Construction of osteochondral-like tissue graft combining β-tricalcium phosphate block and scaffold-free centrifuged chondrocyte cell sheet

Abstract

BackgroundThe combination of a β-tricalcium phosphate (βTCP) block with a scaffold-free chondrocyte sheet formed by the centrifugation of chondrocytes in a well was investigated with the aim of constructing an osteochondral-like structure. MethodsHuman and porcine articular cartilage chondrocytes were respectively centrifuged in a 96-well plate or cell culture insert (0.32cm2) that was set in a 24-well plate, cultivated in the respective vessel for 3 weeks, and the cell sheets were harvested. In some cases, a cylindrical βTCP block (diameter 5 mm, height 3 mm) was placed on the sheet on days 1–7. The sheet size, cell number, and sulfated glycosaminoglycan accumulation were determined. ResultsThe use of a 96-well plate for not suspension but adhesion culture and the initial centrifugation of a well containing cells were crucial to obtaining a uniformly thick cell sheet. The glycosaminoglycan density of the harvested cell sheet was comparable to that of the pellet culture. An inoculum cell number of more than 31 × 105 cells tended to result in a curved cell sheet. Culture involving 18.6 × 105 cells and the 96-well plate for adhesion culture showed no curving of the cell sheet (thickness of 0.85 mm), and these were found to be the best of the culture conditions tested. The timing of the addition of a βTCP block to the cell sheet (1–7 days) markedly affected the balance between the thickness of cell sheet parts on and in the βTCP block. ConclusionCentrifugation and subsequent cultivation of chondrocytes (18.6 × 105 cells) in a 96-well plate for adhesion culture led to the production of a scaffold-free cartilage-like cell sheet with a thickness of 0.85mm. A combined osteochondral-like structure was produced by putting a βTCP block on the cell sheet. The thickness of the cell sheet on the βTCP block and the binding strength between the cell sheet and the βTCP block could be optimized by adjusting the inoculum cell number and timing of βTCP block addition.