Functional decellularized fibrocartilaginous matrix graft for rotator cuff enthesis regeneration: A novel technique to avoid in-vitro loading of cells

Rapid and functional enthesis regeneration after rotator cuff tear (RCT) remains a challenge in clinic. Current tissue-engineering strategies for solving this challenge are focused on developing grafts with the mode of in-vitro loading cells on a scaffold. However, this mode is complicated and time-inefficient, moreover the preservation of this graft outside a cell incubator is highly inconvenient, thus limiting their clinical application. Developing a cell-free graft with chemotaxis to recruit postoperative injected cells may be a promising approach to solve these problems. Herein, we prepared a recombinant SDF-1 alpha (termed as C-SDF-1 alpha) capable of binding collagen and chemotaxis, which were then tethered on the collagen fibers of book-shaped decellularized fibrocartilage matrix (BDFM) to fabricate this cell-free graft (C-SDF-1 alpha/BDFM). This C-SDF-1 alpha/BDFM is noncytotoxicity and low-immunogenicity, allows synovium-derived mesenchymal stem cells (SMSCs) attachment and proliferation, and shows superior chondrogenic inducibility. More importantly, C-SDF-1 alpha/BDFM released the tethered SDF-1 alpha with a sustained release profile in-vitro and in-vivo, thus steadily recruiting chemokine (C-X-C motif) receptor 4 positive (CXCR4(+)) cells. Rats with RCT were repaired acutely with C-SDF-1 alpha/BDFM together with postoperative CXCR4(+)SMSCs injection (C-SDF-1 alpha/BDFM + CXCR4(+)SMSCs), BDFM in-vitro pre-loaded CXCR4(+)SMSCs (BDFM/CXCR4(+)SMSCs), or direct suture only (CTL). At postoperative 14-day, compared with BDFM/ CXCR4(+)SMSCs, C-SDF-1 alpha/BDFM + CXCR4(+)SMSCs showed a little more CXCR4(+)SMSCs at the healing site. At postoperative week 4 or 8, rats treated with C-SDF-1 alpha/BDFM + CXCR4(+)SMSCs presented a similar RC healing quality as BDFM/CXCR4(+)SMSCs, both of which were significantly better than the Cu_ Collectively, compared with conventional BDFM/CXCR4(+)SMSCs, C-SDF-1 alpha/BDFM, as a cell-free graft with chemotaxis, could recruit postoperative injected CXCR4(+) cells into the healing site to participating RC healing, thus avoiding the complex process of in-vitro loading cells on a scaffold and necessitating immense care for the graft outside cell incubator, making it very convenient for clinical application.