Abstract
BackgroundOsteochondral allograft transplantation has a good clinical outcome, however, there is still debate on optimization of allograft storage protocol. Storage temperature and nutrient medium composition are the most critical factors for sustained biological activity of grafts before implantation. In this study, we performed a time-dependent in vitro experiment to investigate the effect of various storage conditions on electromechanical, histological and histochemical properties of articular cartilage.MethodsOsteochondral grafts derived from goat femoral condyles were frozen at −70 °C or stored at 4 °C and 37 °C in the medium supplemented with or without insulin-like growth factor-1 (IGF-1). After 14 and 28 days the cartilage samples were quantitatively analysed for electromechanical properties, glycosaminoglycan distribution, histological structure, chondrocyte viability and apoptosis. The results were compared between the experimental groups and correlations among different evaluation methods were determined.ResultsStorage at −70 °C and 37 °C significantly deteriorated cartilage electromechanical, histological and histochemical properties. Storage at 4 °C maintained the electromechanical quantitative parameter (QP) and glycosaminoglycan expression near the normal levels for 14 days. Although hypothermic storage revealed reduced chondrocyte viability and increased apoptosis, these parameters were superior compared with the storage at −70 °C and 37 °C. IGF-1 supplementation improved the electromechanical QP, chondrocyte viability and histological properties at 37 °C, but the effect lasted only 14 days. Electromechanical properties correlated with the histological grading score (r = 0.673, p < 0.001), chondrocyte viability (r = −0.654, p < 0.001) and apoptosis (r = 0.416, p < 0.02). In addition, apoptosis correlated with glycosaminoglycan distribution (r = −0.644, p < 0.001) and the histological grading score (r = 0.493, p = 0.006).ConclusionsOur results indicate that quality of allografts is better preserved at currently established 4 °C storage temperature. Storage at −70 °C or at 37 °C is unable to maintain cartilage function and metabolic activity. IGF-1 supplementation at 37 °C can enhance chondrocyte viability and improve electromechanical and histological properties of the cartilage, but the impact persists only 14 days. The correlations between cartilage electromechanical quantitative parameter (QP) and metabolic activity were detected. Our findings indicate that non-destructive assessment of cartilage by Arthro-BST is a simple and reliable method to evaluate allograft quality, and could be routinely used before implantation.
Highlights
Osteochondral allograft transplantation has a good clinical outcome, there is still debate on optimization of allograft storage protocol
This study suggested that the apoptotic process could be manipulated to enhance chondrocyte survival and improve the results of osteochondral allograft transplantation
When the culture medium was supplemented with insulin-like growth factor-1 (IGF-1), there was a slight increase of quantitative parameter (QP) for the grafts stored at 4 °C (4.53 ± 0.27), a considerable decrease of QP was detected for the grafts stored at 37 °C (4.77 ± 0.32; p = 0.043)
Summary
Osteochondral allograft transplantation has a good clinical outcome, there is still debate on optimization of allograft storage protocol. Autologous osteochondral transplantation has demonstrated good to excellent clinical results [10,11,12,13], its use is limited due to the lack of healthy cartilage tissue and related donor site morbidity [14, 15]. Longterm in vitro maintenance of osteochondral allograft tissue poses a very big challenge, especially for cell viability. Implantation of viable chondrocytes can assure prolonged maintenance of the extracellular matrix and integrity of the articular cartilage after transplantation. Despite numerous studies on allograft preparation, storage conditions and already approved protocols used by tissue banks, research on how to maintain viable cells is still ongoing [18, 28]. Hypothermic storage at 4 °C, currently used by most tissue banks, has been shown capable of maintaining chondrocyte viability and matrix integrity [32,33,34]. Allograft storage at 37 °C has been proposed, because superior results in comparison with refrigeration have been reported [29, 35]
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