Distribution of bone marrow-derived cells in the vestibular end organs and the endolymphatic sac

Abstract

Conclusion: Bone marrow-derived cells (BMDCs) are constitutively present in the vestibular end organs and in the endolymphatic sac, and may play a role in the maintenance of inner ear homeostasis. Objectives: The aim was to examine the distribution and characteristics of BMDCs in the vestibular end organs and in the endolymphatic sac. Methods: Bone marrow-chimeric mice were generated by bone marrow transplantation from mice genetically labeled with enhanced green fluorescent protein to C57 Bl/6 mice to visualize BMDCs. Three months after bone marrow transplantation, inner ear specimens were processed for histochemical analyses. Results: BMDCs were widely distributed in the vestibular end organs and the endolymphatic sac, whereas there were differences in the phenotype and the distribution between the vestibular end organs and the endolymphatic sac. A subpopulation of BMDCs in the vestibular end organs expressed antigen-presenting protein MHC class II. Moreover, the density of BMDCs in the vestibular end organs increased in response to local mechanical stress.

Keywords::

• Hematopoietic stem cell
• transplantation
• immune response
• macrophage

Acknowledgments

This study was supported by a grant from the Ministry of Education, Culture, Sports, Science and Technology of Japan. The authors thank Dr Masaru Okabe (Osaka University, Osaka, Japan) for generously providing EGFP transgenic mice, and Dr Tomoko Kita (Center for Developmental Biology, RIKEN, Kobe, Japan) for critical discussions.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.