Figure 4. WNTs in BMMΦ CM are required to inhibit RIGS in Csf1r.iCre;Porcn^fl/fl mice exposed to AIR.

(a) Experimental design for partial body irradiation. Mice exposed to AIR were treated with WT or Porcn-null BMMΦ CM at 1 and 24 h post exposure. (b) Kaplan–Meier survival analysis of Csf1r.iCre;Porcn^fl/fl mice (n=10 per group) receiving CM (500 μl per mice i.v.) derived from WT or Porcn-null BMMΦ at 1 h and 48 h post AIR (18 Gy). Mice receiving WT BMMΦ CM showed 60% survival beyond 20 days compared with mice receiving Porcn-null BMMΦ CM or EV-depleted WT BMMΦ CM, where 100% of mice died within 12 days after irradiation (P<0.002 and P<0.003, respectively, Log-rank (Mantel–Cox) test). Reagent used for chemical depletion of EV did not confer any toxicity to normal mice. (c) HE-stained representative transverse sections of duodenum, jejunum and ileum from Csf1r.iCre;Porcn^fl/fl mice (n=3 per group). Note, restitution on crypt villus structure in irradiated Csf1r.iCre;Porcn^fl/fl mice receiving WT BMMΦ CM. However, treatment with Porcn-null BMMΦ CM or αMEM growth medium showed significant loss of crypts along with villi denudation. (d) Histogram demonstrating number of crypts mm⁻¹ in duodenal, jejuna, and illeul sections of Csf1r.iCre;Porcn^fl/fl mice. Irradiated Csf1r.iCre;Porcn^fl/fl mice receiving WT BMMΦ CM showed less crypt loss compared with mice receiving Porcn-null BMMΦ CM (Duodenum *P<6.86E−07, Jejunum **P<7.89E−08 and Ileum ***P<8.16E−08) or αMEM growth medium (Duodenum *P<7.92E−08, Jejunum **P<8.26E−07 and Ileum ***P<8.96E−09; unpaired t-test, two-tailed). (e) Histogram demonstrating villus length in duodenal, jejunal and illeul sections of Csf1r.iCre;Porcn^fl/fl mice. Irradiated Csf1r.iCre;Porcn^fl/fl mice receiving WT BMMΦ CM showed less reduction in villus length compared with mice receiving Porcn-null BMMΦ CM (Duodenum *P<3.64E−06, Jejunum **P<2.86E−06 and Ileum ***P<2.16E−05) or αMEM growth medium (Duodenum *P<4.21E−06, Jejunum **P<3.16E−08 and Ileum ***P<2.88E−05; unpaired t-test, two-tailed).