Background/Purpose: Osteochondral unit is a bio composite responsible for an optimal distribution of load during movements and axial compression of a joint. Any alteration of tissue mechanical properties (cartilage or bone) could interfere with an optimal function. One obvious question is to understand whether alteration of subchondral bone turnover (i.e. quality) could affect cartilage quality and thus represent a potential risk of OA development.

Methods:

To verify this hypothesis, 15 adult female rats where ovariectomized (OVX, n=10) or SHAM operated (n=5). One group of OVX rats was treated for 8 weeks with pamidronate (APD) at dose of 0.6 mg/kg, 5 days/mo SC to inhibit the increase of bone turnover, and the other two groups received the solvent. At the end of the study, distal femurs were harvested. Bio-indentations (CSM, Switzerland) were performed at the level of the medial condyle at three different area submitted physiologically to different mechanical loading. Elastic modulus (MPa) and indentation depth (mM) were recorded, using different load from 0.05 to 8 mN. Indentation depths were located in the upper third of the hyaline cartilage. Cartilage thickness was evaluated by contrast enhanced computed tomography with ionic contrast agent using (Hexabrix^®) at the site of indentation as well as subchondral bone micro architecture. Blood and urine were collected to evaluate bone turnover using measurement of osteocalcin and deoxypyridinoline excretion. Values are mean±SEM; significance of differences was obtained using an ANOVA.

Results:

* versus sham, ° versus OVX (ANOVA)

An increment of markers of bone turnover was observed in OVX rats and was fully prevented by APD administration. OVX resulted in alteration of bone microarchitecture of the subchondral bone as demonstrated by a reduce bone volume (BV/TV) and trabecular thickness (Tb.Th); all these alterations were fully prevented by APD administration. Hyaline and mineralized cartilage thicknesses were not affected by OVX nor by APD treatments. OVX was associated with alteration of cartilage tissue quality as indicated by a decreased of modulus and increased indentation depth. All these alterations were fully prevented by APD treatment preventing the increment in subchondral bone turnover.

Conclusion:

All together these results demonstrate that in rat, an increment of subchondral bone turnover and/or alteration of the local micro architecture is associated with degradation of the cartilage tissue quality independently of the estrogen deficiency. These results underline the crucial role plays by subchondral bone as “regulator” of cartilage quality.

« Back to 2017 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/modulation-of-subchondral-bone-turnover-is-associated-with-alteration-of-cartilage-tissue-quality/