Thoracic aortic aneurysm in an adolescent with intraoperative discovery of contained rupture: a case report.

Background: As surgical recommendations in adults based on size criteria of ascending aortic aneurysms become more refined, criteria for childhood/adolescence remains less clear. Multiple pathologic factors may predispose younger patients to thoracic aortic aortopathy and increase the risk of rupture. An evolving field of research is how to identify thoracic aortic dilation earlier in patients, risk stratify, and to obtain objective measures beyond size for proceeding with surgical intervention in order to prevent catastrophic thoracic aortic dissection. Case Description: We report an adolescent case of dilated ascending aortic aneurysm with a functionally unicuspid/bicuspid aortic valve. This patient was taken to surgery electively, given the gradual increasing size of the ascending aorta. Intraoperatively, there was an unexpected intraoperative finding of a contained aortic rupture. The patient underwent an aortic root replacement with mechanical valve composite graft and coronary artery reimplantation (modified Bentall) with ascending hemiarch replacement. The patient did well with no post-operative complications. Aortic pathology and genetic analysis were performed. The patient was discovered to have a heterozygous variant in PTPN11 which is typically associated with Noonan syndrome; however, this is not known to be associated with aortopathy. Conclusions: As criteria for surgical intervention in adult thoracic ascending aortic aneurysms continues to evolve, this case illustrates challenges when determining the optimal criteria for surgical intervention in adolescent patients.

A Quality Improvement Project to Improve First Case On-time Starts in the Pediatric Operating Room.

BACKGROUND: Delays in the operating room (OR) can lead to increased hospital costs as well as patient and provider dissatisfaction. Starting the first case on time in the OR can potentially prevent subsequent delays. We designed a quality improvement project to improve the first case on-time starts in the pediatric OR at a tertiary care children's hospital. METHODS: Following the collection of baseline data, we formed an interdisciplinary team. We analyzed the causes of delay and used the Six Sigma methodology of Define, Measure, Analyze, Improve, and Control. We identified key drivers and implemented several low-cost interventions using Plan-Do-Study-Act cycles. Major interventions included preoperative care coordination, strategic staggering of OR cases, and introduction of "Wow Bucks" incentives. We monitored start times and the delay in minutes for all first cases weekly. The OR minutes saved per week were calculated and used to estimate cost savings. RESULTS: We studied a total of 1981 first-start cases from May 2018 to October 2019. The first case on-time starts improved from 62% to 77% over the study period. There was a significant improvement in total minutes delayed for all the first cases from 197.9 minutes per week down to 133 minutes per week (P < 0.05). Estimated cost savings were $4,023 per week due to improved OR utilization. CONCLUSIONS: A multidisciplinary collaborative team approach using quality improvement tools can improve on-time starts in the pediatric OR.

BMP signaling is required for RUNX2-dependent induction of the osteoblast phenotype.

UNLABELLED: RUNX2 expression in mesenchymal cells induces osteoblast differentiation and bone formation. BMP blocking agents were used to show that RUNX2-dependent osteoblast differentiation and transactivation activity both require BMP signaling and, further, that RUNX2 enhances the responsiveness of cells to BMPs. INTRODUCTION: BMPs and the RUNX2 transcription factor are both able to stimulate osteoblast differentiation and bone formation. BMPs function by activating SMAD proteins and other signal transduction pathways to stimulate expression of many target genes including RUNX2. In contrast, RUNX2 induces osteoblast-specific gene expression by directly binding to enhancer regions in target genes. In this study, we examine the interdependence of these two factors in controlling osteoblast differentiation in mesenchymal progenitor cells. MATERIALS AND METHODS: C3H10T1/2 mesenchymal cells and primary cultures of marrow stromal cells were transduced with a RUNX2 adenovirus and treated with BMP blocking antibodies or the natural antagonist, NOGGIN. Osteoblast differentiation was determined by assaying alkaline phosphatase and measuring osteoblast-related mRNA using quantitative RT/PCR. Activation of BMP-responsive signal transduction pathways (SMAD, extracellular signal-regulated kinase [ERK], p38, and c-jun-N-terminal kinase [JNK]) was assessed on Western blots. RESULTS AND CONCLUSIONS: C3H10T1/2 cells constitutively synthesize BMP2 and 4 mRNA and protein, and this BMP activity is sufficient to activate basal levels of SMAD phosphorylation. Inhibition of BMP signaling was shown to disrupt the ability of RUNX2 to stimulate osteoblast differentiation and transactivate an osteocalcin gene promoter-luciferase reporter in C3H10T1/2 cells. BMP blocking antibodies also inhibited RUNX2-dependent osteoblast differentiation in primary cultures of murine marrow stromal cells. Conversely, RUNX2 expression synergistically stimulated BMP2 signaling in C3H10T1/2 cells. However, RUNX2 did not increase the ability of this BMP to activate SMAD, ERK, p38, and JNK pathways. This study shows that autocrine BMP production is necessary for the RUNX2 transcription factor to be active and that BMPs and RUNX2 cooperatively interact to stimulate osteoblast gene expression.

Cooperative interactions between activating transcription factor 4 and Runx2/Cbfa1 stimulate osteoblast-specific osteocalcin gene expression.

The role of ATF4 (activating transcription factor 4) in osteoblast differentiation and bone formation was recently described using ATF4-deficient mice (Yang, X., Matsuda, K., Bialek, P., Jacquot, S., Masuoka, H. C., Schinke, T., Li, L., Brancorsini, S., Sassone-Corsi, P., Townes, T. M., Hanauer, A., and Karsenty, G. (2004) Cell 117, 387-398). However, the mechanisms of ATF4 in bone cells are still not clear. In this study, we determined the molecular mechanisms through which ATF4 activates the mouse osteocalcin (Ocn) gene 2 (mOG2) expression and mOG2 promoter activity. ATF4 increased the levels of Ocn mRNA and mOG2 promoter activity in Runx2-containing osteoblasts but not in non-osteoblastic cells that lack detectable Runx2 protein. However, ATF4 increased Ocn mRNA and mOG2 promoter activity in non-osteoblastic cells when Runx2 was co-expressed. Mutational analysis of the OSE1 (ATF4-binding site) and the two OSE2s (Runx2-binding sites) in the 657-bp mOG2 promoter demonstrated that ATF4 and Runx2 activate Ocn via cooperative interactions with these sites. Pull-down assays using nuclear extracts from osteoblasts or COS-7 cells overexpressing ATF4 and Runx2 showed that both factors are present in either anti-ATF4 and anti-Runx2 immunoprecipitates. In contrast, pull-down assays using purified glutathione S-transferase fusion proteins were unable to demonstrate a direct physical interaction between ATF4 and Runx2. Thus, accessory factors are likely involved in stabilizing interactions between these two molecules. Regions within Runx2 required for ATF4 complex formation and activation were identified. Deletion analysis showed that the leucine zipper domain of ATF4 is critical for Runx2 activation. This study is the first demonstration that cooperative interactions between ATF4 and Runx2/Cbfa1 stimulate osteoblast-specific Ocn expression and suggests that this regulation may represent a novel intramolecular mechanism regulating Runx2 activity and, thereby, osteoblast differentiation and bone formation.

Parathyroid hormone induction of the osteocalcin gene. Requirement for an osteoblast-specific element 1 sequence in the promoter and involvement of multiple-signaling pathways.

Parathyroid hormone (PTH) is an important peptide hormone regulator of bone formation and osteoblast activity. However, its mechanism of action in bone cells is largely unknown. This study examined the effect of PTH on mouse osteocalcin gene expression in MC3T3-E1 preosteoblastic cells and primary cultures of bone marrow stromal cells. PTH increased the levels of osteocalcin mRNA 4-5-fold in both cell types. PTH also stimulated transcriptional activity of a 1.3-kb fragment of the mouse osteocalcin gene 2 (mOG2) promoter. Inhibitor studies revealed a requirement for protein kinase A, protein kinase C, and mitogen-activated protein kinase pathways in the PTH response. Deletion of the mOG2 promoter sequence from -1316 to -116 caused no loss in PTH responsiveness whereas deletion from -116 to -34 completely prevented PTH stimulation. Interestingly, this promoter region does not contain the RUNX2 binding site shown to be necessary for PTH responsiveness in other systems. Nuclear extracts from PTH-treated MC3T3-E1 cells exhibited increased binding to OSE1, a previously described osteoblast-specific enhancer in the mOG2 promoter. Furthermore, mutation of OSE1 in DNA transfection assays established the requirement for this element in the PTH response. Collectively, these studies establish that actions of PTH on the osteocalcin gene are mediated by multiple signaling pathways and require OSE1 and associated nuclear proteins.