ECTS2016 Poster Presentations Bone development/growth and fracture repair (35 abstracts)
Role of PHOSPHO1 in chondrocyte matrix vesicle mineralization: an AFM study
Massimo Bottini 1, , Manisha Yadav 2 , Kunal Bhattacharya 3 , Andrea Magrini 1 , Nicola Rosato 1 , Bengt Fadeel 3 , Colin Farquharson 4 & José Luis Millán 2
1University of Rome Tor Vergata, Rome, Italy; 2Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA; 3Karolinska Institutet, Stockholm, Sweden; 4The University of Edinburgh, Easter Bush, Roslin, Midlothian, UK.
We used atomic force microscopy (AFM) to study the morphology and development of mineralization-competent matrix vesicles (MVs) secreted by chondrocytes isolated from WT and Phospho1−/− mice in order to validate the role of PHOSPHO1 in MV mineralization. All MVs appeared as flattened globular features either individually dispersed or connected to a mat-like structure. The mat-like structure very closely resembled type-X collagen that has been described by others. WT MVs were in greater number than Phospho1−/− MVs and showed volumes ranging from few to hundreds of thousands of cubic nanometers. Phospho1−/− MVs showed volumes in a smaller range of values. AFM topographic and phase analyses showed that WT MVs with volumes smaller than ~5×103 nm3 had a smooth surface and phase angle (ϕ) values that were almost constant and slightly smaller than those of mica substrate. On the contrary, bigger WT MVs showed a non-uniform surface with several angstrom tall irregularities and a great heterogeneity of ϕ values with spots that had ϕ values similar to those of mica substrate and were surrounded by regions with negative ϕ values. These spots corresponded to height irregularities in topographic images and their ϕ values increased with MV volume. We interpreted these spots as caused by the presence of the nucleational core (NC) under the MVs’ membrane. Phospho1−/− MV surface was smooth for all vesicles and showed small irregularities only for bigger vesicles. Phospho1−/− MV ϕ values were constant, slightly bigger than those of mica substrate and increasing with MV volume, thus suggesting the absence of a NC in most of these MVs. Raman spectroscopy validated the differences between the material inside WT and Phospho1−/− MVs. Taken together our data document the decreased ability of Phospho1−/− MVs to initiate mineralization.
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Bone Abstracts
ISSN 2052-1219 (online)
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