Greater than 95% of infectious agents enter through exposed mucosal surfaces, such as the respiratory, gastrointestinal and genitourinary tracts. These include HIV, sexually transmitted diseases, numerous opportunistic infections, TB, many emerging and re-emerging infections, and biological warfare/terrorist agents, such as anthrax, Yersinia pestis and small pox. Most mucosal surfaces are lined by a monolayer of polarized epithelial cells, which forms the principal barrier to entry by infectious agents. In essence, the epithelial layer can be considered the most basic component of the innate mucosal immune system. Some pathogens cross the epithelial layer by disrupting it. Other pathogens exploit disruptions in the monolayer, which can be caused by tissue injury secondary to inflammation, trauma, or may result from cell death or division within the monolayer. To maintain their function as a barrier to infection, epithelial tissues have developed efficient wound healing mechanisms. Wound healing is central to mucosal defense against infection. The epithelial barrier must be restored as quickly as possible, to minimize the opportunity for entry of infectious agents. Some infectious agents, such as Pseudomonas aeruginosa, not only exploit pre-existing wounds, but also impede the wound healing process. We are studying epithelial wound healing by growing epithelial cells in 3 dimensional cultures of extracellular matrix, which causes the cells to more closely resemble in vivo conditions.
In Aim 1 we are using a system of human primary lung alveolar type II cells, which form alveolar-like cysts, as a model to study response to acute lung injury/acute respiratory distress syndrome.
In Aim 2, we are using a three-dimensional system of a well-differentiated human airway cell line, which forms cysts and tubules lined by pseudostratified epithelium, as a model to study airway response to injury.
In Aim 3 we are studying the roles of matrix metalloproteinases and sulfatases (enzymes that remove 6-O-sulfate groups from heparan sulfate proteoglycans) in our three dimensional culture systems. This work will be in collaboration with Projects 2, 3 and 4, and supported by Cores B and C. Most infectious agents enter through the layer of cells that lines internal organs, such as the lung. Injuries to this cell layer makes it much easier for pathogens to enter and we are studying how the cell layer heals itself.
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