A composite PET-matrix patch enhances tendon regeneration and tendon-to-bone integration for bridging repair of the chronic massive rotator cuff tears in a rabbit model

In recent years, bridging repair has emerged as an effective approach for the treatment of massive rotator cuff tears (MRCTs). The objective of this study was to develop a composite patch that combines superior mechanical strength and biocompatibility and evaluate its potential for enhancing the outcomes of bridging repair for MRCTs. The composite patch, referred to as the PET-matrix patch (PM), was fabricated by immersing a plain-woven PET patch in decellularized matrix gel and utilizing the freeze-drying technique. The results demonstrated that the PM has reliable mechanical properties, with a maximum failure load of up to 480 N. The decellularized matrix sponge (DMS), present on the surface of the PM, displayed a loose and porous structure, with an average pore size of 62.51 mu m and a porosity of 95.43%. In vitro experiments showed significant elongation of tenocytes on the DMS, with cells spanning across multiple pores and extending multiple protrusions as observed on SEM images. In contrast, tenocytes on the PET patch appeared smaller in size and lacked significant elongation. Additionally, the DMS facilitated the proliferation, migration and differentiation of tenocytes. In a rabbit model of chronic MRCTs, the PM group showed superior outcomes compared to the PET group at 4, 8 and 12 weeks after bridging repair. The PM group displayed significantly higher tendon maturing score, larger collagen diameter in the regenerated tendon and improved tendon-to-bone healing scores compared to the PET group (P < 0.05). Moreover, the maximum failure load of the tendon-bone complex in the PM group was significantly higher than that in the PET group (P < 0.05). In summary, the PM possesses reliable mechanical properties and excellent cytocompatibility, which can significantly improve the outcomes of bridging repair for chronic MRCTs in rabbits. Therefore, it holds great potential for clinical applications.