P002 - Characterizing Native and Allograft ACL Tissues: Transcriptional Role and Novel Histologic Validation of SPARC and PRELP
Abstract
Purpose
Anterior cruciate ligament (ACL) injuries are common and of high relevance given their significant effects on patient function, quality of life, and posttraumatic cartilage damage and arthritis. To date, investigators have reported on the expression of genes classically associated with tendon and ligament reconstruction but have not systematically characterized allografts for ideal candidate gene selection in the clinical and research settings.
Methods and Materials
Next generation RNA sequencing was performed on whole semitendinosus autografts from New Zealand White rabbits and subsequently analyzed using gene enrichment and protein-protein interaction network analysis. Protein expression based on mRNA data was validated by immunohistochemistry, which was performed on clinical grade semitendinosus human hamstring and patellar tendon allografts, the two most common ACL grafts, as well as fresh-harvested ACLs obtained during total knee arthroplasty.
Results
Analysis of 23,398 genes revealed that over 14,000 genes were expressed above the minimal threshold. Gene ontology analysis showed that the extracellular matrix (ECM) proteins Decorin (DCN), Secreted Protein Acidic and Cysteine Rich (SPARC; osteonectin), Collagen type 1 (COL1A1 and COL1A2), and Proline and Arginine Rich End Leucine Rich Repeat Protein (PRELP) are the highest expressed tendon-related genes in rabbit allograft tissue. Clinical grade human hamstring and patellar tendon allograft demonstrated strong, uniform immunohistochemical staining for both SPARC and PRELP proteins, supporting the structural roles of these proteins in both clinically relevant rabbit surgical models and human tissues.
Conclusion
These results reflect the association between collagenous (COL1A1 and COL1A2) and non-collagenous ECM proteins (DCN) in tendon tissues. Identification of SPARC and PRELP as highly expressed tendon-related genes permits consideration of these two proteins as novel biomarkers for tendon health and repair.
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