Mesenchymal Stem Cell Secretome Effectiveness on Healing of Chronic Tendon Injury: Analysis of Procollagen Type I N- Terminal Peptide and Procollagen Type Iii N-terminal Peptide and Histopathology in Rat’s Tendon (Rattus Norvegicus)

Background Chronic tendon injuries, such as Achilles tendinopathy, are common and challenging to treat due to the limited regenerative capacity of tendon tissue. Using mesenchymal stem cell (MSC) secretome, which contains a rich array of growth factors, holds promise for enhancing tendon healing. This study aimed to evaluate the effectiveness of MSC secretome, derived from tendon-derived stem cells (TDSCs) and adipose-derived stem cells (ASCs), on the healing of chronic Achilles tendon injuries in a rat model, focusing on the levels of Procollagen Type I N-Terminal Peptide (PINP) and Procollagen Type III N-Terminal Peptide (PIIINP), and histopathological changes. Methods A chronic tendinopathy model was induced in 16 males of Rattus norvegicus via mechanical overloading and collagenase injection. Rats were divided into four groups: TDSC secretome, ASC secretome, combined TDSC + ASC secretome, and a control group. Secretomes were administered intratendinously. Tendon healing was assessed after four weeks using enzyme-linked immunosorbent assays (ELISA) to measure PINP and PIIINP levels and histopathological analysis to evaluate collagen deposition and tissue structure. Results PINP levels were significantly higher in the TDSC + ASC group compared to the control group (p = 0.004), indicating enhanced Type I collagen synthesis. However, no significant differences were observed in PIIINP levels between the groups. The histopathological analysis did not reveal significant structural differences in tendon healing among the groups, though increased collagen alignment was observed in the TDSC + ASC group. Conclusions The combined TDSC and ASC secretome promotes Type I collagen synthesis in chronic tendon injuries, but histological improvements were insignificant. Further studies are needed to confirm the long-term benefits of secretome therapy.