Protective effect of PAR4 expressed on hematopoietic cells in bleomycin-injured lungs. WT mice were irradiated and underwent transplantation with PN-1^−/−/Par4^+/+ or PN-1^+/+/Par4^−/− or PN-1^+/+/Par4^+/+ or PN-1^−/−/Par4^−/− BM and allowed to recover for 5 weeks before bleomycin-induced lung injury. PN-1^−/−/Par4^+/+ BM → WT (n = 10). PN-1^+/+/Par4^−/− BM → WT (n = 12). PN-1^+/+/Par4^+/+ BM → WT (n = 8). PN-1^−/−/Par4^−/− BM → WT (n = 12). (A) Percentages of surviving mice undergoing transplantation were plotted over a 14-day period after bleomycin treatment. Log-rank test was used to compare the difference between recipient mice: P = .01 for PN-1^−/−/Par4^+/+ BM → WT vs PN-1^+/+/Par4^+/+ BM → WT. (B) Masson’s trichrome and Sirius red stainings of lung withdrawn the day of euthanasia from WT chimeric mice. Representative images are shown. Scale bars, 500 µm.