Faculty Bibliography

INTRODUCTION/BACKGROUND:The purpose of this study was to assess the effect of an acute traumatic meniscus tear that required repair in association with a tibial plateau fracture repair on outcomes. METHODS:Over a 17-year period, 843 patients presented with a tibial plateau fracture and were followed prospectively. 721 patients with Schatzker I-VI fractures were treated operatively via a standardized algorithm. 161 tibial plateau fractures (22.3 %) had an associated meniscus tear that underwent acute repair at the time of bony fixation. These patients were compared to operatively repaired tibial plateau fracture patients with no meniscus injury (NMR). Demographics were collected and outcomes including: radiographic healing, knee range of motion (ROM), and complication rates, were recorded. In addition, re-operation rates were compared and any reoperation for meniscus repair failure identified. All patients had a minimum of 1 year follow up. RESULTS:A total of 524 patients with a mean of 21.4 (range: 12-120) months follow up met inclusion criteria. Patients in the meniscus repair (MR) cohort had poorer knee extension (1.01 degrees, range: 0-30 degrees) compared to the NMR cohort (0.07 degrees, range: 0-10 degrees) (p < 0.001), in addition to poorer knee flexion (123 degrees, range: 0-145 degrees, p = 0.024). Additionally, MR patients reported higher pain scores (mean: 3 and range: 0-8, p = 0.005) at latest follow up. Finally, MR patients had higher rates of infection (8.1 % vs. 3.3 %, p = 0.025) and lateral collapse of the joint (p = 0.032). CONCLUSION/CONCLUSIONS:Patients who had a meniscus repair at the time of tibial plateau fracture repair were found to have poorer knee ROM, more patient reported pain at minimum 12 (mean 24) months post-operation. Additionally, these patients developed more post-operative complications than those patients who did not undergo a meniscus repair.

Stress-induced dinucleoside tetraphosphates (Np₄Ns, where N is adenosine, guanosine, cytosine or uridine) are ubiquitous in living organisms, yet their function has been largely elusive for over 50 years. Recent studies have revealed that RNA polymerase can influence the cellular lifetime of transcripts by incorporating these alarmones into RNA as 5'-terminal caps. Here we present structural and biochemical data that reveal the molecular basis of noncanonical transcription initiation from Np₄As by Escherichia coli and Thermus thermophilus RNA polymerases. Our results show the influence of the first two nucleotide incorporation steps on capping efficiency and the different interactions of Np₄As with transcription initiation complexes. These data provide critical insights into the substrate selectivity that dictates levels of Np₄ capping in bacterial cells.

Astrocytic Ca²⁺ activity regulates activity-dependent synaptic plasticity, but its role in learning-related synaptic changes in the living brain remains unclear. We found that motor training induced synaptic potentiation on apical dendrites of layer 5 pyramidal neurons, as well as astrocytic Ca²⁺ rises in the mouse motor cortex. Reducing astrocytic Ca²⁺ led to synaptic depotentiation during motor training and subsequent impairment in performance improvement. Notably, synaptic depotentiation occurred on a fraction of dendrites with repetitive dendritic Ca²⁺ activity. On those dendrites, dendritic spines that were active before dendritic Ca²⁺ activity underwent CaMKII-dependent size reduction. In addition, the activation of adenosine receptors prevented repetitive dendritic Ca²⁺ activity and synaptic depotentiation caused by the reduction of astrocytic Ca²⁺, suggesting the involvement of ATP released from astrocytes and adenosine signaling in the processes. Together, these findings reveal the function of astrocytic Ca²⁺ in preventing synaptic depotentiation by limiting repetitive dendritic activity during learning.

Insulin resistance impairs benefits of lipid-lowering treatment as evidenced by higher cardiovascular risk in individuals with type 2 diabetes versus those without. Because platelet activity is higher in insulin-resistant patients and promotes atherosclerosis progression, we questioned whether platelets impair inflammation resolution in plaques during lipid-lowering. In mice with obesity and insulin resistance, we induced advanced plaques, then implemented lipid-lowering to promote atherosclerotic plaque inflammation-resolution. Concurrently, mice were treated with either platelet-depleting or control antibodies for 3 weeks. Platelet activation and insulin resistance were unaffected by lipid-lowering. Both antibody-treated groups showed reduced plaque macrophages, but plaque cellular and structural composition differed. In platelet-depleted mice, scRNA seq revealed dampened inflammatory gene expression in plaque macrophages and an expansion of a subset of Fcgr4+ macrophages having features of inflammation-resolving, phagocytic cells. Necrotic core size was smaller and collagen content greater, resembling stable human plaques. Consistent with the mouse results, clinical data showed that patients with lower platelet counts had decreased pro-inflammatory signaling pathways in circulating non-classical monocytes after lipid-lowering. These findings highlight that platelets hinder inflammation-resolution in atherosclerosis during lipid-lowering treatment. Identifying novel platelet-targeted therapies following lipid-lowering treatment in individuals with insulin resistance may be a promising therapeutic approach to promote atherosclerotic plaque inflammation-resolution.

BACKGROUND:The knee's inflammatory response to ligamentous, meniscal, and cartilage injuries is complex and incompletely understood, particularly in the setting of concomitant injuries. Recent research has highlighted the potential utility of synovial fluid biomarker analysis in identifying factors involved in the progression of posttraumatic osteoarthritis. PURPOSE/OBJECTIVE:To investigate if unique patterns of knee injury are associated with distinct synovial fluid biomarker profiles at the time of surgical intervention. STUDY DESIGN/METHODS:Cross-sectional study; Level of evidence, 3. METHODS:Patients undergoing arthroscopic knee surgery were prospectively enrolled and asked to complete the Lysholm Knee Scoring Scale and visual analog scale for pain preoperatively. Synovial fluid was aspirated from the operative knee before surgical incision, and the concentrations of 10 biomarkers of interest were quantified. Patients with intraoperative evidence of articular cartilage, meniscal, and/or anterior cruciate ligament (ACL) injury were identified and included for subsequent analysis. Biomarker concentrations were log-normalized and standardized. Principal component analysis (PCA) was performed using biomarker variables to reduce dimensionality and extract key patterns. Multivariable linear regression for each retained principal component (PC) was performed with the predictors of age, sex, body mass index, symptom duration, ACL injury, meniscal injury, and Outerbridge grade. A separate regression analysis was performed to assess relationships between PCs and patient-reported outcomes controlling for the same variables. RESULTS:= .001; β = -.199). CONCLUSION/CONCLUSIONS:Cartilage lesions exhibited a synovial fluid inflammatory profile distinct from ACL and meniscal injury at the time of knee arthroscopy. While ACL and meniscal injuries displayed a pro-inflammatory phenotype, more severe cartilage lesions were associated with a reduced presence of anti-inflammatory markers. The pro-inflammatory phenotype also independently correlated with worse baseline knee function. These findings contribute to the understanding of the pathophysiology of ligamentous, meniscal, and cartilage injuries and may aid in the identification of pathology-specific treatments to help alter the natural history of disease.

PURPOSE OF REVIEW/OBJECTIVE:Cardiovascular diseases (CVDs) are a leading cause of death worldwide. While it is well known that obesity, dyslipidemia and diabetes are major risk factors of CVD, observational clinical studies have shown that variability in body weight, circulating LDL-cholesterol (LDL-C) or glucose levels further increase this risk. The underlying mechanisms, however, leading to increased risk of CVD due to metabolic cycling are not well understood. RECENT FINDINGS/RESULTS:Recent studies have shown that metabolic cycling can cause reprogramming of immune cells and their progenitors. Weight, LDL-C, or glucose cycling induced myelopoiesis, monocytosis and/or altered immune cell functions. This resulted in a heightened immune response, ultimately worsening atherosclerosis. SUMMARY/CONCLUSIONS:Even though there are differences in how metabolic cycling is measured in clinical and basic research studies, the conclusion remains the same: metabolic cycling increases CVD severity. Some studies have highlighted the role of reprogramming of myeloid cells and their progenitors in progression of atherosclerosis due to metabolic cycling, but further research is required to better understand the mechanisms behind it.

Arrhythmogenic cardiomyopathy (ACM) is a genetically heterogeneous inherited cardiomyopathy with an estimated prevalence of 1:5000-10 000 that predisposes patients to life-threatening ventricular arrhythmias (VA) and sudden cardiac death (SCD). ACM diagnostic criteria and risk prediction models, particularly for arrhythmogenic right ventricular cardiomyopathy (ARVC), the most common form of ACM, are typically genotype-agnostic, but numerous studies have established clinically meaningful genotype-phenotype associations. Early signs of ACM onset differ by genotype indicating the need for genotype-specific diagnostic criteria and family screening paradigms. Likewise, risk factors for SCD vary by genetic subtype, indicating that genotype-specific guidelines for management are also warranted. Of particular importance, genotype-specific therapeutic approaches are being developed. Results from a randomized controlled trial for flecainide use in ARVC patients are currently pending. Research in a plakophilin-2-deficient mouse model suggests this antiarrhythmic drug may be particularly useful for patients with likely pathogenic or pathogenic (LP/P) PKP2 variants. Additionally, the first gene therapy clinical trials in ARVC patients harboring LP/P PKP2 variants are currently underway. This review aims to provide clinicians caring for ACM patients with an up-to-date overview of the current literature in genotype-specific natural history of disease and management of ACM patients and describe scientific advances that have led to upcoming clinical trials.

Directional interactions that generate regular coordination geometries are a powerful means of guiding molecular and colloidal self-assembly, but implementing such high-level interactions with proteins remains challenging due to their complex shapes and intricate interface properties. Here we describe a modular approach to protein nanomaterial design inspired by the rich chemical diversity that can be generated from the small number of atomic valencies. We design protein building blocks using deep learning-based generative tools, incorporating regular coordination geometries and tailorable bonding interactions that enable the assembly of diverse closed and open architectures guided by simple geometric principles. Experimental characterization confirms the successful formation of more than 20 multicomponent polyhedral protein cages, two-dimensional arrays and three-dimensional protein lattices, with a high (10%-50%) success rate and electron microscopy data closely matching the corresponding design models. Due to modularity, individual building blocks can assemble with different partners to generate distinct regular assemblies, resulting in an economy of parts and enabling the construction of reconfigurable networks for designer nanomaterials.