Skull diploë is rich in aquaporin-4

Yuji Suzuki; Hiroki Kitaura; Yukimi Nakamura; Akiyoshi Kakita; Vincent J Huber; Nicholas Capozzoli; Ingrid L Kwee; Tsutomu Nakada

doi:10.1016/j.heliyon.2020.e03259

Skull diploë is rich in aquaporin-4

Heliyon. 2020 Jan 30;6(1):e03259. doi: 10.1016/j.heliyon.2020.e03259. eCollection 2020 Jan.

Authors

Yuji Suzuki¹, Hiroki Kitaura^{1

2}, Yukimi Nakamura¹, Akiyoshi Kakita², Vincent J Huber¹, Nicholas Capozzoli³, Ingrid L Kwee^{1

4}, Tsutomu Nakada^{1

4}

Affiliations

¹ Center for Integrated Human Brain Science, Brain Research Institute, University of Niigata, Japan.
² Department of Pathology, Brain Research Institute, University of Niigata, Japan.
³ Neurology Service, VA Northern California Health Care System, USA.
⁴ Department of Neurology, University of California, Davis, USA.

Abstract

Aquaporin-4 (AQP4) is a water conducting membrane integral protein channel which is widely expressed in the astrocyte system of the brain. During the development of the AQP4 positron emission tomography (PET) imaging agent [¹¹C]TGN-020 (N-(1,3,4-thiadiazol-2-yl)pyridine-3-[¹¹C]-carboxamide), significant radioligand uptake was observed in the skull, where there was no known distribution of any aquaporin family proteins. Herein we confirmed via a newly developed method for bone-tissue immunohistology, a hitherto unrecognized distribution of AQP4, and not AQP1, in the skull. Other bony structures, by contrast, showed virtually no uptake of [¹¹C]TGN-020, and likewise, do not express either AQP4 or AQP1. Immunohistological analysis demonstrated that the AQP4 expression in the skull is restricted to the diploë. Consequently, we suspect AQP4 plays a pivotal role in the formation and maintenance of yellow marrow and the diploë. However, elucidating the exact nature of that role will require further studies.

Keywords: Anatomy; Aquaporin 4 (AQP4); Bone; Immunohistology; Medical imaging; N-(1,3,4-thiadiazol-2-yl) pyridine-3-[11C]-carboxamide ([11C]TGN-020); Nuclear medicine; Pathology; Positron emission tomography(PET); Radiology; Skull; Tissue culture.