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PubMedDate not supplied

Origin of cartilage laminae in MRI.

To understand the origin of the laminated appearance of cartilage in MRI (the magic angle effect), microscopic MRI (mu MRI) experiments were performed at 14-microns pixel resolution on normal canine articular cartilage from the shoulder joints. Two-dimensional images of the spin-spin relaxation time (T2) of the cartilage-bone plug at two angles (0 degree and 55 degrees) were calculated quantitatively. A distinct T2 anisotropy was observed as a function of the cartilage tissue depth. The surface and the deep regions exhibit strong orientational dependence of T2, whereas the upper-middle region exhibits little orientational dependence of T2. These three mu MRI regions correspond approximately to the three histologic zones in cartilage tissue. The results from the bulk T2 measurements agreed with these mu MRI results. Our studies show that the laminated appearance of cartilage in MRI is caused by T2 anisotropy of the tissue. We further suggest that the molecular origin of the T2 anisotropy is the nuclear dipolar interaction. The structure of the cartilage tissue indicates that the collagen meshwork defines this T2 anisotropy. The results show that the T2 anisotropy provides an indirect but sensitive indicator for the orientation of macromolecular structures in cartilage. The clinical implications of this anisotropy are discussed.

Animals↗
PubMed2006

Comparison of quantitative cartilage measurements acquired on two 3.0T MRI systems from different manufacturers.

PURPOSE: To investigate the comparability of two osteoarthritis (OA) surrogate endpoints--average cartilage thickness and cartilage volume--acquired from healthy volunteers on two 3.0T magnetic resonance imaging (MRI) systems from different manufacturers. MATERIALS AND METHODS: Ten knees of five healthy volunteers were scanned on a 3.0T General Electric (GE) and a 3.0T Philips scanner using a fast three-dimensional fat-suppressed spoiled gradient (SPGR) imaging sequence. The acquisition parameters were optimized beforehand and were kept as comparable as possible on both scanners. For quantitative analysis, the average cartilage thickness and volume of the load-bearing regions of the femoral condyles were compared. Data were analyzed using a univariate repeated-measures analysis of variance (ANOVA) to examine the effects of position, condyle, and imaging system on the measurements. RESULTS: The average cartilage thickness and volume of the load-bearing regions of the femoral condyles did not differ between the two different 3.0T MRI systems (P > 0.05). There was no significant effect of position or condyle on the average cartilage thickness measurements (P > 0.05; range = 0.41-0.93) or cartilage volume (P > 0.05; range = 0.14-0.87). CONCLUSION: Two OA surrogate endpoints--average cartilage thickness and cartilage volume--acquired on two 3.0T MRI systems from different manufacturers are comparable.

Adult↗
PubMed1983

Synovial factors and chondrocyte-mediated breakdown of cartilage: inhibition by hydrocortisone.

Cartilage-synovium interactions were explored in a model culture system. Bovine nasal-cartilage discs were cocultured with minced rheumatoid synovium or synovium-conditioned media (SCM) in the presence or absence of hydrocortisone. Cartilage breakdown was assessed by the release of proteoglycan (PG) and hydroxyproline, and matrix biosynthesis by [35S]sulfate incorporation during pulse labeling. Chondrocyte-dependent breakdown in response to synovial factors (i.e., "catabolin" activity) was assessed by the difference in PG release between living and dead cartilages. Short-term contact with minced synovial membrane or exposure to its products released at a distance was sufficient to induce cartilage degradation in coculture; continued exposure was not required for breakdown to persist. Conditioned media from short-term synovial culture were similarly potent, and the induced breakdown was chondrocyte dependent. Matrix biosynthesis was inhibited in exposed cartilage but could be rapidly restored to normal on synovium removal despite the persistence of cartilage breakdown. Early hydrocortisone treatment suppressed the initiation of cartilage breakdown in cocultures and largely abolished the appearance of inductive factors in SCM. Later applications had little effect either in cocultures or in catabolin assays. We conclude that synovium-induced breakdown is an early event and that chondrocyte catabolic mechanisms once they have been activated are sufficient to maintain breakdown at a high level. Hydrocortisone, as well as limiting proteolysis, inhibits early tissue interactions at the level of synovial catabolin production or release.

Animals↗
PubMed1985

Structure of newly synthesised (35S)-proteoglycans and (35S)-proteoglycan turnover products of cartilage explant cultures from dogs with experimental osteoarthritis.

The structure of newly synthesised proteoglycans from explant cultures of cartilage from joints subjected to transection of the anterior cruciate ligament (osteoarthritic) and from normal (non- or sham-operated) joints was examined. The structure of the products of proteoglycan turnover was also examined using explants of normal and osteoarthritic cartilage maintained in culture for a 48 h chase period. The findings were as follows: Newly synthesised (35S)-proteoglycans extracted from cartilage explants from osteoarthritic joints whether examined 3 weeks, 3 months, or 6 months after surgery were larger than those from corresponding normal cartilage. This can be explained by the synthesis in osteoarthritic cartilage of abnormally long chondroitin sulphate chains on newly synthesised proteoglycans. The extracts also contained a newly formed small proteoglycan species that was unable to interact with hyaluronic acid. The proportion of this species was higher in osteoarthritic cartilage compared with normal, examined 3 weeks after surgery, but was generally absent from cartilage obtained 3 and 6 months after surgery. Compared with controls, a smaller proportion of the (35S)-proteoglycans released into the maintenance medium of explant cultures of osteoarthritic cartilage during a 48 h chase period was able to interact with hyaluronic acid. However, although furnished with longer (35S)-glycosaminoglycan chains, these proteoglycans were smaller than those from control explants.

Animals↗
PubMed1988

Effect of purified human interleukin-1 on cartilage degradation.

The effects of highly purified human monocyte-derived interleukin-1 (IL-1) on bovine nasal cartilage breakdown were investigated. Cartilage degradation was determined by quantifying the fraction of total proteoglycan released from cartilage during 8 days of culture. The response appeared to be chondrocyte-dependent, for IL-1 stimulated proteoglycan (PG) release from living but not from dead (frozen-thawed) cartilage. IL-1 action on living cartilage was heat labile and concentration dependent, with significant effect at 5 U/ml and maximal effect at 10-20 U/ml. Kinetic studies showed significant stimulation of PG release by 3 days of incubation with 10 U/ml IL-1. Studies in which IL-1 was removed on day 1 or day 4 showed that the cartilage-degrading effect of this monokine was reversible. Although IL-1 caused little change in the Sepharose CL-2B chromatographic profile of released PGs using an associative elution buffer, a significant shift to lower mol wt was observed under dissociative conditions. To probe the mechanism of IL-1 action, cartilage samples were incubated with IL-1 in the presence of the protein synthesis inhibitor, cycloheximide, or the lysosomal membrane-stabilizing steroid, hydrocortisone. Cycloheximide at 5-10 micrograms/ml completely blocked IL-1-induced breakdown. One the other hand, 3 x 10(-7) M hydrocortisone had little or no effect on IL-1 action. IL-1 was also shown to stimulate the degradation of human articular cartilage.

Animals↗
PubMed1988

Canine osteoarthritis: effects of endogenous neutral metalloproteoglycanases on articular cartilage proteoglycans.

The aim of this study was to analyze the mechanisms by which neutral metalloproteoglycanases (NMPE) degrade proteoglycans (PGs) in the cartilage of an experimental model of osteoarthritis (OA). We demonstrated that chondrocytes in osteoarthritic cartilage synthesize PGs with the same functional characteristics as those found in normal cartilage. Osteoarthritic cartilage contains NMPE in both active and latent forms. Both forms can degrade newly synthesized and endogenous PG macromolecules, as indicated by the reduced hydrodynamic size found in the two PG populations of osteoarthritic cartilage. PG monomers, derived from the included fraction of Sepharose CL2B chromatography, were unable to form aggregates with hyaluronic acid. Reduction and alkylation showed that PG monomers from osteoarthritic cartilage had a small hydrodynamic size, especially after activation with amino-phenylmercuric acetate. No significant differences were observed in the size of the chondroitin sulfate chain when normal cartilage was compared with its osteoarthritic equivalent. These results suggest that the proteolytic degradation of cartilage matrix PGs by NMPE occurs at both the hyaluronate-binding region and at the chondroitin sulfate-rich region of the core protein.

Animals↗
PubMed1989

Articular cartilage and intervertebral disc proteoglycans differ in structure: an electron microscopic study.

Articular cartilage and the intervertebral disc tissues have different material and biological properties and different patterns of aging and degeneration. To determine if the proteoglycans of these tissues differ in structure, we used the electron microscopic monolayer technique to compare baboon articular cartilage proteoglycans with baboon annulus fibrosus, transition zone, and nucleus pulposus proteoglycans. Intervertebral disc and articular cartilage proteoglycans differed significantly. Articular cartilage contained large proteoglycan aggregates formed from hyaluronic acid central filaments, multiple monomers, and large nonaggregated monomers. These molecules were identical to those of nasal cartilage, growth plate cartilage, chondrosarcomas, or menisci. In contrast, the intervertebral disc tissues contained only nonaggregated proteoglycan monomers and clusters of monomers without apparent central filaments. Intervertebral disc nonaggregated monomers were shorter and more variable in length than those from articular cartilage, and nucleus pulposus nonaggregated monomers were even shorter and more variable in length than transition zone and annulus fibrosus monomers. These observations suggest that significant differences in proteoglycan metabolism exist between articular cartilage and intervertebral disc.

Animals↗
PubMed1994

Mechanical properties of canine articular cartilage are significantly altered following transection of the anterior cruciate ligament.

The compressive, tensile, and swelling properties of articular cartilage were studied at two time periods following transection of the anterior cruciate ligament in the knee of greyhound dogs. An experimental protocol was designed to quantify the essential equilibrium and biphasic material properties of cartilage in tension, compression, and shear, as well as the parameters of isometric swelling behavior. All properties were measured at several sites to elicit differences between sites of frequent and less frequent contact. Hydration was determined at each site and was compared with the material properties of cartilage from corresponding sites. There were extensive changes in all compressive, tensile, and swelling properties of cartilage after transection of the anterior cruciate ligament. Twelve weeks after surgery, the intrinsic moduli were reduced significantly in compression (approximately 24% of control values), tension (approximately 64%), and shear (approximately 24%), and the hydraulic permeability was elevated significantly (approximately 48%). Significant increases in hydration (approximately 9%) also were observed, as well as a strong correlation of hydration with hydraulic permeability. The pattern of these changes was not found to differ with site in the joint, but significant differences were observed in the magnitude of change for cartilage from the femoral groove and the femoral condyle. The pattern and extent of changes in the material properties following transection of the anterior cruciate ligament indicate that altered loading of the joint severely compromises the overall mechanical behavior of articular cartilage. The observed loss of matrix stiffness in compression, tension, and shear is associated with increases in the deformation of the solid matrix, a diminished ability to resist swelling, and the increase in hydration observed in this study. The increased swelling and elevated water content were related directly to the increase in hydraulic permeability; this suggests an associated loss of fluid pressurization as the load support mechanism in the degenerated cartilage. Without a successful mechanism for repair, damage to the solid matrix may progress and lead to further degenerative changes in the biochemistry, morphology, and mechanical behavior of articular cartilage.

Animals↗
PubMed1996

Contents and distributions of the proteoglycans decorin and biglycan in normal and osteoarthritic human articular cartilage.

The study was designed to determine the contents and distributions of the proteoglycans decorin and biglycan in adult human femoral condylar cartilage and whether these may change in osteoarthritis. New radioimmunoassays were established using peptides representing the amino-terminal 21 amino acid sequence of each proteoglycan (to which a tyrosine was added for radioiodination) and antibodies in a rabbit antiserum raised to both these molecules. Cartilage was extracted with 4 M guanidine HCl to determine total content, and extracts were analyzed by chromatography to determine molecular sizes. Frozen sections were cut parallel to the articular surface and were extracted to determine distribution within the tissue. Gel chromatography on Sepharose CL-2B under dissociative conditions revealed molecules with a partition coefficient of 0.7-0.75 in both normal and osteoarthritic cartilage. In normal adult cartilage, the mean contents of the core proteins of biglycan and decorin were calculated to be approximately 0.34 and 0.48 mg per gram wet weight, respectively. These represented molar contents similar to that of aggrecan. In osteoarthritic cartilage, there were no overall significant changes in the content and distribution of these molecules. There was, however, considerable individual variation in both distribution and content. Analyses indicated that there was a trend in osteoarthritic cartilage toward a loss of biglycan and decorin from the more superficial layers of intact cartilage, where both these molecules are normally more concentrated. This was accompanied by maintenance of proteoglycan content deeper in the cartilage, regardless of the degree of degeneration.

Adult↗
PubMed1997

Physical properties of rabbit articular cartilage after transection of the anterior cruciate ligament.

The effect of unilateral transection of the anterior cruciate ligament on the confined compression and swelling properties of the distal femoral articular cartilage of skeletally mature rabbits at 9 weeks after surgery was determined. Gross morphological grading of the transected and contralateral control distal femora stained with India ink confirmed that cartilage degeneration had been induced by ligament transection. Osteochondral cores, 1.8 mm in diameter, were harvested from the medial femoral condyles. The modulus, permeability, and electrokinetic (streaming potential) coefficient of the articular cartilage of the osteochondral cores were assessed by confined compression creep experiments. The properties (mean +/- SD) of control cartilage were: confined compression modulus, 0.75 +/- 0.28 MPa; hydraulic permeability, 0.63 +/- 0.28 x 10(-15) m2/Pa*sec; and electrokinetic coefficient, 0.16 +/- 0.31 x 10(-9) V/Pa. In transected knees, the modulus was reduced by 18% (p = 0.04), while the permeability and electrokinetic coefficient were not detectably altered. The change in modulus was accompanied by a trend (p = 0.07) toward a decrease (-11%) in the glycosaminoglycan density within the tissue, a significant increase (p < 0.001) in the water content of the cartilage after equilibration in 1 x phosphate buffered saline from 70.3 +/- 4.1% in control knees to 75.2 +/- 4.0% in transected knees, and little further swelling after tissue equilibration in hypotonic saline. The compressive modulus of the cartilage from both control and transected knees was positively correlated with the density of tissue glycosaminoglycan. The alterations in the physical properties of the articular cartilage after transection of the anterior cruciate ligament in the rabbit show trends similar to those observed in human and other animal models of osteoarthritis and provide further support for the use of this model in the study of cartilage degeneration.

Animals↗
PubMed1997

Repeatability of patellar cartilage thickness patterns in the living, using a fat-suppressed magnetic resonance imaging sequence with short acquisition time and three-dimensional data processing.

A fast, reproducible, and noninvasive method is required for quantifying cartilage thickness clinically and for studying the deformation of articular cartilage during and after mechanical loading in vivo. The objective of the current investigation was to test the repeatability of regional distribution patterns of patellar cartilage thickness in the living on the basis of a fat-suppressed magnetic resonance imaging sequence with a short acquisition time and three-dimensional digital data processing. The knees of eight healthy volunteers were transversally imaged with a fat-suppressed FLASH-3D (fast low angle shot) sequence (acquisition time: 4 minutes and 10 seconds). In each case, the joint was newly positioned before each of the six replicate measurements was taken. The patellar cartilage was reconstructed three-dimensionally, and the distribution of cartilage thickness was determined with a three-dimensional minimal-distance algorithm. Whereas the cartilage volume ranged from 3,198 to 7,149 mm3, the mean coefficient of variation for the 6-fold volume measurement was 1.35%. On average, 75.1% (+/- 4.1%) of all test pixels could be attributed to the same cartilage thickness interval (0.5 mm) by image analysis; 14.8% (+/- 2.4%) deviated by one interval; 6.6% (+/- 1.5%), by two intervals; and 3.5% (+/- 1.8%), by more than two intervals. We conclude that, on the basis of a magnetic resonance imaging sequence with an acquisition time of less than 5 minutes, the quantitative distribution of cartilage thickness can be determined with high precision in vivo.

Adult↗
PubMed1998

Exposure of cartilage to a fibronectin fragment amplifies catabolic processes while also enhancing anabolic processes to limit damage.

The addition of fibronectin fragments to cultured cartilage causes an initial suppression of proteoglycan synthesis, induction of matrix metalloproteinases, and resultant decrease in proteoglycan content by about 50% during the first few days in culture. Because the proteoglycan loss appears to be limited, we investigated whether the fibronectin fragments induce anabolic responses that might counter the damage. The effects of various lengths of exposure of cultured cartilage to the fibronectin fragment on proteoglycan content, proteoglycan synthesis rates, stromelysin-1 release, and tumor necrosis factor-alpha, interleukin-1alpha, and interleukin-6 release were investigated. The results showed that about 7 days of exposure of cultured cartilage to the fibronectin fragment was required for maximal cytokine release, proteoglycan depletion, and stromelysin-1 release. However, nearly maximal suppression of proteoglycan synthesis occurred within 1 day of the addition of the fibronectin fragment and, after its removal, the rates increased to supernormal levels. Decreasing exposure to 3 days caused only a small decrease in cartilage proteoglycan content, although stromelysin-1 release still occurred. Decreasing exposure to 1 day caused an immediate increase in proteoglycan synthesis and an increase to supernormal proteoglycan contents. The effect of first treating cartilage with the fibronectin fragment for various periods and then allowing a recovery was to make the cartilage more resistant to secondary exposures. This study shows that cartilage damage can be caused by short exposures to the fibronectin fragment and that exposures either optimal or suboptimal for damage additionally amplify anabolic processes to make the cartilage resistant to further damage and, thus, condition it against pending amplification of damage.

Animals↗
PubMed1999

Effect of seeding duration on the strength of chondrocyte adhesion to articular cartilage.

Chondrocyte adhesion to cartilage may play an important role in the repair of articular defects by maintaining cells in positions where their biosynthetic products can contribute to the repair process. The objective of this in vitro study was to determine the effect of the duration of seeding time on the ability of chondrocytes to resist detachment from cartilage when subjected to mechanical perturbation (fluid-induced shear stress). Suspensions of adult bovine articular chondrocytes were prepared from primary, high-density monolayer cultures and infused into a parallel-plate shear-flow chamber where they settled onto 50-microm-thick sections of bovine articular cartilage at a density of approximately 20,000 cells/cm2. The chondrocytes were seeded and allowed to attach to the cartilage surface for specific durations (5-40 minutes) in medium including 10% serum at 22 degrees C, after which the cells were exposed to fluid flow-induced shear stresses (6-90 Pa). The fraction of detached cells at each shear stress was calculated from microscopic images. Shear stress was applied for 1 minute because this length of time was sufficient to induce steady-state cell detachment. Increasing the duration of cell seeding led to a more firm attachment of chondrocytes to cartilage. After 9 minutes of seeding, 50% cell detachment was induced by gravitational force alone. After 40 minutes of seeding, 50% detachment required 26 Pa of shear stress. Extrapolation of the data to account for the effect of repeated applications of cell suspensions to an individual cartilage substrate indicated that for a freshly prepared cartilage section, 50% detachment was induced by gravity after 25 minutes of seeding and by 2.3 Pa of shear stress after 40 minutes of seeding. The increase in resistance to shear stress-induced cell detachment with increasing seeding duration suggests that it may be beneficial to allow chondrocytes to stabilize in the absence of applied load for some time after chondrocyte transplantation for cartilage repair in vivo.

Animals↗
PubMed2007

Quantitative and topographical evaluation of ankle articular cartilage using high resolution MRI.

The objectives of this study were to quantitatively evaluate the articular cartilage layers of the ankle and describe the cartilage topographical distribution across the joint surfaces using high resolution MRI and image segmentation. An anisotropic diffusion noise reduction algorithm and a directional gradient vector flow (dGVF) snake segmentation algorithm were applied to cartilage sensitive MR images. Eight cadaveric ankles were studied. Six repeated data sets were acquired in five of the ankles. Quantitative parameters were calculated for each cartilage layer; coefficients of variation (CV) were calculated from the six repeated data sets; and 3D thickness distribution maps were generated. The noise reduction algorithm produced marked image enhancement. Mean cartilage thickness ranged from 0.91 +/- 0.08 mm in the fibula to 1.34 +/- 0.14 mm in the talus. Mean cartilage volume was 3.32 +/- 0.55 ml, 1.72 +/- 0.25 ml, and 0.35 +/- 0.06 ml for the talus, tibia, and fibula, respectively. Mean CV ranged 2.82%-5.04% for quantitative parameters in the talus and tibia. The reported noise reduction and segmentation technique allow precise extraction of ankle cartilage and 3D reconstructions show that the thickest cartilage occurs over the talar shoulders, where osteochondritits dissecans (OCD) lesions commonly occur.

Algorithms↗
PubMed2002

Comparison of collagen dynamics in articular cartilage and isolated fibrils by solid-state NMR spectroscopy.

Native pig articular cartilage was investigated by (13)C cross polarization (CP) magic angle spinning (MAS) NMR at a magnetic field strength of 17.6 T. CP MAS spectra of cartilage are dominated by resonances from rigid collagen, while only low-intensity signals from the glycosaminoglycans are observed. The spectral resolution of collagen fibrils in native cartilage is somewhat higher than for isolated collagen fibrils from bovine achilles tendon investigated for comparison. This is confirmed qualitatively by (1)H-(1)H wideline separation spectra that show much lower line widths for cartilage collagen compared to isolated collagen. The strength of (1)H-(13)C dipolar couplings was measured in a 2D LG CP experiment providing a motionally averaged dipolar coupling value for each resolved signal. These scaled couplings were converted to molecular order parameters for the CH bond vector. Typical order parameters for isolated collagen were 0.91-0.96 for sidechains and 0.98-1.00 for the backbone. Somewhat lower order parameters were determined for cartilage collagen; 0.79-0.90 for the sidechain and 0.92-0.97 for the backbone. The only glycosaminoglycan signals that could be detected by CP MAS show order parameters of 0.48-0.92 and are assigned to relatively rigid hyaluronan and keratan sulfate. The higher mobility of collagen in cartilage is due to the high water content and collisions with the isotropically mobile glycosaminoglycans, such as chondroitin sulfate. Therefore, the mobility of cartilage macromolecules is broadly distributed from almost completely rigid to highly mobile, which lends cartilage its mechanical strength and shock-absorbing properties.

Achilles Tendon↗
PubMed2002

Spatial assessment of articular cartilage proteoglycans with Gd-DTPA-enhanced T1 imaging.

In Gd-DTPA-enhanced T(1) imaging of articular cartilage, the MRI contrast agent with two negative charges is understood to accumulate in tissue inversely to the negative charge of cartilage glycosaminoglycans (GAGs) of proteoglycans (PGs), and this leads to a decrease in the T(1) relaxation time of tissue relative to the charge in tissue. By assuming a constant relaxivity for Gd-DTPA in cartilage, it has further been hypothesized that the contrast agent concentration in tissue could be estimated from consecutive T(1) measurements in the absence or presence of the contrast agent. The spatial sensitivity of the technique was examined at 9.4 T in normal and PG-depleted bovine patellar cartilage samples. As a reference, spatial PG concentration was assessed with digital densitometry from safranin O-stained cartilage sections. An excellent linear correlation between spatial optical density (OD) of stained GAGs and T(1) with Gd-DTPA was observed in the control and chondroitinase ABC-treated cartilage specimens, and the MR parameter accounted for approximately 80% of the variations in GAG concentration within samples. Further, the MR-resolved Gd-DTPA concentration proved to be an even better estimate for PGs, with an improved correlation. However, the linear relation between MR parameters and PG concentration did not apply in the deep tissue, where MR measurements overestimated the PG content. While the absolute [Gd-DTPA] determination may be prone to error due to uncertainty of relaxivity in cartilage, or to other contributing factors such as variations in tissue permeability, the experimental evidence highlights the sensitivity of this technique to reflect spatial changes in cartilage PG concentration in normal and degenerated tissue.

Animals↗
PubMed2002

Relaxivity and diffusion of gadolinium agents in cartilage.

Prior work indicates that the distribution of Gd(DTPA)(2-) (as measured by T(1)) is a good surrogate measure of the distribution of gycosaminoglycan (GAG) in cartilage. In addition to the measured T(1) in the presence of Gd(DTPA)(2-), the precision of the measurement of Gd(DTPA)(2-) concentration depends on the T(1) without Gd(DTPA)(2-) (T(o)(1)), and the relaxivity (r) of Gd(DTPA)(2-) in cartilage, parameters that are influenced by cartilage composition. These parameters were measured in native and GAG-depleted cartilage in order to estimate the bounds on the values one might expect for cartilage in arbitrary states of degeneration. The range of T(o)(1) was 0.3 sec; the range of r was 0.6 (mM*s)(-1) at 8.5 T and 1.4 (mM*s)(-1) at 2 T. These data suggest that Gd(DTPA)(2-) will be underestimated (and GAG overestimated) if the values for T(o)(1) and r are assumed to be those of native cartilage. (For example, in a severe case a 90% loss of GAG would be underestimated as a 70% loss.) Gd(HPDO3A) was investigated as a nonionic "control agent" and found to have relaxivity and diffusion properties that were comparable to Gd(DTPA)(2-) (r(Gd(HPDO3A))/r(Gd(DTPA)) approximately 1; D(Gd(HPDO3A))/D(Gd(DTPA)) approximately 0.85). Since Gd(HPDO3A) distributes uniformly through cartilage (independent of GAG), the distribution of T(1) with Gd(HPDO3A) can be used as a surrogate measure of variations in T(o)(1) and r, if present. From the perspective of transport, if Gd(HPDO3A) has fully penetrated the cartilage, Gd(DTPA)(2-) would have in the same time frame. Therefore, the data confirm the efficacy of using Gd(HPDO3A) as a "control agent" for dGEMRIC.

Animals↗
PubMed1993

Analysis of water-macromolecule proton magnetization transfer in articular cartilage.

These studies were designed to establish which structural elements of cartilage are responsible for proton magnetization transfer between water (Hf) and macromolecules (Hr) observed in MRI studies on articular cartilage. Saturation transfer techniques were used to monitor magnetization transfer in vitro on samples of the two major constituents of cartilage: collagen and proteoglycan. Articular cartilage samples were also evaluated in vitro before and after the removal of the proteoglycan fraction. Isolated hydrated collagen exhibited a significant proton magnetization transfer rate with water. In contrast, proteoglycans exhibited no proton magnetization transfer. Articular cartilage, in vitro, exhibited a high degree of magnetization transfer with water protons consistent with previous MRI studies in vivo. Enzymatic removal of proteoglycan from the cartilage did not alter the magnetization transfer rate between Hr and Hf. These data demonstrate that the structure and concentration of the collagen matrix are the predominant determinants of the magnetization transfer process in articular cartilage with little or no contribution from proteoglycans. This specificity of the magnetization transfer effect may prove useful in the noninvasive evaluation of cartilage composition and structure in vivo.

Animals↗