Noisy Delay Denoises Biochemical Oscillators.

Genetic oscillations are generated by delayed transcriptional negative feedback loops, wherein repressor proteins inhibit their own synthesis after a temporal production delay. This delay is distributed because it arises from a sequence of noisy processes, including transcription, translocation, translation, and folding. Because the delay determines repression timing and, therefore, oscillation period, it has been commonly believed that delay noise weakens oscillatory dynamics. Here, we demonstrate that noisy delay can surprisingly denoise genetic oscillators. Specifically, moderate delay noise improves the signal-to-noise ratio and sharpens oscillation peaks, all without impacting period and amplitude. We show that this denoising phenomenon occurs in a variety of well-studied genetic oscillators, and we use queueing theory to uncover the universal mechanisms that produce it.

Defects in Long-Term APC Repopulation Ability of Adult Human Bone Marrow Hematopoietic Stem Cells (HSCs) Compared with Fetal Liver HSCs.

Immunodeficient mice reconstituted with immune systems from patients, or personalized immune (PI) mice, are powerful tools for understanding human disease. Compared with immunodeficient mice transplanted with human fetal thymus tissue and fetal liver-derived CD34+ cells administered i.v. (Hu/Hu mice), PI mice, which are transplanted with human fetal thymus and adult bone marrow (aBM) CD34+ cells, demonstrate reduced levels of human reconstitution. We characterized APC and APC progenitor repopulation in human immune system mice and detected significant reductions in blood, bone marrow (BM), and splenic APC populations in PI compared with Hu/Hu mice. APC progenitors and hematopoietic stem cells (HSCs) were less abundant in aBM CD34+ cells compared with fetal liver-derived CD34+ cell preparations, and this reduction in APC progenitors was reflected in the BM of PI compared with Hu/Hu mice 14-20 wk posttransplant. The number of HSCs increased in PI mice compared with the originally infused BM cells and maintained functional repopulation potential, because BM from some PI mice 28 wk posttransplant generated human myeloid and lymphoid cells in secondary recipients. Moreover, long-term PI mouse BM contained functional T cell progenitors, evidenced by thymopoiesis in thymic organ cultures. Injection of aBM cells directly into the BM cavity, transgenic expression of hematopoietic cytokines, and coinfusion of human BM-derived mesenchymal stem cells synergized to enhance long-term B cell and monocyte levels in PI mice. These improvements allow a sustained time frame of 18-22 wk where APCs and T cells are present and greater flexibility for modeling immune disease pathogenesis and immunotherapies in PI mice.

Rates of interlock screw back-out are high with the retrograde femoral nailing advanced system for distal femur fractures.

PURPOSE: The retrograde femoral nailing advanced (RFNA) system (DePuy synthes) is a commonly used implant for the fixation of low distal femur and periprosthetic fractures. There is concern that the rate of distal interlock screw back-out may be higher for the RFNA compared to other nails (ON). The purpose of this study was to evaluate the incidence of interlock screw back-out and associated screw removal for RFNA versus ON, along with associated risk factors. METHODS: A retrospective comparative study of patients who underwent retrograde nailing for a distal femur fracture at an academic level one trauma center was performed. The incidence of distal interlock screw back-out and need for screw removal were compared for RFNA versus a propensity score matched cohort who received other nails. RESULTS: One hundred and ten patients underwent retrograde nailing with the RFNA for a distal femur fracture from 2015 to 2022 (average age: 66, BMI: 32, 52.7% smokers, 54.5% female, 61.8%). There was a significantly higher rate of interlock back-out in the RFNA group compared to the ON (27 patients, 24.5% vs 12 patients, 10.9%, p = 0.01), which occurred 6.3 weeks postoperatively. Screw removal rates for back-out were not significantly different for the RFNA group versus ON (8 patients, 7.3% vs 3 patients, 2.7%, p = 0.12). CONCLUSION: In this retrospective comparative study of distal femur fractures treated with retrograde nailing, the RFNA implant was associated with an increased risk of distal interlock screw back-out compared to other nails.

Human stem cell-derived thymic epithelial cells enhance human T-cell development in a xenogeneic thymus.

BACKGROUND: Generation of thymic tissue from pluripotent stem cells would provide therapies for acquired and congenital thymic insufficiency states. OBJECTIVES: This study aimed to generate human thymic epithelial progenitors from human embryonic stem cells (hES-TEPs) and to assess their thymopoietic function in vivo. METHODS: This study differentiated hES-TEPs by mimicking developmental queues with FGF8, retinoic acid, SHH, Noggin, and BMP4. Their function was assessed in reaggregate cellular grafts under the kidney capsule and in hybrid thymi by incorporating them into swine thymus (SwTHY) grafts implanted under the kidney capsules of immunodeficient mice that received human hematopoietic stem and progenitor cells (hHSPCs) intravenously. RESULTS: Cultured hES-TEPs expressed FOXN1 and formed colonies expressing EPCAM and both cortical and medullary thymic epithelial cell markers. In thymectomized immunodeficient mice receiving hHSPCs, hES-TEPs mixed with human thymic mesenchymal cells supported human T-cell development. Hypothesizing that support from non-epithelial thymic cells might allow long-term function of hES-TEPs, the investigators injected them into SwTHY tissue, which supports human thymopoiesis in NOD severe combined immunodeficiency IL2Rγnull mice receiving hHSPCs. hES-TEPs integrated into SwTHY grafts, enhanced human thymopoiesis, and increased peripheral CD4+ naive T-cell reconstitution. CONCLUSIONS: This study has developed and demonstrated in vivo thymopoietic function of hES-TEPs generated with a novel differentiation protocol. The SwTHY hybrid thymus model demonstrates beneficial effects on human thymocyte development of hES-TEPs maturing in the context of a supportive thymic structure.

Interfragmentary strain measurement post-fixation to guide intraoperative decision making: a narrative review.

PURPOSE: Interfragmentary strain influences whether a fracture will undergo direct and indirect fracture healing. Orthopedic trauma surgeons modulate strain and create optimal biomechanical environments for specific fracture patterns using fixation constructs. However, objective intraoperative interfragmentary strain measurement does not currently inform fixation strategy in common practice. This review identifies potential methods and technologies to enable intraoperative strain measurement for guiding optimal fracture fixation strategies. METHODS: PubMed, Scopus, and Web of Science were methodologically queried for manuscripts containing terms related to "bone fracture," "strain," "measurement," and "intraoperative." Manuscripts were systematically screened for relevance and adjudicated by three reviewers. Relevant articles describing methods to measure interfragmentary strain intraoperatively were summarized. RESULTS: After removing duplicates, 1404 records were screened initially. There were 49 manuscripts meeting criteria for in-depth review. Of these, four reports were included in this study that described methods applicable to measuring interfragmentary strain intraoperatively. Two of these reports described a method using instrumented staples, one described optical tracking of Kirschner wires, and one described using a digital linear variable displacement transducer with a custom external fixator. CONCLUSION: The four reports identified by this review describe potential methods to quantify interfragmentary strain after fixation. However, further studies are needed to confirm the precision and accuracy of these measurements across a range of fractures and fixation methods. Additionally, described methods require the insertion and likely removal of additional implants into the bone. Ideally, innovations that measure interfragmentary strain intraoperatively would provide dynamic biomechanical feedback for the surgeon to proactively modulate construct stability.

Long-term sequelae of septic arthritis after tibial plateau fracture fixation: does timing matter?

INTRODUCTION: Septic arthritis following surgical treatment of a tibial plateau fracture is a rare complication, but it does occur, and the impact on long-term function is relatively unknown. The purpose of this study was to determine the long-term sequelae of septic arthritis among patients treated with internal fixation for a tibial plateau fracture and to determine the effect of timing (early or late infection) on the rate of such sequela. MATERIALS AND METHODS: A retrospective comparative study was designed using the trauma database of a single level I academic trauma center. Patients who developed culture-positive septic knee arthritis after internal fixation of a tibial plateau fracture, with 1-year follow-up, were included in the study. The number of debridement procedures required was recorded. Rates of long-term complications and implant removal were identified. Complications rates were compared between patients who developed early (within 30 days of definitive fixation) and late (more than 30 days) septic arthritis. RESULTS: The mean number of debridement procedures per patient was six. Fourteen patients (88%) required implant removal, and thirteen (81%) developed knee arthritis. There was a significantly lower rate of complications in the early septic arthritis group compared to the late group (3 of 6 patients or 50%, vs 10 of 10 patients or 100%; p = 0.036). CONCLUSIONS: Patients who developed septic arthritis following internal fixation of a tibial plateau fracture were likely to endure long-term sequelae. Early infection and detection led to fewer complications. Surgeons treating infectious complications in tibial plateau fracture patients should specifically seek to rule out septic arthritis, anticipate that implant removal may be necessary, and counsel these patients appropriately regarding the anticipated natural history of their condition. LEVEL OF EVIDENCE: III.

Representation Learning for Fine-Grained Change Detection.

Fine-grained change detection in sensor data is very challenging for artificial intelligence though it is critically important in practice. It is the process of identifying differences in the state of an object or phenomenon where the differences are class-specific and are difficult to generalise. As a result, many recent technologies that leverage big data and deep learning struggle with this task. This review focuses on the state-of-the-art methods, applications, and challenges of representation learning for fine-grained change detection. Our research focuses on methods of harnessing the latent metric space of representation learning techniques as an interim output for hybrid human-machine intelligence. We review methods for transforming and projecting embedding space such that significant changes can be communicated more effectively and a more comprehensive interpretation of underlying relationships in sensor data is facilitated. We conduct this research in our work towards developing a method for aligning the axes of latent embedding space with meaningful real-world metrics so that the reasoning behind the detection of change in relation to past observations may be revealed and adjusted. This is an important topic in many fields concerned with producing more meaningful and explainable outputs from deep learning and also for providing means for knowledge injection and model calibration in order to maintain user confidence.

Is percutaneous screw fixation really superior to non-operative management after valgus-impacted femoral neck fracture: a retrospective cohort study.

PURPOSE: The optimal management of valgus-impacted femoral neck fractures remains controversial. Internal fixation is associated with significant rates of re-operation, while historical non-operative management strategies consisting of prolonged bed rest also resulted in patient morbidity. Our hypothesis was that screw fixation would have comparable failure rates to non-operative treatment and immediate mobilization for valgus-impacted femoral neck fractures. METHODS: Retrospective cohort at a single academic Level I trauma center of patients with valgus-impacted femoral neck fractures (AO/OTA 31-B1) treated with percutaneous screw fixation (n = 97) or non-operatively (n = 28). Operative treatment consisted of percutaneous screw fixation. Non-operative treatment consisted of early mobilization. The primary outcome was a salvage operation. Patient demographics were assessed between groups. RESULTS: More non-operatively treated patients were permitted unrestricted weight-bearing (WBAT; p = 0.002). There was no increase in complication rates or mortality, and return to previous ambulatory status was comparable between operatively and non-operatively treated patients. 35.7% (10/28) of non-operatively treated patients underwent a subsequent operation, compared to 15.5% (15/97) of patients with screw fixation (p = 0.03). Only WBAT was independently associated with treatment failure (OR 3.1, 95%CI 1.2-8.3, p =0.02). WBAT was predictive of treatment failure only in the non-operatively treated group (64.3%, 9/14 WBAT vs 8.3%, 1/12 partial, p =0.005). CONCLUSION: After controlling for weight-bearing restrictions, we found no difference in failure rates between non-operative treatment and screw fixation. Non-operative treatment with partial weight-bearing had low failure rates, comparable complication and mortality rates, and equivalent functional outcomes to operative treatment and is reasonable if a patient would like to avoid surgery and accepts the risk of subsequent arthroplasty. Overall, there were relatively high failure rates in all groups.

How are peri-implant fractures below short versus long cephalomedullary nails different?

BACKGROUND: Cephalomedullary nails are a commonly used implant for the treatment of many pertrochanteric femur fractures and are available in short and long configurations. There is no consensus on ideal nail length. Relative advantages can be ascribed to short and long intramedullary nails, yet both implant styles share the potentially devastating complication of peri-implant fracture. Determining the clinical sequelae after fractures below nails of different lengths would provide valuable information for surgeons choosing between short or long nails. Thus, the purpose of the study was to compare injury patterns and treatment outcomes following peri-implant fractures below short or long cephalomedullary nails. METHODS: This was a multicenter retrospective cohort study that identified 33 patients referred for treatment of peri-implant fractures below short and long cephalomedullary nails (n = 19 short, n = 14 long). We compared fracture pattern, treatment strategy, complications, and outcomes between these two groups. RESULTS: Short nails were associated with more diaphyseal fractures (odds ratio [OR] 13.75, CI 2.2-57.9, p 0.002), which were treated more commonly with revision intramedullary nailing (OR, infinity; p 0.01), while long nails were associated with distal metaphyseal fractures (OR 13.75, CI 2.2-57.9, p 0.002), which were treated with plate and screw fixation (p 0.002). After peri-implant fracture, there were no differences in blood loss, operative time, weight bearing status, or complication rates based on the length of the initial nail. In patients treated with revision nailing, there was greater estimated blood loss (EBL, median 300 cc, interquartile range [IQR] 250-1200 vs median 200 cc, IQR 100-300, p 0.03), blood product utilization and complication rates (OR 11.1, CI 1.1-135.7, p 0.03), but a trend toward unrestricted post-operative weight-bearing compared to patients treated with plate and screw constructs. CONCLUSION: Understanding fracture patterns and patient outcomes after fractures below nails of different lengths will help surgeons make more informed implant choices when treating intertrochanteric hip fractures. Revision to a long nail for the treatment of fractures at the tip of a short nail may be associated with increased patient morbidity.

Pharmacological modulation and genetic deletion of REV-ERBα and REV-ERBß regulates dendritic cell development.

The nuclear receptors REV-ERBα and REV-ERBß have been demonstrated to play key roles in the regulation of numerous physiological functions, such as metabolism and the circadian rhythm. Recent studies have established the REV-ERBs' roles in immunity, including macrophage and T cell responses. In contrast, their roles in dendritic cells have not been well defined. Dendritic cells are potent antigen presenting cells, connecting microbial sensing and innate immunity to adaptive immune responses. We demonstrate that both REV-ERBα and REV-ERBß expression is upregulated during the course of bone marrow derived dendritic cell (BMDC) differentiation. BMDCs from REV-ERBα and REV-ERBß deficient mice showed enhanced expression of maturation markers like CD86, MHCII, and proinflammatory cytokines. Conversely, treatment of BMDCs with a REV-ERB-specific agonist, SR9009, inhibited the expression of maturation markers and proinflammatory cytokines. Our study suggests the REV-ERBs act as negative regulators of dendritic cell development and activation. These results indicate that pharmacological modulation of REV-ERB activity could be an attractive strategy to modulate DC activation status and for DC-based therapies.

Management of metabolic syndrome and reduction in body weight in type II diabetic mice by inhibiting glycosphingolipid synthesis.

Metabolic syndrome is defined by hyperlipidemia and cardiovascular complications. We have examined whether inhibition of glycosphingolipid synthesis can interfere with metabolic syndrome in a male mouse model of type II diabetes (db/db). The db/db and control mice (C57/BL6) (n = 6) fed chow for 30 weeks received vehicle (5% Tween-80 in PBS; 100 µl), or a biopolymer-encapsulated D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (BPD) glycosphingolipid synthesis inhibitor daily via oral gavage for 6 weeks. Echocardiography revealed increased Ao-IMT in db/db mice compared to control. However, BPD decreased Ao-IMT, monohexosylceramide and dihexosylceramide, LDL, triglycerides, glucose, and raised HDL levels in db/db mice. This was due to increased gene expression of HMG-CoA reductase, LDLr, SREBP2, and bile acids: Cy7-a hydroxylase, LXR and FXR, lipoprotein lipase, VLDL receptor and PPAR. Treatment also increased the expression of superoxide dismutase-II to reduce the pro-oxidant status in these mice. We observed that decreased cholesterol levels correlated with decreased cholesterol sensing proteins e.g. NPC1 gene/protein expression and mammalian target of rapamycin (mTORC-1) and reduced body weight. Thus, glycosphingolipid synthesis inhibition is a novel approach to manage metabolic syndrome and reduce body weight in diabetic mice and with potential applications in humans.

What have animals taught us about total joint arthroplasty ? A review of the literature.

Animal models for total joint arthroplasty (TJA) have been reported on extensively in the literature. This work seeks to objectively review the most relevant and recent studies performed using these models, and to provide insight into the strengths and weaknesses of each. The terms joint arthroplasty and animal model were searched on Pubmed on March 1, 2015. Animal models included bovine, canine, ovine, goat, rat, and rabbit. Much of the work in animal models for TJA has focused on the biologic response to novel materials, biologics, and surgical techniques ; as interest grows the use of animal models may increase.

Deconstructing Lipid Kinase Inhibitors by Chemical Proteomics.

Diacylglycerol kinases (DGKs) regulate lipid metabolism and cell signaling through ATP-dependent phosphorylation of diacylglycerol to biosynthesize phosphatidic acid. Selective chemical probes for studying DGKs are currently lacking and are needed to annotate isoform-specific functions of these elusive lipid kinases. Previously, we explored fragment-based approaches to discover a core fragment of DGK-α (DGKα) inhibitors responsible for selective binding to the DGKα active site. Here, we utilize quantitative chemical proteomics to deconstruct widely used DGKα inhibitors to identify structural regions mediating off-target activity. We tested the activity of a fragment (RLM001) derived from a nucleotide-like region found in the DGKα inhibitors R59022 and ritanserin and discovered that RLM001 mimics ATP in its ability to broadly compete at ATP-binding sites of DGKα as well as >60 native ATP-binding proteins (kinases and ATPases) detected in cell proteomes. Equipotent inhibition of activity-based probe labeling by RLM001 supports a contiguous ligand-binding site composed of C1, DAGKc, and DAGKa domains in the DGKα active site. Given the lack of available crystal structures of DGKs, our studies highlight the utility of chemical proteomics in revealing active-site features of lipid kinases to enable development of inhibitors with enhanced selectivity against the human proteome.

Chemoproteomic Discovery of a Ritanserin-Targeted Kinase Network Mediating Apoptotic Cell Death of Lung Tumor Cells.

Ritanserin was tested in the clinic as a serotonin receptor inverse agonist but recently emerged as a novel kinase inhibitor with potential applications in cancer. Here, we discovered that ritanserin induced apoptotic cell death of non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) cells via a serotonin-independent mechanism. We used quantitative chemical proteomics to reveal a ritanserin-dependent kinase network that includes key mediators of lipid [diacylglycerol kinase α, phosphatidylinositol 4-kinase ß] and protein [feline encephalitis virus-related kinase, rapidly accelerated fibrosarcoma (RAF)] signaling, metabolism [eukaryotic elongation factor 2 kinase, eukaryotic translation initiation factor 2-α kinase 4], and DNA damage response [tousled-like kinase 2] to broadly kill lung tumor cell types. Whereas ritanserin exhibited polypharmacology in NSCLC proteomes, this compound showed unexpected specificity for c-RAF in the SCLC subtype, with negligible activity against other kinases mediating mitogen-activated protein kinase signaling. Here we show that ritanserin blocks c-RAF but not B-RAF activation of established oncogenic signaling pathways in live cells, providing evidence in support of c-RAF as a key target mediating its anticancer activity. Given the role of c-RAF activation in RAS-mutated cancers resistant to clinical B-RAF inhibitors, our findings may have implications in overcoming resistance mechanisms associated with c-RAF biology. The unique target landscape combined with acceptable safety profiles in humans provides new opportunities for repositioning ritanserin in cancer.

Identification of potent RORß modulators: Scaffold variation.

We sought to develop RORß-selective probe molecules in order to investigate the function of the receptor in vitro and in vivo and its role in the pathophysiology of disease. To accomplish this, we modified a potent dual RORß/RORγ inverse agonist from the primary literature with the goal of improving selectivity for RORß vs RORγ. Truncation of the Western portion of the molecule ablated activity at RORγ and led to a potent series of RORß modulators. Continued exploration of this series investigated alternate replacement cores for the aminothiazole ring. Numerous suitable replacements were found during the course of our SAR investigations and are reported herein.

Antiseptics Commonly Used in Total Joint Arthroplasty Interact and May Form Toxic Products.

BACKGROUND: Multiple antiseptics have been described for use in total joint arthroplasty infection, and the use of multiple antiseptic solutions during a single operation has been described. Our clinical experience is that chlorhexidine (CHX) and Dakin's solution (NaOCl) interact and form a precipitate. The purpose of this study is to determine whether this reaction could be replicated in a laboratory setting, and to determine if other commonly used antiseptics also visibly react when mixed. METHODS: Four percent chlorhexidine gluconate (CHX), 0.5% sodium hypochlorite (NaOCl), 3% hydrogen peroxide (H2O2), and 10% povidone-iodine (BTD) solutions were obtained and all possible combinations were mixed. Any visible reactions were noted and recorded, and a literature search was performed to characterize the reaction and products. RESULTS: CHX and NaOCl, CHX and H2O2, and CHX and BTD reacted instantly, forming a precipitate. NaOCl and H2O2 reacted to produce a gas. NaOCl and BTD reacted and produced a color change. The literature review revealed that at least 2 of the reactions tested (CHX + NaOCl and NaOCl + H2O2) could result in byproducts toxic to humans. CONCLUSION: Surgeons must be aware of these interactions when using antiseptic solutions during procedures. Caution should be used combining or mixing antiseptics, and we recommend against concomitant introduction in a surgical wound.

Anatomic Posterolateral Corner Reconstruction Using a Fibula Cross-Tunnel Technique: A Cadaveric Biomechanical Study.

PURPOSE: To compare the biomechanical properties of a fibula cross-tunnel technique for posterolateral corner (PLC) reconstruction with those of intact knees. METHODS: Seven fresh-frozen cadaveric knees were tested while intact, after PLC tear, and after reconstruction. Testing of the parameters listed above was performed at 0°, 30°, 60°, and 90° of knee flexion. Reconstruction was performed using 2 independent tendon autografts. Afterward, the fibula and graft were loaded to failure. RESULTS: Reconstruction restored external rotation (0°: 11.75° ± 2.02° to 9.81° ± 1.81°, P = .57; 30°: 17.91° ± 1.32° to 13.96° ± 2.84°, P = .12; 60°: 15.86° ± 1.68° to 13.26° ± 3.58°, P = .41; 90°: 15.53° ± 1.62° to 14.07° ± 2.95°, P = .54) to the intact state, and posterior translation (0°: 3.66 ± 0.85 mm to 3.31 ± 0.89 mm, P = .87; 60°: 3.15 ± 0.45 mm to 2.96 ± 0.45 mm, P = .73; 90°: 2.74 ± 0.33 mm to 3.05 ± 0.41 mm, P = .41) and varus angulation (0°: 0.92° ± 0.35° to 1.98° ± 0.42°, P = .55; 30°: 2.65° ± 0.27° to 1.09° ± 0.90°, P = .37; 90°: 4.29° ± 0.44° to 2.53° ± 1.13°, P = .19) under most conditions. During load to failure testing, the construct revealed properties similar to those of native structures (yield load: 330.4 ± 45.8 N; ultimate load: 420.9 ± 37.4 N). CONCLUSIONS: This technique restored external rotation to the intact state after PLC injury in all testing conditions, as well as posterior translation at 0°, 60°, and 90° of flexion, and varus angulation under all conditions tested except 60° of flexion. CLINICAL RELEVANCE: Clinically, this surgical technique may eliminate the need for a tibial tunnel for posterolateral corner reconstruction.