(A) Merged bright-field and fluorescence imaging of multinucleated FBGCs in WT or Trpv4−/− BMDMs plated on PA gels of different stiffness and treated with the fusogenic cytokines IL-4 and GM-CSF. Cell nuclei were stained with DAPI. (B and C) Quantification of the number of FBGCs/high-power field (hpf) (B) and the percentage of BMDMs involved in fusion events (C). Scale bar, 20 μm. n = 3 biological replicates and 5 images per group. **P < 0.01 and ***P < 0.001, Student’s t test. (D) Representative immunofluorescence images showing α-SMA, phalloidin, and nuclei in WT mouse dermal fibroblasts after 48 hours of stimulation with CM collected from WT or Trpv4−/− BMDMs plated on collagen-coated PA gels of 1- or 50-kPa stiffness. Scale bar, 20 μm. (E) Quantification of myofibroblast differentiation from the experiment shown in (D). n = 3 independent experiments and 10 cells per condition. **P < 0.01 and ***P < 0.001, Student’s t test. Ut, untreated. A.U., arbitrary units.