RXFP1 and idiopathic pulmonary fibrosis: The findings in both SSc and IPF support that the lack of or reduced expression of RXFP1 in fibrotic tissues of IPF and SSc contributes to the failed responses to relaxin for IPF lung fibroblasts in vitro and relaxin‐based therapies in SSc clinical trials (Casten & Boucek, 1958; Jefferis & Dixon, 1962; Khanna et al., 2009; Tan et al., 2016).