The remarkable downregulation of inflammatory genes observed in the period preceding the complete repopulation of OHCs with new neurons, in addition to the strong negative correlation between mRNA levels of inflammatory response gene Mmp9 and neurogenesis and synaptogenesis genes Neurod1 and Bdnf (Fig. 5 and Additional file 5) point towards neuroinflammation as a key negative regulator of neurogenesis during TD. Here, MMP9 is linked to thanatophoric dysplasia.