The BMP signaling pathway has also been implicated in the regulation of adult lung homeostasis and tissue repair following injury [27, 28, 29, 30, 31] . Several BMP ligands have been found upregulated in allergen challenged lungs [27] and notably, ectopic expression of gremlin by adenovirus mediated gene transfer in the lung of adult rats causes severe pulmonary fibrosis [32] illustrating the importance of the BMP pathway for lung homeostasis as well. Consistently, over-expression of gremlin has been observed in humans suffering from Idiopathic Pulmonary Fibrosis (IPF) [28, 29] .