Osmolarity influences chondrocyte death in wounded articular cartilage
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: Bone lengthening during skeletal growth is driven primarily by the controlled enlargement of growth plate (GP) chondrocytes. The cellular mechanisms are unclear but membrane transporters are probably involved. We investigated the role of the Na(+) /H(+) antiporter (NHE1) and anion exchanger (AE2) in bone lengthening and GP chondrocyte hypertrophy in Sprague-Dawley 7-day-old rat (P7) bone rudiments using the inhibitors EIPA (5-(N-ethyl-N-isopropyl)amiloride) and DIDS (4,4-diidothiocyano-2,2-stilbenedisulphonate) respectively. We have also determined cell-associated levels of these transporters along the GP using fluorescent immunohistochemistry (FIHC). Culture of bones with EIPA or DIDS inhibited rudiment growth (50% at approx. 250µM and 25µM respectively). Both decreased the size of the hypertrophic zone (P<0.05) but had no effect on overall length or cell density of the GP. In situ chondrocyte volume in proliferative and hypertrophic zones was decreased (P<0.01) with EIPA but not DIDS. FIHC labelling of NHE1 was relatively high and constant along the GP but declined steeply in the late hypertrophic zone. In contrast, AE2 labelling was relatively low in proliferative zone cells but increased (P<0.05) reaching a maximum in the early hypertrophic zone, before falling rapidly in the late hypertrophic zone suggesting AE2 might regulate the transition phase of chondrocytes between proliferative and hypertrophic zones. The inhibition of bone growth by EIPA may be due to a reduction to chondrocyte volume set-point. However the effect of DIDS was unclear but could result from inhibition of AE2 and blocking of the transition phase. These results demonstrate that NHE1 and AE2 are important regulators of bone growth. J. Cell. Biochem. © 2012 Wiley Periodicals, Inc.Journal of Cellular Biochemistry 03/2013; 114(3). DOI:10.1002/jcb.24408 · 3.37 Impact Factor
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ABSTRACT: This systematic review provides (1) a synthesis of existing clinical evidence that helps identify factors associated with the development of glenohumeral chondrolysis after arthroscopy (PAGCL), (2) a consolidated conceptualization of potential causal pathways that elucidate proposed mechanisms leading to PAGCL, and (3) a summary of implications for practice, policy, and future research. A computerized literature review using an iterative search process identified 245 publications in English between January 1960 and April 2009. After we applied inclusion and exclusion criteria, 35 articles were stratified into 4 categories of factors related to PAGCL: (1) patient factors, (2) surgical factors (preoperative and intraoperative), (3) postoperative factors, and (4) causal pathways. The majority of studies (61%) focused on surgical factors correlated with PAGCL, and most were laboratory based (n = 21). Publications involving human subjects were descriptive case reports (n = 15), not epidemiologic studies. A total of 88 patients (91 shoulder surgeries) with PAGCL were identified in case reports. The majority of patients (55%) was male, and the mean age was 27.9 years (range, 13.1 to 64 years). Among patients, 68% (n = 53) had implants/anchors, 67% (n = 59) received local anesthetics through a pain pump, and 45% (n = 41) had surgeries involving radiofrequency devices. The causal pathways to PAGCL likely involve initiating and secondary cartilage injury due to mechanical, thermal, or chemical events. The result is a cascade of interactive cellular responses that may include inflammation and chondrocyte apoptosis causing disturbance of cellular metabolism with subsequent loss of the gliding surface, congruity, and synovial fluid, leading to increased friction and accelerated wear that ultimately yield PAGCL. The literature is limited to correlates, rather than true risk factors, for PAGCL. Well-designed epidemiologic studies that examine various exposures in relation to health outcomes, while controlling for potential confounders, are needed to determine relative risks that allow causal inference, thereby facilitating sound practice and policy decision making. Level IV, systematic review.Arthroscopy The Journal of Arthroscopic and Related Surgery 11/2009; 25(11):1329-42. DOI:10.1016/j.arthro.2009.06.001 · 3.19 Impact Factor
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ABSTRACT: Articular cartilage may experience iatrogenic injury during routine orthopaedic/arthroscopic procedures. This could cause chondrocyte death, leading to cartilage degeneration and posttraumatic osteoarthritis. In an in vitro cartilage injury model, chondrocyte death was reduced by increasing the osmolarity of normal saline, the most commonly-used irrigation solution. Here, we studied the effect of hyperosmolar saline on chondrocyte viability and cartilage repair in an in vivo injury model. Cartilage injury was induced by a single scalpel cut along the patellar groove of 8wk old rats in the absence of irrigation or with either normal (300mOsm) or hyperosmolar saline (600mOsm). The percentage of cell death (PCD) within the injured area was assessed using confocal microscopy. Repair from injury was evaluated by histology/immunostaining, and inflammatory response by histology, cytokine array analysis and ELISA. The PCD in saline-irrigated joints was increased compared to non-irrigated joints [PCD=20.8% (95%CI;14.5,27.1); PCD=9.14% (95%CI,;6.3,11.9);P=0.0017]. However, hyperosmotic saline reduced chondrocyte death compared to normal saline (PCD=10.4% (95%CI;8.5,12.3) P=0.0024). Repair score, type II collagen and aggrecan levels, and injury width, were significantly improved with hyperosmotic compared to normal saline. Mild synovitis and similar changes in serum cytokine profile occurred in all operated joints irrespective of experimental group. Hyperosmotic saline significantly reduced the chondrocyte death associated with scalpel-induced injury and enhanced cartilage repair. This irrigation solution might be useful as a simple chondroprotective strategy and may also reduce unintentional cartilage injury during articular reconstructive surgery and promote integrative cartilage repair, thereby reducing the risk of posttraumatic osteoarthritis. Copyright © 2014. Published by Elsevier Ltd.