Complement factor D as a predictor of Achilles tendon healing and long‐term patient outcomes

Abstract

Dense connective tissue healing, such as tendon, is protracted leading to highly variable and unsatisfactory patient outcomes. Biomarkers prognostic of long‐term clinical outcomes is, however, unknown. The present study was designed to investigate the proteomic profile of healing, identify potential biomarkers, and assess their association with the patient's long‐term outcomes after ATR. Quantitative mass spectrometry analysis demonstrated 1423 proteins in healing and contralateral healthy Achilles tendons of 28 ATR patients. Comparing healing at 2 weeks and healthy protein profiles, we identified 821 overlapping, 390 upregulated, and 17 downregulated proteins. Upregulated proteins are related mainly to extracellular matrix organization and metabolism, while downregulated pathways were associated with exocytosis in immune modulation and thrombosis formation. Further proteomic profiling in relation to validated patient outcomes revealed the downregulated pro‐inflammatory complement factor D (CFD) as the most reliable predictive biomarker of successful tendon healing. Our finding showed a comprehensive proteomic landscape and bioinformatics on human connective tissue, indicating subtype‐specific and shared biological processes and proteins in healing and healthy Achilles tendons, as well as in tendons related to good and poor patient outcomes. Inflammatory protein CFD and serpin family B member 1 were finally identified as potential predictive biomarkers of effective healing outcomes when combined the proteomic profiles with a validated clinical database. Following the future elucidation of the mechanisms associated with the identified biomarkers as predictors of good outcomes, our findings could lead to improved prognostic accuracy and development of targeted treatments, thus improving the long‐term healing outcomes for all patients.

eEF2 improves dense connective tissue repair and healing outcome by regulating cellular death, autophagy, apoptosis, proliferation and migration

“…DCTs repair is a complex process in which the inflammatory phase of healing is successively replaced by proliferative healing processes and matrix deposition. Our recent finding based on the proliferative stage of healing (Chen et al, 2022) also detected an increased eEF2 expression in the healing tendons at two weeks post repair surgery. Interestingly, analysis of the MS-based quantitative proteomic data from the early proliferating healing phase; 2-weeks post-surgery, detected elevated levels of eEF2 in the healing compared to intact Achilles tendons (Figure 5a).…”

“…However, whether eEF2 plays a key role during the proliferation phase of tissue repair remains unclear. The identification of increased eEF2 levels also at 2-weeks post Achilles tendon surgery (Chen et al, 2022), suggests a role in the early proliferative healing phase as defined in earlier studies of Achilles tendon healing (Ackermann et al, 2013, Alim et al, 2016. Fibroblasts play a vital role during proliferation (Bainbridge, 2013, Tracy et al, 2016, Wong et al, 2007, Addis et al, 2020.…”

“…However, some aspects of these limitations can potentially be overcome by using recent technological developments in the field of mass spectrometry (MS)-based proteomics which have considerably improved the sensitivity, completeness and quantitative accuracy of this technique for investigating human diseases (Kim et al, 2014, Wilhelm et al, 2014). Our recent findings using MS to analyze the proteomic landscape of human tendon repair in patients with Achilles tendon rupture (ATR) with high quality and sensitivity (Chen et al, 2022) demonstrate the utility of such approaches.…”

eEF2 improves dense connective tissue repair and healing outcome by regulating cellular death, autophagy, apoptosis, proliferation and migration

“…However, whether eEF2 plays a key role during the proliferation phase of tissue repair remains unclear. The identi cation of increased eEF2 levels also at 2-weeks post Achilles tendon surgery [12], suggests a role in the early proliferative healing phase as de ned in earlier studies of Achilles tendon healing [16,53]. Fibroblasts play a vital role during proliferation [54][55][56][57].…”

“…However, some aspects of these limitations can potentially be overcome by using recent technological developments in the eld of mass spectrometry (MS)-based proteomics which have considerably improved the sensitivity, completeness and quantitative accuracy of this technique for investigating human diseases [10,11]. Our recent ndings using MS to analyze the proteomic landscape of human tendon repair in patients with Achilles tendon rupture (ATR) with high quality and sensitivity [12] demonstrate the utility of such approaches.…”