Osmolarity influences chondrocyte death in wounded articular cartilage

Department of Orthopaedic and Trauma Surgery, University of Edinburgh, Old Dalkeith Road, Edinburgh EH16 4SU, Scotland, UK.
The Journal of Bone and Joint Surgery (Impact Factor: 4.31). 07/2008; 90(7):1531-42. DOI: 10.2106/JBJS.G.00857
Source: PubMed

ABSTRACT Mechanical injury results in chondrocyte death in articular cartilage. The purpose of the present study was to determine whether medium osmolarity affects chondrocyte death in injured articular cartilage.
Osteochondral explants (n = 48) that had been harvested from the metacarpophalangeal joints of three-year-old cows were exposed to media with varying osmolarity (0 to 480 mOsm) for ninety seconds to allow in situ chondrocytes to respond to the altered osmotic environment. Explants were then wounded with a scalpel through the full thickness of articular cartilage, incubated in the same media for 2.5 hours, and transferred to 340-mOsm Dulbecco's Modified Eagle Medium (control medium) with further incubation for seven days. The spatial distribution of in situ chondrocyte death, percentage cell death, and marginal cell death at the wounded cartilage edge were compared as a function of osmolarity and time (2.5 hours compared with seven days) with use of confocal laser scanning microscopy.
In situ chondrocyte death was mainly localized to the superficial tangential zone of injured articular cartilage for the range of medium osmolarities (0 to 480 mOsm) at 2.5 hours and seven days. Therefore, a sample of articular cartilage from the superficial region (which included the scalpel-wounded cartilage edge) was studied with use of confocal laser scanning microscopy to compare the effects of osmolarity on percentage and marginal cell death in the superficial tangential zone. Compared with the control explants exposed to 340-mOsm Dulbecco's Modified Eagle Medium, percentage cell death in the superficial tangential zone was greatest for explants exposed to 0-mOsm (distilled water) and least for explants exposed to 480-mOsm Dulbecco's Modified Eagle Medium at 2.5 hours (13.0% at 340 mOsm [control], 35.5% at 0 mOsm, and 4.3% at 480 mOsm; p <or= 0.02 for paired comparisons) and seven days (9.9% at 340 mOsm [control], 37.7% at 0 mOsm, and 3.5% at 480 mOsm; p <or= 0.01 for paired comparisons). Marginal cell death in the superficial tangential zone decreased with increasing medium osmolarity at 2.5 hours (p = 0.001) and seven days (p = 0.002). There was no significant change in percentage cell death from 2.5 hours to seven days for explants initially exposed to any of the medium osmolarities.
Medium osmolarity significantly affects chondrocyte death in wounded articular cartilage. The greatest chondrocyte death occurs at 0 mOsm. Conversely, increased medium osmolarity (480 mOsm) is chondroprotective. The majority of cell death occurs within 2.5 hours, with no significant increase over seven days.

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    ABSTRACT: Exposure of articular cartilage to static air results in changes to the extracellular matrix and stimulates chondrocyte death, which may cause joint degeneration. However during open orthopaedic surgery, cartilage is often exposed to laminar airflow, which may exacerbate these damaging effects. We compared drying in static and moving air in terms of cartilage appearance, hydration and chondrocyte viability, and tested the ability of saline-saturated gauze to limit the detrimental effects of air exposure. Articular cartilage from bovine metatarsophalangeal joints (N=50) and human femoral heads (N=6) was exposed for 90mins to (1) static air (2) airflow (up to 0.34m/s), or (3) airflow (0.18m/s), covered with gauze. Following air exposure, cartilage was also rehydrated (0.9% saline;120mins) to determine the reversibility of drying effects. The influence of airflow was assessed by studying macroscopic appearance, and quantifying superficial zone chondrocyte viability and cartilage hydration. Airflow caused advanced changes to cartilage appearance, accelerated chondrocyte death, and increased dehydration compared to static air. These effects were prevented if cartilage was covered by saline-saturated gauze. Cartilage rehydration reversed macroscopic changes associated with drying but the chondrocyte death was not altered. Chondrocytes at the cut edge of cartilage were more sensitive to drying compared to cells distant from the edge. Airflow significantly increased articular cartilage dehydration and chondrocyte death compared to static air. As laminar airflow is routinely utilised in operating theatres, it is essential that articular cartilage is kept wet via irrigation or by covering with saline-saturated gauze to prevent chondrocyte death. Copyright © 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
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