Potential utility of cell sheets derived from the anterior cruciate ligament and synovium fabricated in temperature-responsive culture dishes.

Development of tissue-engineered materials to treat anterior cruciate ligament (ACL) injury has been limited by the lack of phenotypic markers. We investigated the feasibility of inducing ACL regeneration using cell sheet technology based on the expression of tenomodulin (TNMD) as an early phenotypic marker of ligaments. ACL remnants, the synovium surrounding cruciate ligaments (SCL), the synovium surrounding the infrapatellar fat pads (SIF), and subcutaneous fat tissue (SCF) were obtained from patients undergoing ACL reconstruction or total knee arthroplasty. ACL cell sheets and SCL-derived cell sheets were fabricated successfully A three-dimensional bioengineered ACL was generated by combining triple-layered ACL cell sheets with a bioabsorbable mesh composite. Immunohistochemical examination showed that TNMD was expressed in human ACL fibers, triple-layered ACL cell sheets, ACL remnants, SCL, and SIF, but not in SCF. Real-time PCR showed that TNMD mRNA was expressed at substantially higher levels in the ACL, SCL, and SIF than in the SCF. These results suggest that TNMD is a specific marker of the human ACL and that ACL sheets have a phenotype similar to that of the ACL. The greater expression of TNMD in the SCL- and SIF- suggests that the synovium is a potential cell source for ACL regeneration.