RIPK1 and Caspase-8 Ensure Chromosome Stability Independently of Their Role in Cell Death and Inflammation.

Receptor-interacting protein kinase (RIPK) 1 functions as a key mediator of tissue homeostasis via formation of Caspase-8 activating ripoptosome complexes, positively and negatively regulating apoptosis, necroptosis, and inflammation. Here, we report an unanticipated cell-death- and inflammation-independent function of RIPK1 and Caspase-8, promoting faithful chromosome alignment in mitosis and thereby ensuring genome stability. We find that ripoptosome complexes progressively form as cells enter mitosis, peaking at metaphase and disassembling as cells exit mitosis. Genetic deletion and mitosis-specific inhibition of Ripk1 or Caspase-8 results in chromosome alignment defects independently of MLKL. We found that Polo-like kinase 1 (PLK1) is recruited into mitotic ripoptosomes, where PLK1's activity is controlled via RIPK1-dependent recruitment and Caspase-8-mediated cleavage. A fine balance of ripoptosome assembly is required as deregulated ripoptosome activity modulates PLK1-dependent phosphorylation of downstream effectors, such as BUBR1. Our data suggest that ripoptosome-mediated regulation of PLK1 contributes to faithful chromosome segregation during mitosis.

Ubiquitin-Mediated Regulation of RIPK1 Kinase Activity Independent of IKK and MK2.

Tumor necrosis factor (TNF) can drive inflammation, cell survival, and death. While ubiquitylation-, phosphorylation-, and nuclear factor κB (NF-κB)-dependent checkpoints suppress the cytotoxic potential of TNF, it remains unclear whether ubiquitylation can directly repress TNF-induced death. Here, we show that ubiquitylation regulates RIPK1's cytotoxic potential not only via activation of downstream kinases and NF-kB transcriptional responses, but also by directly repressing RIPK1 kinase activity via ubiquitin-dependent inactivation. We find that the ubiquitin-associated (UBA) domain of cellular inhibitor of apoptosis (cIAP)1 is required for optimal ubiquitin-lysine occupancy and K48 ubiquitylation of RIPK1. Independently of IKK and MK2, cIAP1-mediated and UBA-assisted ubiquitylation suppresses RIPK1 kinase auto-activation and, in addition, marks it for proteasomal degradation. In the absence of a functional UBA domain of cIAP1, more active RIPK1 kinase accumulates in response to TNF, causing RIPK1 kinase-mediated cell death and systemic inflammatory response syndrome. These results reveal a direct role for cIAP-mediated ubiquitylation in controlling RIPK1 kinase activity and preventing TNF-mediated cytotoxicity.

MK2 Phosphorylates RIPK1 to Prevent TNF-Induced Cell Death.

TNF is an inflammatory cytokine that upon binding to its receptor, TNFR1, can drive cytokine production, cell survival, or cell death. TNFR1 stimulation causes activation of NF-κB, p38α, and its downstream effector kinase MK2, thereby promoting transcription, mRNA stabilization, and translation of target genes. Here we show that TNF-induced activation of MK2 results in global RIPK1 phosphorylation. MK2 directly phosphorylates RIPK1 at residue S321, which inhibits its ability to bind FADD/caspase-8 and induce RIPK1-kinase-dependent apoptosis and necroptosis. Consistently, a phospho-mimetic S321D RIPK1 mutation limits TNF-induced death. Mechanistically, we find that phosphorylation of S321 inhibits RIPK1 kinase activation. We further show that cytosolic RIPK1 contributes to complex-II-mediated cell death, independent of its recruitment to complex-I, suggesting that complex-II originates from both RIPK1 in complex-I and cytosolic RIPK1. Thus, MK2-mediated phosphorylation of RIPK1 serves as a checkpoint within the TNF signaling pathway that integrates cell survival and cytokine production.

Clinical Outcomes of Combined Anterior Cruciate Ligament Reconstruction and Lateral Extra-articular Tenodesis Procedures in Skeletally Immature Patients: A Systematic Review From the SANTI Study Group.

BACKGROUND: The treatment of anterior cruciate ligament (ACL) tears in the pediatric population has changed significantly in the past few decades. Pediatric patients who underwent ACL reconstruction (ACLR) have a high risk of rerupture of up to 32%. The addition of lateral extra-articular procedures [lateral extra-articular tenodesis (LET)], already shown to be effective in reducing the risk of rerupture in adults, may also be effective in pediatric patients. The purpose of this study was to systematically review the clinical outcomes of ACLR+LET tenodesis in pediatric patients. METHODS: Data were collected from Pubmed, MEDLINE, Cochrane, and Scopus Databases according to the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Studies reporting the clinical outcomes of ACLR+LET in the pediatric population using autograft, return to play, growth disturbances, failure rate, and surgical complications were included. RESULTS: A total of 5 studies comprising 381 pediatric patients were included. Three main surgical techniques with common features were used. The mean age of all pediatric patients in the included studies was 11.73 years (range, 5.6 to 16) with a mean follow-up of 50.1 months. The overall graft failure rate of the included studies was 4.65%. The return to play was 95.11%. The mean Lysholm score was 94.51 and the mean Pediatric International Knee Documentation Committee (Pedi-IKDC) was 93.39. In all, 1.9% of the patients had a coronal plane deformity and 0.8% had a limb length discrepancy. 4.6% of the patients had a contralateral ACL tear. CONCLUSIONS: A combined ACLR+LET in pediatric patients showed a graft failure ranging from 0% to 13.6% at a mean follow-up of 50.1 months. This low graft failure rate is consistent with ACLR+LET in adults. Further investigations are needed to validate these findings and the potential role of LET in reducing graft rupture rates in this population. LEVEL OF EVIDENCE: Level IV-systematic review of level IV studies.

Comorbidities rather than age affect medium-term outcome in octogenarian patients after total knee arthroplasty.

PURPOSE: As the population ages, it is important to determine whether total knee arthroplasties (TKA)s are safe and beneficial in the octogenarian population. The aims of the present study were: (1) to assess the effect of comorbidities and age on the incidence of postoperative complications following TKA and (2) to evaluate the mid-term outcome of octogenarian patients. METHODS: A retrospective matched-paired analysis by gender, BMI and duration of follow-up was conducted on 206 patients older than 80 years and younger than 75 years between 2009 and 2016, undergoing primary TKA. The mean follow-up was 5 years. Outcome measures including Oxford Knee Score (OKS), Knee Society Score (KSS), Knee Society Function Score (KSFS), postoperative complications, length of stay (LOS) and survivorship were analysed. The association between complications and comorbidities was assessed using multivariable logistic regression after adjusting for age, Deyo-Charlson Comorbidity Index (D-CCI) and the American Society of Anesthesiologist's (ASA) physical status classification. RESULTS: In the multivariable models, D-CCI class is an independent predictor for postoperative cardiac complications, delirium and transfusion rate (OR ranging from 1.2 to 69.5 in respect to D-CCI reference class 0). Being ≥ 80 years old was associated with an increased risk of transfusion (OR 3.4; 95% CI 1.7-6.8) and 1.7-day increase in LOS (p < 0.001). Both groups showed significant improvement in postoperative knee scores following TKA. CONCLUSION: Octogenarians experienced good clinical results when compared to their younger counterparts. Comorbidities, rather than age itself, are responsible for the increase in postoperative morbidity. Preoperative risk assessment has to be optimized in order to reduce complications.

The healing potential of an acutely repaired ACL: a sequential MRI study.

BACKGROUND: Recently, there has been renewed interest in primary anterior cruciate ligament (ACL) repair. The aim of this study is to report early clinical and radiological results of a consecutive series of acute ACL tears treated with arthroscopic primary ACL repair within 14 days from injury. PATIENTS AND METHODS: A consecutive series of patients with acute ACL tears were prospectively included in the study. Based on MRI appearance, ACL tears were classified into five types, and tissue quality was graded as good, fair, and poor. Patients with type I, II, and III tears and at least 50% of ACL tibial remnant intact with good tissue quality were ultimately included. Clinical outcomes were measured using the Tegner Lysholm Knee Scoring Scale (TLKSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS), subjective and objective International Knee Documentation Committee (IKDC) scores, and KT-1000. Patients were also followed up with MRI evaluations at 1, 3, and 6 months postoperatively. ACL appearance was graded based on morphology (normal or abnormal) and signal intensity (isointense, intermediate, and hyperintense). RESULTS: The mean TLKSS was 98.1, the mean subjective IKDC was 97.6, and the mean KOOS was 98.2. The objective IKDC score was A in eight of ten patients and B in two patients. KT-1000 measurements showed a maximum manual side-to-side difference of less than 2 mm in eight of ten patients, whereas two patients showed a difference of 3 mm. The morphology of the repaired ACL was normal (grade 1) at 1 month follow-up in ten of ten cases, and this appearance persisted at 3 and 6 months postoperatively. The signal intensity at 1 month postoperatively was graded as isointense (grade 1) in four of ten patients, intermediate (grade 2) in five of ten patients, and hyperintense (grade 3) in one of ten patients. At both 3 and 6 months postoperatively, the signal intensity was graded as isointense (grade 1) in nine of ten patients and intermediate (grade 2) in one of ten patients. CONCLUSIONS: Arthroscopic primary ACL repair performed acutely in a carefully selected group of patients with proximal ACL tears and good tissue quality showed good early clinical and radiological results. LEVEL OF EVIDENCE: Level 4.

TAT-RasGAP317-326-mediated tumor cell death sensitization can occur independently of Bax and Bak.

The increase of cancer specificity and efficacy of anti-tumoral agents are prime strategies to overcome the deleterious side effects associated with anti-cancer treatments. We described earlier a cell-permeable protease-resistant peptide derived from the p120 RasGAP protein, called TAT-RasGAP317-326, as being an efficient tumor-specific sensitizer to apoptosis induced by genotoxins in vitro and in vivo. Bcl-2 family members regulate the intrinsic apoptotic response and as such could be targeted by TAT-RasGAP317-326. Our results indicate that the RasGAP-derived peptide increases cisplatin-induced Bax activation. We found no evidence, using in particular knock-out cells, of an involvement of other Bcl-2 family proteins in the tumor-specific sensitization activity of TAT-RasGAP317-326. The absence of Bax and Bak in mouse embryonic fibroblasts rendered them resistant to cisplatin-induced apoptosis and consequently to the sensitizing action of the RasGAP-derived peptide. Surprisingly, in the HCT116 colon carcinoma cell line, the absence of Bax and Bak did not prevent cisplatin-induced apoptosis and the ability of TAT-RasGAP317-326 to augment this response. Our study also revealed that p53, while required for an efficient genotoxin-induced apoptotic response, is dispensable for the ability of the RasGAP-derived peptide to improve the capacity of genotoxins to decrease long-term survival of cancer cells. Hence, even though genotoxin-induced Bax activity can be increased by TAT-RasGAP317-326, the sensitizing activity of the RasGAP-derived peptide can operate in the absence of a functional mitochondrial intrinsic death pathway.

Return to Soccer After Acute Anterior Cruciate Ligament Primary Repair: A 2-Year Minimum Follow-up Study of 50 Amateur Players.

BACKGROUND: Return to sport (RTS) after treatment of an anterior cruciate ligament (ACL) tear is a critical parameter to assess the outcome of a surgical procedure. However, few studies have investigated RTS after ACL repair. PURPOSE: To evaluate RTS of a group of amateur soccer players at a minimum follow-up of 2 years after ACL repair. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A retrospective review of all patients treated with acute ACL repair was conducted. A total of 50 amateur soccer players were included in the study. Patients were examined clinically or contacted to complete postoperative patient-reported outcome measures, namely the Knee injury and Osteoarthritis Outcome Score, the International Knee Documentation Committee questionnaire, the ACL-Return to Sport After Injury scale, and the Forgotten Joint Score-12. RESULTS: The patients' mean age was 25.8 ± 7.7 years (range, 14-47 years), and the mean follow-up was 34.3 ± 10.7 months (range, 24-51.3 months). The median Tegner Activity Scale score was 9. The ACL repair failure rate was 16% (8/50). The mean time from repair to failure was 23.1 ± 12.7 months (range, 6-44 months), and the mean age of patients who sustained ACL repair failure was 19.9 ± 3.3 years (range, 14-24 years), significantly lower compared with patients who did not experience ACL repair failure (26.9 ± 7.9 years; range, 16-47 years; P = .017). Multivariate analysis showed that age ≤21 years was the only significant risk factor for ACL repair failure (odds ratio, 5.45; confidence interval, 1.24-27.91; P = .041). Excluding the 8 patients who experienced repair failure, 31 of 42 patients (73.8%) returned to soccer after ACL repair, with 29 of the 31 (93.5%) returning at their preinjury level of play. Moreover, patients who played competitive soccer and returned to their preinjury level of play were significantly younger than those who did not return to their preinjury level of play (mean, 21.1 ± 3.4 vs 29.2 ± 9.5 years, respectively; P = .002) and had significantly better ACL-Return to Sport After Injury scores (mean, 96.6 ± 4 vs 87.8 ± 11, respectively; P = .044). CONCLUSION: In this study, 73.8% (n = 31) of patients returned to playing soccer, of whom 93.5% (n = 29) returned to their preinjury level after ACL repair. The failure rate was 16% (n = 8) and mainly involved patients ≤21 years old.

Arthroscopic Physeal Sparing Anterior Cruciate Ligament Reconstruction and Lateral Extra-articular Tenodesis With Semitendinosus and Gracilis Tendons.

Anterior cruciate ligament (ACL) injuries among young patients have increased in recent years. The purpose of this study was to present a physeal-sparing intra- and extra-articular reconstruction using semitendinosus and gracilis tendons autograft. In recent years, the management of these injuries in the pediatric population has become increasingly surgical to restore knee function and reduce the risk of meniscal and chondral injury due to persistent knee instability. However, this is a population at high risk for ACL graft rupture, but it can be lowered by an addition of lateral extra-articular tenodesis (LET). This study shows the pearls and pitfalls of an arthroscopic physeal-sparing ACL reconstruction combined with a concomitant LET using hamstrings autograft.

Human 3D Ovarian Cancer Models Reveal Malignant Cell-Intrinsic and -Extrinsic Factors That Influence CAR T-cell Activity.

In vitro preclinical testing of chimeric antigen receptor (CAR) T cells is mostly carried out in monolayer cell cultures. However, alternative strategies are needed to take into account the complexity and the effects of the tumor microenvironment. Here, we describe the modulation of CAR T-cell activity by malignant cells and fibroblasts in human three-dimensional (3D) in vitro cell models of increasing complexity. In models combining mucin-1 (MUC1) and TnMUC1 CAR T cells with human high-grade serous ovarian cancer cell spheroids, malignant cell-intrinsic resistance to CAR T-cell killing was due to defective death receptor signaling involving TNFα. Adding primary human fibroblasts to spheroids unexpectedly increased the ability of CAR T cells to kill resistant malignant cells as CCL2 produced by fibroblasts activated CCR2/4+ CAR T cells. However, culturing malignant cells and fibroblasts in collagen gels engendered production of a dense extracellular matrix that impeded CAR T-cell activity in a TGFß-dependent manner. A vascularized microfluidic device was developed that allowed CAR T cells to flow through the vessels and penetrate the gels in a more physiological way, killing malignant cells in a TNFα-dependent manner. Complex 3D human cell models may provide an efficient way of screening multiple cytotoxic human immune cell constructs while also enabling evaluation of mechanisms of resistance involving cell-cell and cell-matrix interactions, thus accelerating preclinical research on cytotoxic immune cell therapies in solid tumors. Significance: Three-dimensional in vitro models of increasing complexity uncover mechanisms of resistance to CAR T cells in solid tumors, which could help accelerate development of improved CAR T-cell constructs.

A slight degree of osteoarthritis appears to be present after anterior cruciate ligament reconstruction compared with contralateral healthy knees at a minimum of 20 years: A systematic review of the literature.

Purpose: The aim of the present systematic review was to quantitatively synthesize the best literature evidence regarding osteoarthritis developing after anterior cruciate ligament reconstruction (ACLR), including only studies with a follow-up duration of at least 20 years. Material and Methods: A systematic review was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines on four electronic databases (PubMed, Scopus, EMBASE and Cochrane Library). The outcome measures extracted from the studies were failure rate, subsequent knee surgery on the same knee, radiographic development of osteoarthritis measured with Kellgren-Lawrence, International Knee Documentation Committee (IKDC) radiographic score and Ahlbäck classification. The health of both the ACLR knee and the contralateral knee was compared. Results: A total of 1552 patients were included in the study, of which 1290 (83.11%) were operated on using a patellar tendon graft, 190 (12.24%) with hamstrings, 27 (1.73%) with an iliotibial band and 45 (2.89%) with patellar tendon plus a ligament augmentation device (LAD). The mean age at the time of surgery was 25.18 ± 1.91 years, and the mean follow-up time was 23.34 ± 2.56 years. Analysing IDKC Score at final follow-up, ACLR Group showed a higher degree of OA compared with contralateral healthy knee (p < 0.01), but only 33.2% (324/976) of the patients showed a moderate to severe degree (Grade C or D) of osteoarthritis, while for Kellgren-Lawrence, ACLR Group showed a higher degree of OA compared with contralateral healthy knee (p < 0.01), but only 28.9% (196/678) of the patients showed a moderate to severe degree (Grade III or IV) of osteoarthritis. In total, 1552 patients were registered, 155 reruptures (9.98%) and a total of 300 (19.3%) new surgeries, of which 228 meniscectomy (14.69%), 21 (1.35%) knee arthroplasty and 17 (1.09%) hardware removal were recorded. Conclusions: ACL reconstruction appears to result in mild osteoarthritis in the long term in most of the patients and only less than 33.2% develop a moderate to severe degree of knee OA according to IKDC radiographic score. A slight degree of osteoarthritis appears to be present in ACLR knees compared with contralateral healthy knees. Level of Evidence: Level IV.

Evaluating the Reliability of YouTube as a Source of Information for Meniscal Ramp Lesions.

Background: Videos uploaded to YouTube do not go through a review process, and therefore, videos related to medial meniscal ramp lesions may have little educational value. Purpose: To assess the educational quality of YouTube videos regarding ramp lesions of the meniscus. Study Design: Cross-sectional study. Methods: A standard search was performed on the YouTube website using the following terms: "ramp lesion" and "posterior meniscal detachment" and "ramp" and "meniscocapsular" and "meniscotibial detachment," and the top 100 videos based on the number of views were included for analysis. The video duration, publication data, and number of likes and views were retrieved, and the videos were categorized based on video source (health professionals, orthopaedic company, private user), the type of information (anatomy, biomechanics, clinical examination, overview, radiologic, surgical technique), and video content (education, patient support, patient experience/testimony).The content analysis of the information on the videos was evaluated with the use of the DISCERN instrument (score range, 16-80), the Journal of the American Medical Association (JAMA) benchmark criteria (score range, 0-4), and the Global Quality Score (GQS; score range, 1-5). Results: A total of 74 videos were included. Of these videos, 70 (94.6%) were published by health professionals, while the remaining 4 (5.4%) were published by orthopaedic companies. Most of the videos were about surgical technique (n = 36; 48.6%) and all had an educational aim (n = 74; 100%). The mean length of the videos was 10.35 ± 17.65 minutes, and the mean online period was 18.64 ± 13.85 months. The mean DISCERN score, JAMA benchmark score, and GQS were 31.84 ± 17.14 (range, 16-72), 1.65 ± 0.87 (range, 1-4), and 2.04 ± 1.21 (range, 1-5), respectively. Videos that reported an overview about ramp lesions were the best in terms of quality for DISCERN and JAMA benchmark score, while biomechanics videos were the best according to GQS. The worst category of videos was about surgical technique, with all having lower scores. Conclusion: The educational content of YouTube regarding medial meniscal ramp lesions showed low quality and validity based on DISCERN score, JAMA benchmark score, and GQS.

RIPK1 is dispensable for cell death regulation in ß-cells during hyperglycemia.

OBJECTIVE: Receptor-interacting protein kinase 1 (RIPK1) orchestrates the decision between cell survival and cell death in response to tumor necrosis factor (TNF) and other cytokines. Whereas the scaffolding function of RIPK1 is crucial to prevent TNF-induced apoptosis and necroptosis, its kinase activity is required for necroptosis and partially for apoptosis. Although TNF is a proinflammatory cytokine associated with ß-cell loss in diabetes, the mechanism by which TNF induces ß-cell demise remains unclear. METHODS: Here, we dissected the contribution of RIPK1 scaffold versus kinase functions to ß-cell death regulation using mice lacking RIPK1 specifically in ß-cells (Ripk1ß-KO mice) or expressing a kinase-dead version of RIPK1 (Ripk1D138N mice), respectively. These mice were challenged with streptozotocin, a model of autoimmune diabetes. Moreover, Ripk1ß-KO mice were further challenged with a high-fat diet to induce hyperglycemia. For mechanistic studies, pancreatic islets were subjected to various killing and sensitising agents. RESULTS: Inhibition of RIPK1 kinase activity (Ripk1D138N mice) did not affect the onset and progression of hyperglycemia in a type 1 diabetes model. Moreover, the absence of RIPK1 expression in ß-cells did not affect normoglycemia under basal conditions or hyperglycemia under diabetic challenges. Ex vivo, primary pancreatic islets are not sensitised to TNF-induced apoptosis and necroptosis in the absence of RIPK1. Intriguingly, we found that pancreatic islets display high levels of the antiapoptotic cellular FLICE-inhibitory protein (cFLIP) and low levels of apoptosis (Caspase-8) and necroptosis (RIPK3) components. Cycloheximide treatment, which led to a reduction in cFLIP levels, rendered primary islets sensitive to TNF-induced cell death which was fully blocked by caspase inhibition. CONCLUSIONS: Unlike in many other cell types (e.g., epithelial, and immune), RIPK1 is not required for cell death regulation in ß-cells under physiological conditions or diabetic challenges. Moreover, in vivo and in vitro evidence suggest that pancreatic ß-cells do not undergo necroptosis but mainly caspase-dependent death in response to TNF. Last, our results show that ß-cells have a distinct mode of regulation of TNF-cytotoxicity that is independent of RIPK1 and that may be highly dependent on cFLIP.

The importance of murine phospho-MLKL-S345 in situ detection for necroptosis assessment in vivo.

Necroptosis is a caspase-independent modality of cell death implicated in many inflammatory pathologies. The execution of this pathway requires the formation of a cytosolic platform that comprises RIPK1 and RIPK3 which, in turn, mediates the phosphorylation of the pseudokinase MLKL (S345 in mouse). The activation of this executioner is followed by its oligomerisation and accumulation at the plasma-membrane where it leads to cell death via plasma-membrane destabilisation and consequent permeabilisation. While the biochemical and cellular characterisation of these events have been amply investigated, the study of necroptosis involvement in vivo in animal models is currently limited to the use of Mlkl-/- or Ripk3-/- mice. Yet, even in many of the models in which the involvement of necroptosis in disease aetiology has been genetically demonstrated, the fundamental in vivo characterisation regarding the question as to which tissue(s) and specific cell type(s) therein is/are affected by the pathogenic necroptotic death are missing. Here, we describe and validate an immunohistochemistry and immunofluorescence-based method to reliably detect the phosphorylation of mouse MLKL at serine 345 (pMLKL-S345). We first validate the method using tissues derived from mice in which Caspase-8 (Casp8) or FADD are specifically deleted from keratinocytes, or intestinal epithelial cells, respectively. We next demonstrate the presence of necroptotic activation in the lungs of SARS-CoV-infected mice and in the skin and spleen of mice bearing a Sharpin inactivating mutation. Finally, we exclude necroptosis occurrence in the intestines of mice subjected to TNF-induced septic shock. Importantly, by directly comparing the staining of pMLKL-345 with that of cleaved Caspase-3 staining in some of these models, we identify spatio-temporal and functional differences between necroptosis and apoptosis supporting a role of RIPK3 in inflammation independently of MLKL versus the role of RIPK3 in activation of necroptosis.

MLKL post-translational modifications: road signs to infection, inflammation and unknown destinations.

Necroptosis is a caspase-independent modality of cell death that requires the activation of the executioner MLKL. In the last ten years the field gained a substantial amount of evidence regarding its involvement in host response to pathogens, TNF-induced inflammatory diseases as well as pathogen recognition receptors (PRR)-induced inflammation. However, there are still a lot of questions that remain unanswered. While it is clear that there are specific events needed to drive MLKL activation, substantial differences between human and mouse MLKL not only highlight different evolutionary pressure, but also provide potential insights on alternative modalities of activation. While in TNF-induced necroptosis it is clear the involvement of the RIPK3 mediated phosphorylation, it still remains to be understood how certain inflammatory in vivo phenotypes are not equally rescued by either RIPK3 or MLKL loss. Moreover, the plethora of different reported phosphorylation events on MLKL, even in cells that do not express RIPK3, suggest indeed that there is more to MLKL than RIPK3-mediated activation, not only in the execution of necroptosis but perhaps in other inflammatory conditions that include IFN response. The recent discovery of MLKL ubiquitination has highlighted a new checkpoint in the regulation of MLKL activation and the somewhat conflicting evidence reported certainly require some untangling. In this review we will highlight the recent findings on MLKL activation and involvement to pathogen response with a specific focus on MLKL post-translational modifications, in particular ubiquitination. This review will highlight the outstanding main questions that have risen from the last ten years of research, trying at the same time to propose potential avenues of research.

Interposition Arthroplasty versus Dual Cup Mobility Prosthesis in Treatment of Trapeziometacarpal Joint Osteoarthritis: A Prospective Randomized Study.

BACKGROUND: Osteoarthritis (OA) of the trapeziometacarpal (TMC) joint is a common cause of pain and functional disability of the hand and is the second most frequent site in the hand of OA. This prospective randomized study analyses and compares the outcomes and global assessment of 2 different surgical techniques for rhizarthrosis treatment: trapeziectomy with tendon interposition arthroplasty and total joint replacement with Touch® (KeriMedical; Geneva, Switzerland) TMC prosthesis. METHODS: The enrolled patients were randomly divided into 2 groups: group A included 71 patients (75 hands) treated with tendon interposition arthroplasty, while group B included 65 patients (72 hands) treated with total joint replacement. Clinical and radiological outcomes were collected before surgery and at 1, 3, 6, 12, and 24 months of follow-up. RESULTS: Although the values of all clinical tests performed during follow-up demonstrated statistically significant improvement over preoperative ones in both groups, patients treated with prosthesis showed faster improvement, especially in tests of strength and range of motion, which showed better results than patients treated with trapeziectomy and tendon interposition arthroplasty throughout the follow-up. CONCLUSIONS: Our study suggests that joint replacement should be preferred to interposition arthroplasty as the treatment of rhizarthrosis, choosing the latter in case of prosthetic replacement complications or scaphoid-trapezium-trapezoid OA.

Spontaneous healing of a ruptured anterior cruciate ligament: a case series and literature review.

PURPOSE: The anterior cruciate ligament is probably one of the ligaments with the lowest healing potential. Many authors have reported cases of spontaneous healing but nowadays it is difficult to predict successful healing of an anterior cruciate ligament rupture and, even more, residual functionality and capability to return to sport. The aim of this study was to investigate cases of spontaneous healing in a population that received non-surgical treatment after anterior cruciate ligament rupture and to perform an updated review of contemporary literature. METHODS: The authors retrospectively reviewed patients who suffered from an acute complete anterior cruciate ligament rupture and underwent non-surgical treatment. No specific rehabilitation protocol was prescribed. A new magnetic resonance imaging study was conducted 6 months after the injury for all patients. A literature review was conducted regarding spontaneous healing of the anterior cruciate ligament. The papers included in the analysis were reports of any level of evidence, written in English, Italian, or French languages; articles were excluded if they reported non-human studies, histological studies, studies conducted without magnetic resonance imaging or arthroscopic second look, or partial anterior cruciate ligament tear. RESULTS: Case series: Six patients were enrolled in the study. All patients had a proximal anterior cruciate ligament lesion. The minimum follow-up was 13 months (range 6-20 months). At the last follow-up the mean score on the Lysholm scale was 97, the mean IKDC score was 94, and the mean KOOS score was 96. All patients returned to their own sport activities; no one reported significant differences. The magnetic resonance imaging study at 6 months revealed an end-to-end continuous anterior cruciate ligament with homogeneous signal. No one had any new knee injury at last follow-up. LITERATURE REVIEW: A search of comprehensive databases retrieved 1057 articles; 8 full-text articles met the eligibility criteria. The studies were heterogeneous regarding the populations analysed, sport activity level, treatment applied, healing definition, and follow-up. The failure rate of non-surgical management ranged among the papers from 0 to 73%. CONCLUSIONS: The study findings show that spontaneous anterior cruciate ligament healing is possible and there are chances of clinical recovery for patients not suitable for surgery. However, there is still a lack of evidence about predictors, clinical outcomes, and adequate rehabilitation protocols.

Comparison of Primary Repair of the Anterior Cruciate Ligament and Anterolateral Structures to Reconstruction and Lateral Extra-articular Tenodesis at 2-Year Follow-up.

BACKGROUND: Lateral extra-articular procedures have been effective in reducing graft rupture rates after anterior cruciate ligament (ACL) reconstruction (ACLR), but the evidence supporting their role in ACL repair is sparse. PURPOSE/HYPOTHESIS: The purpose was to compare clinical and radiological outcomes of ACLR and lateral extra-articular tenodesis (LET) (ACLR+LET) against combined repair of the ACL and anterolateral (AL) structures (ACL+AL Repair). It was hypothesized that patients undergoing ACL+AL Repair would have noninferior clinical and radiological outcomes with respect to International Knee Documentation Committee (IKDC) scores, knee laxity parameters, and magnetic resonance imaging (MRI) characteristics. Furthermore, it was hypothesized that patients undergoing repair would have significantly better Forgotten Joint Score-12 (FJS-12) values and shorter times to return to the preinjury level of sport, without any increase in the rate of ipsilateral second ACL injury. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Consecutive patients evaluated with an acute ACL tear were considered for study eligibility. ACLR+LET was only performed when intraoperative tear characteristics contraindicated ACL repair. Patient-reported outcome measures such as the IKDC score, Lysholm score, and Knee injury and Osteoarthritis Outcome Score (KOOS); reinjury rates; anteroposterior side-to-side laxity difference; and MRI characteristics were reported at a minimum follow-up of 2 years. The noninferiority study was based on the IKDC subjective score; side-to-side anteroposterior laxity difference; and signal-to-noise quotient (SNQ). The noninferiority margins were defined using the existing literature. An a priori sample size calculation was performed using the IKDC subjective score as the primary outcome measure. RESULTS: A total of 100 patients (47 ACLR+LET, 53 ACL+AL Repair) with a mean follow-up of 25.2 months (range, 24-31 months) were enrolled and underwent surgery within 15 days of injury. At the final follow-up, the differences between groups with respect to the IKDC score, anteroposterior side-to-side laxity difference, and SNQ did not exceed noninferiority thresholds. ACL+AL Repair was associated with a shorter time to return to the preinjury level of sport (ACL+AL Repair: mean, 6.4 months; ACLR+LET: mean, 9.5 months; P < .01), better FJS-12 values (ACL+AL Repair: mean, 91.4; ACLR+LET: mean, 97.4; P = .04), and a higher proportion of patients achieving the Patient Acceptable Symptom State (PASS) for the KOOS subdomains studied (Symptoms: 90.2% vs 67.4%, P = .005; Sport and Recreation: 94.1% vs 67.4%, P < .001; Quality of Life: 92.2% vs 73.9%, P = .01). There were no significant differences between groups with respect to ipsilateral second ACL injury rates (ACL+AL Repair group, 3.8% and ACLR+LET group, 2.1% [n = 1]; P = .63). CONCLUSION: ACL+AL Repair yielded clinical outcomes that were noninferior to (or not significantly different from) ACLR+LET with respect to IKDC subjective, Tegner activity level, and Lysholm scores; knee laxity parameters; graft maturity; and rates of failure and reoperation. However, there were significant advantages of ACL+AL Repair, including a shorter duration of time to return to the preinjury level of sport, better FJS-12 values, and a higher proportion of patients achieving PASS for KOOS subdomains studied (Symptoms, Sport and Recreation, Quality of Life).

Medial Patellofemoral Ligament Reconstruction Using Gracilis Tendon Graft and "All Suture" Knotless Anchors for Patellar Fixation.

Patellar dislocation is a frequent sports-related knee injury. The primary restraint to lateral translation of patella is medial patellofemoral ligament. Several treatments for patella dislocation have been described in the literature. The purpose of this Technical Note is to describe the surgical technique for medial patellofemoral ligament reconstruction using gracilis tendon and 2 knotless soft anchors, avoiding patella tunneling.

Cleavage of cFLIP restrains cell death during viral infection and tissue injury and favors tissue repair.

Cell death coordinates repair programs following pathogen attack and tissue injury. However, aberrant cell death can interfere with such programs and cause organ failure. Cellular FLICE-like inhibitory protein (cFLIP) is a crucial regulator of cell death and a substrate of Caspase-8. However, the physiological role of cFLIP cleavage by Caspase-8 remains elusive. Here, we found an essential role for cFLIP cleavage in restraining cell death in different pathophysiological scenarios. Mice expressing a cleavage-resistant cFLIP mutant, CflipD377A, exhibited increased sensitivity to severe acute respiratory syndrome coronavirus (SARS-CoV)-induced lethality, impaired skin wound healing, and increased tissue damage caused by Sharpin deficiency. In vitro, abrogation of cFLIP cleavage sensitizes cells to tumor necrosis factor(TNF)-induced necroptosis and apoptosis by favoring complex-II formation. Mechanistically, the cell death-sensitizing effect of the D377A mutation depends on glutamine-469. These results reveal a crucial role for cFLIP cleavage in controlling the amplitude of cell death responses occurring upon tissue stress to ensure the execution of repair programs.