Abstract 34

Autologous Tenocyte Implantation for Massive Rotator Cuff Defect: Histological Assessment in the Rabbit

¹Craig Willers, ¹Jimin Chen, ^1,2Allan Wang, ¹Ming H. Zheng

>1Department of Orthopaedics Surgery, School of Surgery and Pathology, University of Western Australia, Nedlands, WA 6009, Australia

>2Australia Orthopaedics Association 140 Mounts Bay Road, West Perth, WA, 6005, Australia

Introduction: Large or recurrent rotator cuff tendon tears are difficult to treat effectively. Collagen bioscaffolds have recently become available to reinforce tendon repair. This study compares the suitability of two collagen bioscaffolds for autologous tenocyte implantation, and evaluates the reparative response induced by these biomaterial constructs in a rabbit model.

Methods: Tenocytes were isolated from rabbit patellar tendon, cultured, and seeded onto either Restore SIS or ACI-Maix collagen membrane. Scanning electron microscopy was used to examine tenocyte integration and growth within the bioscaffold over time. Massive rotator cuff defect was created in fifty NZW rabbits and treated by either: (A) suture of autologous cuff tendon (control), (B) ACI-Maix implantation, (C) Autologous tenocyte-seeded ACI-Maix implantation, (D) SIS implantation, (E) Autologous tenocyte-seeded SIS implantation. Gross and histological evaluation was performed at four and eight weeks postoperatively. Results: Scanning electron microscopy of the ACI-Maix membrane showed the loose organisation of collagen fibres of its rough side, a feature conducive to cell adhesion and integration. Furthermore, one, three, and five day sequential analysis after seeding showed progressive tenocyte integration into the membrane and matrix neosynthesis. Scanning electron microscopy of the SIS membrane exhibited its relatively smooth surface of highly compacted collagen fibres. Sequential analysis of the SIS membrane after seeding showed monolayer cell integration with progressive proliferation and observed matrix neosynthesis. At four weeks, all ACI-Maix and SIS membrane reparative outcomes were characterized by partially absorbed membrane, subsequent lymphocytic inflammatory response, and immature bone trough remodelling. By eight weeks, inflammation had subsided and the regenerating tendon illustrated improved remodelling by histology. Autologous tenocyte implantation with both membranes improved reparative tendon histology and grade at eight weeks in comparison to membrane-only implants, and was histologically equivalent to the control group. All fifty rabbits regained normal gait two weeks postoperatively, and no tendon rupture occurred in any rabbit groups.

Conclusion: Autologous tenocytes seeded onto both ACI-Maix and SIS membrane show cell behaviour suitable for cell-based therapy. Although both implants showed inflammatory response in the rabbit initially, resorption occurs with time. The bioscaffold-induced healing response of rotator cuff tear is improved by the addition of autologous tenocytes in the rabbit. We therefore suggest autologous tenocyte implantation may be a clinically useful alternative treatment for massive rotator cuff tears.

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