Inpatient Hospital Costs, Emergency Department Visits, and Readmissions for Revision Hip and Knee Arthroplasty.

BACKGROUND: Revision total hip arthroplasty (THA) and total knee arthroplasty (TKA) tremendously burden hospital resources. This study evaluated factors influencing perioperative costs, including emergency department (ED) visits, readmissions, and total costs-of-care within 90 days following revision surgery. METHODS: A retrospective analysis of 772 revision TKAs and THAs performed on 630 subjects at a single center between January 2007 and December 2019 was conducted. Cost data were available from January 2015 to December 2019 for 277 patients. Factors examined included comorbidities, demographic information, preoperative Anesthesia Society of Anesthesiologists score, implant selection, and operative indication using mixed-effects linear regression models. RESULTS: Among 772 revisions (425 THAs and 347 TKAs), 213 patients required an ED visit, and 90 required hospital readmission within 90 days. There were 22.6% of patients who underwent a second procedure after their initial revision. Liver disease was a significant predictor of ED readmission for THA patients (multivariable odds ratio [OR]: 3.473, P = .001), while aseptic loosening, osteolysis, or instability significantly reduced the odds of readmission for TKA patients (OR: 0.368, P = .014). In terms of ED visits, liver disease increased the odds for THA patients (OR: 1.845, P = .100), and aseptic loosening, osteolysis, or instability decreased the odds for TKA patients (OR: 0.223, P < .001). Increased age was associated with increased costs in both THA and TKA patients, with significant cost factors including congestive heart failure for TKA patients (OR: $7,308.17, P = .004) and kidney disease for THA patients. Revision surgeries took longer than primary ones, with TKA averaging 3.0 hours (1.6 times longer) and THA 2.8 hours (1.5 times longer). CONCLUSIONS: Liver disease increases ED readmission risk in revision THA, while aseptic loosening, osteolysis, or instability decreases it in revision TKA. Increased age and congestive heart failure are associated with increased costs. These findings inform postoperative care and resource allocation in revision arthroplasty. LEVEL OF EVIDENCE: Economic and Decision Analysis, Level IV.

No significant difference in thick versus thin osteochondral flap trochleoplasty in the treatment of trochlear dysplasia: A systematic review.

PURPOSE: Trochleoplasty has become increasingly utilised to address patellar instability in the setting of severe trochlear dysplasia. There remains a paucity of literature on the outcomes of 'thick'- versus 'thin'-osteochondral flap trochleoplasty. The purpose of this study is to compare clinical and radiographic outcomes between patients with patellar instability with symptomatic trochlear dysplasia treated using a 'thick' versus 'thin' osteochondral flap trochleoplasty. METHODS: A systematic review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using a PRISMA checklist. Quality assessment of final articles was conducted by two blinded reviewers. Articles were separated based on the use of a 'thick' versus 'thin' flap trochleoplasty. Data collection consisted of recording the following variables: patient demographics, indications for trochleoplasty, mean follow-up time, additional procedures performed during trochleoplasty, patient-reported outcome measures (PROMs), radiographic outcomes (tibial tubercle-trochlear groove [TT-TG] distance, Caton-Deschamps Index [CDI] and sulcus angle [SA]) and the incidence of any postoperative complications and patellar redislocation rates. RESULTS: A total of 24 studies, consisting of 927 patients, were identified as meeting inclusion criteria. A total of five papers described a 'thick' flap technique, while 19 papers described the use of a 'thin' flap technique. No significant difference in the mean improvement of Kujala scores was appreciated when comparing 'thick' versus 'thin' techniques (p > 0.05). Improvements in mean radiographic outcomes based on TT-TG, CDI and SA were observed in both 'thick' and 'thin' flap trochleoplasty groups. The overall redislocation rate was 0.35%. CONCLUSION: No significant difference in Kujala scores was observed in patients undergoing trochleoplasty utilising 'thick' versus 'thin' technique, while improvements in mean TT-TG, CDI and SA were noted in both technique groups, with an overall redislocation rate of 0.35%. LEVEL OF EVIDENCE: Level IV.

The State of Local Antibiotic Use in Orthopedic Trauma.

Fracture-related infections are a challenging complication in orthopedic trauma that often necessitates multiple surgeries. Early administration of systemic antibiotics and surgical intervention remains the gold standard of care, but despite these measures, treatment failures can be as high as 35%. For these reasons, the introduction of local antibiotics at the site of at-risk fractures has increased over the past decade. This review looks at the various measures being used clinically including local antibiotic powder, polymethylmethacrylate, biodegradable substances, antibiotic-coated implants, and novel methods such as hydrogels and nanoparticles that have the potential for use in the future.

Effect of Preoperative Corticosteroids on Postoperative Glucose Control in Total Joint Arthroplasty.

Background: Dexamethasone is a commonly used perioperative medication for the management of postoperative nausea and vomiting following total joint arthroplasty (TJA). However, concerns have been raised about its potential to cause hyperglycemia. This study aimed to investigate the impact of dexamethasone administration on glucose levels and complications in both diabetic and nondiabetic patients undergoing TJA. Methods: We performed a retrospective review of 1928 patients who underwent primary total knee and hip arthroplasty procedures at a large tertiary medical institution. Patients were divided into 2 groups based on whether they received preoperative dexamethasone. Postoperative blood glucose values and variability were measured, and data on complications were collected. We performed statistical analysis using descriptive analysis, multivariate logistic regression models, negative binomial regression, and a subset analysis to assess the impact of dexamethasone dose on postoperative glycemic control. Results: Preoperative dexamethasone did not significantly increase the mean glucose, fasting glucose, glucose variability, or 90-day complications in both the diabetic and nondiabetic groups. Nondiabetic patients who received dexamethasone had a significantly lower rate of intensive care unit admission (P < .01). Additionally, patients who received dexamethasone had a significantly shorter length of hospital stay compared to those who did not (P < .001). Conclusions: Preoperative dexamethasone administration is a safe and effective method for preventing postoperative nausea and vomiting in patients undergoing TJA without significant adverse effects on glucose levels, glucose variability, or infection rates in both diabetics and nondiabetics. Preoperative dexamethasone decreases postoperative length of stay.

Thirty-Day Outcomes After Acute Total Hip Arthroplasty Combined With Internal Fixation of Acetabular Fractures: A Multi-Institutional Database Analysis.

INTRODUCTION: The purposes of this study were to characterize the 30-day surgical risk of patients undergoing open reduction and internal fixation (ORIF) and total hip arthroplasty stratified by an acetabular fracture pattern and to compare postoperative complications with ORIF alone using a large database. METHODS: The American College of Surgeons National Surgical Quality Improvement Program database was queried to determine 30-day outcomes after the combined hip procedure (CHP) compared with ORIF alone between 2005 and 2020. Current Procedural Terminology codes categorized fracture patterns. Univariate analysis was performed using the chi-square, Fisher exact, or Wilcoxon rank sum test. Logistic regression models were fitted to evaluate for any differences in postoperative complications. Total hospital length of stay was compared. RESULTS: A total of 1,187 patients were identified. One hundred eighty-four patients underwent a CHP, consisting of 99 acetabular wall fractures, 45 elementary acetabular fractures, and 40 associated acetabular fractures. There was no notable difference in any surgical site infection, thromboembolic events, transfusion rates, 30-day revision surgery, and readmission, regardless of the fracture pattern when controlling for comorbidities. Total hospital length of stay was shorter for patients who underwent a CHP for acetabular wall fractures or elementary acetabular fractures (P < 0.001). CONCLUSION: This combined surgical approach appears to have a similar 30-day risk profile when compared with ORIF alone regardless of the fracture pattern.

Diagnosing periprosthetic joint infection.

Aims: The diagnosis of periprosthetic joint infection (PJI) can be challenging as the symptoms are similar to other conditions, and the markers used for diagnosis have limited sensitivity and specificity. Recent research has suggested using blood cell ratios, such as platelet-to-volume ratio (PVR) and platelet-to-lymphocyte ratio (PLR), to improve diagnostic accuracy. The aim of the study was to further validate the effectiveness of PVR and PLR in diagnosing PJI. Methods: A retrospective review was conducted to assess the accuracy of different marker combinations for diagnosing chronic PJI. A total of 573 patients were included in the study, of which 124 knees and 122 hips had a diagnosis of chronic PJI. Complete blood count and synovial fluid analysis were collected. Recently published blood cell ratio cut-off points were applied to receiver operating characteristic curves for all markers and combinations. The area under the curve (AUC), sensitivity, specificity, and positive and negative predictive values were calculated. Results: The results of the analysis showed that the combination of ESR, CRP, synovial white blood cell count (Syn. WBC), and polymorphonuclear neutrophil percentage (PMN%) with PVR had the highest AUC of 0.99 for knees, with sensitivity of 97.73% and specificity of 100%. Similarly, for hips, this combination had an AUC of 0.98, sensitivity of 96.15%, and specificity of 100.00%. Conclusion: This study supports the use of PVR calculated from readily available complete blood counts, combined with established markers, to improve the accuracy in diagnosing chronic PJI in both total hip and knee arthroplasties.

Safety and Efficacy of Tranexamic Acid in Total Ankle Arthroplasty.

Tranexamic acid has been shown to significantly reduce blood loss in patients undergoing total knee arthroplasty and total hip arthroplasty. However, there is a paucity of data regarding its safety and efficacy in total ankle arthroplasty. The purpose of this study was to determine whether tranexamic acid use in patients with total ankle arthroplasty affects blood loss or overall complication rate. A retrospective chart review was conducted for 64 patients who underwent total ankle arthroplasty with (n = 32) and without (n = 32) intraoperative tranexamic acid from 2014 to 2023 at a single academic medical center. Recorded blood loss, pre-to-postoperative hemoglobin changes, hidden blood loss, and complication rates were recorded and compared. There was no statistically significant difference in recorded blood loss, total calculated blood loss, pre-to-postoperative hemoglobin difference, hidden blood loss, or overall complications between the groups (all, P > .05). A lower rate of wound complications was observed in the tranexamic acid group, but the difference between each group was not statistically significant (P > .05). Tranexamic acid did not decrease blood loss during total ankle arthroplasty, as measured in our study. Tranexamic acid was not associated with any increase in overall complications. Based on our findings, tranexamic acid may be a safe intervention in total ankle arthroplasty, but further studies are needed to better elucidate its clinical impact.Level of Evidence: Level 3.

Arthroscopic versus open irrigation and debridement in native knee septic arthritis: A retrospective review.

Introduction: Native knee septic arthritis is a rare condition with a potential for high morbidity if not promptly treated. Treatment involves surgical decompression of the affected joint along with systemic antibiotic therapy. The purpose of this study is to compare arthroscopic versus open irrigation and debridement for treatment of native knee septic arthritis. Methods: A retrospective review was conducted at a single academic institution of all patients treated for native knee septic arthritis from January 2007 until August 2018 utilizing ICD and CPT codes. Patient demographics, type of surgical procedure, need for reoperation, laboratory values, length of stay, and comorbidities were compared. Results: A cohort of sixty-six patients who underwent 85 surgeries were included. Among these surgeries, 52 (61%) were arthroscopic while 33 (39%) were open arthrotomies, and 21% required more than one operation. While not statistically significant, the odds of reoperation was higher for those that underwent arthroscopic compared to open irrigation and debridement on univariable (OR = 4.05, p = .08) and multivariable analysis (OR = 4.39, p = .10). Additionally, patients were more likely to require a longer hospital stay if they initially underwent arthroscopic rather than open debridement (RR = 1.31, p = .02). Conclusion: Native knee septic arthritis can be treated with a single surgery in the majority of cases. In our sample, there was an increased odds of reoperation in those treated arthroscopically compared to open, though this finding was not statistically significant. We found longer length of stay for patients undergoing arthroscopic rather than open irrigation and debridement - even after controlling for multiple operations, culture status, sex, age, and comorbidities.

Utility of Blood Cell Ratio Combinations for Diagnosis of Periprosthetic Joint Infection.

Background: Periprosthetic joint infection (PJI) is a serious complication following joint replacement surgery, and its diagnosis can be challenging due to the similarity of symptoms to other conditions and the lack of confirmatory imaging tests. Platelet/mean platelet volume ratio (PVR), platelet/lymphocyte ratio, monocyte/lymphocyte ratio, and neutrophil/lymphocyte ratio have been proposed as potential markers to aid in the diagnosis of PJI. This study aimed to further assess the utility of these blood cell ratio combinations for the diagnosis of PJI. Methods: A retrospective chart review was conducted on patients who presented to a university hospital for evaluation for PJI or underwent aseptic revision surgery. All patients were reviewed for inclusion in the study. Data were collected on several markers, including complete blood counts, synovial fluid white blood cell count, and polymorphonuclear percentage. Receiver operator characteristic curve analysis was used to evaluate the diagnostic capabilities of the markers and marker combinations. Results: The combination of erythrocyte sedimentation rate, C-reactive protein, synovial white blood cell count, and synovial polymorphonuclear percentage, with PVR, had the highest area under the curve of 0.97, with a sensitivity of 94.3% and a specificity of 88.9%, and a positive predictive value of 97.1% and a negative predictive value of 80.0%. Conclusions: This study further supports the use of PVR calculated from complete blood count commonly ordered laboratory values obtained during routine complete blood counts when combined with established serum and synovial markers to increase the diagnostic accuracy for diagnosing PJI.

Surgical smoke and the orthopedic surgeon: a non-systematic review of the hazards and strategies for mitigating risk.

INTRODUCTION: Surgical smoke generated through the use of electrical surgical devices poses a risk to the surgeon, medical personnel in the operating room, and the patient by exposing them to environmentally hazardous particulate matter. Previous investigation has shown that surgical smoke leads to an increased risk of pulmonary conditions, circulatory disorders, and irritation of the eyes, nose, and throat. Transmission of infectious disease can occur through inhalation of viral particles, and the presence of carcinogens are also of major concern. The deleterious effects of surgical smoke are well documented in several subspecialties, namely dermatology and general surgery, but there has been little discussion on the topic amongst orthopedic surgeons. METHODS: A non-systematic review of the literature was completed with the aim of identifying the major categories of adverse health effects associated with surgical smoke inhalation and offering recommendations to reduce these hazards in the orthopedic surgical community. RESULTS: Three primary categories of risk associated with surgical smoke inhalation were identified: inflammation, viral/bacterial transmission, and carcinogenicity. In addition, strategies for mitigating risk and best practice recommendations were explored. CONCLUSION: Surgical smoke is an under-recognized occupational hazard within the orthopedic surgery literature. There are several strategies which can be employed to reduce risk. Further investigation is needed to understand the long-term impact of these risks, as well as what can be done to improve the practicality and compliance with protective measures.

Treatment of Vancouver B2 Femur Fractures With Open Reduction Internal Fixation Versus Revision Arthroplasty.

Background Vancouver B2 periprosthetic femur fractures have traditionally been treated with revision arthroplasty. However, there is increasing evidence that open reduction and internal fixation (ORIF) may be a valid alternative treatment strategy. The purpose of this study was to compare the outcomes of ORIF versus revision arthroplasty for the treatment of Vancouver B2 fractures and evaluate the influence of the treating surgeon's fellowship training on treatment selection. Methodology This was a retrospective cohort study of 31 patients treated for Vancouver B2 periprosthetic fractures (16 ORIF and 15 revision arthroplasty) at a single academic Level 1 trauma center. Outcome measures included one-year mortality, revision, reoperation, infection, and blood loss. Results There were no statistically significant differences in revision, reoperation, or infection at an average follow-up of 65 weeks. Median estimated blood loss was higher in the arthroplasty group (700 cc versus 400 cc; P = 0.04). There were five deaths in the ORIF group versus one in the revision group (P = 0.18). Cases treated by surgeons with fellowship training in arthroplasty were more likely to be treated with revision arthroplasty (10/11, 90.9%) than those treated by surgeons with fellowship training in trauma (5/15, 33.3%; P < 0.01). Conclusions There was no difference in outcomes between the two treatment strategies, but revision was associated with higher blood loss. The appropriate treatment method should be based on surgeon familiarity and patients' characteristics.

Surgeon Accuracy in Prediction of Stability of Posterior Wall Acetabular Fractures. A Survey of Orthopaedic Trauma Surgeons.

OBJECTIVES: This study aims to investigate surgeon accuracy in prediction of the stability of posterior wall acetabular fractures by comparing "examination under anesthesia" findings to submitted estimations on the basis of radiograph and computed tomography (CT) imaging across a range of experience in orthopaedic surgeons and trainees. METHODS: Records of patients who underwent examination under anesthesia after presenting with posterior wall acetabular fractures at 2 different institutions were pooled for data collection, totaling 50 cases. Radiographs, CT images, and information regarding the presence of a hip dislocation requiring procedural reduction were provided to participants for review. A survey was generated for submission of impressions of stability for each individual case and disseminated among orthopaedic trainees and surgeons in practice. RESULTS: The submissions of 11 respondents were analyzed. Mean accuracy was calculated to be 0.70 (SD = 0.07). Sensitivity and specificity of respondents were 0.68 (SD = 0.11) and 0.71 (SD = 0.12), respectively. Positive predictive value and negative predictive value for respondents were 0.56 (SD = 0.09) and 0.82 (SD = 0.04), respectively. There was poor correlation of accuracy with years of experience with R 2 calculated to be 0.0004 and poor agreement between observers with Kappa measurement of interobserver reliability of 0.46. CONCLUSIONS: Our study suggests that surgeons are unable to consistently differentiate between stable and unstable patterns on the basis of assessments based on x-ray and CT. Years of experience in training or practice was not found to be associated with improved accuracy of stability prediction.

Cost Analysis of Conversion Total Knee Arthroplasty: A Multi-Institutional Database Study.

BACKGROUND: Total knee arthroplasty (TKA) after prior knee surgery, also known as conversion TKA (convTKA), has been associated with higher complications, resource utilization, time, and effort. The increased surgical complexity of convTKA may not be reflected by the relative value units (RVUs) assigned under the current U.S. coding guidelines. The purpose of this study was to compare the RVUs of primary TKA and convTKA and to calculate the RVU per minute to account for work effort. METHODS: The American College of Surgeons National Surgical Quality Improvement Project (NSQIP) database was analyzed for the years 2005 to 2020. Current Procedural Terminology (CPT) code 27447 alone was used to identify patients who underwent primary TKA, and 27447 plus 20680 were used to identify convTKA. After 1:1 propensity score matching, 1,600 cases were assigned to each cohort. The 2023 Medicare Physician Fee Schedule RVU-to-dollar conversion factor from the U.S. Centers for Medicare & Medicaid Services (CMS) was used to calculate RVU dollar valuations per operative time. Complication rates were compared using a multivariate logistic regression model controlling for baseline characteristics. RESULTS: The mean operative time for TKA was 97.8 minutes, with a corresponding RVU per minute of 0.25, while the mean operative time for convTKA was 124.3 minutes, with an RVU per minute of 0.19 (p < 0.0001). Using the conversion factor of $33.06 per RVU, this equated to $8.11 per minute for TKA versus $6.39 per minute for convTKA. ConvTKA was associated with higher overall complication (10.9% versus 6.5%, p < 0.0001), blood transfusion (6.6% versus 3.7%, p < 0.01), reoperation (2.3% versus 0.94%, p < 0.0001), and readmission (3.7% versus 1.8%, p < 0.001) rates. CONCLUSIONS: The current billing guidelines lead to lower compensation for convTKA despite its increased complexity. The longer operative time, higher complication rate, and increased resource utilization may incentivize providers to avoid performing this operation. CPT code revaluation is warranted to reflect the time and effort associated with this procedure. LEVEL OF EVIDENCE: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Predictors of Success With Chronic Antibiotic Suppression for Prosthetic Joint Infections.

BACKGROUND: Management of recurrent prosthetic joint infection (PJI) after attempted surgical eradication remains a challenge. Chronic antibiotic suppression (CAS) is regarded as a reasonable treatment option for select patients with persistent infection or multiple comorbidities. The study seeks to compare cohorts who succeed and fail with CAS. METHODS: This retrospective cohort study assesses patients who were treated with CAS for a PJI. Patients were included if they had a culture-proven PJI and received chronic suppressive antibiotics. Failure of suppression was defined as reoperation after initiating CAS or death occurring as result of infection. A Cox proportional hazards multivariate regression model was used to estimate risk of reoperation as a function of risk factors related to patient comorbidities, surgical history, affected joint, and infecting organism. RESULTS: We identified 45 PJIs (31 knees, 14 hips) managed with CAS with a median follow-up of 50 (95% confidence interval [CI] 33.61-74.02) months. The overall success rate of managing PJI with CAS was 67% (30/45). Controlling for body mass index and Gram status of the organism, total hip arthroplasty patients were less likely than total knee arthroplasty patients to require reoperation (hazard ratio 0.18, 95% CI 0.01-0.96, P = .04). Patients with Gram-positive infections were less likely than those with a Gram-negative infections to require reoperation (hazard ratio 0.22, 95% CI 0.05-0.88, P = .03). Severe antibiotic side effects were rare. Patients who experienced multiple changes to their antibiotic regimen were more likely to fail with CAS. CONCLUSION: CAS is a reasonable strategy in patients with PJI who lack or refuse further surgical treatment options. Most hips and Gram-positive infections treated with CAS successfully avoided reoperation in this cohort.

Relative Efficacy of Intra-articular Injections in the Treatment of Knee Osteoarthritis: A Systematic Review and Network Meta-analysis.

BACKGROUND: In younger patients and those without severe degenerative changes, the efficacy of intra-articular (IA) injections as a nonoperative modality for treating symptomatic knee osteoarthritis (OA)-related pain while maintaining function has become a subject of increasing interest. PURPOSE: To assess and compare the efficacy of different IA injections used for the treatment of knee OA, including hyaluronic acid (HA), corticosteroids (CS), platelet-rich plasma (PRP), and plasma rich in growth factors (PRGF), with a minimum 6-month patient follow-up. STUDY DESIGN: Meta-analysis of randomized controlled trials; Level of evidence, 1. METHODS: A systematic review was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines using the following databases: PubMed/MEDLINE, Scopus, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Google Scholar. Mean or mean change from baseline and standard deviation for outcome scores regarding pain and function were recorded at the 6-month follow-up and converted to either a 0 to 100 visual analog scale score for pain or a 0 to 100 Western Ontario and McMaster Universities Osteoarthritis Index score for function. A frequentist network meta-analysis model was developed to compare the effects of HA, CS, PRP, PRGF, and placebo on patient-reported outcomes. RESULTS: All IA treatments except CS were found to result in a statistically significant improvement in outcomes when compared with placebo. PRP demonstrated a clinically meaningful difference in function-related improvement when compared with CS and placebo due to large effect sizes. Studies evaluating outcomes of PRGF reported significant improvement when compared with placebo due to large effect sizes, whereas a potential clinically significant difference was detected in the same comparison parameters in pain evaluation. With regard to improvements in pain, function, and both combined, PRP was found to possess the highest probability of efficacy, followed by PRGF, HA, CS, and placebo. CONCLUSION: PRP yielded improved outcomes when compared with PRGF, HA, CS, and placebo for the treatment of symptomatic knee OA at a minimum 6-month follow-up. Further investigations evaluating different IA and other nonoperative treatment options for patients with knee OA are warranted to better understand the true clinical efficacy and long-term outcomes of nonsurgical OA management.

Tolerance induction and microglial engraftment after fetal therapy without conditioning in mice with Mucopolysaccharidosis type VII.

Mucopolysaccharidosis type VII (MPS7) is a lysosomal storage disorder (LSD) resulting from mutations in the ß-glucuronidase gene, leading to multiorgan dysfunction and fetal demise. While postnatal enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation have resulted in some phenotypic improvements, prenatal treatment might take advantage of a unique developmental window to penetrate the blood-brain barrier or induce tolerance to the missing protein, addressing two important shortcomings of postnatal therapy for multiple LSDs. We performed in utero ERT (IUERT) at E14.5 in MPS7 mice and improved survival of affected mice to birth. IUERT penetrated brain microglia, whereas postnatal administration did not, and neurological testing (after IUERT plus postnatal administration) showed decreased microglial inflammation and improved grip strength in treated mice. IUERT prevented antienzyme antibody development even after multiple repeated postnatal challenges. To test a more durable treatment strategy, we performed in utero hematopoietic stem cell transplantation (IUHCT) using congenic CX3C chemokine receptor 1-green fluorescent protein (CX3CR1-GFP) mice as donors, such that donor-derived microglia are identified by GFP expression. In wild-type recipients, hematopoietic chimerism resulted in microglial engraftment throughout the brain without irradiation or conditioning; the transcriptomes of donor and host microglia were similar. IUHCT in MPS7 mice enabled cross-correction of liver Kupffer cells and improved phenotype in multiple tissues. Engrafted microglia were seen in chimeric mice, with decreased inflammation near donor microglia. These results suggest that fetal therapy with IUERT and/or IUHCT could overcome the shortcomings of current treatment strategies to improve phenotype in MPS7 and other LSDs.

Characterization of Chlamydomonas reinhardtii Core Histones by Top-Down Mass Spectrometry Reveals Unique Algae-Specific Variants and Post-Translational Modifications.

The unicellular microalga Chlamydomonas reinhardtii has played an instrumental role in the development of many new fields (bioproducts, biofuels, etc.) as well as the advancement of basic science (photosynthetic apparati, flagellar function, etc.). Chlamydomonas' versatility ultimately derives from the genes encoded in its genome and the way that the expression of these genes is regulated, which is largely influenced by a family of DNA binding proteins called histones. We characterize C. reinhardtii core histones, both variants and their post-translational modifications, by chromatographic separation, followed by top-down mass spectrometry (TDMS). Because TDMS has not been previously used to study Chlamydomonas proteins, we show rampant artifactual protein oxidation using established nuclei purification and histone extraction methods. After addressing oxidation, both histones H3 and H4 are found to each have a single polypeptide sequence that is minimally acetylated and methylated. Surprisingly, we uncover a novel monomethylation at lysine 79 on histone H4 present on all observed molecules. Histone H2B and H2A are found to have two and three variants, respectively, and both are minimally modified. This study provides an updated assessment of the core histone proteins in the green alga C. reinhardtii by top-down mass spectrometry and lays the foundation for further investigation of these essential proteins.