Tracheobronchomalacia is a common congenital defect in which the walls of the trachea and bronchi lack of adequate cartilage required for support of the airways. Deletion of Wls, a cargo receptor mediating Wnt ligand secretion, in the embryonic endoderm using ShhCre mice inhibited formation of tracheal-bronchial cartilaginous rings. The normal dorsal-ventral patterning of tracheal mesenchyme was lost. Smooth muscle cells, identified by Acta2 staining, were aberrantly located in ventral mesenchyme of the trachea, normally the region of Sox9 expression in cartilage progenitors. Wnt/β-catenin activity, indicated by Axin2 LacZ reporter, was decreased in tracheal mesenchyme of Wlsf/f;ShhCre/+ embryos. Proliferation of chondroblasts was decreased and reciprocally, proliferation of smooth muscle cells was increased in Wlsf/f;ShhCre/+ tracheal tissue. Expression of Tbx4, Tbx5, Msx1 and Msx2, known to mediate cartilage and muscle patterning, were decreased in tracheal mesenchyme of Wlsf/f;ShhCre/+ embryos. Ex vivo studies demonstrated that Wnt7b and Wnt5a, expressed by the epithelium of developing trachea, and active Wnt/β-catenin signaling are required for tracheal chondrogenesis before formation of mesenchymal condensations. In conclusion, Wnt ligands produced by the tracheal epithelium pattern the tracheal mesenchyme via modulation of gene expression and cell proliferation required for proper tracheal cartilage and smooth muscle differentiation.
Tracheobronchomalacia (TBM) is a common congenital disorder in which the cartilaginous rings of the trachea are weakened or missing. Despite the high prevalence and clinical issues associated with TBM, the etiology is largely unknown. Our previous studies demonstrated that Wntless (Wls) and its associated Wnt pathways are critical for patterning of the upper airways. Deletion of Wls in respiratory endoderm caused TBM and ectopic trachealis muscle. To understand mechanisms by which Wls mediates tracheal patterning, we performed RNA sequencing in prechondrogenic tracheal tissue of Wls;Shh embryos. Chondrogenic Bmp4, and Sox9 were decreased, while expression of myogenic genes was increased. We identified Notum, a deacylase that inactivates Wnt ligands, as a target of Wls induced Wnt signaling. Notum's mesenchymal ventral expression in prechondrogenic trachea overlaps with expression of Axin2, a Wnt/β-catenin target and inhibitor. Notum is induced by Wnt/β-catenin in developing trachea. Deletion of Notum activated mesenchymal Wnt/β-catenin and caused tracheal mispatterning of trachealis muscle and cartilage as well as tracheal stenosis. Notum is required for tracheal morphogenesis, influencing mesenchymal condensations critical for patterning of tracheal cartilage and muscle. We propose that Notum influences mesenchymal cell differentiation by generating a barrier for Wnt ligands produced and secreted by airway epithelial cells to attenuate Wnt signaling.
Background Pediatric renal cell carcinoma (pRCC) is the second most common renal malignancy of childhood; however, treatment data for advanced disease is lacking. Methods A retrospective analysis of pRCC patients (age < 21 years at diagnosis) treated between 2000 and 2015 at Cincinnati Children's Hospital Medical Center was undertaken, with specific focus on medical therapies, accompanied by a detailed literature review. Results Twenty‐four patients (median age = 15 years) were identified; 11 were female. Past history of kidney pathology (4) and prior hematologic/oncologic diagnoses (5) were common associated findings. Translocation morphology RCC (tRCC) was the most common subtype (16; 64%), followed by papillary (6; 24%), clear cell renal cell carcinoma (ccRCC) (1), and chromophobe (1). The TNM stage distribution was I (8; 33%), II (2; 8%), III (3; 13%), and IV (11; 46%). Eleven patients with stage IV disease all had tRCC and received medicinal anticancer therapies, the most common being antiangiogenic (10), conventional chemotherapy (8), mTOR inhibition (7), and immunotherapy (3). Four patients also received small‐port radiotherapy. The mean time to progression (TTP) was longest for axitinib (n = 2; TTP = 7.8 m; range 5.5‐10 m) and sunitinib (n = 6; TTP = 4.7 m; range 0.3–12 m). Overall, 20 cases of pediatric RCC who received RCC‐directed medicinal therapy with outcome data have been previously reported. Conclusions For patients with unresectable pRCC requiring systemic therapy, available data are scarce. Data herein support an increased TTP with antiangiogenic therapy in tRCC supporting a formal study of antiangiogenic therapies through multicooperative‐group collaboration.
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