Proteins and bioprosthetic calcification in the rat model.
OBJECTIVE
The mechanism of valvular bioprostheses calcification is still unknown, but early studies showed increased Gla-protein content in calcified valves. Using an experimental model, which reproduces the clinical process, we therefore analyzed the role of minerals and proteins in bioprosthetic valvular calcification.


METHODS
Glutaraldehyde pretreated porcine valves were studied before and after implantation in rats by X-ray, calcium (Ca) and phosphorus (P) measurement, Fourier Transform Infrared (FTIR) spectroscopy, SDS-PAGE and 45Ca ligand blotting of the extracted proteins.


RESULTS
Before implantation, there was no X-ray calcification with very little Ca and P content. After implantation, X-ray calcifications appeared on day seven with increased Ca and P up to day 35 (p < 0.05, ANOVA). FTIR revealed structural proteins alone before implantation, plus minor proportions of lipids on day two, which always preceded Ca and P appearance. Ca and P increased up to day 35, first as amorphous and changed in carbapatite over time. SDS-PAGE before implantation revealed two proteins (66-kD and 54-kD) alone, which were sustained up to day 35. The 66-kD had 45Ca affinity. On day two, many other proteins appeared on SDS-PAGE, four of which (52, 45, 14 and below 14-kD) with 45Ca affinity. Protein pattern did not change from day two to 35.


CONCLUSIONS
Valvular bioprosthesis calcification is associated with progressive increase in Ca and P content and at least five calcium-binding proteins: one intrinsic valvular protein, pre-existing to implantation, plus four other, extrinsic valvular proteins adsorbed within the tissue after implantation.
Shen
M
M
Hospital Broussais, Paris, France.
Farge
D
D
Daudon
M
M
Carpentier
S
S
Pellerin
M
M
Lacour
B
B
Chen
L
L
Martinet
B
B
Carpentier
A
A
D000818:Animals; D001705:Bioprosthesis; D002114:Calcinosis / Q000473:pathology*; D002118:Calcium / Q000032:analysis; D002135:Calcium-Binding Proteins / Q000032:analysis*; D005260:Female; D006350:Heart Valve Prosthesis; D008297:Male; D010758:Phosphorus / Q000032:analysis; D011475:Prosthesis Failure; D051381:Rats; D017208:Rats, Wistar; D013499:Surface Properties
D002135:Calcium-Binding Proteins; D010758:Phosphorus; D002118:Calcium