The use of ultrasonication to aid recellularization of acellular natural tissue scaffolds for use in anterior cruciate ligament reconstruction

Tissue engineering offers a promising solution to the replacement of anterior cruciate ligament. A decellularized porcine patella tendon scaffold was produced by immersing whole tissues sequentially in hypotonic buffer, 0.1% (w/v) sodium dodecyl sulfate (SDS) in hypotonic buffer, and nuclease solution prior to sterilization with 0.1% (w/v) peracetic acid. Initial studies revealed that primary human tenocytes would attach to, but failed to penetrate into, the decellularized scaffold. A novel use of ultrasonication was therefore developed to allow extrinsic cells to migrate into the acellular scaffold. Various intensities of ultrasonication were tested in order to produce a microscopically more open porous matrix without damaging the overall architecture of the scaffold. Ultrasonication treatment with the intensity of 360 W and a pulse time of 1 s for a total of 1 min was found to be the optimal treatment. This process did not have a significant effect upon the biochemical constituents (collagen, glycosaminoglycans), nor did it denature the collagen. Moreover, the acellular sonicated scaffold retained the essential biomechanical characteristics of the native tissue. Primary human tenocytes penetrated into the center of whole acellular sonicated scaffolds over a 3-week period in static culture. The viability of the cells in the center of the scaffold (depth of circa 2.5 mm) was, however, compromised. To circumvent the problem of nutrient limitation, acellular sonicated scaffolds were split into fascicular scaffolds (500 mum thick). Cells seeded onto the fascicular scaffolds penetrated throughout the scaffold and remained viable after 3 weeks of culture. This study has shown that an acellular biocompatible tendon scaffold can be produced using 0.1% (w/v) SDS and that ultrasonication can provide a novel method to enhance the recellularization of decellularized natural tissues.