ZCCHC3 is a stress granule zinc knuckle protein that strongly suppresses LINE-1 retrotransposition.

Retrotransposons have generated about half of the human genome and LINE-1s (L1s) are the only autonomously active retrotransposons. The cell has evolved an arsenal of defense mechanisms to protect against retrotransposition with factors we are only beginning to understand. In this study, we investigate Zinc Finger CCHC-Type Containing 3 (ZCCHC3), a gag-like zinc knuckle protein recently reported to function in the innate immune response to infecting viruses. We show that ZCCHC3 also severely restricts human retrotransposons and associates with the L1 ORF1p ribonucleoprotein particle. We identify ZCCHC3 as a bona fide stress granule protein, and its association with LINE-1 is further supported by colocalization with L1 ORF1 protein in stress granules, dense cytoplasmic aggregations of proteins and RNAs that contain stalled translation pre-initiation complexes and form when the cell is under stress. Our work also draws links between ZCCHC3 and the anti-viral and retrotransposon restriction factors Mov10 RISC Complex RNA Helicase (MOV10) and Zinc Finger CCCH-Type, Antiviral 1 (ZC3HAV1, also called ZAP). Furthermore, collective evidence from subcellular localization, co-immunoprecipitation, and velocity gradient centrifugation connects ZCCHC3 with the RNA exosome, a multi-subunit ribonuclease complex capable of degrading various species of RNA molecules and that has previously been linked with retrotransposon control.

C9orf72-associated SMCR8 protein binds in the ubiquitin pathway and with proteins linked with neurological disease.

A pathogenic GGGCCC hexanucleotide expansion in the first intron/promoter region of the C9orf72 gene is the most common mutation associated with amyotrophic lateral sclerosis (ALS). The C9orf72 gene product forms a complex with SMCR8 (Smith-Magenis Syndrome Chromosome Region, Candidate 8) and WDR41 (WD Repeat domain 41) proteins. Recent studies have indicated roles for the complex in autophagy regulation, vesicle trafficking, and immune response in transgenic mice, however a direct connection with ALS etiology remains unclear. With the aim of increasing understanding of the multi-functional C9orf72-SMCR8-WDR41 complex, we determined by mass spectrometry analysis the proteins that directly associate with SMCR8. SMCR8 protein binds many components of the ubiquitin-proteasome system, and we demonstrate its poly-ubiquitination without obvious degradation. Evidence is also presented for localization of endogenous SMCR8 protein to cytoplasmic stress granules. However, in several cell lines we failed to reproduce previous observations that C9orf72 protein enters these granules. SMCR8 protein associates with many products of genes associated with various Mendelian neurological disorders in addition to ALS, implicating SMCR8-containing complexes in a range of neuropathologies. We reinforce previous observations that SMCR8 and C9orf72 protein levels are positively linked, and now show in vivo that SMCR8 protein levels are greatly reduced in brain tissues of C9orf72 gene expansion carrier individuals. While further study is required, these data suggest that SMCR8 protein level might prove a useful biomarker for the C9orf72 expansion in ALS.

Top 100 most cited articles in orthopaedic surgery: An update.

INTRODUCTION: As the research landscape evolves, we sought to investigate the current most cited Orthopaedic Surgery articles and compare these to previously cited articles. METHODS: Web of Science database screened orthopaedic journal articles with comparison to previous data using multivariate regression analysis. RESULTS: Rate of citations increased 172% within the last decade. Previous rank and citations within the last decade had a greater effect on contemporary rank (p = 0.084, p = 0.002, respectively). CONCLUSION: Trends in investigative research can shift by the next decade. Previous citation rank and citations in last decade contributed most to current rank.

Patella Baja in Total Knee Arthroplasty.

Patella baja in total knee arthroplasty can result in impingement, pain, and decreased range of motion. Etiology can range from previous knee surgeries such as anterior cruciate ligament reconstruction, retrograde femoral nail, infrapatellar fat pad resection, and previous total knee arthroplasty. Diagnosis can be confirmed by one of a number of measurements of patellar height including Insall-Salvati and Blackburne-Peel ratios. It is important to differentiate between true patella baja and pseudopatella baja by patellar height ratio. Treatment includes correct identification of the underlying etiology and appropriate management. Surgical management strategies include tibial tubercle osteotomy, distal femoral augment and revision, proximalization of the patellar component, modification of the anterior tibial component, and/or Z-plasty of the patellar tendon. We review the outcomes for each of these procedures.

External iliac vein compression secondary to osteolysis-induced hematoma in total hip arthroplasty.

A 62-year-old man with a history of right total hip arthroplasty, who was managed conservatively for moderate osteolysis, presented with acute-onset, painless, significant, and diffuse right lower extremity edema. Initial laboratory markers were negative for infection. Advanced imaging demonstrated a complex extrapelvic fluid mass along the psoas sheath causing compression of the external iliac vein. Intraoperatively, significant hematoma was removed from the iliopsoas sheath, followed by metal head and liner exchange as well as bone grafting of the osteolytic defects adjacent to the hip implant. Postoperative imaging showed adequate decompression, no deep vein thrombosis, and a patent external iliac vein. At 2 weeks, postoperative swelling completely resolved. At 3 months, the patient recovered to normal baseline level and underwent contralateral total hip arthroplasty for symptomatic osteoarthritis.

A human endogenous retrovirus encoded protease potentially cleaves numerous cellular proteins.

BACKGROUND: A considerable portion of the human genome derives from retroviruses inherited over millions of years. Human endogenous retroviruses (HERVs) are usually severely mutated, yet some coding-competent HERVs exist. The HERV-K(HML-2) group includes evolutionarily young proviruses that encode typical retroviral proteins. HERV-K(HML-2) has been implicated in various human diseases because transcription is often upregulated and some of its encoded proteins are known to affect cell biology. HERV-K(HML-2) Protease (Pro) has received little attention so far, although it is expressed in some disease contexts and other retroviral proteases are known to process cellular proteins. RESULTS: We set out to identify human cellular proteins that are substrates of HERV-K(HML-2) Pro employing a modified Terminal Amine Isotopic Labeling of Substrates (TAILS) procedure. Thousands of human proteins were identified by this assay as significantly processed by HERV-K(HML-2) Pro at both acidic and neutral pH. We confirmed cleavage of a majority of selected human proteins in vitro and in co-expression experiments in vivo. Sizes of processing products observed for some of the tested proteins coincided with product sizes predicted by TAILS. Processed proteins locate to various cellular compartments and participate in diverse, often disease-relevant cellular processes. A limited number of HERV-K(HML-2) reference and non-reference loci appears capable of encoding active Pro. CONCLUSIONS: Our findings from an approach combining TAILS with experimental verification of candidate proteins in vitro and in cultured cells suggest that hundreds of cellular proteins are potential substrates of HERV-K(HML-2) Pro. It is therefore conceivable that even low-level expression of HERV-K(HML-2) Pro affects levels of a diverse array of proteins and thus has a functional impact on cell biology and possible relevance for human diseases. Further studies are indicated to elucidate effects of HERV-K(HML-2) Pro expression regarding human substrate proteins, cell biology, and disease. The latter also calls for studies on expression of specific HERV-K(HML-2) loci capable of encoding active Pro. Endogenous retrovirus-encoded Pro activity may also be relevant for disease development in species other than human.

Properties of LINE-1 proteins and repeat element expression in the context of amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease involving loss of motor neurons and having no known cure and uncertain etiology. Several studies have drawn connections between altered retrotransposon expression and ALS. Certain features of the LINE-1 (L1) retrotransposon-encoded ORF1 protein (ORF1p) are analogous to those of neurodegeneration-associated RNA-binding proteins, including formation of cytoplasmic aggregates. In this study we explore these features and consider possible links between L1 expression and ALS. RESULTS: We first considered factors that modulate aggregation and subcellular distribution of LINE-1 ORF1p, including nuclear localization. Changes to some ORF1p amino acid residues alter both retrotransposition efficiency and protein aggregation dynamics, and we found that one such polymorphism is present in endogenous L1s abundant in the human genome. We failed, however, to identify CRM1-mediated nuclear export signals in ORF1p nor strict involvement of cell cycle in endogenous ORF1p nuclear localization in human 2102Ep germline teratocarcinoma cells. Some proteins linked with ALS bind and colocalize with L1 ORF1p ribonucleoprotein particles in cytoplasmic RNA granules. Increased expression of several ALS-associated proteins, including TAR DNA Binding Protein (TDP-43), strongly limits cell culture retrotransposition, while some disease-related mutations modify these effects. Using quantitative reverse transcription PCR (RT-qPCR) of ALS tissues and reanalysis of publicly available RNA-Seq datasets, we asked if changes in expression of retrotransposons are associated with ALS. We found minimal altered expression in sporadic ALS tissues but confirmed a previous report of differential expression of many repeat subfamilies in C9orf72 gene-mutated ALS patients. CONCLUSIONS: Here we extended understanding of the subcellular localization dynamics of the aggregation-prone LINE-1 ORF1p RNA-binding protein. However, we failed to find compelling evidence for misregulation of LINE-1 retrotransposons in sporadic ALS nor a clear effect of ALS-associated TDP-43 protein on L1 expression. In sum, our study reveals that the interplay of active retrotransposons and the molecular features of ALS are more complex than anticipated. Thus, the potential consequences of altered retrotransposon activity for ALS and other neurodegenerative disorders are worthy of continued investigation.

Mortality During Total Knee Periprosthetic Joint Infection.

BACKGROUND: Periprosthetic joint infections (PJIs) are fraught with multiple complications including poor patient-reported outcomes, disability, reinfection, disarticulation, and even death. We sought to perform a systematic review asking the question: (1) What is the mortality rate of a PJI of the knee undergoing 2-stage revision for infection? (2) Has this rate improved over time? (3) How does this compare to a normal cohort of individuals? METHODS: We performed a database search in MEDLINE/EMBASE, PubMed, and all relevant reference studies using the following keywords: "periprosthetic joint infection," "mortality rates," "total knee arthroplasty," and "outcomes after two stage revision." Two hundred forty-two relevant studies and citations were identified, and 14 studies were extracted and included in the review. RESULTS: A total of 20,719 patients underwent 2-stage revision for total knee PJI. Average age was 66 years. Mean mortality percentage reported was 14.4% (1.7%-34.0%) with average follow-up 3.8 years (0.25-9 years). One-year mortality rate was 4.33% (3.14%-5.51%) after total knee PJI with an increase of 3.13% per year mortality thereafter (r = 0.76 [0.49, 0.90], P < .001). Five-year mortality was 21.64%. When comparing the national age-adjusted mortality (Actuarial Life Table) and the reported 1-year mortality risk in this meta-analysis, the risk of death after total knee PJI is significantly increased, with an odds ratio of 3.05 (95% confidence interval, 2.69-3.44; P < .001). CONCLUSION: The mortality rate after 2-stage total knee revision for infection is very high. When counseling a patient regarding complications of this disease, death should be discussed.

Transcriptional profiling of HERV-K(HML-2) in amyotrophic lateral sclerosis and potential implications for expression of HML-2 proteins.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder. About 90% of ALS cases are without a known genetic cause. The human endogenous retrovirus multi-copy HERV-K(HML-2) group was recently reported to potentially contribute to neurodegeneration and disease pathogenesis in ALS because of transcriptional upregulation and toxic effects of HML-2 Envelope (Env) protein. Env and other proteins are encoded by some transcriptionally active HML-2 loci. However, more detailed information is required regarding which HML-2 loci are transcribed in ALS, which of their proteins are expressed, and differences between the disease and non-disease states. METHODS: For brain and spinal cord tissue samples from ALS patients and controls, we identified transcribed HML-2 loci by generating and mapping HML-2-specific cDNA sequences. We predicted expression of HML-2 env gene-derived proteins based on the observed cDNA sequences. Furthermore, we determined overall HML-2 transcript levels by RT-qPCR and investigated presence of HML-2 Env protein in ALS and control tissue samples by Western blotting. RESULTS: We identified 24 different transcribed HML-2 loci. Some of those loci are transcribed at relatively high levels. However, significant differences in HML-2 loci transcriptional activities were not seen when comparing ALS and controls. Likewise, overall HML-2 transcript levels, as determined by RT-qPCR, were not significantly different between ALS and controls. Indeed, we were unable to detect full-length HML-2 Env protein in ALS and control tissue samples despite reasonable sensitivity. Rather our analyses suggest that a number of HML-2 protein variants other than full-length Env may potentially be expressed in ALS patients. CONCLUSIONS: Our results expand and refine recent publications on HERV-K(HML-2) and ALS. Some of our results are in conflict with recent findings and call for further specific analyses. Our profiling of HML-2 transcription in ALS opens up the possibility that HML-2 proteins other than canonical full-length Env may have to be considered when studying the role of HML-2 in ALS disease.

Effects of fondaparinux on wound drainage after total hip and knee arthroplasty.

BACKGROUND: The purpose of this investigation was to determine the effects of fondaparinux on postoperative wound drainage, length of hospital stay (LOS) and rate of surgical site infection in total joint patients. METHODS: 117 patients undergoing total joint arthroplasty treated with fondaparinux for venous thromboembolism (VTE) prophylaxis were prospectively studied. RESULTS: The average time to a dry wound was 3.4 days, with an average LOS of 3.77 days. Perioperative complications included 2 cases each of superficial cellulitis, deep vein thrombosis, and pulmonary embolism; there were no cases of deep infection. Multi-variate analysis showed increased patient BMI increased LOS (p = 0.0169). CONCLUSION: Fondaparinux is an effective drug for VTE prophylaxis in total joint arthroplasty with wound drainage and LOS comparable to historical controls of enoxaparin, warfarin, and rivaroxaban.

Local bio-absorbable antibiotic delivery in calcium sulfate beads in hip and knee arthroplasty.

Antibiotic-impregnated calcium sulfate (AICS) beads have been used for prevention and treatment of periprosthetic joint infections. We evaluated post-operative complications following the use of AICS beads. 56 patients undergoing complex primary or revision hip or knee arthroplasty received antibiotic calcium sulfate beads. Primary outcomes were wound complication rates. Secondary outcomes included reoperation and reinfection rates. One case (1.7%) of persistent wound drainage occurred requiring surgical irrigation and a poly-exchange. No post-operative infections were seen. Use of 100% pure calcium sulfate AICS beads may help reduce post-operative wound complications. AICS appears to be a safe adjunct tool in local antibiotic delivery.

Self-Resolution of a Draining Sinus Tract in a Patient with Chronic Periprosthetic Hip Infection.

We report a novel case of a patient who had a draining sinus soon after a total hip arthroplasty that spontaneously resolved. The patient voluntarily discontinued antibiotic suppressive therapy (AST) after 10 years of treatment and paradoxically experienced full resolution of signs of chronic prosthetic joint infection (PJI), including recovery of his left-sided draining sinus tract. Now 8 years after discontinuing AST, the patient has no pain, good function, and no major or minor criteria of joint infection according to the Musculoskeletal Infection Society (MSIS) workgroup. The authors have not identified literature describing a similar resolution of draining sinus tracts from around a prosthetic joint after discontinuing AST. Despite the resolution of this patient's sinus tract, the authors do not advocate for discontinuing AST in patients with a draining sinus tract. However, in spite of the fact that the MSIS consensus statement suggests that a draining sinus is a sure sign of PJI and that the assumption is that the infection will not go away until explant, this case was different.

Calculating the Position of the Joint Line of the Knee Using Anatomical Landmarks.

Restoration of the joint line of the knee during primary and revision total knee arthroplasty is a step that directly influences patient outcomes. In revision total knee arthroplasty, necessary bony landmarks may be missing or obscured, so there remains a lack of consensus on how to accurately identify and restore the joint line of the knee. In this study, 50 magnetic resonance images of normal knees were analyzed to determine a quantitative relationship between the joint line of the knee and 6 bony landmarks: medial and lateral femoral epicondyles, medial and lateral femoral metaphyseal flares, tibial tubercle, and proximal tibio-fibular joint. Wide variability was found in the absolute distance from each landmark to the joint line of the knee, including significant differences between the sexes. Normalization of the absolute distances to femoral or tibial diameters revealed reliable spatial relationships to the joint line of the knee. The joint line was found to be equidistant from the lateral femoral epicondyle and the proximal tibio-fibular joint, representing a reproducible point of reference for joint line restoration. The authors propose a simple 3-step algorithm that can be used with magnetic resonance imaging, computed tomography, or radiography to reliably determine the anatomical location of the joint line of the knee relative to the surrounding bony anatomy. [Orthopedics. 2016; 39(6):381-386.].

Metal in Total Hip Arthroplasty: Wear Particles, Biology, and Diagnosis.

Total hip arthroplasty (THA) has been performed for nearly 50 years. Between 2006 and 2012, more than 600,000 metal-on-metal THA procedures were performed in the United States. This article reviews the production of metal wear debris in a metal-on-metal articulation and the interaction of cobalt and chromium ions that ultimately led to a dramatic decline in the use of metal-on-metal THA articulations. Additionally, the article reviews mechanisms of metal wear, the biologic reaction to cobalt and chromium ions, the clinical presentation of failing metal-on-metal articulations, and current diagnostic strategies. Further, the article discusses the use of inflammatory markers, metal ion levels, radiographs, metal artifact reduction sequence magnetic resonance imaging, and ultrasound for failed metal-on-metal THA procedures. When adopting new technologies, orthopedic surgeons must weigh the potential increased benefits against the possibility of new mechanisms of failure. Metal-on-metal bearings are a prime example of the give and take between innovation and clinical results, especially in the setting of an already successful procedure such as THA. [Orthopedics. 2016; 39(6):371-379.].

The Broad-Spectrum Antiviral Protein ZAP Restricts Human Retrotransposition.

Intrinsic immunity describes the set of recently discovered but poorly understood cellular mechanisms that specifically target viral pathogens. Their discovery derives in large part from intensive studies of HIV and SIV that revealed restriction factors acting at various stages of the retroviral life cycle. Recent studies indicate that some factors restrict both retroviruses and retrotransposons but surprisingly in ways that may differ. We screened known interferon-stimulated antiviral proteins previously untested for their effects on cell culture retrotransposition. Several factors, including BST2, ISG20, MAVS, MX2, and ZAP, showed strong L1 inhibition. We focused on ZAP (PARP13/ZC3HAV1), a zinc-finger protein that targets viruses of several families, including Retroviridae, Tiloviridae, and Togaviridae, and show that ZAP expression also strongly restricts retrotransposition in cell culture through loss of L1 RNA and ribonucleoprotein particle integrity. Association of ZAP with the L1 ribonucleoprotein particle is supported by co-immunoprecipitation and co-localization with ORF1p in cytoplasmic stress granules. We also used mass spectrometry to determine the protein components of the ZAP interactome, and identified many proteins that directly interact and colocalize with ZAP, including MOV10, an RNA helicase previously shown to suppress retrotransposons. The detection of a chaperonin complex, RNA degradation proteins, helicases, post-translational modifiers, and components of chromatin modifying complexes suggest mechanisms of ZAP anti-retroelement activity that function in the cytoplasm and perhaps also in the nucleus. The association of the ZAP ribonucleoprotein particle with many interferon-stimulated gene products indicates it may be a key player in the interferon response.

The pros and cons of using larger femoral heads in total hip arthroplasty.

With the introduction of improved bearing surfaces for total hip arthroplasty (THA) has come a reintroduction of larger femoral heads with the promise of reducing the rate of hip instability and increasing hip range of motion (ROM). The size of femoral heads used for THA ranges from 22 to 40 mm, and even larger heads are used for hip resurfacing. With accurately positioned components, larger heads reduce the hip instability rate and theoretically increase hip ROM. However, for any given bearing surface, the volumetric wear rate is higher for larger heads than for smaller heads, which potentially jeopardizes the long-term survival of these reconstructions. In this article, we review the evidence for use of larger femoral heads with respect to stability, ROM, impingement, wear rate, bearing surfaces, and future directions.

Identification of the landmark registration safe zones during total knee arthroplasty using an imageless navigation system.

Incorrect registration during computer assisted total knee arthroplasty (CA-TKA) leads to malposition of implants. Our aim was to evaluate the tolerable error in anatomic landmark registration. We incorrectly registered the femoral epicondyles, femoral and tibial centers, as well as the malleoli and documented the change in angulation or rotation. We found that the distal femoral epicondyles were the most difficult anatomic landmarks to register. The other bony landmarks were more forgiving. Identification of the distal femoral epicondyles has a high inter-observer and intra-observer variability. Our observation that there is less than 2mm of safe zone in the anterior or posterior direction during registration of the medial and lateral epicondyles may explain the inability of CA-TKA to improve upon the outcomes of conventional TKA.

Kinematics of the stiff total knee arthroplasty.

The kinematics of 10 total knee replacements with poor flexion (<90 degrees ) were compared with 11 replacements with good flexion (>110 degrees ) at a mean of 3 years from surgery using optical calibration with implant shape-matching techniques from radiographs taken in standing, early-lunge, and late-lunge positions. There were no significant differences between groups in anteroposterior translation of the medial and lateral femoral condyles or tibial rotation during standing and early lunge. Groups differed in amount of posterior translation of the femoral condyles during late lunge because of the poor-flexion group's inability to achieve the same amount of flexion as the good-flexion group. Poor flexion after total knee arthroplasty, we conclude, is not associated with abnormal kinematics in the setting of well-aligned, well-fixed implants.

Comparison of outcomes of using spinal versus general anesthesia in total hip arthroplasty.

Blood loss, operative time, and rate of complications were compared in 606 patients undergoing primary unilateral total hip arthroplasty with either spinal anesthesia (SA) or general anesthesia (GA). Patients were followed for 2 years after surgery. Compared with GA, SA resulted in mean reductions of 12% in operative time, 25% in estimated intraoperative blood loss, 38% in rate of operative blood loss, and 50% in intraoperative transfusion requirements. Compared with patients receiving GA, patients receiving SA had higher hemoglobin levels on postoperative days 1 and 2 and a 20% lower total transfusion requirement. SA appears superior to GA for this procedure.