FIGURE 7.

Protective effects of mesenchymal stromal cell‐derived extracellular vesicles (MSC‐EVs) in a mouse noise trauma model in vivo. A, Mean auditory brainstem response (ABR) thresholds (in dB) are plotted for the different frequencies (4, 8, 16, 32 kHz) and designated as pre‐noise (grey) or post‐noise values (black, 4 weeks after noise trauma). Treatment with MSC‐EVs on day 3 post‐noise (n = 5) attenuates threshold shifts after noise trauma when compared to the control (artificial perilymph, n = 5) treated animals, especially in the higher frequencies. Pre‐noise ABR thresholds of all animals tested are comparable and at physiological levels. Data are presented as mean ± standard deviation; ***P ˂ .001, n.s., not significant. B, Representative images after immunohistochemical staining for myosin VIIa are shown. A normal organ of Corti (no noise trauma, no treatment, displays intact inner and outer hair cells (IHC and OHC), while noise trauma and treatment with control (artificial perilymph) results in intact inner but damaged outer hair cells. Post‐noise treatment with EVs from umbilical cord (UC)‐derived MSCs rescues the organ of Corti with intact inner and outer hair cells. Scale bar: 50 μm applies to all images shown