KRT18 and acute respiratory distress syndrome: Since Krt8/Krt18-expressing transitional cells are overrepresented in both ARDS and end-stage fibrotic lung disease [162,169], accumulation of Krt8/Krt18-expressing transitional cells after lung injury could signal the presence of a maladaptive damage-and-repair cycle that inhibits AT2-to-AT1 transdifferentiation.