Abstract
BackgroundPrevious reports showed the presence of limited numbers of stem cells in neonatal murine cochlear sensory epithelia and these cells are progressively lost during the postnatal development. The goal of this study was to investigate whether stem cells can be derived from mature mouse cochleae under suspension culture conditions, and to analyze the expression of the stem cell and inner ear progenitor cell markers in cells dissociated from neonatal and adult mouse organs of Corti.MethodsOrgans of Corti were dissected from postnatal day 1 (P1) or postnatal day 60 (P60) mouse. The dissociated cells were cultivated under suspension cultures conditions. Reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemistry were conducted for phenotype characterization.ResultsThe number of cochlear stem cells (otospheres) yielded from P1 organ of Corti was significantly higher than that of the P60 organ of Corti. RT-PCR analyses showed that the stem markers, such as nanog, sox2, klf4, and nestin can be found to be distributed similarly in the cells derived from both of organisms, but the inner ear developmental/progenitor cell markers showed lower expression in P60 organ of Corti compared to P1. Immunocytochemistry results also revealed the evidence that P60 otospheres lacking of differentiation potential in vitro, which opposed to the strong differentiation potential of otospheres at P1 stage.ConclusionsOur findings suggest that the loss of numbers and features of stem cells in the adult organ of Corti is associated with the substantial down-regulation of inner ear progenitor key-markers during maturation of the cells in organ of Corti.
Highlights
Previous reports showed the presence of limited numbers of stem cells in neonatal murine cochlear sensory epithelia and these cells are progressively lost during the postnatal development
It is well known that the adult mammalian cochleae lack regenerative ability and the irreversible degeneration of cochlear sensory hair cells leads to permanent hearing loss [14], but little is known about the genes and pathways that are potentially involved in this difference of the regenerative/repair potentialities between early postnatal and adult mammalian cochlear sensory epithelia (SE) [14]
The aims of this study are: 1) To investigate whether some remnants of regenerative ability of quiescent progenitor/stem cells can be isolated from mature cochlea, we compare the sphere-forming capabilities of cultured cells derived from postnatal day 1 (P1) and postnatal day 60 (P60) SE; 2) To explore changes of genes and pathways underlying the stem/ progenitor cells maintenance and the capacity of regeneration/repair between P1 and P60 SE-derived cells
Summary
Previous reports showed the presence of limited numbers of stem cells in neonatal murine cochlear sensory epithelia and these cells are progressively lost during the postnatal development. While previous studies demonstrate that early postnatal cochlea harbors stem/progenitor-like cells and show a limited regenerative/repair capacity [3,4,5,6,7,8,9,10,11,12,13], and these properties, are progressively lost later during the postnatal development of the inner ear [5]. The aims of this study are: 1) To investigate whether some remnants of regenerative ability of quiescent progenitor/stem cells can be isolated from mature cochlea, we compare the sphere-forming capabilities of cultured cells derived from P1 and P60 SE; 2) To explore changes of genes and pathways underlying the stem/ progenitor cells maintenance and the capacity of regeneration/repair between P1 and P60 SE-derived cells. We investigate whether these cells can be differentiated into hair cells and supporting cells in vitro using immunocytochemistry
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