| Abstrakt: |
Using tissue clearing and immunofluorescence, we have recently characterized the adult rat temporal bone marrow distribution, and in particular the distribution and connections to the inner ear of petrosal bone marrow (doi: 10.3389/ fneur.2024.1386654). Bone marrow was identified by its high cellular content and by the presence of cell populations belonging to the hemopoietic niche (e.g. megakaryocytes, see companion abstract from our group). In the cleared rat pet-rosal bone, autofluorescence allowed delineation of the otic capsule. The largest marrow island was found outside of the otic capsule, surrounding semicircular canal arms, and connecting to the dura through bone channels similar to those of calvarial bone, with only a few channels directed towards the bony labyrinth. Unexpectedly, bone marrow was also observed within the otic capsule endochondral layer, forming small clusters associated to the vestibule (VEM) and cochlear apex (CAEM). Endochondral bone marrow was connected through vascular loops to the labyrinth, and through straight channels to dural sinuses. The latter also received vascular connection from marrow located in surrounding bones, suggesting a role as immune barrier restricting pathogen spread from ear to brain. In mouse, petrosal bone marrow distribution was overall similar to the rat but displayed a few differences. The most evident difference was the volume ratio of CAEM over total petrosal bone marrow (23 ± 1% in mouse, n = 2; 2 ± 1% in rat, n = 8; p < 10E-8). Moreover, CAEM and VEM were connected by vascular bridges in mouse but not in rat. Given the importance of local bone marrow in the immune reactions of brain (doi: 10.1111/imr.13120) and middle ear (doi: 10.3389/fgene.2022.985214), this difference in CAEM volume and connectivity calls for attention in choosing a model for human inner ear immune reactions. [ABSTRACT FROM AUTHOR] |
