Faculty Bibliography

Many growth factors and cytokines signal by binding to the extracellular domains of their receptors and driving association and transphosphorylation of the receptor intracellular tyrosine kinase domains, initiating downstream signaling cascades. To enable systematic exploration of how receptor valency and geometry affect signaling outcomes, we designed cyclic homo-oligomers with up to 8 subunits using repeat protein building blocks that can be modularly extended. By incorporating a de novo-designed fibroblast growth factor receptor (FGFR)-binding module into these scaffolds, we generated a series of synthetic signaling ligands that exhibit potent valency- and geometry-dependent Ca²⁺ release and mitogen-activated protein kinase (MAPK) pathway activation. The high specificity of the designed agonists reveals distinct roles for two FGFR splice variants in driving arterial endothelium and perivascular cell fates during early vascular development. Our designed modular assemblies should be broadly useful for unraveling the complexities of signaling in key developmental transitions and for developing future therapeutic applications.

Microsporidia are single-celled intracellular parasites that cause opportunistic diseases in humans. Encephalitozoon intestinalis is a prevalent human-infecting species that invades the small intestine. Dissemination to other organ systems is also observed, and is potentially facilitated by macrophages. The macrophage response to infection and the developmental trajectory of the parasite are not well studied. Here we use single cell RNA sequencing to investigate transcriptional changes in both the host and parasite during infection. While a small population of infected macrophages mount a response, most remain transcriptionally unchanged, suggesting that the majority of parasites may avoid host detection. The parasite transcriptome reveals large transcriptional changes throughout the life cycle, providing a blueprint for parasite development. The stealthy microsporidian lifestyle likely allows these parasites to harness macrophages for replication and dissemination. Together, our data provide insights into the host response in primary human macrophages and the E. intestinalis developmental program.

BACKGROUND:Primary osteoarthritis (OA) occurs without identifiable underlying causes such as previous injuries or specific medical conditions. Age is a major contributing factor to OA, and as one ages, various joint tissues undergo gradual change, including degeneration of the articular cartilage, alterations in subchondral bone (SCB) morphology, and inflammation of the synovium. METHODS:We investigated the prevalence of primary OA in aged, genetically diverse UM-HET3 mice. Articular cartilage (AC) integrity and SCB morphology were assessed in 182 knee joints of 22-25 months old mice using the Osteoarthritis Research Society International (OARSI) scoring system and micro-CT, respectively. Additionally, we explored the effects of methylene blue (MB) and mitoquinone (MitoQ), two agents that affect mitochondrial function, on the prevalence and progression of OA during aging. RESULTS:Aged UM-HET3 mice showed a high prevalence of primary OA in both sexes. Significant positive correlations were found between cumulative AC (cAC) scores and synovitis in both sexes, and osteophyte formation in female mice. Ectopic chondrogenesis did not show significant correlations with cAC scores. Significant direct correlations were found between AC scores and inflammatory markers in chondrocytes, including matrix metalloproteinase-13, inducible nitric oxide synthase, and the NLR family pyrin domain containing-3 inflammasome in both sexes, indicating a link between OA severity and inflammation. Additionally, markers of cell cycle arrest, such as p16 and β-galactosidase, also correlated with AC scores. In male mice, no significant correlations were found between SCB morphology traits and cAC scores, while in female mice, significant correlations were found between cAC scores and tibial SCB plate bone mineral density. Notably, MB and MitoQ treatments influenced the disease's progression in a sex-specific manner. MB treatment significantly reduced cAC scores at the medial knee joint, while MitoQ treatment reduced cAC scores, but these did not reach significance. CONCLUSIONS:Our study provides comprehensive insights into the prevalence and progression of primary OA in aged UM-HET3 mice, highlighting the sex-specific effects of MB and MitoQ treatments. The correlations between AC scores and various pathological factors underscore the multifaceted nature of OA and its association with inflammation and subchondral bone changes.

Infection and chronic post-traumatic osteomyelitis of the tibia after open fracture are complex problems that cause significant morbidity and threaten the viability of a limb. Therefore, it is of utmost importance for the orthopaedic surgeon to understand both patient and treatment factors that modify the risk of developing these disastrous complications. Infection risk is largely based on severity of open injury in addition to inherent patient factors. Orthopaedic surgeons can work to mitigate this risk with prompt antibiotic administration, thorough and complete debridement, expedient fracture stabilization, and early wound closure. In the case osteomyelitis does occur, the surgeon should use a systematic multidisciplinary approach for eradication.

We report on the latest advancements in Microcrystal Electron Diffraction (3D ED/MicroED), as discussed during a symposium at the National Center for CryoEM Access and Training housed at the New York Structural Biology Center. This snapshot describes cutting-edge developments in various facets of the field and identifies potential avenues for continued progress. Key sections discuss instrumentation access, research applications for small molecules and biomacromolecules, data collection hardware and software, data reduction software, and finally reporting and validation. 3D ED/MicroED is still early in its wide adoption by the structural science community with ample opportunities for expansion, growth, and innovation.

Melanosomal pH is important for the synthesis of melanin as the rate-limiting enzyme, tyrosinase, is very pH-sensitive. The soluble adenylyl cyclase (sAC) signaling pathway was recently identified as a regulator of melanosomal pH in melanocytes; however, the melanosomal proteins critical for sAC-dependent regulation of melanosomal pH were undefined. We now systematically examine four well-characterized melanosomal membrane proteins to determine whether any of them are required for sAC-dependent regulation of melanosomal pH. We find that OA1, OCA2, and SLC45A2 are dispensable for sAC-dependent regulation of melanosomal pH. In contrast, TPC2 activity is required for sAC-dependent regulation of melanosomal pH and melanin synthesis. In addition, activation of TPC2 by NAADP-AM rescues melanosomal pH alkalinization and reduces melanin synthesis following pharmacologic or genetic inhibition of sAC signaling. These studies establish TPC2 as a critical melanosomal protein for sAC-dependent regulation of melanosomal pH and pigmentation.

Aortic stiffening is an inevitable manifestation of chronological aging, yet the mechano-molecular programs that orchestrate region- and layer-specific adaptations along the length and through the wall of the aorta are incompletely defined. Here, we show that the decline in passive cyclic distensibility is more pronounced in the ascending thoracic aorta (ATA) compared to distal segments of the aorta and that collagen content increases in both the medial and adventitial compartments of the ATA during aging. The single-cell RNA sequencing of aged ATA tissues reveals altered cellular senescence, remodeling, and inflammatory responses accompanied by enrichment of T-lymphocytes and rarefaction of vascular smooth muscle cells, compared to young samples. T lymphocyte clusters accumulate in the adventitia, while the activation of mechanosensitive Piezo-1 enhances vasoconstriction and contributes to the overall functional decline of ATA tissues. These results portray the immuno-mechanical aging of the ATA as a process that culminates in a stiffer conduit permissive to the accrual of multi-gerogenic signals priming to disease development.

OBJECTIVE:The purpose of this study was to perform a network meta-analysis of level I and II evidence comparing different management techniques to define the optimum treatment method for humeral shaft fractures (HSFs). DATA SOURCES/METHODS:A systematic review of the literature using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines of MEDLINE, Embase, and Cochrane Library was screened from 2010 to 2023. STUDY SELECTION/METHODS:Inclusion criteria were evidence level I or II studies comparing nonoperative and/or operative repair techniques including open reduction internal fixation plate osteosynthesis (ORIF-Plate), minimally invasive percutaneous plating (MIPO), and intramedullary nail (IMN) fixation for the management of HSFs (OTA/AO 12A, B, C). DATA EXTRACTION/METHODS:The risk of bias and methodologic quality of evidence were assessed according to the guidelines designed by the Cochrane Statistical Methods Group and Cochrane Methods Bias Group. DATA SYNTHESIS/RESULTS:Network meta-analysis was conducted with a frequentist approach with a random-effects model using the netmeta package version 0.9-6 in R. RESULTS:A total of 25 studies (1908 patients) were included. MIPO resulted in the lowest complication rate (2.1%) when compared with ORIF-Plate (16.1%) [odds ratio (OR), 0.13; 95% confidence interval (CI), 0.04-0.49]. MIPO resulted in the lowest nonunion rate (0.65%) compared with all management techniques (OR, 0.28; 95% CI, 0.08-0.98), whereas Non-Op resulted in the highest (15.87%) (OR, 3.48; 95% CI, 1.98-6.11). MIPO demonstrated the lowest rate of postoperative radial nerve palsy overall (2.2%) and demonstrated a significantly lower rate compared with ORIF-Plate (OR, 0.22; 95% CI, 0.07-0.71, P = 0.02). IMN resulted in the lowest rate of deep infection (1.1%) when compared with ORIF-Plate (8.6%; P = 0.013). MIPO resulted in a significantly lower Disabilities of the Arm, Shoulder, and Hand score (3.86 ± 5.2) and higher American Shoulder and Elbow Surgeons score (98.2 ± 1.4) than ORIF-Plate (19.5 ± 9.0 and 60.0 ± 5.4, P < 0.05). CONCLUSION/CONCLUSIONS:The results from this study support that surgical management results in better postoperative functional outcomes, leads to higher union rates, reduces fracture healing time, reduces revision rate, and decreases malunion rates in patients with HSFs. In addition, MIPO resulted in statistically higher union rates, lowest complication rate, lowest rate of postoperative radial nerve palsy, and lower intraoperative time while resulting in better postoperative Disabilities of the Arm, Shoulder, and Hand and American Shoulder and Elbow Surgeons scores when compared with nonoperative and operative (ORIF and IMN) treatment modalities. LEVEL OF EVIDENCE/METHODS:Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.