Cellular morphology and markers of cartilage and bone in the marine teleost Sparus auratus

Abstract

Modifications have been characterised in terms of cellular organisation and the extracellular matrix (ECM) during bone ontogeny in the sea bream (Sparus auratus). During endochondral development, the agglomeration of matrix-secreting cells gives rise to chondrones; these chondrones frequently contain proliferating-cell-nuclear-antigen-positive cells, which subsequently become large collagen-II-positive cells with the characteristics of chondrocytes. Moreover, the matrix:cell ratio within the perichondrium increases, accompanied by a modification in ECM composition. Mineralisation of cartilage ECM is marked by a rapid fall in cell number, the switching off of collagen II transcription and the switching on of collagen X transcription, followed by collagen I transcription and bone mineralisation. The formation of dermal structures initiated upon the condensation of mesenchyme cells defines the future location of the dermal bone. Subsequent cellular differentiation gives rise to cells on the bone surface; these cells are positive for collagen I and osteonectin transcripts. The fish skeleton, with the exception of vertebrae, tends to comprise flattened bones that are covered by a monolayer of cells, the periosteum. A third type of tissue, present in gills, consists of chondrocyte-like cells embedded in a mineralised matrix resembling chondroid bone in mammals. The results suggest that the cellular organisation and ontogeny of endochondral and dermal bone in the sea bream are similar to those described in other vertebrates.

Environmental Conditioning of Skeletal Anomalies Typology and Frequency in Gilthead Seabream (Sparus aurata L., 1758) Juveniles

“…2 [81] reports that dentary ossifies endochondrally but being the only reference affirming this, this bone has been inserted among the intramembranously ossifying elements.…”

“…1hypurals are reported to ossify endochondrally in zebrafish ( Danio rerio ) [78]–[80], in Senegalese sole ( Solea senegalensis ) [80], in gilthead seabream [81] but other authors found that ossification is perichondral in Nile tilapia and desert pupfish [82];…”

“…At least three ossification processes have been described in fish skeletal tissues: intramembranous ossification , in which the type of bone (dermal bone) is not preformed into a cartilage, but all these dermal skeleton elements form in the mesenchyme or in the dermis, below a multilayered epithelium or epidermis (majority of exoskeleton); endochondral ossification , where a cartilaginous scaffold is replaced by bone (majority of the endoskeleton); perichondral ossification , where a cartilaginous precursor is present and usually starts with the transformation of a perichondrium into a periosteum. A few problems were encountered in attempting to correctly assign each bone to the corresponding ossification modality in gilthead seabream owing the presence in literature of many contradictory data: i.e., hypurals are reported to ossify endochondrally in zebrafish ( Danio rerio ) [78]–[80] and, in Senegalese sole ( Solea senegalensis ) [80] and in gilthead seabream [81], whilst other authors [82] described hypural perichondral ossification in Nile tilapia ( Oreochromis niloticus ) and desert pupfish ( Cyprinodon macularis ). Even dentary and opercular series bones are widely reported as intramembranously ossifying in fish (all originating from the neural crest) [83], whilst [81] reported that in gilthead seabream they ossify endochondrally.…”

MiR-29a is an enhancer of mineral deposition in bone-derived systems

“…SPARC has a key role in ECM assembly and deposition due to its binding to a number of different ECM components [53]. Controlled expression of this protein seems to be essential for normal osteoblastic differentiation and skeletogenesis in mammals [54][55][56] and fish [57][58][59]. In that sense, SPARC was shown to display several conserved features throughout evolution, mainly related to its protein structure, function and regulation [59].…”

Divergent responsiveness of the dentary and vertebral bone to a selective estrogen-receptor modulator (SERM) in the teleost Sparus auratus

“…Nevertheless, there is overall conservation of tissue organisation in vertebrates and the extracellular matrix (ECM) in teleosts contains homologues of mammalian ECM proteins, both collagenous and non-collagenous, such as osteonectin (OSN) and osteocalcin [8,17,29]. At the cellular level osteoblasts (bone forming cells) and osteoclasts (bone resorbing cells) are present in the bone of advanced teleosts but in contrast to osteocyte-containing mammalian bone, it is acellular, with a few notable exceptions eg.…”