Tiki1 is required for head formation via Wnt cleavage-oxidation and inactivation.

Secreted Wnt morphogens are signaling molecules essential for embryogenesis, pathogenesis, and regeneration and require distinct modifications for secretion, gradient formation, and activity. Whether Wnt proteins can be posttranslationally inactivated during development and homeostasis is unknown. Here we identify, through functional cDNA screening, a transmembrane protein Tiki1 that is expressed specifically in the dorsal Spemann-Mangold Organizer and is required for anterior development during Xenopus embryogenesis. Tiki1 antagonizes Wnt function in embryos and human cells via a TIKI homology domain that is conserved from bacteria to mammals and acts likely as a protease to cleave eight amino-terminal residues of a Wnt protein, resulting in oxidized Wnt oligomers that exhibit normal secretion but minimized receptor-binding capability. Our findings identify a Wnt-specific protease that controls head formation, reveal a mechanism for morphogen inactivation through proteolysis-induced oxidation-oligomerization, and suggest a role of the Wnt amino terminus in evasion of oxidizing inactivation. TIKI proteins may represent potential therapeutic targets.

Fibrosis and Mast Cells in Colorectal Lesions: Significance in Adenoma-Colorectal Cancer Sequence and Association with Diet.

PURPOSE: Adenoma is the most common benign neoplasm with potential to progress into colorectal cancer (CRC), a disease responsible for high rates of mortality. However, it is not possible yet to establish which lesions will evolve into CRC. We aimed to investigate the intrinsic factors, diet profile, and microenvironment as factors involved in adenoma-CRC progression. METHODS: We evaluated nutritional profile and microscopic features. Adenomas and CRC lesions were stained with Mallory's trichrome to reveal fibrosis and Alcian blue to identify mast cells. RESULTS: A total of 143 patients was selected, 66 % diagnosed with normal mucosa, 28.4 % with benign lesion, and 5.6 % with CRC. A higher frequency of lesions was associated with patients older than 50 years (26.57 %) and women (18.18 %), but men were more likely to develop CRC. Regarding microscopic aspects, epithelium-connective tissue interface with disorganization feature was significantly higher in CRC when compared to adenoma (P = 0.0007). A greater fibrosis around vessels was also observed in CRC (P = 0.01). The statistical analysis indicated a significant correlation between mast cell population and patients older than 50 years (P < 0.01), male (P < 0.01), with right colon lesion (P < 0.05) and CRC. Low consumption of leafy greens (P < 0.001) and carotenoids (P < 0.01) and elevated consumption of red meat (P < 0.001) were associated with a high density of mast cells. CONCLUSIONS: An association between clinical, diet profile, and microscopic features in colorectal lesions was observed, with a progressive change in the microenvironment during adenoma-CRC sequence.

Analysis of Estrogen Effects on Eruption of Rat Molars / Análisis de los Efectos del Estrógeno en la Erupción de Molares de Rata

ABSTRACT: Tooth eruption requires resorption of the alveolar bone interposed between the tooth germ and the oral mucosa (coronal bone). The cells responsible for bone resorption are the osteoclasts and their activity can be reduced or inactivated by estrogen hormone. We aimed to investigate the effects of estrogen on the process of tooth eruption in rats. Thirty-three Wistar rats, aged two-to-17-days, were divided into control, sham and estrogen-treated groups. After daily injections with estrogen, the animals were euthanized and the jaws removed and processed for histological analysis. We performed clinical examination, morphological analysis, quantification of the number of osteoclasts on the surface of the coronal bone and immunohistochemical analysis of estrogen receptor type alpha (ERα). Estrogen therapy was effective, which could be confirmed by the higher estrogen plasma levels on treated animals. However, it had no effect on tooth development or tooth eruption. Progressive bone resorption was observed and the number of osteoclasts on coronal bone was not affected on hormoneinjected animals, allowing tooth to erupt at the same time observed in untreated animals. Immunohistochemistry for ERα confirmed the presence of this type of receptor in osteoclasts, osteoblasts and osteocytes. Taken together, our results showed that estrogen stimulation was not sufficient to decrease the number of osteoclasts on the coronal bone, supporting the idea that, although estrogen may have a protective activity on bone resorption, this may not apply to the alveolar bone that is meant to be resorbed during eruptive process.

RESUMEN: La erupción dental requiere la resorción del hueso alveolar interpuesto entre el germen dental y la mucosa oral (hueso coronal). Las células responsables de la resorción ósea son los osteoclastos y su actividad puede reducirse o inactivarse por la hormona del estrógeno. Objetivos: apuntamos a investigar los efectos del estrógeno en el proceso de la erupción dental en ratas. Treinta y tres ratas Wistar, de dos a 17 días de edad, se dividieron en grupos de control, Sham y se trataron con estrógenos. Los animales fueron eutanizados después del tratamento con estrógeno y se procesaron las mandíbulas para el análisis histológico. Se realizó el examen clínico, el análisis morfológico, la cuantificación del número de osteoclastos en la superficie del hueso coronal y el análisis inmunohistoquímico del tipo de receptor de estrógeno alfa (ERα). La terapia de estrógeno fue eficaz, lo que podría ser confirmado por los niveles plasmáticos más altos de estrógeno en los animales tratados. Sin embargo, no se observó ningún efecto sobre el desarrollo de los dientes o la erupción dental. Se observó una resorción ósea progresiva y el número de osteoclastos en el hueso coronal no se vio afectado en los animales inyectados con hormonas, permitiendo que el diente erupcionó durante el mismo período de tiempo observado en animales no tratados. La inmunohistoquímica para el ERα confirmó la presencia de este tipo de receptor en los osteoclastos, osteoblastos y osteocitos. Nuestros resultados mostraron que la estimulación del estrógeno no fue suficiente para reducir el número de osteoclastos en el hueso coronal confirmando que, si bien el estrógeno puede tener una actividad protectora en la resorción ósea, esto puede no se aplica al hueso alveolar que está destinado a ser rerecurrido durante el proceso eruptivo.