Functional bone histology of zebrafish reveals two types of endochondral ossification, different types of osteoblast clusters and a new bone type

Abstract

The zebrafish is as an important vertebrate animal model system for studying developmental processes, gene functions and signalling pathways. It is also used as a model system for the understanding of human developmental diseases including those related to the skeleton. However, surprisingly little is known about normal zebrafish skeletogenesis and osteogenesis. As in most vertebrates, it is commonly known that the bones of adult zebrafish are cellular unlike that of some other teleosts. After careful histological analyses of each zebrafish adult bone, we identified several acellular bones, with no entrapped osteocytes in addition to several cellular bones. We show that both cellular and acellular bones can even occur within the same skeletal element and transitions between these two cell types can be found. Furthermore, we describe two types of osteoblast clusters during skeletogenesis and two different types of endochondral ossification. The epiphyseal plate, for example, lacks a zone of calcification and a degradation zone with osteoblasts. A new bone type that we term tubular bone was also identified. This bone is completely filled with adipose tissue, unlike spongy bones. This study provides important insight on how osteogenesis takes place in zebrafish, and especially on the transition from cellular to acellular bones. Overall, this study leads to a deeper understanding of the functional histological composition of adult zebrafish bones.

Immune Suppressive and Bone Inhibitory Effects of Prednisolone in Growing and Regenerating Zebrafish Tissues

“…However, much of the zebrafish skeleton is composed of rigid and dense bones that are also referred to as compact bones. In addition, trabecular bone can be found in the zebrafish skull . Importantly, zebrafish osteoblasts undergo a differentiation cascade very similar to mammalian osteoblasts, both during intramembranous and perichondral and endochondral ossification .…”

Rmrp Mutation Disrupts Chondrogenesis and Bone Ossification in Zebrafish Model of Cartilage-Hair Hypoplasia via Enhanced Wnt/β-Catenin Signaling

“…Zebrafish have no limbs and long bones; however, the craniofacial bones of zebrafish are formed through endochondral ossification and intramembranous ossification as they are in humans . The ceratohyal bones are formed by endochondral ossification similar to that of mammalian bones, which also have the same composition of epiphysis and epiphysial growth plates . Previous studies have shown that the mutation of genes that cause chondrodysplasia in humans can lead to chondrodysplasia of craniofacial bone, such as the ceratohyal cartilage in zebrafish .…”

“…(20) The ceratohyal bones are formed by endochondral ossification similar to that of mammalian bones, which also have the same composition of epiphysis and epiphysial growth plates. (44) Previous studies have shown that the mutation of genes that cause chondrodysplasia in humans can lead to chondrodysplasia of craniofacial bone, such as the ceratohyal cartilage in zebrafish. (45) Thus, we investigated craniofacial development and found a pharyngeal arch cartilage development defect in rmrp mutants.…”

Anatomical Assessment of the Adult Skeleton of Zebrafish Reared Under Different Thyroid Hormone Profiles

“…Bone names as well as size (SL) at which each bone ossified were based on Cubbage and Mabee, 1996;Bird and Mabee, 2003. Craniofacial bones were sorted based on whether they were cellular, compact, spongy, and/or tubular (based on Weigele and Franz-Odendaal, 2016).…”