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Browsing by Author "Koehler, Karl"
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Item Heparinized Gelatin-Based Hydrogels for Differentiation of Induced Pluripotent Stem Cells(American Chemical Society, 2022) Arkenberg, Matthew R.; Koehler, Karl; Lin, Chien-Chi; Biomedical Engineering, School of Engineering and TechnologyChemically defined hydrogels are increasingly utilized to define the effects of extracellular matrix (ECM) components on cellular fate determination of human embryonic and induced pluripotent stem cell (hESC and hiPSCs). In particular, hydrogels cross-linked by orthogonal click chemistry, including thiol-norbornene photopolymerization and inverse electron demand Diels-Alder (iEDDA) reactions, are explored for 3D culture of hESC/hiPSCs owing to the specificity, efficiency, cytocompatibility, and modularity of the cross-linking reactions. In this work, we exploited the modularity of thiol-norbornene photopolymerization to create a biomimetic hydrogel platform for 3D culture and differentiation of hiPSCs. A cell-adhesive, protease-labile, and cross-linkable gelatin derivative, gelatin-norbornene (GelNB), was used as the backbone polymer for constructing hiPSC-laden biomimetic hydrogels. GelNB was further heparinized via the iEDDA click reaction using tetrazine-modified heparin (HepTz), creating GelNB-Hep. GelNB or GelNB-Hep was modularly cross-linked with either inert macromer poly(ethylene glycol)-tetra-thiol (PEG4SH) or another bioactive macromer-thiolated hyaluronic acid (THA). The formulations of these hydrogels were modularly tuned to afford biomimetic matrices with similar elastic moduli but varying bioactive components, enabling the understanding of each bioactive component on supporting hiPSC growth and ectodermal, mesodermal, and endodermal fate commitment under identical soluble differentiation cues.Item Management of Mandible Fracture in 150 Children Across 7 Years in a US Tertiary Care Hospital(American Medical Association, 2019-09-19) Kao, Richard; Rabbani, Cyrus C.; Patel, Janaki M.; Parkhurst, Samantha M.; Mantravadi, Avinash V.; Ting, Jonathan Y.; Sim, Michael W.; Koehler, Karl; Shipchandler, Taha Z.; Otolaryngology -- Head and Neck Surgery, School of MedicineImportance: Pediatric mandible fractures are the most common pediatric facial fracture requiring hospitalization, but data are lacking on management methods, outcomes, and complications. Objective: To analyze management methods, outcomes, and complications of pediatric mandible fractures at an urban academic tertiary care center. Design, setting, and participants: Single-institution cohort study conducted at 2 urban level 1 pediatric trauma centers including all patients aged 0 to 17 years diagnosed with mandible fractures between January 1, 2010, and December 31, 2016. Fractures were treated by multispecialty surgical teams. Data were analyzed between January 1, 2018, and March 1, 2018. Main outcomes and measures: Fracture distributions, mechanisms, treatment methods, complications, and follow-up. Results: Of 150 patients with 310 total mandible fractures, the mean (SD) age was 12.8 (4.6) years; 108 (72.0%) were male; 107 (71.3%) were white; and 109 (72.7%) had 2 or more mandible fractures. There were 78 condylar or subcondylar fractures (60 patients), 75 ramus or angle fractures (69 patients), 69 body fractures (62 patients), 78 symphyseal or parasymphyseal fractures (76 patients), and 10 coronoid fractures (10 patients). The most common mechanisms of injury were assault and battery, motor vehicle collisions, falls or play, and sports-related mechanisms. Thirty-eight (25%) patients were treated with observation and a soft diet. Children 12 years and older were more likely to receive open reduction internal fixation (ORIF) (P = .02). Of 112 patients treated with surgery, 63 (56.2%) were treated with maxillomandibular fixation (MMF), 24 (21.4%) received ORIF, and 20 (17.9%) received both MMF and ORIF. Nonabsorbable plating was used in all but 1 of the ORIF procedures. Five of 44 (11.4%) patients receiving ORIF or ORIF and MMF had follow-up beyond 6 months, and 8 of the 44 (18.2%) had documented plating hardware removal; hardware was in place for a mean (SD) 180 (167) days. Sixty of the 150 patients (40.0%) had some form of follow-up, a mean (SD) 90 (113) days total after initial presentation. Thirteen patients experienced complications, for a total complication rate of 8.7%. Conclusions and relevance: Conservative management, using MMF and a soft diet, was favored for most operative pediatric mandible fractures. Open reduction internal fixation with titanium plating was less commonly used. Outcomes were favorable despite a lack of consistent follow-up. Level of evidence: 4.