Quantitative imaging of proteoglycan in cartilage using a gadolinium probe and microCT.
OBJECTIVE
Micro-computed tomography (microCT) imaging has the potential to allow the three-dimensional (3D) visualization of cartilage morphology. However, cartilage intensity on a microCT image is weak because cartilage does not strongly attenuate X-rays. This work was designed to demonstrate that exposure of cartilage to charged gadolinium compounds modifies the intensity to allow an improved visualization of cartilage morphology and the determination of proteoglycan content.


METHODS
Trypsin was used to deplete proteoglycan in bovine nasal cartilage disks. Disks were then exposed to Gd(3+), gadopentetate (Gd-DTPA(2-)), or gadoteridol (Gd-HP-DO3A), and imaged with microCT. The intensities of the disks were measured from the images and compared to the actual proteoglycan content determined with a dimethylmethylene blue assay.


RESULTS
Treatment of naïve disks with 200 mM Gd(3+) for 24h at room temperature produced a 2.8-fold increase in intensity on microCT images. Similar treatment with 200 mM Gd-DTPA(2-) produced a 1.4-fold increase. After 2h of trypsin treatment at room temperature, the intensities of cartilage disks exposed to 20 0mM Gd(3+) decreased by 12%. Conversely, the intensities of trypsin-treated disks exposed to 200 mM Gd-DPTA(2-) increased by 15%. Trypsin treatment caused a 4% increase in the intensities of disks exposed to neutral Gd-HP-DO3A. The correlation between proteoglycan content and the microCT intensity of cartilage treated with Gd(3+) was very good (r(2)=0.81).


CONCLUSIONS
Gadolinium and microCT allow an improved 3D visualization of cartilage and quantification of its proteoglycan content.
Cockman
M D
MD
Procter and Gamble Pharmaceuticals, 8700 Mason-Montgomery Road, Mason, OH 45040, USA. cockman_michael_dane@lilly.com
Blanton
C A
CA
Chmielewski
P A
PA
Dong
L
L
Dufresne
T E
TE
Hookfin
E B
EB
Karb
M J
MJ
Liu
S
S
Wehmeyer
K R
KR
D000818:Animals; D002356:Cartilage / Q000737:chemistry* / Q000000981:diagnostic imaging; D002417:Cattle; D003287:Contrast Media; D005682:Gadolinium; D019786:Gadolinium DTPA; D006571:Heterocyclic Compounds; D021621:Imaging, Three-Dimensional / Q000379:methods; D009300:Nasal Septum / Q000737:chemistry / Q000000981:diagnostic imaging; D009942:Organometallic Compounds; D011509:Proteoglycans / Q000032:analysis*; D014057:Tomography, X-Ray Computed / Q000379:methods
D003287:Contrast Media; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D011509:Proteoglycans; C062402:gadoteridol; D005682:Gadolinium; D019786:Gadolinium DTPA