Regional estimates of hair cells and supporting cells in the human crista ampullaris

Abstract

Regional estimates of type I and type II vestibular hair cells (HC) and supporting cell (SC) numbers were obtained from the horizontal crista ampullaris by using design-based stereology in human. Cristae were microdissected from temporal bones obtained post-mortem (N=16, age range 26-98 years). Three groups were made according to age: group 1, n=5, ages between 26 and 67 years, average age 51 years; group 2, n=4, average age 84 years; and group 3, n=7, average age 94 years. For group 1, the average total HC number was 8,005+/-214, corresponding to 4,119+/-107 type I HC, 3,886+/-117 type II HC, and 10,274+/-224 SC. The type I:type II HC ratio was 1.06+/-0.01, and HC density was 0.80 cells/100 microm2. For group 2, the average total HC number was 7,074+/-489, corresponding to 3,733+/-212 type I HC, 3,341+/-314 type II HC, and 9,321+/-858 SC. The type I:II HC ratio was 1.12+/-0.06, and HC density was 0.75 cells/100 microm2. For group 3, the average HC number was 6,009+/-327, corresponding to 3,380+/-223 type I HC, 2,628+/-235 type II HC, and 10,185+/-182 SC. The type I:II HC ratio was 1.34+/-0.10, and HC density was 0.63 cells/100 microm2. A significant decline in type I, type II, and total HC number and density was found in groups 2 and 3, with individuals exceeding the average human life span.

Histopathologic Changes of the Inner ear in Rhesus Monkeys After Intratympanic Gentamicin Injection and Vestibular Prosthesis Electrode Array Implantation

“…Methods employed in this study cannot consistently distinguish between the central and peripheral zones in the cristae or striolar and nonstriolar regions in the maculae. In normal humans, there is decreased HC density in the central zone and striolar region (Lopez et al 2005;Gopen et al 2003) and increased type I:II HC ratio in the central zone (Lopez et al 2005). Although consistent with our qualitative observations, these differences could not be quantified in the present study due to the lack of well-defined anatomic boundaries.…”

“…The mean type I:II HC ratios of 2.3 (SD 0.8) and 1.1 (SD 0.4) in the crista and macula, respectively, estimated in this study are in range of ratios of approximately 1.6-2.4 in the central zone of the crista (Rauch et al 2001;Lopez et al 2005) and 1.4-1.7 in the otolith end organ macula (Gopen et al 2003;Merchant et al 2000) in humans. Methods employed in this study cannot consistently distinguish between the central and peripheral zones in the cristae or striolar and nonstriolar regions in the maculae.…”

“…While less rigorous than the dissector stereological technique (Sterio 1984), its accuracy has been validated in multiple studies of archived human temporal bones that underwent sectioning and processing using techniques similar to those employed in this study (Merchant 1999;Richter 1980;Rauch et al 2001), and yielded results similar to more labor-intensive stereological methods (Lopez et al 2005). Moreover, although optical (Severinsen et al 2010) and physical dissector techniques (Lysakowski and Goldberg 2008) have been employed with success in other studies, pilot studies in our specimens indicated that the slice thickness we employed (10 μm) was too thin for optical sectioning and too thick for physical dissector techniques, relative to the average size of an HC (5 μm).…”

“…For instance, due to the fixed plane of sectioning, only a small fraction of a certain region is available for counting (e.g., 8 % of utricle when sectioned in the axial plane) (Merchant 1999). In fact, where unbiased stereological methods have been successfully applied to vestibular neuroepithelia, each neuroepithelium of interest was microdissected before sectioning to ensure that the sectioning plane was perpendicular throughout the region of interest to maximize yield (Ishiyama et al 2007;Lopez et al 2005;Gopen et al 2003). This was not possible in the present study, as it would have led to the destruction of anatomical areas of interest relevant to MVP implantation.…”

“…Total HC surface density in the cristae and maculae has been shown to decrease with increasing body size, being approximately 120-200/0.01 mm 2 in chinchillas (Fernandez et al 1995;Desai et al 2005a;Desai et al 2005b), 100-130/0.01 mm 2 in squirrel monkeys (Fernandez et al 1995), and 60-80/0.01 mm 2 in humans (Richter 1980;Lopez et al 2005). Although normative data have not been published for the rhesus monkey, the mean total HC estimate of 79/ 0.01 mm 2 (SD 3.0/0.01 mm 2 ) we measured for cristae and maculae of normal rhesus ears in this study is consistent with this trend when compared to human and small animal data obtained using unbiased stereology.…”