ADAMTS-5 deficient mice do not develop mechanical allodynia associated with osteoarthritis following medial meniscal destabilization

OBJECTIVE

To characterize pain-related behavior during the course of knee osteoarthritis (OA) induced by destabilization of the medial meniscus (DMM) in wild type (WT) and in ADAMTS-5 null mice.

METHODS

DMM surgery was performed in the right knee of CD-1 mice. At regular intervals up to 8 weeks after surgery, mice were assessed for the following parameters: mechanical allodynia (via withdrawal thresholds to von Frey filaments applied to the plantar surface of both hind paws or to the tail), thermal hyperalgesia, locomotor activity and gait analysis. In addition, mechanical allodynia was tested in C57BL/6 WT or ADAMTS-5 null mice following DMM surgery.

RESULTS

In CD-1 mice, a robust and progressive decrease in withdrawal threshold was observed in both hind paws after DMM but not sham surgery. Allodynia was apparent as early as 14 days postoperatively. Both sexes developed OA changes after surgery with concurrent mechanical allodynia. No other pain-related behavioral changes were detected up to 8 weeks post-surgery. In C57BL/6 mice, a genetic background in which only males develop OA changes after DMM, males but not females developed allodynia in the ipsilateral hind paw. In contrast, C57BL/6 ADAMTS-5 null mice did not develop OA changes or mechanical allodynia up to 8 weeks post-surgery.

CONCLUSION

Joint pathology following DMM surgery in mice is associated with progressive mechanical allodynia. ADAMTS-5 null mice are resistant to DMM-induced OA-like lesions and to the associated mechanical allodynia.

Effect of prostaglandin and bisphosphonate on cancellous bone volume and structure in the ovariectomized rat studied by quantitative three-dimensional nuclear magnetic resonance microscopy

The purpose of this work was to evaluate the potential of nuclear magnetic resonance microscopy (NMRM) in conjunction with a processing technique to monitor the effect of preventive agents in an ovariectomized (OVX) rat. Twenty-five female Sprague-Dawley rats were OVX at 6 months of age (except for the intact control group), allowed to lose bone for 60 days, and then treated for 60 days. During treatment, animals were administered vehicle, prostaglandin E2 (PGE2; 6 mg/kg), or alendronate (3 microg/kg) subcutaneously once a day. Subsequently, tibiae were harvested and the marrow removed. NMRM was carried out at 9.4 T, with the specimens immersed in 1.2 mM diethylenetriaminepentaacetic acid-gadolinium salt (Gd-DTPA) aqueous solution. A three-dimensional (3D) partial flip-angle pulse sequence was used, providing a 1283 array of (46 microm)3 isotropic voxels. Fifty of the 128 axial images in the 3D data set comprising approximately 2.4 mm volume distal to the growth plate were processed from each specimen using a probability-based method for determining bone volume fraction (BVF), tubularity, contiguity, as well as the mean trabecular plate thickness and separation. PGE2 and alendronate altered BVF consistently at all tibial regions. The effect of alendronate was to keep BVF about midway between intact and OVX, whereas PGE2 returned BVF to intact levels. The other parameters showed similar responses to treatment. The strongest discriminator was trabecular BVF, which could obviously differentiate the groups. The study establishes NMRM as a nondestructive histomorphometric method for the quantitative evaluation of drug response in a rat ovariectomy model.

Nondestructive imaging of human cartilage glycosaminoglycan concentration by MRI

Despite the compelling need mandated by the prevalence and morbidity of degenerative cartilage diseases, it is extremely difficult to study disease progression and therapeutic efficacy, either in vitro or in vivo (clinically). This is partly because no techniques have been available for nondestructively visualizing the distribution of functionally important macromolecules in living cartilage. Here we describe and validate a technique to image the glycosaminoglycan concentration ([GAG]) of human cartilage nondestructively by magnetic resonance imaging (MRI). The technique is based on the premise that the negatively charged contrast agent gadolinium diethylene triamine pentaacetic acid (Gd(DTPA)2-) will distribute in cartilage in inverse relation to the negatively charged GAG concentration. Nuclear magnetic resonance spectroscopy studies of cartilage explants demonstrated that there was an approximately linear relationship between T1 (in the presence of Gd(DTPA)2-) and [GAG] over a large range of [GAG]. Furthermore, there was a strong agreement between the [GAG] calculated from [Gd(DTPA)2-] and the actual [GAG] determined from the validated methods of calculations from [Na+] and the biochemical DMMB assay. Spatial distributions of GAG were easily observed in T1-weighted and T1-calculated MRI studies of intact human joints, with good histological correlation. Furthermore, in vivo clinical images of T1 in the presence of Gd(DTPA)2- (i.e., GAG distribution) correlated well with the validated ex vivo results after total knee replacement surgery, showing that it is feasible to monitor GAG distribution in vivo. This approach gives us the opportunity to image directly the concentration of GAG, a major and critically important macromolecule in human cartilage.