Glucosylceramide synthase modulation ameliorates murine renal pathologies and promotes macrophage effector function in vitro.

While significant advances have been made in understanding renal pathophysiology, less is known about the role of glycosphingolipid (GSL) metabolism in driving organ dysfunction. Here, we used a small molecule inhibitor of glucosylceramide synthase to modulate GSL levels in three mouse models of distinct renal pathologies: Alport syndrome (Col4a3 KO), polycystic kidney disease (Nek8jck), and steroid-resistant nephrotic syndrome (Nphs2 cKO). At the tissue level, we identified a core immune-enriched transcriptional signature that was shared across models and enriched in human polycystic kidney disease. Single nuclei analysis identified robust transcriptional changes across multiple kidney cell types, including epithelial and immune lineages. To further explore the role of GSL modulation in macrophage biology, we performed in vitro studies with homeostatic and inflammatory bone marrow-derived macrophages. Cumulatively, this study provides a comprehensive overview of renal dysfunction and the effect of GSL modulation on kidney-derived cells in the setting of renal dysfunction.

Demographics and Early Outcomes of Commercial Antibiotic Cement Usage for Infection Prophylaxis During Primary Total Knee Arthroplasty in Patients Older Than 65 Years: An American Joint Replacement Registry Study.

INTRODUCTION: The use of antibiotic-laden bone cement (ALBC) for infection prophylaxis in the setting of primary total knee arthroplasty (TKA) remains controversial. Using data from the American Joint Replacement Registry (AJRR), (1) we examined the demographics of ALBC usage in the United States and (2) identified the effect of prophylactic commercially available ALBC on early revision and readmission for prosthetic joint infection (PJI) after primary TKA. METHODS: This is a retrospective cohort study of the AJRR from 2017 to 2020. Patients older than 65 years undergoing primary cemented TKA with or without the use of commercially available antibiotic cement were eligible for inclusion (N = 251,506 patients). Data were linked to available Medicare claims to maximize revision outcomes. Demographics including age, sex, race/ethnicity, Charlson Comorbidity Index (CCI), preoperative inflammatory arthritis, region, and body mass index (BMI) class were recorded. Cox proportional hazards regression analysis was used to evaluate the association between the two outcome measures and ALBC usage. RESULTS: Patients undergoing cemented TKA with ALBC were more likely to be Non-Hispanic Black ( P < 0.001), have a CCI of 2 or 3 ( P < 0.001), reside in the South ( P < 0.001), and had a higher mean BMI ( P < 0.001). In the regression models, ALBC usage was associated with increased risk of 90-day revision for PJI (hazards ratio 2.175 [95% confidence interval] 1.698 to 2.787) ( P < 0.001) and was not associated with 90-day all-cause readmissions. Male sex, higher CCI, and BMI >35 were all independently associated with 90-day revision for PJI. DISCUSSION: The use of commercial ALBC in patients older than 65 years for primary TKA in the AJRR was not closely associated with underlying comorbidities suggesting that hospital-level and surgeon-level factors influence its use. In addition, ALBC use did not decrease the risk of 90-day revision for PJI and was not associated with 90-day readmission rates.

Same-Day Outpatient Lower-Extremity Joint Replacement: A Critical Analysis Review.

➢ The economics of transitioning total joint arthroplasty (TJA) to standalone ambulatory surgery centers (ASCs) should not be capitalized on at the expense of patient safety in the absence of established superior patient outcomes. ➢ Proper patient selection is essential to maximizing safety and avoiding complications resulting in readmission. ➢ Ambulatory TJA programs should focus on reducing complications frequently associated with delays in discharge. ➢ The transition from hospital-based TJA to ASC-based TJA has substantial financial implications for the hospital, payer, patient, and surgeon.

Early complications and reoperation rates are similar amongst open reduction internal fixation, intramedullary nail, and distal femoral replacement for periprosthetic distal femur fractures: a systematic review and meta-analysis.

BACKGROUND: Our purpose was to perform a systematic review and meta-analysis to evaluate complication and revision rates for periprosthetic distal femur fractures (PPDFF) treated with: (1) ORIF using periarticular locking plates (ORIF), (2) retrograde intramedullary nail (IMN), and (3) distal femoral replacement (DFR). METHODS: Systematic review of the literature was performed to identify eligible studies (N = 52). Identified treatment groups were: ORIF (N = 1205 cases), IMN (N = 272 cases), and DFR (N = 353 cases). Median follow-up was 30 months (range 6-96 months). Primary outcomes were: (1) major complication rates and (2) reoperation rates over the follow-up period. Secondary outcomes were incidence of deep infection, periprosthetic fracture, mortality over the follow-up period, 1-year mortality, non-union, malunion, delayed union, and hardware failure. Data for primary and secondary outcomes were pooled and unadjusted analysis was performed. Meta-analysis was performed on subset of individual studies comparing at least two of three treatment groups (N = 14 studies). Odds-ratios and their respective standard errors were determined for each treatment group combination. Maximum likelihood random effects meta-analysis was conducted for primary outcomes. RESULTS: From the systematic review, major complication rates (p = 0.55) and reoperation rates (p = 0.20) were not significantly different between the three treatment groups. DFR group had a higher incidence of deep infection relative to IMN and ORIF groups (p = 0.03). Malunion rates were higher in IMN versus ORIF (p = 0.02). For the meta-analysis, odds of major complications were not significantly different between IMN versus DFR (OR 1.39 [0.23-8.52]), IMN versus ORIF (OR 0.86 [0.48-1.53]), or the ORIF versus DFR (OR 0.91 [0.52-1.59]). Additionally, odds of a reoperation were not significantly different between IMN versus DFR (OR 0.59 [0.08-4.11]), IMN versus ORIF (OR 1.26 [0.66-2.40]), or ORIF versus DFR (OR 0.91 [0.51-1.55]). CONCLUSIONS: There was no difference in major complications or reoperations between the three treatment groups. Deep infection rates were higher in DFR relative to internal fixation, malunion rates were higher in IMN versus ORIF, and periprosthetic fracture rates were higher in DFR and IMN versus ORIF.

Operative Anatomy of the Medial Gastrocnemius Recession vs the Proximal Medial Gastrocnemius Recession.

BACKGROUND: Isolated gastrocnemius contracture (IGC) is associated with various foot and ankle pathologies. To address the problem of IGC, a number of gastrocnemius lengthening procedures have been described. Although proximal medial gastrocnemius recession (PMGR) has shown to be an effective operative treatment for IGC, it poses risks to various anatomic structures around the knee joint and requires the patient to be positioned prone. As an alternative, we proposed to release the medial gastrocnemius at the division between the proximal one-third and distal two-thirds of the gastrocnemius muscle to correct equinus contracture, while minimizing risk to other structures. The aim of this study was to describe an anatomic basis for a medial gastrocnemius recession (MGR) and to investigate the anatomic structures at risk in comparison to PMGR. METHODS: Eight cadaveric lower leg specimens were used in the study. The standard PMGR and the novel MGR were performed on each specimen. After completion of the 2 procedures, complete dissection was performed to investigate the distances between surgically released fascia margins and surrounding anatomic structures, including the greater saphenous vein, small saphenous vein, saphenous nerve, medial sural cutaneous nerve, semimembranosus tendon, tibial nerve, and popliteal artery. The mean distances were calculated and the shortest distances for each structure were reported. RESULTS: Proximities of anatomic structures to surgically released gastrocnemius fascia at the medial and lateral margins were notably different between the 2 techniques. For the PMGR, the semimembranosus tendon (95% confidence interval of 2.4-7.4 mm), small saphenous vein (3.4-10.0 mm), popliteal artery (3.9-9.3 mm), and tibial nerve (5.0-11.1 mm) were in greater proximity to the operative margin. For the MGR, the greater saphenous vein (5.3-17.6 mm) and saphenous nerve (5.1-18.6 mm) were at greater risk. CONCLUSIONS: MGR at the proximal one-third of the gastrocnemius muscle may be a safe alternative for operative treatment of IGC. CLINICAL RELEVANCE: We identified the major structures at risk when performing the proximal medial gastrocnemius release and propose a novel, possibly safer alternative for the medial gastrocnemius release.

High-throughput Phenotyping of Lung Cancer Somatic Mutations.

Recent genome sequencing efforts have identified millions of somatic mutations in cancer. However, the functional impact of most variants is poorly understood. Here we characterize 194 somatic mutations identified in primary lung adenocarcinomas. We present an expression-based variant-impact phenotyping (eVIP) method that uses gene expression changes to distinguish impactful from neutral somatic mutations. eVIP identified 69% of mutations analyzed as impactful and 31% as functionally neutral. A subset of the impactful mutations induces xenograft tumor formation in mice and/or confers resistance to cellular EGFR inhibition. Among these impactful variants are rare somatic, clinically actionable variants including EGFR S645C, ARAF S214C and S214F, ERBB2 S418T, and multiple BRAF variants, demonstrating that rare mutations can be functionally important in cancer.

Identification of an "Exceptional Responder" Cell Line to MEK1 Inhibition: Clinical Implications for MEK-Targeted Therapy.

UNLABELLED: The identification of somatic genetic alterations that confer sensitivity to pharmacologic inhibitors has led to new cancer therapies. To identify mutations that confer an exceptional dependency, shRNA-based loss-of-function data were analyzed from a dataset of numerous cell lines to reveal genes that are essential in a small subset of cancer cell lines. Once these cell lines were determined, detailed genomic characterization from these cell lines was utilized to ascertain the genomic aberrations that led to this extreme dependency. This method, in a large subset of lung cancer cell lines, yielded a single lung adenocarcinoma cell line, NCI-H1437, which is sensitive to RNA interference of MAP2K1 expression. Notably, NCI-H1437 is the only lung cancer cell line included in the dataset with a known activating mutation in MAP2K1 (Q56P). Subsequent validation using shRNA and CRISPR-Cas9 confirmed MAP2K1 dependency. In vitro and in vivo inhibitor studies established that NCI-H1437 cells are sensitive to MEK1 inhibitors, including the FDA-approved drug trametinib. Like NCI-H1437 cells, the MAP2K1-mutant cell lines SNU-C1 (colon) and OCUM-1 (gastric) showed decreased viability after MAP2K1 depletion via Cas9-mediated gene editing. Similarly, these cell lines were particularly sensitive to trametinib treatment compared with control cell lines. On the basis of these data, cancers that harbor driver mutations in MAP2K1 could benefit from treatment with MEK1 inhibitors. Furthermore, this functional data mining approach provides a general method to experimentally test genomic features that confer dependence in tumors. IMPLICATIONS: Cancers with an activated RAS/MAPK pathway driven by oncogenic MAP2K1 mutations may be particularly sensitive to MEK1 inhibitor treatments.

Dynamic epigenetic regulation by menin during pancreatic islet tumor formation.

UNLABELLED: The tumor suppressor gene MEN1 is frequently mutated in sporadic pancreatic neuroendocrine tumors (PanNET) and is responsible for the familial multiple endocrine neoplasia type 1 (MEN-1) cancer syndrome. Menin, the protein product of MEN1, associates with the histone methyltransferases (HMT) MLL1 (KMT2A) and MLL4 (KMT2B) to form menin-HMT complexes in both human and mouse model systems. To elucidate the role of methylation of histone H3 at lysine 4 (H3K4) mediated by menin-HMT complexes during PanNET formation, genome-wide histone H3 lysine 4 trimethylation (H3K4me3) signals were mapped in pancreatic islets using unbiased chromatin immunoprecipitation coupled with next-generation sequencing (ChIP-seq). Integrative analysis of gene expression profiles and histone H3K4me3 levels identified a number of transcripts and target genes dependent on menin. In the absence of Men1, histone H3K27me3 levels are enriched, with a concomitant decrease in H3K4me3 within the promoters of these target genes. In particular, expression of the insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) gene is subject to dynamic epigenetic regulation by Men1-dependent histone modification in a time-dependent manner. Decreased expression of IGF2BP2 in Men1-deficient hyperplastic pancreatic islets is partially reversed by ablation of RBP2 (KDM5A), a histone H3K4-specific demethylase of the jumonji, AT-rich interactive domain 1 (JARID1) family. Taken together, these data demonstrate that loss of Men1 in pancreatic islet cells alters the epigenetic landscape of its target genes. IMPLICATIONS: Epigenetic profiling and gene expression analysis in Men1-deficient pancreatic islet cells reveals vital insight into the molecular events that occur during the progression of pancreatic islet tumorigenesis.

A radiographic and clinical comparison of reamer-irrigator-aspirator versus iliac crest bone graft in ankle arthrodesis.

PURPOSE: We evaluated radiographic fusion at follow-up and complication rates in patients who had either iliac crest (ICBG) or femoral reamer-irrigator-aspirator (RIA) bone graft for tibiotalar fusion. METHODS: We retrospectively reviewed charts and radiographs of all patients who had a tibiotalar fusion from August 2007 to February 2011. Records were analysed for patient demographics, complications, and clinical symptoms. Radiographs were reviewed in sequential order by two fellowship-trained foot and ankle surgeons and one orthopaedic surgeon who specialises in foot and ankle surgery to determine radiographic fusion at routine follow-up. Patients were contacted to determine current visual analog scores (VAS) at their graft site. RESULTS: Mean patient age was 49.4 ± 12.1 years in the RIA group and 49.3 ± 15.4 years in the ICBG group (p = .97). Pre-operative characteristics showed no significant differences between groups. The ICBG group had significantly more nonunions than the RIA group (six vs. one, p = 0.04). Two patients in the ICBG had chronic pain at their graft site based on their VAS score; there were none in the RIA group. Radiographic fusion at follow-up was similar between groups, with no significant difference (12.48 ± 3.85 weeks vs.12.21 ± 3.19 weeks, p = .80). CONCLUSIONS: There was a significantly higher nonunion rate in the ICBG group, but both groups had a solid radiographic bony fusion at similar follow-up time points. Our results suggest RIA bone graft is a viable alternative to ICBG for tibiotalar fusion.

Short to midterm clinical and radiographic outcomes of the Salto total ankle prosthesis.

BACKGROUND: Total ankle arthroplasty (TAA) has become an increasingly effective treatment option for tibiotalar arthritis. The purpose of this study was to evaluate the short to midterm clinical and radiographic outcomes of the Salto fixed bearing total ankle prosthesis. METHODS: We retrospectively reviewed the radiographs and patient records of 74 consecutive patients with 75 TAA implants from January 2007 to April 2011. The average age was 60.6 years (range, 41-82) with 41 females and 33 males. The average clinical follow-up was 43 months (range, 24-73 months). Radiographs were reviewed for areas of radiolucency and cystic changes around the talar and tibial implants, as well as for implant migration using standardized tibal, talar, talocalcaneal, and tibial slope angular measurements. The validated Foot and Ankle Outcome Score (FAOS), Short Form-12 (SF-12), and Visual Analog Scale (VAS) were used as subjective patient outcome measures. Kaplan Meier (K-M) curves were created for implant survivorship with revision of components as an endpoint and for return to the operating room for any reason. RESULTS: Total ankle survivorship was 98%. Thirteen patients returned to the operating room for any reason. There was 1 deep infection, and no ankles were converted to an arthrodesis. Average ankle dorsiflexion and plantarflexion improved from 4.3 ± 3.3 to 8.7 ± 5.6 degrees (P = .0008) and 24 ± 11 to 29 ± 7 degrees (P = .04), respectively. Patients showed significant improvements in all subscales of the FAOS (P < .0001). The physical component of the SF-12 significantly improved from 30 ± 8 to 41 ± 13 (P < .0001), but this was not observed with the mental component (52 ± 1 vs 53 ± 1, P = .55). The mean VAS for patient satisfaction was 9 (range, 2-10). Two patients had component migration (1 tibial and 1 talar component), neither of which required a revision procedure. Six ankles had a total of 9 radiolucent lines with a radiographically stable implant, and no patients had cystic changes. CONCLUSION: This is one of the first articles to report clinical and radiographic outcome data for the fixed bearing version of this prosthesis. We observed significant improvements in subjective outcome measures and range of motion with a 98% component survivorship at short to midterm follow-up. Longer follow-up will be necessary to determine the durability of this implant. LEVEL OF EVIDENCE: Level IV, case series.