ABSTRACT
Type XVIII collagen is a multidomain protein that contains cleavable C-terminal NC1 and endostatin fragments, which have been shown to either induce or inhibit cell migration. Endostatin is being intensely studied because of its anti-angiogenic activity. Three variants of type XVIII collagen have been reported to be distributed in epithelial and endothelial basement membranes in a tissue-specific manner. The single gene encoding collagen XVIII is on chromosome 21 within the region associated with the congenital heart disease phenotype observed in Down's syndrome. In this study, we investigated the expression pattern of collagen XVIII in embryonic mouse hearts during formation of the atrioventricular (AV) valves. We found that collagen XVIII is localized not only in various basement membranes but is also highly expressed throughout the connective tissue core of the endocardial cushions and forming AV valve leaflets. It was closely associated with the epithelial-mesenchymal transformation of endothelial cells into mesenchymal cushion tissue cells and was localized around these cells as they migrated into the cardiac jelly to form the initial connective tissue elements of the valve leaflets. However, after embryonic day 17.5 collagen XVIII expression decreased rapidly in the connective tissue and thereafter remained detectable only in the basement membranes of the endothelial layer covering the leaflets. The staining pattern observed within the AV endocardial cushions suggests that collagen XVIII may have a role in cardiac valve morphogenesis. These results may help us to better understand normal heart development and the aberrant mechanisms that cause cardiac malformations in Down's syndrome.
Subject(s)
Collagen Type XVIII/physiology , Endostatins/physiology , Heart Valves/embryology , Animals , Down Syndrome/embryology , Down Syndrome/pathology , Epithelium/embryology , Epithelium/physiology , Epithelium/ultrastructure , Female , Heart Defects, Congenital/embryology , Heart Defects, Congenital/pathology , Heart Valves/physiology , Heart Valves/ultrastructure , Male , Mesoderm/enzymology , Mesoderm/physiology , Mesoderm/ultrastructure , Mice , Mice, Inbred C57BL , Microscopy, ImmunoelectronABSTRACT
The purpose of this study was to evaluate, retrospectively, the profile of patients with oral squamous cell carcinoma. They were referred to two hospitals of Belo Horizonte (MG, Brazil) between 1986 and 1996. The medical records of 740 patients presenting oral squamous cell carcinoma were reviewed in detail. The TNM classification and staging, age, gender, race, occupation, and site of the primary tumor were recorded. The male-to-female ratio was 4.8:1. The mean age was 58.6 years. Most of the patients were in their sixties and were farm workers. The tumors were found principally on the tongue. There was a close relationship between some habits (tobacco and alcohol consumption) and the development of oral squamous cell carcinoma. Most of the patients sought medical care in the first year, even though almost half of them had lesions in stage T4. The identification of the characteristics of this specific population might reflect either accomplishments or problems in oral cancer control and can enable the development of a primary prevention program for oral squamous cell carcinoma.