OPTIMIZING WOUNDED ARTICULAR CARTILAGE FOR IMPROVED CARTILAGE INTEGRATION: EVALUATING CHONDROPROTECTIVE MEASURES FOR MINIMIZING IN SITU CHONDROCYTE DEATH

Abstract

AbstractObjectiveThe preparation of host degenerate cartilage for repair typically requires cutting and/or scraping to remove the damaged tissue. This can lead to mechanical injury and cartilage cell (chondrocytes) death, potentially limiting the integration of repair material. This study evaluated cell death at the site of cutting injury and determined whether raising the osmotic pressure (hyper-osmolarity) prior to injury could be chondroprotective.MethodsEx vivo human femoral head cartilage was obtained from 13 patients (5 males and 8 females: 71.8 years old) with Ethical Permission and Patient consent. Cartilage wells were created using 3 or 5mm biopsy punches. Cell death at the wounded edge of the host cartilage and the edge of the extracted explants were assessed by quantifying the percentage of cell death (PCD) and measuring the width of the cell death zone at identified regions of interest (ROI) using the confocal laser scanning microscopy and image analysis software. To assess the chondroprotective effect of hyper-osmolarity, cartilage specimens were incubated in 340 or 600mOsm media, five minutes prior to injury to allow the chondrocytes to respond to the altered osmolarity. Wounded cartilage explants and cartilage wells were then cultured for a further 150 minutes following injury.ResultsIn 340mOsm media, the PCD around the 3mm cartilage wells was significantly less compared to the corresponding explants (20.05±10.24% vs 35.25±4.86%; P=0.0003). When using the 5mm biopsy punch, the PCD at the wound edges was significantly lower when compared to the 3mm cartilage wells (13.33±7.80% vs 20.05±10.24%; P=0.0121) at the same osmolarity. The width of the cell death zone for the well edges for both 3 and 5mm punches was significantly narrower when compared to their corresponding harvested cartilage explants in 340mOsm media (P<0.0001; P=0.0218, respectively). Exposing cartilage to raised osmolarity (600mOsm) prior to injury significantly reduced the PCD for cartilage wells produced by the 3mm biopsy punches (from 20.05±10.24% to 12.24±6.00%; P=0.0025). In addition, the zone of cell death was marginally reduced at the edges of the 5mm cartilage wells (19.25±15.78mm to 12.72±9.09mm; P=0.0499).ConclusionsThe choice of biopsy punch and the osmolarity of the incubation medium prior to cartilage injury markedly affected the extent of chondrocyte death both at the edges of the cartilage wells and the explants. The smaller biopsy punch caused more chondrocyte death in the native cartilage wells compared to the larger punch, but this could be compensated for by the chondroprotective effect of raising the osmotic pressure. In general, there was less cell death at the wounded edges of the cartilage wells, compared to the explants. These results suggest that there is scope for further optimising the cutting implements used to create the cartilage wells and protecting chondrocytes by hyper-osmolarity in order to minimize cell death at cut edges and potentially enhance integration between cartilage repair material and host cartilage.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.