Epigallocatechin-3-Gallate (EGCG)-Loaded Hyaluronic Acid Hydrogel Seems to Be Effective in a Rat Model of Collagenase-Induced Achilles Tendinopathy.

Tendon injuries account for 45% of musculoskeletal injuries. However, research on the occurrence and pathogenesis of tendinopathy is insufficient, and there is still much debate regarding treatment methods. It is important to understand the molecular mechanisms of oxidative stress and inflammatory responses because oxidative stress in tendon tissue is induced by various factors, including inflammatory cytokines, drug exposure, and metabolic abnormalities. In this study, 28 rats were divided into four groups (7 rats assigned to each group): control group (CON), collagenase injection group (CL), collagenase injection and hyaluronic acid injection group (CL + HA), and collagenase injection and EGCG-loaded hyaluronic acid injection group (CL + HA + EGCG). Seven weeks after the start of the study, all rats underwent histochemical analysis, immunofluorescence staining, and Western blot. The results showed increased inflammatory cells, disarray of collagen matrix, and degradation of the collagen matrix in the CL group. However, in the EGCG-treated group, there was a significant increase in type I collagen expression and a significant decrease in type III collagen expression, compared to the CL group. Additionally, there was an increase in the expression of antioxidant markers SOD (Superoxide Dismutase) and CAT (Catalase), tenogenic markers COLL-1 (collagen type I), and SCX (Scleraxis), and a downregulated expression of apoptosis markers cas-3 and cas-7. Our findings suggest that EGCG-loaded hyaluronic acid hydrogel exhibits potential in preventing tendon damage and promoting the regeneration process in a rat model of Achilles tendinopathy. The insights gained from our histological and molecular investigations highlight the future potential for testing novel tendinopathy treatments in human subjects.