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Akiva et al. In vivo studies of mineral deposition in zebrafish Tail Fins

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DOI:10.1038/bonekey.2016.32

In order to learn more about the process by which ions from the environment are sequestered, concentrated and deposited in the extracellular matrix during bone mineralization, Akiva et al. devised a series of in vivo imaging studies using zebrafish larvae. Mineral deposition in the developing caudal fin was followed using cryo-SEM-microscopy and fluorescent calcein, combined with Raman and XRF spectroscopy.

Calcium-rich particles inside cells were detected close to developing bones and within the intra-ray region, which is further away from mineralized bone; in both cases the mineralized particles were very closely associated with vasculature.

The authors suggest that their observations challenge the view that most mineral deposition during bone formation takes place in osteoblasts in close juxtaposition with bone, or in the extracellular matrix. They propose that other cells are involved and deposits are made in an initial, disordered phase, before being transported to the extracellular bone matrix.

Editor’s comment: It is important to keep in mind that development, metabolism and regeneration capacity of dermal skeletal elements, such as fin rays, is different from endoskeletal structures. Since the postcranial dermal skeleton largely disappeared in mammals, these observations in ZF might not be directly applicable to humans.

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