File:Inner ear pathology in MPS IIIB mice at 30 wks.png

English: A. Radial view of cochlear upper basal turn showing grossly normal features. B. Crista ampullaris of lateral semicircular canal in the same animal shows abnormal lysosomal storage in both hair cells and supporting cells of the sensory epithelium (black arrow), and in dark cells (white arrow). C. Expanded view of medial organ of Corti in A. The only cells showing storage are inner pillar cells (IP) (black arrow). Mesothelial cells lining the basilar membrane (BM) show the aberrant storage (white arrowheads), as do adherent inflammatory cells (black arrowheads). Vacuoles within inner hair cells (asterisk, IHC) are probably a processing artifact. D. Spiral ganglion cell region from A shows aberrant storage only in glial cells (white arrowheads). E. Spiral ligament and lateral organ of Corti from A shows aberrant storage in outer sulcus cells (white arrowhead, OSC), epithelial cells of spiral prominence (black arrowhead, SP), Type III fibrocytes (white arrows, T3), and Type II fibrocytes (black arrows, T2). Type IV fibrocytes (T4) also showed storage, not apparent in this view. F. Complete loss of hair cells and other differentiated cell types of the organ of Corti (black arrow), with secondary loss of neuronal processes (white arrow). This was more prevalent in MPS IIIB mice than in WTs. G. Plot of the number of hair cell profiles versus neuronal density, as seen in radial view in the lower base for 5 MPS IIIB and 5 WT mice at 30 wks. Differences in hair cell numbers by genotype are highly significant (t-test, p<.001). Because inner hair cells were less affected than outer hair cells, only numbers <1.0 indicate loss of IHCs. Neuronal density decreases only when IHCs are missing, so that neuronal loss appears secondary to hair cell loss in MPS IIIB. StV: Stria vascularis; RM: Reissner's membrane; TM: Tectorial membrane; OHC: Outer hair cells; DC: Deiters' cells; OP: Outer pillar cell; Lim: Spiral limbus.