PGR and lymphangioleiomyomatosis: Taken together, these findings, along with the decreased myofiber cross-sectional area (CSA) (Figure 3, C and E) and proportion (Figure 4C and Supplemental Figure 5, A and B) in EP LAM compared with Veh and EPR LAM, suggest that EP LAM myofibers are undergoing atrophy and that Pgr+ fibroblasts, Pgr– fibroblasts, and mesothelial-like cells may contribute to this process through TGF-β pathway signaling.