Chondrocytes within Osteochondral Grafts Are More Resistant than Osteoblasts to Tissue Culture at 37°C

Abstract

It is proposed that an ideal osteochondral allograft for cartilage repair consists of a devitalized bone but functional cartilage. The different modes of nutrient supply in vivo for bone (vascular support) and cartilage (diffusion) suggest that a modulation of storage conditions could differentially affect the respective cells, resulting in the proposed allograft. For this purpose, osteochondral tissues from porcine humeral heads were either cultured at 37°C for up to 24 hr or stored at 4°C for 24 hr, the temperature at which osteochondral allografts are routinely stored. Functionality of the cells was assessed by in situ hybridization for transcripts encoding collagen types I and II. At 37°C, a time-dependent significant reduction of the bone surface covered with functional cells was observed with only 5% ± 5% coverage left at 24 hr compared with 41% ± 10% at 0 hr. Similarly, cartilage area containing functional cells was significantly reduced from 84% ± 7% at 0 hr to 70% ± 3% after 24 hr. After 24 hr at 4°C, a significantly reduced amount of functional cells covering bone surfaces was observed (27% ± 5%) but not of cells within the cartilage (79% ± 8%). In the applied experimental setup, bone cells were more affected by tissue culture at 37°C than cartilage cells. Even though chondrocytes appear to be more sensitive to 37°C than to 4°C, the substantially reduced amount of functional bone cells at 37°C warrants further investigation of whether a preincubation of osteochondral allografts at 37°C--prior to regular storage at 4°C--might result in an optimized osteochondral allograft with devitalized bone but viable cartilage.

Improved Preservation of Fresh Osteochondral Allografts for Clinical Use

“…Another factor reported to affect success of OCA procedures is the viability of the bone portion of the graft. 2,16 However, unlike the cartilage portion of the OCA, it is suggested that devitalization of the bone component results in improved graft incorporation and decreased failure rates. It is theorized that because bone is not an immunologically privileged tissue, host immune responses to viable bone can result in poor incorporation and eventual collapse of the graft.…”

“…To maintain chondrocyte viability in OCAs for clinically relevant time periods, researchers have applied tissue preservation, rather than storage, methods to this problem by using cell culture protocols for OCAs. [7][8][9][10][11][12][13][14][15][16][17][18] Use of various culture media preparations to preserve OCAs at 4°C has been reported to significantly improve chondrocyte viability compared with LRS. 7,14,17,19 These media preparations can be separated into those that include fetal bovine serum (FBS) 12,20,21 and those that do not.…”

“…Conversely, numerous studies have reported promising results with respect to chondrocyte viability when OCAs were preserved at 37°C, the standard temperature for in vitro cell and tissue culture, when compared with 4°C. 11,16,19,[35][36][37][38] OCAs preserved at 37°C have consistently had significantly higher chondrocyte viability at day 28 compared with those preserved at 4°C. 19,35,36 Importantly, these studies have also indicated that supplementation with FBS may not be required to maintain high levels of chondrocyte viability of the OCA preserved at 37°C tissue.…”

Cartilage storage at 4 °C with regular culture medium replacement benefits chondrocyte viability of osteochondral grafts in vitro

“…Regarding storage temperature, dispute exists between whether to store at body temperature (37 °C) or in a thermostat refrigerator (4 °C). Several studies report that ex vivo storage of articular cartilage is better at 37 °C compared with 4 °C (Bastian et al 2011; Bian et al 2010; Pallante et al 2009). However, the issue with graft storage at 37 °C is that microorganism growth can occur, which increases the infection risk and contributes to high storage costs (Stoker et al 2012).…”

Comparison of Techniques for Preimplantation Treatment of Osteochondral Allograft Bone

“…18,[23][24][25] The concentration process increases the nucleated cell concentration of the BMC by 2 to 40 times over that of the BMA. 18,25,26 Cells in BMC have the potential to become osteoblasts 18,27 and can respond to local stimuli to produce new bone and to recruit additional cells to stimulate the healing, integration, and remodeling processes requisite for optimal OCA incorporation. Additionally, BMC has been reported to contain many growth factors including platelet-derived growth factor (PDGF), transforming growth factor-β(TGF-β), and vascular endothelial growth factor (VEGF).…”