UC Davis

Anterior cruciate ligament (ACL) injuries are prevalent among athletes and the general public, resulting in socioeconomic stress, loss of performance, and decreased quality of life. Currently, surgical repair is the gold standard. However, these interventions are expensive and associated with limited improvement in quality of life due to the increased risk of post-traumatic osteoarthritis (PTOA). PTOA is due in part to the lack of recapitulation of the enthesis between the ligament and bone. Therefore, there is a need to develop alternative ways to improve ligament-to-bone grafting and promote the development of a functional enthesis. Tissue engineering techniques have emerged as one way to generate these tissues. Current tissue-engineered ligament grafts fail to mature completely, and usually fail at the ligament-bone interface. The purpose of this study was to use a two-step modular approach to promote enthesis formation and thereby improve the mechanical integrity of engineered ligaments. First, an enthesis construct was formed around individual brushite anchors. Second, a linear bone-to-bone ligament was formed using two enthesis anchors. Control constructs and constructs that controlled for the increased cell density (400k) were formed in parallel around two bare brushite anchors. Neither interface strength (MTL), ultimate tensile strength, collagen percentage, nor modulus was significantly different between the groups. Although, we observed a trend in interface strength, collagen content, and failure at the midsubstance with the modular constructs. Tissue infiltration at the anchor was observed, suggesting the initial formation of a tidemark. We also observed the presence of collagen X near the anchor. Although, it was less intense in the modular group.