Expression of TGF-β1 and VEGF in patients with Achilles tendon rupture and the clinical efficacy

Systematic Review of Relevant Biomarkers for Human Connective Tissue Repair and Healing Outcome: Implications for Understanding Healing Processes and Design of Healing Interventions

Objective: The healing process following connective tissue (CT) injuries is complex, resulting in variable and often suboptimal outcomes. Patients undergoing CT repair frequently experience healing failures, compromised function, and chronic degenerative diseases. The identification of biomarkers to guide improved clinical outcomes after CT injuries remains an emerging but promising field. [Figure: see text] [Figure: see text] Design: Systematic review. Data sources: Databases, including PubMed, MEDLINE Ovid, Web of Science, and Google Scholar, were searched up to August 2024. Eligibility criteria: To achieve the research objective, randomized control trials, cohort studies, and case-control studies on biomarkers associated with CT repair and healing outcomes were selected. The present analysis was confined to clinical and preclinical models, excluding imaging studies. The entire process of this systematic review adhered strictly to the guidelines outlined in the Preferred Reporting Items for Systematic Review and Meta-Analyses protocol checklist. Results: A total of 1,815 studies on biomarkers of CT repair were initially identified, with 75 studies meeting eligibility criteria and 55 passing quality assessments. For biomarkers associated with CT healing outcomes, 281 studies were considered, with 30 studies meeting eligibility criteria and 24 passing quality assessments. Twenty-one overlapping studies investigated the effects of biomarkers on both CT repair and healing outcomes. Specific biomarkers identified, and ranked from highest to lowest quality, include complement factor D, eukaryotic elongation factor-2, procollagen type I N-terminal propetide, procollagen type III N-terminal propetide, lactate, pyruvate, platelet-derived growth factor-BB, tissue inhibitor of metalloproteinase-3 (TIMP-3), cysteine-rich protein-1, plastin-3, periostin, protein S100-A11, vimentin, matrix metalloproteinases (MMP-2, MMP-7, and MMP-9), hepatocyte growth factor, interferon-γ, interleukins (IL-6, IL-8, and IL-10), MMP-1, MMP-3, tumor necrosis factor-α, fibroblast growth factor-2, IL-1α, chondroitin-6-sulfate, inter-alpha-trypsin inhibitor heavy chain-4, transforming growth factor-beta 1, vascular endothelial growth factor, C-C chemokine receptor 7, C-C chemokine ligand 19, IL-1β, IL-1Ra, IL-12p40, granulocyte-macrophage colony-stimulating factor (GM-CSF), and TIMP-1. Conclusions: All of the 37 identified potential biomarkers demonstrated regulatory effects on CT repair and mediated healing outcomes. Notably, the identified biomarkers from human studies can potentially play an essential role in the development of targeted treatment protocols to counteract compromised healing and can also serve as predictors for detecting CT healing processes and long-term outcomes.

Recent developments in Achilles tendon risk-analyzing rupture factors for enhanced injury prevention and clinical guidance: Current implications of regenerative medicine

Background

In recent years, many countries have actively implemented programs and strategies to promote physical education and sports. Despite these efforts, the increase in physical activity has been accompanied by a significant rise in muscle and tendon-ligament injuries, with Achilles tendon rupture being the most prevalent, accounting for 47 % of such injuries. This review aims to summarize all significant factors determining the predisposition of the Achilles tendon to rupture, to develop effective personalized prevention measures.

Objective

To identify and evaluate the risk factors contributing to Achilles tendon rupture and to develop strategies for personalized prevention.

Methods

This review utilized data from several databases, including Elsevier, Global Health, PubMed-NCBI, Embase, Medline, Scopus, ResearchGate, RSCI, Cochrane Library, Google Scholar, eLibrary.ru, and CyberLeninka. Both non-modifiable and modifiable risk factors for Achilles tendon injuries and ruptures were analyzed.

Results

The analysis identified several non-modifiable risk factors, such as genetic predisposition, anatomical and functional features of the Achilles tendon, sex, and age. These factors should be considered when selecting sports activities and designing training programs. Modifiable risk factors included imbalanced nutrition, improper exercise regimens, and inadequate monitoring of Achilles tendon conditions in athletes. Early treatment of musculoskeletal injuries, Achilles tendon diseases, foot deformities, and metabolic disorders is crucial. Long-term drug use and its risk assessment were also highlighted as important considerations. Furthermore, recent clinical advancements in both conventional and surgical methods to treat Achilles tendon injuries were described. The efficacy of these therapies in enhancing functional outcomes in individuals with Achilles injuries was compared. Advancements in cell-based and scaffold-based therapies aimed at enhancing cell regeneration and repairing Achilles injuries were also discussed.

Discussion

The combination of several established factors significantly increases the risk of Achilles tendon rupture. Addressing these factors through personalized prevention strategies can effectively reduce the incidence of these injuries. Proper nutrition, regular monitoring, timely treatment, and the correction of metabolic disorders are essential components of a comprehensive prevention plan.

Conclusion

Early identification of Achilles tendon risk factors allows for the timely development of effective personalized prevention strategies. These measures can contribute significantly to public health preservation by reducing the incidence of Achilles tendon ruptures associated with physical activity and sports. Continued research and clinical advancements in treatment methods will further enhance the ability to prevent and manage Achilles tendon injuries.

The translational potential of this article

This study identifies key modifiable and non-modifiable risk factors for Achilles tendon injuries, paving the way for personalized prevention strategies. Emphasizing nutrition, exercise, and early treatment of musculoskeletal issues, along with advancements in cell-based therapies, offers promising avenues for improving recovery and outcomes. These findings can guide clinical practices in prevention and rehabilitation, ultimately reducing Achilles injuries and enhancing public health.

Current progress in growth factors and extracellular vesicles in tendon healing

Tendon injury healing is a complex process that involves the participation of a significant number of molecules and cells, including growth factors molecules in a key role. Numerous studies have demonstrated the function of growth factors in tendon healing, and the recent emergence of EV has also provided a new visual field for promoting tendon healing. This review examines the tendon structure, growth, and development, as well as the physiological process of its healing after injury. The review assesses the role of six substances in tendon healing: insulin-like growth factor-I (IGF-I), transforming growth factor β (TGFβ), vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and EV. Different growth factors are active at various stages of healing and exhibit separate physiological activities. IGF-1 is expressed immediately after injury and stimulates the mitosis of various cells while suppressing the response to inflammation. VEGF, which is also active immediately after injury, accelerates local metabolism by promoting vascular network formation and positively impacts the activities of other growth factors. However, VEGF's protracted action could be harmful to tendon healing. PDGF, the earliest discovered cytokine to influence tendon healing, has a powerful cell chemotaxis and promotes cell proliferation, but it can equally accelerate the response to inflammation and relieve local adhesions. Also useful for relieving tendon adhesion is TGF- β, which is active almost during the entire phase of tendon healing. As a powerful active substance, in addition to its participation in the field of cardiovascular and cerebrovascular vessels, tumour and chronic wounds, TGF- β reportedly plays a role in promoting cell proliferation, activating growth factors, and inhibiting inflammatory response during tendon healing.

Growth factors in the treatment of Achilles tendon injury

Achilles tendon (AT) injury is one of the most common tendon injuries, especially in athletes, the elderly, and working-age people. In AT injury, the biomechanical properties of the tendon are severely affected, leading to abnormal function. In recent years, many efforts have been underway to develop effective treatments for AT injuries to enable patients to return to sports faster. For instance, several new techniques for tissue-engineered biological augmentation for tendon healing, growth factors (GFs), gene therapy, and mesenchymal stem cells were introduced. Increasing evidence has suggested that GFs can reduce inflammation, promote extracellular matrix production, and accelerate AT repair. In this review, we highlighted some recent investigations regarding the role of GFs, such as transforming GF-β(TGF-β), bone morphogenetic proteins (BMP), fibroblast GF (FGF), vascular endothelial GF (VEGF), platelet-derived GF (PDGF), and insulin-like GF (IGF), in tendon healing. In addition, we summarized the clinical trials and animal experiments on the efficacy of GFs in AT repair. We also highlighted the advantages and disadvantages of the different isoforms of TGF-β and BMPs, including GFs combined with stem cells, scaffolds, or other GFs. The strategies discussed in this review are currently in the early stages of development. It is noteworthy that although these emerging technologies may potentially develop into substantial clinical treatment options for AT injury, definitive conclusions on the use of these techniques for routine management of tendon ailments could not be drawn due to the lack of data.

Biological and Mechanical Factors and Epigenetic Regulation Involved in Tendon Healing

Tendons are an important part of the musculoskeletal system. Connecting muscles to bones, tendons convert force into movement. Tendon injury can be acute or chronic. Noticeably, tendon healing requires a long time span and includes inflammation, proliferation, and remodeling processes. The mismatch between endogenous and exogenous healing may lead to adhesion causing further negative effects. Management of tendon injuries and complications such as subsequent adhesion formation are still challenges for clinicians. Due to numerous factors, tendon healing is a complex process. This review introduces the role of various biological and mechanical factors and epigenetic regulation processes involved in tendon healing.

The Role of Vascular Endothelial Growth Factor in Tendon Healing

Angiogenesis is crucial to facilitate tendon healing, such as delivering oxygen and nutrients, removing waste products, and controlling immune responses. Vascular endothelial growth factor (VEGF) is one of the most vital angiogenic factors that regulate blood vessel formation in tendon healing. Recently, biological therapies, including the application of exogenous VEGF, have been attracting increasing attention. However, at present, the effect of the application of exogenous VEGF in tendon healing is controversial, as the role of endogenous VEGF in tendons has also not been fully elucidated. This article will summarize the role of both endogenous and exogenous VEGF in tendon healing and discuss possible reasons for the controversy. The present review shows that tendon repair is facilitated only by proper angiogenesis and VEGF at the early stage, whereas the persistent high VEGF expression and prolonged presence of blood vessels may impair tendon repair at a later stage.

Gait analysis combined with the expression of TGF-β1, TGF-β3 and CREB during Achilles tendon healing in rat

PURPOSE

To observe the changes of gait behavior and the expression of wound healing factors of transforming growth factor-β1 (TGF-β1), TGF-β3 and cAMP response element binding protein-1 (CREB-1) during the healing of Achilles tendon in a rat model, and to investigate whether gait analysis can be used to evaluate the tendon healing.

METHODS

Achilles tendon of 40 healthy male Sprague-Dawley rats were transected and sutured to establish the Achilles tendon injury (ATI) model. They were randomly divided into 4 groups based on the observational time point at 1, 2, 4 and 6 weeks after injury (n = 10 for each group). Before modeling, 9 rats were randomly selected for CatWalk gait analysis, which contained step cycle, single stance time and average speed. Data were recorded as the normal controls. After then, ATI models were established in the left hind limbs of the all 40 rats (ATI group), while the right hind limbs were only cut and sutured without injury of the Achilles tendon (sham operation group). At 1, 2, 4 and 6 weeks after injury, the gait behavior of the corresponding group of rats (n = 9) as observed and recorded by CatWalk platform. After then, the rats were sacrificed and Achilles tendon of both limbs was harvested. The tendon healing was observed by gross anatomy and histological examination, and the protein and mRNA expression of TGF-β1, TGF-β3, CREB-1 were observed by immunohistochemistry and qPCR. The results of tendon gross grading were analyzed by Wilcoxon rank sum test, and other data were analyzed by one-way analysis of variance among multiple groups.

RESULTS

Compared with normal controls, all gait indexes (step cycle, single stance time and average speed) were greatly affected following ATI, which however improved with time. The step cycle was significantly lower at 1, 2 and 4 weeks after ATI (compared with normal controls, all p < 0.05), but almost returned to the normal level at 6 weeks ((0.694 ± 0.102) vs. (0.503 ± 0.094) s, p > 0.05). The single stance time of the ATI group was significantly shorter at 1 and 2 weeks after operation ((0.078 ± 0.010) s at 1 week, (0.078 ± 0.020) s at 2 weeks, all p < 0.001) and revealed no significant difference at 4 weeks (p = 0.120). The average speed of ATI group at 1, 2, 4, 6 weeks was significantly lower than that in the normal control group (all p < 0.001). Gross observation showed that the grade of local scar adhesion in ATI group increased significantly at 2, 4 and 6 weeks, compared with the sham operation group (all p < 0.001). Extensive adhesion was formed at 6 weeks after ATI. The results of HE staining showed that the number of fibroblast increased gradually and arranged more orderly in ATI group at 1, 2 and 4 weeks (all p < 0.001), and decreased at 6 weeks, but it was still significantly higher than that of the sham operation group (p < 0.001). Immunohistochemistry showed that the positive expression of TGF-β1, TGF-β3, CREB-1 in ATI group was higher than that in the sham operation group at 4 time points (all p < 0.05), which reached the peak at 2 weeks after operation and decreased at 4 weeks (p = 0.002, p < 0.001, p = 0.041, respectively). The results of qPCR suggested that the mRNA expression of TGF-β1, TGF-β3, CREB-1 in ATI group was higher than that in the sham operation group at all-time points (all p < 0.05), which reached the peak at 2 weeks after operation, decreased at 4 weeks, and significantly decreased at 6 weeks (all p < 0.001).

CONCLUSION

Gait behavior indexes are associated with Achilles tendon healing. The study gives an insight of TGF-β1, TGF-β3, CREB-1 changes in the coursing of Achilles tendon healing and these cytokines may be able to be used to regulate the Achilles tendon healing.

MOFs-Based Nitric Oxide Therapy for Tendon Regeneration

Tendon regeneration is still a great challenge due to its avascular structure and low self-renewal capability. The nitric oxide (NO) therapy emerges as a promising treatment for inducing the regeneration of injured tendon by angiogenesis. Here, in this study, a system that NO-loaded metal-organic frameworks (MOFs) encapsulated in polycaprolactone (PCL)/gelatin (Gel) aligned coaxial scaffolds (NMPGA) is designed and prepared for tendon repair. In this system, NO is able to be released in vitro at a slow and stable average speed of 1.67 nM h^-1 as long as 15 d without a burst release stage in the initial 48 h. Furthermore, NMPGA can not only improve the tubular formation capability of endothelial cells in vitro but also obviously increase the blood perfusion near the injured tendon in vivo, leading to accelerating the maturity of collagen and recovery of biomechanical strength of the regenerated tendon tissue. As a NO-loaded MOFs therapeutic system, NMPGA can promote tendon regeneration in a shorter healing period with better biomechanical properties in comparison with control group by angiogenesis. Therefore, this study not only provides a promising scaffold for tendon regeneration, but also paves a new way to develop a NO-based therapy for biomedical application in the future.