Association between apoptotis and CD4(+)/CD8(+) T-lymphocyte ratio in aseptic loosening after total hip replacement

Roles of inflammatory cell infiltrate in periprosthetic osteolysis

Classically, particle-induced periprosthetic osteolysis at the implant-bone interface has explained the aseptic loosening of joint replacement. This response is preceded by triggering both the innate and acquired immune response with subsequent activation of osteoclasts, the bone-resorbing cells. Although particle-induced periprosthetic osteolysis has been considered a foreign body chronic inflammation mediated by myelomonocytic-derived cells, current reports describe wide heterogeneous inflammatory cells infiltrating the periprosthetic tissues. This review aims to discuss the role of those non-myelomonocytic cells in periprosthetic tissues exposed to wear particles by showing original data. Specifically, we discuss the role of T cells (CD3+, CD4+, and CD8+) and B cells (CD20+) coexisting with CD68+/TRAP- multinucleated giant cells associated with both polyethylene and metallic particles infiltrating retrieved periprosthetic membranes. This review contributes valuable insight to support the complex cell and molecular mechanisms behind the aseptic loosening theories of orthopedic implants.

Observation of Anesthetic Effect of Dexmedetomidine Combined With Intraspinal Anesthesia in Hip Arthroplasty and its Effect on Postoperative Delirium and Stress Response

Objective

To observe the anesthetic effect of dexmedetomidine combined with spinal anesthesia in hip arthroplasty, and to analyze the effects of dexmedetomidine on postoperative stress response, incidence of delirium, immune function and inflammatory indicators.

Methods

A total of 42 patients who underwent hip replacement in our hospital from March 2020 to June 2021 were selected as the research subjects and randomly divided into the control group and the observation group, 21 cases in each group. The control group was given intraspinal anesthesia, and the observation group was given dexmedetomidine on this basis. The onset time and maintenance time of sensory and motor nerve block were recorded. Stress response indexes [cortisol (Cor), blood glucose (Glu), adrenaline (E), noadrenaline (NE)], T lymphocyte subsets (CD3+, CD4+, CD8+, CD4+/CD8+), inflammatory indexes [tumor necrosis factor -α (TNF-α) and interleukin-6 (IL-6)] were detected before and after operation, and the incidence of postoperative delirium in both groups was recorded.

Results

The onset time of sensory nerve block and motor block in the observation group were lower than those in the control group, and the retention time of sensory nerve block and motor nerve block were higher than those in the control group (P < 0.05). After surgery, the levels of Cor, Glu, E and NE in the observation group were lower than those in the control group (P < 0.05). After surgery, the incidence of postoperative delirium in the observation group (4.79%) was lower than that in the control group (28.57%) (P < 0.05). After surgery, the levels of CD3+, CD4+, CD8+, and CD4+/CD8+ in the observation group were higher than those in the control group (P < 0.05). After surgery, the levels of TNF-α and IL-6 in the observation group were lower than those in the control group (P < 0.05).

Conclusion

The combined use of dexmedetomidine and intraspinal anesthesia has good anesthesia effect in hip joint replacement, which can greatly reduce the stress response of patients, reduce the incidence of postoperative delirium, and effectively restore the immune function of patients, reduce the level of inflammatory response, and has high clinical application value.

Identification of Critical Genes and lncRNAs in Osteolysis after Total Hip Arthroplasty and Osteoarthritis by RNA Sequencing

Total hip arthroplasty (THA) is a cost-effective treatment for osteoarthritis (OA), and osteolysis is a common complication of THA. This study was aimed at exploring the relevant molecular biomarkers for osteolysis after THA. We performed RNA sequence to identify and characterize expressed mRNAs and lncRNAs in OA and osteolysis. Differentially expressed mRNAs (DEmRNAs) and lncRNAs (DElncRNAs) in OA and osteolysis were acquired, as well as shared DEmRNAs/DElncRNAs in OA and osteolysis and osteolysis-specific DEmRNAs/DElncRNAs. Then, shared and osteolysis-specific DElncRNA-DEmRNA coexpression networks were constructed to further investigate the function of DElncRNAs and DEmRNAs in OA and osteolysis. In total, 343 DEmRNAs and 25 DElncRNAs in OA, 908 DEmRNAs and 107 DElncRNAs in osteolysis, and 406 DEmRNAs and 46 DElncRNAs between OA and osteolysis were acquired. A total of 136 shared DEmRNAs and 9 shared DElncRNAs in OA and osteolysis and 736 osteolysis-specific DEmRNAs and 103 osteolysis-specific DElncRNAs were acquired. Then, 128 shared DElncRNA-DEmRNA coexpression pairs and 522 osteolysis-specific DElncRNA-DEmRNA coexpression pairs were identified. The present study highlighted the roles of four interaction pairs, including two shared lncRNA-mRNA interaction pairs in OA and osteolysis (AC111000.4 and AC016831.6), which may function in the immune process of OA and osteolysis by regulating CD8A and CD8B, respectively, and two osteolysis-specific interaction pairs (AC090607.4-FOXO3 and TAL1-ABALON), which may play an important role in osteoclastogenesis.

Metallic wear debris collected from patients induces apoptosis in rat primary osteoblasts via reactive oxygen species‑mediated mitochondrial dysfunction and endoplasmic reticulum stress

Although total hip arthroplasty is considered to be an effective surgical procedure for treating hip joint diseases, it is hindered by implant wear debris, which induces aseptic loosening. Various cell types are involved in this pathogenesis; however, the interactions between wear debris and osteoblasts, which serve a crucial role in bone formation, have not been clearly illustrated. In the present study, minor metallic wear particles were collected from the interfacial membrane around loosened implants of patients, and the biological effects of these particles on rat primary osteoblasts were then explored. The results demonstrated that metallic wear debris was able to induce the apoptosis of treated cells in a concentration- and time-dependent manner. Furthermore, it was identified that reactive oxygen species (ROS) generation increased, the mitochondrial membrane potential collapsed, and the mitochondria-caspase-dependent and endoplasmic reticulum (ER) stress apoptotic pathways were activated following metallic wear debris application. In addition, apoptosis and associated pathways were inhibited by the use of N-acetyl-L-cysteine, an antioxidant that suppresses ROS production, indicating that the ROS generation triggered ER stress, mitochondrial dysfunction and downstream cascades that contributed to cell apoptosis. These findings suggest that metallic wear debris-induced ROS serve an important role in the apoptosis of osteoblasts. This provides a valuable insight, not only into understanding the mechanisms underlying the involvement of osteoblasts in osteolysis, but also into a potential novel therapeutic approach to treat implant aseptic loosening.

Preferential CD8 rather than CD4 T-cell response to wear particles of polyether-ether-ketone and highly cross-linked polyethylene

The efficacy of polyether-ether-ketone (PEEK) as a bearing material in knee components, a potential alternative to the currently used highly cross-linked polyethylene (HXLPE), has attracted a lot of attention recently. This study aimed to systematically assess the effect of particulate wear debris on CD4 and CD8 T-cell responses. HXLPE and PEEK particles (96% less than 5 μm) were generated by custom cryo-milling and pulverization in liquid nitrogen, and then incubated with blood collected from 25 donors. The phenotypes of the T-cells were systematically analyzed by immunostaining and flow cytometry. For the in vivo study, 0.1 mL of each particle suspension (about 1.0 × 10⁸ wear particles) was injected into murine knee joints; the synovium and spleen were collected one week later for histological examination and immunofluorescence staining. PEEK and HXLPE particles did not induce CD4+ T-cell responses; however, CD8+ T-cells might be involved in mediating particle-induced reactions. The T-cell and inflammatory responses induced by PEEK and HXLPE particles were comparable. Further investigations into the frictional properties of materials should be performed to expand on our results.

Enriching the understanding of the effects of the particles on the adaptive immune response.

Effects of wear particles of polyether-ether-ketone and cobalt-chromium-molybdenum on CD4- and CD8-T-cell responses

T-cells, second only to macrophages, are often considered as the potential cells involved in debris-related failure of arthroplasty. Here, we assessed the effects of particulate wear debris on T-cells and inflammatory reactions. Blood samples from 25 donors were incubated with polyether-ether-ketone (PEEK) and cobalt-chromium-molybdenum (CoCrMo) particles generated by custom cryo-milling and pulverization. The T-cell phenotypes were assessed using immunostaining and flow cytometry. For the in vivo study, 0.1 mL of each particle suspension (approximately 1.0 × 10⁸ wear particles) was injected into murine knee joints; the synovium and spleen were collected one week after the operation for histological examination and immunofluorescence staining. The T-cell responses observed included low-level activation of Th1, Th2, Th17, and CD8+ pathways after 72 h of co-culture of the particles with peripheral blood mononuclear cells. Obvious CD8+ T-cell responses were observed in local synovium and peripheral spleen, with higher inflammatory cytokine expression in the CoCrMo group. Relatively minor cytotoxic and immunological reactions were observed in vitro, with PEEK and CoCrMo particle-induced immune responses being primarily mediated by CD8+ T-cells, rather than CD4+ T-cells, in vivo. Overall, PEEK wear particles induced fewer inflammatory reactions than CoCrMo particles. This study verified that PEEK was suitable as a potential alternative for metals in total knee replacements in terms of the immunological reaction to PEEK particles, and shed light on the effects of wear particles from polymer and metal-based implants on immune responses.

Case Series With Histopathologic and Radiographic Analyses Following Failure of Fresh Osteochondral Allografts of the Talus

BACKGROUND

Fresh osteochondral allografting of the talus is one treatment option for large chondral defects. Following positive early term results, failure rates of up to 35% have been reported. A retrieval study was performed to characterize failed talar allografts.

METHODS

Failed fresh osteochondral allografts of the talus were retrieved on revision. Cases of deep infection were excluded. After tissue fixation, samples were decalcified, embedded, and stained with Safranin-O/Fast Green, osteocalcin, tumor necrosis factor alpha (TNF-α), CD4, CD8, and CD68. Slides were graded according to the modified Mankin scoring system or severity scale. Medical record review was performed.

RESULTS

Eight allografts (7 patients) were retrieved from patients, following an average term of implantation of 31 months (range, 12-58). There were 3 types of allografts in this series (hemidome, n=5; segmental, n=2; bipolar, n=1). Reasons for transplantation were post-traumatic arthritis or osteonecrosis; reasons for revision were graft failure/collapse, nonunion, progressive arthritis, and/or pain. Prior to revision, all grafts exhibited collapse and subchondral lucencies. At the graft host interface, Safranin-O staining demonstrated substantial loss of sulfated glycosaminoglycans, Osteocalcin immunostaning was nearly absent, CD68 (indicating osteoclast activity) was predominantly exhibited, and CD4+ helper T cells as well as CD8+ cytotoxic T cells and NK cells-cell types commonly implicated in allogeneic organ transplant rejection-were found in high concentrations. TNF-α was present throughout the graft.

CONCLUSION

A histopathologic analysis of 8 retrieved, failed talar allografts was performed. Graft failure appeared to be primarily biologic, with an extensive loss of viable cartilaginous and osseous tissue at the graft-host interface. This study provides the first evidence of a potential CD4+ and CD8+ lymphocyte-mediated failure mechanism in fresh osteochondral allografts that were revised following collapse.

LEVEL OF EVIDENCE

Level IV, case series.

Endotoxins in surgical instruments of hip arthroplasty

Abstract OBJECTIVE To investigate endotoxins in sterilized surgical instruments used in hip arthroplasties. METHOD A descriptive exploratory study conducted in a public teaching hospital. Six types of surgical instruments were selected, namely: acetabulum rasp, femoral rasp, femoral head remover, chisel box, flexible bone reamer and femoral head test. The selection was based on the analysis of the difficulty in removing bone and blood residues during cleaning. The sample was made up of 60 surgical instruments, which were tested for endotoxins in three different stages. The EndosafeTM Gel-Clot LAL (Limulus Amebocyte Lysate method) was used. RESULT There was consistent gel formation with positive analysis in eight instruments, corresponding to 13.3%, being four femoral rasps and four bone reamers. CONCLUSION Endotoxins in quantity ≥0.125 UE/mL were detected in 13.3% of the instruments tested.

Immune response in adverse reactions to metal debris following metal-on-metal total hip arthroplasty

BACKGROUND

The purpose of the present study was to determine whether T cell-mediated type IV hypersensitivity reactions could be a major cause of adverse reaction to metal debris (ARMD) after metal-on-metal total hip arthroplasty (THA).

METHODS

Thirteen patients (1 man and 12 women; mean age 68 years, age range 60 to 83 years) with ARMD underwent revision surgery following metal-on-metal THA (15 hips). Lymphocyte stimulation testing was conducted. Periprosthetic tissue specimens underwent immunohistochemical studies.

RESULTS

Lymphocyte stimulation testing showed that five patients were nickel-sensitive, and one patient was also cobalt-sensitive. Immunohistochemical studies showed that T cells were dominant in five hips, and B cells were dominant in 10 hips. In four of the five patients with a positive lymphocyte stimulation test, the dominant lymphocytes were T cells, suggesting type IV hypersensitivity. The major cause of ARMD was not type IV hypersensitivity in the remaining nine patients.

CONCLUSION

Metal hypersensitivity does not appear to be the dominant biological reaction involved in the occurrence of ARMD.

Contributions of human tissue analysis to understanding the mechanisms of loosening and osteolysis in total hip replacement

Aseptic loosening and osteolysis are the most frequent late complications of total hip arthroplasty (THA) leading to revision of the prosthesis. This review aims to demonstrate how histopathological studies contribute to our understanding of the mechanisms of aseptic loosening/osteolysis development. Only studies analysing periprosthetic tissues retrieved from failed implants in humans were included. Data from 101 studies (5532 patients with failure of THA implants) published in English or German between 1974 and 2013 were included. "Control" samples were reported in 45 of the 101 studies. The most frequently examined tissues were the bone-implant interface membrane and pseudosynovial tissues. Histopathological studies contribute importantly to determination of key cell populations underlying the biological mechanisms of aseptic loosening and osteolysis. The studies demonstrated the key molecules of the host response at the protein level (chemokines, cytokines, nitric oxide metabolites, metalloproteinases). However, these studies also have important limitations. Tissues harvested at revision surgery reflect specifically end-stage failure and may not adequately reveal the evolution of pathophysiological events that lead to prosthetic loosening and osteolysis. One possible solution is to examine tissues harvested from stable total hip arthroplasties that have been revised at various time periods due to dislocation or periprosthetic fracture in multicenter studies.

The pathology of orthopedic implant failure is mediated by innate immune system cytokines

All of the over 1 million total joint replacements implanted in the US each year are expected to eventually fail after 15–25 years of use, due to slow progressive subtle inflammation at the bone implant interface. This inflammatory disease state is caused by implant debris acting, primarily, on innate immune cells, that is, macrophages. This slow progressive pathological bone loss or “aseptic loosening” is a potentially life-threatening condition due to the serious complications in older people (>75 yrs) of total joint replacement revision surgery. In some people implant debris (particles and ions from metals) can influence the adaptive immune system as well, giving rise to the concept of metal sensitivity. However, a consensus of studies agrees that the dominant form of this response is due to innate reactivity by macrophages to implant debris where both danger (DAMP) and pathogen (PAMP) signalling elicit cytokine-based inflammatory responses. This paper discusses implant debris induced release of the cytokines and chemokines due to activation of the innate (and the adaptive) immune system and the subsequent formation of osteolysis. Different mechanisms of implant-debris reactivity related to the innate immune system are detailed, for example, danger signalling (e.g., IL-1β, IL-18, IL-33, etc.), toll-like receptor activation (e.g., IL-6, TNF-α, etc.), apoptosis (e.g., caspases 3–9), bone catabolism (e.g., TRAP5b), and hypoxia responses (Hif1-α). Cytokine-based clinical and basic science studies are in progress to provide diagnosis and therapeutic intervention strategies.

T cells from chronic bone infection show reduced proliferation and a high proportion of CD28⁻ CD4 T cells

Chronic bone infection is associated with bone resorption. From animal studies, CD3/CD28-activated T cells are known to enhance osteoclastogenesis and bone resorption. Because CD28 is expressed constitutively on T cells and its expression is down-regulated by chronic exposure to the inflammatory environment, we characterized co-stimulatory molecule expression on T cells from chronically infected patients. We used cytofluorometric techniques to phenotypically characterize T cells, its co-stimulatory molecules and perforin secretion from infected and non-infected human bones. Chronic bone infection was defined as infection lasting for more than a month. We show a higher T cell activation [human leucocyte antigen D-related (HLA-DR⁺)] in infected compared to non-infected bones: median being 16 versus 7%, P = 0·009 for CD4 T cells, and 33 versus 15%, P = 0·038 for CD8 T cells, respectively. However, T cell proliferation (Ki67⁺) was lower for CD8 T cells in infected bones: 26 versus 34%, P = 0·045. In contrast, we detected no difference in apoptosis and regulatory T cells. In infected bone, we found higher CD28-negative CD4⁺ T cells compared to non-infected bone: 20 versus 8%, respectively (P = 0·005); this T cell subset had higher CD11b expression and perforin secretion. Chronically infected human bones are characterized by an increase of CD28-negative CD4⁺ T cells, indicating long-term activated cells with cytotoxic ability. Therefore, this alteration of co-stimulatory molecules may modify interactions with osteoclasts and impact bone resorption.

Polyethylene particles stimulate expression of ITAM-related molecules in peri-implant tissues and when stimulating osteoclastogenesis in vitro

Wear particle-induced orthopaedic prosthesis loosening is associated with elevated osteoclast activity. The immunoreceptor tyrosine-based activation motif (ITAM)-related molecules OSCAR, FcRγ, TREM2 and DAP12 are important for osteoclast formation. The aim of this study was to determine if these molecules are involved in peri-implant loosening by investigating their expression in peri-implant tissues obtained at revision of joint replacement components containing polyethylene (PE) wear particles, and in osteoclasts formed in vitro in the presence of PE particles. The results showed that there was a marked and statistically significant increase in protein levels of the ITAM-related molecules in the revision tissues. The levels of OSCAR, FcRγ, TREM2 and DAP12 mRNA in the revision tissues were also increased. In vitro PE particles stimulated osteoclast resorption in the presence of 50 ng ml(-1) receptor activator NFκB (RANKL) and significantly elevated the expression of OSCAR, FcRγ, TREM2 and DAP12 during osteoclast formation. These findings suggest that the ITAM signalling molecules and their co-receptors have a role in pathogenic bone loss associated with implant PE wear.

Osteoclastogenesis in peripheral blood mononuclear cell cultures of periprosthetic osteolysis patients and the phenotype of T cells localized in periprosthetic tissues

Arthroplasty is a very successful medical procedure. Failures depend on aseptic loosening caused by periprosthetic osteolysis, where T cells have a contradictory role. We analyzed osteoclastogenesis in peripheral blood mononuclear cell (PBMC) cultures of periprosthetic osteolysis patients and the phenotype of T cells localized in periprosthetic tissues. We enrolled 45 subjects with periprosthetic osteolysis (15), stable prosthesis (15) and healthy controls (15). We performed PBMC cultures to study osteoclastogenesis. Osteoclasts and T cell phenotype were examined by immunohistochemistry, immunofluorescence and flow citometry. Periprosthetic osteolysis patients showed spontaneous osteoclastogenesis, which was inhibited by RANK-Fc and T cell depletion. In periprosthetic osteolysis patients' PBMC cultures, CD4 and CD8 T cells increased and CD8 T cells did not express CD25. In periprosthetic tissues T cells were close to osteoclasts, suggesting their interaction. Local CD8 T cells showed a regulatory phenotype, expressing CD25 and FoxP3, while CD4 T cells did not express activation markers. Our data suggest that, in an early stage of periprosthetic osteolysis, T cells may promote osteoclastogenesis, whereas subsequently osteoclasts activate FoxP3/CD8 T cells, which inhibit CD4 effector T cells. This mechanism may explain the previous finding of non-active T cells in periprosthetic tissues.

Targeting extracellular signal-regulated kinase (ERK) signaling has therapeutic implications for inflammatory osteolysis

The extracellular signal-regulated kinase 1/2 (ERK) pathway, part of the mitogen-activated protein kinase (MAPK) family, is well-known for its role in cell differentiation and proliferation. In the context of osteoclastogenesis, macrophage colony stimulating factor (M-CSF) is an upstream activator of ERK signals for the survival of osteoclast precursors prior to their differentiation into multinucleated osteoclasts. In this study, we demonstrate by using both in vivo and in vitro models that the ERK signaling pathway involves an inflammatory response of various cells mediating osteolysis. Osteoblasts exhibit innate immune response by expressing M-CSF in response to lipopolysaccharide (LPS). LPS induced M-CSF expression is mediated by ERK. The inhibition of ERK signaling attenuated the inflammatory response to LPS both in vivo and in vitro. Thus, the ERK pathway may be a potentially important therapeutic target in the treatment of inflammatory osteolysis.