The interglobular spaces in the endochondral layer of the osseous labyrinth

Abstract

The endochondral layer of the osseous labyrinth in the rat, golden hamster, mouse, guingea pig, pig, rabbit, cat, dog and monkey was studied and compared with that of man. (1) With the exception of the mouse and golden hamster, interglobular spaces were found. (2) In all species but the rat, the interglobular spaces contain acid mucopolysaccharides. An analogy between these structures and the ‘basophilic islands’ (basophile Inseln) is discussed. (3) Extension, arrangement, direction, occurrence and frequency of interglobular spaces vary within each species so that no constant relations could be found, which are also lacking in man. Possible reasons for the persistence throughout life of interglobular spaces in the osseous labyrinth of man and some mammals are discussed.

Temporal bone marrow of the rat and its connections to the inner ear

“…Bone matrix autofluorescence intensity at 647 nm allowed delineation of the otic capsule endochondral bone characterized by an interconnected network of macrophage-rich vascular channels connected to reticular bone marrow clusters containing Iba1+ cells and megakaryocytes. The architecture of rat endochondral bone we observed fits with what was characterized in previous studies, where it was found to be very vascularized and enriched in globuli ossei rather than interglobular substance (40). Although the techniques used in these previous studies did not allow labeling of selective immune cell populations nor 3D reconstruction, and therefore bone marrow was not investigated in these studies, comparative measurements of bone properties from these studies suggest that the rat would be the optimal model to study endochondral bone marrow, since endochondral bone vascularization is much higher in rat than in most other animal models (41).…”

“…Given that endochondral and membranous bone differ in collagen I and osteocalcin expression patterns (38), and that both proteins have been observed to be autofluorescent in cleared bone (14), these intensity differences appear to correlate with endochondral bone distribution. As further support of this, around the cochlea the geometry of low-autofluorescence bone (Figures 1C,D) was similar to that of endochondral bone (39) and at high resolution osteon-like layered patterns could be seen in this region (Figure 1E), consistent with the presence of osseous globuli, which predominate in the rat endochondral bone (40). On the other hand, microCT allowed to visualize the distribution of bone marrow cavities but did not allow to observe local variations of bone matrix structure or cavity contents (Figure 1F).…”

“…The localization of megakaryocytes in cleared bone marrow has been shown in other bones to reflect the distribution of stem cells ( 46 ). In addition, lightsheet imaging allowed us to distinguish features in the decalcified bone matrix which delineated petrosal endochondral bone ( 38 , 40 ), and therefore allowed us to observe endochondral bone marrow clusters. The size and perivascular location of endochondral bone marrow lobules justifies their neglect in classical temporal bone histology: without selective labeling, most immune cells cannot be identified, the small size of marrow clusters hinders their analysis with conventional bone marrow tools, such as needle aspiration; on the other hand, since bone marrow cells are only loosely attached to each other ( 47 ), slice histology may lead to marrow cell detachment and loss, whereas tissue clearing of intact bones has been shown to give more unbiased cell density estimates ( 14 ).…”