Laryngotracheal transplantation: technical modifications and functional outcomes.

OBJECTIVES/HYPOTHESIS: Laryngeal transplantation offers the potential for patients without a larynx to recover their voice, which is critical in our communication age. We report clinical and functional outcomes from a laryngotracheal transplant. Widespread adoption of this technique has been slowed due to the ethical concerns of life-long immunosuppression after a nonvital organ transplant. Our patient was already on immunosuppressive medication from prior kidney-pancreas transplantation, and therefore was not exposed to added long-term risk. We describe the unique technical advances, clinical course, and rehabilitation of this patient and the implications for future laryngeal transplantation. STUDY DESIGN: Case report. METHODS: A laryngotracheal transplantation was performed in a 51-year-old prior kidney-pancreas transplant recipient presenting with complete laryngotracheal stenosis. Surgical modifications were made in the previously described technique related to retrieval, vascular supply, and reinnervation. This resulted in a robustly vascularized organ with well-perfused long-segment tracheal transplant and early return of motor reinnervation. RESULTS: A multidisciplinary approach resulted in a successful transplant without evidence of rejection to date. Postoperatively, the patient continues to rely on a tracheotomy but has had the return of an oral and nasal airway, vocalization, smell, and taste, all experienced for the first time in 11 years. CONCLUSIONS: We have demonstrated that our methods may result in a successful laryngotracheal transplant. We describe the preparation, surgical technique, rehabilitation, and interventions employed in achieving optimal outcomes. This report contributes valuable information on this rarely performed composite transplant.

Identification of novel ciliogenesis factors using a new in vivo model for mucociliary epithelial development.

Mucociliary epithelia are essential for homeostasis of many organs and consist of mucus-secreting goblet cells and ciliated cells. Here, we present the ciliated epidermis of Xenopus embryos as a facile model system for in vivo molecular studies of mucociliary epithelial development. Using an in situ hybridization-based approach, we identified numerous genes expressed differentially in mucus-secreting cells or in ciliated cells. Focusing on genes expressed in ciliated cells, we have identified new candidate ciliogenesis factors, including several not present in the current ciliome. We find that TTC25-GFP is localized to the base of cilia and to ciliary axonemes, and disruption of TTC25 function disrupts ciliogenesis. Mig12-GFP localizes very strongly to the base of cilia and confocal imaging of this construct allows for simple visualization of the planar polarity of basal bodies that underlies polarized ciliary beating. Knockdown of Mig12 disrupts ciliogenesis. Finally, we show that ciliogenesis factors identified in the Xenopus epidermis are required in the midline to facilitate neural tube closure. These results provide further evidence of a requirement for cilia in neural tube morphogenesis and suggest that genes identified in the Xenopus epidermis play broad roles in ciliogenesis. The suites of genes identified here will provide a foundation for future studies, and may also contribute to our understanding of pathological changes in mucociliary epithelia that accompany diseases such as asthma.

Divergent and convergent effects on gene expression and function in acute versus chronic endothelial activation.

Activation of the vascular endothelium with cytokines such as TNF is widely used to study the role of the vasculature in proinflammatory disease. To gain insight into mechanisms of prolonged vascular endothelial activation we compared changes in gene expression induced by continuous activation in stable tmTNF-expressing cells with changes due to acute TNF challenge in vitro. Affymetrix Genechip analysis was performed on RNA from control, acute and continuous TNF-activated endothelial cells. Only 36% of the significant changes in gene expression were convergent between the acute and continuously activated endothelial cells compared with the control. From the divergently regulated genes, for example the cytokine ENA-78 was specifically induced in chronically activated cells, while E-selectin, a cell adhesion molecule, was upregulated only in acutely activated endothelial cells. Antioxidant SOD gene induction was noted in acute activation, while a regulatory NADPH oxidase subunit was selectively upregulated in continuously activated endothelium in accordance with significant reactive oxygen species induction occurred only in these cells. Accordingly, p38 and ERK1/2, two MAP kinases downstream of reactive oxygen species, were activated in stable transmembrane-spanning precursor (tm) TNF-expressing cells and were refractory to activation with soluble TNF or VEGF. In consequence, the increased p38 MAP kinase activity contributed to increased endothelial cell migration in tmTNF-expressing cells. These data suggest that continuous activation of endothelial cells leads to specific expression and functional changes, consistent with alterations observed in dysfunctional endothelium exposed to or involved in chronic inflammation.

Global analysis of gene expression in Xenopus hindlimbs during stage-dependent complete and incomplete regeneration.

Xenopus laevis tadpoles are capable of limb regeneration after amputation, in a process that initially involves the formation of a blastema. However, Xenopus has full regenerative capacity only through premetamorphic stages. We have used the Affymetrix Xenopus laevis Genome Genechip microarray to perform a large-scale screen of gene expression in the regeneration-complete, stage 53 (st53), and regeneration-incomplete, stage 57 (st57), hindlimbs at 1 and 5 days postamputation. Through an exhaustive reannotation of the Genechip and a variety of comparative bioinformatic analyses, we have identified genes that are differentially expressed between the regeneration-complete and -incomplete stages, detected the transcriptional changes associated with the regenerating blastema, and compared these results with those of other regeneration researchers. We focus particular attention on striking transcriptional activity observed in genes associated with patterning, stress response, and inflammation. Overall, this work provides the most comprehensive views yet of a regenerating limb and different transcriptional compositions of regeneration-competent and deficient tissues.

An examination of non-formalin-based fixation methods for Xenopus embryos.

Despite the growing availability of non-formalin-based fixatives, the vast majority of researchers in developmental biology continue to fix embryos and tissue in 4% paraformaldehyde. This fixation method has proven useful for both immunohistochemistry and in situ hybridization, yet working with paraformaldehyde has distinct disadvantages in its toxicity and the short shelf life of prepared solutions. In a search for viable alternative fixatives, we have evaluated two non-formalin-based commercial products, FineFIX (Milestone Microwave Laboratory System) and NOTOXhisto (Scientific Device Laboratory). These products were tested side-by-side with a commonly used 4% paraformaldehyde solution (MEMPFA) on Xenopus laevis embryos and assayed using whole mount immunohistochemistry and whole mount in situ hybridization. The results indicate that NOTOXhisto can be used as a substitute for MEMPFA in both tested Xenopus protocols with no loss of sensitivity or tissue morphology.

Cardiovascular gene expression profiles of dioxin exposure in zebrafish embryos.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a widespread environmental contaminant that causes altered heart morphology, circulatory impairment, edema, hemorrhage, and early life stage mortality in fish. TCDD toxicity is dependent, in large part, on the aryl hydrocarbon receptor (AHR), but understanding of the molecular mechanism of cardiovascular embryotoxicity remains incomplete. To identify genes potentially involved in cardiovascular effects, we constructed custom cDNA microarrays consisting of 4896 zebrafish adult heart cDNA clones and over 200 genes with known developmental, toxicological and housekeeping roles. Gene expression profiles were obtained for 3-day-old zebrafish after early embryonic exposure to either 0.5 or 5.0 nM TCDD. In all, 516 clones were significantly differentially expressed (p < 0.005) under at least one treatment condition; 123 high-priority clones were selected for further investigation. Cytochromes P450 1A and 1B1, and other members of the AHR gene battery, were strongly and dose-dependently induced by TCDD. Importantly, altered expression of cardiac sarcomere components, including cardiac troponin T2 and multiple myosin isoforms, was consistent with the hypothesis that TCDD causes dilated cardiomyopathy. Observed increases in expression levels of mitochondrial energy transfer genes also may be related to cardiomyopathy. Other TCDD-responsive genes included fatty acid and steroid metabolism enzymes, ribosomal and signal-transduction proteins, and 18 expressed sequence tags (ESTs) with no known protein homologs. As the first broad-scale study of TCDD-modulated gene expression in a non-mammalian system, this work provides an important perspective on mechanisms of TCDD toxicity.

Cardiac output monitoring during off-pump coronary artery bypass grafting.

OBJECTIVE: To evaluate and compare monitors of cardiac output during repositioning and stabilization of the heart for off-pump coronary artery bypass (OPCAB) surgery. DESIGN: Prospective, observational, clinical study. SETTING: University teaching hospital. PARTICIPANTS: Consecutive patients scheduled to undergo elective OPCAB (n = 19). INTERVENTIONS: Monitoring, induction, and anesthesia followed a routine protocol for coronary artery bypass patients. This included the use of transesophageal echocardiography (TEE) and pulmonary artery catheter placement. MEASUREMENTS AND MAIN RESULTS: After positioning and stabilization for OPCAB surgery, the changes in descending aortic flow velocity (VTI) times heart rate (HR) and the mixed venous oxygen saturation (SvO(2)) could be used to predict the changes in thermodilution cardiac output (TDCO) using the following model: deltaTDCO((calc))=-13.15+0.35(deltaVTI*HR)+0.61(deltaSvO(2)) where Delta indicates the percentage change from baseline values. The changes in mean arterial pressure, mean pulmonary artery pressure, and continuous cardiac output did not correlate with the changes in TDCO. CONCLUSION: The use of the VTI*HR, as determined by TEE, in addition to the SvO(2) can strengthen clinical decision making during repositioning and stabilization of the heart during OPCAB. Changes in the VTI*HR and SvO(2) can be used as surrogate markers for changes in CO during OPCAB surgery.