Faculty Bibliography

INTRODUCTION/BACKGROUND:The study aimed to investigate the efficacy of autogenous iliac crest bone graft (ICBG) compared with other graft types in achieving successful fracture nonunion repair. METHODS:An institutional review board-approved retrospective review of prospectively collected data was conducted on a consecutive series of patients surgically treated for fracture nonunions at an academic medical center between September 10, 2004, and August 20, 2023. Patients were analyzed based on which bone graft type-ICBG versus alternative graft types-used during their nonunion repair. Patient demographics, injury characteristics, and surgical history were compared. Outcomes included radiographic healing, time to union, postoperative complications, and revision rate. Cohorts were compared using an independent sample Student t-test for continuous variables and chi-square or Fisher exact tests for categorical variables. One-way analysis of variance with post hoc comparisons assessed differences across treatment strategy groups. RESULTS:Five hundred fifty-six patients were treated surgically for a fracture nonunion using standard internal fixation and a "bone graft" for biologic stimulation. 57.4% of these patients were treated with autogenous ICBG; 42.6% received alternative grafts (iliac crest aspirate, allograft, bone morphogenetic, reamer-irrigation aspirator, and/or demineralized bone matrix, without autogenous cancellous iliac crest). Compared with the alternative cohort, the ICBG cohort showed greater healing success after a single nonunion surgery (95.6% ICBG versus 86.9% alternative, P < 0.001) and faster healing times (4.8 ± 2.4 months versus 7.1 ± 4.9 months, P < 0.001). Complications at the ICBG harvest site included wound infections/hematomas and iliac wing fracture. No notable differences were found in positive cultures at the time of surgery, postoperative fracture-related infection, implant failure, or neurovascular injury. DISCUSSION/CONCLUSIONS:Using autogenous ICBG in the surgical repair of fracture nonunions was associated with higher healing rates compared with alternative graft types, supporting its continued role in enhancing bone healing outcomes, even in the face of infected nonunion.

Determining the clinical relevance of BRCA2 variants of uncertain significance is critical for informed risk management. Recently, two saturation genome editing studies assessed the functional effects of all single nucleotide variants in the BRCA2 C-terminal DNA Binding Domain. To improve the accuracy of functional data used for ACMG/AMP variant classification, we combined results from these studies in four composite models and evaluated the performance of each model using variants with known classifications. Here, we show that an "Integrated VarCall Model", which combined raw functional data for 6383 variants from the original studies, yielded 98.8% accuracy and out-performed the original studies and other combined data models. Incorporation of the "Integrated VarCall Model" functional data with other sources of evidence according to ClinGen BRCA1/2 variant curation expert panel specifications resulted in classification of 5926 (92.8%) BRCA2 variants as pathogenic (n = 735) or benign (n = 5191) and provides valuable insights for individuals with BRCA2 variants.

OBJECTIVE:To examine factors associated with lag screw slide following fixation of intertrochanteric hip fractures with 1 type of cephalomedullary nail. METHODS:Retrospective review of patients operatively treated for intertrochanteric hip fractures (OTA/AO 31A1 and 31A2) with a single cephalomedullary nail (CMN) at a single academic medical centre between November 2014 and November 2023. CMN lag screw was placed in "dynamic" mode to allow for controlled collapse, or screw "slide." Screw slide was defined as the difference in lateral prominence of the lag screw at latest follow up compared to its initial position. Patients were grouped based on the amount of screw slide (<5 mm, 5-15 mm, >15 mm) and correlation analysis was performed. RESULTS: = 0.002) was associated with >15 mm screw slide. CONCLUSIONS:Excessive lag screw slide (>15 mm) was associated with higher patient BMI. Patients with higher BMIs should be monitored to identify excessive slide. Surgeons should attempt to keep the lag screw as close to the lateral cortex as possible. While the use of anti-osteoporotic therapy was associated with more slide, this was almost exclusively seen in patients only prescribed vitamin D and calcium.

Melanocyte stem cells (McSCs) are a crucial melanocyte reservoir within the hair follicle niche. This review provides an overview of the processes for McSC quiescence and activation. Because McSCs closely interact with hair follicle stem cells, we have focused on this interaction. Given the high prevalence of hair graying, the McSC system serves as a model for cellular aging. Here, we highlight current research on the mechanisms of hair graying.

BACKGROUND/UNASSIGNED:Dysregulated proteolysis is implicated in thoracic (thoracic aortic aneurysm [TAA]) and abdominal aortic aneurysm (AAA) pathogenesis, but proteolytic landscapes (degradomes) of aneurysmal and normal aorta and contributions of individual proteases remain undefined. Here, a proteome-wide approach was used to define and compare TAA and AAA degradomes and uncover the specific role in aortic remodeling of 2 proteases consistently identified in the aneurysms, CMA1 (mast cell chymase) and MMP9 (matrix metalloprotease 9). METHODS/UNASSIGNED:The mass spectrometry-based N-terminomics strategy, terminal amine isotopic labeling of substrates, was applied to Marfan syndrome TAAs (n=5), AAAs (n=16), and nondiseased thoracic aorta (n=4), and abdominal aorta (n=4) in a forward degradomics application, that is, to define substrate and protease degradomes. 8-plex iTRAQ terminal amine isotopic labeling of substrates was used for quantitative comparison of the tissue cohorts. Cleavage sites of CMA1 and MMP9 were sought by reverse degradomics, that is, digestion of aortic proteins with these proteases, followed by terminal amine isotopic labeling of substrates. CMA1 and MMP9 proteolysis of biglycan was further resolved using amino-terminal oriented mass spectrometry of substrates. RESULTS/UNASSIGNED:We experimentally annotated 20 885 proteolytically derived peptides and identified 129 proteases in the aortic tissues. Quantitative substrate degradome comparisons identified specific differentially modulated pathways and networks in TAAs and AAAs. Reverse degradomics elucidated >300 CMA1 and MMP9 substrate cleavage sites, of which many, including orthogonally validated biglycan cleavages, occurred in the disease degradomes. CONCLUSIONS/UNASSIGNED:Unbiased forward degradomics of the aortic wall from TAA, AAA, and nondiseased tissue provides a systems biology view of aortic wall breakdown and a new resource for its hitherto occult proteolytic landscape, demonstrating widespread extracellular matrix remodeling with disproportionate impact on proteoglycans. The findings provided insights into aortic aneurysm pathways and disease biomarkers and suggest involvement of numerous proteases. Mapping of specific proteolytic contributions of CMA1 and MMP9 illustrates a strategy for defining the activities of all proteases involved in aortic disease.

Brown adipose tissue is an evolutionary innovation in placental mammals that regulates body temperature through adaptive thermogenesis. Cold exposure activates brown adipose tissue thermogenesis through coordinated induction of brown adipogenesis, angiogenesis, and sympathetic innervation; however, how these processes are coordinated remains unclear. Here, we show that fragments of Slit guidance ligand 3 (SLIT3) drive crosstalk among adipocyte progenitors, endothelial cells, and sympathetic nerves. Adipocyte progenitors secrete SLIT3, which is cleaved into functionally distinct SLIT3-N and SLIT3-C fragments that independently promote angiogenesis and sympathetic innervation. We identify PLXNA1 as a receptor for SLIT3-C and demonstrate its essential role in sympathetic innervation of brown adipose tissue. Moreover, we identify BMP1 as the first SLIT protease described in vertebrates. Coordinated neurovascular expansion mediated by distinct SLIT3 fragments provides a bifurcated yet integrated mechanism that ensures a synchronized brown adipose tissue response to environmental challenges. Finally, this study reveals a previously unrecognized role for adipocyte progenitors in regulating tissue innervation.

The skin is the largest human organ and a site of substantial disease burden, yet its cellular and molecular organization across the body is largely undefined. Here we construct an organ-wide single-cell spatial atlas of ~1.2 million cells from normal adult human skin, resolving the location of 45 cell types across 114 samples encompassing 15 anatomic sites. We uncover site-specific stereotypic cell-type composition and their organization into ten multicellular neighborhoods, most notably a perivascular neighborhood reminiscent of skin-associated lymphoid tissue. Within this neighborhood, ligand-receptor (L-R) analyses identify a central role for tumor necrosis factor in maintaining CCL19⁺ perivascular fibroblasts, highlighting homeostatic immune-stromal crosstalk. Finally, comparing neighborhood dynamics in spatial transcriptomics of skin disease, we find pan-disease immune alterations in this perivascular neighborhood, suggesting spatial compartmentalization of pathogenic activity. Thus, multicellular neighborhoods underlie the skin's multiscale molecular to macroanatomic organization, orchestrate cell-cell interactions and anatomic site specialization and exhibit architectural disruption in disease.

The Drosophila corneal lens is an apical extracellular matrix structure with a biconvex shape that enables it to focus light onto the underlying photoreceptors. Here, we investigated how this shape is influenced by the source of one of its major components, the polysaccharide chitin. Knocking down the chitin synthase Krotzkopf verkehrt strongly reduced the thickness and curvature of the corneal lens. Conversely, enhancing chitin export by overexpressing Rebuf expanded and distorted the corneal lens. We found that the cone and primary pigment cells in the center of each ommatidium produce most of the chitin, and preventing chitin synthesis by these central cells reduced corneal lens curvature. Increasing chitin export from central cells increased the thickness of the central corneal lens, while increasing export from peripheral lattice cells made the edges thicker. The wild-type biconvex shape thus results from high levels of chitin production by central cells relative to peripheral cells, indicating that localized chitin secretion is critical for normal corneal lens curvature.

Epstein-Barr virus (EBV) plays a role in the pathogenesis of a wide variety of acute and chronic diseases. Cutaneous manifestations of EBV include exanthems, chronic infections, malignancies, and small vessel vasculitides. Clinically and histologically, many of these conditions can imitate each other, making diagnosis challenging. In this report, we present a case of a child who developed Gianotti-Crosti syndrome with histopathologic features of anti-neutrophil cytoplasmic antibody (ANCA) vasculitis in the setting of acute EBV infection. Furthermore, we review the literature on EBV-induced cutaneous small vessel vasculitis and discuss pathogenic mechanisms.