Faculty Bibliography

This retrospective, matched-cohort study analyzed 1,556 patients with diabetic ulcers treated at 470 wound centers throughout the United States to determine the effectiveness of a cryopreserved bioactive split-thickness skin allograft plus standard of care when compared to standard of care alone. There were 778 patients treated with the graft in the treatment cohort, who were paired with 778 patients drawn from a pool of 126,864 candidates treated with standard of care alone (controls), by using propensity matching to create nearly identical cohorts. Both cohorts received standard wound care, including surgical debridement, moist wound care, and offloading. Logistic regression analysis of healing rates according to wound size, wound location, wound duration, volume reduction, exposed deep structures, and Wagner grade was performed. Amputation rates and recidivism at 3 months, 6 months, and 1 year after wound closure were analyzed. Diabetic ulcers were 59% more likely to close in the treatment cohort compared to the control cohort (p = .0045). The healing rate with the graft was better than standard of care across multiple subsets, but the most significant improvement was noted in the worst wounds that had a duration of 90-179 days prior to treatment (p =.0073), exposed deep structures (p = .036), and/or Wagner Grade 4 ulcers (p = 0.04). Furthermore, the decrease in recidivism was statistically significant at 3 months, 6 months, and 1 year, with and without initially exposed deep structures (p < .05). The amputation rate in the treatment cohort was 41.7% less than that of the control cohort at 20 weeks (0.9% vs 1.5%, respectively). This study demonstrated that diabetic ulcers treated with a cryopreserved bioactive split-thickness skin allograft were more likely to heal and remain closed compared to ulcers treated with standard of care alone. This article is protected by copyright. All rights reserved.

Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by insulin deficiency, and patients with diabetes have an increased risk of bone fracture and significantly impaired fracture healing. Proinflammatory cytokine tumor necrosis factor-alpha is significantly upregulated in diabetic fractures and is believed to underlie delayed fracture healing commonly observed in diabetes. Our previous genetic screen for the binding partners of progranulin (PGRN), a growth factor-like molecule that induces chondrogenesis, led to the identification of tumor necrosis factor receptors (TNFRs) as the PGRN-binding receptors. In this study, we employed several in vivo models to ascertain whether PGRN has therapeutic effects in diabetic fracture healing. Here, we report that deletion of PGRN significantly delayed bone fracture healing and aggravated inflammation in the fracture models of mice with T1DM. In contrast, recombinant PGRN effectively promoted diabetic fracture healing by inhibiting inflammation and enhancing chondrogenesis. In addition, both TNFR1 proinflammatory and TNFR2 anti-inflammatory signaling pathways are involved in PGRN-stimulated diabetic fracture healing. Collectively, these findings illuminate a novel understanding concerning the role of PGRN in diabetic fracture healing and may have an application in the development of novel therapeutic intervention strategies for diabetic and other types of impaired fracture healing.

PURPOSE/OBJECTIVE:Genetically engineered mouse models of sporadic cancers are critical for studying tumor biology and for preclinical testing of therapeutics. We present an MRI-based pipeline designed to produce high resolution, quantitative information about tumor progression and response to novel therapies in mouse models of medulloblastoma (MB). METHODS:Sporadic MB was modeled in mice by inducing expression of an activated form of the Smoothened gene (aSmo) in a small number of cerebellar granule cell precursors. aSmo mice were imaged and analyzed at defined time-points using a 3D manganese-enhanced MRI-based pipeline optimized for high-throughput. RESULTS:A semi-automated segmentation protocol was established that estimates tumor volume in a time-frame compatible with a high-throughput pipeline. Both an empirical, volume-based classifier and a linear discriminant analysis-based classifier were tested to distinguish progressing from nonprogressing lesions at early stages of tumorigenesis. Tumor centroids measured at early stages revealed that there is a very specific location of the probable origin of the aSmo MB tumors. The efficacy of the manganese-enhanced MRI pipeline was demonstrated with a small-scale experimental drug trial designed to reduce the number of tumor associated macrophages and microglia. CONCLUSION/CONCLUSIONS:Our results revealed a high level of heterogeneity between tumors within and between aSmo MB models, indicating that meaningful studies of sporadic tumor progression and response to therapy could not be conducted without an imaging-based pipeline approach.

PURPOSE/OBJECTIVE:To investigate the effect of a change in USMLE Step 1 timing on Step 2 Clinical Knowledge (CK) scores, the effect of lag-time on Step 2 CK performance, and the relationship of incoming MCAT score to Step 2 CK performance pre- and post-change. METHOD/METHODS:Four LCME-accredited schools that moved Step 1 after core clerkships between academic years 2008-2009 and 2017-2018 were analyzed in a pre-post format. Standard t-tests were used to examine the change in Step 2 CK scores pre- and post-change. Tests of differences in proportions were used to evaluate whether Step 2 CK failure rates differed between curricular change groups. Linear regressions were used to examine the relationships between Step 2 CK performance, lag-time and incoming MCAT score, and curricular change group. RESULTS:Step 2 CK performance did not change significantly (P = .20). Failure rates remained highly consistent (pre-change: 1.83%, post-change: 1.79%). The regression indicated that lag-time had a significant effect on Step 2 CK performance, with scores declining with increasing lag-time. The regression yielded small but significant interaction effects between MCAT and Step 2 CK scores. Students with lower incoming MCATs tended to perform better on Step 2 CK when Step 1 was after clerkships. CONCLUSIONS:Moving Step 1 after core clerkships appears to have had no significant impact on Step 2 CK scores or failure rates, supporting the argument that such a change is noninferior to the traditional model. Students with lower MCAT scores benefit most from the change.

DNA combing technology is a powerful methodology for the study of DNA replication in vivo. This tool can be used to identify origins of replication, assess of directionality of forks, and measure fork speed. Over the years, the method has been used extensively to study nuclear DNA replication. The first step involves the incorporation of thymidine analogs (CldU and IdU) into nascent DNA chains and followed by their visualization with immunofluorescence using antibodies that can distinguish the two analogs. Recently, we adapted and fine-tuned DNA combing technology to the specifics of mitochondrial DNA (Phillips et al., 2017, p. 155). The protocol, which we termed mito-SMARD (mitochondrial single molecule analysis of replication DNA), provides in vivo insight into mitochondrial DNA (mtDNA) replication with high resolution.

Background/UNASSIGNED:Cartilage defects account for substantial economic and humanistic burdens and pose a significant clinical problem. The efficacy of clinical approaches to cartilage repair is often inadequate, in part, owing to the restricted proliferative capacity of chondrocytes. Molecules have the capacity to promote the differentiation of multipotent mesenchymal stem cells into chondrocytes and may also gain the ability to repair the damaged cartilage. Objective/UNASSIGNED:This study aimed to investigate the role of Atsttrin (progranulin-derived engineered protein) in cartilage repair as well as the signaling pathway involved. Methods/UNASSIGNED:. Real-time polymerase chain reaction and Western blot analysis were used to monitor the effect of Atsttrin on the transcriptional and protein levels, respectively, of key anabolic and catabolic signaling molecules. Results/UNASSIGNED:In addition, Atsttrin-mediated cartilage repair occurred primarily through tumor necrosis factor receptor 2-initiated Akt signaling and downstream JunB transcription factor. Conclusion/UNASSIGNED:Atsttrin might serve as a promising therapeutic modality for cartilage regeneration.

Mitochondria and their associated membranes actively participate in biosynthesis, trafficking, and degradation of cellular phospholipids. Two crucial lipid biosynthetic activities of mitochondria include (i) the decarboxylation of phosphatidylserine to phosphatidylethanolamine and (ii) the de novo synthesis of cardiolipin. Here we describe protocols to measure these two activities, applying isotope-labeled or exogenous substrates in combination with thin-layer chromatography or mass spectrometry.