In Vivo Evaluation of a Bi-Phasic Nanofiber-Based Scaffold for Integrative Rotator Cuff Repair

INTRODUCTION: Over 300,000 rotator cuff repair surgeries are performed annually[1]. Injuries to the rotator cuff often occur at the tendon-to-bone insertion[2], thus tendon integration is critical for long term stability and functionality of clinical repair. The native tendon-tobone junction consists of a continuous transition from the tendon proper to non-calcified and calcified fibrocartilage, and then to bone[3-5]. This controlled matrix heterogeneity, however, is not regenerated following rotator cuff repair; thus significant demand exists for integrative grafting systems that enable functional tendon-bone healing. To promote biological fixation, we have developed a biomimetic biphasic scaffold with contiguous non-mineralized (Phase A) and mineralized (Phase B) regions that are designed to facilitate the regeneration of the tendon-bone insertion. Specifically, Phase A is composed of nanofibers of poly(lactide-co-glycolide) (PLGA) and Phase B consists of composite nanofibers of PLGA and hydroxyapatite (HA) nanoparticles (PLGA-HA). The objectives of this study are twofold: 1) to evaluate the formation of non-mineralized and mineralized fibrocartilage on the biphasic scaffold using a subcutaneous rat model, and 2) to determine the osteointegration strength of the mineralized region (Phase B) of the biphasic scaffold. It is hypothesized that Phase B of the biphasic scaffold will integrate with bone and distinct yet continuous regions of non-calcified and calcified interface-like tissue will form on the biphasic scaffold in vivo.