results suggest that cellular responses to UHMWPE wear debris are dependent on the shape of the particles.

The immune response to implant materials in humans.

The etiology of aseptic loosening of prosthetic joint replacement components is unclear. Implant materials have been considered biologically inert, but recent studies indicate that inflammatory reactions directed against the implanted materials may contribute to aseptic loosening. Data suggesting a progression from a simple inflammatory reaction to complex immune responses against the biomaterials are reviewed. The cellular responses to particles of polymethylmethacrylate, ultrahigh molecular weight polyethylene, and alloys of cobaltchromium and titanium were assayed in vitro to determine cell proliferation in patients with underlying diagnoses of osteoarthrosis, rheumatoid arthritis, and avascular necrosis who had joint replacement. Control populations were provided by patients with similar diagnoses who were preoperative surgical candidates. The underlying diagnoses did not seem to influence responses to particle stimulation. Elevated responses to both acrylic and cobaltchromium were observed in patients with aseptically loosened prostheses. These findings suggest that the development of a cellular response to particulate debris may be significant in the pathogenesis of aseptic loosening.

Long-term effectiveness of translational manipulation for adhesive capsulitis.

Long term effects of glenohumeral joint translational (gliding) manipulation on range of motion, pain, and function in patients with adhesive capsulitis were studied. Thirty-one patients underwent brachial plexus block followed by translational manipulation of the glenohumeral joint. Changes in range of motion and pain were assessed before manipulation with the patient under anesthesia, immediately after manipulation with the patient still under anesthesia, at early followup (5.3 ± 3.2 weeks), and at long term followup (14.4 ± 7.3 months). Passive range of motion increased significantly for flexion, abduction, external rotation, and internal rotation. Significant decreases in visual analog pain scores between initial evaluation and the followup assessments also occurred. Furthermore, Wolfgangs criteria score increased significantly between initial evaluation and followup assessments. Translational manipulation provides a safe, effective treatment option for adhesive capsulitis.

Total Joint Arthroplasty and the Immune Response

Total joint replacement arthroplasty has proved highly successful in the management of osteoarthritis and rheumatoid arthritis. The cause of aseptic loosening of prosthetic joint replacement components is unclear. Early experience with total joint arthroplasty was plagued by a number of problems that no longer exist as major impediments to long-term success. Improvement in the operating room environment and the use of prophylactic antibiotics have substantially reduced the high incidence of infection to less than 1%. Implant materials have long been considered biologically inert, but recent studies indicate that inflammatory reactions directed against the implanted materials may contribute to aseptic loosening. Currently, particulate debris from cement or polyethylene causing loosening of the prosthesis is the major problem in total joint arthroplasty. Significant data suggest a progression from a simple inflammatory reaction to complex immune responses against the biomaterials. The cellular responses to particles of polymethylmethacrylate, ultra-high-molecular-weight polyethylene, and alloys of cobalt-chromium and titanium have been assayed in vitro in patients with osteoarthritis, rheumatoid arthritis, and avascular necrosis who had total joint replacement. Elevated immunologic cell proliferation responses to both acrylic and cobalt chromium were observed in patients with aseptically loosened prostheses. These findings suggest that the development of a cellular response to particulate debris may be significant in the pathogenesis of aseptic loosening.

Proteins bound to polyethylene components in patients who have aseptic loosening after total joint arthroplasty. A preliminary report.

BACKGROUND Immunological responses to proteins that adhere to ultra-high molecular weight polyethylene have not, to our knowledge, been examined previously in patients who have aseptic loosening. In the current study, polyethylene components from forty-nine failed prostheses recovered during revision procedures were examined for the presence of antibodies that were bound to the polyethylene surface or that were reactive with other proteins that were bound to the polyethylene surface. METHODS The polyethylene components consisted of thirty acetabular cups recovered during revision total hip arthroplasties and nineteen tibial components recovered during revision total knee arthroplasties. After extensive washing, bound proteins were extracted from the polyethylene components with use of 0.1-molar glycine-hydrogen chloride solution followed by four-molar guanidine hydrochloride solution. RESULTS Sufficient protein for analysis was recovered from forty-two polyethylene components. Polyacrylamide gel electrophoresis demonstrated a minimum of one and a maximum of twelve protein bands, with molecular weights ranging from thirteen to 231 kilodaltons. Immunoblotting revealed the presence of type-I collagen in most (thirty-four) of the forty-two explants, whereas aggrecan proteoglycans were detected in eight samples. Immunoglobulin also was detected in most (thirty-three) extracts, whereas type-II collagen was consistently absent. The presence of autologous antibodies directed against polyethylene-bound proteins in sera drawn at the time of the revision was investigated. Antibodies that were reactive against the ultra-high molecular weight polyethylene-bound proteins were detected in twenty-six of the forty-two patients with use of the Western blot technique. The number of reactive bands ranged from one to six, and the strongest binding was directed against a 103-kilodalton protein. Assays for specificity revealed that these sera autologous antibodies were reactive against the type-I collagen that was present in the explant solutions. CONCLUSIONS We hypothesize that immunoglobulin complexed with polyethylene may fix complement and that the complement cascade may in turn attract inflammatory cells to the polyethylene surface. Our data support the hypothesis that an immunological response to antigens bound to the polyethylene surface may contribute to aseptic loosening. CLINICAL RELEVANCE Despite improvements in materials and designs of prostheses, aseptic loosening is the most common complication of total joint replacement, frequently leading to revision operations. We examined the immunological response to proteins that bind to ultra-high molecular weight polyethylene in patients who had aseptic loosening and discovered a high prevalence of antibodies to polyethylene-bound proteins. This immunological response may contribute to an inflammatory reaction in the periprosthetic tissue, ultimately leading to increased bone resorption around the prosthesis.

The roles of monocytic heat shock protein 60 and Toll-like receptors in the regional inflammation response to wear debris particles

The biological response to orthopaedic wear debris is central to peri-prosthetic tissue inflammation and osteolysis, through mechanisms that include local inflammatory cytokine production. In particular, interleukin-1 beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha|) are generated in high quantities following monocyte accumulation in periprosthetic inflammatory tissue, and these cytokine combine with other inflammatory mediators to trigger osteolysis. Since the precise mechanisms involved in debris-associated inflammation remain unclear, it is important to understand how wear debris particles initially interact with inflammatory cells. We have previously demonstrated that the severity of the inflammation response is influenced by the size, shape, and quantity of particles accumulated in tissues. The current in vitro and in vivo results indicate that heat-shock protein (Hsp) expression is elevated when monocytes are exposed to wear debris particles. We have also addressed the mechanisms by which heat-shock protein 60 (Hsp60) positively modulates inflammatory cytokines via Toll-like receptor-4 (TLR4) signal transduction pathway on mononuclear cells. Furthermore, down-regulation of TLR4 expression using antisense oligonucleotides targeted to TLR4 mRNA suppressed cytokine production in both exogenous Hsp60 and particles stimulated cultures. Collectively, these data indicate that monocytic Hsp60 is an additional inducible immunoregulatory mediator in response to particle-induced cell stress.

Human periprosthetic tissues implanted in severe combined immunodeficient mice respond to gene transfer of a cytokine inhibitor.

BACKGROUND Periprosthetic tissue formation and local inflammation that are associated with wear debris contribute to the pathogenesis of aseptic loosening of a prosthesis. This study evaluated a retrovirus-mediated gene therapy with use of a novel xenograft-based animal model. METHODS Human periprosthetic tissues obtained from patients during revision arthroplasty performed because of aseptic loosening of a prosthetic joint were transplanted into the left quadriceps and paravertebral muscles of severe combined immunodeficient (SCID) mice. The engrafted tissues were recovered seven, fifteen, or thirty days after implantation for histological and molecular analyses. The periprosthetic tissues were incubated with retroviruses encoding for human interleukin-1 receptor antagonist (hIL-1Ra) or bacteria beta-galactosidase (LacZ) at 37 degrees C for three hours prior to implantation to evaluate their responses to gene modification. RESULTS The human periprosthetic tissues were well accepted in SCID mice for up to thirty days, with angiogenesis occurring in the majority of the implanted tissue sections. The histological appearance was consistent between the recovered graft tissue and the original donor tissue. Strong expression of interleukin-1, tumor necrosis factor, and interleukin-6 was detected in the xenografts with use of immunohistochemical stains. Histological analysis revealed that interleukin-1 receptor antagonist gene modification significantly decreased the total number of inflammatory cells (p < 0.01) in engrafted human tissue containing implant wear debris. Real-time reverse transcription-polymerase chain reaction and immunohistochemical staining showed declining expression levels of interleukin-1 and tumor necrosis factor following interleukin-1 receptor antagonist gene transfer in comparison with LacZ-transduced or virus-free controls. CONCLUSIONS Human periprosthetic tissue can survive in the SCID mouse host for up to thirty days and responds to the interleukin-1 receptor antagonist gene transfer with the amelioration of inflammation.

Pristane-induced arthritis in mice: V. Susceptibility to pristane-induced arthritis is determined by the genetic regulation of the T cell repertoire

OBJECTIVE Pristane-induced arthritis (PIA) is an experimental seropositive arthritis that is characterized by serologic and cellular immune abnormalities and is dependent on the presence of a competent CD4+ T cell population. We examined the regulation of PIA by genes of the major histocompatibility complex (MHC) and the Mls-1 loci to determine whether the selection of the T cells that infiltrate arthritic joints is a critical factor in disease susceptibility. METHODS Genetic regulation of PIA was investigated using F1 hybrid and congenic strain analysis to determine the influence of MHC and Mls-1 genes. The T cell receptor Vbeta phenotypes of lymph node cells and T cells infiltrating arthritic joints were examined with 2-color flow cytometry and reverse transcription-polymerase chain reaction techniques. RESULTS F1 hybrid offspring from 2 major PIA-susceptible strains (DBA/1 x BALB/c) were resistant to the induction of arthritis because of the interaction between genes of the MHC and the Mls-1 loci, which modified the T cell repertoire. This conclusion was supported by the observed resistance to PIA in BALB/ c-Mls-1a mice, where T cells expressing the Vbeta8.1 and Vbeta6 phenotypes were absent. The receptor phenotype of T cells infiltrating arthritic joints in DBA/1 mice was markedly skewed toward Vbeta8.1 and Vbeta6 compared with the population observed in lymph nodes from either PIA or normal control DBA/1 mice. CONCLUSION The data support the hypothesis that PIA is a T cell-mediated disease. While pristane causes a polyclonal T cell expansion that gives rise to lymphadenopathy, the development of arthritis in susceptible strains of mice occurs due to the preservation of specific T cell subsets with the capacity to infiltrate synovial joints.