Transport of membrane-bound mineral particles in blood vessels during chicken embryonic bone development.
During bone formation in embryos, large amounts of calcium and phosphate are taken up and transported to the site where solid mineral is first deposited. The initial mineral forms in vesicles inside osteoblasts and is deposited as a highly disordered calcium phosphate phase. The mineral is then translocated to the extracellular space where it penetrates the collagen matrix and crystallizes. To date little is known about the transport mechanisms of calcium and phosphate in the vascular system, especially when high transport rates are needed and the concentrations of these ions in the blood serum may exceed the solubility product of the mineral phase. Here we used a rapidly growing biological model, the chick embryo, to study the bone mineralization pathway taking advantage of the fact that large amounts of bone mineral constituents are transported. Cryo scanning electron microscopy together with cryo energy dispersive X-ray spectroscopy and focused-ion beam imaging in the serial surface view mode surprisingly reveal the presence of abundant vesicles containing small mineral particles in the lumen of the blood vessels. Morphologically similar vesicles are also found in the cells associated with bone formation. This observation directly implicates the vascular system in solid mineral distribution, as opposed to the transport of ions in solution. Mineral particle transport inside vesicles implies that far larger amounts of the bone mineral constituents can be transported through the vasculature, without the danger of ectopic precipitation. This introduces a new stage into the bone mineral formation pathway, with the first mineral being formed far from the bone itself.
Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel. Electronic address: kerschnitzki@gmail.com.
Michael
M
Kerschnitzki
Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel.
Anat
A
Akiva
Department of Molecular Genetics, Weizmann Institute of Science, 76100 Rehovot, Israel.
Adi Ben
AB
Shoham
Department of Chemical Engineering and the Russell Berrie Nanotechnology Institute (RBNI), Technion-Israel Institute of Technology, Haifa 32000, Israel.
Naama
N
Koifman
Department of Chemical Research Support, Weizmann Institute of Science, 76100 Rehovot, Israel.
Eyal
E
Shimoni
Department of Chemical Research Support, Weizmann Institute of Science, 76100 Rehovot, Israel.
Katya
K
Rechav
Department of Genetics and Developmental Biology, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, 32000, Haifa, Israel.
Alaa A
AA
Arraf
Department of Genetics and Developmental Biology, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, 32000, Haifa, Israel.
Thomas M
TM
Schultheiss
Department of Chemical Engineering and the Russell Berrie Nanotechnology Institute (RBNI), Technion-Israel Institute of Technology, Haifa 32000, Israel.
Yeshayahu
Y
Talmon
Department of Molecular Genetics, Weizmann Institute of Science, 76100 Rehovot, Israel.
Elazar
E
Zelzer
Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel.
Stephen
S
Weiner
Department of Structural Biology, Weizmann Institute of Science, 76100 Rehovot, Israel.
Lia
L
Addadi
D000818:Animals; D001692:Biological Transport; D001808:Blood Vessels / Q000196:embryology* / Q000378:metabolism* / Q000648:ultrastructure; D001846:Bone Development; D002118:Calcium / Q000378:metabolism; D002642:Chick Embryo; D005269:Femur / Q000196:embryology; D021621:Imaging, Three-Dimensional; D008566:Membranes / Q000378:metabolism; D008903:Minerals / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism
D008903:Minerals; D010758:Phosphorus; D002118:Calcium
3D FIB; Avian embryo; Biomineralization; Calcium phosphate; Cryo-electron microscopy