Baylon, E. G. | bioRxiv Science

bioRxiv2019

Non-ionic CT Contrast Solutions Rapidly Alter Bovine Cartilage and Meniscus Mechanics

ObjectiveTo evaluate effects of a common CT contrast agent (iohexol) on the mechanical behaviors of cartilage and meniscus. MethodsIndentation responses of juvenile bovine cartilage and meniscus were monitored following exposure to undiluted contrast agent (100% CA), 50% CA/water, 50% CA/Phosphate Buffered Saline (PBS) or PBS alone, and during re-equilibration in PBS. The normalized peak force [Formula], effective osmotic strain ({varepsilon}osm), and normalized effective contact modulus [Formula] were calculated for every cycle, with time constants determined for both exposure and recovery via mono- or biexponential fits to [Formula]. ResultsAll cartilage CA groups exhibited long-term increases in [Formula] following exposure, although the hyperosmolal 100% CA and 50% CA/PBS groups showed an initial transient decrease. Meniscus presented opposing trends, with decreasing [Formula] for all CA groups. Re-equilibration in PBS for 1hr after exposure to 100% CA did not produce recovery to baseline [Formula] in either tissue. The recovery time for meniscus was substantially longer than that of cartilage. [Formula] increased with CA exposure time for cartilage but decreased for meniscus, suggesting an increased effective stiffness for cartilage and decreased stiffness for meniscus. Long-term changes to{varepsilon} osm in both tissues were consistent with changes in [Formula]. ConclusionExposure to iohexol solutions affected joint tissues differentially, with increased cartilage stiffness, likely relating to competing hyperosmotic and hypotonic interactions with tissue fixed charges, and decreased meniscus stiffness, likely dominated by hyperosmolarity. These altered tissue mechanics could allow non-physiological deformation during ambulatory weight-bearing, resulting in an increased risk of tissue or cell damage.

bioengineering↗

bioRxiv2018

Osmotic Swelling Responses are Conserved Across Cartilaginous Tissues with Varied Sulfated-Glycosaminoglycan Contents

The interactions between the negatively charged sulfated glycosaminoglycan (sGAG) chains and the ionic interstitial fluid in articular cartilage and meniscal fibrocartilage give rise to an osmotic swelling stress that is critical for the load-bearing capability of both tissues. This osmotic swelling stress is altered when the sGAG content is changed, as during progression of degenerative joint disease; understanding the influence of sGAG concentration on the osmotic swelling stress of cartilage and meniscus is important to enhance our understanding of physiology and disease. This study compared the effect of altered osmotic environments on the confined compression swelling behavior of bovine tissues spanning a range of sGAG concentrations: juvenile articular cartilage, juvenile and adult meniscus, and juvenile cartilage degraded to reduce sGAG content. The transient response to changes in bath conditions was evaluated for explants assigned to one of three compressive offsets (5%, 10%, or 15% strain) and one of three bath conditions (0.1X, 1X, or 10X Phosphate Buffered Saline). Our results show that relative responses to alterations to the osmotic environment are consistent across tissue types, demonstrating that the role of sGAG in the swelling properties of the tissues tested is conserved, even when sGAG is present at low concentrations. Additionally, this study found unexpected correlations across tissue types between sGAG and collagen contents and between the aggregate modulus and both sGAG and collagen contents. These results suggest some conservation of composition-function relationships across a range of tissue types.

bioengineering↗