Project 3: In Project 3, we are working on the theory that PAH can be treated by fixing cell-cell junctions in blood vessels with a drug called recombinant ACE2(angiotensin converting enzyme 2). This is the only approach so far that has worked to reverse disease in mouse models of heritable PAH, but we need to better understand how it is working and make sure it has long term safety in animal models before starting human trials, hopefully within a few years. Definition: Cell-cell junctions-all of our organs and body structures are made from cells. Normally, these cells (think of a balloon filled with water) line up right next to each other so that the cell membranes touch each other. Materials can flow from one cell to the next. In PAH patients it is believed that the cells in the linings of the small arteries are not able to line up together as they should.