iTRAQ-based proteomics reveals potential markers and treatment pathways for acute Achilles tendon rupture.

BACKGROUND: Due to its limited blood supply and irregular mechanical loading, the Achilles tendon is the most frequently ruptured tendon. Despite the rising incidence of acute Achilles tendon rupture (AATR), the optimal treatment remains controversial. Missed diagnoses and delayed treatments lead to poor outcomes and limited treatment options. This study aimed to identify potential biomarkers for diagnosing and developing therapies for AATR. METHODS: We employed the coupled isobaric tag for relative and absolute quantitation-liquid chromatography-electrospray ionization-tandem mass spectrometry approach to investigate protein expression in tissues from AATR patients. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted to identify differentially expressed proteins (DEPs) between AATR patients and healthy individuals. A protein-protein interaction (PPI) network of DEPs was constructed using the Search Tool for the Retrieval of Interacting Genes. The screened hub genes were selectively verified by immunohistochemical staining. RESULTS: We identified 410 DEPs between AATR patients and controls. The DEPs were significantly enriched in GO terms such as the extracellular region, extracellular region part, and defense response, as well as KEGG pathways, including complement and coagulation cascades, focal adhesion, and regulation of actin cytoskeleton. The main hub nodes in the PPI network comprised fibronectin 1 (FN1), major histocompatibility complex, class I, B (HLA-B), filamin A (FLNA), heat shock 27-kDa protein 1 (HSPB1), heat shock protein family A member 5 (HSPA5), apolipoprotein A4 (APOA4), and myosin IC (MYO1C). Although APOA4 and collagens I, II, and III were detectable in healthy tendons, immunohistochemical staining confirmed higher expression of these proteins in the acutely ruptured Achilles tendon. CONCLUSIONS: Our findings lay a foundation for further molecular studies of AATR. Inflammation and age-related degeneration may contribute to the pathogenesis of AATR. Moreover, the identified DEPs could be potential biomarkers for AATR diagnosis and treatment.

Active exercise promotes Achilles tendon healing and is accompanied by the upregulation of collapsin response mediator protein­2 in rats.

Collapsin response mediator protein-2 (CRMP-2) is involved in neurite elongation and regeneration; however, its role in wound healing remains to be elucidated. The present study aimed to investigate the effects of active mobilization treatment on Achilles tendon healing and to determine the role of CRMP­2 in the healing process. Sprague Dawley rats were subjected to Achilles tendon injury, which was verified by hematoxylin and eosin staining and scanning electronic microscopy. Immobilization induced the disruption of collagen fibril arrangement and promoted collagen fibril damage. The average collagen fibril perimeter in the active mobilization group was significantly increased compared with in the immobilization group (125.6±0.8 nm vs. 119.9±1.7 nm; P<0.05). In addition, immunohistological analysis revealed that CRMP­2 expression was significantly upregulated, particularly in the ruptured site of Achilles tendon tissues derived from animals in the mobilization group compared with the immobilization group (0.32±0.00 vs. 0.08±0.00; P<0.05). The increased CRMP­2 levels were also confirmed by western blotting (active mobilization group, 0.71±0.03; immobilization group, 0.49±0.01 nm; P<0.05). These results indicated that active mobilization may promote Achilles tendon healing via upregulation of CRMP­2 protein expression.

Early Ankle Mobilization Promotes Healing in a Rabbit Model of Achilles Tendon Rupture.

The use of early mobilization of the ankle joint without orthosis in the treatment of Achilles tendon rupture has been advocated as the optimal management. The goal of this study was to compare outcomes in a postoperative rabbit model of Achilles tendon rupture between early mobilization and immobilized animals using a differential proteomics approach. In total, 135 rabbits were randomized into the control group (n=15), the postoperative cast immobilization (PCI) group (n=60), and the early mobilization (EM) group (n=60). A rupture of the Achilles tendon was created in each animal model and repaired microsurgically, and tendon samples were removed at 3, 7, 14, and 21 days postoperatively. Proteins were separated using 2-dimensional polyacrylamide gel electrophoresis and identified using peptide mass fingerprinting, tandem mass spectrometry, NCBI database searches, and bioinformatics analyses. A series of differentially expressed proteins were identified between groups, some of which may play an important role in Achilles tendon healing. Notable candidate proteins that were upregulated in the EM group were identified, such as CRMP-2, galactokinase 1, tropomyosin-4, and transthyretin. The healing of ruptured Achilles tendons appears to be affected at the level of protein expression with the use of early mobilization. The classic postoperative treatment of Achilles tendon rupture with an orthosis ignored the self-protecting instinct of humans. With a novel operative technique, the repaired tendon can persist the load that comes from traction in knee and ankle joint functional movement. In addition, kinesitherapy provided an excellent experimental outcome via a mechanobiological mechanism.