Differences in expression of Mohawk transcription factors and collagen in anterior cruciate ligament grafts between two remodeling outcomes under arthroscopy

Abstract

Objective To investigate the differences in expression of Mohawk (MKX) transcription factors and collagen of types Ⅰ and Ⅲ in anterior cruciate ligament (ACL) grafts between 2 remodeling outcomes under arthroscopy. Methods Enrolled for this study were 17 patients who had undergone arthroscopic single-bundle ACL reconstruction with autogenous hamstring tendons and secondary arthroscopic exploration 48 to 131 months (average, 83.1 months) after removal of tibial internal fixator at Department of Sports Medicine, The First Affiliated Hospital to Shenzhen University from March 2017 to December 2017. They were divided into a good remodeling group (11 cases) and a fair remodeling group (6 cases) according to the graft quality under arthroscopy (synovial and vascular coverage, and apparent tension, thickness and retear of the grafts). During the secondary arthroscopic procedures, biopsy of the central ACL grafts was performed. Moreover, normal ACL tissues were harvested from 8 contemporary controls of <60 years old who underwent total knee replacement. Immunohistochemical assay and quantificational real-time polymerase chain reaction were conducted to detect the expression of transcription factors and collagen of types Ⅰ and Ⅲ in all the samples. Results In the samples from good remodeling and control groups, there were abundant well-arranged collagen fibers of types Ⅰ and Ⅲ and MKX-positive cells; in the fair remolding group, the collagen fibers of types Ⅰ and Ⅲ and MKX-positive cells were much decreased in number and the fibers were not well arranged. The former 2 groups scored in immunohistochemical assay significantly higher than the latter one (P<0.05). qRT-PCR showed that the expression levels of MKX gene (0.44±0.30), COL1A1 gene (0.52±0.27) and COL3A1 gene (0.60±0.22) in the fair remolding group were significantly lower than in the control group (1.00±0.00, 1.00±0.00 and 1.00±0.00) and than in the good remolding group (0.97±0.67, 0.99±0.38 and 1.00±0.35) (P<0.05). Conclusion Good remodeling ACL grafts with histological maturation under arthroscopy are more similar to normal ACL than fair remodeling ACL grafts in expression of MKX transcription factors and collagen of types Ⅰ and Ⅲ. Key words: Anterior cruciate ligament; Transplantation, autologous; Ligaments, articular; Transcription factors; Collagen